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35080B kVp Divider Operators Manual

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1. 50 kV 90 kV 40 kV ZERO at A0 80kV CAL at 80 Sensitivity 10 kV div Sensitivity 10 kV div Scope setting 0 1 V div Scope setting 0 1 V div Operation 2 Oscilloscope Zero and Offsets Figure 2 1A and 1B Suggested Oscilloscope Settings for Use with the Wide Range Filter Pack 37617 As an alternative to reading directly in kV the output of the Model 35080B kVp Divider may be read directly in volts The formula below is used to calculate the kV kV Model 35080B voltage x 100 ZERO kV Example A peak voltage of 0 300 volts is read The ZERO kV of the Wide Range Filter Pack 37617 is 40 kV Therefore kV 0 300 x 100 40 30 40 70kV 2 5 Geometry of Setup The filter pack is aligned on the beam center with the long axis of the Model 35080B kVp Divider perpendicular to the x ray tube axis and the beam normal to the tabletop see Figure 2 2 The x ray beam must be large enough to cover the active area of the filter pack Distance is not critical but a 22 inch distance from focal spot to kVp divider is suggested The kVp divider must be inverted for under table x ray head evaluation refer to Figure 2 3 Again the filter pack should be on beam center perpendicular to the axis of the x ray tube and the beam normal to the table The beam area must be large enough to cover the active area of the filter pack In positioning the kVp divider the long axis of the instrument should be perpendicular to the x ray tube axis
2. 38237 is similar to the operation of the Wide Range Filter Pack 37617 described in Section 2 Prior to taking measurements it is suggested that the battery and internal calibration be checked as described in Section 2 1 and 2 2 OSCILLOSCOPE SETUP Two possible methods for reading the output of the Model 35080B kVp Divider on a storage oscilloscope are to read the kVp divider output voltage and then convert the voltage into the equivalent kV using the conversion formula or to set up the oscilloscope to allow direct readout of kV Both methods are described and assume that the operator is familiar with the use of his storage oscilloscope Converting voltage reading into kV The following formula is used to convert a voltage reading obtained from the Model 35080B kVp Divider into the equivalent kV kV kVp Divider Voltage x 100 ZERO kV Example The peak voltage located on the waveform captured by the storage oscilloscope is 0 280 volts The ZERO kV of the Low Range Filter Pack 38237 is 26 kV This reading represents a kVp of kV 0 280 x 100 26 kV 28 26 kV 54 kV Setup for direct kV readout 1 Insert the Low Range Filter Pack 38237 into the Model 35080B kVp Divider and connect the kVp divider output to the oscilloscope input using a BNC to BNC coaxial cable 2 Set the oscilloscope gain to 0 1 V div DC Coupled This corresponds to a 10 kV div sensitivity 3 Setthe FUNCTION switch of the kVp divider to the CAL positio
3. Divider s calibration The CAL position on the kVp divider provides a check of the electronics only The Test Filter Pack 32863 verifies the calibration of the kVp divider from radiation input through to the output signal under actual operating conditions 4 2 SPECIFICATIONS Output 3 00 V 1 Cal 0 750 V 1 X ray Generator kV Setting 100 kV is recommended X ray Generator mA Setting 200 mA at 22 inches focal spot to kVp divider is recommended 4 3 Theory of Operation Section 3 describes the theory of operation of the Model 35080B kVp divider With the Test Filter Pack 32863 installed the output voltage of the kVp divider is equal to three times the x ray intensity striking the heavily filtered detector divided by the x ray intensity striking the lightly filtered detector The Test Filter Pack 32863 has equal thickness of copper filters for both detectors When this filter pack is inserted into the kVp Divider the ratio seen by the instrument for adequately high intensities is 1 0 The Model 35080B kVp Divider is factory calibrated to produce 3 0 volts for a ratio of 1 0 In theory the 3 volt value is not a function of tube current distance or kV in order to have a standardized test however the 3 volt check should be run at 22 inches focal spot to kVp divider at 200 mA and 100 kVp Typical waveforms from single phase and three phase exposures using the Test Filter Pack 32863 are shown in Figure 4 1 35080B Operators
4. is due to variations in tube filtration and part is due to positional dependence Therefore when using the Linear Mammo Filter Pack 37351 if the Model 35080B kVp Divider is moved a new measurement at the K edge comparison kVp point must be made with the Linear Mammo Filter Pack 37351 and a new correction factor computed 6 4 Corrections If the amount of molybdenum filtration were known the correction could be made with the correction curves in Figures 6 1 and 6 2 Figure 6 1 shows the correction required for total molybdenum filtration of 12 microns 24 microns and 35 microns no correction is required for 24 microns Figure 6 2 shows the effect of adding 0 25 mm Al to the 24 microns of molybdenum Linear Mammo Filter Pack 37351 Correction for Molybdenum Filtration LTT 24 microns Figure 6 1 Correction Curves for 12 24 and 35 Microns Molybdenum Filtrations E oe 5 UO D O U gt x A machine with 35 microns of molybdenum and a reading of 29 0 add 1 0 kV the corrected reading is 30 0 kVp Refer to Figure 6 1 For 12 microns and a reading of 28 0 kVp subtract 1 5 kV for a corrected reading of 26 5 kV 6 2 Linear Mammo Filter Pack Option 37351 6 Corrections Linear Mammo Filter Pack 37351 Correction for Aluminum Filtration 2 2 ME A 24 microns molybdenum E o 5 U D O U gt a 28 5 Indicated kVp Figure 7 2 The correction curve that shows the effect of adding 0 25mm
5. is subtracted from the standard calibration filtration 2 5 mm Al and the resulting number is multiplied by the filtration effect 2 5 5 0 x 0 5 1 25 kV The resulting number 1 25 kV is the correction which is added to the apparent reading Therefore the actual reading is 90 kV 1 25 kV 88 75 kV Filtration Effect kV Per mm AL g Na JIN Es E o o z NGT INTE ING TT Model 35080B Reading kVp Figure 2 4 The Wide Range Filter Pack 37617 Filtration Effect Correction Curve Operation 2 Linearity Corrections 2 7 Linearity Corrections Corrections for linearity in using the Wide Range Filter Pack 37617 are made by taking the apparent output of the Model 35080B and adding or subtracting the value in kV shown on the following curve For the greatest accuracy possible readings should first be corrected for filtration before linearity corrections are made For most applications however linearity corrections alone may be adequate especially if the difference in total filtration from the calibration standard of 2 5 mm Al is small See Section 2 6 for information about filtration correction Wide Range Filter Pack 37617 Linearity Correction Curve pt tt tt Et tt Pip y AHHH HA S NE kVp Correction Model 35080B Reading kVp Figure2 5 The Wide Range Filter Pack 37617 Linearity Correction Curve The kVp Correction Value read from the vertical scale should be added to the Mod
6. 1 10 2 Appendix A A 1 A 2 A 3 Linear Mammo Filter Pack Option 37351 J nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 6 1 a o a Ren 6 1 ee e ER 6 1 Rate Ee EE 6 1 Ree dee EE 6 2 DBeraling Inssiucli ns E 6 3 CT Filter Pack Option 33551 iii nica diia 7 1 dee edel DEEN 7 1 Specifications a a A E AAFO a A A e 7 1 Theory of Operas aja 7 2 Operating Re gen EE 7 2 Correction OF E le a Le EE 7 3 Mobile Filter Pack Plus Option 37946 ccccccccccccccccoconecononencnennnnnanas 8 1 A EE EEE 8 1 Species hass 8 1 Filtration ENecrCOFSCIONS mem 8 2 Linearity Correcti NS e aussah ee EE EE 8 3 Low Range Filter Pack Option 38237 nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 9 1 ee e le de ae 9 1 DSC IM TSAR 9 1 Theory eet 9 1 Operating INSTUCUON Susa da 9 2 Filtration Effect Correction BEE 9 3 A ea er Geeer 9 3 MAINTENANCO ia 10 1 Cleaning the E d 10 1 Ree e e e 10 1 Battery Replacement cai ees ora cos oq vs orn ri prides ia oi pea or 10 2 SR 10 3 Replaceable Parts Iotommaton AAA 10 6 Recalibration amp Repair Information Technical Aesisiance 10 7 NS EES 10 7 Mammographic Measurements with the Model 35080B A 1 ee lu 010 E ET A 1 K edge Measures ld A 1 Linear Measurement AAA A 2 Appendix B Appendix C C 1 C 2 Correcting kVp Measurements for Gain Effects sssssnnnnnnnnnnnnnnvnnnnnnner B 1 a ONT ee ee ee Ee B 1 Oscilloscope Measurements u nung rien B 1 Voltmeter
7. Al 0 01in Al to the 24 microns molybdenum filter The aluminum makes the Linear Mammo Filter Pack 37351 read high To make corrections subtract the kV correction from the indicated reading In most cases amount of molybdenum filtration is unknown and the use of the Cadmium K edge Mammo Filter Pack 37355 for precise calibration of the generator at a kVp between 27 5 and 29 5 kV is required NOTE See Appendix A for more detailed instructions on the use of the K edge and Linear Mammo Filter Packs 37355 and 37351 respectively 6 5 Operating Instructions This procedure will normally follow that given in Section 5 4 where measurement with the Cadmium K edge Mammo Filter Pack 37355 ended 1 Measurement Setup Replace the Cadmium K edge Mammo Filter Pack 37355 with the Linear Mammo Filter Pack 37351 Reposition the Model 35080B kVp Divider to approximately 15 inches from the focal spot by lowering the compression paddle or other support device See Figure 6 3 35080B Operators Manual Model 35080B kVp Divider Figure 6 3 Linear Measurement Setup Connect the kVp Divider output to either a storage oscilloscope or a peak read and hold DMM Set the oscilloscope to 0 05 volts division vertical gain and the input to DC Coupled single trace storage mode NOTE The Linear Mammo Filter Pack 37351 may be used with a peak read and hold DMM for the readout instead of or along side of the storage oscilloscope The devi
8. Effects B 1 Introduction NOTE Section 10 4 Calibration of the Model 35080B kVp Divider users manual details a method for performing gain corrections by adjusting the internal potentiometers of the instrument This remains a completely acceptable technique The purpose of this addendum is to provide an alternative method for users with sealed units who cannot access the adjustment potentiometers The calibration mode feature of the Model 35080B kVp Divider provides a method to monitor the gain of the internal circuitry When the kVp divider is placed in CAL mode the specific voltage and kVp stated on each individual filter pack should be obtained If the output voltage in CAL mode is not within 1 of the value stated on the pack kVp measurements should be corrected in one of the following ways depending on the device used for measuring the output of the kVp divider A deviation of less than 1 will result in a maximum kVp error of 0 75 of reading B 2 Oscilloscope Measurements The Model 35080B kVp Divider Instruction Manual describes the technique that should be used to measure kVp when connected to an oscilloscope refer to Section 2 4 A slight modification of this technique will allow for the correction of gain effects Briefly this technique is as follows 1 Insert the filter pack to be used into the kVp divider and connect to the oscilloscope Set the oscilloscope gain to an appropriate value depending on the sensitivity
9. Linearity Correction Corrections for the linearity of the Low Range Filter Pack 38237 can be made by taking the measured output of the Model 35080B kVp Divider and adding the value in kVp shown on the curve in Figure 9 2 For best accuracy a filtration correction should be made prior to the linearity correction If the difference in total filtration from the calibration standard of 2 5 mm Al is small however linearity corrections alone may be sufficient Example The Model 35080B kVp Divider with a Low Range Filter Pack 38237 has a reading of 45 kVp From the chart a kVp Correction value of 0 2 kVp is obtained Assuming filtration corrections are not required for this x ray system the actual kVp is 45 0 2 44 8 kVp 9 3 35080B Operators Manual Low Range Filter Pack 38237 Linearity Correction Curve kVp Correction Model 35080B kVp Reading Figure 9 2 Low Range Filter Pack 38237 Linearity Correction Curve The kVp Correction Value read from the vertical scale should be added to the Model 35080B Model 35080B kVp Divider reading to obtain the corrected kVp result Maintenance 1 0 Cleaning the Instrument Section 10 Maintenance 10 1 Cleaning the Instrument To clean the exterior of the instrument follow these steps Turn off the instrument and disconnect the output connector 2 Moisten a soft cleaning cloth with a solution of three parts water and one part liquid dishwashing deterge
10. Operation Since the filter pack primarily consists of metal sheets the absorption is not expected to change with time There are only two calibration adjustments in the kVp divider One adjustment RP103 sets the gain of the ratio circuit The other adjustment RP101 sets the ratio of the internal reference currents that are used as an internal calibration check when the function switch is set to the CAL mode INTERNAL CALIBRATION CHECK 1 Set the function switch to the CAL position 2 Insert the Test Pack 32863 3 The output voltage should read 0 750 volts 1 10 3 35080B Operators Manual NOTE Each 1 deviation of this value will result in no more than a 0 75 of reading error This measurement must be made with a 0 1 DVM EXTERNAL CALIBRATION CHECK Place the Model 35080B kVp Divider in the RUN mode Insert the Test Pack 32863 Place the kVp divider in the x ray beam aligned as described in Section 4 5 Geometry of Setup Make the focal spot to kVp divider distance 22 inches With a 100 kV 200 mA exposure the output should be 3 volts 1 NOTE Most oscilloscopes are not accurate enough 0 1 to make this measurement Each 1 of miss adjustment will cause a maximum of 0 75 of reading error CALIBRATION ADJUSTMENT 10 4 NOTE Only facilities with precision calibration equipment should adjust the calibration of the Model 35080B kVp Divider Insert the Test Pack 32863 Pl
11. This filter pack uses the inherent stability of the Cadmium K edge as an absolute reference for precision measurements between 27 5 and 29 5 kVp for beryllium window molybdenum anode mammographic generators with molybdenum filtration When used in conjunction with the Linear Mammo Filter Pack 37351 precision calibrations of 1 0 kV accuracy can be performed from 22 to 40 kV Cadmium K edge Mammo Filter Pack 37355 Response Curve 24 microns Mo Filter OU D oO O gt 2 Sei Q fe 5 O Figure 5 1 Response Curve for the Cadmium K edge Mammo Filter Pack 37355 5 1 35080B Operators Manual 5 2 Specifications Intended Use Beryllium window molybdenum anode mammographic generators Range 27 5 kVp to 29 5 kVp Accuracy 0 5 kV Sensitivity 0 1 volt per kV Zero 27 0 kV Cal 0 75 V Minimum Anode Current 50 mA Target to kVp Divider Distance 12 in 30 5 cm Effect of Molybdenum Filtration Negligible 12 to 35 microns 5 3 Theory of Operation The Cadmium K edge Mammo Filter Pack 37355 contains two different filters side by side One is constructed of cadmium an element whose x ray attenuation increases in a step fashion at its K edge 26 7 kV The other filter is made of an element like aluminum that has no K edge in the mammographic region These two filters are selected to have identical attenuation characteristics for photon energies less than 26 7 kV The Model 35080B kVp Divider take
12. minimum level 2 2 Internal Calibration Check Connect the output of the Model 35080B kVp Divider to a DVM with 0 1 accuracy Remove any filter pack that may be inserted in the kVp Divider Turn the function switch to the CAL position After a short delay a voltage of 0 750 1 will appear This reading verifies the stability of the kVp Divider ratio electronics A 1 error in the kVp Divider gain will cause a maximum kV reading error of 0 75 of reading Refer to Section 10 4 for detailed information on calibration 2 3 Filter Pack Selection One Wide Range Filter Pack 37617 is provided as standard for the Model 35080B kVp Divider See Sections 4 through 9 of this manual for use of optional filter packs available from Fluke Biomedical Radiation Management Services 2 4 Oscilloscope Zero and Offsets NOTE It is assumed that the operator is familiar with the use of a storage oscilloscope The following examples are for oscilloscopes with 8 major divisions for vertical scales and sensitivity selections of 0 1 V div and 0 2 V div The selection of time scales or triggering are not discussed in this manual 35080B Operators Manual Figures 2 1A amp 2B show suggested oscilloscope settings for the 50 150 kV range using the Wide Range Filter Pack 37617 1 Insert the Wide Range Filter Pack 37617 into the Model 35080B kVp Divider and connect the kVp divider to the oscilloscope 2 Set the oscilloscope
13. voltage in the LINEAR VOLTAGE column on the data sheet multiply by 100 3 Enter the value in the LINEAR kVp column 4 Apply the CORRECTION VALUE to all kVp s by either adding to or subtracting from the LINEAR kVp column and record the results in the CORRECTED kVp column This column now has the true kVp value for all kVp s measured Part D If the position of the Model 35080B kVp Divider changes during the Linear kVp measurement you must repeat the measurement starting with Part C some of the correction value is positional dependent Set K edge True Linear Linear Correction Corrected kVp Voltage kVp Voltage kVp Value kVp 22 e EE 0 213 21 3 0 8 22 1 23 0 221 22 1 0 8 22 9 24 0 230 23 0 0 8 23 8 25 0 237 23 7 0 8 24 5 26 EE 0 249 24 9 0 8 25 7 27 0 255 25 5 0 8 26 3 28 0 267 26 7 0 8 27 5 29 0 8 28 6 30 0 8 29 5 31 0 8 30 7 32 0 8 31 6 33 0 8 32 7 34 0 8 33 8 35 0 8 35 0 36 0 8 35 9 35080B Operators Manual Ltt Figure A 1 The Model 35080B Mammographic Worksheet Example Set True Linear Voltage Linear kVp Correction Value Corrected kVp Appendix B Correcting kVp Measurements For Gain Effects Section B Correcting kVp Measurements For Gain
14. 080B Operators Manual K EDGE MEASUREMENT PROCEDURE Part A 1 Set the x ray generator for 25 kVp 100 mA or a mAs setting that provides the maximum tube current at least 50 mA 2 Select the Mo molybdenum filter 3 Make an exposure adjusting the scope trigger level as necessary to get a stable trace 4 Measure the peak voltage and record in box A on the accompanying data sheet Figure A 2 Part B 1 Set the generator for 26 kVp and make an exposure 2 Record this voltage value in box B on the data sheet Figure A 2 The voltage values A and B should be equal to within 0 020V if so this will be your BASE VOLTAGE if not then repeat the above steps at one kVp lower Part C 1 Set the generator for 29 kVp and make an exposure 2 Measure the peak voltage If this voltage is greater than the BASE VOLTAGE by 0 1V but not greater than 0 25 V above the BASE VOLTAGE record in box C Figure A 2 If the voltage is greater than 0 25 volts above the BASE VOLTAGE repeat this step at one kVp lower If the voltage is not greater than the BASE VOLTAGE by 0 1 volts repeat this step at one kVp higher Part D Repeat the last measurement to verify that the generator is repeatable The voltage reading should repeat to within 0 020 V If the reading is not repeatable the generator needs service Part E 1 Subtract the BASELINE voltage from the voltage measured in Part C step 2 box 2 Multiply this voltage by 10 ad
15. 1 2 24 9 34 6 29 0 38 0 33 1 31 3 25 1 34 7 29 1 38 1 33 2 31 4 25 2 34 8 29 3 38 2 33 3 31 5 25 3 34 9 29 4 38 3 33 5 31 6 25 4 35 0 29 5 38 4 33 6 31 7 25 5 35 1 29 6 38 5 33 7 31 8 25 7 35 2 29 7 38 6 33 8 31 9 25 8 35 3 29 9 38 7 33 9 32 0 25 9 35 4 30 0 38 8 34 1 32 1 26 0 35 5 30 1 38 9 34 2 32 2 26 1 35 6 30 2 39 0 34 3 32 3 26 3 35 7 30 3 39 1 34 4 32 4 26 4 35 8 30 5 39 2 34 5 32 5 26 5 35 9 30 6 39 3 34 7 32 6 26 6 36 0 30 7 39 4 34 8 32 7 26 7 36 1 30 8 39 5 34 9 32 8 26 9 36 2 30 9 39 6 35 0 32 9 27 0 36 3 31 1 39 7 35 1 33 0 27 1 36 4 31 2 39 8 35 3 33 1 27 2 36 5 31 3 39 9 35 4 33 2 27 3 36 6 31 4 40 0 35 5 33 3 27 5 36 7 31 5 40 1 35 6 33 4 27 6 36 8 31 7 40 2 35 7 33 5 27 7 36 9 31 8 40 3 35 9 33 6 27 8 37 0 31 9 40 4 36 0 33 7 27 9 37 1 32 0 33 8 28 1 37 2 32 1 C 3 35080B Operators Manual 4 For all subsequent measurements at other generator settings use the following procedure First obtain a reading using the Linear Mammo Filter Pack 37351 Next determine the actual kVp using the look up table at the end of this application note Finally add the k edge correction value calculated in step 3 to this value This procedure will allow kVp measurements over the range of about 25 to 35 kVp The example at the end of this addendum show a sample measurement session with all of the appropriate correctio
16. 351 The K edge measurement should be performed each time a generator is tested Part of the correction factor for the Linear Mammo Filter Pack 37351 is due to variations in tube filtration and part is due to positional dependence Therefore if the Model 35080B non invasive kVp Divider is moved when using the Linear Mammo Filter Pack 37351 a new measurement at the K edge comparison kVp point must be made with the Linear Mammo Filter Pack 37351 to compute a new correction factor The following procedure enables the first time user to achieve good results An experienced user can take many short cuts The kVp divider with the mammo kVp option is for use on molybdenum anode beryllium window tubes only A 2 K Edge Measurement MEASUREMENT SETUP 1 Remove the cone 2 Remove the compression paddle turn it upside down and reinstall as shown in Figure 5 3 3 Place the Model 35080B kVp Divider with a K edge Mammo Filter Pack 37355 on top of the compression paddle as close as possible to the x ray tube 4 Level the kVp divider OSCILLOSCOPE SETUP 1 Connect the Model 35080B kVp Divider to the scope using a shielded cable 2 Set the vertical sensitivity to 0 5 volts per division 3 With the input in the GROUND position adjust the vertical position control to place the trace on the bottom graticule line 4 Set the scope in single trace storage mode 5 Place the input selector switch in the DC position 35
17. 5080B Operators Manual 7 3 Theory of Operation The Model 35080B kVp Divider contains a pair of solid state detectors which when exposed to x rays send signals to a ratio module The resulting ratio depends on the kV of the CT beam and the difference in thickness of filters placed between the detectors and the beam source The filters are carefully selected to give the best response curve possible over the kV range of CT interest see Specifications The narrow dimensions of the CT Filter Pack s 33551 detector area are suited to the beam area restrictions of CT applications 7 4 Operating Instructions 1 Select 2 5 mm Al filtration and remove beam restricting devices from the CT beam path on the CT machine Open the beam width to 10 mm to cover the sensor area on the CT Filter Pack 33551 Use the patient positioning laser to align the Model 35080B kVp Divider within the beam Connect the kVp Divider output to a storage oscilloscope Set the oscilloscope sensitivity to 0 1 V div DC Coupled Put the kVp Divider into the CAL mode and verify its output is 0 644 volt 1 Turn the kVp Divider OFF and position the oscilloscope trace to read 60 kV the reference baseline on the oscilloscope which is added to the measured value 6 Again put the kVp Divider into the CAL mode and verify that the oscilloscope trace corresponds to 124 4 kV 1 kV 7 Place the tube head in its top position 8 Switch the kVp Divider int
18. February 2005 Manual No 37648 Rev 7 2004 2005 Fluke Corporation All rights reserved Printed in U S A All product names are trademarks of their respective companies FS iOmedical 35080B kVp Divider Operators Manual Fluke Biomedical Radiation Management Services 6045 Cochran Road Cleveland Ohio 44139 440 498 2564 120 Andrews Road Hicksville New York 11801 516 870 0100 www flukebiomedical com rms Section 1 1 1 1 2 1 3 1 4 Section 2 Table of Contents General Information sssnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnvnnnnnner 1 1 lee Te dein NEE 1 1 Manual Add aia aaa 1 1 Safety Symbol and TEMSaa ae 1 1 Specifications EN 1 2 Operi og RRA 2 1 Battery Check va 2 1 Internal Calibration Check aaa 2 1 Filter Pack Selection SE 2 1 Oscilloscope Zero and Ofteets AAA 2 1 Geometry OF EE 2 3 Filtration Effect e Let EN 2 4 O 2 5 Theory of Operation csi 3 1 INIFOAUCHON an dera 3 1 Measurement TNEON arrasar ee EES 3 1 Wide Range Filter Pack OG 617 nennen nnnnnnnnennnnneneeenn 3 1 Mva 3 3 ME Snap 3 3 Internal Cali 3 3 Test Filter Pack Option 20863 seen 4 1 A iE 4 1 28121811E e Ee 4 1 Theory f Operator nun 4 1 Operating INSWUCHONS Lee eee ee 4 2 Cadmium K Edge Mammo Filter Pack Option 37355 uuuuu0 5 1 Jee Te aa RA 5 1 Sp ificationS AE 5 2 Theory of Operation Pee 5 2 Operatiq Ra de ee E 5 3 Section 6 Section 10 10
19. Manual 4 4 Operating Instructions The operation of the Test Filter Pack 32863 is similar to the operation of the Wide Range Filter Pack 37617 described in Section 2 Prior to taking measurements it is suggested that the battery and internal calibration be checked as described in Sections 2 1 and 2 2 Position the kVp Divider as described in Section 2 5 Geometry of Setup Set up the oscilloscope to read the 3 0 volts expected from the Model 35080B kVp divider using the Test Filter Pack 32863 and make an exposure On a properly functioning unit the observed waveform amplitude will be 3 00 Volts 1 Be aware that the oscilloscope accuracy may not be adequate for this test The calibration of the kVp Divider can only be verified to within the accuracy of the oscilloscope or other readout device used If the unit appears to be out of calibration refer to Section 10 4 Calibration kV WaveForm Model 35080B WaveForm Single Phase Output Single Phase wo I m kV WaveForm Model 35080B WaveForm Three Phase Output Three Phase 100 KV 3V ay Figure 4 1 The Model 35080B kVp Divider Single phase and Three phase Output with the Test Filter Pack 32863 4 2 Cadmium K edge Mammo Filter Pack Option 37355 Introduction 5 Section 5 Cadmium K edge Mammo Filter Pack Option 37355 5 1 Introduction The Cadmium K edge Mammo Filter Pack 37355 provides a non invasive way to make kVp measurements of mammographic x ray generators
20. Measurements nen B 2 The Model 35050A Dosimeter Meaeuremente nennen B 2 Procedure for Making kVp Measurements on Rhodium Anode Rhodium Filtration Selection of GE DMR Mammography X Ray EE C 1 TO C 1 POCO it AAA ai C 1 iii Blank page General Information 1 Introduction Section 1 General Information 1 1 Introduction The Model 35080B kVp Divider is an alternative to high voltage divider tanks It provides a safe non invasive fast measurement of kVp without endangering personnel and or equipment Its use is primarily intended for x ray machine service and calibration High speed precision logarithmic circuitry allows for wide variations in mA and distance without a sacrifice of accuracy or response speed The Model 35080B kVp Divider provides an analog output voltage proportional to the instantaneous voltage applied to the x ray tube When the kVp divider is connected to a storage oscilloscope the kV waveform may be viewed directly If a digital display of the kVp value is desired then the Model 35080B kVp Divider may be connected to the Model 35050A Dosimeter kVp Readout One Wide Range Filter Pack 37617 allows high accuracy measurements from 50 to 150kV The kVp divider is placed on the x ray table with the filter pack in place A storage oscilloscope is connected to the kVp divider The x ray beam is collimated to the area of the filter pack An exposure is made and the kV waveform is displayed on the storage oscilloscop
21. Operating Instructions of this instruction manual ARAY BEAN HEAVY EH LIGHT FILTER FILTERS DETECTORS Figure 3 1 Simplified Functional Block Diagram of the Model 35080B kVp Divider 3 1 35080B Operators Manual 0 9 0 8 0 7 0 6 0 5 0 4 Model 35080B Output in Volts 0 3 0 2 0 1 kV Figure 3 2 Output Ratio Plotted as a Function of kV Voltage WaveForm Model 35080B Single Phase WaveForm Single Phase NVN Lounen Voltage WaveForm Model 35080BWaveForm Three Phase Output Three Phase fF E Figure 3 3 Output of the Model 35080B kVp Divider Compared to Voltage Applied to X ray Tube 3 2 Theory of Operation 3 Output 3 4 Output In the Model 35080B kVp Divider the intensity ratio is taken with a high speed logarithmic ratio module Thus the output of the Model 35080B kVp Divider follows the kVp waveform applied to the x ray tube within the linear range of the filter pack The waveform differs from the waveform output of a resistive divider in that information below the kV baseline of the filter is not displayed see Figure 3 3 3 5 Intensity Cutoff An examination of the Model 35080B kVp Divider waveforms in Figure 3 3 shows that as the potential of the x ray beam waveform increases for the first time the Model 35080B kVp Divider follows the signal as soon as it comes into the linear range of the filter pack However as the x ray signal deca
22. T Filter Pack Optional Mobile Filter Pack Plus Optional Low Range Filter Pack Optional Carrying Case Battery Cover Rubber Feet 10 6 Maintenance 1 0 Cleaning the Instrument 10 6 Recalibration amp Repair Information technical assistance If your instrument needs recalibration or repair we request that you contact Fluke Biomedical at 440 498 2564 or by Fax at 440 542 3682 More information concerning the operation application or service of your instrument may be obtained from the applications engineer at the previously listed numbers 10 7 Warranty Information Should your instrument require warranty service contact Fluke Biomedical at 440 498 2564 or by Fax at 440 542 3682 NOTE This warranty does not cover battery replacement or damage caused by battery leakage 10 7 35080B Operators Manual Blank page Appendix A Mammographic Measurements With The Model 35080B Section A Mammographic Measurements With The Model 35080B A 1 Introduction We recommend that the two mammographic filter packs K edge Mammo Filter Pack 37355 and Linear Mammo Filter Pack 37351 be used together The K edge Mammo Filter Pack 37355 is used first to find a point between 27 5 kV and 29 5 kV very accurately Then the Linear Mammo Filter Pack 37351 measurement is made at the same point to determine the necessary correction to apply to all readings taken with the Linear Mammo Filter Pack 37
23. Use Beryllium window molybdenum anode mammographic generators Range 22 0 kVp to 40 0 kVp Accuracy 1 0 kV exclusive of filtration effects Sensitivity 0 01 volt per kV Cal 0 200 V 20 0 kV Minimum Anode Current 50 mA Target to kVp Divider Distance 12 in to 24 in 30 5 to 61 cm 6 3 Theory of Operation The Linear Mammo Filter Pack 37351 is similar in construction to the Wide Range linear diagnostic filter pack except that the filter elements are much thinner As expected in mammography measurements are more sensitive to variations in added filtration than in the diagnostic range Thus the Linear Mammo Filter Pack 37351 is normally used in conjunction with the K edge Mammo Filter Pack 37355 The K edge Mammo Filter Pack 37355 is used first to find a point between 27 5 kV and 29 5 kV very accurately Then the Linear Mammo Filter Pack 37351 measurement is made at the same point to determine the necessary correction to apply to the Linear Mammo Filter Pack 37351 readings 35080B Operators Manual The reading from the Linear Mammo Filter Pack 37351 is compared to that taken with the Cadmium K edge Mammo Filter Pack 37355 and a kV correction value for the Linear Mammo Filter Pack 37351 is computed This correction value is applied uniformly to all readings taken with the Linear The K edge measurement should be performed each time a generator is tested Part of the correction factor for the Linear Mammo Filter Pack 37351
24. a calibration check Permitted Tube Current Range 1 mA to 3000 mA dependent on waveform and distance Response Time 150 microseconds 10 90 Environment Operating temperature 15 to 35 C storage temperature 35 to 50 C relative humidity to 90 Orientation The long axis of the Model 35080B kVp Divider is oriented perpendicular to the axis of the x ray tube to eliminate heel effect Table 1 1 Permitted Tube Current Settings less than 1 kV effect Single Phase Single Phase Half Wave Full Wave Three Phase Minimum Tube Current 12 Focal Spot to kVp divider 1 mA 2 mA 4 mA Maximum Tube Current 22 Focal Spot to kVp divider 750 mA 1500 mA 3000 mA Factory calibration performed at 200 mA 2 5 mm Al inherent filtration 22 inches focal spot to kVp divider Six point calibration check Batteries One Eveready 9V alkaline type 522 life approximately 60 hours BATTERY CHECK function connects battery to output connector for voltage measurement Dimensions and Weight 60 mm high x 210 mm wide x 90 mm deep 2 3 8 in x 8 1 4 in x 3 1 2 in net weight 0 68 kg 1 1 2 Ib Standard Filter Pack One Wide Range Filter Pack 37617 is provided for measurement from 50 to 150 kVp General Information 1 Specifications Table 1 2 The Wide Range Filter Pack 37617 Specifications Range 50 to 150 kVp Sensitivity 0 1 V 10 kV Cal 0 400 V Zero 40 kV Cal 80 kV Accuracy 2 exclusive of l
25. ace the Model 35080B kVp Divider on the x ray table such that the distance from the focal spot to the kVp divider is 22 inches and the instrument is normal to the beam with the long axis of the kVp divider perpendicular to the axis of the x ray tube this configuration will avoid heel effect Settings on the generator for kVp should be 100 kV and 200 mA With the kVp divider in the OFF mode zero the oscilloscope Turn the mode switch on the kVp divider to the RUN position Make an x ray exposure greater than 1 mS duration for three phase generating equipment greater than 1 line cycle duration for single phase generating equipment Accurately measure the peak voltage 0 1 Record this value as A If A falls outside of the range 2 970 to 3 030 volts adjust the kVp divider as follows Remove the kVp divider instrument case to access the adjustment potentiometers Place the kVp divider in the CAL mode and measure the output voltage 0 1 accuracy Record this value as B With the kVp divider still in the CAL mode adjust RP102 until the output is V 3 000 x B A volts With the instrument still in CAL adjust RP101 until the output 0 750 volts Place the kVp divider back in its instrument case and turn the function switch to the RUN mode Repeat Step 5 The value should be 3 00 volts 1 If not repeat the sequence Maintenance Calibration 1 0 NOTE If the os
26. ce is direct reading in kVp Merely multiply the display reading by 100 For example a voltage of 0 375 is equivalent to 37 5 kV With the Linear Mammo Filter Pack 37351 installed on the kVp Divider move the switch to the CAL position The voltage output should be 0 200 volts 003 volts 1 1 digit Check CAL voltage with a digital voltmeter or an oscilloscope with at least 0 1 accuracy This value corresponds to a kV reading of 20 0 kV and may be used to setup the oscilloscope The CAL function checks the gain of the kVp Divider A 1 error in gain will result in a 1 error in the kVp reading 0 3 kV at 30 kV With the same generator settings used for K edge measurement at 29 kVp see Section 5 4 turn the kVp Divider to OFF and position the oscilloscope trace on the bottom line Place the kVp Divider in the CAL position and the trace will move to the middle line 20 kV The oscilloscope with eight major vertical positions is now set to indicate a range of 0 to 40 kV Make an exposure and record this value separate from the K edge reading made in Section 5 4 step 6 NOTE The CORRECTION VALUE may be either negative or positive Linear Mammo Filter Pack Option 37351 Operating Instructions 6 5 Measure other kVp values as desired Record the LINEAR VOLTAGE multiply by 100 and this will be your uncorrected LINEAR KVP Lastly add or subtract the CORRECTION VALUE and record the results This now has the true
27. cilloscope in use is not accurate to 0 1 do not attempt adjustment of the Model 35080B kVp Divider OTHER ADJUSTMENTS The third adjustment potentiometer RP103 adjusts the amount of the waveform that is displayed by the oscilloscope If annoying artifacts are observed on the oscilloscope turning the potentiometer RP103 counterclockwise will decrease the width of the waveform displayed on the oscilloscope Turning the same potentiometer clockwise will conversely increase the width of waveform displayed Refer to Figure 10 3 for an illustration of the effects of this adjustment Figure 10 2 Location of RP101 RP102 and RP103 10 5 35080B Operators Manual LEGEND kV Waveform Model 35080B Waveform Output Before Adjustment of RP103 Increased Amount of Leading and Trailing Edge in the Model 35080B Waveform After Adjustment of RP103 Turned Clockwise Figure 10 3 Effects of RP103 Adjustment 10 5 Replaceable Parts Information Fluke Biomedical maintains a complete inventory of all normal replaceable parts See Table 10 1 To place an order or to obtain information concerning replaceable parts contact the Fluke Biomedical at 440 498 2564 or by Fax at 440 542 3682 Table 10 1 Replaceable Parts List Description Part Number Power battery 9 0 V alkaline Wide Range Filter Pack Test Filter Pack Optional Linear Mammo Filter Pack Optional Cadmium K edge Mammo Filter Pack Optional C
28. d to 27 0 and record in box D Figure A 2 This is the true kVp for this station 3 Set the scope for single sweep storage mode and in the DC input mode NOTE PROCEED TO LINEAR MEASUREMENT DO NOT CHANGE THE GENERATOR SETTINGS A 3 Linear Measurement MEASUREMENT SETUP 1 Replace the Cadmium K edge Mammo Filter Pack 37355 with the Linear Mammo Filter Pack 37351 2 Reposition the Model 35080 kVp Divider to approximately 15 inches from the focal spot see Figure 6 3 OSCILLOSCOPE SETUP 1 Set the vertical sensitivity to 0 05 volts per division 2 With the input switch in the GROUND position use the vertical position control to place the trace on the bottom graticule line Appendix Linear Measurement 3 Set scope for single sweep storage mode and in the DC input mode LINEAR MEASUREMENT PROCEDURE Part A 1 With the generator settings used for K edge measurement in Part C make an exposure 2 Record the voltage in box E Figure A 2 then multiply the voltage in box E by 100 and record as kVp in box F Part B 1 Subtract the kVp in box F from the kVp in box D Figure A 2 This will be the CORRECTION VALUE applied to all kVp measurements made with the Linear Mammo Filter Pack 37351C 2 Insert this value in all spaces in the column labeled CORRECTION VALUE NOTE This value may be either positive or negative Part C 1 Measure other kVp values as desired 2 Enter the
29. e At no time are the high voltage supply cables disturbed The Model 35080B kVp Divider is highly portable a contrast to bulky heavy high voltage divider tanks The instrument is accurate to 2 exclusive of linearity and filtration effects The user should note however that as with an invasive divider the accuracy of readings will depend on the accuracy of the oscilloscope or readout device used in the measurements 1 2 Manual Addenda Any improvements or changes concerning the instrument or manual will be explained in an addenda included with the manual Be sure to note these changes and incorporate them into the manual 1 3 Safety Symbol and Terms The following symbol and terms are found on the instrument or used in this manual L mo symbol on the instrument indicates that the user should refer to the operating instructions located in the manual The WARNING heading used in this manual explains dangers that might result in personal injury or death Always read the associated information very carefully before performing the indicated procedure The CAUTION heading used in this manual explains hazards that could damage the instrument Such damage may invalidate the warranty 1 1 35080B Operators Manual 1 4 Specifications Range 50 150 kVp with the Wide Range Filter Pack 37617 Accuracy 2 of reading exclusive of linearity filtration and gain effects Calibration Internally generated signal provides
30. el 35080B kVp Divider reading to produce the corrected KVp result 2 5 35080B Operators Manual Blank page Theory of Operation Introduction Section 3 Theory of Operation 3 1 Introduction When used with the Wide Range Filter Pack 37617 the Model 35080B kVp Divider produces an output voltage that closely follows the voltage applied to the x ray tube It does this with a 10 90 response time of 150 microseconds so the waveform can be used not only for determining kVp but also for making precise time determinations and for diagnosing generator malfunctions 3 2 Measurement Theory In this measurement scheme two x ray detectors are used refer to Figures 3 1 and 3 2 The x ray beam passes through a relatively heavy filter prior to striking detector A and through a lighter filter prior to striking detector B The ratio of the currents 1 1 is transformed to a voltage by a custom designed ratio module Typically this ratio voltage increases as the voltage applied to the x ray tube increases The ratio voltage is virtually independent of the current applied to the x ray tube and the distance to the x ray tube 3 3 Wide Range Filter Pack 37617 The Wide Range Filter Pack 37617 is a standard filter pack supplied with the Model 35080B kVp Divider This filter pack gives linear performance over a wide 50 150 kVp range Detailed characteristics of the filter pack are given in Section 1 General Information and Section 2
31. en reducing the distance from the focal spot to the kVp divider make sure that the x ray beam is wide enough to cover the active area of the filter pack at the distance used 9 2 Low Range Filter Pack Option 38237 Filtration Effect Correction 9 9 5 Filtration Effect Correction The Low Range Filter Pack 38237 is calibrated at 2 5 mm Al total filtration Measurements made at other filtration values require a correction to the measured reading Corrections for filtration are made using the correction curve shown in Figure 9 1 Corrections are made by subtracting the total filtration of the x ray machine being measured from 2 5 mm Al multiplying the result by the value read off the chart for the measured kVp and adding this result to the measured kVp Example A reading of 49 kVp is obtained from a Model 35080B kVp Divider using a Low Range Filter Pack 38237 The x ray system has 3 3 mm Al total filtration The filtration effect curve of Figure 9 1 indicates a filtration effect of 0 5 kVp per mm Al at 49 kVp The difference in filtration 2 5 3 3 0 8 mm Al is multiplied by the correction value to yield 0 8 x 0 5 0 4 kVp This number is then added to the apparent reading to obtain the actual kVp which is 49 kVp 0 4 kVp 48 6 kVp Low Range Filter Pack 38237 Filtration Effect kVp Per mm Al Model 35080B kVp Reading Figure 9 1 Low Range Filter Pack 38237 Filtration Effect Correction Curve 9 6
32. er should not be used when following this procedure When preparing to make measurements with the Linear Mammo Filter Pack 37351 be sure to press the RESET MEASURE button twice until the phrase kVp NOT Corrected appears on the top line of the Model 35050A display All subsequent measurements made with the Linear Mammo Filter Pack 37351 should also have this phrase on the top line of the display If you have an older version of the Model 35050A Dosimeter that does not provide automatic k edge corrections ignore this note 35080B Operators Manual Use the following procedure to measure kVp on the rhodium anode rhodium filtration selection of the DMR 1 Acquire a Cadmium K edge Mammo Filter Pack 37355 measurement using the normal method to determine a value of kVp between 27 5 and 29 5 kVp This value can be used without correction resulting in a maximum error of about 1 kVp For maximum accuracy use the look up table in Table C 1 to obtain a corrected value of kVp For example if the measured value of kVp were 27 8 the actual corrected value would be 28 2 kVp This correction is due to the slight difference in response of the Cadmium K edge Mammo Filter Pack 37355 to the Rh anode Rh filtration spectrum as compared to a Mo anode Mo filtration spectrum Table C 1 Look up table for Cadmium K edge Mammo Filter Pack 37355 measurements made on Rh anode Rh filtration selection of DMR mammography system The equation used
33. erized by erratic spikes superimposed on the kV waveform 3 The x ray machine may be badly adjusted 35080B Operators Manual PROBLEMS WITH THE MODEL 35080B KVP DIVIDER 1 The power battery may be weak or dead Check the battery and replace it if necessary see Section 2 1 Battery Check and Section 10 3 Battery Replacement 2 The function switch on the Model 35080B kVp Divider may be in the wrong position such as CAL Verify that the function switch is in the RUN position 3 Orientation of the kVp divider may not be correct for the location of the x ray source Refer to Section 2 5 Geometry of Setup Turn the kVp divider upside down for under table x ray heads and right side up for above table x ray heads 4 There may be an electronic fault in the kVp divider Check the CAL operation of the kVp divider refer to Section 2 2 Internal Calibration Check 10 3 Battery Replacement The Model 35080B kVp Divider is powered by a single 9 V Eveready type 522 alkaline battery Battery life is approximately 60 hours The battery condition can be checked without opening the instrument case with the function switch in the BAT CHK position a digital voltmeter DVM can be connected to the output connector NOTE Do not leave the function switch in the BAT CHK position as this will decrease battery life If the battery voltage drops below 7 0 V the battery should be replaced as the remaining life of t
34. for the correction is Corrected kVp Uncorrected kVp 27 x 1 5 27 Uncorrected Corrected Uncorrected Corrected kVp kVp kVp kVp 2 Insert the Linear Mammo Filter Pack 87351 into the Model 35080B kVp Divider and acquire a kVp measurement using the same generator settings as used for the k edge measurement in step 1 Use the look up table in Table C 2 to determine the actual kVp of the exposure For example if the measured value were 34 3 kVp the actual kVp would be 28 7 3 Determine the k edge correction value as usual by subtracting the Linear Mammo Filter Pack 37351 reading 28 2 in the example from the measurement obtained with the Cadmium K edge Mammo Filter Pack 37355 in step 1 28 7 in the example Note that the k edge correction value can be positive or negative the value is 28 2 28 7 0 5 kVp in this example Appendix Procedure C Table C 2 Look up table for Linear Mammo Filter Pack 37351 measurements made on Rh anode Rh filtration selection of DMR mammography system The equation used for the correction is Corrected kVp Uncorrected kVp x 1 2 12 5 Uncorrected Corrected Uncorrected Corrected Uncorrected Corrected kVp kVp kVp kVp kVp kVp 30 5 24 1 33 9 28 2 37 3 32 3 30 6 24 2 34 0 28 3 37 4 32 4 30 7 24 3 34 1 28 4 37 5 32 5 30 8 24 5 34 2 28 5 37 6 32 6 30 9 24 6 34 3 28 7 37 7 32 7 31 0 24 7 34 4 28 8 37 8 32 9 31 1 24 8 34 5 28 9 37 9 33 0 3
35. gain to 0 1 V div DC Coupled This setting corresponds to a 10 kV div sensitivity 3 If making KV measurements from 50 to 120 kV set the FUNCTION switch of the kVp divider to the OFF position and adjust the oscilloscope vertical position control so that the oscilloscope trace coincides with the bottom horizontal line on the screen which corresponds to 40 kV Then set the FUNCTION switch of the kVp Divider to the CAL position and verify that after a delay of several seconds the trace on the oscilloscope coincides with middle horizontal line on the screen which corresponds to 80 kV When switching to the RUN position a slight offset may be noted on the oscilloscope Do NOT readjust the oscilloscope trace to compensate for this offset Refer to Figure 2 1A 4 If making kV measurements from 120 to 150 kV set the FUNCTION switch of the kVp divider to the CAL position and adjust the oscilloscope vertical position control so that the oscilloscope trace coincides with the bottom line on the screen which corresponds to 80 kV Refer to Figure 2 1B NOTE If the accuracy of the Model 35080B kVp Divider is in question the output voltage may be checked with a 0 1 DVM The proper CAL voltage is on the filter pack label The allowed tolerance is 1 A 1 error will cause at most a 0 75 error in the kV reading 1A 1B 160 120 kV kV 150 110 kV kV 140 100 kV kV 130 90 kV kV 120 80 kV CAL at 80 kV 110 70kV kV 100 60 kV kV
36. he battery is quite limited If the battery voltage is already below 6 5 volts when checked the battery must be replaced for proper operation of the kVp divider To replace the battery remove the screw from the cover on the bottom of the kVp divider refer to Figure 10 1 Lift the cover from the instrument case Place your hand over the battery compartment and roll the instrument upright letting the battery drop into your hand Carefully disconnect the battery terminal from the used battery and replace it with a fresh 9 V alkaline battery Eveready type 522 Slip the battery back into the compartment and replace the cover Note that the leading edge of the cover must be inserted under the lip of the instrument case before it is properly seated refer to Figure 10 1 Align the hole in the cover with the threaded hole in the case and reinsert the screw 10 2 Maintenance 1 0 Cleaning the Instrument LEADING EDGE OF COVER Figure 10 1 Battery Replacement for the Model 35080B kVp Divider 10 4 Calibration WARNING The factory calibration of the Model 35080B kVp Divider is performed with a precision high voltage divider and a 12 bit 0 1 digital oscilloscope If comparable equipment is not available do NOT attempt to make adjustments on the kVp divider Return the unit to the factory for adjustment Calibration of the Model 35080B kVp Divider depends primarily on the stability of the filter pack Review Section 3 Theory of
37. ilter pack See Figure 5 3 Minimum Model 35080B kVp Divider Figure 5 3 K edge Measurement Setup 5 3 35080B Operators Manual Oscilloscope Setup Connect the kVp Divider to the scope using a shielded cable and set the vertical sensitivity set to 0 5 volts per division With the scope input in the GROUND position adjust the vertical position control to place the trace on the bottom graticule line Next set the scope in single trace storage mode and place the input selector switch in the DC position 25 kVp Measurement Procedure Set the x ray generator for 25 kVp and 100 mA If not available use at least 50 mA and a minimum time of 50 msec or a mAs setting that provides these tube currents Select the Mo molybdenum filter and make an exposure while adjusting the scope trigger level as necessary to get a stable trace After measuring the peak voltage record the value 26 kVp Measurement Procedure Set the generator for 26 kVp and make an exposure Record this value also The two voltage values should be equal to within 0 020 V If so this will be your BASE VOLTAGE if not then repeat steps 3 and 4 at 24 and 25 kVp respectively 29 kVp Measurement Procedure Set the generator for 29 kVp and make an exposure If this voltage is greater than the BASE VOLTAGE by 0 1 V to 0 25 V record this new voltage value If this voltage is greater than the BASE VOLTAGE by higher than 0 25 V repeat this step at one kVp lower
38. inearity and filtration effects Linearity and filtration effects can be corrected using curves from Section 2 of this instruction manual Optional Filter Packs A Test Filter Pack 32863 that provides verification of instrument accuracy a K edge Mammo Filter Pack 37355 and a Linear Mammo Filter Pack 87351 used for precision measurements from 22 to 40 kVp a CT Filter Pack 33551 used for CT system kVp measurements from 70 to 140 kVp a Mobile Filter Pack Plus 37946 used for measurements on x ray systems with kV waveforms above 1 kHz with substantial ripple and a Low Range Filter Pack 38237 used for measurements from 30 kVp to 90 kVp where the kVp range or sensitivity of other filter packs is not adequate Patent numbers 4 843 619 and 4 916 727 1 3 35080B Operators Manual Blank page Operation 2 Battery Check Section 2 Operation NOTE Prior to taking measurements with the Model 35080B kVp Divider it is suggested that the battery and internal calibration be checked 2 1 Battery Check Connect the output of the Model 35080B kVp Divider to a DVM digital voltmeter Place the kVp divider function switch in the BAT CHK position The battery should be replaced if the voltage is less than 7 0 volts as the remaining battery life is quite short The battery must be replaced if the voltage is less than 6 5 volts as the instrument will not function properly when the voltage supply is below this
39. k Plus 37946 is calibrated at 2 5 mm Al total filtration so measurements made at other filtration values require correction of the measured reading Corrections are made by subtracting the total filtration of the x ray machine being measured from 2 5 mm Al multiplying the result by the value read off the chart for the measured kVp and adding this result to the measured kVp Example The Model 35080B kVp Divider with a Mobile Filter Pack Plus 37946 inserted reads 80kVp The x ray system has 3 3 mm AI total filtration The filtration effect curve of Figure 8 1 indicates a filtration effect of 1 05 kVp per mm Al at 80 kVp The difference in filtration 2 5 3 3 0 8 mm Al is multiplied by the correction value to yield 0 8 x 1 05 0 84 kVp This number is then added to the apparent reading to obtain the actual kVp which is 80 kVp 0 84 kVp 79 16 kVp Filtration Effect kVp Per mm Al 1 6 1 5 1 4 1 3 2 E lt 1 1 1 E 0 9 0 8 ds S 05 04 0 3 0 2 0 1 0 40 50 Model 35080B Reading kVp Figure 8 1 Mobile Filter Pack Plus 37946 Filtration Effect Correction Curve Mobile Filter Pack Plus Option 37946 8 Linearity Corrections 8 4 Linearity Corrections Corrections for linearity of the Mobile Filter Pack Plus 37946 can be made by taking the measured output of the Model 35080B kVp Divider and adding the value in kVp shown on the curve in Figure 8 2 The curve shown by the solid
40. kVp value for all kKVp s measured NOTE See Appendix A for step by step instructions on using the Linear Mammo Filter Pack 37351 in conjunction with the Cadmium K edge Mammo Filter Pack 37355 6 Subtract this kVp voltage from the true K edge kVp value see Section 5 4 This will be the CORRECTION VALUE applied to all kVp measurements made with the Linear Mammo Filter Pack 37351 35080B Operators Manual Blank page CT Filter Pack Option 33551 7 Introduction Section 7 CT Filter Pack Option 33551 7 1 Introduction The CT Filter Pack 33551 provides a non invasive way to make independent tests of the internal voltage divider of a CT system and a convenient and safe way to check tube voltage The actual kV waveform of the CT machine can be displayed on a storage oscilloscope If the CT machine is a DC continuous scan unit the proportional voltage can be read on a DMM These applications are made possible with the CT Filter Pack 33551 in conjunction with the Model 35080B kVp Divider 7 2 Specifications Range 70 to 140 kV Sensitivity 0 1 V 10 kV Cal 0 644 V Zero 60 kV Cal 124 4 kV Linearity Less than 1 kV correction from 70 to 140 kV Calibration Filtration 2 5mm Al Filtration Effect Less than 1 kV per mm Al difference in filtration from the 2 5 mm Al calibration standard over the 70 to 140 kV range Active Area 40 mm x 6 5 mm Minimum Anode Current 25 mA at 25 inches 7 1 3
41. line in Figure 8 2 is normally used for x ray generators with an observed ripple amplitude and frequency of approximately 20 at 2 kHz For best accuracy filtration corrections should be made prior to the linearity corrections However if the difference in total filtration from the calibration standard of 2 5 mm Al is small linearity corrections alone may be sufficient See Section 9 3 for information regarding filtration corrections Example The Model 35080B kVp Divider with a Mobile Filter Pack Plus 37946 has a reading of 83 kVp From the chart a kVp Correction value of 0 9 kVp is obtained Assuming filtration corrections are not Mobile Filter Pack Plus 37946 Linearity Correction Curves 1 5 1 0 5 0 5 05 o 1 3 1 5 N Qa 2 5 N Y 9 me Z Y 3 5 4 r i r r r r r r 40 50 60 70 80 90 100 110 120 130 140 Model 35080B kVp Reading DC to 720 Hz Ripple 20 Ripple amp 2 kHz required for this x ray system the actual kVp is 83 0 9 82 1 kVp Figure 8 2 Mobile Filter Pack Plus 37946 Linearity Correction Curve The kVp Correction Value read from the vertical scale should be added to the Model 35080B kVp Divider reading to obtain the corrected kVp result 8 3 35080B Operators Manual Blank page Low Range Filter Pack Option 38237 9 Introduction Section 9 Low Range Filter Pack Option 38237 9 1 Introduction The L
42. ls below the zero level of 27 kVp the need to make several exposures while varying the kVp as in steps 3 and 4 is negated The difference between the baseline and peak levels can be obtained from the single trace in Figure 6 7 This difference is measured to be 0 100 V and thus the kVp is calculated as follows kVp 27 0 10 0 100 28 0 5 5 35080B Operators Manual Generator Input Filtered Single Phase Generator co D Wei 2 O gt 2 S FE a Cadmium K edge Mammo Filter Pack 37355 Filtered Single Phase Generator Output Volts Seconds Figure 6 7 The Model 35080B kVp Divider Output Waveform with the Cadmium K edge Mammo Filter Pack 37355 single phase mammographic generator 5 6 Cadmium K edge Mammo Filter Pack Option 37355 Operating Instructions 5 NOTE When proceeding to Linear Measurement Section 6 5 Operating Instructions do not change the generator settings 35080B Operators Manual Blank page Linear Mammo Filter Pack Option 37351 6 Introduction Section 6 Linear Mammo Filter Pack Option 37351 6 1 Introduction The Linear Mammo Filter Pack 37351 provides a non invasive way to make kVp measurements of mammographic x ray generators This filter pack features nearly perfect linearity for precision measurements between 22 and 40 kVp for beryllium window molybdenum anode mammographic generators with molybdenum filtration 6 2 Specifications Intended
43. n The kVp divider will provide a voltage that represents 41 kV Adjust the oscilloscope vertical position control to place the trace 0 9 division below the center of the screen 4 Set the FUNCTION switch of the kVp divider to the RUN position The oscilloscope trace will move down to approximately 2 4 divisions below the center of the screen Do not readjust the trace positioning any further 5 The center line on the oscilloscope screen is now adjusted to represent 50 kV Each division represents a 10kV increment One division above the center line is 60 kV two divisions above is 70 kV and so forth Similarly one division below the center line is 40 kV and two divisions below is 30 kV GEOMETRY OF SETUP The Model 35080B kVp Divider with the Low Range Filter Pack 38237 is set up for use in the same manner as described in Section 2 5 for the Wide Range Filter Pack 37617 The normal setup described in Section 2 5 calls for 200 mA and 22 inches Lower current settings may be used in many cases however the detectors in the kVp divider require a minimum intensity below which the output voltage of the kVp Divider develops noise and errors The minimum mA at a given distance varies from generator to generator The typical specification is given for guidance only Ifa particular test setup seems to be giving noisy or erroneous readings increase the mA setting of the generator reduce the distance from the source to the kVp divider or both Wh
44. ns applied When using an oscilloscope as the readout device for the kVp divider first convert all measured voltages to kVp using the standard gain and offset for each filter pack Then these measured values can be converted to actual kVp values using Tables C 1 and C 2 Example The chart below gives a set of sample kVp measurements made following the procedure outlined previously K edge reading uncorrected K edge reading corrected Table C 1 Linear pack reading uncorrected Linear pack reading corrected Table C 2 K edge correction value 0 5 Corrected kVp measurement same as above Once the k edge correction value is determined all subsequent measurements in the same session will use this same value It is not necessary to repeat the k edge measurements in the same session unless the Model 35080B kVp Divider is moved CA Fluke Biomedical Radiation Management Services 6045 Cochran Road Cleveland Ohio 44139 440 498 2564 120 Andrews Road Hicksville New York 11801 516 870 0100 www flukebiomedical com rms
45. nt Do not soak the cloth in the solution you must not let the solution drip inside the instrument 3 Use the moistened cloth to wipe the instrument s exterior cover 4 Let the instrument dry completely before using 10 2 Troubleshooting Difficulties experienced by the Model 35080B kVp Divider user may be caused by problems from one or more of the three sources described below problems with the storage oscilloscope used to obtain the kV reading problems with the x ray machine and either improper technique or an electronic fault with the kVp divider Typically the existence of a problem would be signaled by one of the following 1 No waveform on the oscilloscope trace 2 A strange or unexpected waveform on the oscilloscope trace The information given below is provided to direct the user to the most likely sources of minor problems it is not meant to provide all solutions to all possible problems PROBLEMS WITH THE OSCILLOSCOPE 1 If the oscilloscope settings for CAL and ZERO are not correct a waveform may not be displayed or an unusual or unexpected waveform may be observed refer to Section 4 4 2 The oscilloscope may be grounded or inoperative Check the operation of the oscilloscope 3 The oscilloscope trigger may be set improperly PROBLEMS WITH THE X RAY MACHINE 1 The x ray machine may be inoperative Verify with a dosimeter that the x ray machine is functioning 2 The x ray machine may be arcing Arcing is charact
46. o the RUN mode and make the exposure ak ON 7 5 Correction of Readings Filtration No correction is needed for 2 5 mm Al Refer to Figure 7 1 For a given kV reading if the effective filtration of the CT beam is greater than 2 5 mm Al subtract the difference in mm times the correction factor from the apparent reading if the effective filtration is less than 2 5 mm Al add the difference times the correction factor to the apparent reading Example 1 The kV reading is 100 and the total filtration of the beam is 3 5 mm Al The difference between the effective and calibration filtration is 1 mm This difference times the correction factor for 100 kV is 1 x 0 35 0 35 kV Therefore the corrected kVp is calculated as 100kV 0 35 kV 99 65 kV Example 2 The kV reading is 80 and the total filtration is 2 0 mm Al The difference between the effective and calibration filtration is 0 5 mm The difference times the correction factor for 80 kV is 0 5 x 0 2 0 10 kV Therefore 80 kV is 0 5 x 0 2 0 10 kV Therefore 80 kV 0 10 kV 80 1 kV CT Filter Pack Option 33551 7 Correction of Readings Effect of Filtration on kV D Ge eT KEE A E AN E e e SE Ee DEE O a WEE WEE DES a Ge ae ee ee O p U D O UO Figure 7 1 CT Filter Pack 33551 Filtration Effect Correction Curve Linearity Refer to Figure 7 2 If a kV correction value from the Y axis has a negative sign then its magnitude is subtrac
47. of the filter pack 2 With the function switch of the kVp divider set to OFF adjust the oscilloscope vertical position such that the trace coincides with the bottom horizontal line on the screen This line now corresponds to the Zero offset kVp given on the pack 3 Switch the kVp divider to the CAL position The oscilloscope trace should now be at a level corresponding to the CAL kVp given on the filter pack If this is not the case the gain effects should be corrected before making kVp measurements in the RUN position 4 The gain effects can be corrected by adjusting the fine tuning knob on the Volts div switch of the oscilloscope While still in the CAL position adjust this knob until the trace on the screen corresponds to the kVp value expected for the filter pack in use Measurements made in RUN mode will now be corrected for gain effects 35080B Operators Manual B 3 Voltmeter Measurements If the output of the Model 35080B kVp Divider is connected to a voltmeter a mathematical correction is required to compensate for gain effects The first step in this correction process is to determine the expected and actual voltages when the kVp divider is placed in CAL mode With the filter pack in place switch the kVp divider to the CAL position and read the voltmeter to obtain the actual CAL voltage of the unit The expected CAL voltage is the value listed on the filter pack itself If these values do not agree to within 1 perform the f
48. ollowing correction for all subsequent kVp measurements made using this filter pack Voltages obtained in RUN mode will deviate from correct values by the same ratio as the deviation in CAL voltages That is ActualCAL Voltage Measured Voltage inRUNmode ExpectedCAl Voltage g Corrected Voltage where Corrected Voltage is the true voltage that would be obtained if the gain were accurate Therefore we can obtain a Corrected Voltage for any exposure by rearranging the above equation Expected Voltage in CAL mode Corrected Voltage Measured Voltage Actual Voltage inCALmode The corrected kVp is then calculated as usual by multiplying the Corrected Voltage by the sensitivity and adding the Zero offset kVp of the particular filter pack in use Example A Model 35080B kVp Divider with a Wide Range Filter Pack 37617 50 150 kVp is connected to a voltmeter and switched to CAL mode A value of 0 412 V is observed which is 3 higher than the expected CAL voltage of 0 400 V for this pack Therefore subsequent measurements made with this pack should be corrected The kVp divider is now switched to RUN mode An x ray exposure is made and a voltage of 0 515 V is measured A Corrected Voltage is calculated from the previous equation 0 400V Corrected Voltage 0 515 0 500V 0 412 Using the sensitivity of 0 1 V 10 kV and 40 kVp Zero offset given for this filter pack the Corrected kVp is 90 A kVp of 91 5 would have been measured if
49. on the other hand if this voltage is not greater than the BASE VOLTAGE by 0 1 V repeat this step at one kVp higher Subtract the BASE VOLTAGE from the voltage measured in step 5 Multiply this voltage by 10 and add 27 0 to determine the true kVp for this station Proceed to Section 6 5 Linear Mammo Filter Pack Operating Instructions Example 1 DC Mammographic Generator Figures 5 4 and 5 5 show the input and output waveform obtained from exposures taken at 24 26 and 28 kVp respectively The baseline value of 3 10 V can be seen from the lower pair of traces on Figure 5 5 The level measured on the upper trace is 3 20 V The kVp corresponding to this trace is calculated as kVp 27 0 10 3 20 3 10 28 0 Generator Input DC Generator 24 kV 26 kV 28 kV Input Kilovolts u Milliseconds Cadmium K edge Mammo Filter Pack Option 37355 Operating Instructions 5 Figure 5 4 DC Mammographic Generator Input Waveforms Cadmium K edge Mammo Filter Pack 37355 DC Generator 24 kV 26 kV 38 kV Output Volts al Ya VC em am E G RW E Dei BIER gt Milliseconds Figure 5 5 The Model 35080B kVp Divider Output Waveforms with the Cadmium K edge Mammo Filter Pack 37355 DC mammographic Generator Example 2 Single Phase Mammographic Generator Figures 5 6 and 5 7 show the input and output waveform obtained from exposures taken at 28 kVp Since it can be seen from Figure 6 6 that the kVp fal
50. ow Range Filter Pack 38237 is optimized for measurements in the 30 kVp to 90 kVp range It can be used to make measurements below the 50 kVp lower limit of the Wide Range Filter Pack 37617 and Mobile Filter Pack Plus 37946 on x ray generators with settings below 50 kVp The Low Range Filter Pack 38237 will typically operate at lower mA settings making it useful in taking measurements difficult to obtain with either the Wide Range Filter Pack 37617 or Mobile Filter Pack Plus 38237 at the lower end of their kVp operating range 9 2 Specifications Range 30 kVp to 90 kVp Sensitivity 0 1 V 10 kV Cal 0 150 V Zero 26 KV Cal 41 KV Accuracy 2 exclusive of linearity and filtration effects Minimum Anode Current for less than 1 kV effect Typical at 22 inches with a 3 phase x ray generator 3 mA from 90 kVp down to 50 kVp increasing to 10 mA 40 kVp and 30 mA 30 kVp 9 3 Theory of Operation The Low Range Filter Pack 88237 operates in a manner similar to the operation of the Wide Range Filter Pack 37617 described in Section 3 The thickness and composition of the filters have been optimized for operation over the 30 kVp to 90 kVp range in the Low Range Filter Pack 38237 The filter differences cause the different Cal and Zero voltages specified and require different correction curves shown later in this section 9 1 35080B Operators Manual 9 4 Operating Instructions The operation of the Low Range Filter Pack
51. s the ratio of the x ray signals passing through the two filters As long as the applied voltage to the x ray generator is less than 26 7 kV the output of the kVp Divider is constant approximately 3 volts When the applied voltage exceeds 26 7 kV the ratio and thus the output voltage increases rapidly The filters are carefully manufactured so that the voltage increases at 0 1 V kV above 27 0 kV For molybdenum anode beryllium window generators there is very little effect on the calibration for changes in molybdenum filtration from 12 to 35 microns As shown by Figure 5 2 the addition of aluminum filtration does influence the sensitivity Adding 0 25 mm of aluminum can increase the kVp divider s reading by up to 0 5 kVp Cadmium K edge Mammo Filter Pack Option 37355 Theory of Operation 5 Cadmium K edge Mammo Filter Pack 37355 kVb Correction Curve ra FAS 24 microns molybdenum a c 2 5 U D o O U x pe eck EEE is Se Ee AS 28 5 Indicated kVp Figure 5 2 The kVp Correction Curves for the Cadmium K edge Mammo Filter Pack 37355 5 4 Operating Instructions 1 Measurement Setup Place the Model 35080B kVp Divider in the x ray beam on the compression paddle or other suitable support with the axis of the kVp Divider perpendicular to the axis of the x ray tube Raise the kVp Divider with the Cadmium K edge Mammo Filter Pack 37355 as close as possible to the x ray tube The x ray beam should cover the entire f
52. special circuit intended to prevent the presentation of a distorted waveform at low intensities Section 3 5 Intensity Cutoff discusses the effect of this circuit for single phase waveforms For generators with substantial kV ripple for which the Mobile Filter Pack Plus 37946 is intended this same effect may be noticed As the kV waveform decreases the output suddenly switches to the filter pack s baseline which corresponds to 40 kVp with the Mobile Filter Pack Plus 37946 During the rising portion of the next kV cycle the output will switch back to and follow the actual waveform as shown in Figure 3 3 for the single phase example This is normal operation of the Model 35080B kVp Divider for large ripple signals The filtration and linearity correction curves for the Mobile Filter Pack Plus 37946 are given in the next two sections Two linearity curves are shown The solid line on the linearity graph is the standard linearity curve for an x ray generator with a 2 kHz waveform with 20 observed ripple The dashed line is normally not used but shows the linearity curve for generators with DC to 720 Hz ripple components 8 1 35080B Operators Manual 8 2 Specifications Range 50 to 135 kV Sensitivity 0 1 V 10 kV Cal 0 600 V Zero 40 kV Cal 100 kV Calibration Filtration 2 5 mm Al 8 3 Filtration Effect Corrections Corrections for filtration are made using the correction curve shown in Figure 8 1 The Mobile Filter Pac
53. ted from the apparent reading shown on the X axis If a kV correction value is positive then its magnitude is added to the apparent kV reading on the X axis Example 1 If the apparent reading is 70 kV the correction value is 1 Since the correction value has a negative sign it is subtracted from the apparent reading Therefore 70 kV 1 kV 69 kV Example 2 If the apparent reading is 80 kV the correction value is 0 9 Since the correction value has a positive sign it is added to the apparent reading Therefore 80 kV 0 9 kV 80 9 kV 7 3 35080B Operators Manual Linearity Correction Curve S W I 40 gt E 5 V S O UO Figure 7 2 CT Filter Pack 33551 Linearity Correction Curve 7 4 Mobile Filter Pack Plus Option 37946 8 Introduction Section 8 Mobile Filter Pack Plus Option 37946 8 1 Introduction The Mobile Filter Pack Plus 37946 is a specialized filter pack designed primarily for use on mid to high frequency generators 1 kHz with substantial kV ripple 10 For single phase and 3 phase generators or other low frequency generators lt 1 kHz use of the Mobile Filter Pack Plus 37946 is not recommended The Wide Range Filter Pack 37617 should be used for these applications Measurements below the 50kV operating range of either the Mobile Filter Pack Plus 37946 or the Wide Range Filter Pack 37617 should be made with the Low Range Filter Pack 38237 When an in
54. th this filter pack inserted is connected to a Model 35050A Dosimeter and a kVp of 81 2 is measured When placed in an x ray beam in RUN mode the Model 35050A Dosimeter reads 91 5 kVp The Corrected kVp for this exposure is calculated from the previous equation 80kVp 40kVp 40kVp 90kVp 81 2kVp 40kVp CorrectedkVp 91 5kVp 40 vol B 3 35080B Operators Manual Blank page Appendix C Procedure For Making kVp Measurements Section C Procedure For Making kVp Measurements On Rhodium Anode Rhodium Filtration Selection Of GE DMR Mammography X ray System C 1 Introduction The GE DMR mammography x ray system has both molybdenum and rhodium anode selections Measurements on the Mo anode track can be made in the same manner as on any other Mo anode mammography generator provided Mo is also selected as the additional filter material This involves using the Model 35080B Dosimeter and its two associated mammo filter packs the Cadmium K edge Mammo Filter Pack 37355 and the Linear Mammo Filter Pack 37351 as instructed in the Model 10100A TRIAD Field Service Kit Instruction Manual 37580 or the Model 35080B kVp Divider Instruction Manual 37648 This addendum is intended to provide a method to measure kVp on the rhodium anode track with rhodium also selected as the additional filter material C 2 Procedure NOTE The automatic k edge correction feature of the 35050A available in firmware versions 11 Jan 95 and lat
55. the above gain correction had not been performed B 4 The Model 35050A Dosimeter Measurements The Model 35050A Dosimeter kVp Readout automatically converts the output voltage of the Model 35080B kVp Divider to a kVp value using the sensitivity and Zero kVp offset of the selected filter pack Therefore the method for calculating a Corrected kVp value is slightly different The first step again is to determine the actual and expected values with the Model 35080B kVp Divider in CAL mode In this case since the values are in kVp rather than raw voltages the Zero offset value must be included in the calculation The ratio equation in terms of kVp values is Actual CALkVp Zero offset kvp Measured kVp inRUNmode Zero offset kvp Expected CALkVp Zero offset kvp Corrected kVp Zero offset kWp where the Expected CAL kVp and Zero offset kVp correspond to the values given on the actual filter pack Note that the sensitivity need not be considered since it cancels out of the above equation The Corrected kVp can be obtained directly from this equation by rearranging B 2 Appendix B The Model 35050A Dosimeter Measurements Expected CALkVp Zero offset CorrectedkVp Measured kVp Zero ol Zero offset ActualCALkVp Zero offset Example For the Wide Range Filter Pack 37617 50 150kVp the Expected CAL kVp is given as 80 and the Zero offset value is 40 kVp However a Model 35080B kVp Divider in CAL mode wi
56. to eliminate heel effect The beam must strike the filter pack side of the kVp divider the unit is designed to be turned over for under table x ray heads In setting the x ray generator 200 mA at 22 inches is recommended but the limits of operation allow higher or lower settings and distances Refer to Section 1 4 Specifications for low current limits After correctly positioning the kVp Divider connect the oscilloscope place the kVp Divider in the RUN mode and make an exposure e LONG AXIS OF 35080B TUBE AXIS ABOVE TABLE X RAY TUBE be Sa X RAY TABLE WW AXIS OF 35080B UNDER TABLE X RAY TUBE 2 3 35080B Operators Manual Figure 2 2 Geometry of Setup for Above Table X ray Tube Figure 2 3 Geometry of Setup for Below Table X ray Tube 2 6 Filtration Effect Corrections Corrections for filtration are made with the correction curves in Figure 2 4 Factory calibration of the Model 35080B kVp Divider is performed with 2 5 mm Al total filtration so any other amount of filtration in the beam which is greater than or less than 2 5 mm Al will require some correction of the apparent reading Example Suppose the kVp Divider reads 90 kV using the Wide Range Filter Pack 37617 The x ray machine has 5 0 mm AI total filtration The filtration effect curve for this filter pack indicates a filtration effect of 0 5 KV per mm Al at 90 kVp To determine the actual reading the filtration in the x ray machine
57. vasive kV divider is connected to high frequency high ripple generators for calibration the kV waveform is often substantially changed due to the capacitance of the added high voltage cables When the invasive divider is subsequently removed for normal operation of the x ray system the kVp at any given generator setting may be significantly higher than was measured with an invasive divider The Model 35080B kVp Divider with the Mobile Filter Pack Plus 37946 provides an easy and accurate non invasive method for measuring the kVp of these systems The operating instructions for the Mobile Filter Pack Plus 37946 are the same as given in Section 4 for the Wide Range Filter Pack 37617 with minor exceptions as detailed below The recommended focal spot to kVp divider distance is 12 inches rather than the 22 inches suggested for the Wide Range Filter Pack 37617 The long axis of the Model 35080B kVp Divider should still be perpendicular to the x ray tube axis to avoid heel effect as shown in Figures 2 2 and 2 3 The formula used to calculate the kV is the same as for the Wide Range pack kV Model 35080B voltage x 100 ZERO kV where the ZERO kV is 40 for both the Mobile and Wide Range Filter Packs 37946C and 37167 However when the kVp divider is placed in the CAL mode with a Mobile Filter Pack Plus 37946 inserted an output voltage of 0 600 V 1 should be obtained corresponding to a CAL kV of 100 The kVp Divider has a
58. ys the signal presented to the oscilloscope will suddenly switch to the filter pack s baseline This effect is caused by a special circuit that prevents the presentation of a distorted signal to the oscilloscope This circuit automatically resets about 10 seconds after an exposure is made 3 6 Internal Calibration In order to assure that the ratio circuit in the Model 35080B kVp Divider is stable a CAL position is provided on the function switch When the Model 35080B kVp Divider is switched into the CAL position a signal ratio of 0 25 is electronically switched into the ratio circuit This produces an output of 0 75 volts with no filter pack inserted This value should be within 1 of 0 75 volts When the Wide Range Filter Pack 37617 is inserted a CAL voltage of 0 40 volts 1 is produced at the Model 35080B kVp Divider output The CAL voltage is inscribed on each of the other filter packs The value in kV is also given and this may be used to check the oscilloscope calibration NOTE If the Model 35080B kVp Divider is exposed to an x ray beam while the function switch is left in the CAL position the resulting scope presentation will be badly distorted 3 3 35080B Operators Manual Blank page Test Filter Pack Option 32863 4 Introduction Section 4 Test Filter Pack Option 32863 4 1 Introduction The Test Filter Pack 32863 provides a means for a complete system check of the Model 35080B kVp

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