Home

abovetable x–ray source radiographic systems

1. Il AR 8 04 1 2000 C A B DISTANCE FROM TOP FILM CASSETTE TO BASE OF TEST STAND RECORD VALUE OF C AT ITEM 49 TEST STANO REFERENCE POINT OF SIGHT CONCAVELY CURVED RADIOGRAPHIC TABLE CASSETTE TRAY FILM CASSETTE FIGURE 1 HOW TO DETERMINE DISTANCE FROM TOP OF CASSETTE TO BASE OF TEST STAND FOR CONCAVELY CURVED TABLE TOP PART Il AR 9 04 1 2000 C B A DISTANCE FROM TOP OF FILM CASSETTE TO BASE OF TEST STAND RECORD VALUE OF C AT ITEM 49 TEST STAND RADIOGRAPHIC TABLE REFERENCE POINT IS BASE OF CASSETTE TRAY WHICH REMAINS VISIBLE FILM EVEN AFTER TRAY IS CASSETTE RAISED FIGURE 2 HOW DETERMINE DISTANCE FROM TOP OF CASSETTE TO BASE OF TEST STAND FOR RAISEABLE CASSETTE TRAY PART Il AR 10 04 1 2000 8 7 8 8 8 9 8 10 8 11 9 1 9 3 9 4 ii Manually open the collimator blades fully iii Turn on the light localizer iv Reinsert the cassette tray v Watch the image of the light field on the tabletop to see if the light field adjusts down b If a manual PBL does it prevent the production of x rays until manual adjustments are made Record at item 54 If the PBL is not functioning according to its intended design skip over this section and section 9 0 and explain on a continuation sheet Turn on the light localizer measure to the nearest millimeter the dimensions of the light field at the tabletop Record the light
2. discrete steps select a second setting not differing from the first by more than a factor of 2 and record the mAs product at item 43 The change in tube current may cause a change in tube potential If manual compensation is available readjust the tube potential to its original value and continue with step 5 9 However if the kVp cannot be compensated back to its original setting enter an asterisk in the first column of item 44 skip procedural step 5 9 and state in the Remarks that the kVp could not be compensated While varying technique factors between each measurement as in step 5 3 make four exposures at the selected technique factors Record the exposure readings at items 44 45 46 and 47 PART Il AR 6 04 1 2000 5 10 5 11 6 1 6 2 7 1 7 2 7 3 7 4 Sum the exposures entered on the test record If the sum is 1 R or greater the direct print paper in the slide assembly should provide a satisfactory image Make additional exposures if required to obtain at least 1 R to the ion chamber Remove the cassette from the slide assembly and develop the direct print paper by exposure to fluorescent light Refer to page LINA 1 for proper development techniques If a readable image has not been obtained a new cassette with fresh direct print paper should be inserted and exposed after recheckino light field alignment with the metal markers on the slide assembly 6 0 ADDITIONAL EXPOSURES TO THE UNDERTABLE CASSETTE IM
3. field dimensions at items 55 and 56 Set the source assembly to the second SID and lock into place Repeat the procedure of steps 8 4 and 8 7 Record the indicated SID at item 57 and light field dimensions at items 58 and 59 Remove the first cassette and insert the second Record the film dimensions of the second cassette at items 60 and 61 Check the PBL sizing at two SIDs as detailed in 8 3 8 4 8 7 and 8 8 recording the data in the appropriate spaces of items 62 through 67 9 0 PBL OPERATIONS Turn on the light localizer and close the beam limiting device to the smallest field possible Is it possible to manually adjust the x ray field size to a size smaller than the image receptor Record at item 68 With the x ray field size adjusted to a size smaller than the image receptor pull out the cassette tray change the cassette to one of a different size or rotate the same one 90 and reinsert it Does the beam limiting device return to positive beam limitation Record at item 69 If possible move the source assembly to an SID greater than 36 where the PBL system is not intended to operate Select low range values of tube potential and tube current and an exposure time of 0 5 second or longer Attempt to make an exposure Is x ray production prevented at SIDs where operation is not intended Record at item 70 PART Il AR 11 04 1 2000 10 1 10 2 10 9 10 4 12 1 12 2 12 3 10 0 ACTUAL VERSUS INDICATED FIELD S
4. the above exposure and or timer readings appear suspect i e any two readings differ by 10 percent or more of the greater value make an additional six exposures for a total of ten data points Record at items 31 through 42 If the x ray control is manufactured before May 1994 follow the guidance of paragraph a under each step for this test section otherwise use paragraph b a If the unit under test either does not allow specific selection of tube current or if only mAs is selectable then omit procedural steps 5 6 through 5 9 enter an asterisk in the first column of item 43 on the test record and state ona continuation sheet that the mA is fixed or that mAs is selected b Enter anew mAs product not to exceed twice the first mAs product at item 43 on the test record If anew mAs product cannot be obtained then enter an asterisk in the first column of item 43 on the test record and state on the continuation sheet that the mAs product is fixed a If tube current selection is in fixed steps select an adjacent tube current step and record the indicated value at item 43 b If tube current or mAs is in fixed steps select an adjacent setting and record the mAs product at item 43 a If tube current selection is continuous i e not in discrete steps select a second tube current not differing from the first by more than a factor of 2 and record its value at item 43 b If the tube current or mAs is continuous i e not in
5. the tabletop If only one cassette size is available it may be rotated to swap length and width dimensions provided it is not the same dimension on each side Place the first cassette into the cassette tray and insert the cassette tray Select two SIDs at which the PBL sensors operate preferably one short and one long SID Set the source assembly at the first SID and lock into place Make an exposure to ensure that the system operates at this SID If an exposure is not possible move to a SID at which an exposure may be made Record this indicated SID at item 52 Record at item 53 the type of PBL with which the system is equipped Either the PBL system automatically adjusts the x ray field when the cassette tray is inserted or the PBL system prevents production of x rays until manual adjustments are made or no PBL system is present It may be necessary to consult the user s information to determine at which SIDs PBL is intended If the beam limiting device is not a PBL type then record C at item 53 and record an at item 54 then skip procedure steps 8 6 through 9 4 If the system is equipped with PBL determine if the PBL is functioning as intended a Ian automatic PBL does the unit automatically adjust field size NOTE Since PBL devices by definition must be positive beam limiting the following has been useful in testing the PBL operation i Partially withdraw the cassette tray putting the system into manual mode PART
6. usually expressed as common fraction multiples of 1 120 second while three phase systems usually have timer settings expressed as decimal fractions Is the system single phase or three phase If the system is single phase set the Pulse Fraction Threshold on the MDH to 0 2 and record at item 14 If the system is three phase set it to 0 5 and record at item 14 Set the x ray monitor mode selector switch to PULSE EXPOSURE and the function selector to MEASURE The x ray monitor display should read 0 00 If any other display is present reset the instrument by switching the function selector to HOLD and then back to MEASURE Are the technique factors visible at the operator s position Record at item 15 If multiple tubeheads are controlled by a single exposure switch is there an indication of which tubehead has been selected both at the control panel and at the selected tubehead Record at item 16 Is there a warning label as prescribed in 21 CFR 1020 30 j present on the control panel containing the main power switch Record at item 17 Make an exposure and record the resulting reading at item 18 of the test record Without changing technique factors remove aluminum to obtain totals of 3 5 2 5 and 1 5 mm and repeat the procedure of step 4 11 for each total Record the exposure readings at items 19 through 21 Remove all of the aluminum absorbers from Slot 1 Did the exposures terminate after one of the following a preset tim
7. IZE Does the beam limiting device numerically indicate the field size at an SID at which the diagnostic source assembly can be set Record at item 71 Remove the film cassette Set the diagnostic source assembly to the lowest SID for which the field size dimensions in the plane of the undertable image receptor UTIR are given on the BLD and lock into position Record the SID at item 72 NOTE If the diagnostic source assembly cannot be set to an SID for which field size dimensions are given on the BLD set the SID as close as possible to one provided on the BLD Manually adjust the beam limiting device for an indicated field size e g 8 x 10 inches Record the indicated field size at items 73 and 74 Turn on the light localizer and measure to the nearest millimeter the dimensions of the light field at the surface of the table Record the dimensions at item 75 and 76 11 0 ILLUMINANCE OF LIGHT LOCALIZER If the SID is variable set the diagnostic source assembly to a source to tabletop distance of 42 5 inches 108 cm or the maximum SID whichever is less NOTE the 42 5 inches source to table top places the light sensitive surface of the digiphot 100 cm from the source If a light meter other than the digiphot is used be sure the light sensitive surface is 100 cm from the source Open the beam limiting device to an approximate field size of 10 x 10 Set the photometer on the tabletop Refer to page PHOTO 1 for proper use of the photo
8. PART SYSTEMS FORM FDA 2784 C S D 9 R Q 5 H 2 7 Z oy po eos REPRINTED APRIL 2000 1 1 1 2 2 1 2 2 2 3 2 4 ROUTINE COMPLIANCE TESTING ABOVETABLE X RAY SOURCE RADIOGRAPHIC SYSTEMS Test Procedure ARA Use Form FD2784 1 0 GENERAL GUIDANCE This procedure applies to the testing of any stationary x ray system employing an abovetable source for radiography a conventional undertable cassette tray either manual or both manual and automatic control of radiographic technique factors and a variable aperture beam limiting device The procedure applies to systems operating at fixed as well as variable SIDs that are equipped with either manual or automatic positive beam limiting PBL devices or manual non PBL devices When a step or entire section of the procedure is skipped enter an asterisk in the first data item of that section explain on a continuation sheet why this was skipped and continue on with the next appropriate section NOTE If multiple indicators are provided for a single parameter e g perpendicularity centering kVp and so forth but the indicators do not agree with one another choose the indicator 1 associated with a certified component and 2 most commonly used Note on a continuation sheet that these indicators do not agree and estimate the amount of discrepancy 2 0 PRETEST CHECKLIST Turn on t
9. PORTANT Should you have chosen to use direct print paper in the cassette tray step 3 4 a total exposure of 4 0 to 7 0 R to the ion chamber is necessary to provide a readable image on the direct print paper If the total exposure to the ion chamber step 5 10 is greater than 4 R skip to step 6 2 However if the total exposure to the ion chamber is less than 4 R perform 6 1 Make additional exposures as required to obtain at least 4 R to the ion chamber Check the anode cooling curves to ensure that the rated anode limits are not exceeded Remove the cassette from the cassette tray Develop the direct print paper by exposure to fluorescent light 7 0 SID DETERMINATION With the test stand still in position beneath the source assembly measure the distance from the focal spot to the tabletop to the nearest millimeter Unless the focal spot location is marked on the tube housing estimate the focal spot or source location as being in a plane halfway down the housing end cap from the axial centerline of the tube housing assembly In other words the focal spot is 1 4 the way up the housing end cap from the x ray beam exit side Using the test kit measuring tape measure the distance from the source to the tabletop Record the measurement at item 48 Place a film cassette into the cassette tray Partially insert the cassette tray Measure to the nearest millimeter the distance from the top of the cassette to the base of the test stand a
10. ber as listed on the identification label for the beam limiting device in items 2 and 3 Record the manufacturer s name model number and serial number as listed on the identification label for the x ray table in items 4 and 5 Check the certification status of each component to determine if the components are certified without a variance C certified with a variance V not certified N or not present in the system X DO NOT include other components such as wall cassettes or spot film devices which are not used for abovetable radiography Record this data at item 6 3 0 INITIAL SETUP Turn on the light localizer to assure that it is operable If it is not explain on a continuation sheet and skip sections 8 0 9 0 10 0 11 0 and 12 0 Are means provided to indicate when the beam axis is perpendicular to the plane of the image receptor Record at item 7 If Yes use the indicator s to align the beam axis perpendicular to the plane of the image receptor If use any available method to align the beam axis e g visual inspection Are means provided to center the diagnostic source assembly over the image receptor This requirement can be met by a Bucky light table markings cassette tray center markers a light localizer tubestand detent or other similar devices Record at item 8 Place either a plastic cassette containing a sheet of direct print paper or a loaded film cassette into the bucky tray and center the diagno
11. e interval a preset mAs or a preset number of pulses Record at item 22 NOTE The intent of this question is to identify conditions that pose an imminent hazard e g a system which upon activation of exposure button causes not one but repeated exposures to occur or termination of the exposure occurs only upon release of the exposure switch 5 0 REPRODUCIBILITY AND LINEARITY Reset the x ray monitor so that the display reads 0 00 Without changing the technique factors make an exposure Do not record the resultant reading Without changing technique factors or the x ray monitor settings make an additional exposure The reading will not have a minus sign present Record this reading of exposure at item 23 Switch the mode selector to PULSE DURATION and record this time reading at item 24 Switch the mode selector back to PULSE EXPOSURE PART Il AR 5 04 1 2000 5 3 5 4 5 5 5 6 5 7 5 8 5 9 Repeat step 5 2 for three additional exposures with the exposure readings being recorded at items 25 27 and 29 and the time readings being recorded at items 26 28 and 30 Do not reset the x ray monitor between exposures All variable controls for technique factors shall be adjusted to alternate settings and reset to the test setting after each measurement NOTE The varying of technique factors to alternate settings and then back to the test setting is only applicable to equipment manufactured after September 5 1978 Should
12. he main power to the x ray system Set up the system so that it will operate in the radiographic mode to the undertable cassette tray and bucky Connect the 6 cm chamber to the electrometer Set the x ray monitor mode selector switch to EXPOSURE RATE and the function selector switch to MEASURE Allow the electronics 10 seconds to stabilize After 10 seconds the exposure rate should be less than 4 mR min If it is not the instrument may be defective and you should contact CDRH for guidance If not already completed complete the general information test record Record the five digits which appear preprinted on the general information test record and a unique letter designator in the appropriate block for each page of the abovetable radiographic test record Thus test records for a combination abovetable radiographic undertable fluoroscopic system would be identified as follows Gl12345 general information AR12345A abovetable radiographic UF 12345B undertable fluoroscopic Note that the unique letter designation changes when testing a different X ray source PART Il 04 1 2000 2 9 2 6 2 7 2 8 2 9 3 1 3 2 3 3 3 4 3 5 Verify that the assembler s report FDA 2579 is correctly prepared If it is not write in the correct information above the incorrect information Record the code for the appropriate Test Procedure at item 1 Record the manufacturer s name and model number and serial num
13. just the beam limiting device so that the light field is approximately 4 x 6 at the slide assembly with the longer dimension parallel to the long dimension of the table Using a piece of white paper at the top of the test stand check all edges of the light field against those of the opening in the top of the test stand to make sure that the light field is not shielded by the stand and that it passes through the opening in the top of the stand Define the edges of the light field on the slide assembly grid by placing the metal marker strips so that the outside edge of the marker is along the inside edge of the light field and one end of the marker is along the central line of the grid Again avoid disturbing the slide assembly or the test stand NOTE One method of checking if the outer edge of the metal marker is on the edge of the light field is as follows a Seta sheet of white paper alongside the metal marker b Note the edge of the light field on the paper Move the metal marker so that the outer edge is in line with the image of the light field on the white paper c Setacorner of the white paper on the metal marker so that approximately 1 4 of the marker extends on each side of the triangle formed by the corner of the paper The bright outline of the light field should be co linear with the edge of the metal marker If it 15 not adjust accordingly Quickly recheck the alignment of the source assembly test stand and image recepto
14. meter Turn on the light localizer At or near the center of one quadrant of the light field determine the illuminance by subtracting the ambient light level from the corresponding light level when the light localizer is engaged Do not move the photometer between measurements Record this illuminance at item 77 NOTE Do not apply the correction factor provided on the photometer to any of the measurements The recorded illuminance values must be uncorrected Repeat the measurements at or near the center of the other three quadrants of the light field and record at items 78 79 and 80 12 0 X RAY FIELD LIGHT ALIGNMENT AND SIZE COMPARISON Take the direct print paper that had been in the slide assembly and was developed in section 5 11 Reconstruct the outline of the x ray field using a straight edge and pencil or pen see figure 3 Reconstruct the image of the metal markers to their actual size usually 0 5 x 1 5 PART Il AR 12 04 1 2000 12 4 12 5 12 6 12 7 13 1 13 2 13 3 Measure the dimensions of the x ray field image on the direct print paper to the nearest millimeter Record the x ray field dimensions at items 81 and 82 Measure the light field dimensions by measuring the distance from the outside edges of the image of the marker strips which define the edge of the light field in each direction Record the light field dimensions at items 83 and 84 Measure the distance from the outside edges of the marker
15. nd record at item 49 NOTE If the system is equipped with a concave tabletop measure both the vertical distance from the top of the cassette to any reference point on the test PART Il AR 7 04 1 2000 8 1 8 2 8 3 8 4 8 5 8 6 stand and the distance from that reference point to the base of the test stand Subtract the second measurement from the first and record the difference at item 49 See Figure 1 Some systems are equipped with a cassette tray that raises vertically after it is inserted into the table In this case before the cassette tray is inserted measure the vertical distance from the top of the cassette to a reference point on the cassette tray that will remain visible after the tray has raised into position Insert the tray and activate the raising mechanism Then measure the vertical distance from the reference point to the base of the test stand subtract the first measurement from the second and record the difference at item 49 See Figure 2 8 0 PBL X RAY FIELD UTIR SIZE COMPARISON Remove the test stand and other equipment from beneath the tubehead Select two commonly used sizes of cassettes Record the film dimensions of the first cassette at items 50 and 51 In all cases dimensions of image receptors or light field measurements will be characterized as along the table for a direction along the long dimension of the table and across the table for a direction perpendicular to the long dimension of
16. r Make any necessary adjustments If adjustments are made check the alignment of the marker with the light field as noted in 3 9 Record the indicated SID at item 9 of the test record If the unit operates at a fixed SID that is not indicated look in the user s manual Place a total of 4 5 mm of aluminum in slot 1 of the test stand PART Il AR 3 04 1 2000 3 13 4 1 4 2 4 3 4 4 4 5 CAUTION Consult the system s duty cycle information and anode cooling curves to ensure that the following series of exposures will not exceed the manufacturer s anode heat loading specifications If the proper cooling time between exposures cannot be determined use the following guidance a Rotating anode tubes Wait 60 seconds after every accumulated 5 000 heat units loading of the anode b Stationary anode tubes Wait 30 seconds between exposures of less than 900 heat units and 60 seconds between exposures of 900 to 1800 heat units If a loaded film cassette is used at step 3 4 set the x ray control to 60 kVp and 4 mAs or as close to these technique factors as possible Make an exposure and have the x ray technician process the film for you If a readable image is not obtained at these technique factors adjust the technique factors appropriately and repeat the exposure Set the developed film aside for later determination of the centers alignment and continue with the next step 4 0 BEAM QUALITY If both Manual and Automatic con
17. stic source assembly over the image receptor Set up the test stand and equipment as follows see figure on test record a Place the test stand on the table approximately centered beneath the source assembly with the long axis of the base parallel to the long axis of the table b Attach the spacer assembly to the top of the test stand positioned out of the beam Position the 6 cm chamber in the lower mounting hole of the test stand and secure with the retaining ring d Insert the slide assembly grid side up in slot 6 of the test stand PART Il AR 2 04 1 2000 9 6 3 7 3 8 3 9 3 10 3 11 3 12 e Insert a plastic cassette containing a sheet of direct print paper into the slide assembly Turn on the light localizer and center the test stand beneath the source assembly by centering the light field on the slide assembly grid A piece of white paper in the slide assembly makes visualization of the light field easier during setup Remove it when the setup is complete Lower the source assembly to the minimum SID position or until the face of the beam limiting device comes down close to or in contact with the spacer assembly NOTE In order to reduce the error in the SID measurement adjust the source assembly such that the SID indicator is on a division mark It is not necessary for the BLD to actually be in contact with the spacer assembly Lock the vertical movements of the source assembly and tabletop Ad
18. strips and the outline of the x ray field in the direction along the table Sum the two distances for the total misalignment along the table Record at item 85 Determine the total misalignment across the table the same way as the total misalignment along the table in step 12 6 Record at item 86 13 0 X RAY FIELD UTIR CENTER COMPARISON Depending upon the option chosen refer to either the film that was processed by the x ray technician or to the direct print paper from the cassette tray With a ruler and a pen or pencil trace the perimeter of the x ray field image Draw diagonals from opposite corners of the x ray field to define the center of the field Likewise draw diagonals from opposite corners of the film to define the center of the film Measure to the nearest millimeter the misalignment between the center of the x ray field and the center of the film Record at item 87 PART Il AR 13 04 1 2000 Reconstructed image of metal strips Dashed line gt KEN W 0 coincides with outer i d fine tour In this edges of the fou example metal strips and is the perimeter of the light field Along Table Misalignment L Lo Across Table Misalignment W W3 Edge of x ray field Edge of direct print paper Figure 3 PART Il AR 14 04 1 2000
19. trols are provided for exposure termination select the Manual mode of operation Select a commonly used technique in the above 70 kVp range Record the selected kVp at item 10 a Choose independent values of tube current and exposure time commonly used and record at item 11 and 12 Leave item 13 blank b If only mAs is selectable choose a value commonly used and record at item 13 Leave items 11 and 12 blank If the capability is provided for adjustment of the filtration present in the useful beam adjust for minimum filtration that will allow an exposure in the above 70 kVp range Many systems have an Exposure Hold light to indicate that exposure cannot be made without the filter present in the beam If an exposure is possible with the filtration removed and the Exposure Hold light lit continue with sections 4 0 through 6 0 in this condition of operation Determine whether the system is single phase or three phase using one or more of the following methods a Consult the user information provided by the high voltage generator or x ray control manufacturer b Check the identification plate of the high voltage generator Many times the manufacturer lists the phase of the system along with other electrical characteristics on this label PART Il AR 4 04 1 2000 4 6 4 7 4 8 4 9 4 10 4 11 4 12 4 13 4 14 5 1 5 2 c Observe the time settings on the control panel Single phase timer settings are

abovetable x–ray source radiographic systems

Contents

Download Pdf Manuals

Related Search

Related Contents

abovetable x&ndash;ray source radiographic systems

Contents

Download Pdf Manuals

Related Search

Related Contents

abovetable x–ray source radiographic systems