CT Dose Profiler Help
Contents
1. Philips Philips TX 120 1038 Philips Philips TX S 80 Philips Phiips 8000 90 1096 1888 Philips Philips Mx8000 140 1653 Philips _ Mx8000 IDT Briliance 16 amp Power 90 1072 1 765 Philips PhiligpsBigBore 90 1113 1 996 Philips Philips Big Bore Dicker Picker 1200SX 80 3008 Dicker PickerUlraZ 80 1076 3328 Dicker PickerUltraZ Philips Philips Marconi Mx8000 90 1096 1 888 Marconi Marcoi 8000 90 1096 1888 Marconi JjMaroniM8000 1 140 1653 Shimadzu ShimadzuSCT 80 1134 2470 Siemens emeng DRG 135 J Siemens emeng DPG 135 l Siemens SomatomPlus4Seres 80 1100 2047 Siemens Somatom AR C Siemens Somatom AR T 2014 06 23 6 2A Appendix ER Siemens Somatom AR T 1 067 Siemens Siemens DXP Siemens Siemens Volume Zoom L 80 1200 2135 Siemens lAress__ _ 80 1201 2 135 Siemens Access Siemens EmotonDuo eo 1108 1 951 Siemens Emotion Duo Siemens Sensaion4 LI 80 1 156 1 939 Siemens Sensaiond JI 140 1602 Siemens Sensaton16 LI op 1 42 1893 Siemens Sensation 16 Siemens Sensation t JI 140 1584 Siemens Sensation16Straton 80 1258 1 893 Siemens X Sensation 16 Straton Siemens Sensation16Staton 140 LI 1 571 Siemens2. Ped Head Ped Body 16 cm Phantom Smal Head Head EE Small Body Medium Body 32 cm Phantom Large Body Set values on the console Select the desired Image Thickness Detector Coverage mm Coverage Time 20 0 40 0 l PM 2 0 sec Helical Thickness mm oss 125 25 Coverage Speed 2 75 50 20 62 mm sec Pitch amp Speed mm rot 0 884 1 1 375 1 39 37 55 00 Rotation Time sec 0 516 1 2014 06 23 6 2A CT Dose Profiler User s Manual EM Start measuring 20 Select the kV at which you want to do the measurement and enter it into Ocean 2014 Select one of the supported kVs that was shown when you selected the scanner model see point 12 21 Select the pitch and enter it into Ocean 2014 22 Select the tube rotation time and enter it into Ocean 2014 23 Select Collimation and enter it into Ocean 2014 Ocean 2014 defines Collimation as the total width of the beam the number of slices multiplied by the width of each slice 24 Make sure to select A center for the CT phantom position in Ocean 2014 25 If you want DLP enter the scan length into Ocean 2014 26 Make sure that the Measuring time is set to the same or a slightly larger value than the scan time you noted in point 16 if you specify a longer measuring time than you actually need you lose resolution in the dose profile T E Eja aa ee a nay Head 1 000 171 1 00 d E Head 12
3. 1 25 111 104 0 99 089 085 082 081 O80 079 079 079 079 079 079 080 082 70kv 1 18 1 06 100 0 96 O88 085 0 84 083 O83 O83 0 84 O84 0 84 O85 O86 O87 0 89 BOkV 113 103 0 98 0 95 0 8 087 087 087 0 7 O88 050 091 091 0 93 0 94 O96 098 90kv iii 1 02 0 97 0 95 0 90 O89 0 90 O91 0 92 0 93 0 96 O97 O98 1 01 1 03 105 1 09 100 kv 1 09 1 01 0 98 095 092 092 0 94 0 6 0 7 099 102 104 105 109 111 1 14 1 21 110kv 107 101 0 99 0 6 0 94 0 95 0 97 100 102 105 108 110 1 12 117 1 19 124 133 120kv 1 05 102 1 00 098 096 098 101 104 106 110 114 1 17 1 19 124 127 133 145 130kv 104 1 02 1 01 0 99 0 99 101 105 109 111 115 120 1 23 126 131 135 143 1 56 140kv 104 1 03 102 1 00 101 104 109 113 1 16 121 126 130 1 33 139 145 1 52 1 67 150kv 107 104 1 02 101 104 107 1 14 119 121 127 133 138 142 147 156 162 1 76 Energy correction factors for Head Phantom beam quality RQR Al mm 3 5 7 10 13 19 22 55 kv 0 86 O88 O88 0 89 091 0 92 0 94 amp okv 0 87 O88 089 090 0 92 093 0 95 70kv 0 88 0 89 oan 0 91 0 93 O95 0 97 gokv 0 80 0 91 0 92 0 93 O95 O98 1 00 90kv 091 0 93 0 94 095 O97 101 1 03 100 kv 0 93 0 94 096 097 1 00 1 04 1 06 110kv 0 95 0 97 0 98 1 00 103 1 07 1 10 120kv 0 97 0 99 100 1 03 106 111 1 3 130kV 100 1 01 1 03 1 06 109 115 1 7 140 kv 102 104 1 06 1 09 112 1 19 1 2 150kV 105 1 07 108 1 13 1 16 1 24 1 26 2014 06 23 6 2A CT Dose Profiler User s Manual EUM The CT Dose Profiler Probe Energy correction factors for Body Phantom
4. Equipment E 43 m e E Select equipment E a Generator Tube Manufacturer siemens T Generator name Siemens Somatom Plus 4 mm Madel T 3 5 Serial 78978978 a es n Waveform type HF DC Note 1 m If you want to modify the standard analysis Ocean 2014 Professional is required see topic Modify analysis and Advanced analysis in the Ocean 2014 Reference Manual or Help text A ical CTDI in phantom helical scan This example shows three measurements each with its own analysis Two is a measurement in a head phantom and the other is in a body phantom In this case is only one measurement performed Note e You should use TIMED MODE for this measurement The measuring time is defined by the column CT Dose Profiler User s Manual 2014 06 23 6 2A Create your own templates E N Measuring time e Use Low sensitivity for Head phantom and free in air and High sensitivity for Body phantom The calculation analysis for the first measurement looks like this CTDI 1 spiral scan in phantom Result Pass Set kV 80 kV CTDI 100 c 26 52 mGy CTDI w 30 28 mGy CTDIvol 30 28 mGy DLP 517 8 mGycm Epose rade dnce Default pass fail criteria When you add the CTDI in phantom helical scan analysis the following pass fail criteria is shown Min Max Use CTDI 100 w limit mGy You must choose your own default limits for the pass fail criteria If you leave a limit blank no pa
5. Start measuring Analysis ES Result Pass Set kV 80 kV CTDI 100 c 26 52 mGy CTDI w 30 28 mGy 2 CTDIvol 30 28 mGy DLP 517 8 mGycm Expos re rade gn Gyia 31 The first CTDI measurement is now done You can now measure the remaining CTDI values using the above method 2 2 Measurement free in air The second standard template that comes with Ocean 2014 is for measurements free in air This template calculates CTDI free in air and Geometric Efficiency You perform this measurement the same way as described in the previous section but in this case is no phantom used Hint When you do the free in air measurement you may use the phantom as a holder for the probe as shown in the picture below 1 Go to the Library tab and open the Examples RTI gt Application gt CT folder If you can t find the examples please read the section Load CT Dose Profiler templates 2 Select the template Geometric Efficiency CTDoseProfiler by double clicking on the name CT Dose Profiler User s Manual 2014 06 23 6 2A Start measuring EUM 1 No measurement loaded e Library 3 Real time display templates Examples RTI Applications CT gt FI Session templates Real time display 1 Ven pos Name Last modified Type 4 Se Real time display templates AE TN CIT CINasePrnfiler 2012 03 07 Template b Inbox 2012 03 07 Template 4 4 Examples RTI 4 Applications 3 Load the templ
6. Users of the old software Beginning October 2012 Ocean software replaces the CT Dose Profile Analyzer software All new CT Dose Profiler probes from this date are delivered with the Ocean 2014 software If you already have a probe and are using the CT Dose Profile Analyzer software please note the following e The first version of the CT dose profiler probe called CT SD16 wil not work with Ocean 2014 If you have this probe you have to continue to use the software you have or update to the new probe called CT Dose Profiler e When you start Ocean 2014 for the first time with the CT Dose Profiler probe and you use Piranha Ocean 2014 may show a message that your probe needs to be reprogrammed CT Dose Profiler User s Manual 2014 06 23 6 2A Introduction EM A Your meter s CT Dose Profiler probe is not compatible with Ocean 1 Ouit Ocean 2 Start the RTI Detector Manager If you don t have it installed yeu can find the installer on your CD or in the update package you can download from the RTI website 3 Go to Maintenance 4 Click on CTDP correction 5 Wait while the probe is fixed 6 Quit the Detector Manager 7 Restart Ocean Once you have done this the probe will not work with the CT Dose Profiler Analyzer software the old software To use it with this program again you have to use the Detector Manager again and reverse the fix 1 Start the Detector Manager with the Piranha and the CD Dose Profiler
7. after specifying the manufacturer name CT Dose Profiler User s Manual 2014 06 23 6 2A Start measuring EM Equipment Hjem 3 m Generator 3 Manufacturer Toshiba El a Generator name ld Model e a Serial Waveform type HF DC Md Note 1 d el Note 2 1 Note 3 Note 4 Generator ID Include in reports ial uec When you click on the binoculars the available scanners for selected manufacturer are shown Select generator model Aquilion 16 80 100 120 135 kV Aquilion Multi 4 80 100 120 135 kV i Asteion 120 130 kV i Asteion Dual 120 135 kV Asteion Multi CXB 400C tube 80 100 120 135 kV Asteion Multi older tube 80 100 120 135 kV Auklet 120 kV z Generaic scanner 120 kv Toshiba TCT 600 120 kV Xpress GX Post 98 Asteion 120 130 kV Xpress GX Pre 98 120 kv Xpress HS 120 kV be Xpress HS1 120 kV Xspeed II 120 kV i Xvision EX 120 kV If you don t find the scanner model you are looking for do the following e Select one that is similar to one in the list e Use the Generic scanner e Use your own k factor You must then instead select the CTDI template in the folder User def k factors or if you are using Ocean 2014 Professional modify the template and add a column for the k factor Select one that is similar 1 Select one that you think is similar 2 Edit the model field 3 Proceed according t
8. beam quality RQR Al mm 3 5 7 10 13 19 22 55 kV 60 kV 70 kV 50 kv 90 kv 100 kV 110 kV 120 kV 130 kV 140 kV 150 kV 0 83 0 84 0 85 0 87 0 88 0 90 0 92 0 94 0 96 0 98 1 01 0 84 0 85 0 86 0 88 0 89 0 91 0 93 0 95 0 98 1 01 1 03 0 85 0 86 0 87 0 89 0 91 0 93 0 95 0 97 0 99 1 02 1 05 0 86 0 87 0 88 0 90 0 92 0 94 0 96 0 99 1 02 1 05 1 09 F 0 88 0 89 0 90 0 92 0 94 0 96 0 99 1 02 1 05 1 08 1 17 5 3 Angular dependence This is a graph of the typical angular dependence of the CT Dose Profiler probe measured at 120 KV Normalizedto 0 degrees 30 40 0 89 0 90 0 92 0 95 0 97 1 00 1 04 1 07 1 11 1 15 1 20 0 90 0 91 0 94 0 96 0 99 1 02 1 06 1 09 1 13 1 17 1 22 Angular dependence Free in air 30 CT Dose Profiler User s Manual 20 10 0 10 Degrees 20 30 40 50 2014 06 23 6 2A The CT Dose Profiler Probe 49 5 4 Rotation symmetry The rotation symmetry can be measured by rotating the CT Dose Profiler along its longest axis under an irradiating x ray tube A typical rotation symmetry for one whole rotation is shown in picture below NN PODNE T UN 0 045 0 04 0 035 0 03 0 025 S 0 02 0 015 0 01 Doserate mGy s 0 005 0 l 10 0 d 4 5 8 17 14 16 18 20 5 Time s the output from the tube was going down slightly during
9. have Ocean 2014 Professional Ocean 2014 s helptext and User s Manual give a general description of how to create a template The next two topics give specific information about reguired columns calculations and other information reguired to measure CTDI and Geometric Efficiency using the CT Dose Profiler and Ocean 2014 3 1 CTDI template in phantom The theory behind the method of only one helical scan with the probe in the center hole of the phantom used in Ocean 2014 to measure the CTDI is described in the section CTDI and k factor This section describes what columns and analyses you must include in a template to evaluate CTDI go CTDI CT DI oi and DLP The CTDI analysis is used to evaluate the CT dose index on computed tomography systems using the RTI CT Dose Profiler detector Ocean 2014 uses one helical scan exposure with the CTDP in the center hole of a 5 hole phantom and calculates the CIDI CTDI i and DLP Since a known relationship exists between the the center hole and the peripheral holes only one helical scan measurement is done in the center hole of the phantom to calculate the CTDI This relationship is unique for each CT scanner and is defined in Ocean 2014 as the k factor A list of k factors Ocean 2014 uses is available in the Appendix Use the binoculars to select a scanner from the list Ocean 2014 will choose the correct k factor based the CT scanner name you selected
10. is less than 40 mm Recommended columns or general settings The following columns are recommended for the CTDI free in air helical scan analysis The measured dose from the CT Dose Profiler detector SetlV sd kV The set value for kV CT Phantom type The phantom type specifies head or body for this analysis not required Set value Collimation Set value This column specifies the collimation Pitch Set value This column specifies the pitch Scan length Set This specifies the length of the scan not required value Scan speed Set This specifies the scan speed value Measuring time This is the measuring time for TIMED MODE THis is a meter setting a value used by the meter Tube rotation time This is the tube rotation time Set value 2014 06 23 6 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2014 06 23 6 2A Chapter 4 Theory 4 4 1 Theory CTDI and k factor A quick and convenient way to determine CTDI is to use a method we call the Central Point Method This method is based on the observation that the ratio between CTDI and CTDI og central is a constant for specific CT scanners in combination with the type of phantom used in the measurement see reference 10 If the k factor is known you can perform a CT Dli 00 central measurement and the software will then calculate CTDI and CTDI a automatically The Appendix k factors lists all scanners currently sup
11. probe connected 2 The Detector Manager wil show the probe and its type is PiranhaCT DP du RTI Detector Manager RTI Internal mode Main Detector Calibration Maintenance Help Store to Device vw Add Detector Remove Detector A Add Calibration Calibration TV IF F d R3 ROR W 2 5 mm Al 3 Double click on the probe and the following pop up window is shown Edit Detector Override default detector name Use only when a different detector name than the default name is needed 4 Change the type to CT Dose Profiler 2014 06 23 6 2A CT Dose Profiler User s Manual WR Introduction Edit Detector Type CT Dose Profiler Serial Override default detector name 9999 Use only when a different detector name than the default name is needed 5 Click on OK to close the window 6 Now click on Store to device d RTI Detector Manager RTI Internal mode Main Detector Calibration Maintenance Help D Store to Device 4 Add Detector Detector BR J Calibration CT Dose Firanha Profi MP2 12020 7 Wait until programming of the probe is completed 8 Close the Detector Manager You can now use the probe with the CT Dose Profiler Analyzer od software again Next time you use Ocean 2014 again and Ocean 2014 complains again and asks you to correct the probe you can follow the above procedure CT Dose Profiler User s Manual 2014 06 23 6 2A
12. reproducible results LL PH6115 B05 RSNA 2007 abstract Herrnsdorf L Bj rk M Cederquist B and Mattsson C Thungstr m G Fr jdh C Point dose profile measurements using solid state detectors in characterization of Computed Tomography systems RTI Electronics AB M lndal Sweden and Mid Sweden University Sundsvall Sweden Science Direct dor10 1016 1 01ma 2009 03 159 International Standard IEC 60601 2 44 Particular requirements for the safety of x ray equipment for computed tomography International Standard Geneva Switzerland International Electrotechnical Commission 2002 CT Dose Profiler User s Manual 2014 06 23 6 2A References ER 14 Perisinakis K Papadakis A E Damilakis J The effect of x ray beam quality and geometry on radiation utilization efficiency in multidetector CT imaging Medical Physics Vol 36 No 4 April 2009 15 Palm A Herrnsdorf L Absorbed dose and dose rate using the Varian OBI 1 3 and 1 4 CBCT system Journal of Applied Clinical Medical Physics 16 Dixon R L A new look at CT dose measurement Beyond CTDI Med Phys 30 6 June 2003 0094 2405 2003 30 6 1272 9 17 Dixon R L Restructuring CT dosimetry A realistic strategy for the future Requiem for the pencil chamber Med Phys 33 10 October 2006 0094 2405 2006 33 10 3973 4 23 00 Please find more information about the basis of the dose profile detector in these thesis works Development and evaluatio
13. the long exposure Typical deviation for the CT Dose Profiler probe is about 1 96 5 5 Field size dependence The CT Dose Profiler probe is calibrated with a 5 cm wide field When measurements are performed free in air with small fields 4 cm and down to 3 mm the calibration factor is no longer accurate and must be corrected see picture below This is automaticaly done in Ocean 2014 when you measure free in air and the FWHM lower then 4 cm Field size dependence free in air 1 2 0 8 0 6 0 4 Nomalizedto 4 cm 0 2 0 1 2 3 4 5 6 d 8 Field cm No correction is needed in a phantom due to the large amount of scattering material 2014 06 23 6 2A CT Dose Profiler User s Manual The CT Dose Profiler Probe 5 6 Axial sequential scans vs helical scans The two methods to receive a dose profile axial sequential scans and helical scans have been compared and two dose profiles from the two methods are shown in the picture below The measurement with the axial sequential scans took a long time to perform and the helical scan took a couple of seconds The measurements were made in a phantom without the couch in the beam Helical Signal 300 200 100 0 100 200 300 z axis mm CT Dose Profiler User s Manual 2014 06 23 6 2A Chapter 6 Appendix ER Appendix 6 Appendix 6 1 factors The table below shows the k factors Ocean uses There bis one factor for head and body r
14. the phantom Extension SENSOR Connector The sensor in the CT Dose Profiler probe is very thin 250 um in comparison to the beam width and is therefore always completely irradiated when it is in the beam The sensor is used to collect the dose profile and it can also be used as a trigger As radiation hits SENSOR in either direction the detector registers the dose value at that point and sends the information to the software The electrometer can collect 2000 such dose values per second The recommended and most convenient method to measure the dose profile is to use the update mode caled Timed This mode makes it possible to measure exactly the length of time you like You simply check on the CT system how the scan will take and then use a margin in your choice of Measuring time To be able to collect the dose at the different positions thereby creating the dose profile the probe must be moved through the CT This is achieved by placing it free in air or in a phantom and then using the couch movement to scan the probe In short do a helical spiral scan Therefore it is not possible to use axial scans for measuring CTDI with the CT Dose Profiler probe and Ocean 2014 since then the dose profile is not measured When the table is not moving the CT Dose Profiler acts as an ordinary dose detector and simply gives the point dose reading at that position You can of course make many axial scans in small steps with the detector and plot a dose
15. the text here how to setup the phantom probe and how to set the scanner Assume that you want to measure CTDI 100 using a head phantom First setup the meter phantom and probe CT Dose Profiler User s Manual 2014 06 23 6 2A Start measuring A 1 Connect the CTDP probe to the Piranha via the extension cable If you are using USB cable between the meter and PC connect it now 2 Place the CT head phantom on the head support and the CTDP probe in the center hole with the connector pointing towards the couch as shown in the picture Me Note Only one exposure with the probe in the center hole is required The section Theory of CTDI and k factor describes the theory behind this method 3 Make sure that the sensor is in the center of the phantom This can be accomplished easily by using the graded scale on the CTDP probe Assuming you are using a standard phantom with a length of 150 mm the stitched mark at 75 mm on the CTDP probe should be place in the phantom opening and the end of the extension should then be at the end of the phantom as shown in the pictures below A 4 Make sure that the two horizontal CT lasers are visible on the probe approximately in the middle of it Also verify that the vertical laser is approximately in the middle of the phantom Center the CT at this position put this position to zero 5 Put a piece of tape along the probe attaching it to the phantom This is to e
16. 1 000 171 1 00 12 00 In 3 100 Body 12 1 000 171 1 00 12 00 16 You are now ready to perform the measurement Timed mode will be used and you must start the measurement manually before you start the CT scan 27 Click the Start button in Ocean 2014 and begin the CT scan from the console Rm EE EE h gt KR d i ia Data link z i Central database Measure Design Appearance Reporting Help 2 Clear row Ee Ex Clear all POSLI Detector New Quick Favorites sista nt Close Check Edit Measure i le FR wen KE e EB DE rl TE uu FF J TO Start Measuring Men nd VV A LEE FEET a 28 You will see how the measurement is progressing on Ocean 2014 s status bar Im ui Lue meas E 1 Untitled HT Measurements amp Library The dose profile will now be measured Be sure that the entire scan is covered by the measuring time you have chosen If not you should increase the measuring time in Ocean 2014 and redo the measurement 29 As soon the measurement is completed Ocean 2014 will display the dose profile and calculated data The dose profile is Shown in the waveform window and the total measured dose is shown in the Exposure column in the grid CT Dose Profiler User s Manual 2014 06 23 6 2A Start measuring EM s 1 Toshiba huvudfantom E Measurements gt een mre rr Free mre ll cm o pues ES 1 000 2 120
17. 87 1 656 1 614 LightSpeed16 CT 80 1046 41819 1 627 1 611 1 483 LightSpeedPro16 1 80 1057 1 996 1771 1 652 1 577 LighSpeed RT 80 1093 2140 1 897 1 770 1 694 LightSpeed VCT 80 1136 2 046 1 778 1 648 Optima CT660 1 Optima CT660 1 Optima CT660 DiscoveryCT750 TI VTT ITI ITI TT FTT rm TT ITI FTT TT TT ITI WT FTT FTT FTT TT TT IT TT VT FTT FTT TT FTI ITI TT VT FTT TT TT TT ITI ITI ITI ITI ptima CT660 80 2010 Optima CT660 100 1 810 Optima CT660 1 700 Optima CT660 140 1 50 Discovery CT750 80 0965 24100 1 850 1 730 1 670 DiscoveryCT750 small bd 1 120 1 560 1 700 hilips hilips hilips hilips hilips Philips 310 GE3 noCu 120 1 956 hilips Philips 350 GE3 noCu 120 1 956 hilips Philips 310 GE3 w Cu 120 hilips Philips 350 GE3 w Cu IL 120 hilips Philips AV 1 80 1 20 2034 hilips 1 795 hilips 1 718 hilips 1 739 hilips 1 666 hilips Philips LX 80 1 20 2 034 hilips 1 795 hilips 1 718 hilips 1 739 hilips 1 666 hilips Philips SR7000 _ _ 80 1120 2 034 hilips 1 795 hilips 1 718 hilips 1 739 hilips 1 666 hilips 1 572 hilips 1 572 2014 06 23 6 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 54 Appendix 1 053 Philips Philips TX 3400 J vo
18. CT Dose Profiler Probe for evaluation of CI systems CT Dose Profiler User s Manual English Version 6 2A RTI article number 9630512 00 CT Dose Profiler User s Manual 2014 06 23 6 2A CT Dose Profiler The CT Dose Profiler probe makes it possible to evaluate the performance of modern CT scanners VU Rm NOTICE RTI Electronics AB reserves all rights to make changes in the CT Dose Profiler and the information in this document without prior notice RTI Electronics AB assumes no responsibility for any errors or consequential damages that may result from the use or misinterpretation of any information contained in this document Copyright O 2012 2014 by RTI Electronics AB All rights reserved Content of this document may not be reproduced for any other purpose than supporting the use of the product without prior permission from RTI Electronics AB Microsoft Microsoft Excel Microsoft Access Windows Win32 Windows 95 98 ME NT 2000 XP 2003 Vista Windows 7 and Windows 8 are either registered trademarks or trademarks of Microsoft Corporation in the United States and or other countries OpenOffice org and OpenOffice org Calc are registred trademarks of OpenOffice org BLUETOOTH is a trademark owned by Bluetooth SIG Inc USA Contact Information World Wide RTI Electronics AB Flojelbergsgatan 8 C SE 431 37 MOLNDAL Sweden Phone Int 46 31 7463600 E mail Sales sales rti se Support support rti se
19. Emotion LI 80 0821 1751 Siemens Sensation 10 80 1155 1 93 Siemens SensationtO 140 1584 Siemens SensatonOpen 80 1 071 1812 Siemens Sensation Open Siemens SensaionOpen Ian 1558 Siemens Sensaton64 80 1 042 1 684 Siemens Sensaion64 _ 140 1538 Siemens DefinitionAs eo 1054 1851 Toshiba Xspeed Il Toshiba Xpress GX Pre 98 120 1035 J 2014 06 23 6 2A CT Dose Profiler User s Manual oshiba oshiba Aquilion Multi4 eo 1117 20722 oshiba Aauilion Multi 4 oshiba Aquilion Multi 4 oshiba oshiba oshiba i ma oshiba Asteion Multi older tube 1 099 2 039 oshiba Asteion Multi older tube 1 076 1 731 oshiba oshiba Asteion Multi CXB 400C tube 80 1 141 2131 oshiba oshiba oshiba oshiba oshiba oshiba AqulIon 6 80 1 147 2200 oshiba Aquilion 16 oshiba Aquilion 16 oshiba oshiba CT Dose Profiler User s Manual 2014 06 23 6 2A Chapter 7 References ER References 7 References 1 10 11 12 13 Vrieze T Bruesewitz M R Primak A Zhang J McCollough C H CT dosimetry A comparison of measurement techniques and devices Department of Radiology Mayo Clinic College of Medicine The study will be presented at RSNA 2006 Appendix MSCT Dosimetry guidelines on radiation dose to the patient Karlsson H A new detector for measurements of CT
20. Head 12 1 000 171 es ER 16 in 3 100 Body 12 1 000 171 1 00 12 00 16 Make the necessary adjustments and redo the measurement if you don t get a value in the Exposure column The waveform graph shows the dose profile Waveform Waveform data P CTDI 100 c 26 52 mGy Exposure rate m Beam width FWHM N A 0 1 1 1 10 12 4 4 1 6 Geometric efficiency N A 104 Between cursors I I Dose 27 82 mGy 97 I CTDI 27 82 mGy el I Time 9751ms i i Length 117 0 mm Ti o I E 6 i o I Sei h i o U I a 44 o I Lu 3 2 H I I I 1 Sojnm ewe H 7 m 0 20 40 60 80 100 120 140 160 180 Z axis mm There are two cursors that can be moved Corresponding cursor values are shown in the waveform data window The center indicator can be moved manually This can be useful in situations when Ocean 2014 isn t able to find the correct center position When the center indicator is moved all values related to its position and the 50 mm indications are recalculated To move the center indicator just move mouse pointer over it and use drag and drop Right click on the graph and select Auto position center indicator if you want to restore the automatically calculated position Waveform Exposure rate Exposure rate mGy s 30 The calculated values are shown in the Analysis window 2014 06 23 6 2A CT Dose Profiler User s Manual EN
21. Introduction ER 1 2 1 3 Help in Ocean 2014 The manual for the CT Dose Profiler is available as a help tutorial in Ocean 2014 Go to the Help page on the ribbon bar Design Data link RE ce sporting Central database Help Table of FAO le Measure 2 Setup Contact Activate Chec contents started M RII meter updal Help Tutorials Your first CTDI measurement w Connected Design your awn templates Theory af CTDI and k factor Click on the CTDP tutorial button and select what you want to read about The RTI Mover The RTI Mover is an accessory that can be used with the CT Dose Profiler Probe and is supported in Ocean 2014 The RTI Mover makes it possible to measure CT dose profiles with an axial scan The RTI Mover is described in a separate manual RTI Mover User s Manual 2014 06 23 6 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2014 06 23 6 2A Chapter 2 Start measuring 2 2 1 BET Start measuring Start measuring The Ocean 2014 software is used to evaluate and calculate all parameters based on the measured dose profile Ocean 2014 is available in three different license levels Display Connect and Professional Depending on the level you are running you have different possibilities Connect You can use Quick Check or the templates that come with Ocean 2014 These templates are locked and you cannot modify the structure However you
22. Service service rti se Web site http vwwrti se CT Dose Profiler User s Manual Contact Information United States RTI Electronics Inc 33 Jacksonville Road Building 1 Towaco NJ 07082 USA Phone 800 222 7537 Toll free Int 1 973 439 0242 Fax nt 1 973 439 0248 E mail Sales sales rtielectronics com Support suppor rtielectronics com Service service rtielectronics com Web site http wwwrtielectronics com 2014 06 23 6 2A Intended Use of the CT Dose Profiler probe Together with the Ocean Software from RTI Electronics AB it is to be used for quality control service and maintanance of CT systems With the CT system in stand by condition without patients present the probe is intended to be used to provide the operator with information on radiation beam parameters that might influence further steps in an examination but not an ongoing exposure for assessing the performance of the CT scanner for evaluation of of examination techniques and procedures for service and maintanance measurements for quality control measurements for educational purposes authority supervision etc The product is intended to be used by hospital physicists X ray engineers manufacturer s service teems and other professionals with similar tasks and competencies The operator need s basic knowledge about the software Ocean before starting to use the CT Dose Profiler probe This can be achieved by studying the rel
23. a mm mm s mm s s mGy 12 16 In 2 120 Head 12 1 000 171 1 00 12 00 16 la 3 100 Body 12 1 000 171 1 00 12 00 16 Grid with set values and measured total exposure ddd PLEIN 1938 4 quawidinb3 The dose profile is shown Waveform data is shown Calculated values are shown here v here t here V Waveform data Analysis 8 Show hide Cursori_ Cursor2 Diff CTDI 1 spiral scan in phantom Exposure Set kV 100 0 kV E CTDI 100 c mGy CTDI w mGy Between cursors sn CTDIvol mGy Exposure DLP mGycm Exposure rate Waveform not available CTDI 2 spiral scan in phantom a 2 E Analysis Comment 7 Piranha Real time display Ej Log mode KA Charging Not Available Pressure kPa Note Waveform grid cursor data and analysis are empty right now since no measurement has been performed yet The template performs four different CTDI measurements note only one exposure is needed for each one two with head phantom and two with body phantom You can change Set kV and phantom type if you want 10 The first thing you should do is to select CT scanner in Ocean 2014 Go to the Equipment tab 11 Specify the CT scanner manufacturer CT Dose Profiler User s Manual 2014 06 23 6 2A Start measuring CR Equipment me 43 Generator Tube Manufacturer E Genera
24. actor in the section Theory of CTDI and k factor A more complete list of k factors is available in the Appendix section of this manual 14 If you know the total filtration go to the Tube tab and enter it If you don t know use the default value 7 mm Now it is time to prepare the CT settings You will be required to perform the following perform a topogram a scout image know how to set the cursors to define the scan area for the spiral helical scan and be able to perform the scan It is very important that these CT parameters are read and set correctly otherwise the measurement will be incorrect 2014 06 23 6 2A CT Dose Profiler User s Manual EM Start measuring 15 First perform a topogram scout image over the whole CT Dose Profiler when it is positioned inside the phantom Ocean 2014 is not used at this stage and the meter will not record any data You do not have to be concerned with any settings or measured data since the reason for this scan is to find out where to set the cursors of the CT machine for the helical scan 16 The CT console will show the scanned image similar to the one below Locate the sensor in the scanned image Set the start cursor approximately 3 cm before the phantom and the end cursor approximately 3 cm after the phantom While these are not exact numbers the measurement should start a little bit before the phantom and stop a little bit after it Note down the scan time that the CT unit needs to
25. al calculation 24 Measuring time 16 30 Mover 13 N NI 35 42 CT Dose Profiler User s Manual O Ocean Connect 16 Prodfessional 16 templates 10 P Pass Fail define 30 35 Phantom body 16 head 16 Phantom type 16 Pitch 16 30 35 42 Position phantom 16 probe 16 Professional 16 Quick Check 16 R H3 47 Rotation symmetry 49 RQR 47 RTI Mover 13 Scan axial 50 helical 50 Scan length 16 30 35 Scan speed 30 35 Scanners body 52 head 52 k factor 52 supported 52 tube voltage 52 Select CT scanner 16 Sensitivity 46 Sensor 46 Set kV 30 35 Set values 16 CT Dose Profiler User s Manual SFOV 16 ra Templates 10 Timed mode 46 Tube filtration 16 Tube rotation time User k factor 26 Volume CTDI 42 W Waveform 16 Weight 46 Weighted CTDI 42 ETE 33 index 30 35 2014 06 23 6 2A
26. anced analysis in Ocean 2014 Reference Manual or Help text for more information free in air helical scan test ical CTDI and Geometric Efficienc This example shows three measurements each with its own analysis Only the first measurement is performed in this case View Select Set kV Collimation Pitch Tube rotation time Scan speed Measuring time Exposure kv mm mm s 3 mGy n 2 120 12 1 000 1 00 12 00 15 n 3 120 12 1 000 1 00 12 00 5 Note e You should use TIMED MODE for this measurement The measuring time is defined by the column 2014 06 23 6 2A CT Dose Profiler User s Manual E N Create your own templates Measuring time e Use Low sensitivity for Head phantom and free in air and High sensitivity for Body phantom The calculation analysis for the first measurement looks like this Hesult Pass Set kV 120 kV Geometric efficiency 85 7 9b Beam width FWHM 27 7 mm CTDI 100 83 21 mGy E nig ee p Ex BE Default pass fail criteria When you add the CTDI helical scan free in air analysis the following pass fail criteria is shown Hin Max Geometric efficiency E Beam width FWHM mm No default limits are specified you must fill out limit If you leave a limit blank not test for that criteria is done Result layout and macros As described in the topic Advanced analysis in the Ocean 2014 Reference Manual or in the Help text it is possible to modify th
27. ate EE TE mm o 5 mGy E i 5 1 000 In 3 120 12 es 1 00 12 00 3 4 You must enter the parameters below before you can perform your first measurement kV Pitch Tube rotation time s Collimation mm 5 Now perform the measurement the same way as the CTDI measurement described in the previous section 6 As soon the measurement is completed Ocean 2014 will display the dose profile and calculated data The dose profile is Shown in the waveform window and the total measured dose is shown in the Exposure column in the grid 1 000 24 00 2 120 12 1 000 T 12 00 15 In 3 120 12 1 000 1 00 12 00 5 Make the necessary adjustments and redo the measurement if you don t get a value in the Exposure column The waveform graph shows the dose profile Waveform 98 Waveform data IS CTDI 100 c N A Exposure rate Time s Beam width FWHM N A 0 30 50 55 60 s Between cursors 80 Dose 83 21 mGy CTDI 83 21mGy 70 Time 4399 ms Length 105 6 mm DU e 50 ce 5 o 40 5 Gd n e OI 20 10 0 120 140 Z axis mm 2014 06 23 6 2A CT Dose Profiler User s Manual 2 3 ER Start measuring There are two cursors that can be moved Corresponding cursor values are shown in the waveform data window If the center point and FWHM can t be found automatically the analysis will show a calculation error In this case in the wavefor
28. calculation right click on the waveform graph and check Auto position center indicator The central CTDI CTDI 100 c is calculated as CTDIc Integrated dose between X4 and X5 Pitch Pitch must be specified in the grid The weighted CTDI CTDI 100 w is calculated as CTDIw CTDIc kFactor The k factor is from the table in the Appendix The k factor is found based on kVp phantom type and CT scanner name If you want to specify your own k factor add the k factor column to the template The volume CTDI CTDI 100 vol for a helical scan is calculated as CTDIvol CTDIw Pitch The dose length product DLP is calculated as DLP CTDIvol Scan length CT Dose Profiler User s Manual 2014 06 23 6 2A Create your own templates E N 3 2 Recommended columns or general settings The following columns are recommended for the CTDI in phantom helical scan analysis Exposure Measured The measured dose from the CT Dose Profiler detector Set kV The set value for kV CT Phantom type The phantom type specifies head or body for this analysis Set value CT phantom position This specifies where the CT chamber is positioned in the phantom not Set value reguired center hole is assumed if not specified Collimation Set value This column specifies the collimation Pitch Set value This column specifies the pitch Scan length Set This specifies the length of the scan value Scan speed Set This s
29. can change set values and parameters that are used to make the measurement and evaluate the result You can only use real time display mode Professional You can use Quick Check or the templates that come with Ocean 2014 but you can also create your own templates This gives you more possibilities to adapt the templates to your own needs add pass and fail criteria and more You can do both real time display measurements and include the CT Dose Profiler measurements in a QA session The CT Dose Profiler probe is a point dose detector that has a solid state sensor placed 3 cm from the end of the probe The probe can be extended with an extension piece made of PMMA to fill different phantoms The extension is 45 mm When this is attached the detector will be centered in the middle of a 150 mm wide PMMA phantom when the end of the extension reaches the end of the phantom Extension SENSOR Connector The sensor is very thin 250 um in comparison to the beam width and is therefore always completely irradiated when it is in the beam The sensor collects the dose profile As radiation hits the sensor in either direction the detector registers the dose value at that point and sends the information to the software The electrometer can collect 2000 such dose values per second When the dose profile is collected all of the data points are put into a graph The recommended and most convenient method to measure the dose profile is to use Timed mode T
30. dose profile CTDI and CT tube variations Poster Can be downloaded from http www rti se m the section Application Notes Karlsson H Development and evaluation of a new detector and software for measurements of CT dose profile CTDI and CT tube current variations Master Thesis Department of Radiation Physics Goteborg University Goteborg Sweden 2004 Nagel H D Radiation Exposure in Computed Tomography Fundamentals Influencing parameters Dose Assessment Optimisation Scanner Data Terminology 4th Edition Hamburg Germany December 2002 CTB Publications D 21073 Hamburg ctb publications gmx de Stamm G Nagel H D Software CT Expo Medizinische Hockschule Hannover D 30625 Hannover stamm georg a mh hannover de International Standard IEC 61267 Medical diagnostic X ray equipment Radiation conditions for use in the determination of characteristics 1994 Morin Gerber and McCollough Radiation Dose in Computed Tomography of the Heart by American Hart Association Inc 2003 ACR Practice Guideline for Diagnostic Reference Levels m Medical X Ray Imaging 2002 Res 20 Cederquist B Evaluation of two thin CT dose profile detectors and a new way to perform QA in a CTDI head phantom Master Thesis Department of Radiation Physics G teborg University G teborg Sweden 2008 Vrieze T Bauhs J McCollogh C Use of spiral scan acquisition for CT dose measurements Selection of optical pitch values to ensure
31. e the layout of the analysis result The layout is defined as text combined with macros When the analysis result is shown the macros are replaced with the appropriate calculated values set values and measured values The default layout of text CTDI free in air helical scan analysis looks like this CT Dose Profiler User s Manual 2014 06 23 6 2A Create your own templates ma Title Result STestResult Set kv PoetkV kV Geometric efficiency SGeometricEfficiency 56 Beam width FWHM BeamWidthFWHM mm CTDI 100 2CTDI100 5UnitC TDI100 DoseProfileGraph This text can be modified and more macros can be used to show more calculated results for example the relative difference The following macros are available for the CTDI free in air helical scan analysis STitle Specified title SResult Analysis result STestResult Pass or fail text the overall result for the test SSetkV Set kVp 55etmAs Set mAs SSetPitch Set pitch 5et5canTime Set value for the scan time SSetTubeRotTime 5et tube rotation time S SetCollimationMT Set value for the collimation SSetPhantomType Set value for phantom type SScanSpeed Calculated scan speed Set Pitch Collimation NT Set Tube Rot Time SDoseProfileGraph The CT dose profile graph SCTD OO Measured CTDILOU SUnitCTDILOO Unit for CTDT SBeamWidthFWHM Beam width from waveform SMinBeamWidthFWHM Minimum value SMaxBeamWidthFWHM Maximum value SGeometricE
32. ee graph above represents the position of the sensor and the y axis represents the exposure rate The waveform includes a maximum of 1024 samples Ocean 2014 finds key locations in the waveform in the following way 1 Find the maximum dose rate that occurred during the scan 2 Search backward from this point to find where the dose profile goes below 50 of the maximum value and call this position X1 not shown on graph 3 Search forward from the point found in step 1 to find where the dose profile goes below 50 of the maximum value and call this position X2 not shown on graph 4 Calculate the position halfway between X1 and X2 Call this point X3 shown as a solid red line in graph above 5 Calculate X3 50 mm and X3 50 mm and call these positions X4 and X5 respectively They are marked with red dotted lines in the graph above and labeled with the text 50 mm and 50 mm respectively If the points X1 and X2 can t be found automatically the analysis will show a calculation error In this case in the waveform graph not the analysis graph use the mouse pointer and grab the center pointer You can now move it Position it manually in the center of the dose profile Two new indicators for FWHM become visible Move these and position in a position where the dose rate is half of the maximum dose rate Now are all parameters in the analysis calculated based on the manual positions you have done If you want to go back to automatic
33. es in the phantom That makes it hard to measure reproducible values if a suitable pitch is not used a so called target pitch The target pitch can be calculated with the following equation FWHM S R Target pitch x NT 5 where S is the distance between the x ray source and CT center and R is the distance between the CT center and the detector Observe that you have to know the FWHM in the center of the CT Few CTs have the possibility to scan with any pitch value which makes it hard to perform this measurement A pencil ion chamber is not affected by the divergence in beam width and distance the same way as a point detector The CTDI oo p from a measurement with the pencil ion chamber and the point dose detector are a little hard to compare but the point doses simulate the dose to a point in a phantom better This is the reason why it is recommended to use the one exposure method with the k factor CT Dose Profiler User s Manual 2014 06 23 6 2A Chapter 5 The CT Dose Profiler Probe EM The CT Dose Profiler Probe 5 5 1 The CT Dose Profiler Probe The CT Dose Profiler has one solid state sensor placed 3 cm from the end of the probe The probe can be extended with an extension piece made of PMMA to fill different phantoms The standard extension is 45 mm When this extension is on the detector will be centered in the middle of a 150 mm wide PMMA phantom when the end of the extension reaches the end of
34. espectively The k factors are based on data from impactctscan org Name kVp Head Bod Iscint 1 527 Iscint Exel2400Electt 140 LL 1430 Iscint 1 466 Iscint Helicat 1 466 Iscint 1 500 1 680 1 585 9800 Series 1 503 HiLight L eo 1047 1 00 1 636 1 605 1 571 HiSpeedCT inoSmartBeam__ 80 1 047 1 00 1 636 1 605 1 571 HiSpeed CT i with SmartBeam 80 1 047 2093 1 827 1 607 1 568 1 505 Pace 80 1162 2 164 1 734 1 627 Pace 1 636 Ser 80 1 62 2 164 1 734 1 627 1 636 Prospeed 1 713 1 610 80 1145 2213 1 692 1 605 80 1145 2213 1 692 1 605 80 1032 1927 1 730 1 633 1 570 amp B o 9 CD CD Q TI TI ITI ITI TT TT ITI TT FTT FTT FTT TT ITI TT ITI VT FTT FTT TT ITI ITI TT FTI FTT TT TT TT ITI FTI FTI FTT TT FTI TT ITI WT FTT FTT FTT TT ITI ITI TT FTT FTT FTT ITI ITI jrm LightSpeed 80 1032 4927 1 730 1 633 1 570 LightSpeedPlus 80 1032 1927 1 730 1 633 1 570 HiSpeedZXi LI 80 1027 1 810 1 500 iSpeed ZX i 0 968 1 480 CT Dose Profiler User s Manual 2014 06 23 6 2A Appendix HEST ightSpeed VCT 1 566 ightSpeed VCT small hd large bd 80 1 061 2041 ightSpeed VCT small hd large bd 1 802 ightSpeed VCT small hd large bd 1 684 ightSpeed VCT small hd large bd 1 614 HiSpeed HL 80 1027 1810 1 500 1 480 LightSpeed Ulta 80 1042 2009 1 7
35. ess ai cS 52 XE RTC LOIS a ke i AS A O 52 PROTO EI GS radis ETT dh Bitan 58 Ile GEN 61 2014 06 23 6 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2014 06 23 6 2A Chapter 1 Introduction BET Introduction 1 1 Introduction Regular quality assurance measurements on CT scanners are necessary in order to monitor the dose levels patients are exposed to during medical examinations In many countries governments require regular quality compliance testing information from clinics and hospitals that perform CT examinations Today computed tomography CT comprises approximately 70 of the total dose given to patients during X ray examinations With the rapid advancements in CT technology there is increasing demand to develop new testing strategies and measuring equipment to maintain the highest possible standard of patient care It was found that using the standard 10 cm CT ionization chamber may result in inaccurate measurements due to its tendency to underestimate the dose profile Our answer to this problem is the CT Dose Profiler CT DP probe The CT Dose Profiler CTDP probe is a highly advanced point dose probe designed to fit into the standard phantoms to evaluate computed tomography systems There is no limit to the slice width that users can measure with the CTDP When using this probe for CTDI measurements the traditional five axial scans with an ion chamber are replaced with one helical spiral scan with
36. evant documentation The product is NOT intended to be used for direct control of any diagnostic X ray system performance during irradiation of a patient so that patients or other unquilified persons can change settings of operating parameters during and immediately before and after measurements 2014 06 23 6 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2014 06 23 6 2A Contents Nar Table of Contents 1 IDITOOU C GOl ue uy DF Ry Ne Odd nU UN SN 10 1 1 Users of the old software scenen kaaa kaaa aaa kaaa II IL IIu 10 1 2 Help in Ocean 2014 E 13 deer TOER TEN o u pe e e o e e en 13 Start measuring iaai da e od A Sd 16 2 1 Make your first CTDI measurement 16 2 2 Measurement free in air summer kaaa kakaa 24 2 9 Unlisted al 26 Create your own templates aaa aaa aaa aaa aaa aaa anna 30 3 1 CTDI template in phantom cement AAA LILI A ELLER LEE LILI kakaa 30 3 2 CTDI free in air and Geomtetric Efficiency template eee 35 EE EE 42 4 1 CTDI and k factor E 42 4 2 Whyuse a k factor ere 44 The CT Dose Profiler Probe 1 aaa KEEN aaa aaa aaa nana 46 cubes ER TU 46 92 ee ee Ee e EE 47 5 3 Angular dependence usenet kr Lk ERE REEL REELLE ER EL EL REELLE NE ELLE dasaka 48 SP ROION SVIME ER 49 9 9 Field size dependence aaa aaa aaa aaa aaa kaaa kaaa kaaa aaa aan 49 5 6 Axial sequential scans vs belcalecanme anna LL LL LL LEE 50 PRD Car
37. f k factors for common CT units are used by the software and listed in the Appendix k factors The factor is calculated by dividing CTDI with CT Dli gg central from measurements obtained with pencil ion chambers CTDI C TDI 100 center For head phantoms the k factor is around 1 and for body phantom the k factor is around 1 7 at 120 kV 2014 06 23 6 2A CT Dose Profiler User s Manual 4 2 Why use a k factor To measure the CTDI og with the CT Dose Profiler in the center hole of a head or body phantom with one helical scan exposure and then multiply it with the k factor to get CTDI and CTDI a is of course faster than doing the five exposures with the pencil ion chamber With the CT Dose Profiler you can also see a visible image of the dose profile that will tell you if something is wrong with the system Another reason why the k factor should be used is that it is hard to compare axial measurements over a pencil ion chamber with helical measurements over the CT Dose Profiler in the peripheral holes The nominal beam width is defined in the center of the CT where it is constant during the rotations If you move a detector outside the center axis the beam width and dose rate will oscillate during the rotation The pencil ion chamber is only partly irradiated so it is not affected the same way by the inverse Square law and divergence in the beam width as a fully irradiated detector Measurements with the pencil ion chamber do n
38. fficiency Geometric efficiency from waveform SMinGeometricEfficiency Minimum value SMaxGeometricEfficiency Maximum value 2014 06 23 6 2A CT Dose Profiler User s Manual E N Create your own templates Calculations The CTDI 100 c is calculated in the following way All calculations are done from the dose profile waveform Exposa m rade gn Cryg 20 SC 100 120 140 12 151 200 The waveform is an array of samples where the Z axis see graph above represents the position of the sensor and the y axis represents the exposure rate The waveform includes a maximum of 1024 samples Ocean 2014 finds key locations in the waveform in the following way 1 Find the maximum dose rate that occurred during the scan 2 Search backward from this point to find where the dose profile goes below 50 of the maximum value and call this position X1 not shown on graph 3 Search forward from the point found in step 1 to find where the dose profile goes below 50 of the maximum value and call this position X2 not shown on graph 4 Calculate the position halfway between X1 and X2 Call this point X3 shown as a solid red line in graph above 5 Calculate X3 50 mm and X3 50 mm and call these positions X4 and X5 respectively They are marked with red dotted lines in the graph above and labeled with the text 50 mm and 50 mm respectively If the points X1 and X2 can t be found automatically the analysis will show a calculation err
39. his mode makes it possible to define exactly how long you want to measure and by that being able to ensure that you don t miss any radiation You simply check on the CT scanner how long the scan will take and then use a certain margin of your choice in specifying measuring time To be able to collect the dose at the different positions thereby creating the dose profile the probe must be moved through the CT beam This is achieved by placing it free in air or in a phantom and then using the couch movement to scan the probe perform a helical scan Therefore it is not possible to use axial scans for measuring the CTDI with the CT Dose Profiler probe You could of course make many axial scans in small steps with the detector and plot a dose profile but that takes a lot of time With a helical scan you will receive the dose profile in a few seconds It has been proven that the CTDI can be measured with helical scans as long as corrections are made for the pitch see reference 10 This correction is done automatically in Ocean 2014 Make your first CTDI measurement We will use the measuring template that comes with Ocean 2014 in this first example As mentioned before it is assumed that you are familiar with Ocean 2014 If you need general information about Ocean 2014 please consult its User s Manual You can do the measurement in Quick Check or in Ocean 2014 s main mode If you use Quick Check just follow the instructions on the screen but read in
40. m graph not the analysis graph use the mouse pointer and grab the center pointer You can now move it Position it manually in the center of the dose profile Two new indicators for FWHM become visible Move these and position in a position where the dose rate is half of the maximum dose rate Now are all parameters in the analysis calculated based on the manual positions you have done If you want to go back to automatic calculation right click on the waveform graph and check Auto position center indicator 7 The calculated values are shown in the Analysis window Analysis Result Pass Set kV 120 kV Geometric efficiency 86 7 95 Beam width FWHM 27 7 mm CTDI 100 83 21 mGy n B Erneut m ra ncs B 8 The first measurement Geometric Efficiency is now done Other parameters measured with this template are the CTDI 100 free in air and the Beam width FWHM Full Width Half Maximum Unlisted CT scanners The scanners we currently have k factors for required for the method to measure CTDI with only one scan are listed in Appendix k factors Note that you can always specify the k factor after the measurement if you don t know it when you perform the measurement Add a user defined k factor later and specify it all calculations will be updated according to the new k factor you specify As described in section Make your first CTDI measurement you select the CT scanner by clicking on the binoculars on the Equipment tab
41. n of a new detector and software for measuring CT dose profile CTDI and CT tube current variation Evaluation of two thin CT dose profile detectors and a new way to perform QA in a CTDI head phantom You can download these papers and other application notes as a PDF file from our website at www rti se 2014 06 23 6 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2014 06 23 6 2A Index e Index A Analysis 30 Angualar dependence 48 Axial scan 50 B Beam width 35 Build CTDP templates 30 templates 35 Calculations CTDI 30 Center indicator 16 manual 24 Collimation 16 Columns 30 Connect 16 CT Dose Profiler 16 Connector 46 CT console 16 CT Dose Index 42 CT Dose Profile Analyzer 10 CT Dose Profiler probe 16 CT pahntom position 16 CT Phantom position 30 CT Phantom type 30 CT scanner model 16 select 16 CTDI 16 42 free in air 24 CTDI100 10 42 CTDIvol 10 16 CTDlw 10 42 CT SD16 10 D Dependence angular 48 energy 47 field size 49 2014 06 23 6 2A Detector Manager 10 DLP 10 16 42 Dose length product 42 Dose profile 16 a Energy correction 47 dependence 4 Examples 16 F Field size 49 Full Width Half Maximum 24 FWHM 10 24 35 G Generic scanner 26 Geometric efficiency 16 24 35 H Helical scan 50 K k factor 16 42 user defined 26 k factors 52 LU Layout template 30 35 Length 46 Macros 30 35 Manu
42. nalysis result STestResult Pass or fail text the overall result for the test SSetkV Set kVp SSetmAs Set mAs SSetPitch Set pitch SSetScanTime Set value for the scan time SSetTubeRotTime Set tube rotation time SSetCollimationMT Set value for the collimation SSetPhantomType Set value for phantom type 5can5peed Calculated scan speed Set Pitch Collimation NT Set Tube Rot Time SDoseProfileGraph The CT dose profile graph SCTDIc Measured CTDI 100 c center position from waveform SCTDIwn Measured value CTDI normalized SUnitwn Unit for CTDI normalized SMinCTDIwn Minimum value SMaxtCTDIwn Maximum value SCTDIw Measured value CTDI weighted SUnitw Unit for CTDI weighted SMinCTDIw Minimum value SMaxCTDIw Maximum value SCTDIvol Measured value CTDI volume SUnitvol Unit for CTDI volume SMinCTDIvol Minimum value SMaxCTDIvol Maximum value SDLP Measured value for Dose Length Product SUnitDLP Unit for Dose Length Product SMinDLP Minimum value SMaxDLP Maximum value SkFactor Used k factor if blank automatically selected by the analysis 2014 06 23 6 2A CT Dose Profiler User s Manual EUM Create your own templates Calculations The CTDI 100 c is calculated in the following way All calculations are done from the dose profile waveform im Exposite rade dnce mm STI EE ses 100 a 160 Zs rm The waveform is an array of samples where the Z axis s
43. nsure that the probe is not dislodged within the phantom when the couch starts to move 6 Start Ocean 2014 7 Go to the Library tab and open the Examples RTI gt Application gt CT folder If you can t find the examples please read the section Import CT Dose Profiler templates 8 Select the template CTDI CTDoseProfiler by double clicking on the name 2014 06 23 6 2A CT Dose Profiler User s Manual WR Start measuring Library O Real time display templates Examples RTI Applications CT gt I Session templates Real ti gt E Test ps Last modified Ge Type 4 Sc Real time display templates D bn e Inbox 2012 03 07 Template 4 4 Examples RTI 2012 03 07 Template 4 3 Applications 9 A hint is shown that briefly describes how to perform the measurement Click OK to close it you can reopen it by clicking on the hint icon The template is loaded and a new measurement is initiated Ocean 2014 will automatically connect to the meter at this point r MV Tase wes we cm Md Ocean Professional lo e x Measure Design Datalink Appearance Reporting Central database Help D el i o a Clear row o y V Getwaveforms N om me JAN Connect Reset Start Capture Pause Position Meter Exposure Favorites Bias off History Trend To do Update Ire v check info assistant l Close list inspection dates Edit Bias Compare Scheduling mr Ir mn
44. o the description in section Make your first CTDI measurement 2014 06 23 6 2A CT Dose Profiler User s Manual ER Start measuring Select Generic scanner 1 Select the Generic scanner 2 Edit the model field 3 Proceed according to the description in section Make your first CTDI measurement Use your own k factor The k factor is used by Ocean 2014 to calculate the weighted CTDI CTDI from only one measurement in the center hole of the phantom The k factor is calculated as CTDI GE D I 100 center If you know this factor for a certain CT scanner you can use it by building your own template and include the k factor column T Toshiba huvudfantom re Measurements E Library mm s s 12 00 1 090 co In 2 120 Head 12 1000 171 1 00 12 00 16 In 3 100 Body 12 1000 171 1 00 12 00 16 As soon as you enter a value in the k factor column this value is used for the calculation It will overrule any value available in Ocean 2014 s database CT Dose Profiler User s Manual 2014 06 23 6 2A Chapter 3 Create your own templates E N Create your own templates 3 Create your own templates The templates we have used so far have been the standard templates delivered with Ocean 2014 These templates are locked and cannot be modified you can only change existing set values but not the structure You can build your own templates real time display or test templates if you
45. or In this case in the waveform graph not the analysis graph use the mouse pointer and grab the center pointer You can now move it Position it manually in the center of the dose profile Two new indicators for FWHM become visible Move these and position in a position where the dose rate is half of the maximum dose rate Now are all parameters in the analysis calculated based on the manual positions you have done If you want to go back to automatic calculation right click on the waveform graph and check Auto position center indicator The central CTDI CTDI 100 c is calculated as CTDI100 Integrated dose between X4 and X5 Pitch Pitch must be specified in the grid FW HM is calculated as the distance between X1 and X2 BeamWidthFWHM X2 X1 Calculate Geometric efficiency in the z direction according to IEC 60601 2 44 as GeometricEfficiency 100 Dose between X6 and X7 Total dose Note The dose profile waveform is adjusted with the following function X FWHM for 3 mm X 40 mm CorrF 1 25466313 0 43935032 X 0 34546921 X 0 14128364 X 0 03057638 X 0 00330919 X 0 00014071 X For X 3 mm no valid correction available CT Dose Profiler User s Manual 2014 06 23 6 2A Create your own templates ER For X gt 40 mm CorrF 1 00 This means that the total dose indicated between cursors will differ from the dose value shown in the grid in the Exposure column when the FWHM
46. ot tell you if you measure on a thin dose profile with high dose rate or a broad dose profile with a low dose rate if they have the same dose area It can only measure a value that can foretell the dose but it cannot give a visible image of the dose profile The point dose detector can measure the same CTDI 9 in the center of the CT with helical scans as the pencil ion chamber can measure with axial scans On the central axis the dose is non oscillatory and the beam width is constant When measurements are performed in the peripheral holes the conditions are not the same any more The dose rate and the beam width in a peripheral hole oscillate during a rotation The dose rate oscillates due to varying x ray attenuation and beam divergence with changing distances affected by the inverse square law The beam width varies due to the divergence from the x ray source which becomes wider with increasing distance A single axial scan irradiates the same amount of dose to a detector with good rotation symmetry for every full 360 degree rotation it does not matter where the rotation starts and stops as long as it makes one whole rotation and it is very easy to get good reproducibility It is not the same for helical scans over a point dose detector because then you measure the point dose and not the dose length of for example 100 mm The beam divergence from the x ray source will have a big influence over the helical dose distribution among the peripheral hol
47. pecifies the scan speed value Measuring time This is the measuring time for TIMED MODE This is a meter setting a value used by the meter Tube rotation time This is the tube rotation time Set value CTDI free in air and Geomtetric Efficiency template The CTDI free in air helical scan analysis is used to evaluate the geometric efficiency CTDI free in air and beam width FWHM on computed tomography systems using the RTI CT Dose Profiler detector It uses one helical scan exposure and calculates the geometric efficiency The Geometric efficiency is simply speaking the guotient between the dose inside the collimation width NT and the total dose profile along the z axis expressed in percentage The exact definition can be seen in reference 13 The Geometric efficiency gives an indication of how good the collimation on the CT system is and how much of the radiation goes outside the detectors An example of measured Geometric efficiency is shown in the picture below The two dotted black lines represent the length of NT Ideally all the active detectors should receive the same amount of radiation and no radiation should be outside the detectors That would give a Geometric efficiency of 100 but that is probably not possible due to the penumbra etc A Geometric efficiency over 70 is good for a multi slice CT MSCT If you want to modify the standard analysis Ocean 2014 Professional is required see topic Modify analysis and Adv
48. perform this scan as you will need this value later on to select a suitable measuring time 17 You must enter the following parameters before you can perform your first measurement kV Pitch Tube rotation time s Collimation mm Phantom type head or body To be able to acquire DLP you also need to specify Scan length mm The scan speed is automatically calculated You now have to find the corresponding parameters on the CT console Parameters may have different names on units from different manufacturers 18 First select spiral helical scan on the CT scanner 19 Choose the correct Scan Field of View SFOV on the CT console The SFOV should be chosen according to the type of phantom that is used Select the phantom type in Ocean 2014 Here is an example of how a console may appear on a GE CT scanner when SFOV is selected CT Dose Profiler User s Manual 2014 06 23 6 2A Start measurin Delete Smart Preview Oplimize Gatin y Add ala a Biopsy g Group Seincted Prep HG Group Group Rx m Pabie Needed FEED enn ma Scan End Mo of Thick Interval Gantry T i SCH 3i Helical 5 0 z 1 41 Full 50 000 T200 000 41 55 00 3 000 30 0 Larg 120 500 1 9 0 4 sec 1 315 1 Y Select the desired SFOV Ped Ped Small Medium Large Head Bod Head Body Bod Cancel Select SFOV according to what kind of phantom you use SFOV type CTDI phantom
49. ported in Ocean 2014 There are a number of different quantities related to CTDI The most common are summarized in the table below Quantity Symbol Remarks Volume CTDI CTDlva As CTDlwbut corrected for pitch Dose length product DLP Takes the irradiated volume into bin M dean i The CTDI quantity can be interpreted as the radiation energy deposited in a slice with a thickness corresponding to the nominal beam collimation thickness The dose inside the slice is the CTDI and the dose outside the slice is excluded see figure below In single slice CT the expression for CTDI is defined as 1 Ka CTDI 2 D z dz where T is the nominal beam collimation thickness in mm and D z is the dose profile On the y axis the quantity is relative dose CTDI is acquired by reducing the integral to go between 50 and 50 For MSCT CTDI is defined as CIDI fix d Z dz N T 7 where N is the number of detectors and T is the width of a detector CTDI weighted represents an average value of the CTDI pg inside a phantom this requires five measurements one in each hole CT Dose Profiler User s Manual 2014 06 23 6 2A Theory 8 CTDI 1 CTDI 2 CTDI M 3 100 center 3 100 perpheral In the case of single slice CT the slice thickness is determined by the width of the detector In multislice CT MSCT the slice thickness is determined by the number of detectors and the widths of the detectors In
50. profile but that takes a lot of time With a helical scan you will receive the dose profile in a few seconds It has been proven that the dose profile can be measured with helical scans as long as corrections are made for the pitch see reference 10 Specifications Supported meters Barracuda with EMM 1Ch EMM 2Ch EMM Bias EMM BiasB and EMM BiasW with Ocean Piranha with external input with Ocean 2014 Typical cal factor 0 28 mGy nC Material Al and PMMA Connector Triaxial LEMO Length Detector extension 165 mm 45 mm Diameter 12 5 mm Sensor width 250 um Max sensitivity variation Less than 5 Weight Probe extension 40g 10g CT Dose Profiler User s Manual 2014 06 23 6 2A The CT Dose Profiler Probe ma 5 2 Energy correction When using the Piranha with Ocean 2014 and the CT Dose Profiler probe in the radiographic range all dose and rate values measured are automatically compensated for the energy dependence of the sensor The kV range is 55 150 kV and the total filtration ranges from 1 to 55 mm Al for measurements free in air and from 3 to 22 mm AI for measurements in head and body CT phantoms The reference point for all correction factors is at 120 kV with 2 5 mm Al filtration free in air calibration R3 RQR Energy correction factors free in air beam quality RQR Al mm 1 2 AS 3 5 7 10 13 15 19 22 25 29 34 38 44 55 55kv 1 30 115 107 102 091 086 082 081 079 077 077 078 078 0 77 amp 0kv
51. spiral CT there is an additional factor called the CT pitch factor It is defined as the table movement per gantry rotation Pitch E N T where Ad is the distance in mm that the couch moves between consecutive serial scans or per 3609 rotation in helical scanning N is the number of detectors and T is the detector thickness in mm IEC 2003 CTDI is the same as CTDI but with respect to the pitch factor in helical spiral scanning CTDL CTDI Pitch The displayed CTDL given by a manufacturer may be a representative figure for that model and not the value measured on the particular CT scanner see reference 13 The dose length product DLP includes the irradiated volume and represents the overall exposure for an examination and is calculated as following DLP CTDI L where L is the scan length of a certain examination The scan length is defined as L R p N T where R is the number of tube rotations p is the pitch factor N is the number of detectors and T is the detector thickness The effective dose to a region is defined as E Ep DLP where DLP mGycm is defined in equation 6 and Epp is the region specific DLP normalized effective dose mSv mGycm A quicker way to perform quality assurance has been introduced by using the CT Dose Profiler probe and the Ocean 2014 software To be able to use it the k factor must be known for the CT unit and the type of phantom that is used for the measurement A number o
52. ss fail analysis is performed for that item When you modify a CTDI in phantom helical scan analysis Ocean 2014 Professional is required all pass fail criteria are available Hin Max F Use CTDI 100 w limit mGy E Use CTDI 100 w n limit mGy mAs Use CTDI 100 vol limit mGy Use DLP limit mGycm You must modify the layout to see the results of the additional parameters Result layout and macros As described in the topic Advanced analysis in the Ocean 2014 Reference Manual or Help text it is possible to modify the the layout of the analysis result Ocean 2014 Professional is required The layout is 2014 06 23 6 2A CT Dose Profiler User s Manual EM Create your own templates defined as text combined with macros When the analysis result is shown the macros are replaced with the appropriate calculated values set values and measured values The default layout for the CTDI in phantom helical scan analysis looks like this Title Result STestResult Set kV 5etkV kV CTDI 100 c SCTDIc SUnitw CTDl w SCTDlw SUnitw CTDIvol SCTDlIvol SUnitvol DLP SDLP UntDLP SDoseProfileGraph This text can be modified and more macros can be added to show more calculated results for example the relative difference The following macros are available for the CTDI in phantom helical scan analysis CT Dose Profiler User s Manual 2014 06 23 6 2A Create your own templates E N Title Specified title SResult A
53. the CTDP probe in the center hole of the phantom head or body The CT Dose Profiler replaces the conventional TLD and OSL methods or film for dose profile measurements The CT Dose Profiler probe is designed to be used with the Piranha X ray multimeter and a PC running the Ocean 2014 software You can measure several different parameters with Ocean 2014 and the CTDP probe There are two standard templates one for CTDI and one for geometric efficiency that come with Ocean 2014 which can be used with all license levels As mentioned above the CTDI measurement can be done with one helical scan After the helical scan Ocean 2014 gives several parameters at the same time such as CT dose profile CTDI gog CTDI CTDI oy DLP and FWHM The scientific methods used in the CT Dose Profiler have been evaluated in a variety of studies see the reference list especialy 1 4 10 11 12 14 15 and 16 Note This manual will show you how to use the CT Dose Profiler probe with a Piranha and the Ocean 2014 software It will also give examples of practical measuring methods It is assumed that you have installed Ocean 2014 and are familiar it If you haven t instaled Ocean 2014 yet do that first You will find instructions in the Ocean 2014 User s Manual AN The CT Dose Profiler shall be handled with care even if it is much more durable than a traditional CT ion chamber If it is dropped or subjected to strong shocks the detector chip may be damaged
54. tor name CD Model m Serial E Waveform type HF DC tu Note 1 a CO TI Note 2 Note 3 Note 4 jua udinb3 Generator ID E Indude in reports aha 12 Now select the CT scanner model Click on the binoculars to see the CT scanner list for the specified manufacturer If you don t find your CT scanner in the list select the Generic scanner You can also read more in the section Unlisted CT scanners Select generator model Aquilion 16 BO 100 120 135 kV i Aquilion Multi 4 BO 100 120 135 kv i Asteion 120 130 kV Asteion Dual 120 135 kV Asteion Multi CXB 400C tube 80 100 120 135kv Asteion Multi older tube 80 100 120 135 kV Auklet 120 kV bs Generaic scanner 120 kV Toshiba TCT 600 120 kV i Xpress GX Post 98 Asteion 120 130 kV Xpress GX Pre 98 120 kV be Xpress HS 120 kV i Xpress HS1 120 kV i Xspeed II 120 kV i Xvision EX 120 kV 13 Select CT scanner model and click OK Note also that for each model the possible kV settings are also listed If you can t find the CT scanner you are looking for read the section Unlisted CT scanners For the purpose of following this example select one that is similar to the one you have When you select the CT scanner model the required data will be pulled into your measurement from a database including energy correction factors and the k factor You can read more about the k f
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