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1. 2 Select the template Geometric Efficiency CTDoseProfiler by double clicking on the name CT Dose Profiler User s Manual 2012 10 25 5 2A Start measuring 25 I Mo measurement loaded a Measurements 2 Library G Real time display templates b Examples RTI k Applications CT gt EB Session templates Real time displav gt Fest en Name Last modified Type a D Real time display templates e LTDL cris afile 2012 03 07 Template b Inbox um 4 19 Examples RTI l Geometric k n CTDoseProfiler 2012 03 07 Template i a D Applications 3 Load the template e 1 000 a 2 120 12 1 000 Ea a 15 lim 3 120 12 1 000 1 00 12 00 5 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 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 T 1 000 24 00 2 120 12 1 000 pe 12 00 15 la 3 170 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
2. Web site http wwrti 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 Int 1 973 439 0248 E mail Sales sales rtielectronics com Support support rtielectronics com Service service rtielectronics com Web site htto wwurtielectronics com 2012 10 25 5 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 relevant documentation
3. 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 2012 10 25 5 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2012 10 25 5 2A Contents 7 Table of Contents 1 INtFOQUGHOM ii ii avi ka a tp a n ki anv E 10 TA Users ofthe old SOMWANC sas uu ul u pan uu bean ik e pann ease ken apse pe ao ane 10 1 2 Import CT Dose Profiler Templates nanna 12 19 Fielpun OO CCAM ki u u Aa 14 S CANE ME eS urih O ese ses date x pa ata ua rear 16 2 1 Make your first CTDI measurement J I 16 2 2 Measurement free in air L cccccceccececeeeceeseeeeeeseneceesenaceeseeaceeseneeeseneeseesateeeenaees 24 2 3 Unlisted CT scanners vr sus in ta dy tal patat seid to ta dl l an e a bk tn a poo mase 26 Create your own templates 30 3 1 CTDI template in phantom nn 30 3 2 CTDI free in air and Geomtetric Efficiency template 35 WIN OY ai uu ka et Ga a a a e tk L al 42 4t GND AN KT ACCOM u ea ko na kota n ka e ak ao ab a ok a Soon kk 42 4 2 Why use a k factor n 44 The CT Dose
4. Waveform data EJ s CTDI 100 c N A Exposure rate si Beam width FWHM N A ime s Te N A 0 3 0 I Between cursors 80 1 I Dose 83 21 mGy i CTDI 83 21 mGy 70 Time 4399 ms s Length 105 6 mm 60 I oo I 50 w LI w 40 T 5 i ow 3 30 gt I LU I 20 LI I 10 i s 0 0 20 40 60 80 100 120 140 Z axis mm 2012 10 25 5 2A CT Dose Profiler User s Manual 2 Start measuring There are two cursors that can be moved Corresponding cursor values are shown in the waveform data window 7 The calculated values are shown in the Analysis window Result Pass Set kV Geometric efficiency Beam width FWHM CTDI 100 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 2 3 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 As described in section Make your first CTDI measurement you select the CT scanner by clicking on the binoculars on the Equipment tab after specifying the manufacturer name Equipment Generator Manufacturer Generator name Model Serial Waveform type Note 1 Note 2 Note 3 Note 4 Generator ID ial vaje When you click on the binoculars the available scanners for selected manufacturer are shown
5. 1 7 at 120 kV Why use a k factor To measure the CTDI oo 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 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 not tell you if you measure on a thin dose profile with high dose rate ora 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 p in the center of the CT with helical scans as the pencil ion chamber can measure with a
6. 120 kV 86 7 Yo 21 1 mm 63 21 mGy HF DC Indude in reports CT Dose Profiler User s Manual jus wd inby JALI EYWE la m 2012 10 25 5 2A Start measuring K A Select generator model i Aquilion 16 80 100 120 135 kV Aquilion Multi 4 80 100 120 135 kV Asteion 120 130 kV 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 Toshiba TCT 600 120 kv i Xpress GX Post 98 Asteion 120 130 kV fe Xpress GX Pre 98 120 kV i Xpress HS 120 kV be Xpress HS1 120 kV i speed IT 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 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 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 to the description in section Make your first CTDI measurement Use your own k factor The k factor is used by Ocean to calculate the weighted CTDI CTDI from only one measurement in the center hole of the phantom The k factor is calculated as CTDI CE D I 100 center If you know this factor for a certain CT scann
7. CTDI 42 W Waveform 16 Weight 46 Weighted CTDI 42 2012 10 25 5 2A
8. Dose Profiler User s Manual Toshiba Aauilion 16 80 1 147 2 206 Toshiba lAquilion 16 1 070 1 959 Toshiba _ _ Aquilion 16 1 056 1 779 Toshiba Aauilion 16 1 051 1 728 CT Dose Profiler User s Manual 2012 10 25 5 2A Chapter 7 References 58 References 7 References li 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 dose profile CTDI and CT tube variations Poster Can be downloaded from http www rti se in 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 G teborg University Goteborg Sweden 2004 Nagel H D Radiation Exposure in Computed Tomography Fundamentals Influencing parameters Dose Assessment Optimisation Scanner Data Terminology qth 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 mh hannover de International St
9. Note This manual will show you how to use the CT Dose Profiler probe with a Piranha or Barracuda and the Ocean software It will also give examples of practical measuring methods It is assumed that you have installed Ocean and are familiar it If you haven t installed Ocean yet do that first You will find instructions in the Ocean User s Manual 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 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 will not work with Ocean 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 for the first time with the CT Dose Profiler probe and you use Piranha Ocean may show a message that your probe needs to be reprogrammed CT Dose Profiler User s Manual 2012 10 25 5 2A Introduction HELEN Your meter s CT Dose Profiler probe is not compatible 7 with Ocean 1 Quit Ocean 2 Start the RTI Detector Manager If you don t have it installed you 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 LTDP correction 5 Wait while the probe t fixed 6
10. Profiler Probe 46 5 PECHE ANONS uuu ee it tie e ee ta 46 52 IEMEFOV EOMEOGU OI pey uu i enemas eee 47 5 93 Angular dependence ii sat LU eee 48 Did IROLAHOM SVIMIMO UY kou saa uuu uz uuu tin EAR ke oke kk ia oak a aks pasan sss 49 5 5 Field size dependence nanna nanna 49 5 6 Axial sequential scans vs helical SCANS sa 50 ADDSPIQIKCu u iu l a u uuu e oo te a ie de 52 GE KRAG ON SA u uuu cece e tr nes yan tay a a a tan ou ese sa at 52 Ferer eri c6sS uu n uuu ai ni kte kl kk a a ak r 58 III YO ik eat tk akt a e t a at veda a a a a a na e kt a a e kaa a Eta ak 61 2012 10 25 5 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2012 10 25 5 2A Chapter 1 Introduction KI 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 standar
11. 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 old software again Next time you use Ocean again and Ocean complains again and asks you to correct the probe you can follow the above procedure 1 2 Import CT Dose Profiler Templates If your latest full installation of Ocean was done before before October 2012 you may not find the examples this manual refers to or not the latest version To import the examples for the CT Dose Profiler probe follow the procedures below 1 Go to the Help tab on the ribbon bar and select Import examples Measure Design Data link Appearance Reporting Central database Help FO 2 intact Activate Check Trial About Import Backup RTI meter update Suppart I Database FT Tableof FAQ Getting Measure Design Misc contents started v Help Tutorials Import examples CT Dose Profiler User s Manual 2012 10 25 5 2A Introduction KEN 2 When you click on the button the Start wizard will open Click next until you come to the Examples page Ocean startup wizard Welcome Examples Units 4 Piranha Spreadsheet program A number of example templates are available to help I you get started with Ocean By selecting meters Examples modalities and parameters in the list to the right you Finish will get examples suitable for your needs and that corresponds to the capa
12. 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 10 r IT j ji l TT I 8 oe Wi 0 7 e EN n 7 a s j s j a 4 ao j jJ _ oe L monwa 1 Lo pp co 0 Z axis mm 30 The calculated values are shown in the Analysis window 2012 10 25 5 2A CT Dose Profiler User s Manual PPH Start measuring Analysis Result Pass Set kV 80 kV CTDI 100 c 26 52 mGy CTDI w 30 28 mGy 1 CTDIvol 30 28 mGy 1 DLP 517 8 mGycm E pasi e rat 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 is for measurements free in air This template calculates CT DI 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
13. dependence free in air 4 Field cm No correction is needed in a phantom due to the large amount of scattering material 2012 10 25 5 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 os scan ire v T L a i a w ik v 300 200 1 0 100 200 300 z axis mm CT Dose Profiler User s Manual 2012 10 25 5 2A Chapter 6 Appendix 52 Appendix 6 Appendix 6 1 k factors The table below shows the k factors Ocean uses There is one factor for head and body respectively The k factors are based on data from impactctscan org Manufacturer Name kVp Head Body Elscint Exel2400Hlectt 140 1430 GE High 000 I 8 1047 1 600 GEJ HiSpeedClinoSmariBeam 80 1047 1600 GE IHiSpeed CT i with SmartBeam _ 80 1047 2 093 GE Pae 80 1162 2164 GE sec oo 80 1162 2164 GE y O 80 1145 2213 GE eT 80 1 145 2213 GE QR 0202 80 102 1 927 GE _ siLightSpeed 8 1 032 1 927 GEJ ILigh
14. for this analysis Set value CT phantom position This specifies where the CT chamber is positioned in the phantom not Set value required 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 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 CT DI free in air and Geomtetric Efficiency template The CTDI free in air helical scan analysis is used to evaluate the geometric efficiency CT DI 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 quotient 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 ac
15. 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 S CTDI D z dz T o0 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 oo is acquired by reducing the integral to go between 50 and 50 For MSCT CTDI is defined as I3 Em E va D z dz where N is the number of detectors and T is the width of a detector CTDI weighted represents an average value of the CTDI 9 inside a phantom this requires five CT Dose Profiler User s Manual 2012 10 25 5 2A Theory 43 measurements one in each hole l CIDI Fi 5 ki DI ia T a I l TRA 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 spiral CT there is an additional factor called the CT pitch factor It is defined as the table movement per gantry rotation Pitch EA N T where Ad is the distance in mm that the couch moves between consecutive serial scans or per 360 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
16. level vou are running vou have different possibilities Displav You can only use the measuring templates that come with Ocean These templates are locked and you cannot modifv the structure However vou 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 Connect Same as for Display Professional You can use the templates that come with Ocean 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 c
17. not dislodged within the phantom when the couch starts to move 6 Start Ocean 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 2012 10 25 5 2A CT Dose Profiler User s Manual KEN Start measuring 8 Select the template CTDI CTDoseProfiler by double clicking on the name gt JE Session templates Name Last modi fied Type CTDI CTDoseProfiler 2012 03 07 Template Geometric EMmaency 2012 03 07 Template gt i Test templates a D Real time display templates b amp Inbox a a Examples RTI 4 79 Applications DoseProfiler 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 will automatically connect to the meter at this point G ane youn teat CTDI Press wes Untitled Ocean Professional rr Measure Design Datalink Appearance Reporting Central database Help 2 u e Clear row 6 TI Get waveforms AN n PO i A ab j ETN ia 2 p img a l s Clear all na pee Connect Reset Start Capture Pause Position Meter Exposure Detector Favorites Bias off History Trend To do Update g check info assistant L Close list inspection d
18. only one helical scan with the probe in the center hole of the phantom used in Ocean 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 pou CTDI 1 CTDI 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 uses one helical scan exposure with the CTDP in the center hole of a 5 hole phantom and calculates the CTDI CTDI OI 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 as the k factor A list of k factors Ocean uses is available in the Appendix Use the binoculars to select a scanner from the list Ocean will choose the correct k factor based the CT scanner name you selected Equipment Jn T DUO E Select equipment E T ye e Generator Tube Manufacturer siemens or Generator name Siemens Somatom Plus 4 x Model z Serial 78978978 a a A ri Waveform type HF DC f Note 1 HE If you want to modify the standard analysis Ocean Professional is required see topic Modify analysis and Advanced analysis in the Oc
19. 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 po 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 2012 10 25 5 2A Chapter 5 The CT Dose Profiler Probe 5 5 1 r The CT Dose Profiler Probe 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 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 t
20. the pitch factor in helical spiral scanning CTDI CTDI Pitch The displayed CTDI i 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 NT 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 E DLP where DLP mGycm is defined in equation 6 and Ep p 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 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 of 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 CTDI go central from measurements obtained with pencil ion chambers _ CTDI C TDI 100 center 2012 10 25 5 2A CT Dose Profiler User s Manual 4 2 TW Theory For head phantoms the k factor is around 1 and for body phantom the k factor is around
21. 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 factor 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 2012 10 25 5 2A CT Dose Profiler User s Manual MET Start measuring 15 First perform a topogram scout image over the whole CT Dose Profiler when it is positioned inside the phantom Ocean is not used at this stage and the meter will not record any data You do not have to be concerned with anv 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 approximatelv 3 cm b
22. 0 102 105 108 110 112 1 17 1 19 1 24 1 33 120kv 1L05 1 02 100 0 98 096 098 101 104 106 110 114 117 1 19 1 24 1 27 13 1 45 130kv 1L04 102 101 0 99 O99 101 105 109 111 115 120 12 126 1 31 135 143 1 56 140 kv 104 103 102 100 101 104 109 1 13 116 121 126 130 1 33 1 39 145 152 1 67 150kv 107 104 102 101 104 107 114 119 1 21 1 27 133 138 142 147 156 162 1 76 Energy correction factors for Head Phantom beam quality ROR Al mm 3 5 7 10 13 19 22 55 kW 086 O88 088 089 091 082 0 94 60kV 087 O88 089 090 0 92 O93 0 35 7okv O88 0 89 0 90 0 91 0 93 O95 0 97 sokv 0 90 091 092 033 095 098 1 00 sokv 091 0 93 0 94 095 O97 101 1 03 100kv 0 93 094 0 96 097 1 00 1 04 1 06 110kv 0 85 097 0 98 100 1 03 1 07 1 10 120kv 0 97 0 99 100 103 1 06 1 11 1 13 130kv 1 00 101 103 106 1 09 115 1 17 140 kv 1 02 1 04 106 109 112 1 19 1 22 F 150 kv 1 05 1 07 108 1 13 116 1 24 1 26 2012 10 25 5 2A CT Dose Profiler User s Manual 48 The CT Dose Profiler Probe Energy correction factors for Body Phantom beam quality RQR Al mm 3 5 7 10 13 19 22 55 kv 60 kV 70 kV 80 kV 90 kw 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 8
23. 9 0 90 0 92 0 94 0 36 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 Normalized to 0 degrees 50 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 10 Degrees 20 30 40 50 2012 10 25 5 2A The CT Dose Profiler Probe 49 9 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 a ee JI 0 045 Doserate mGy s l I 10 12 Time s 14 16 18 20 5 the output from the tube was going down slightly during the long exposure Typical deviation for the CT Dose Profiler probe is about 1 90 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 lt 4 cm and down to 3 mm the calibration factor is no longer accurate and must be corrected see picture below This is automatically done in Ocean when you measure free in air and the FWHM lower then 4 cm 1 2 0 8 0 6 Nomalized to 4cm 0 4 0 2 Field size
24. CT Dose Profiler Probe for evaluation of CT systems CT Dose Profiler User s Manual English Version 5 2A RTI article number 9630512 00 CT Dose Profiler User s Manual 2012 10 25 5 2A CT Dose Profiler The CT Dose Profiler probe makes it possible to evaluate the performance of modern CT scanners VU RT 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 2012 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 and Vista 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 446 31 463600 E mail Sales sales rti se Support support rti se Service service rti se
25. Hel 5 0 1 41 Full 30 000 T200 000 di 55 00 1 375 Helical 5 000 1 9 0 4 sec 1 pady Select the desired SFOV Ped Ped Small Medium Large Head Bod Head one Body Bod SATE Taa Select SFOV according to what kind of phantom you use SFOV type CTDI phantom Ped Head Ped Body 16 cm Phantom Smal Head Head 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 MA HEER pen m 2 0 sec Helical Thickness mm 0 625 1 25 as Coverage Speed 3 75 50 20 62 mmisec Pitch amp Speed mm rot 0 884 1 1 375 1 39 37 55 00 Rotation Time sec 0 516 1 20 62 OK Cancel 2012 10 25 5 2A CT Dose Profiler User s Manual 2 Start measuring 20 Select the kV at which you want to do the measurement and enter it into Ocean 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 22 Select the tube rotation time and enter it into Ocean 23 Select Collimation and enter it into Ocean Ocean 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 25 If you want DLP enter the scan length into Ocean 26 Make sure
26. Quit the Detector Manager i 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 probe connected 2 The Detector Manager will show the probe and its type is PiranhaCT DP i RTI Detector Manager RTI Internal mode Main Detector Calibration Maintenance Help F Add Detector Remove Detector Detector Store to Device Calibration TV 1 f B R3 ROR W 2 5 mm AN 3 Double click on the probe and the following pop up window is shown Edit Detector ype PiranhaCTDP 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 2012 10 25 5 2A CT Dose Profiler User s Manual MPA Introduction Edit Detector Tvpe 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 i ETI Detector Manager ETI Internal mode Main Detector Calibration Maintenance Help Store to Device t Add Detector Detector a Calibration CT Dose Piranha Profil MF2 17020 7
27. Time 5DoseProfileGraph The CT dose profile graph SCTDIc Measured CTDI 100 c center position from waveform SCTDlwn Measured value CTDI normalized SUnitwn Unit for CTDI normalized 5MinCTDlwn Minimum value SMaxCTDlwn Maximum value SCTDIw Measured value CTDI weighted Unitw Unit for CTDI weighted SMinCTDIw Minimum value SMaxCTDIw Maximum value SCTDIvol Measured value CTDI volume SUnitvol Unit for CTDI volume SMinCTDIvol Minimum value SMaxCTDlvol Maximum value SDLP Measured value for Dose Length Product SUnitDLP Unit for Dose Length Product SMinDLP Minimum value SMaxDLP Maximum value 5kFactor Used k factor if blank automatically selected by the analysis 2012 10 25 5 2A CT Dose Profiler User s Manual FE Create your own templates Calculations The CTDI 100 c is calculated in the following way All calculations are done from the dose profile waveform Exposite rat mG 100 40 150 10 Zs nn 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 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 Searc
28. an 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 This 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 Make your first CTDI measurement We will use the measuring template that comes with Ocean in this first example As mentioned before it is assumed that you are familiar with Ocean If you need general infor
29. andard 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 in 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 Goteborg University Goteborg Sweden 2008 Vrieze T Bauhs J McCollogh C Use of spiral scan acquisition for CT dose measurements Selection of optical pitch values to ensure reproducible results LL PH6115 B05 RSNA 2007 abstract Herrnsdorf L Bjork 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 Mo lndal Sweden and Mid Sweden University Sundsvall Sweden Science Direct do 10 1016 j mma 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 2012 10 25 5 2A References EX 14 Perisinakis K Papadakis A E Damilakis J The effect of x ray beam quality and ge
30. asurement 29 As soon the measurement is completed Ocean 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 2012 10 25 5 2A Start measuring 2 Toshiba huvudfantom IT Measurements Riy kv mm mm s mm s s AMOY In gt ee Head 12 l 171 i 00 16 30 04 ia 2 120 Head 12 1 000 171 1 00 12 00 16 io 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 mGv Beam width FWHM N A 16 Geometric efficiency N A L A Exposure rate Time s 1 1 ki ku 10 Between cursors Dose 27 82 mGy 9 CTDI 27 82 mGy 8 Time 9751 ms w Length 117 0 mm B T oO Eg wo Es a 4 o a 3 2 1 0 iim 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 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
31. ates Meter Edit Measure Bias Compare Scheduling EE Measurements Library i Untitled e kv mm mm s mm s s mGy la gt aie 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 dQ12 eyUesid aa quawdinb3 The dose profile is shown here a y Waveform data is shown n Calculated values are shown zan CT Dose Profiler User s Manual Waveform Waveform data P Analysis TE a Show hide Cursorl Cursor2 Die CTDI 1 spiral scan in phantom Exposure 1 18 T i Ai Time Set kV 100 0 kv CTDI 100 c mGy fel CTDI w mGy 124 t l l l 1 Between cursors CTDIvol mGy 10 Exposure DLP mGycm 927 l l Exposure rate es Waveform not available of oz CTDI 2 spiral scan in phantom 5 T T T se 92 BA 96 se bas 102 104 106 102 11 0 A alvsis Comment Real time display amp Piranha E Log mode EA 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 ty
32. bility of your meter and your detectors probes The example templates will be copied to a folder called Examples RTI found in the main folder for each template type Itis recommended that you don t use the Examples RTI folder to store your own templates since future i updates of Ocean may use this folder mA mAs AJ CT dose Barracuda ff Radiography Pulsed fluoroscopy Mammography 3 Select CT and CT Dose as shown in the picture note that this works also if you use Barracuda 4 Click Next 5 The new real time templates are added to the RTI Example gt Applications gt CT folder T CTDI CTDoseProfiler 7 Geometric Efficiency CTDoseProfiler These templates can be used with all license levels of Ocean Display Connect and Professional The template structures are locked but the set values and parameters can be changed If you have Ocean Professional you can modify these templates in any way you want If you use Display or Connect you can t modify the structure of the templates only change set values There is one additional template for CTDI in the User def k factor folder This template is the same as CTDI CTDoseProfiler but allows you to specify your own k factor This template can be used in case you don t find your scanner in Ocean s list and you know the k factor To create your own templates for the CT Dose Profiler probe and calculate CTDI and Geometric Efficiency you must
33. canS5peed Calculated scan speed Set Pitch Collimation NT Set Tube Rot Time DoseProfileGraph The CT dose profile graph SCTDILO0 Measured CTDILOO UnitCTDILOO Unit for CTDI SBeamWidthFWHM Beam width from waveform SMinBeamWidthFWHM Minimum value SMaxBeamWidthFWHM Maximum value GeometricEfficiency Geometric efficiency from waveform MinGeometricEfficiency Minimum value SMaxGeometricEfficiency Maximum value 2012 10 25 5 2A CT Dose Profiler User s Manual 3 Create your own templates Calculations The CTDI 100 c is calculated in the following way All calculations are done from the dose profile waveform Expos e rat gn Gys 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 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 an
34. d 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 The central CTDI CTDI 100 c is calculated as CTDI100 Integrated dose between X4 and X5 Pitch Pitch must be specified in the grid FWHM 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 lt X lt 40 mm CorrF 1 25466313 0 43935032 X 40 34546921 X 0 14128364 X 0 03057638 X 0 00330919 X 0 00014071 X For X lt 3 mm no valid correction available 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 is less than 40 mm CT Dose Profiler User s Manual 2012 10 25 5 2A Create your own templates rL Recommended columns or general settings The following columns are recommended for the CTDI free in air helical scan analysis ke The measured dose from the CT Dose Profiler detector Set sd kV The set value for kV CT Phantom type The phantom type specifies head or body for this analysis not required Set value Collima
35. d 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 CTDP 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 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 Barracuda or Piranha X ray multimeter and a PC running the Ocean software You can measure several different parameters with Ocean and the CTDP probe There are two standard templates one for CTDI and one for geometric efficiency that come with Ocean 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 gives several parameters at the same time such as CT dose profile CTDI oo CT DI CT DI op DLP and FWHM The scientific methods used in the CT Dose Profiler have been evaluated in a variety of studies see the reference list especially 1 4 10 11 12 14 15 and 16
36. ean 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 2012 10 25 5 2A Create your own templates 31 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 CIDI 1 spiral scan in phantom Result Pass set kV BU kV CTDI 100 c 26 52 mGy CTDI w 30 28 mGy CTDIvol 30 28 mGy DLP 517 86 mGycm Epose rat mos 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 pass fail analysis is performed for that item When you modify a CTDI in phantom helical scan analysis Ocean Professional is required all pass fail criteria are available Min Max MI Use CTDI 100 w limit mGy E Use CTDI 100 w n limit mGy mAs Use CTDI 100 vol limit mGy C Use DLP limit mGyem You must modify the layout to see the results of the additional parameters Res
37. efore the phantom and the end cursor approximatelv 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 perform this scan as vou 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 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 2012 10 25 5 2A Start measurin Split Delete Smart Preview W Optimize Gatin 4 Add n Biopsy g Group Current Seineted Rix Frep ji i Group Group Rx n abit Needed FEE 0 0 ka 120 500 aes Scan Start End Ho of Thick Interval a Type Location Location Images Speed mm
38. er you can use it by building your own template and include the k factor column IY Toshiba huvudfantom IEP Measurements GP Library View f Select CT phantom type Collimation Tube rotation time Measuring time Exposure k aa Ti s ii s mGy Head 1 000 171 1 00 12 00 16 30 04 1 090 J K 1 090 J 090 A a 2 120 Head In 3 100 Body 1 000 171 1 00 12 00 16 1 000 171 1 00 12 00 16 sis Es 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 s database 2012 10 25 5 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2012 10 25 5 2A Chapter 3 Create your own templates 3 3 1 HET Create your own templates Create your own templates The templates we have used so far have been the standard templates delivered with Ocean 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 have Ocean Professional Ocean s helptext and User s Manual give a general description of how to create a template The next two topics give specific information about required columns calculations and other information required to measure CTDI and Geometric Efficiency using the CT Dose Profiler and Ocean CT DI template in phantom The theory behind the method of
39. h 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 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 SCTDIw 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 2012 10 25 5 2A Create your own templates 35 3 2 Recommended columns or general settings The folowing columns are recommended for the CTDI in phantom helical scan analysis Parameter 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
40. have Ocean Professional To use it as a point dose detector and to measure just dose is possible with all license levels of ocean For users of Ocean Professional If you use Professional you will also find test templates in the RTI Example gt CT folder under test templates These templates can be included in your sessions You can also create your own templates Read more about this in the section Create your own templates 2012 10 25 5 2A CT Dose Profiler User s Manual OI ITITS Introduction 1 3 Help in Ocean The manual for the CT Dose Profiler is available as a help tutorial in Ocean Go to the Help page on the ribbon bar Data link Appearance or ting Central database Help e ee Q w g Table of FAQ Getting Measure Design Import Contact Activate Cl contents started Y Y examples RTI meter up Help Tutorials Tr l r Your first CTDI measurement gay Keyboard ER Measurements gt Library 17 No measure Design your own templates Theory of CTDI and k factor Click on the CTDP tutorial button and select what you want to read about CT Dose Profiler User s Manual 2012 10 25 5 2A Chapter 2 Start measuring 2 2 1 KON Start measuring Start measuring The Ocean software is used to evaluate and calculate all parameters based on the measured dose profile Ocean is available in three different license levels Displav Connect and Professional Depending on the
41. he 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 called 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 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 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 Piranha with external input Typical cal factor 0 28
42. iler 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 CTDIlvol 10 16 CIDIW 10 42 CT SD16 10 D Dependence angular 48 energy 47 field size 49 2012 10 25 5 2A Detector Manager 10 Display 16 DLP 10 16 42 Dose length product 42 Dose profile 16 E Energy correction 47 dependence 47 Examples 16 Field size 49 Full Width Half Maximum 24 FWHM 10 24 35 Geometric efficiency 16 24 35 Helical scan 50 Import CIDP templates 12 K k factor 16 42 k factors 52 L Layout template 30 35 Length 46 Macros 30 35 Measuring time 16 30 N NT 35 42 CT Dose Profiler User s Manual O Ocean Connect 16 Display 16 Prodfessional 16 templates 10 Ocean Professional 12 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 R3 47 Rotation symmetry 49 RQR 47 ats 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 SFOV 16 CT Dose Profiler User s Manual CCI Index sT Templates 10 import 12 locked 12 Timed mode 46 Tube filtration 16 Tube rotation time 30 35 Volume
43. mGy nC Material Al and PMMA Connector T riaxial 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 2012 10 25 5 2A The CT Dose Profiler Probe Ka 5 2 Energy correction When using the Piranha or Barracuda with Ocean 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 Al 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 ROR Al mm i 2 2 5 3 5 7 10 13 15 19 22 25 29 34 38 44 55 55k 130 115 107 102 0 91 O86 082 O81 O79 O77 O77 0 78 0 78 O77 60k 125 1 11 104 099 089 O85 O87 081 O80 0 79 O75 0 79 0 79 0 79 079 080 082 7OkV 118 106 1 00 0 96 O88 O85 O84 O83 083 O83 O84 084 084 085 O86 087 0 89 sokv 1 13 1 03 0 98 0 95 O88 087 087 087 087 O88 090 091 091 0 93 094 096 0 98 90kV il 102 097 095 0 90 089 0 90 O91 0 92 O93 O96 O97 098 1 01 103 1 05 1 09 100 kv 1 09 101 0 98 0 95 092 0 92 094 0 96 097 099 102 104 105 1 09 111 1 14 1 21 110kv 1 07 101 0 99 096 094 O95 O97 10
44. mation about Ocean please consult its User s Manual CT Dose Profiler User s Manual 2012 10 25 5 2A Start measuring Ka Assume that you want to measure CTDI 100 using a head phantom First setup the meter phantom and probe 1 Connect the CTDP probe to the Piranha Barracuda 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 a 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 4 Make sure that the two horizontal CT lasers are visible on the probe approximately in the middle of tt 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 ensure that the probe is
45. ometry 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 evaluation of a new detector and software for measuring CT dose profile CT DI 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 2012 10 25 5 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2012 10 25 5 2A Index 61 Index Analysis 30 Angualar dependence 48 Applications 12 Axialscan 50 B Beam width 35 Build CTDP templates 30 templates 35 Calculations CTDI 30 Center indicator 16 Collimation 16 Columns 30 Connect 16 CT Dose Profiler 16 Connector 46 CT console 16 CT Dose Index 42 CT Dose Profile Analyzer CT Dose Prof
46. pe if you want 10 The first thing you should do is to select CT scanner in Ocean Go to the Equipment tab 11 Specify the CT scanner manufacturer 2012 10 25 5 2A Start measuring IKTU Equipment P gt Generator Manufacturer ki Cy Generator name w Model w jus wdinb3 Serial 1 Waveform type HF DC m E I a Note 1 a TI Note 2 Note 3 Note 4 Generator ID Include in reports ialveia 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 one of the same brand and similar model You can also read more in the section Unlisted CT scanners Select generator model Aquilion 16 80 100 120 135 kV i Aquilion Multi 4 80 100 120 135 kV i Asteion 120 130 kv i Asteion Dual 120 135 kV l Asteion Multi CXB 400C tube 80 100 120 135 kV i Asteion Multi older tube 80 100 120 135 kw i Auklet 120 kV i Toshiba TCT 600 120 kV i Xpress GX Post 98 Asteion 120 130 kV l Xpress GX Pre 38 120 kV press HS 120 kV Xpress HS1 120 kV i Kspeed 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
47. r Picker Ultraz 8 1 076 3328 l Philips JPhilips Marconi Mx8000 90 1096 1888 l Marconi Marconi m8000 pe 71096 1888 l Marconi Marconi Mx8000 140 1653 Shimadzu ShimadzuscT 80 1434 2470 Siemens Siemens DRG 425 Siemens SiemensDRG1 15 Siemens Somatom Plus4Series 80 1100 2047 l Siemens Siemens Volume Zoom 80 1 201 2135 1 CT Dose Profiler User s Manual 2012 10 25 5 2A Appendix W IIIS Siemens jaces CL 8 121 2435 l Siemens EmotionDuo peso 1108 1951 l Siemens Sensation4 peso 1156 1939 l Siemens Sensation4 140 1602 Siemens __ Sensation16 8 144 189 l Siemens Sensation16 140 1584 Siemens Sensation 16 Straton so 125 1893 l Siemens Sensation16Straton 140 1571 Siemens Emotion6 8 084 1751 l Siemens Sensation10 80o 1155 1893 l Siemens Sensation10 140 _ 1584 Siemens Sensation Open 80 1 071 1812 l Siemens Sensation Open 140 1558 Siemens Sensation64 80o 1 042 1684 l Siemens Sensation64 140 153 Siemens Definition AaS 80o 104 1851 l Toshiba Xpress GX Pre 98 120 1035 Toshiba AquilionMuli4 80 1 117 2072 l Toshiba _ Asteion Multi older tube x 80 1141 2131 Toshiba Asteion Multi CXB 400C tube 80 114 2131 2012 10 25 5 2A CT
48. ric efficiency s 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 Reference Manual or in the Help text it is possible to modify the 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 2012 10 25 5 2A Create your own templates 37 Title Result ST estResult set kV goetkV kV Geometric efficiency dGeometrncEficiency Beam width FWHM SBeamVWidthFWHM mm CTDI 100 SCTDMOQ SUnitCTDI100 5DoseProfileGraph 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 Title Specified title SResult Analysis result STestResult Pass or fail text the overall result for the test SSetkV Set kVp 55etmAs Set m s SetPitch Set pitch SetScanTime Set value for the scan time SSetTubeRotTime Set tube rotation time SSetCollimationNT Set value for the collimation SetPhantomType Set value for phantom type 5
49. tSpeedPus 0 80 1 032 1 927 GEJ ILightSpeed Plus GEJ HiSspeedzxi SS 80 l 1027 1810 GE IHiSpeedNXi C I 80 107 1810 CT Dose Profiler User s Manual 2012 10 25 5 2A Appendix 53 LiahiSpeed Ultra 80 1042 2009 ea ieee p 16 mamaman T Yuma so f roor 1 996 GE lt LightSpeed Pro 16 GEJ LightfpeedRT 1 093 214 GEJ kLightfpeedaVCT oo 8 1 136 2 046 GE ightSpeedVCT smallhd largebd 80 1 061 2041 GE LiahtSpeed VCT small hd large bd Philips JPhilips 310 GE2 no Cu 0120 108 Philips JPhilips 350 GE2 no Cu 120 1088 Philips PPhiips310 GE2 w Cu 0120 1025 Philips JPhilips 350 GE2 w Cu 120 1025 Philips PPhiips 310 GE3 no Cu 120 1956 Philips JPhilips 350 GE3 no Cu 10 1956 Philips Jhilps310 GE3w Cu ss 120 Y Philips Philips 350 GE3 w Cu 1 122 Y Phos his Philips AV 8 1120 2 034 Philips Philips LX j 8 1120 2 034 Philips Philips SR7000 oo 80 1120 2 034 Philips Philips TX 00 po Philips Philips TX 1201088 Philips Philips TX 80 Philips PhiipsMx8000 106 1 888 2012 10 25 5 2A CT Dose Profiler User s Manual OIII II Appendix Philips Philips mx8000 140 1653 Philips M8000 IDT Brilliance 16 amp Power 90 1 072 1765 l Philips Philips Big Bore 90 1113 188 l Picker Picker12008X f 80 3008 Picke
50. 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 x Untitled fe Measurements E Library kv mm mm 5 i mGy In ko 80 12 mm s Head 1 000 171 1 00 in 2 120 16 Head 1 000 171 1 00 12 00 E In 3 100 Body 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 and begin the CT scan from the console ie oe mr Untitled Ocear a Measure Design Datalink Appearance Reporting Central database Help 5 e a G id rh Clear row 2 sa 7 Get a a ji a a i F EE zi ki E la z Clear all saad Expt Detector Favorites Capture Pause Position Meter li n check info L Close 28 You will see how the measurement is progressing on Ocean s status bar is acquired I LA Li Ti ke lf l di ji L a Tj oi L i L TJ L mil fo L C Mon a i lt m A M ss T Untited TTTTTiessurements lt gt Library The dose profile willnow 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 and redo the me
51. tion 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 2012 10 25 5 2A CT Dose Profiler User s Manual CT Dose Profiler User s Manual 2012 10 25 5 2A Chapter 4 Theory r Theory 4 Theory 4 1 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 oo 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 DI go central measurement and the software will then calculate CTDI and CTDI a automatically The Appendix k factors lists all scanners currently supported in Ocean There are a number of different quantities related to CTDI The most common are summarized in the table below Quantity Symbol Remarks Volume CTDI CTDlvol As CTDIw but corrected for pitch Dose length product DLP Takes the irradiated volume into jsa ent ukana The CTDI quantity can be interpreted as the radiation energy deposited
52. tive 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 Professional is required see topic Modify analysis and Advanced analysis in Ocean Reference Manual or Help text for more information This example shows three measurements each with its own analysis Only the first measurement is performed in this case Tube rotation time Scan speed Measuring time Exposure View Select Set kV Collimation s mGy In 2 120 12 1 000 1 00 12 00 15 In 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 Measuring time e Use Low sensitivity for Head phantom and free in air and High sensitivity for Body phantom 2012 10 25 5 2A CT Dose Profiler User s Manual 3 Create your own templates The calculation analysis for the first measurement looks like this Result Pass Set kV 120 kV Geometric efficiency 66 7 Beam width FWHM 27 7 mm CTDI 100 63 21 mGy E S Eag Epost re rat tays 8 Default pass fail criteria When you add the CTDI helical scan free in air analysis the following pass fail criteria is shown Min Max Geomet
53. ult layout and macros As described in the topic Advanced analysis in the Ocean Reference Manual or Help text it is possible to modify the the layout of the analysis result Ocean Professional is required The layout is defined as 2012 10 25 5 2A CT Dose Profiler User s Manual 3 Create your own templates 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 CTDI w SCIDIW SU nitw CTDIvol SC TDivol SUnitvol DLP SDLP SUntDLP 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 CT DI in phantom helical scan analysis CT Dose Profiler User s Manual 2012 10 25 5 2A Create your own templates HEST STitle Specified title SResult Analysis result STestResult Pass or fail text the overall result for the test SSetkV Set kVp SSetrnAs Set mAs SetPitch Set pitch SetScanTime Set value for the scan time SSetTubeRotTime Set tube rotation time SetCollimationNT Set value for the collimation SetPhantomType Set value for phantom type 5can5peed Calculated scan speed Set Pitch Collimation NT Set Tube Rot
54. xial 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 holes 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 S 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

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