DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE Rev. 1.0 DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE DoseLab users may reference the following instructions to perform Tomotherapy Quality Assurance tests as recommended in AAPM Report of the Task Group Report 148: QA for helical tomotherapy. Each section refers to the corresponding TG-148 heading/text to describe how the tests should be analyzed utilizing the existing DoseLab modules. Familiarity with TG-148 is highly recommended. Prior to completing these tests, the example Tomotherapy preference files should be imported into DoseLab. TG-148 RECOMMENDED TESTS 1. V.B.1.C. - Y-JAW DIVERGENCE/BEAM CENTERING The machine isocenter must be within 0.5 cm based on the recommended image of the Task Group. Please see Detailed QA Test Descriptions for the instructions to perform this test. 2. V B.1.D. - Y-JAW/GANTRY ROTATION PLANE ALIGNMENT The slope of each line on the recommended image must not vary by more than 5 degrees. Obtain the images as described in the Task Group report and follow these steps to analyze: 1. Open the *.tif image in DoseLab s Single Image Analysis module 2. Crop the image to include only the exposure created at 50 cm SID 3. Open the MLC Strip Test tool via Machine QA MLC Strip test 4. Manually enter an SID of 50 cm 5. In the Tolerances dropdown, select Edit 6. Highlight the V.B.1.d. y-jaw/gantry rotation plane alignment Tolerance set 7. Change the Slope of lines baseline value to match the current slope displayed in the Results window 8. Select OK to save the changes 9. Save these baseline results to the Database (Results Save to PDF or database) and exit the MLC Strip Test tool 10. Re-open the raw, un-cropped image and crop the image again this time only include the exposure at 110 cm SID 11. Manually enter an SID of 110 cm 12. Choose the V.B.1.d. y-jaw/gantry rotation plane alignment tolerance set from the Tolerance dropdown 13. Verify that the slope of the 110 cm SID image is within 5 degrees of the 50 cm SID baseline (set in step 4). 3. V B.1.E. - TREATMENT FIELD CENTERING The center of the described fields must be within 0.5 mm. Please see Detailed QA Test Descriptions for further detail. 4. V.B.1.F. - MLC ALIGNMENT TEST The alignment verification must verify that the MLC offset is less than 1.5 mm and 0.5 degrees at isocenter. Take an image as described in the Task Group Report and follow these instructions to analyze the resulting image: 1. Open the *.tif image in DoseLab s Single Image Analysis 2. Open the MLC Strip Test Tool via Machine QA MLC Strip test 3. Manually define an SID of 85 cm 4. Open the V.B.1.f. MLC alignment test tolerance set, verify the twist slope & strip distances, and save to the Database a. Overall twist is multiplied by a factor of 2 in this case; therefore the result should be divided by 2 for MLC twist. Since this is a baseline value, it is acceptable to monitor the total twist if the user understands this parameter. 1
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE Rev. 1.0 5. V.B.3.A. - GANTRY ANGLE CONSISTENCY The gantry angles must be accurate within 1 degree. For image analysis, follow these steps: 1. Open first image in DoseLab s Single Image Analysis 2. Run the Starshot tool via Machine QA Starshot 3. Under Preferences ensure that Display angle of each spoke is selected 4. Record angles in Database (must be performed manually via Custom Tests, as angle results are not automatically saved) 5. Repeat for any additional starshot images 6. V.B.3.B. - COUCH SPEED UNIFORMITY The dose delivered along the couch s axis of travel must vary by less than 2 % when subjected to couch motion. Delivery shall be based on TG148 and clinically relevant parameters. Follow these instructions to analyze the resulting image: 1. Open the *.tif image in DoseLab s Single Image Analysis 2. Open the Flatness and Symmetry tool via Machine QA Flatness and symmetry 3. Select the V.B.3.b. Couch speed uniformity tolerance set 4. Select the appropriate baseline for comparison 5. Verify the relative optical density of along the couch travel axis does not vary by 2% and save results to the Database 7. V.B.3.C. - COUCH TRANSLATION/GANTRY ROTATION Consistent spacing of exposures during gantry rotation & couch movement is verified with this test. To analyze the resulting image: 1. Open the *.tif image in DoseLab s Single Image Analysis 2. Open the MLC Strip Test Tool via Machine QA MLC Strip test 3. Manually define an SID of 85 cm 4. Open the V.B.3.c. Couch translation/gantry rotation tolerance set, verify the results, and save them to the Database 8. V. B.4.A - INTERRUPTED TREATMENT PROCEDURE Standard and interrupted treatments must differ by no more than 3% in dose and 1 mm in the y direction. Follow these instructions to analyze the image for this test: 1. Convert both films to OD by using the Flatbed Scanners tool 2. Open the Dose Comparison Interface 3. Change gamma criteria to 3%/1 mm 4. Run a Film to Film comparison 9. V.B.4.B. LASER LOCALIZATION The lasers must be within 1 mm of the radiation field. Please see Detailed QA Test Descriptions for further detail. 10. V.I.B.2 IMAGE QUALITY Image quality constancy for the MVCT is verified with this recommended assessment. Analyze the resulting MVCT of this test by: 1. Open MVCT images in the DoseLab CT/CBCT tool 2. Select appropriate slice(s) by manually entering the slice number, verify the results, and save results to the Database 2
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE v. 1.0 DETAILED QA TEST DESCRIPTIONS Prior to performing these tests, the user should manually copy the example Tomotherapy both the MLC Strip Test tolerance.mat and CBCT phantoms.xml files into their Preferences folder (where DoseLab is installed) to populate the preset Tolerance sets and Tomotherapy-related phantoms. These coped files will overwrite the default tolerance set, so if there is any customization already performed by the user it is suggested that they first contact Mobius Medical Systems Customer Support (support@mobiusmed.com) prior to copying these files. Alternatively, advanced users may add these Tolerances sets manually if preferred. For guidance on film scanning with Epson scanners, see Appendix C of the DoseLab User Manual. 1. V.B.1.C. - Y-JAW DIVERGENCE/BEAM CENTERING 1. Take an image as described in the Task Group Report - verification that the center of the described fields is within 0.5 mm can be completed by obtaining two separate vertical profile measurements and subtracting the central position of each respective profile s FWHM 2. Using the scanned image, open the image in Single Image analysis 3. Load the Profiler tool via Analysis Image profiler and export two profiles that are 0.5 cm from the field convergence in the image, demonstrated by the solid and dotted lines on the image below 4. Select the appropriate Profile type based on the image orientation (if image is in the orientation shown below, choose Vertical profile ) 5. Select Save profile to save the data in an Excel spreadsheet format 6. Repeat this for both images 7. Once in Excel, utilizing the Distance and Image value columns from each spreadsheet, normalize the image value column to the maximum value for that column 8. From this conversion, determine the FWHM value and use the appropriate inverse square scaling to determine the offset. For an example of this test results, see sheet labeled V.B.1.C. in DoseLab - TG148 Example.xls. Figure 1: V.B.1.C. Image Display in DoseLab s Image Profiler Module
2. V B.1.D. - Y-JAW/GANTRY ROTATION PLANE ALIGNMENT DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE Rev. 1.0 1. Following the Task Group report, obtain two images: a. One at 50cm SID b. And one at 110cm SID 2. After scanning, manually split the image into two separate images via DoseLab s Single Image Analysis interface: a. One containing only the 50cm SID portion of the image b. And another containing only the 110cm SID portion of the image. 3. Load the 50cm SID image into the MLC Strip Tool Single Image Analysis 4. Open the MLC Strip Tool via Machine QA MLC Strip test 5. Find the slope of the line in the Results window and set this value as the test s Baseline value by selecting V.B.1.d. Y- Jaw/Gantry Rotation Plane Alignment from the Tolerances dropdown 6. Subsequently, load the 110cm SID image and cross-compare the line slope from the 50cm SID baseline value. 7. Show that the line slope does not deviate by more than 0.5 degrees. Note that the warn value should be set to 0.25, as the physical jaw twist is half of the angle between the fields as measured on the film. If utilizing the provided Example Tomotherapy Tolerance Set, this will be preset as the value. Figure 2: V.B.1.D. Image Setup in DoseLab s MLC Strip Test Module 4
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE v. 1.0 3. V B.1.E. - TREATMENT FIELD CENTERING Verifying that the center of the fields is within 0.5 mm can be performed by taking several profile measurements of the TG-148 recommended image and finding the central fit line displayed by a linear regression. A single vertical profile going through each exposure along with a single horizontal profile will be sufficient information. 1. Capture the images as instructed in TG-148 and scan them for analysis 2. Open the exposure in Single Image Analysis 3. Using the Image Profiler tool (Analysis Image profiler), capture a vertical profile though each exposure a. After all profile captures, you should have 8 total: i. 7 vertical profiles, 1 through each of the 7 individual exposures ii. 1 horizontal profile that traverses all exposures at once 4. Select Save profile to save the data in an Excel spreadsheet format one full horizontal profile and one vertical profile for each individual exposure 5. Determine the FWHM of the vertical profiles to find the center of each region 6. Optional: If preferred, the resulting data could be used to calculate a linear regression for overall pass of this test. It would be determined by how close the value of the results is to 1. Failing results would likely be ±0.1 from the nominal value, but this level should be determined by your clinically relevant data. This would be user-calculated. For an example of this test results, see sheet labeled V.B.1.E. in DoseLab - TG148 Example.xls. Figure 3: V.B.1.E. Image Display in DoseLab s Image Profiler Tool
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE Rev. 1.0 4. V.B.1.F. - MLC ALIGNMENT TEST 1. Obtain an image as described in TG-148 - the MLC offset should be less than 1.5 mm at the isocenter and the MLC twist should be less than 0.5 (or per vendor specifications, as they may change) 2. After scanning the image, load the scanned image into Single Image Analysis 3. Open the MLC Strip Tool via Machine QA MLC Strip test 4. Once in the MLC Strip tool, proceed to Preferences and uncheck Perform Lorentzian fit to utilize a Gaussian fit 5. Ensure that the provided example Tomotherapy Tolerance Set reflects the appropriate Baseline and Warn/Fail tolerances as described in TG-148, or as is clinically relevant by selecting, V.B.1.f. MLC Alignment Test from the Tolerances dropdown 6. Manually enter the SID 7. The resulting Distance between lines and Slope of lines should supply the necessary data, as recommended in the Task Group Note that the overall twist is magnified by a factor of 2 and should therefore be divided by 2 to obtain true MLC twist results. Uncheck Perform Lorentzian fit Manually define the SID Figure 4: V.B.1.F. Image Setup in DoseLab s MLC Strip Test Module 6
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE v. 1.0 5. V.B.3.A. - GANTRY ANGLE CONSISTENCY The control sinogram for this test is set to open the middle two leaves 32 and 33 at projections centered at 0, 120, and 240. Using a horizontal line marked on the films during setup, the resulting star pattern can be checked for the correct initial angles at the start of treatment and the ability to reproduce this pattern after 24 rotations. 1. Take the images as directed in the Task Group report and scan the image 2. Load the test s recommended image into Single Image Analysis 3. Open the Starshot Tool via Machine QA Starshot 4. Under Preferences ensure that Display angle of each spoke is selected 5. The resulting gantry angles should be reproducible with a tolerance of 1 6. Optional: Enter the results into the V.B.4.B. sheet the DoseLab TG148 Example spreadsheet. Import the spreadsheet values into the Database. For an example of this test built in the Database, see the example in Machine B. Note that the angle values are not directly saved to the database and will need to be entered via a user-created Custom Test. For information on creating custom test, see the DoseLab User Guide. Angles are not automatically saved to the database Figure 5: V.B.3.A. Image Angle Results Display in DoseLab s Starshot Module
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE Rev. 1.0 6. V.B.3.B. - COUCH SPEED UNIFORMITY 1. The film is irradiated with couch movement involved as instructed in TG-148 and scanned 2. With the resulting scan, load the image into Single Image Analysis 3. Open the Flatness and Symmetry Tool via Machine QA Flatness and Symmetry 4. Proceed to Preferences and select these options: a. Apply 5x5 Weiner filter b. Only analyze in vertical profile c. Differences from baseline profiles Calculate maximum differences 5. The result is a profile generated along the axis of couch travel 6. The relative optical density (image value) along this line should vary by less than 2% a. Observe the Max vertical diff from base value for this metric Filter for film noise Only relevant profile Compare for constancy. Figure 6: V.B.3.B. Image Display in DoseLab s Flatness and Symmetry Module 8
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE v. 1.0 7. V.B.3.C. - COUCH TRANSLATION/GANTRY ROTATION 1. The resulting film from the Task Group is exposed and scanned 2. Load the image into Single Image Analysis 3. Open the Flatness and Symmetry Tool via Machine QA Flatness and Symmetry 4. Ensure that the provided example Tomotherapy Tolerance Set reflects the appropriate Baseline and Warn/Fail tolerances as described in TG-148, or as is clinically relevant by selecting, V.B.3.c Couch Translation/Gantry Rotation from the Tolerances dropdown 5. The resulting profile should show maxima 5 cm apart to within 1 mm Match exactly with TG148 Figure 7: V.B.3.C. Image Display in DoseLab s Flatness and Symmetry Module
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE Rev. 1.0 8. V.B.4.A - INTERRUPTED TREATMENT PROCEDURE 1. Acquire the necessary films per protocol instruction and scan the films accordingly 2. Convert both scanned films to optical density (OD) by using the Flatbed Scanners tool a. Load an unexposed film image (or select Convert the film to OD without applying uniformity correction if desired) b. Choose the appropriate color channel based on the recommended dose levels c. Select Exposed film image and navigate to the the exposed film d. Choose Process image in the Select Files window to save the file in OD values e. The OD-converted image will save to the same location as the non-converted image was located. For example, if the non-converted film was saved as C:\DoseLab\Measured, the resulting OD film would be named C:\DoseLab\Measured-OD f. Ensure this is repeated for the second film g. Further detail on this step may be found in the Section 4.2.2 of the DoseLab User Manual 3. After the image is converted to OD, open the Dose Comparison Interface from DoseLab s main menu 4. Under Preferences Default comparison values, change the gamma criteria to 3%/1mm and select OK 5. In the Dose Comparison Preset dropdown, select Film to film 6. Load one of the converted films as the Calculated distribution and the other as the Measured distribution a. The order of selection is not significant as long as the user is aware of what each film has been labeled 7. Choose Next from the interface to proceed with a film to film comparison a. Details on this type of comparison, which each step entails, as well as all automation provided by the Dose Comparison Interface can be found in Section 4.4 of the DoseLab User Manual 8. When overlaid, the interrupted treatment should differ from the completed procedure by no more that 3% in its delivered dose and the overall length FWHM of the dose distribution in the y-direction should differ by no more than 1 mm. Viewing the Gamma image will provide graphical representation of this comparison. 9. Optional: Enter the results into the V.B.4.A. sheet of the DoseLab TG148 Example spreadsheet. Import the spreadsheet values into the Database. For an example of this test built in the Database, see the example in Machine B. Figure 8: V.B.4.A. Gamma Display in DoseLab s Dose Comparison Module 10
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE v. 1.0 9. V.B.4.B. - LASER LOCALIZATION 1. Obtain images as instructed in TG-148 recommendations 2. Images should be scanned in for analysis if necessary, see Appendix C in the DoseLab User Manual for film scanning recommendations with Epson scanners 3. In order to verify laser localization accuracy within 1 mm, several profiles will need to be taken over the image. These may be obtained using the Image Profiler tool in Single Image analysis (Analysis Image profiler) 4. In each instance, select Save profile to save the data in an Excel spreadsheet format 5. First, open the sagittal laser image and save four vertical profiles: a. Two directly over of the sagittal laser fiducials (as shown with the dotted white line below) b. And two along the exposure just next to the outer fiducials (as shown with the solid white line below) Figure 9a: V.B.4.B. Image Display in DoseLab s Image Profiler Tool with Vertical Profile Markings 6. Next, two horizontal profiles should be taken, one across each of the axial laser fiducials, as shown by the dotted and solid white lines below Figure 9b: V.B.4.B. Image Display in DoseLab s Image Profiler Tool with Horizontal Profile Markings 7. The profiles through the exposure are used to determine the angular displacement of the image itself by performing a linear regression from the center of each respective FWHM. The sagittal marks profiles can then be corrected for any slope to verify the 1mm positioning accuracy. 8. Next, the two horizontal profiles overlaying the axial laser marks will provide information to determine the positioning and demonstrate any angular discrepancy. The value should be within 1 degree of a total 90 degree offset from the sagittal marks. 9. Finally, the distance measurement tool in DoseLab provides the information for the movable laser positioning. To utilize this tool, open the image in Single Image Analysis and select Analysis Distance measurement. For an example of this test results, see sheet labeled V.B.4.E. in DoseLab - TG148 Example.xls.
DOSELAB TOMOTHERAPY TG-148 QA QUICK GUIDE Rev. 1.0 10. V.I.B.2 - IMAGE QUALITY 1. Obtain the MVCT images as described in TG-148 2. From DoseLab s main interface, choose CT / CBCT 3. When prompted, navigate to the location of the images for analysis 4. Utilize the CBCT module with manual slice detection by ensuring that Preferences Autodetect slices at startup is unchecked 5. Select Tomo Test from the Phantom dropdown 6. Choose View CT scan to select the appropriate slice and then close the viewer to enter this value into the Slice box 7. Hit Process to obtain results for CNR, Uniformity, Spatial Resolution, Contrast, Scaling Discrepancy, Geometric Distortion. 8. These results may be directly saved to the DoseLab database. Manual Slice selection needed for MVCT Figure 20: V.I.B.2. CBCT Display in DoseLab s CT/CBCT Module with ROIs Overlaid 12