Use of the MPPG 5 Profile Comparison Tool
To load measured scans, click the “Get Measured Dose File” button. The “Select Measured Data” window will open. By default, only files with the ‘.ASC’ extension will be shown. Select a file and click “Open”. After a brief loading period, the text next to “Measurement File” and “Measurement Status” will change. The “Measurement File” line will display the measured dose filename. The “Measurement Status” will summarize the contents of the measured dose file (Figure 4.1).
Figure 4.1: The main window after loading measured data
To load a calculated DICOM-RT DOSE file, click the “Get Calculated Dose File” button. The “Select DICOM-RT Dose File” window will open. By default, only files with the ‘.dcm’ extension will be shown. Select a file and click “Open”.
After a brief loading period, the text next to “DICOM-RT DOSE File” and “DICOM Status” will change. The “DICOM-RT DOSE File” line will display the measured dose filename. The “DICOM Status” will describe the loading process and whether it was successful in automatically finding the DICOM offset (Figure 4.2).
Figure 4.2: The main window after loading a DICOM-RT DOSE file. The DICOM offset was automatically determined.
The MPPG #5 Profile Comparison Tool will attempt to determine the DICOM Offset automatically using other files in the same directory. If the required files are in the same directory and point called “ORIGIN” was created in the TPS, the offset will be extracted from these files automatically. If not, the “Enter DICOM Offset…” box will appear and allow you to enter the DICOM offset manually (Figure 4.3).
Figure 4.3: The “Enter DICOM Offset…” Window
If you wish to change the DICOM offset after the DICOM-RT DOSE file has been loaded, click the “Edit DICOM Offset…” button. The “Enter DICOM Offset…” box will appear and allow you to enter the DICOM offset manually.
To compare the measured profiles to the calculated data in the DICOM-RT DOSE file, click the “Run” button (Figure 4.4).
Figure 4.4: The “Run” button
There are a number of profile normalization options available. Normalization options may be set separately for depth dose profiles and inline/crossline profiles (Figure 4.5).
- Normalize Depth Dose Profile To:
- Dmax: The measured and calculated depth dose profiles are rescaled such that that maximum dose for each profile is 1.
- Depth (Y): When the user selects this option, the box next to “Depth (Y) =” becomes editable. The user may enter a normalization depth in the box. The profiles will be normalized to the same value at this depth. After normalization at depth, both profiles are rescaled by the same factor so that the measured profile maximum dose has a relative value of 1.
- Normalize Inline and Crossline Profile To:
- Dmax: The measured and calculated dose profiles are rescaled such that that maximum dose for each profile is 1.
- Position (X,Z): When the user selects this option, the boxes next to “Crossline (X) =” and “Inline (Z) =” becomes editable. The user may enter a normalization location in the box.
- For crossline profiles, the measured and calculated dose profiles will be normalized to the same value at the location in the “Crossline (X) =” box.
- For inline profiles, the measured and calculated dose profiles will be normalized to the same value at the location in the “Inline (Z) =” box.
- After normalization at a given position, both profiles are rescaled by the same factor so that the measured profile dose maximum has a relative value of 1. For diagonal profiles:
- If there is any change in depth, the depth-dose options will apply
- If there is no change in depth, the diagonal profile will use the crossline profile options.
Figure 4.5: The Depth-Dose and Profile Normalization Options box
The gamma analysis criteria may be specified in the “Gamma Analysis Options” box. (Figure 4.6).
- Dose Diff. (%): The dose difference criterion for gamma analysis
- DTA (mm): The distance-to-agreement criterion for gamma analysis
- Dose Analysis:
- Global: The dose difference percentage will be calculated relative to the maximum measured dose in the profile.
- Local: The dose difference percentage will be calculated relative to the local measured dose value.
- Use Threshold?: Checking this box enables the use of a threshold below which measured data points will be excluded from the gamma analysis
- Threshold Value Box (%): If "Use Threshold?" is checked, the threshold value box will become enabled and allow the user to enter a percentage value. If a measured dose point in the profile is less than the threshold percentage of the normalization dose, then the point will not included in the gamma analysis.
Figure 4.6: Gamma Analysis Options box
The program produces two kinds of output. They may be turned on and off in the “Output Options” box (Figure 4.7).
- Create CSV File: A comma-separated value file called “mppg_out_table.csv” will be created. The file contains a log of each profile analyzed. Each entry includes filenames, scan axis, measurement depth and results of the gamma analysis.
- Create PDF: Figures will be created for each profile analyzed and saved as a PostScript file. The user may convert this to a PDF. The figures contain a comparison of the measured and calculated profiles. They also show the gamma analysis value across the profile.
Figure 4.7: Output Options box