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Analyze One Beam At a Time

Generally it is our thought that people would do the whole plan and only if something were wrong would one look at single beams. However, some people would rather analyze single beams. This can be done, one simply uses the exact same process but for a plan with only one of the beams. The planning system has to compute the 3D dose matrix for the single beam and one downloads that in RTOG or Dicom RT format. With Dicom RT format there are only two files needed for each single beam plan, the RP file containing the plan with one beam and the RD file containing the dose matrix for this single beam. The 3D dose matrix can be for the patient or a phantom. Shown below is single beams computed for a phantom at gantry angle zero. The process and tools are exactly the same as in processing a plan with all the beams on a CT scan set.

Shown below are two IMRT beams labeled a1 and a3 integrated with the Varian aS500 EPID.

Next below is a transverse plane through isocenter in the phantom, DosimetryCheck result in magenta, compared with the planning system dose (green).

A coronal plane through isocenter in the phantom compared with the planning system dose. (Note 90 degree rotation of above beam's eye view.)

A sagittal plane through isocenter in the phantom compared with the planning system dose.

A 3D view of the dose difference of 5 cGy for beam a1.

Next is the same for the third beam out of five IMRT fields.

One can do gamma analysis as on a multiple beam plan. Shown is the gamma area of 1.0 for 3% of 60 cGy or 3 mm in the coronal plane for beam a1 shown above.