Effect of beamlet step-size on IMRT plan quality
The C-shaped structural arrangement of the IMRT benchmark. The OAR is a central cylinder in diameter and in length. The PTV is half a donut that surrounds the cylinder by 180° and is wide. There is a separation between the PTV and OAR.
Isodose lines of the central transverse slices for beamlet size (a) , (b) , (c) , and (d) . The isodose lines from inner to outer positions represent 95%, 70%, 50%, 30%, and 12% of the prescription dose.
Objective function values as the results of the DAO dose optimization. The values are normalized such that the value of the case is 1.
PTV DVH. The percent target volume at least receiving 100% prescribed dose are 95% and 90% for beamlet sizes 1, 2, and , and , respectively.
OAR DVH. This shows that smaller beamlet sizes give a smaller dose to the OAR region.
Dose profiles along a vertical line in the central transverse slice. The dose is plotted against the vertical distance measured from the bottom central point of the OAR on the sampled slice.
Intensity map of the sum of the four leaf pairs in the middle of the PTV in the transverse direction for beamlet size (a) , (b) , (c) , and (d) . For an easy comparison, Fig. 1 is also shown here.
Statistical result. Sigma is standard deviation of the dose.
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