![]() LoSasso and colleagues 34 compared the penumbra widths of MLCs with Cerrobend blocks, defined as the distance between the 20% and 80% isodose lines. This effect results in scalloping of the isodose curves at around 50%, although the scalloping decreases with increasing depth, especially for higher and lower isodose values (Fig. The method of determining leaf position by maintaining a constant aperture area does not take into account the staircase effect from the finite width of the MLC leaves. Using this convention, the treatment area of each field is the same for the cerrobend aperture and the MLC aperture. The most commonly used strategy is to replace the "cerrobend aperture" with the MLC, positioning the leaves so that their ends transect the aperture. Because of the large number of leaves, it is essential to have some automated method of determining their positions in the treatment-planning system. Clifton Ling, in Oncologic Imaging, 2002 Treatment Planning with Multileaf CollimatorĪlthough the use of a multileaf collimator (MLC) does not in principle alter the treatment-planning process, certain added requirements and features need to be considered.
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