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The dosimetric effect of organ movement in prostate radiotherapy: New models for hollow organs
Author(s) -
Pavel Luciana Maria
Publication year - 2003
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1563071
Subject(s) - rectum , dosimetry , prostate , radiation therapy , nuclear medicine , radiation treatment planning , medicine , dose volume histogram , radiology , cancer , surgery
In this work two new models were developed in order to calculate the effects of movement on the dose distribution for hollow organs. For the rectum a two‐dimensional model is used where isotropic expansion or contraction is allowed in the plane of each CT slice. A fully three‐dimensional (3D) deformations model was created for the bladder which was considered as an isotropic expanding/contracting contour about its center of mass. The idea is to determine the dose to specific pieces of tissue in the hollow organ wall for a series of outlines. The dose affecting the wall of the hollow organ (sensitive tissue volume) each fraction, was plotted as a dose‐surface‐histogram (DSH). Also, for the first time, a “final” DSH—which takes into account the organ movements over 9 or 10 fractions—was calculated for five patients and compared to each daily DSH. As a result of interfraction motion, the rectum and bladder are shifted systematically into or out of the high dose region, thus resulting in a “final” DSH which differs from the planning DSH. All the results obtained in this work are crucial for a better estimation of the uncertainty in the dose delivered to the normal tissue of the hollow organs at risk when organ motion is present. The use of DSHs instead of dose‐volume‐histograms (DVHs) for hollow organs and the explicit inclusion of geometrical information of the 3D dose distribution should lead to better predictions of late rectal or bladder complications after radiotherapy of prostate cancer.