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COMPARISON OF INTERFRACTIONAL VARIATION IN CANINE HEAD POSITION USING PALPATION AND A HEAD‐REPOSITIONING DEVICE
Author(s) -
MAYER MONIQUE N.,
WALDNER CHERYL L.,
ELLIOT KIRSTEN M.,
SIDHU NARINDER
Publication year - 2010
Publication title -
veterinary radiology and ultrasound
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.541
H-Index - 60
eISSN - 1740-8261
pISSN - 1058-8183
DOI - 10.1111/j.1740-8261.2010.01672.x
Subject(s) - medicine , palpation , head (geology) , position (finance) , variation (astronomy) , nuclear medicine , anatomy , radiology , finance , geomorphology , economics , geology , physics , astrophysics
Radiation treatment planning is performed on images that do not take variation in patient position into account. To compensate for expected variations in position of the patient, a three‐dimensional expansion of the clinical target volume, or set‐up margin, is added. Variations in patient position can be decreased through use of an immobilization device, allowing selection of a smaller set‐up margin. The objective of this prospective study was comparison of interfractional variation in patient position between set‐ups of the canine head region using palpation of bony landmarks and set‐ups using a head‐repositioning device. Fiducial markers were attached to the skull bones of three research dogs, and the dogs were positioned as for a typical radiation treatment of the head region using both set‐up methods. A kilovoltage on‐board imager was used to acquire orthogonal images and the difference between the x ‐, y ‐, and z ‐axis coordinates of each fiducial marker relative to the initial reference isocenter was measured. The difference in patient position for each axis coordinate was significantly lower for set‐ups using the head‐repositioning device than for set‐ups using bony landmarks ( P <0.05). Ninety‐five percent of the absolute values of the displacement vector differences were <4.62 mm for set‐up using bony landmarks, and <1.93 mm for set‐up using the head‐repositioning device. A minimum set‐up margin of 5–6 mm is recommended when patient set‐up is based on bony landmarks and of 2–3 mm when the head‐repositioning device is used.