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REPEATABILITY OF A PLANNING TARGET VOLUME EXPANSION PROTOCOL FOR RADIATION THERAPY OF REGIONAL LYMPH NODES IN CANINE AND FELINE PATIENTS WITH HEAD TUMORS
Author(s) -
Yoshikawa Hiroto,
Harmon Joseph F.,
Custis James T.,
LaRue Susan M.
Publication year - 2012
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.1740-8261.2012.01972.x
Subject(s) - medicine , cats , head and neck cancer , radiation treatment planning , lymph , radiation therapy , head and neck , nuclear medicine , cone beam computed tomography , radiology , pathology , surgery , computed tomography
For canine and feline patients with head tumors, simultaneous irradiation of the primary tumor and mandibular and retropharyngeal lymph nodes (LNs) is often indicated. The purpose of this study was to assess the repeatability of a planning target volume (PTV) expansion protocol for these LNs. Two CT image sets from 44 dogs and 37 cats that underwent radiation therapy for head tumors were compared to determine LN repositioning accuracy and precision; planning‐CT (for radiation therapy planning) and cone‐beam CT (at the time of actual treatment sessions). Eleven percent of dogs and 65% of cats received treatment to their LNs. In dogs, the mandibular LNs were positioned more caudally ( P = 0.0002) and the right mandibular and right retropharyngeal LNs were positioned more to the left side of the patient ( P = 0.00015 and P = 0.003, respectively). In cats, left mandibular LN was positioned higher (toward roof) than the planning‐CT ( P = 0.028). In conclusion, when the patient immobilization devices and bony anatomy matching are used to align the primary head target and these LNs are treated simultaneously, an asymmetrical PTV expansion that ranges 4–9 mm (dogs) and 2–4 mm (cats), depending on the directions of couch movement, should be used to include the LNs within the PTV at least 95% of the time.