Proposed expansion margins for planning organ at risk volume for lenses during radiation therapy of the nasal cavity in dogs and cats

Zaki Jafry, Arnon Gal, Andre Fleck, Johnson Darko, Valerie J. Poirier

Research output: Contribution to journalArticle

Abstract

Radiation therapy protocols for the feline or canine nasal cavity can damage epithelial cells of the posterior pole of the lens and lead to the development of cataracts. Aims of this retrospective, descriptive study were to calculate movements of the lens during radiation therapy of the nasal cavity in a sample of cats and dogs, and to propose species-specific expansion margins for planning organ at risk volume (PRV) to minimize radiation doses to the lens. All included patients were immobilized with an indexed bite block and positioned in a vacuum positioning cushion for head irradiation. On-board cone beam CT (CBCT) imaging was used for patient alignment. Both ocular lenses were contoured on the therapeutic CBCTs. Coregistration (fusion) between the planning CT and CBCTs was used to measure the movements of the lens. Two measurements were made: the differences between the centroid point of each lens as well as the displacement of the coregistrations. A total of 496 different observations were recorded from 14 cats and 52 dogs. Using the displacement results, we calculated how often the lens would be within the lens-PRV contour. We proposed that an optimal expansion margin from the lens volume of 2 mm in cats and 3 mm in dogs may be necessary in generating PRV expansion for the lens. From our results, we expect the lens would therefore be within these proposed PRV expansions in 92% of the feline measurements and 95% of the canine measurements.

Original languageEnglish (US)
Pages (from-to)471-478
Number of pages8
JournalVeterinary Radiology and Ultrasound
Volume58
Issue number4
DOIs
StatePublished - Jul 1 2017

Fingerprint

Organs at Risk
nasal cavity
Nasal Cavity
radiotherapy
Lens
Lenses
Cats
Radiotherapy
planning
Dogs
cats
dogs
Felidae
Canidae
eye lens
Crystalline Lens
descriptive studies
cataract
Bites and Stings
Vacuum

Keywords

  • CT scan
  • IGRT
  • IMRT
  • nasal tumor

ASJC Scopus subject areas

  • veterinary(all)

Cite this

Proposed expansion margins for planning organ at risk volume for lenses during radiation therapy of the nasal cavity in dogs and cats. / Jafry, Zaki; Gal, Arnon; Fleck, Andre; Darko, Johnson; Poirier, Valerie J.

In: Veterinary Radiology and Ultrasound, Vol. 58, No. 4, 01.07.2017, p. 471-478.

Research output: Contribution to journalArticle

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