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A STUDY TO EVALUATE SINGLE PORT, CENTRAL AXIS DOSIMETRY AND VERIFICATION TECHNIQUES FOR VETERINARY RADIOTHERAPY, USING THE CANINE NASAL CAVITY AS A MODEL TARGET
Author(s) -
Walker Michael,
Durrer Russell,
Weir Vicki,
Slater Margaret,
MCPherson Jim,
Ray Charles,
Carsten Keith
Publication year - 1994
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.1740-8261.1994.tb01595.x
Subject(s) - densitometry , medicine , nuclear medicine , dosimetry , thermoluminescent dosimeter , nasal cavity , radiation treatment planning , biomedical engineering , radiation therapy , radiology , surgery , dosimeter
Ten normal dogs received single doses of Co‐60 radiation to their nasal cavity. The minimum nasal cavity dose was estimated using three different techniques: manual calculation from percent depth dose tables, computerized planning for a homogenous field, and computerized planning utilizing field heterogeneity factors. The doses delivered were measured by LiF thermoluminescent dosimetry (TLD) and by verification film densitometry. The radiation dose resulting from manual calculated prescriptions correlated well to those from computerized planning for a homogenous soft tissue field (corr. coeff.87; p=.001). However, for both of these methods the estimated dose differed from the measured dose by about 12%. Computerized planning utilizing field heterogeneity factors showed no improvement over the previous two methods, (corr. coeff.88; p=.0009) but the results were biased by the dose measurements being central axis doses in a normal nasal cavity. Both manual and computerized verification film densitometry correlated well to TLD measurements (corr. coeff.97 and .94 respectively, p=.00001 and p=.001 respectively), differing from TLD measurements by about 5–7%. Both manual and computerized verification film densitometry correlated well to manual calculated prescriptions (corr. coeff.86 and .85 respectively, p=.0015 and .0016 respectively). Also manual and computerized verification film densitometry correlated well to computer calculations using homogenous tissue fields (corr. coeff.86 and .85 respectively, p=.0015 and .0016 respectively) and to computer calculations using heterogeneity factors (corr. coeff.89 and .89 respectively, p=.005 and .0005 respectively). Film densitometry was found to be a good method to spot check dose delivery to the nasal cavity, a body part for which accurate dosimetry is difficult to achieve.