A STUDY TO EVALUATE SINGLE PORT, CENTRAL AXIS DOSIMETRY AND VERIFICATION TECHNIQUES FOR VETERINARY RADIOTHERAPY, USING THE CANINE NASAL CAVITY AS A MODEL TARGET
M. Walker et al., A STUDY TO EVALUATE SINGLE PORT, CENTRAL AXIS DOSIMETRY AND VERIFICATION TECHNIQUES FOR VETERINARY RADIOTHERAPY, USING THE CANINE NASAL CAVITY AS A MODEL TARGET, Veterinary radiology & ultrasound, 35(3), 1994, pp. 210-216
Ten normal dogs received single doses of Co-60 radiation to their nasa
l cavity. The minimum nasal cavity dose was estimated using three diff
erent techniques: manual calculation from percent depth dose tables, c
omputerized planning for a homogenous field, and computerized planning
utilizing field heterogeneity factors. The doses delivered were measu
red by LiF thermoluminescent dosimetry (TLD) and by verification film
densitometry. The radiation dose resulting from manual calculated pres
criptions correlated well to those from computerized planning for a ho
mogenous soft tissue field (corr. coeff. .87; p = .001). However, for
both of these methods the estimated dose differed from the measured do
se by about 12%. Computerized planning utilizing field heterogeneity f
actors showed no improvement over the previous two methods, (corr. coe
ff. .88; p = .0009) but the results were biased by the dose measuremen
ts being central axis doses in a normal nasal cavity. Both manual and
computerized verification film densitometry correlated well to TLD mea
surements (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 wel
l to manual calculated prescriptions (corr. coeff. .86 and .85 respect
ively, p = .0015 and .0016 respectively). Also manual and computerized
verification film densitometry correlated well to computer calculatio
ns using homogenous tissue fields (corr. coeff. .86 and .85 respective
ly, p = .0015 and .0016 respectively) and to computer calculations usi
ng 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 fo
r which accurate dosimetry is difficult to achieve.