Accuracy of Intracavitary Applicator Reconstruction for Cervix Cancer Brachytherapy
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Date
2019-12-03Author
ALMasri, Hussein
Kakinohana, Yasumasa
Toita, Takafumi
Ariga, Takuro
Kasuya, Goro
Murayama, Sadayuki
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Show full item recordAbstract
The accuracy of intracavitary applicator reconstruction for cervical cancer was assessed. A homemade phantom that mimics
clinical applicator placement and reference points was used. Three stainless steel (15°, 30°, and 45°) tandems, x-ray markers, and
three reference points were used to compare radiography- and CT-based systems. For CT reconstructions, two Fletcher CT
compatible (15° and 30°) tandems, two ovoids, and two reference points, with and without inserted x-ray markers, were used. A
2.5-mm CT slice thickness was used. To check for inter- and intra-operator variations in CT, only a 30° tandem without x-ray
markers and 1.25-mm CT slice thickness were used. Applicators were reconstructed three times for each image set to verify the
operator reproducibility. A 6 Gy dose was prescribed and normalized at AL-point. Source dwell times were compared to check
for dose variation at A-point. Maximum standard deviations SD (σ) for radiography and CT reconstructions were 0.35 and
0.83mm, respectively. Analysis of variance for the means of 15° and 30° tandems showed no significant difference. Levene’s test
proved insignificant difference for 15° tandem (p value = 0.131), whereas it showed a significant difference for 30° tandem (p
value = 0.011). This phantom study showed that the variance of dwell times between the two methods for 30° tandem was
statistically significant due to increased applicator curvature. CT proves superiority to radiography. X-ray marker method was
more accurate but has less image quality. Inter- and intra-oncologist variations showed good agreement.