[Comparison of calculated and measured rectal doses in HDR brachytherapy with Ir-192 source].
Two orthogonal radiographs are used to reconstruct the three-dimensional positions of applicators (sources) and their dosemeter for assessing afterloading techniques. It has always been assumed that the applicators are perfectly fixed and unchanged during irradiation. In a review comparing measurements by a five-detector dosemeter and calculated doses in our institution, a relatively poor correlation (correlation coefficient = 0.79) was observed. The purpose of this study was to investigate the sources of this difference between calculated and measured rectal doses in HDR brachytherapy with Ir-192 source. In this study, the calculated dose was used as a reference value. The overall percentage difference between calculated and measured rectal doses was estimated at 9%. The major source of the difference between calculated and measured rectal doses was applicators and dosemeter movement during irradiation. This was verified by X-ray fluoroscopy during irradiation. It was found that loose fastening of the applicators caused a change in the position of the applicators and dosemeter during irradiation. By improving the fastening of the applicators and dosemeter, the correlation (correlation coefficient = 0.90) between calculated and measured doses was improved. The results demonstrate the importance of the fastening of the applicators and dosemeter.
Kakinohana
Y
Y
Department of Radiology, University of the Ryukyus School of Medicine.
Toita
T
T
Ogawa
K
K
Yoshinaga
M
M
Iraha
S
S
Zukeran
Y
Y
Sawada
S
S
D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D008433:Mathematics; D019047:Phantoms, Imaging; D011874:Radiometry; D011879:Radiotherapy Dosage; D012007:Rectum; D012680:Sensitivity and Specificity; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy
D007496:Iridium Radioisotopes