In vivo dosimetry of high-dose-rate interstitial brachytherapy in the pelvic region: use of a radiophotoluminescence glass dosimeter for measurement of 1004 points in 66 patients with pelvic malignancy.
OBJECTIVE
To perform the largest in vivo dosimetry study for interstitial brachytherapy yet to be undertaken using a new radiophotoluminescence glass dosimeter (RPLGD) in patients with pelvic malignancy and to study the limits of contemporary planning software based on the results.


METHODS
Sixty-six patients with pelvic malignancy were treated with high-dose-rate interstitial brachytherapy, including prostate (n = 26), gynecological (n = 35), and miscellaneous (n = 5). Doses for a total of 1004 points were measured by RPLGDs and calculated with planning software in the following locations: rectum (n = 549), urethra (n = 415), vagina (n = 25), and perineum (n = 15). Compatibility (measured dose/calculated dose) was analyzed according to dosimeter location.


RESULTS
The compatibility for all dosimeters was 0.98 +/- 0.23, stratified by location: rectum, 0.99 +/- 0.20; urethra, 0.96 +/- 0.26; vagina, 0.91 +/- 0.08; and perineum, 1.25 +/- 0.32.


CONCLUSIONS
Deviations between measured and calculated doses for the rectum and urethra were greater than 20%, which is attributable to the independent movements of these organs and the applicators. Missing corrections for inhomogeneity are responsible for the 9% negative shift near the vaginal cylinder (specific gravity = 1.24), whereas neglect of transit dose contributes to the 25% positive shift in the perineal dose. Dose deviation of >20% for nontarget organs should be taken into account in the planning process. Further development of planning software and a real-time dosimetry system are necessary to use the current findings and to achieve adaptive dose delivery.
Nose
Takayuki
T
Department of Radiation Oncology, The Cancer Institute Hospital of the Japanese Foundation for Cancer Research, Tokyo, Japan. takayuki.nose@jfcr.or.jp
Koizumi
Masahiko
M
Yoshida
Ken
K
Nishiyama
Kinji
K
Sasaki
Junichi
J
Ohnishi
Takeshi
T
Kozuka
Takuyo
T
Gomi
Kotaro
K
Oguchi
Masahiko
M
Sumida
Iori
I
Takahashi
Yutaka
Y
Ito
Akira
A
Yamashita
Takashi
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D005260:Female; D005833:Genital Neoplasms, Female / Q000532:radiotherapy; D006801:Humans; D049449:Luminescence; D008297:Male; D008875:Middle Aged; D010386:Pelvic Neoplasms / Q000532:radiotherapy*; D010502:Perineum; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011834:Radiation Monitoring / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D012007:Rectum; D014521:Urethra; D014621:Vagina