A comparison of ICRU point doses and volumetric doses of organs at risk (OARs) in brachytherapy for cervical cancer.

In brachytherapy for cervix cancer, doses to organs at risk (OARs) are traditionally calculated using the ICRU-38 point doses to rectum and bladder. Three-dimensional image-guided brachytherapy allows assessment of OAR dose with dose volume histograms (DVHs). The purpose of this study was to analyse the correlation between DVHs and ICRU point doses. Using the PLATO™ planning system, the bladder, rectum and sigmoid were retrospectively contoured on 62 CT datasets for 20 patients treated with definitive radiotherapy. The median external beam radiotherapy dose was 45 Gy. Brachytherapy was delivered using a CT-MRI compatible tandem and ovoids to a median dose of 24 Gy in three fractions. DVHs were calculated, and the minimum dose to 2 cc of tissue receiving the highest dose (D(2cc) ) was recorded and compared with the ICRU point doses (D(ICRU) ). The mean rectal D(ICRU) was 4.01 Gy compared with D(2cc) of 4.28 Gy. The mean bladder D(ICRU) was 6.74 Gy compared with D(2cc) of 8.65 Gy. The mean sigmoid D(2cc) was 4.58 Gy. The mean dose ratios (D(2cc) /D(ICRU) ) were 1.08 for rectum and 1.39 for bladder. D(ICRU) correlated with D(2cc) for rectum (r = 0.76, P = 0.001) and for bladder (r = 0.78, P = 0.01). OAR doses assessed by DVH criteria were higher than ICRU point doses. The significant correlation between D(2cc) and D(ICRU) has allowed us to set DVH dose constraints for CT-based brachytherapy and thus begin the transition from two-dimensional to three-dimensional image-guided brachytherapy planning.

Vinod SK ，Caldwell K ，Lau A ，Fowler AR ... -  《-》

CT based 3-dimensional treatment planning of intracavitary brachytherapy for cancer of the cervix: comparison between dose-volume histograms and ICRU point doses to the rectum and bladder.

Hashim N ，Jamalludin Z ，Ung NM ，Ho GF ，Malik RA ，Phua VC ... -  《-》

Point vs. volumetric bladder and rectal doses in combined intracavitary-interstitial high-dose-rate brachytherapy: correlation and comparison with published Vienna applicator data.

Yaparpalvi R ，Mutyala S ，Gorla GR ，Butler J ，Mah D ，Garg MK ，Kalnicki S ... -  《Brachytherapy》

Dose and volume parameters for MRI-based treatment planning in intracavitary brachytherapy for cervical cancer.

Kirisits C ，Pötter R ，Lang S ，Dimopoulos J ，Wachter-Gerstner N ，Georg D ... -  《INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS》

Image-based 3D treatment planning for vaginal cylinder brachytherapy: dosimetric effects of bladder filling on organs at risk.

To investigate the dosimetric effects of bladder filling on organs at risk (OARs) using three-dimensional image-based treatment planning for vaginal cylinder brachytherapy. Twelve patients with endometrial or cervical cancer underwent postoperative high-dose rate vaginal cylinder brachytherapy. For three-dimensional planning, patients were simulated by computed tomography with an indwelling catheter in place (empty bladder) and with 180 mL of sterile water instilled into the bladder (full bladder). The bladder, rectum, sigmoid, and small bowel (OARs) were contoured, and a prescription dose was generated for 10 to 35 Gy in 2 to 5 fractions at the surface or at 5 mm depth. For each OAR, the volume dose was defined by use of two different criteria: the minimum dose value in a 2.0-cc volume receiving the highest dose (D(2cc)) and the dose received by 50% of the OAR volume (D(50%)). International Commission on Radiation Units & Measurements (ICRU) bladder and rectum point doses were calculated for comparison. The cylinder-to-bowel distance was measured using the shortest distance from the cylinder apex to the contoured sigmoid or small bowel. Statistical analyses were performed with paired t tests. Mean bladder and rectum D(2cc) values were lower than their respective ICRU doses. However, differences between D(2cc) and ICRU doses were small. Empty vs. full bladder did not significantly affect the mean cylinder-to-bowel distance (0.72 vs. 0.92 cm, p = 0.08). In contrast, bladder distention had appreciable effects on bladder and small bowel volume dosimetry. With a full bladder, the mean small bowel D(2cc) significantly decreased from 677 to 408 cGy (p = 0.004); the mean bladder D(2cc) did not increase significantly (1,179 cGy vs. 1,246 cGy, p = 0.11). Bladder distention decreased the mean D(50%) for both the bladder (441 vs. 279 cGy, p = 0.001) and the small bowel (168 vs. 132 cGy, p = 0.001). Rectum and sigmoid volume doses were not affected by bladder filling. In high-dose rate vaginal cylinder brachytherapy, treatment with a distended bladder preferentially reduces high dose to the small bowel around the vaginal cuff without a significant change in dose to the bladder, rectum, or sigmoid.

Hung J ，Shen S ，De Los Santos JF ，Kim RY ... -  《-》