PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 9725593

Developing a dose-volume histogram computation program for brachytherapy.

E Panitsa·J C Rosenwald·C Kappas
View original source ↗Export metadata ↓

Abstract

A dose-volume histogram (DVH) computation program was developed for brachytherapy treatment planning in an attempt to benefit from the DVH's ability to present graphically information on 3D dose distributions. The program is incorporated into a planning system that utilizes a pair of orthogonal radiographs to localize the radiation sources. DVHs are calculated for the volume of tissue enclosed by an isodose surface (e.g. half the value of the reference isodose). The calculation algorithm is based on a non-uniform random sampling that gives a denser point distribution at the centre of the implants. Our program was tested and proved to be fast enough for clinical use and sufficiently accurate (i.e. computation time of 20 s and less than 2% relative error for one point source, for 100,000 calculation points). The accuracy improves when a larger calculation point number is used, but the computation time also increases proportionally. The DVH is presented in the form of a simple graph or table, or as Anderson's 'natural' DVH graph. The cumulative DVH tables can be used to extract a series of indexes characterizing the homogeneity and the dose levels of the distribution in the treatment volume and the surrounding tissues. If a reference plan is available, the DVH results can be assessed relative to the reference plan's DVH.

Explore related subjects

BrachytherapyComputer SimulationIridium RadioisotopesMathematicsRadiotherapy DosageRadiotherapy Planning, Computer-AssistedReproducibility of ResultsJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

E Panitsa, J C Rosenwald, C Kappas. 1998. Developing a dose-volume histogram computation program for brachytherapy.. https://doi.org/10.1088/0031-9155%2F43%2F8%2F009

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1999

The use and advantages of a multichannel vaginal cylinder in high-dose-rate brachytherapy.

PURPOSE: This paper describes California Endocurietherapy's (CET) high-dose-rate (HDR) multichannel cylinder, the rationale for its design, procedure for its insertion, and the dosimetry involved in its use. A study was done that compared the doses achieved using the CET multichannel cylinder to the same cylinder if it only had a central channel. METHODS AND MATERIALS: The CET multichannel vaginal cylinder was inexpensively constructed, using parts from various suppliers. After insertion in the patient, the cylinder is affixed to a base plate to prevent displacement. Two sets of orthogonal films (without and with rectal barium) are taken in preparation for digitization of the catheters, bladder, rectal, and pelvic sidewall points. Using HDR brachytherapy planning software, the dose distribution is adjusted to achieve the prescribed dose (5 Gy HDR) 5 mm lateral to the cylinder surface, 5 mm lateral at the proximal parametrial tissue, and 4 mm superior to the vaginal apex. Doses to the bladder and rectum are limited to approximately 85% and 75%, respectively, of the prescribed dose. The plan is optimized on geometric parameters. For dose comparison to treatment using a central channel cylinder, the lateral channels are de-activated, leaving only the central channel activated. Dose points are placed 5 mm laterally and superiorly from the cylinder surface, and the plan is optimized to deliver a uniform dose to the defined dose points. The doses and treatment volumes are statistically compared. RESULTS: The CET multichannel cylinder allows much better dose control than the central channel cylinder. The multichannel cylinder achieves lower bladder and rectal doses by 14% and 15%, respectively, when compared to the central channel cylinder. By increasing the dwell times of certain dwell positions, the prescription dose is achieved in the vaginal apex and proximal parametrial tissues and along the length of the cylinder. CONCLUSION: The multichannel cylinder enables more flexibility in isodose shaping and dose control to various points and structures when compared to the conventional central channel cylinder.

Brachytherapy↗
PubMed1999

Factors affecting long-term outcome of irradiation in carcinoma of the vagina.

OBJECTIVE: This report evaluates prognostic and technical factors affecting outcome of patients with primary carcinoma of the vagina treated with definitive radiation therapy. METHODS AND MATERIALS: A retrospective analysis was performed on records of 212 patients with histologically confirmed carcinoma of the vagina treated with irradiation. RESULTS: Tumor stage was the most significant prognostic factor; actuarial 10-year disease-free survival was 94% for Stage 0 (20 patients), 80% for Stage I (59 patients), 55% for Stage IIA (63 patients), 35% for Stage IIB (34 patients), 38% for Stage III (20 patients), and 0% for Stage IV (15 patients). All in situ lesions except one were controlled with intracavitary therapy. Of the patients with Stage I disease, 86% showed no evidence of vaginal or pelvic recurrence; most of them received interstitial or intracavitary therapy or both, and the addition of external-beam irradiation did not significantly increase survival or tumor control. In Stage IIA (paravaginal extension) and IIB (parametrial involvement) 66% and 56% of the tumors, respectively, were controlled with a combination of brachytherapy and external-beam irradiation; 13 of 20 (65%) Stage III tumors were controlled in the pelvis. Four patients with Stage IV disease (27%) had no recurrence in the pelvis. The total incidence of distant metastases was 13% in Stage I, 30% in Stage IIA, 52% in Stage IIB, 50% in Stage III, and 47% in Stage IV. The dose of irradiation delivered to the primary tumor or the parametrial extension was of relative importance in achieving successful results. In patients with Stage I disease, brachytherapy alone achieved the same local tumor control (80-100%) as in patients receiving external pelvic irradiation (78-100%) as well. In Stage II and III there was a trend toward better tumor control (57-80%) with combined external irradiation and brachytherapy than with the latter alone (33-50%) (p = 0.42). The incidence of grade 2-3 complications (12%) correlated with the stage of the tumor and type of treatment given. CONCLUSION: Radiation therapy is an effective treatment for patients with vaginal carcinoma, particularly Stage I. More effective irradiation techniques, including optimization of dose distribution combining external irradiation and interstitial brachytherapy in tumors beyond Stage I, are necessary to enhance locoregional tumor control. The high incidence of distant metastases emphasizes the need for earlier diagnosis and effective systemic cytotoxic agents to improve survival in these patients.

Brachytherapy↗