Design and testing of indigenous cost effective three dimensional radiation field analyser (3D RFA).

The aim of the study is to design and validate an indigenous three dimensional Radiation Field Analyser (3D RFA). The feed system made for X, Y and Z axis movements is of lead screw with deep ball bearing mechanism made up of stain less steel driven by stepper motors with accuracy less than 0.5 mm. The telescopic column lifting unit was designed using linear actuation technology for lifting the water phantom. The acrylic phantom with dimensions of 800 x 750 x 570 mm was made with thickness of 15 mm. The software was developed in visual basic programming language, classified into two types, viz. beam analyzer software and beam acquisition software. The premeasurement checks were performed as per TG 106 recommendations. The physical parameters of photon PDDs such as Dmax, D10, D20 and Quality Index (QI), and the electron PDDs such as R50, Rp, E0, Epo and X-ray contamination values can be obtained instantaneously by using the developed RFA system. Also the results for profile data such as field size, central axis deviation, penumbra, flatness and symmetry calculated according to various protocols can be obtained for both photon and electron beams. The result of PDDs for photon beams were compared with BJR25 supplement values and the profile data were compared with TG 40 recommendation. The results were in agreement with standard protocols.

Transperineal low-dose rate iridium-192 interstitial brachytherapy in cervical carcinoma stage IIB.

PURPOSE: To assess local control, survival and complications in patients with cervical carcinoma Stage IIB treated radically with transperineal Iridium-192 low-dose rate interstitial brachytherapy following external beam radiotherapy. PATIENTS AND METHODS: 65 women (age 25-70 years, mean 47 years) with cervical carcinoma Stage IIB were initially treated with external beam radiotherapy on a telecobalt or 6 MV linear accelerator to a dose of 50 Gy delivered in 5-6 weeks. After 2-3 weeks of completing external radiation, patients received interstitial brachytherapy with Iridium-192 (activity 0.5-1 mCi/cm) using a Syed-Neblett perineal template. The median dose delivered to the implant volume was 24 Gy (range 20-32 Gy) delivered at an average dose rate of 0.70 Gy/h (range 0.40-1.20 Gy/h). A point defined at 1.5 cm lateral to the central uterine tandem at the level of os was taken as a representative for assessing the dose to the cervix. Mean doses delivered by interstitial brachytherapy to point A, cervix, point B and rectum were 38 Gy, 34 Gy, 16 Gy and 16 Gy, respectively. RESULTS: At a median follow-up of 53 months, the actuarial disease free survival and overall survival for 65 patients at both 5 and 10 years was 64% and 44%, respectively. Response to radiotherapy was a strong predictor of local control with 82% of patients continuing to have pelvic control after initial complete response. Overall, nine (14%) patients had persistent disease, ten (15%) developed a central recurrence after initial control and three patients developed distant metastasis on follow-up. No patient had any immediate treatment-related complication. Late toxicity included grade I-II rectal reactions in five patients and grade IV bladder complication (vesico-vaginal fistula) in two patients. 5 years after treatment, one patient developed intestinal obstruction, which was relieved after conservative management. Two patients developed vaginal stenosis. The 5- and 10-year disease free survival was 48% in patients aged less than 45 years as compared to 80% in patients of more than 45 years (p = 0.009). Dose to the cervical point was a prognostic indicator with 5- and 10-year disease free survival of 47% in patients who received < 35 Gy in comparison to 80% in patients who had > 35 Gy (p = 0.03). There was no difference in local control and survival in patients with minimal and moderate parametrial involvement. Bulky disease (> 4 cm) at presentation and a longer gap between external radiation and brachytherapy showed a trend towards inferior local control. CONCLUSIONS: Interstitial brachytherapy after external beam irradiation in patients with cervical carcinoma Stage IIB results in acceptable local control, survival and complication rates. Increased dose to the cervical disease results in improved local control and survival and should therefore be considered while optimizing brachytherapy treatment plans. Comparison of the results with those of standard intracavitary therapy remains to be proven in a randomized trial.

Late esophageal toxicity using a combination of external beam radiation, intraluminal brachytherapy and 5-fluorouracil infusion in carcinoma of the esophagus.

One hundred patients with potentially curable squamous cell carcinoma of the esophagus were treated using a combination of external beam radiation, medium-dose intraluminal brachytherapy (ILBT), and 5-fluorouracil infusion (as a radiosensitizer) from January 1990 to December 1993. The main objective was to determine late toxicity and optimization of the dose of intraluminal radiation. All patients had external radiation of 50 Gy over 5 1/2 weeks, followed by ILBT of 20 Gy for 50 patients (group 1) and 15 Gy for a subsequent 50 patients (group 2), using a dose rate of 315-330 cGy/h with the prescription at 1 cm off axis. The 5-fluorouracil infusion was 500 mg/m2 administered 12 h prior to ILBT. The treatment-related complications among groups 1 and 2 were strictures 24% vs. 8% (p = 0.029), ulceration 30% vs. 28% (p = 0.8), and tracheoesophageal fistulae 12% for both groups. The overall survival for groups 1 and 2 was 8% and 23% at 5 years. The development of life-threatening complications is a major concern and extreme caution is urged before selecting patients for a combination of ILBT and 5-fluorouracil treatment.

Treatment volume from total reference air kerma (TRAK) in intracavitory applications and its comparison with ICRU reference volume.

PURPOSE: A systematic dosimetry study conforming to International Commission on Radiation Units and Measurements Report Number 38, was carried out for, cancer of Cervix Stage I and II cases at Tata Memorial Hospital. METHODS AND MATERIALS: The reference Volume dimension were noted for each applicator. Also 3-D dosimetry was performed for selected cases, and actual geometric volume enclosed by various isodose surfaces were obtained. A relation was derived, which gave the volume enclosed by any isodose surface as a function of total reference air kerma of the sources in the applicator. The volume enclosed by reference isodose surface was compared with the product of its dimensions height, width, and thickness. RESULTS: The volume enclosed by any isodose surface of an intracavitary application can be easily derived from total reference air kerma of the sources within the applicator. CONCLUSION: Ratio of the volume enclosed by reference isodose surface with the product of its dimensions (HWT) could be a predictive parameter for clinical outcome, besides the reference volume specified by the report.