RESUMEN
PURPOSE: An evaluation of CT plan data, using cylinder applicators, in fractionated HDR treatments of cervical cancers has been investigated in this clinical study. Critical and statistical analysis of the data, for each patient and fraction, for plan dose, doses for bladder and rectum have been enumerated and reported. Plans were done for each patient, following CT scans after insertion of the applicator in the respective cases. This process involved time for CT-scan and re-plan, in each fraction, adding cost of treatments for the poor patients. MATERIAL AND METHODS: This study on HDR brachytherapy for cervical cancer patients has applied the Co-60 BEBIG Multisource Unit. Cylinder applicators have been applied for treatments. A selection of twenty nine patients, out of a few hundred representative female patients, in the age group of 40-70 years, has been analyzed and presented in this paper. Radiation oncologists inserted the applicator and fixed it in more than 600 treatments. This study, therefore, aimed at their insertion technique, CT-planning by radiation oncology physicists and the delivery of the treatments. Details of set up and technique has been explained, where bladder and rectum doses has been assessed within the tolerance limit [1]. RESULTS: Statistical analysis of data from the treatment plans, substantiates the conclusion of the argument that there is no need to do CT-plans for each subsequently prescribed number of fractions as the doses in plan, bladder and rectum are restricted within the limits of tolerance. Data in Table 1 are analyzed in various graphs. This utilized the Empirical Null Distribution of Group Differences. A graphic study of dose distribution is reported to assure the expected variation of dose from the central tandem. This analysis proves to substantiate a protocol that no re-plan for fractionated delivery is essential following the approval of the first plan. CONCLUSIONS: The goal of this study was to critically evaluate the outcome of fractionated cylinder treatments of cervical cancers. This resulted in the set up technique for insertion of applicators and treatment plan, following a CT-scan and the assertion of the argument that re-plans are not necessary for multiple HDR cylinder treatments for the same patient [2, 3].
RESUMEN
PURPOSE: The report presents an extraordinary synthesis of customer acceptance procedures (CAP), quality assurance tests (QA) in the treatment of cervical cancer patients, using the first Co-60 Multisource Unit® in Bangladesh. The QA and commissioning required measurements and emergency tests verifying the functional limits of parameters acceptable for the new HDR afterloader. Acceptable limits were: 1) the deviation between specified and measured source strength: ± 3%; 2) the positional accuracy and uniformity: ± 1 mm; 3) the temporal accuracy (i.e. timer error and linearity and end error): ± 1% or 30 sec.; 4) treatment planning system (digitizer and localization software): ± 3% or 1 mm; 5) the distance from line to first dwell position and all the others: 5 mm and 10 mm (± 1 mm). MATERIAL AND METHODS: Till February 2011, 47 patients were treated with HDR with more than 140 insertions applied. Amongst them, 12 patients were in stage IIB and IIIB, 22 were postoperative (IA and IB) while the remaining 13 patients were with unknown stage. All the cases with stage IIB and IIIB received concurrent chemo-radiation and brachytherapy. Postoperative patients received EBRT (50 Gy and HDR) according to the institutional protocol. CT scans were completed before HDR-plus planning with a good reproducibility (± 2%) and were documented in repeating the plan for the same set up of a patient. Absorbed dose (Gy) to a point P, at a distance of "r" in centimeters from a source of the Reference Air Kerma Rate (RAKR) has been utilized for the QA of the source, where source strength measurement was accomplished. RESULTS: All methods and analysis applicable to the QA and commissioning of Co-60 have been investigated and systematically analyzed, measured and documented before the treatment of a patient. Studies and safety requirements of this HDR remote afterloader were carried out. Acceptance and the QA were imperative to justify functionality and dependability in delivering the treatment. Implications of these studies were described in detail in this paper, where equipments and guidelines of measurement parameters are enunciated. CONCLUSIONS: We noted that contouring structures from CT images, prescription points for dose delivery, optimization, isodose evaluation, DVH, dwell times and a 3-D Dose reconstructed images, etc. followed by a final verification after delivering the treatment at the console, are well prepared in the new planning software. We present our material as an early preliminary report.