Life exposure to 226Ra and possible consequences.

This paper presents a model of continuous exposure to 226Ra by water consumption over a 55-year period. The effects of 226Ra concentration in drinking water were investigated. Reaching the peak at the age of 16, the assessed effective dose has shown that children are more sensitive to radiation than adults. It has been found that consumption of 226Ra-rich water during certain period of life increases consequent effective doses. The earlier the exposure, the higher amount of 226Ra could be retained causing the higher values of effective dose later in life. However, long-term exposure to 226Ra in drinking water as well as consumption of 226Ra-rich water during a certain period of life does not indicate the appearance of malignant diseases in the year of exposure and later in adults.

A simple calibration method for 106Ru-106Rh eye applicators.

Ru-Rh eye applicators are used for the radiotherapy of eye malignancies such as melanomas. We present a method of dosimetry of these beta particle emitting applicators. Method is based on a Plexiglas phantom (constructed for this purpose) containing spherical shells and very small, 1x1x1mm3 thermoluminescent dosimeters (TLD) as dosimeters. We determined 3-D depth doses and interpolated depth dose functions. Surface dose rate inhomogeneities and the consequences were considered and discussed. A possible influence of photon component of the emission on the results was analysed. The method has overall combined uncertainty + or -6% which is comparable, and slightly better, than other recent dosimetric methods.

Model of total skin electron treatment using the 'six-dual-field' technique.

During implementation of the total skin electron treatment, using six-dual-field technique, at radiotherapy department a large number of measurements are needed. To assess depth dose curve required by clinicians and dose uniformity over a whole treatment plane, combinations of different irradiation parameters are used (electron energy, beam angle, scatterers). Measurements for each combination must be performed. One possible way to reduce number of measurements is to model the treatment using the Monte Carlo simulation of electron transport. We made a simplified multiple-source Monte Carlo model of electron beam and tested it by comparing calculations and experimental results. Calculated data differs less than 5 percent from measurements in the treatment plane. During the treatment patient can be approximated using cylinders with different diameters and orientations. We tried to model the depth dose variations in the total skin electron treatment not just around the body cross-section (simplified to cylinders of different diameters), but also along the body to account for the variations in body curvature longitudinally. This effect comes down to the problem of modeling distribution in different cylinders, but varying the longitudinal orientation of those cylinders. We compared Monte Carlo calculations and film measurements of depth dose curves for two orientations of the cylindrical phantom, which were the simplest for experimental arrangement. Comparison of the results proved accuracy of the model and we used it to calculate depth dose curves for a number of other cylinder orientations.

Allogeneic stem cell transplantation in treatment of aggressive lymphomas: case series.

AIM: To assess the outcome of allogeneic stem cell transplantation in patients with aggressive lymphoma. METHODS: Between 1991 and 2002, 22 patients with aggressive lymphoma in advanced phase of the disease underwent allogeneic stem cell transplantation at the Division of Hematology, Zagreb University Hospital Center. Seventeen patients received stem cells from the bone marrow. Eighteen patients underwent total body irradiation and received cyclophosphamide for conditioning, whereas the rest of the patients received busulfan and cyclophosphamide (n=2) or chemotherapeutic protocol combining carmustine, melphalan, etoposide, and cytarabine (BEAM regimen) (n=2). All patients received cyclosporin and short methotrexate for the prophylaxis of graft-versus-host disease (GVHD). RESULTS: Three months after allotransplantation, 17 patients had complete remission, 3 patients had active disease, and the outcome in 2 patients was early death. Nine patients were alive and in complete remission for 4 to 124 months, whereas 13 patients died (8 because of disease progression and 3 because of GVHD and infection). The probability of overall survival at 4 years was 47%. CONCLUSION: Allogeneic transplantation is an effective therapy for advanced aggressive lymphoma. Because of high treatment-related toxicity and mortality, prospective trials are needed to asses the best time when to apply this treatment.

A dosimetric method of total body irradiation.

The determination of the dose delivered to the body during Total Body Irradiation (TBI) is not easy, as direct measurements are impossible. This article presents the intention to develop a systematic and simple method for absorbed dose determination in(60)Co TBI using mid plane dose factors (MDF) and external measurements, i.e. entrance and exit dose readings by semiconductor detectors. In order to perform the radiation field analysis prior to TBI treatment, a special silicon n-type detector with increased sensitivity (1200 nC/Gy) was used. The dependence of the calibration factor of this detector exposed to different dose rates in standard and TBI conditions was investigated. A theoretical model of anthropomorphic phantoms of cylindrical ellipsoid shape was established. The software made it possible to generalize the applicability of TBI dosimetry to any individual case of real patient data. A quality assurance analysis of dosimetric results of 350 patients, who underwent TBI during a 17-year period, was performed.