Dosimetric validation of the MCNPX Monte Carlo simulation for radiobiologic studies of megavoltage grid radiotherapy.

Purpose: To validate the MCNPX Monte Carlo simulation for radiobiologic studies of megavoltage grid radiotherapy.

Methods And Materials: EDR2 films, a scanning water phantom with microionization chamber and MCNPX Monte Carlo code, were used to study the dosimetric characteristics of a commercially available megavoltage grid therapy collimator. The measured dose profiles, ratios between maximum and minimum doses at 1.

Therapeutic advantage of grid irradiation for large single fractions.

Purpose: In the present work, we used model calculations of cell survival to compare the effects of single fraction high-dose grid therapy with those of uniform dose delivery on tumor and normal tissues.

Methods And Materials: The grid consisted of a hexagonal pattern of divergent holes in a Cerrobend block. A linear-quadratic model was used to find the surviving fraction of tumor and normal tissue cells after high-dose irradiation.

Partial breast brachytherapy after lumpectomy: low-dose-rate and high-dose-rate experience.

Purpose: The use of partial breast brachytherapy (PBB) after lumpectomy for selected patients with early-stage breast cancer reduces the adjuvant radiotherapy treatment time to <1 week. Despite the advantages of accelerated treatment, maintaining an acceptable cosmetic outcome is important. In a cohort of patients who received low-dose-rate (LDR) or high-dose-rate (HDR) PBB after lumpectomy, the clinical characteristics and treatment parameters were analyzed to identify predictors for an unfavorable cosmetic outcome.

The effect of high-dose-rate brachytherapy dwell sequence on cell survival.

Purpose: During a high-dose-rate (HDR) brachytherapy treatment, as the source steps through different dwell positions, the dose rate at any fixed point within the implant varies, because the distance between the point and the source continually changes. The instantaneous dose rate may vary by a factor of 100 or more, in a complex dwell position sequence. Two different points which receive the same total dose may have received that dose with a very different sequence of dose rates.