Microdosimetric analysis of radiation from a clinical mammography machine using realistic breast phantoms and a miniature proportional counter.

We have measured the microdosimetric spectra of a Senographe 600T mammography machine employing an Mo target with 0.8 mm Be inherent filtration and 0.03 mm Mo added filtration, giving a half-value layer of 0.

Microdosimetric evaluation of relative biological effectiveness for 103Pd, 125I, 241Am, and 192Ir brachytherapy sources.

Purpose: To determine the microdosimetric-derived relative biological effectiveness (RBE) of 103Pd, 125I, 241Am, and 192Ir brachytherapy sources at low doses and/or low dose rates.

Methods And Materials: The Theory of Dual Radiation Action can be used to predict expected RBE values based on the spatial distribution of energy deposition at microscopic levels from these sources. Single-event lineal energy spectra for these isotopes have been obtained both experimentally and theoretically.

Photoneutrons from high energy medical linear accelerators: measurement of the spectrum and dose using a miniature proportional counter.

Purpose: A new method of measuring photoneutron dose to the patient during treatment with high energy photon or electron beams is presented. This method has the advantage of providing not only the dose, but the microdosimetric spectrum at the same time.

Methods And Materials: A miniature cylindrical gas proportional counter (0.

Microdosimetry for boron neutron capture therapy.

Preclinical studies for boron neutron capture therapy (BNCT) using epithermal neutrons are ongoing at several laboratories. The absorbed dose in tumor cells is a function of the thermal neutron flux at depth, the microscopic boron concentration, and the size of the cell. Dosimetry is therefore complicated by the admixture of thermal, epithermal, and fast neutrons, plus gamma rays, and the array of secondary high-linear-energy-transfer particles produced within the patient from neutron interactions.

Evaluation of an iron-filtered epithermal neutron beam for neutron-capture therapy.

An epithermal neutron filter using iron, aluminum, and sulfur was evaluated to determine if the therapeutic performance could be improved with respect to aluminum-sulfur-based filters. An empirically optimized filter was developed that delivered a 93% pure beam of 24-keV epithermal neutrons. It was expected that a thick filter using iron with a density thickness greater than 200 g/cm2 would eliminate the excess gamma contamination found in Al-S filters.