The gamma-ray dose component of a d(80) + Be neutron beam was measured with a 6Li-shielded Geiger-Mueller counter in a tissue-equivalent liquid phantom. The proportion of gamma-ray dose to total dose increased from 0.07 near the surface to 0.09 at 25 cm depth. Due to thermal neutron sensitivity, the G-M count rate increased by 25% in the absence of 6Li shielding.

Fast Neutrons↗

PubMedDate not supplied

Dosimetric properties of p(90)+(Be + Ta) and p(101)+(Be + Al) neutrons.

Dosimetric data were obtained for p(90) + (Be + Ta) and p(101) + (Be + A1) radiation with field size 9 x 11 cm at a 125-cm SSD impinging on a tissue-equivalent liquid phantom with density 1.10. The radiation was unfiltered or filtered by 10 cm of polyethylene. Dose rates measured with a 0.5-cm3 ion chamber at a depth of 5 cm ranged from 0.046 Gy min-1 microA-1 for filtered p(90) + (Be + Ta) to 0.11 Gy min-1 microA-1 for unfiltered p(101) + (Be + A1). Neutron time of flight energy spectra in air averaged above 10 MeV indicate mean neutron energies ranging from 42.0-51.4 MeV for the four beams under study. The central axis depths at which 50% dose attentuation occurred ranged from 15 to 20 cm for these beams. At 3 cm depth the gamma dose component of the total p(101) + (Be + A1) dose was 14.5%, or 17% with filtration.

Fast Neutrons↗

PubMedDate not supplied

Ultrasound hyperthermia applicators: intensity distributions and quality assurance.

Intensity plots at several depths in water were obtained with three ultrasound hyperthermia applicators (Clinitherm, Mark VII), each with a single plane circular ceramic transducer element. One of the applicators exhibited an anomalous localized intensity maximum 3 cm away from the central beam axis. This observation, and the fact that transducer efficiency and field patterns may change with time and use, suggest quality assurance enhancement through periodic checks of output distributions of ultrasonic applicators for clinical use.

Evaluation Studies as Topic↗