Modeling the National Ignition Facility neutron imaging system.

Numerical modeling of the neutron imaging system for the National Ignition Facility (NIF), forward from calculated target neutron emission to a camera image, will guide both the reduction of data and the future development of the system. Located 28 m from target chamber center, the system can produce two images at different neutron energies by gating on neutron arrival time. The brighter image, using neutrons near 14 MeV, reflects the size and symmetry of the implosion "hot spot.

Thermoluminescence of 7LiF in therapeutic high linear energy transfer (LET) charged-particle beams.

The thermoluminescence of the 200 and 260 degrees C peaks of 7LiF has been measured and compared with off-axis dose and depth-dose distributions for three therapeutic high-LET beams: negative pions, helium ions and neon ions. The methods of analysis consisted of both a single-peak analysis and the dual-peak analysis methods of Hogstrom and Irifune and Hoffmann et al. The results indicate that 7LiF, analysed by the dual-peak analysis methods, is potentially useful for extracting total dose, high-LET dose, and beam quality of helium-ion and negative-pion beams.

Pion treatment procedures and verification techniques.

Procedures and techniques developed for the negative pi-meson (pion) radiotherapy program at the Los Alamos Meson Physics Facility, Los Alamos, NM, are reviewed and described. A particular pion patient is followed through the entire planning and treatment sequence to describe CT scanning procedures, bolus and collimator and treatment techniques developed to minimize positioning errors (less than 5 mm). Comparison of 2-D and 3-D isodose calculations developed at Los Alamos showed differences of less than 10% attributable to multiple scattering effects and the computational models used.

A lyoluminescent tissue-equivalent dosemeter for pion therapy beams.

The light emitted when pion irradiated glucose is dissolved in luminol solution has been found to be proportional to the pion beam depth dose distribution in water as determined by a TE ionisation chamber. The lyoluminescence of glucose overlaps very closely with the response profile of the ionisation chamber to the 170 MeV/c pi--mesons giving a Bragg peak to plateau ratio of 3:1. In comparison, the thermoluminescence response of LiF (TLD-700) to pions has been found to deviate significantly from this ratio.

Mailed thermoluminescent dosimetry reviews in radiation therapy.

The six Centers for Radiological Physics performed periodic thermoluminescent dosimetry (TLD) reviews for photon beams at 276 facilities across the country. The purpose of the reviews and the techniques in use are briefly described. Results from 2413 mailed reviews of megavoltage units indicate that, in 92% of the reviews, a specified dose was delivered within +/- 5% of the TLD-measured dose.