Jerald W. Hilbert

HIGH-ENERGY PROTON DEPTH-DOSE PATTERNS.

The deposition of energy by monoenergetic unidirectional proton beams incident on polystyrene was investigated. Center-line depth-dose curves were established for protons having energies of 730 MeV...

Changes in the frequency distribution of energy deposited in short pathlengths as a function of energy degradation of the primary beam.

The frequency distributions of event size in the deposition of energy over small pathlengths have been measured after penetration of 44.3 MeV protons through various thicknesses of tissue-equivalent material. These distributions have been measured over a range of penetration extending from zero thickness to thicknesses of muscle-equivalent plastic close to that corresponding to the total range of the protons. These distributions are those associated with the passage of the proton through

Frequency distributions of energy loss by fast charged particles after passage through large thicknesses of tissue-equivalent materials.

0.667\times 10^{-4}\ {\rm g}/{\rm cm}^{2}

ENERGY DEPOSITION IN MICROSCOPIC VOLUMES BY HIGH-ENERGY PROTONS.

of a tissue-equivalent gas. The transition from the region where statistical fluctuations dominate to that where a significant spread in beam energy has taken place is clearly demonstrated. In no instance does it appear that the concept of dose based upon a value of the stopping power or average energy deposited adequately defines the energy delivered to a structure having the dimensions usually associated with those of biological significance if only a relatively small number o...

Frequency distributions of energy deposition by 44 MeV protons at bone-soft tissue interfaces

Frequency distributions of the energy deposition by 600 MeV protons in small volumes as a result of their traversal of a tissue-equivalent gas have been measured after the beams passage through various thicknesses of a tissue-equivalent plastic. The pathIength examined is equivalent to 1.75 ,u of unit density tissue (muscle). Comparisons of the energy deposition distribution functions after passage through 0, 5 and 21 cm of tissue-equivalent plastic (muscle) are given. Through the use of a coincidence gate, spectra depicting energy deposition due only to direct proton ionization in the gas were compared with those combined with contributions due to the nuclear interaction products.

FRACTIONATED INTRACAVITARY RADIATION THERAPY WITH THE BRACHYTRON: GENERAL TECHNIQUES AND PRELIMINARY RESULTS IN THE TREATMENT OF CERVIX CANCER

Measurements of the frequency distributions of the energy deposited as the result of the passage of high-energy protons through microscopic volumes of biological interest present some unique proble...

STATISTICAL FLUCTUATIONS OF ENERGY DEPOSITED IN LOW-ATOMIC-NUMBER MATERIALS BY 43.7-MeV PROTONS.

The frequency distributions of event size in the deposition of energy produced by the passage of protons in a pathlength of 6.99*10-5 g cm-2 tissue-equivalent gas have been measured after penetration of a 44 MeV monoenergetic proton beam through various amounts of bone and muscle equivalent plastic. Corresponding thicknesses of the absorbers of the two types were chosen such that the mean energy of the residual beam of protons entering the gaseous test volumes were identical. Each pair of absorbers thus produced the same relative ionization density as measured by the Bragg curve. The resultant energy deposition distributions obtained for each pair of the two absorbing materials were identical. This indicates that both primary and forward scattered secondary particle spectra in a degraded beam are not significantly different after the primary beam passes through equivalent amounts of bone or soft tissue. The results obtained on a microscopic scale are in agreement with both calculations of the absorbed dose and dose equivalent under similar conditions and with experimental measurements of absorbed dose.