Therapeutic uses of X-rays

The proton treatment center at Loma Linda University Medical Center: rationale for and description of its development

Proton radiation, a continuation of radiation oncology's historic search for an optimum dose distribution, offers superior characteristics for clinical radiation therapy. A complete facility for clinical proton radiation therapy has been designed for and constructed at Loma Linda University Medical Center. To bring about this achievement, a consortium of engineers, physicists, and physicians interested in the clinical applications of protons was necessary. The accelerator, the beam transport and delivery systems, the building, and the personnel who operate the system were all brought together to fully exploit the properties of protons for patient treatments, which are now underway.

Effects of gamma radiation on the in vitro wear of composite restorative materials

The effects of gamma radiation at therapeutic dosage levels on the wear of three anterior (two light-cured and one autocured) composites and a light-cured posterior composite were studied in vitro. Specimens were subjected to successive sets of 100 abrades to a maximum of 500 abrades on a reciprocating arm abrader, with the dimensional change being recorded between the sets of abrades. The data showed that there were no significant effects on the wear rates of any of the materials tested. The rate of height loss was similar for the two hybrid composites tested (P less than 0.05), as was that for the microfilled and conventional material (P less than 0.05). There was, however, a significant difference (P greater than 0.001) in the wear behaviour between the two groups.

The effects of gamma radiation on the properties of composite restorative resins

The effects of gamma radiation at therapeutic dosage levels on the physical properties of three anterior (two light-cured and one autocure) composites and a light-cured posterior composite were studied. Gamma radiation had no effect on the autocured composite but had varied effects on the light-cured systems. The diametral tensile strength and dimensional stability were unaffected, water sorption and solubility were reduced but surface and bulk hardnesses were increased with the hardness increases linearly related to the radiation dosage. These effects may arise from continued polymerization of the air-inhibited surface layer and possibility of low molecular weight entities within the matrix. Overall, therapeutic levels of gamma radiation had no detrimental effects on the physical properties of the composite resins.