We have considered the thermal equilibrium in pre-protostellar cores in the approximation where the dust temperature is independent of interactions with the gas and where the gas is heated both by collisions with dust grains and ionization by cosmic rays. We have then used these results to study the stability of cores in hydrostatic equilibrium in the limit where thermal pressure dominates over...

Radiation therapy is a viable option in managing potentially life-threatening malignancies including prostate cancer. It is known that pelvic radiation can result in injury of the distal large bowel with the development of radiation proctitis. Despite reports from retrospective studies, there is a lack of direct endoscopic and histologic evidence of external pelvic radiation injury to the ileal...

the primary treatment of thyroid carcinoma is surgery and the outcome depends on its extent. the post-operative management alternatives in thyroid carcinoma include thyroid hormone, radio-iodine ablation (i-131 na), external beam radiation therapy (ebrt) and occasionally adjuvant chemotherapy. this retrospective study analyzes the managements of 153 patients (102, 51), age range 10-96 years, me...

introduction intensity-modulated radiotherapy (imrt) is becoming an increasingly routine treatment method. imrt can be delivered by use of conventional multileaf collimators (mlcs) and/or physical compensators. one of the most important factors in selecting an appropriate imrt technique is integral dose. integral dose is equal to the mean energy deposited in the total irradiated volume of the p...

PURPOSE To estimate the α/β ratio of prostate cancer treated with external beam radiation only by use of a model of long-term prostate-specific antigen (PSA) dynamics. METHODS AND MATERIALS Repeated measures of PSA from 5,093 patients from 6 institutions treated for localized prostate cancer by external beam radiation therapy (EBRT) without planned androgen deprivation were analyzed. A biphas...

all living organisms are exposed to ionizing radiation comprising cosmic rays coming from outer space, terrestrial nuclides occurring in the earth’s crust, building materials, air, water and foods and in the human body itself. the exposures are constant and uniform for all individuals everywhere including the dose from ingestion of 40k in food. cosmic rays are, more intense at higher altitudes,...

Technologic advances in radiation treatment planning and delivery have generated popular interest in the different radiation therapy techniques used in treating patients with localized prostate cancer. Throughout the past decade, high-energy (> 4 MV) linear accelerators have largely replaced Cobalt machines in external beam radiation therapy (EBRT) delivery. Conventional EBRT has been used to t...

The development of radionuclide therapies during the past few decades provides a growing body of data on radiobiologic effects, including normal tissue toxicities and antitumor efficacy. Information on normal tissue toxicity from radionuclides is more limited than that from external beam radiation and appears to be more variable. Much of the increased variability is attributed to heterogeneous ...

In addition to inducing lethal DNA damage in tumor and stromal cells, radiation can alter the interactions of tumor cells with their microenvironment. Recent technological advances in planning and delivery of external beam radiotherapy have allowed delivery of larger doses per fraction (hypofractionation) while minimizing dose to normal tissues with higher precision. The effects of radiation on...