Quality assurance for the physical and technical factors affecting treatment planning of head and neck malignancies

In this work the effect of patient immobilization was studied in cases of head and neck malignancies, which treated in the supine position with a cobalt-60 machine at Clinical Oncology Department in Tanta University Hospitals. Four patients were immobilized using orfit and planned on the x-ray diagnosis machine with and without the orfit. Different headrest types were used to detect which of them help in the reproducibility from day to day. Then portal images were obtained to perform weekly "on-line" setup errors. Comparison between manually dose distribution and those calculated using C.T. planning images and calculated by planning system were investigated are done. By measurements and calculation the HORTON's equation of shadow tray factor must be development

Verification of radiation dose calculation for patients treated by Co-60 using 2-D planning system

In this study, experimental verifications is done for output, dose profile percentage depth dose for open and modified [wedged and partially blocked] fields as compared with the calculated using Multidata code. Four typical configurations of irradiation were selected, regular fields, wedged fields, blocked fields and cases of internal inhomogeneity. Measurements were performed on cobalt - 60 unit Theratron 780E using Multidata water phantom. For blocked fields dose profiles were measured using radiographic films and then scanned using PTW densitometer. Data were analyzed in both of the low and high dose gradient regions of the measured and calculated profiles. Differences between the measured and the calculated dose were determined. The results indicate that the Multidata planning system calculations agree with the measured ones in situations. However, in the blocked field the mean deviation between measured and calculated dose under the block was [15.2%] although the blocks is drown according to the instructions by the system manufactures. The reason for such errors was found to be due to the implemented algorithm in the system

practical determination method of potassium traces in foodstuffs by the use of natural [40]k radiation

A new approach is presented for experimental determination of the potassium traces in foodstuffs, soil, sediment and plants, by use of natural [40]K radiation. Potassium maintains the salt balance in plant and animal cells and is important for healthy metabolis. Its role is often likened to that of the oil in an engine. There are actually three potassium isotopes'. [39]K, a stable isotope, is the most abundant, at 93.26% of the total; [41]K is next in abundance at 6.73% and is also a stable isotope. The potassium isotope of interest is a radioactive isotope, [40]K. It is present in all potassium at a very low concentration, 0.0118%. It has a very long half-life, 1,260,000,000 years. When it decays 89% of the events give rise to the emission of a beta ray with maximum energy of 1.33 Mev. The other 11% of the decays produce a gamma ray with an energy of 1.46 Mev. The long half-life and low abundance might seem to imply that this radioisotope, [40]K, is of little or no consequence, so it is usually ignored. In fact the knowledge that all potassium contains this radioactive isotope does not seem to be widely known. Very few of the discussions about potassium mention its radioactivity, which seems to imply that either it is not known or that this trivial level can be safely ignored. This radioactive element is vital for our good health. It is an element that is essential for the body's growth and maintenance. Potassium is also necessary in order to maintain normal water transport between the cells and body fluids. It also plays an essential role in the response of nerves to stimulation and in the contraction of muscles