Dose Measurements in the Build-Up Region for the Photon Beams from Clinac-1800 Dual Energy Medical Linear Accelerator

Abstract

The increase in surface dose with field size for both photon energies is due to the electron scattering from the intervening materials. The use of wedge filters absorbs low-energy scattered electrons significantly and hence, the relative surface dose (RSD) is always less than unity. The increase in dose enhancement percentage with graphite compared to perspex supporting assembly indicates that the electron backscatter is proportional to the atomic number of the medium.

Vitiligo at the Sites of Irradiation in a Patient with Hodgkin's Disease

“…It was remarkable that the skin irradiated for the paraaortic field, receiving 30 Gy, showed complete depigmentation only in the lumbar region, which had direct contact to the irradiation table, while upper regions were depigmentated only partially reflecting the decrease of depth of the dose build-up region [15] in completely depigmentated areas. As vitiligo in general is caused by melanocyte depletion our observations could indicate an increased radiosensitivity of this cell type in this disorder [20].…”

Autorenschaft wissenschaftlicher Veröffentlichungen Analyse der Zeitschrift “Strahlentherapie und Onkologie”

“…In den untersuchten Jahrgängen gab es 14 Publikationen mit nur einem einzigen Autor [21,36,38,66,69,80,86,88,100,111,117,135,141,158]. Insgesamt 20 Publikationen hatten zwei Autoren [8,9,28,37,50,65,78,103,109,114,116,123,124,148,149,150,151,157,163,164], 21 Publikationen drei Autoren [6,20,35,40,41,42,43,52,70,73,74,75,112,122,126,127,132,…”

Analytical Consideration of Surface Dose and Kerma for Megavoltage Photon Beams in Clinical Radiation Therapy

“…With an increasing energy of these radiations, the penetration power of photons and secondary electrons will be increased and as a result the point of maximum dose (d_max) is placed in more depth (Apipunyasopon et al, 2013).Depending on the amount of energy, dose build up region occurs for x-rays megavoltage in the first depths of the entrance surface of phantom or skin. Dose build up region are a causes the skin sparing effect in megavoltage beams and makes them suitable for delivering the lethal dose to deep tumors as well as reaching the lowest dose in the surface layers of the skin (Butson et al, 1997;Ravikumar and Ravichandran, 2000). On the other hand, low-energy photons and electron contamination causes an increase in the dose of skin, and loss or decrease in the skin sparing effect in the treatment with megavoltage beams (Ravikumar and Ravichandran, 2000).…”

“…Dose build up region are a causes the skin sparing effect in megavoltage beams and makes them suitable for delivering the lethal dose to deep tumors as well as reaching the lowest dose in the surface layers of the skin (Butson et al, 1997;Ravikumar and Ravichandran, 2000). On the other hand, low-energy photons and electron contamination causes an increase in the dose of skin, and loss or decrease in the skin sparing effect in the treatment with megavoltage beams (Ravikumar and Ravichandran, 2000).…”