Skin dose during radiotherapy: a summary and general estimation technique

Abstract

The skin dose associated with radiotherapy may be of interest for clinical evaluation or investigating the risk of late effects. However, skin dose is not intuitive and is difficult to measure. Our objectives were to develop and evaluate a general estimation technique for skin dose based on treatment parameters. The literature on skin dose was supplemented with measurements and Monte Carlo simulations. Using all available data, a general dosimetry system was developed (in the form of a series of equations) to estimate skin dose based on treatment parameters including field size, the presence of a block tray, and obliquity of the treatment field. For out‐of‐field locations, the distance from the field edge was also considered. This dosimetry system was then compared to TLD measurements made on the surface of a phantom. As compared to measurements, the general dosimetry system was able to predict skin dose within, on average, 21% of the local dose (4% of the normalDmax dose). Skin dose for patients receiving radiotherapy can be estimated with reasonable accuracy using a set of general rules and equations.PACS numbers: 87.53.‐j, 87.53.Bn, 87.55.ne

AAPM TG158: Measurement and calculation of doses outside the treated volume from external‐beam radiation therapy

“…Erythema, desquamation, and necrosis can all be observed in contemporary radiotherapy . These effects are largely limited to areas of the skin within the treatment field as these skin doses are higher than outside the treatment field . Correspondingly, more attention is given to the skin dose within the field.…”

Monte Carlo based investigations of electron contamination from telecobalt unit head in build up region and its impact on surface dose

“…The variation of percentage surface dose with field size is shown in figure 7 at SSD of 60 cm and 80 cm. Moreover, the figure also shows the previously published surface dose results (1)(2) . Gerbi et al [5] have used extrapolation chamber for the measurement of surface dose of AECL Eldorado and Cobalt-60 unit.…”

“…The results are compared with the already published measurements of Cobalt-60 beam [27]. From literature survey, it is clear that extensive research has been carried out to measure surface dose of telecobalt unit [3,[5][6][7][8][9][10][25][26][27] as well as medical linear accelerator [1,11,12,21,22,[28][29][30]. The researchers have used different measurement techniques such as extrapolation chamber [5], parallel plate chamber [5,6,7], TLD [5,7,8], Gafchromic films [13][14][15][16][17][18][19][20][21][22], MOSFET [31,32].…”

“…One of the most common side effects of radiation is acute skin reaction which can range from mild erythema to confluent moist desquamation and occasionally, ulceration [1,2]. Radiation skin reactions occur as a result of damage to the basal cell layer of the skin and the resultant imbalance between the normal production of cells in this layer and the destruction of cells at the skin surface [2,3].…”

“…Because of undulations in the basal cell layer and also because of the finite thickness of its cells, a range of 50-100 µm is appropriate for specifying the depth of the sensitive layer of most parts of the skin. For practical dose assessment the International Commission on Radiological Protection (ICRP) recommends the use of a depth of 70 µm as a reasonable mean value, which corresponds to the boundary between the dermis and epidermis layers of the skin [4], while the dermal layer may be assessed at 1.0 mm [1].…”