Area of human body is mass/age dependent. In Radiation Protection, it can (area ) in general be used to convert skin dose to whole body dose in case of non-uniform (shallow) exposure or if some portion of skin receives shallow dose. What are mathematical models which can be used to estimate are area?
Surface area (m2) of the body can be expressed as α0Hα1Mα2 where H is height (cm) and M is mass (kg). The International Commission on Radiological Protection (ICRP) has used α0, α1 and α2 of 0.0235, 0.42246 and 0.51456, respectively, derived by Gehan and George ( https://www.ncbi.nlm.nih.gov/pubmed/5527019 ). The resulting reference values are listed in Table 2.9 of ICRP Publication 89 issued in 2002.
Other papers on the mathematical formulation of the body surface area report 1/6(WH)0.5 ( https://www.ncbi.nlm.nih.gov/pubmed/15696524 ), 71.3989H0.7437W0.4040 ( https://www.ncbi.nlm.nih.gov/pubmed/19900761 ).
The following paper reports that hand surface area (cm2) can be described by 1.219 x hand length (cm) x hand circumference (cm).
@Hamada Sir, Thanks for nice reference. Totally a new information about the methodology.
Currently, effective dose is defined and estimated in a Reference Person. The equivalent doses in the organs and tissues of the Reference Male and the Reference Female are averaged. Then, the sum of the averaged dose multiplied with the corresponding tissue weighting factor yields the sex-averaged effective dose for the Reference Person. These tissue weighting factors are mean values representing an average over many individuals of both sexes. It will be possible to develop a personalized dose coefficients for individual, but the partial employment of the personalized approach may then lead to a departure from the nominal approach.
P.S.
Under development in ICRP are the reference computational phantoms for children of different ages and for the pregnant woman and fetus.
The use of tissue weighting factors (wT) assigned for various organs and tissues is recommended within the framework of the nominal concept (e.g., wT for skin when skin is exposed, and wT for other tissues when other tissues are exposed in addition to the skin).
If I understand your idea correctly, are you considering a set of weighting factors tailored for various parts of the skin considering various organs/tissues beneath each part of the skin as a function of dose distribution and the size of the body/tissue/organs? Such personalized approach would be interesting, but may introduce complexity as radiosensitivity (e.g., to cancer) differs greatly among tissues/organs, with age, and between sexes. Based on the current set of epidemiological evidence, the risk cannot be estimated so accurately for each condition.
Agrees with Prof. Hamada. Wt for skin is only for stochastic effect say skin cancer. For skin redinning which occurs at many Gy Wt does not have much meaning. In radiation protection in field conditions it is difficult to know prospective areas to be exposed as worker is rarely stationery. Philosophy of radiation protection demands simplicity rather than complexity. Low energy photons and beta only deliver skin dose and deeper organs are not at risk. For higher energy photons skin and deep doses are practically equal. Only precautions are required in contamination cases where area needs to be known to some extent.
In fluoroscopy skin dose may be high and according the organ doses will be decided by backscatter and attenuation. Here concept of effective dose is not straight and not much meaning full.
Just to add that wT for skin is based on the nominal risk for non-melanoma skin cancer. Radiation-induced skin cancer is almost exclusively of the basal cell type. Melanoma skin cancer is a typical example where no clear evidence is available for association with radiation exposures (other examples include testicular cancer and chronic lymphocytic leukemia).
Provided below is an example difficulty in estimating fluoroscopy related risks for neighboring tissues/organs. Epidemiological data obtained from multiple chest fluoroscopies for patients with tuberculosis (i.e., fractionated exposures) showed that whereas there was a high risk for breast cancer ( https://www.ncbi.nlm.nih.gov/pubmed/8643829 ), there was no lung cancer risk even at >3 Gy to the lung with a flat dose response (i.e., lack of dose response) ( https://www.ncbi.nlm.nih.gov/pubmed/7761580 ). A similar observation (breast cancer risk with no lung cancer risk) was reported following repeated radiographic examination ( https://www.ncbi.nlm.nih.gov/pubmed/20681802 ).
As the pertinent reference, I suggest ICRP Publication 117.
Cardiovascular disease is categorized in tissue reactions (deterministic effects) by ICRP definition.
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