RADIATION DOSIMETRY A THEORY RADIATION DOSES non-SI units (relationship between units) Dose Formula SI units ΔΕ J/kg = Gray (Gy) Absorbed Dose, rad 1 Gy = 100 rad Δm AE is the energy lost from the radiation beam, and Am is the mass of the material into which the energy is absorbed. ΔQ Roentgen (R) 1R = 2,58 · 104 C/kg Exposure dose, C/kg Δm where AQ is the electric charge freed by such radiation in a specified volume of air divided by the mass Am of that air. Relationship between absorbed dose and exposure dose D = f · X D is adsorbed dose , f is a coefficient depending on the kind of tissue being irradiated. H = Q · D where H is dose equivalent, Q is relative biological effectiveness of a particular kind of radiation, D is adsorbed dose. Equivalent Dose, Sievert rem Н (Sv) 1 Sv =100 rem Effective H ΣΗT Sievert rem 1 Sv =100 rem Equivalent Dose , Hef where HT = Wr · H, is the tissue-weighted dose equivalent to an organ or tissue, H, is the dose equivalent to the organ or tissue and the WT applicable to that organ or tissue. (Sv) Table 1 – Quality factors for different kinds of radiation Table 2 – Dimensionless weighting factors (Wr) Tissue WT Type of Radiation Gonads 0.25 Breast 0.15 х-гаys Red bone marrow 0.12 Lungs Thyroid 0.12 0.03 20 Bone surfaces 0.03 Neutrons (fast) 10 Remainder 0.30 Protons 10 Total body 1.00 1 DOSE RATES 1. Adsorbed dose rate: Np =" Table 3 – Exposure constants Radionuclides k, (µGy-m³/GBq-h at 1 m)" 137CS 99m'Tc 201TI н 2. Dose equivalent rate: Nµ = 88.11 15.95 3. Exposure rate: Nx = 12.16 Exposure rate at a distance r from the source of Mo radiation can be found as 39.46 67GA 20.54 1231 Ny = Y, where is ky is exposure constant for a ky'A 41.89 %3! "In 1251 57CO 131 55.41 given radioisotope, A is activity of the radioactive source, r is distance from the source of the radiation. 37.03 15.16 58.65 18ED 154.05 10. A person with lymphoma receives a dose of 35 Gy in the form of y radiation during a course of radiotherapy. Most of this dose is absorbed in 18 g of cancerous lymphatic tissue. (a) How much energy is absorbed by the cancerous tissue? (b) If this treatment consists of five 15 minute sessions per week over the course of 5 weeks and just 1% of the y photons in the y ray beam are absorbed, what is the power of the y ray beam? (c) If the y ray beam consists of just 0.5% of the y photons emitted by the y source, each of which has an energy of 0.03MeV, what is the activity (in Ci) of the y ray source?

RADIATION DOSIMETRY A THEORY RADIATION DOSES non-SI units (relationship between units) Dose Formula SI units ΔΕ J/kg = Gray (Gy) Absorbed Dose, rad 1 Gy = 100 rad Δm AE is the energy lost from the radiation beam, and Am is the mass of the material into which the energy is absorbed. ΔQ Roentgen (R) 1R = 2,58 · 104 C/kg Exposure dose, C/kg Δm where AQ is the electric charge freed by such radiation in a specified volume of air divided by the mass Am of that air. Relationship between absorbed dose and exposure dose D = f · X D is adsorbed dose , f is a coefficient depending on the kind of tissue being irradiated. H = Q · D where H is dose equivalent, Q is relative biological effectiveness of a particular kind of radiation, D is adsorbed dose. Equivalent Dose, Sievert rem Н (Sv) 1 Sv =100 rem Effective H ΣΗT Sievert rem 1 Sv =100 rem Equivalent Dose , Hef where HT = Wr · H, is the tissue-weighted dose equivalent to an organ or tissue, H, is the dose equivalent to the organ or tissue and the WT applicable to that organ or tissue. (Sv) Table 1 – Quality factors for different kinds of radiation Table 2 – Dimensionless weighting factors (Wr) Tissue WT Type of Radiation Gonads 0.25 Breast 0.15 х-гаys Red bone marrow 0.12 Lungs Thyroid 0.12 0.03 20 Bone surfaces 0.03 Neutrons (fast) 10 Remainder 0.30 Protons 10 Total body 1.00 1 DOSE RATES 1. Adsorbed dose rate: Np =" Table 3 – Exposure constants Radionuclides k, (µGy-m³/GBq-h at 1 m)" 137CS 99m'Tc 201TI н 2. Dose equivalent rate: Nµ = 88.11 15.95 3. Exposure rate: Nx = 12.16 Exposure rate at a distance r from the source of Mo radiation can be found as 39.46 67GA 20.54 1231 Ny = Y, where is ky is exposure constant for a ky'A 41.89 %3! "In 1251 57CO 131 55.41 given radioisotope, A is activity of the radioactive source, r is distance from the source of the radiation. 37.03 15.16 58.65 18ED 154.05 10. A person with lymphoma receives a dose of 35 Gy in the form of y radiation during a course of radiotherapy. Most of this dose is absorbed in 18 g of cancerous lymphatic tissue. (a) How much energy is absorbed by the cancerous tissue? (b) If this treatment consists of five 15 minute sessions per week over the course of 5 weeks and just 1% of the y photons in the y ray beam are absorbed, what is the power of the y ray beam? (c) If the y ray beam consists of just 0.5% of the y photons emitted by the y source, each of which has an energy of 0.03MeV, what is the activity (in Ci) of the y ray source?