Mini Review ISSN: 2574 -1241 DOI: 10.26717/BJSTR.2021.33.005413 Comparison of Methods and Systems in Internal Radiation Dosimetry Guy Yembi Goma and Muhammad Maqbool* Health Physics Program, Department of Clinical & Diagnostic Sciences, the University of Alabama at Birmingham, USA *Corresponding author: Muhammad Maqbool, Health Physics Program, Department of Clinical & Diagnostic Sciences, the University of Alabama at Birmingham, USA ARTICLE INFO ABSTRACT Received: January 17, 2021 Exact dose delivery to cancer patients in their treatment by radiation is very Published: January 29, 2021 patients and radiations workers is performed before any dose delivery. A cancer patient canimportant. be exposed Radiation to radiation Dosimetry in twois a ways:specific external area in exposurewhich exact and doseinternal calculation exposure. to External exposure occurs when source of radiation is located and placed outside a Citation: Guy Yembi Goma, Muhammad Maqbool. Comparison of Methods and patient. Internal exposure is due to radiopharmaceuticals taken inside a patient’s body. Systems in Internal Radiation Dosimetry. The area of dosimetry dealing with radiation delivered by external sources of radiation is called external dosimetry and the area in which radiation is obtained from radioactive BJSTR. MS.ID.005413. sources within the body is called internal dosimetry. In this minireview, various methods Biomed J Sci & Tech Res 33(3)-2021. and systems used in the internal dosimetry are analyzed. Comparison of those methods Keywords: Dosimetry; Internal Dosimetry reveals that every method and system has its own advantages and priorities over others Methods; Internal Dosimetry Systems in various cases and circumstances. Abbreviations: S: Source Organ; CFR: Code of Federal Regulations; GI: Gastrointestinal Tract; ALI: Annual Limit of Intake, DAC: Derived Air Concentration; ICRP: International Commission on Radiology Protection Mini Review parameters such as: the activity of the radionuclide, its physical This different internal dosimetry methods were developed for and biological half-life T and T , the fractional abundance of the the purpose of radioprotection, and radiation safety to minimize p b radiation with energy E emitted per nuclear transition n , the the risk of the effects of ionizing radiation on the people. The i i fraction of energy emitted that is absorbed in the target volume current method for calculating dose was proposed by the ICRP , the pathology or biodistribution of the radioactivity in the body [1-4]. Internal dosimetry modalities or methods are used when a i [5,6]. The equivalent and effective doses are proportional to the radioactive material enters the body by different routes inhalation, ϕ radiation and tissue weighting factors and the absorbed dose. The ingestion, absorption, injection on different circumstances either absorbed dose rate is given by the equation: by breathing, eating, or drinking respectively, contaminated air, ~~ ~ . Φ ∆Φ Φ −1 A∑∑ii NEiii A ii A ∑ i NEiii occupational or accidentally. In this course class paper, we describe D(..) rad hr orGy s= k = k = 2.13 fluids foods and wounds. These occur in different occasions, either mm m the various mathematical models for calculating the absorbed dose Ci or Bq], is the accumulated activity, (1) by diverse organs of the body. Where A ̃ [μ −1 −−11 ∆=total [rad . g .µ Ci orGy . kg . Bq . s ] 2.13Σi N i E i Internal Dosimetry Dose Calculation is the equilibrium absorbed dose constant, and , is the mass(2) of the target volume. This formula is applicable only for non- amount of energy deposited per unit mass of the body tissue. That The quantification of the absorbed dose to tissue requires the penetrating radiations ( -rays and energy comes from different type of radiations, the penetrating energy is absorbed in the target volume. For penetrating radiations and α β-rays), implying that all the (x and . Furthermore, the radiation absorbed dose is a function of lot of emissions (x and γ-rays), as well as non-penetrating ones α γ-rays), all the energy or portion of it will be absorbed by β Copyright@ Muhammad Maqbool | Biomed J Sci & Tech Res | BJSTR. MS.ID.005413. 25881 Volume 33- Issue 3 DOI: 10.26717/BJSTR.2021.33.005413 the target volume. When the source and the target are different, we 1 fraction, with , being basically the absorbed fraction and is an r 2 energy by the target tissue, then, the absorbed dose is given by the μ must insert a coefficient to account for the partial absorption of the following equation. Internationalabsorption coefficient. Commission on Radiology Protection Φ← (ICRP) −1 A* NEii i () T S D( rad . hr )= 2.13 m The ICRP introduced two methodologies ICRP II [10] and Where Φ=iT()← S AF() T ← S is the absorbed fraction (3) of dose ICRP 30 [1] for internal dosimetry implementable in occupational settings, particularly in the nuclear fuel cycle with reference to organ T. For and particles, x- and -radiation of energies less coming from the source organ (S), that is absorbed by the target than 11 keV, all the energy emitted. By the radiopharmaceutical is α β γ (Figure 1). The ICRP II is the foundation of the radiation protection absorbed in the volume greater than 1cm. So, will take the value i regulations in the US (Code of Federal Regulations (CFR), 10 CFR 0, unless the source S and target T are the same, . For and new ICRP 30. The ICRP II and ICRP 30 systems have to do with ϕ i 20), which was revised (10 CFR 20) in 1994 and gave birth to the particles, most non-penetrating radiation is usually absorbed, so occupational exposure and its calculation of the dose equivalent ϕ α β we set the absorption fraction . For x and -rays, penetrating 51.2*A *ξ i using the formula: H = , with ξ =∑ iinQ Φ i i m radiation with energy greater than , the value of i varies inversely ϕ γ Where n , is the quality with increasing energy and between 0 and 1, contingent on the i i (2)i ϕ factor of the radiation to get the result in equivalent dose. The energy. The data of i are computed by statistical Monte Carlo ϕ are defined in section 2., while Q methods based on the interaction radiation and matter [6]. constant 5.12 is the k constant that converts into rem per day, for ϕ activity A( Different Dosimetry Systems certain amount of radiopharmaceutical enters the body either by μCi), mass m(g), and energy E(MeV). At time t = 0, a inhalation or The previous formulas have been derived using lot of dose for radiopharmaceutical with complex emission spectra. respiratory system models are used to compute the transfer of simplifications and are the most commonly used to calculate ingestion. For the gastrointestinal (GI) tract as well as the These dosimetry systems that seem to look different, where some radionuclide from the GI or the respiratory system to the body parameters have been combined, may look different, but yield the same output given the same input and assumptions. fluids as well as its excretion. Then, by either pathway of intake, the enters the body through compartment a which is connected to Marinelli-Quimby Methods radionuclide enters the body fluid system [11]. The radionuclide different compartments, b, c, d, etc. representing type of tissues The equation for the dose of non-penetrating beta ( or organs of the body, where the radiopharmaceutical experiences that decays completely in a body tissue is given by the equation: β) emitter [7,8]. biological clearance and physical decay, and finally goes out of the Dββ= 73.8* CE * * T to be uniform in the reference man. The ICRP metabolic design body. The dose distribution in the first compartment is assumed uses mathematical models for the reference man to track the where: Dβ [] rad is the concentration of(4) the radionuclide, radiopharmaceutical as it moves from the original compartment C[µ Ci .] g −1 is the concentration of the nuclide, E[] MeV is the β to other tissues or organs. The different compartment models mean energy emitted per decay of the nuclide, is the half-life of are: ICRP-30 Dosimetric Model for Respiratory System (ICRP the nuclide in the tissue. By analogy with the cumulative activity, ~ 73.8 A=1.44* fAT * * ,we see that k = = 51.1 , and C[µ Ci .] g −1 is the the Gastrointestinal Tract, and ICRP-30 Dosimetric Model for 0 1.44 Human Respiratory Tract Model), ICRP-30 Dosimetric Model for activity per unit mass, and for the emitter, the absorbed fraction Submersion in a Radioactive Gas Cloud. The solutions of these =1. For penetrating radiations such as -rays, we use the geometric computations are the equivalent dose and effective dose rates of β factors of Brownell and Hine [9] for spheres and cylinders of set various tissues and organs as a function of time. Then, the committed ϕ γ shape to calculate the data for the fraction of energy emitted that equivalent dose and the committed effective dose subsequent from is absorbed in the target volume. The dose in the vicinity of the the original intake can be evaluated, as well as the ALI (Annual ϕ γ-emitter is given by the formula: e−µr rad LimitWe of calculateIntake), the the DAC committed (Derived effective Air Concentration) dose for a [11].radionuclide D=10−3τ * c dV y ∫ r2 hr in the body with the ICRP mathematical tools and data from the − reference man. The committed effective dose is given for a period where C[µ Ci .] g 1 is the activity of the gamma emitter. Similarly, (5) = 50 years by the formula: E(ττ )=∑⇔=∑ wH ( ) E (50) wH -rate constant is the exposure rate per TTT TTT disintegration from the point source (same as k**Σ nE τ by analogy, the specific γ Γ ii i e−µr where w is the weighting factor for the tissue, and H () (6) T T ∫ r 2 plays a role of the absorbed) to an (τ) is the infinite medium, while the factor committed equivalent dose of tissue T given by equation (7) Copyright@ Muhammad Maqbool | Biomed J Sci & Tech Res | BJSTR.