Comparison of Methods and Systems in Internal Radiation Dosimetry Comparison of Methods Systems in Internal Radiation

(2) is the equilibrium absorbed dose constant, and , is the mass of the target volume. This formula is applicable only for non-penetrating radiations ( α -rays and β-rays), implying that all the energy is absorbed in the target volume. For penetrating radiations (x and γ-rays), all the energy or portion of it will be absorbed INFO ABSTRACT Exact dose delivery to cancer patients in their treatment by radiation is very important. Radiation Dosimetry is a specific area in which exact dose calculation to patients and radiations workers is performed before any dose delivery. A cancer patient can be exposed to radiation in two ways: external exposure and internal exposure. External exposure occurs when source of radiation is located and placed outside a patient. Internal exposure is due to radiopharmaceuticals taken inside a patient’s body. 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 sources within the body is called internal dosimetry. In this minireview, various methods and systems used in the internal dosimetry are analyzed. Comparison of those methods reveals that every method and system has its own advantages and priorities over others in various cases and Federal


Internal Dosimetry Dose Calculation
The quantification of the absorbed dose to tissue requires the amount of energy deposited per unit mass of the body tissue. That energy comes from different type of radiations, the penetrating emissions (x and γ-rays), as well as non-penetrating ones α and β. Furthermore, the radiation absorbed dose is a function of lot of parameters such as: the activity of the radionuclide, its physical and biological half-life T p and T b , the fractional abundance of the radiation with energy E i emitted per nuclear transition n i , the fraction of energy emitted that is absorbed in the target volume ϕ i , the pathology or biodistribution of the radioactivity in the body [5,6]. The equivalent and effective doses are proportional to the radiation and tissue weighting factors and the absorbed dose. The absorbed dose rate is given by the equation:1.
Where A ̃ [μCi or Bq], is the accumulated activity, is the absorbed fraction of dose coming from the source organ (S), that is absorbed by the target organ T. For α and β particles, x-and γ-radiation of energies less than 11 keV, all the energy emitted. By the radiopharmaceutical is absorbed in the volume greater than 1cm. So, ϕ i will take the value 0, unless the source S and target T are the same, ϕ i . For α and β particles, most non-penetrating radiation is usually absorbed, so we set the absorption fraction ϕ i . For x and γ-rays, penetrating radiation with energy greater than , the value of ϕ i varies inversely with increasing energy and between 0 and 1, contingent on the energy. The data of ϕ i are computed by statistical Monte Carlo methods based on the interaction radiation and matter [6].

Different Dosimetry Systems
The previous formulas have been derived using lot of simplifications and are the most commonly used to calculate dose for radiopharmaceutical with complex emission spectra.
These dosimetry systems that seem to look different, where some parameters have been combined, may look different, but yield the same output given the same input and assumptions.

Marinelli-Quimby Methods
The equation for the dose of non-penetrating beta (β) emitter that decays completely in a body tissue is given by the equation: [7,8]. . ] C Ci g µ − is the activity per unit mass, and for the β emitter, the absorbed fraction ϕ=1. For penetrating radiations such as γ-rays, we use the geometric factors of Brownell and Hine [9] for spheres and cylinders of set shape to calculate the data for the fraction of energy ϕ emitted that is absorbed in the target volume. The dose in the vicinity of the γ-emitter is given by the formula:

International Commission on Radiology Protection (ICRP)
The ICRP introduced two methodologies ICRP II [10] and ICRP 30 [1] for internal dosimetry implementable in occupational settings, particularly in the nuclear fuel cycle with reference to We calculate the committed effective dose for a radionuclide in the body with the ICRP mathematical tools and data from the reference man. The committed effective dose is given for a period τ= 50 years by the formula: ( ) where w T is the weighting factor for the tissue, and H T (τ) is the committed equivalent dose of tissue T given by equation (7) DOI: 10.26717/BJSTR.2021.33.005413 where τ= 50 years for occupational use, and τ= 70 years for the members of the public [12]. For a target organ T, we can calculate and sum the respective committed equivalent dose from all organs, known as source organ S.

Medical Internal Radiation Dosimetry (MIRD) System
The MIRD system has been extensively studied in class, so, here we are going write down the main equations that govern that system [13]. The absorbed dose in the MIRD system is given by the set of equations below: Equation (11)

Radiation Dose Assessment Resource (RADAR)
The Radiation Dose Assessment Resource set up a website www.doseinfo-radar.com. The introduction of the internet gave the scientific community the impulse to disseminate a number of publications on data and procedures used in the system. The RADAR system is ruled by the equation [14].
where and are respectively the number of transformations going on in the organ (the number of disintegrations is the area of the activity-time curve for a source region) and is given by the expression: Mathematically speaking is similar to the mean dose per cumulated activity defined in the MIRD system by the equation (11) in 3.3 . The RADAR team put together collections of decay data, dose conversion factors, and classified, identical dose models for occupational workers and nuclear medicine patients. Furthermore, they developed a computer code, OLINDA/EXM that works with formulas (12), (13) and input data from RADAR site [15].

Specific Absorbed Fraction, Specific Effective Energy, and Committed Quantities
The specific equivalent dose in a target organ T caused by the The product of Y R E R by ( gives the mean absorbed dose in the target T per disintegration in source S by the type of radiation R. The ICRP expresses the specific effective energy (SEE) transmitted per gram of tissue in T from the emission of a specific radiation R in the source organ S per disintegration as follows [12], Where R w is the weighting factor of radiation R emitted per disintegration of a radionuclide in source S to the equivalent dose in target T. To get this expression in radiation protection unit, we time the SEE by the factor:

Conclusion
It has been long journey exploring, learning about the various internal dosimetry systems that are used to monitor, evaluate exposure for occupational workers as well as the public. All these dosimetry systems are crucial for protecting radiation workers and the public in order to prevent acute, rare effect of radiation, as well as minimizing the risk for long-term effects. Finally, we protect the people, also, by verifying adequacy at workplace controls and demonstrating regulatory compliance.