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The effects of body and organ size on absorbed dose: There is no standard patient
Abstracts and ellipsoids of masses down to 1 g. Consideration is given to the adjustment of the activities administered to the various age groups relative to that normally administered to adults. Radiation doses to whole body and to certain critical organs are given for the various radiopharmaceuticals.
The Effects of Body and Organ Size on Absorbed Dose: There is no Standard Patient, by J. W. POSTON. Health Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830. U.S.A. problem of estimating the absorbed dose to organs and tissues of the body due to the presence of a radiopharmaceutical in one or more organs is discussed. Complications are introduced by the fact that the body is not homogeneous and in many cases the organ shapes are not regular. Publications of the MIRD Committee have provided a direct means of estimating the absorbed dose (or absorbed fraction) for a number of radioisotopes. These estimates are based on Monte Carlo calculations for monoenergetic photons distributed uniformly in organs of an adult phantom. In addition, the absorbed fractions for the adult are not reasonable values for the child. The paper examines how these absorbed fraction estimates apply to a nonstandard patient. The historical developments in dose estimation related to body and organ size are traced. These developments include the early use of simple shapes, the design of a realistic adult phantom, and simple methods and scaling laws used to apply absorbed fraction estimates obtained for these smaller phantoms are presented and compared to estimates obtained by other procedures. TfxE
The Development of a Mathematical Phantom Representing a lo-yr Old for Use in Internal Dosimetry Calculations, by S. F. DELJS and J. W. POSTON. Health Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, U.S.A. WITH the increased growth of nuclear energy generating facilities, estimates of absorbed dose to other population groups (e.g. children) are required. In addition, children are being exposed to many nuclear medicine procedures and accurate dose estimates are needed. The main purpose of this research is to design a mathematical phantom
151
representing as closely as possible a IO-yr old child. The phantom was similar in shape to the adult phantom of Snyder and Fisher, but several changes were made in the design to make the phantom more realistic. These changes included the addition of a neck and feet, placing the arms outside the trunk section, changing the shape of the trunk region, and a redesign of the male genitalia rc~icjr~. Several modifications were made to the itleali7ctl skeleton. For example, the skull, ribs. pelvis. spine. scapulae and clavicles were redesigned to approllmate more closely the true anatomical shapes. Some internal organs were modified as a result of the above changes. These organs included Ihc brain, lungs, liver and the large and small Intz\ tines. However, in all cases, an attempt was made to modify the shapes and locations in a manner such that they were more representative of those of the 10-yr old child. A description of the phantom and its utility will be presented. Estimates of absorbed dose obtained with this phantom are expected to be significantly different from those estimates derived through the use of simpler models. These differences and their significance will be discussed also.
CAMIRD/II-Computer Software to Facilitate Absorbed-Dose Calculations, by PAUL A. FELLER Bureau of Radiological Health, FDA. HEW, Cincinnati General Hospital, Cincinnati, Ohio 45267, U.S.A. CAMIRDIII, a computer software system designed or mini-computers, for the users of time-sharing eliminates the tedium associated with the MIRD method of computing absorbed doses. The system consists of four programs written in FORTRAN IV, plus nuclide and specific-absorbed-fraction data files. The dose calculation program of the system only requires that the user specify the radionuclide, the target and source organs, and cumulated activities. Using previously stored data files of nuclide decay parameters and specific absorbed fractions, the program calculates absorbed dose contributions to the target organ from activity in each specified source organ and from the remainder of the body. Benefits of this program are ease of operation and greater speed, precision and accuracy than through manual computations. Another program in the system calculates and prints values of S, the mean absorbed dose per unit cumulated activity of a specified radionuclide, for available combinations
The Effects of Body and Organ Size on Absorbed Dose: There is no Standard Patient, by J. W. POSTON. Health Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830. U.S.A. problem of estimating the absorbed dose to organs and tissues of the body due to the presence of a radiopharmaceutical in one or more organs is discussed. Complications are introduced by the fact that the body is not homogeneous and in many cases the organ shapes are not regular. Publications of the MIRD Committee have provided a direct means of estimating the absorbed dose (or absorbed fraction) for a number of radioisotopes. These estimates are based on Monte Carlo calculations for monoenergetic photons distributed uniformly in organs of an adult phantom. In addition, the absorbed fractions for the adult are not reasonable values for the child. The paper examines how these absorbed fraction estimates apply to a nonstandard patient. The historical developments in dose estimation related to body and organ size are traced. These developments include the early use of simple shapes, the design of a realistic adult phantom, and simple methods and scaling laws used to apply absorbed fraction estimates obtained for these smaller phantoms are presented and compared to estimates obtained by other procedures. TfxE
The Development of a Mathematical Phantom Representing a lo-yr Old for Use in Internal Dosimetry Calculations, by S. F. DELJS and J. W. POSTON. Health Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, U.S.A. WITH the increased growth of nuclear energy generating facilities, estimates of absorbed dose to other population groups (e.g. children) are required. In addition, children are being exposed to many nuclear medicine procedures and accurate dose estimates are needed. The main purpose of this research is to design a mathematical phantom
151
representing as closely as possible a IO-yr old child. The phantom was similar in shape to the adult phantom of Snyder and Fisher, but several changes were made in the design to make the phantom more realistic. These changes included the addition of a neck and feet, placing the arms outside the trunk section, changing the shape of the trunk region, and a redesign of the male genitalia rc~icjr~. Several modifications were made to the itleali7ctl skeleton. For example, the skull, ribs. pelvis. spine. scapulae and clavicles were redesigned to approllmate more closely the true anatomical shapes. Some internal organs were modified as a result of the above changes. These organs included Ihc brain, lungs, liver and the large and small Intz\ tines. However, in all cases, an attempt was made to modify the shapes and locations in a manner such that they were more representative of those of the 10-yr old child. A description of the phantom and its utility will be presented. Estimates of absorbed dose obtained with this phantom are expected to be significantly different from those estimates derived through the use of simpler models. These differences and their significance will be discussed also.
CAMIRD/II-Computer Software to Facilitate Absorbed-Dose Calculations, by PAUL A. FELLER Bureau of Radiological Health, FDA. HEW, Cincinnati General Hospital, Cincinnati, Ohio 45267, U.S.A. CAMIRDIII, a computer software system designed or mini-computers, for the users of time-sharing eliminates the tedium associated with the MIRD method of computing absorbed doses. The system consists of four programs written in FORTRAN IV, plus nuclide and specific-absorbed-fraction data files. The dose calculation program of the system only requires that the user specify the radionuclide, the target and source organs, and cumulated activities. Using previously stored data files of nuclide decay parameters and specific absorbed fractions, the program calculates absorbed dose contributions to the target organ from activity in each specified source organ and from the remainder of the body. Benefits of this program are ease of operation and greater speed, precision and accuracy than through manual computations. Another program in the system calculates and prints values of S, the mean absorbed dose per unit cumulated activity of a specified radionuclide, for available combinations