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Nov 1978

Volume 5, Issue 6, pp. 467-573

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Thallium‐201 production with the idle beam from neutron therapy

James W. Blue, David C. Liu, and James B. Smathers

Med. Phys. 5, 532 (1978); http://dx.doi.org/10.1118/1.594444 (4 pages) | Cited 1 time

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Deuteron reactions have been studied for the possibility of producing 201Tl so that this radioisotope could be made as an adjunct to neutron therapy. The cross‐sections for the (d,xn) reactions for 203Tl and 205Tl target nuclei have been measured for x=3, 4, and 5. From these data the yields of 201Tl for a typical treatment day have been calculated.
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87.53.Jw Therapeutic applications, including brachytherapy
87.57.-s Medical imaging
87.63.-d Non-ionizing radiation equipment and techniques
87.85.Pq Biomedical imaging
87.80.-y Biophysical techniques (research methods)

Use of a pencil‐shaped ionization chamber for measurement of exposure resulting from a computed tomography scan

Arata Suzuki and Marcia N. Suzuki

Med. Phys. 5, 536 (1978); http://dx.doi.org/10.1118/1.594445 (4 pages) | Cited 14 times

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A simple method of comparing and/or monitoring the radiation output level of a Computed Tomography (CT) system, using a specially developed pencil‐shaped ionization chamber, is presented. When the measurement is made with a phantom for the period of one tomographic scan, the result can be interpreted as the average exposure along the chamber axis resulting from the entire series of scans to be performed by the CT system. An interesting feature of this method is that no detailed knowledge of the beam distribution or slice thickness is necessary in order to measure the radiation output level, to compare the performance of CT systems or to estimate patient’s exposure for a particular combination of CT operation parameters.
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87.53.Bn Dosimetry/exposure assessment
87.57.-s Medical imaging
87.63.-d Non-ionizing radiation equipment and techniques
87.85.Pq Biomedical imaging

New approach to the LSF measurement of x‐ray intensifying screens

J. M. Geary

Med. Phys. 5, 540 (1978); http://dx.doi.org/10.1118/1.594446 (3 pages) | Cited 1 time

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The traditional method for obtaining the line spread function (LSF) of double screens used in medical x‐ray diagnostic systems has made extensive use of radiographic film. An alternate radiometric approach is discussed in this note, which makes use of a scanning optical slab waveguide as a means of coupling screen‐fluorescent light to the outside world for detection.
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87.57.-s Medical imaging
87.63.-d Non-ionizing radiation equipment and techniques
87.85.Pq Biomedical imaging
87.80.-y Biophysical techniques (research methods)

Determination of effective energies in CT calibration

Michael R. Millner, William H. Payne, Robert G. Waggener, William D. McDavid, Michael J. Dennis, and Victor J. Sank

Med. Phys. 5, 543 (1978); http://dx.doi.org/10.1118/1.594488 (3 pages) | Cited 8 times

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The effective energy of a polychromatic beam for a Computed Tomography (CT) scanner can be measured directly only with difficulty. However, a linear relationship exists between the measured CT numbers and corresponding attenuation coefficients of known materials at the effective energy of the x-ray beam. The effective energy can then be determined by searching all energies for the best linear correlation between the CT numbers and the attenuation coefficients. This can be performed by two methods: graphically, by means of choosing visually the straightest of the fitted lines or, mathematically, by maximizing the correlation coefficient. The energy corresponding to the optimal fit is therefore selected as the effective energy. The latter method was implemented by computer and demonstrated by scanning the AAPM phantom, which contained known materials, and determining the effective energies and the relationship between the linear attenuation coefficients and CT numbers for three commercial units.
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87.50.S- Radiofrequency/microwave fields effects
87.50.W- Optical/infrared radiation effects
87.57.-s Medical imaging
87.63.-d Non-ionizing radiation equipment and techniques
87.85.Pq Biomedical imaging
87.80.-y Biophysical techniques (research methods)

Development of optical process for accessing three‐dimensional patient topology

Irving A. Lerch, Robert J. Barish, and Howard Stern

Med. Phys. 5, 546 (1978); http://dx.doi.org/10.1118/1.594447 (4 pages) | Cited 1 time

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A commercial optical system developed by Solid Photography, Inc., has been used to generate precise paraffin–polyethylene tissue compensators. A program with the objective of constructing a medical facility has been undertaken to access patient topology for treatment planning, tissue‐compensator fabrication, and patient positioning verification on the treatment table. Currently, patients are taken to a specially equipped studio where a series of microprocessor‐controlled reticles are projected on the surface to be analyzed and photographs are taken automatically for computer processing. The topology data then drives a machine tool to sculpt the tissue compensators and may be transmitted via acoustic‐coupled terminals to a treatment‐planning computer at the Medical Center. The tissue compensators have been found to conform accurately to patient contours. At present, data bases can be generated to accommodate volumes of approximately 70 000 cm3.
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87.57.-s Medical imaging
87.63.-d Non-ionizing radiation equipment and techniques
87.85.Pq Biomedical imaging
87.55.-x Treatment strategy
87.90.+y Other topics in biological and medical physics (restricted to new topics in section 87)

An exposure timer for use with telecobalt units

A. Kannan

Med. Phys. 5, 550 (1978); http://dx.doi.org/10.1118/1.594448 (2 pages)

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The influence of mains frequency variation on the exposure output of teletherapy machines has been investigated. As the correction to be applied for such variations during routine treatment is cumbersome, a silicon diode timer, which works directly by the action of radiation, is described.
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87.53.Bn Dosimetry/exposure assessment
06.30.Ft Time and frequency

A review of the reliability of chamber factors used clinically in the United States (1968–1976)

W. F. Hanson, W. Grant, III, P. Kennedy, J. H. Cundiff, W. F. Gagnon, L. W. Berkley, and R. J. Shalek

Med. Phys. 5, 552 (1978); http://dx.doi.org/10.1118/1.594449 (4 pages)

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One of the principle concerns of a physicist responsible for calibrating megavoltage radiotherapy equipment is the validity and stability of the 60Co exposure correction factor assigned to his ionization‐chamber and electrometer system. It is the practice of the AAPM Radiological Physics Center (RPC) to perform an intercomparison between the RPC chamber and electrometer system and the chamber and electrometer in use at each of the various institutions visited by the RPC. The results of 202 such intercomparisons are reviewed to determine (1) the consistency in the assignment of exposure correction factors by a calibrating agency with itself and with other calibrating agencies, and (2) the dependence of the reliability of the exposure correction factors upon the type of field instrument and the time since calibration.
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87.53.Bn Dosimetry/exposure assessment
87.57.-s Medical imaging
87.63.-d Non-ionizing radiation equipment and techniques
87.85.Pq Biomedical imaging

An analysis of discrepancies encountered by the AAPM radiological physics center

William F. Gagnon, Lawrence W. Berkley, Paula Kennedy, William F. Hanson, and Robert J. Shalek

Med. Phys. 5, 556 (1978); http://dx.doi.org/10.1118/1.594450 (5 pages)

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The AAPM Radiological Physics Center has reviewed 188 institutions and has evaluated such parameters as coincidence of radiation field and light field, timer error (end effect), beam flatness and symmetry, transmission through blocking trays, wedges and compensators, and central‐axis depth‐dose data. In previous papers these data had been presented in combination as they resulted in discrepancies in tumor dose. The individual sources of discrepancies were listed only as frequency and maximum deviation. A detailed analysis is now presented which may help define criteria of recommended practice.
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87.53.Bn Dosimetry/exposure assessment
87.55.-x Treatment strategy

Report of the workshop on medical imaging

N. A. Baily

Med. Phys. 5, 561 (1978); http://dx.doi.org/10.1118/1.594451 (4 pages)

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Abstract Unavailable
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87.50.C- Static and low-frequency electric and magnetic fields effects
87.57.-s Medical imaging
87.63.-d Non-ionizing radiation equipment and techniques
87.85.Pq Biomedical imaging
42.79.Ls Scanners, image intensifiers, and image converters
42.79.Pw Imaging detectors and sensors

Survey of program directors for training of medical physicists

L. H. Lanzl, D. E. Cunningham, B. E. Bjärngard, J. E. Dowdey, R. E. Johnston, A. R. Liboff, and E. Siegel

Med. Phys. 5, 565 (1978); http://dx.doi.org/10.1118/1.594452 (3 pages)

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A survey of the 34 known training programs in medical physics elicited 28 responses for active programs. A key question of the program directors was their attitude toward program accreditation: 22 of 28 were in favor. The survey also disclosed some details of the training programs.
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01.40.-d Education
87.90.+y Other topics in biological and medical physics (restricted to new topics in section 87)
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Departments of Radiology, Radiation Oncology, Biophysics, Community and Public Health, Medical College of Wisconsin
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