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On the potential use of stimulated positron emission (SPE) in the detection and monitoring of some bone diseases
Author(s) -
Benjamin Menashe,
Macovski Albert
Publication year - 1980
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.594832
Subject(s) - osteomalacia , bone mineral , osteoporosis , nuclear medicine , bone tissue , materials science , cortical bone , biomedical engineering , chemistry , medicine , pathology
The feasibility of a new method for in vivo regional measurement of the loss of bone tissue in osteoporosis and bone mineral in osteomalacia has been studied analytically. A cross section in the patient's body containing the bone is excited by high energy x rays ( h ν>1.022 MeV) to produce positron–electron pairs. The positron distribution is imaged by detecting the resulting annihilations using two detectors placed on opposite sides of the irradiated slice and focused to receive annihilations produced inside the bone. Since the cross section for pair production is proportional to the square of the atomic number of the absorber, any pathological processes involving demineralization or loss of bone tissue are expected to strongly affect the number of counts received from the region imaged. This technique is unique among other radiological procedures for bone measurements in its direct three‐dimensional imaging capability. It has no fundamental limit on precision, and higher precision is achieved by resorting to higher dose or greater bony volume irradiated. In addition, the measurement can be confined to an anatomically and physiologically appropriate bone site, thus maximizing the signal and minimizing interference from surrounding tissues. Using radiological models for osteoporosis and osteomalacia, it is shown that a high sensitivity to small changes (∼5%) in density or amount of mineral of cortical bone can be obtained with a relatively low radiation dose (<0.5 rad). With the same radiation dose, the method is less sensitive to changes in vertebral bone, due to the lower mineral fraction in this type of bone. The dependence of sensitivity on incident x‐ray energy is studied, and it is shown that the optimum energy, from a point of view of maximizing sensitivity while minimizing the loss of spatial resolution due to positron range lies at between 2 and 3 MeV. Finally, the application of the technique in the detection and monitoring of bone cancer and tumors metastatic to bone is suggested.