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Phys Med Biol

Title:		Single-photon transmission measurements in positron tomography using 137Cs
Author(s):		Yu SK; Nahmias C;
Address:		"Department of Nuclear Medicine, McMaster University Medical Centre, Hamilton, Ontario, Canada"
Journal Title:		Phys Med Biol
Year:		1995
Volume:		40
Issue:		7
Page Number:		1255 - 1266
DOI:		10.1088/0031-9155/40/7/008
ISSN/ISBN:		0031-9155 (Print) 0031-9155 (Linking)
Abstract:		"Transmission measurements are an essential step in the quantification of radioisotope distributions in vivo using positron tomographic techniques. The development of a new technique for measuring transmission data that relies on the detection of photons in 'singles' mode rather than 'coincidence' mode no longer restricts the choice of transmission sources to those that decay by positron emission. The motivation for using the 'singles' mode of operation is the substantial increase in count rate that can be achieved. This corresponds to a great increase in the statistical accuracy of the transmission data. We propose 137Cs as a suitable isotope for this purpose. 137Cs is more economical than 68Ge, the traditional source used for transmission measurements, in terms of longer half-life and lower financial cost. 137Cs can be used for transmission measurements without any recalibration of the tomograph, and the estimated spatial resolution is comparable to that obtained using annihilation photons. A simple extrapolation method is developed, which allows extrapolation of the attenuation coefficients measured at 662 keV to 511 keV. A dual-energy-window technique, whereby correction can be made on-the-fly during acquisition, is used for scatter correction. The measured linear attenuation coefficients agree with predicted values"
Keywords:		"*Cesium Radioisotopes Germanium Humans Mathematics *Models, Structural Organ Specificity *Phantoms, Imaging Photons Probability Radioisotopes Scattering, Radiation Tomography, Emission-Computed/*methods Tomography, Emission-Computed, Single-Photon/*method;"
Notes:		"MedlineYu, S K Nahmias, C eng Comparative Study Research Support, Non-U.S. Gov't England 1995/07/01 Phys Med Biol. 1995 Jul; 40(7):1255-66. doi: 10.1088/0031-9155/40/7/008"