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Quantitative Organ Visualization Using SPECT

Department of Radiology, University of California, San Francisco, California
Division of Nuclear Medicine, University of Michigan Medical Center, Ann Arbor, Michigan
Department of Radiology, Georgetown University, Washington, DC

Correspondence: For reprints contact: Louis T. Kircos, DDS, MS, PhD, Div. of Oral Radiology, University of California, San Francisco, San Francisco, CA 94143.

ABSTRACT

Quantitative organ visualization (QOV) was performed using single photon emission computed tomography (SPECT). Organ size was calculated from serial, contiguous ECT images taken through the organ of interest with image boundaries determined using a maximum directional gradient edge finding technique. Organ activity was calculated using ECT counts bounded by the directional gradient, imaging system efficiency, and imaging time. The technique used to perform QOV was evaluated using phantom studies, in vivo canine liver, spleen, bladder, and kidney studies, and in vivo human bladder studies. It was demonstrated that absolute organ activity and organ size could be determined with this system and total imaging time restricted to <45 min to an accuracy of about ±10% providing (a) the minimum dimensions of the organ are > the FWHM of the imaging system and (b) the total radioactivity within the organ of interest exceeds 15 nCi/cc for dog-sized torsos. In addition, effective half-lives of 1.5 hr or greater could be determined.