Positron tomographic imaging of the liver: ⁶⁸Ga iron hydroxide colloid

A new radiopharmaceutical, ⁶⁸Ga iron hydroxide colloid, for hepatic imaging by positron emission tomography was prepared from the eluate of a ⁶⁸Ge-⁶⁸Ga solvent extraction generator. In rats, 84% of the administered dose of colloid localized in the liver and 4.6% accumulated in the spleen. Initial imaging studies in normal dogs showed close correspondence of the findings by positron tomography and transmission computed tomography. Emission tomography with ⁶⁸Ga-colloid was performed in 10 patients with hepatic metastases demonstrated by conventional (99m)Tc sulfur colloid scintigraphy. All focal defects noted on the conventional scintigrams were easily identified and generally were seen more clearly by positron tomography. In one patient, additional lesions not identified on the initial (99m)Tc sulfur colloid images were demonstrated. The positron tomographic images were compared with those obtained by transmission computed tomography in seven patients; the two studies showed comparable findings in five patients, whereas positron tomography more clearly showed multiple lesions in two. Our results suggest that positron emission tomography is a suitable technique for obtaining high contrast, cross-sectional images of large abdominal organs.