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With guidance from staff interventional radiologist Abraham Levitin, MD, Mr. Young and colleagues found that 99mTc-MAA SPECT/CT was 2.5 times more accurate than planar imaging in this role.

Scintigraphy using single photon emission computed tomography with an integrated x-ray computed tomography scanner (SPECT/CT) to detect extrahepatic shunting could help boost the safety of yttrium-90 (90Y) radiomicrosphere therapy in the liver, according to a Cleveland Clinic study presented here at the Society of Nuclear Medicine (SNM) 2010 Annual Meeting.

Microsphere technology has gained popularity among surgeons and interventional radiologists as an effective organ-preserving method of individually treating hepatic malignancies, noted lead investigator and presenter Ron Young, technologist and manager of the nuclear medicine department at the Cleveland Clinic in Ohio.

Mr. Young described how, in a typical procedure, the 20 to 40 μm glass spheres imbedded with 90Y are injected into hepatic artery circulation where they selectively embolize the tumor's microvasculature. Beta particles emitted by the isotope kill cells in a 2.4 mm diameter region around the tumor and spare healthy liver tissue.

Hepatic radiomicrosphere therapy is considered safe, with a complication rate of less than 5%, Mr. Young reported. But he added that many adverse events arise from the incomplete embolization of the hepatic vessels under angiographic guidance before the procedure. It can lead to severe pulmonary, gastrointestinal, and pancreatic radiation burns after the 90Y particles are shunted from the liver. Other complications include pancreatitis, cholestitis, and gastritis, he told Medscape Radiology in an interview.

To minimize risk, technetium-99m (99mTc) microaggregated albumin (MAA) imaging is performed to simulate extrahepatic shunting in the presence of incomplete hepatic vessel embolization before the surgeon moves on to the actual procedure, Mr. Young explained. With guidance from staff interventional radiologist Abraham Levitin, MD, Mr. Young and colleagues found that 99mTc-MAA SPECT/CT was 2.5 times more accurate than planar imaging in this role.

In 99 consecutive patients who underwent both imaging procedures, extrahepatic shunting was detected in 23 patients with SPECT/CT and in 9 patients with the planar approach. The investigators did not perform a detailed statistical analysis. SPECT/CT also detected a hepatic thrombosis that was not observed on planar images, Mr. Young noted. The finding led the surgical team to minimize the lumen of the thrombosis in the inferior vena cava before turning their attention back to liver treatment, he added.

The findings promise a significant improvement over the standard technology, said Peter S. Conti, MD, professor of radiology, pharmacy, and biomedical engineering at the University of Southern California in Los Angeles. Dr. Conti was not involved with the study.

"The broader implications are that the use of SPECT/CT improves the ability of the clinician to determine if patients are good candidates for therapy," he said during an SNM-sponsored media briefing.

Hooman Kabiri, MD, who performs 90Y microsphere procedures at the Ohio State University Medical Center in Columbus, said in a phone interview that a shift to SPECT/CT would give him and other interventionist radiologists more peace of mind.

"It can add to the sensitivity of detecting our ability to embolize the communications between the hepatic and nonhepatic arteries. It is a valuable tool in that respect," he told Medscape Radiology.

But shifting to SPECT/CT could also lead to unnecessary treatment delays because of possible false positives, he cautioned. The 3% adverse incident rate at Ohio State suggests that the actual rate of extrahepatic shunting is much lower than the 23% rate identified with SPECT/CT in the Cleveland Clinic study, he said about the trial.

A larger prospective study testing the relative clinical efficacy and accuracy of the 2 imaging techniques is planned, Mr. Young told SNM meeting attendees. The study did not receive commercial support. Mr. Young, Dr. Conti, and Dr. Kabiri have disclosed no relevant financial relationships.

Source: Society of Nuclear Medicine (SNM)