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A new, single-photon emission computed tomography ( SPECT ) compares favorably with conventional technology in detecting cardiac perfusion abnormalities but works in a fraction of the time, according to researchers in a multicenter study.

In addition to the shorter acquisition time for images, the high-speed SPECT may also reduce radiation exposure, the study says.

"Quantitative measures of myocardial perfusion and function, obtained using normal limits specific for the new technology, correlated extremely well with...conventional SPECT measures acquired over as much as 8 times longer time," senior author Dr. Daniel Berman, of Cedars-Sinai Medical Center in Los Angeles, and colleagues write in the May 4th issue of the Journal of the American College of Cardiology.

Researchers at Cedars-Sinai and three other American hospitals first compared conventional SPECT with the new, compact gamma camera system (Spectrum Dynamics, Ceasaria, Israel) in 63 patients with a low pre-test likelihood of coronary artery disease. Using data from this cohort, they developed method- and sex-specific normal limits.

Then they compared the results of the two technologies in a validation cohort of 238 patients.

The researchers report that high-speed stress and rest total perfusion deficit correlated linearly with conventional SPECT total perfusion deficit (r = 0.95 and 0.97, respectively, p <0.0001), with good concordance in the three vascular territories (kappa statistics for the left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery were 0.73, 0.73, and 0.70, respectively; >90% agreement).

"The percentage of ischemic myocardium by both imaging modalities was significantly larger in patients with a high coronary artery disease likelihood than in those with a low and intermediate likelihood (p < 0.001)," Dr. Berman and colleagues write.

Fast SPECT obtained results in 2 to 4 minutes, one-seventh the acquisition time.

The system's speed has another benefit, as it "lends itself to protocols that would reduce both acquisition time and radiation dose," the authors note.

"The comparative results confirm the feasibility of performing very fast SPECT imaging without jeopardizing the quality of images," Dr. Frans J. Th. Wackers, of Yale University School of Medicine in New Haven, Connecticut, writes in an editorial.

Dr. Wackers, who was not involved with the study, said it showed that imaging time can be reduced from the conventional 15 to 20 minutes. "Such short imaging times will be much better tolerated by patients," Dr. Wackers writes. "This alone has the potential of improving image quality by reducing the chance of patient motion artifacts."

In e-mail to Reuters Health, Dr. Wackers said other research on high-speed SPECT consistently has shown the feasibility of reducing imaging time with either new equipment or new software. "It is fascinating that it is possible to shorten acquisition time and still obtain better looking images," he said.

He added, however, that further research is needed. "Although there is a general agreement in imaging results between the old, slow SPECT and high-speed SPECT, there are definite differences in the images," he said. "It is not clear which technology represents the real truth. For that reason, one has to be careful in completely abandoning the old technique.

Although high-speed SPECT imaging "is well beyond the experimental stage, the definitive clinical study has as yet not been performed," Dr. Wackers said. What's needed next, he said, is a sufficiently large randomized controlled trial in which patients are assigned to either the old or new technique, and then are followed for the occurrence of cardiac events.

Source: Reuters Health

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