SPECT/CT: Diagnostic Confidence Is on the Rise as Need for Additional Studies Falls

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Philips Precedence SPECT/CT features a 16-slice CT and can be used for combination studies, as well as CT-only and SPECT-only exams.

Single-photon emission computed tomography (SPECT) coupled with computed tomography (CT) is on the cusp of defining a new standard of diagnostic imaging for a variety of indications. The modality is expanding its presence in cardiac and oncological medicine and stands ready to offer clinicians a powerful tool for musculoskeletal indications.

Since its commercial introduction by GE Healthcare in 1999, SPECT/CT has been steadily winning converts as the technology increases its deployment. The response from clinicians conducting studies with the equipment, as well as their referrers, has been nothing short of enthusiastic.

Nuclear medicine physicians utilizing SPECT/CT no longer have to hear the old bromide about “unclear medicine;” the anatomic detail of CT paired with the functional capabilities of SPECT is delivering exams that are increasing diagnostic certainty, reducing the need for additional imaging procedures, and providing precise roadmaps for surgical interventions.

Cardiac clarity

Jean Luc Urbain, MD, PhD, chief and chair of nuclear medicine at the University of Western Ontario, Schulich School of Medicine and Dentistry in London, Ontario, said the facility began its SPECT/CT program with a GE Hawkeye in 2004 and immediately saw utilization of the modality proliferate.

“We now have four units installed, and a fifth one coming on-line shortly” he says.

His practice does quite a bit of nuclear cardiac studies on the units, as many oncology exams as it can, and a fair amount of musculoskeletal imaging.

“We see 3,000 patients for stress tests with myocardial perfusion imaging (MPI) a year, mostly on SPECT/CT,” Urbain says. “Cardiology represents about 40 percent of our business annually, oncology about 30 to 40 percent, and the rest is musculoskeletal.”

The department bases its determination of SPECT/CT exam usage on whether the SPECT portion of the study will be enhanced by CT capabilities, according to Urbain.

“My estimate is about 35 percent of the time SPECT images are enhanced by the CT portion of equipment,” he notes.

One of the greatest advantages to using SPECT/CT is that the specificity of the diagnoses from the department has been greatly enhanced, Urbain says.

“Now that we have the capability to view the functional and anatomic aspects of the exam together, we are very confident about the localization of what we see,” he explains. “Overall, it has improved tremendously our ability to diagnose accurately.”

This has been most evident in the practice’s MPI studies. They’ve been able to decrease uncertainty in these exams by about 20 to 25 percent by conducting the procedures on SPECT/CT, which has led to better patient management.

“It has drastically improved our ability to diagnose, or rule out, ischemia,” he notes.

SPECT/CT has provided another benefit to the facility; by its capability to increase diagnostic certainty, physicians are now better able to provide a diagnosis without conducting additional imaging studies on other modalities. This, in turn, has allowed greater utilization of these technologies for other patients.

Urbain is particularly excited about the possibilities for the future of SPECT/CT in cardiac imaging. He and his colleagues have begun an investigation into the efficacy of SPECT/CT MPI procedures being conducted with coronary CT angiography (CTA) in a single patient session.

“We have learned so much over the past six months that we can probably begin rewriting textbooks,” he says. “We are seeing things that we never would have suspected.”

Given the capability to design an ideal SPECT/CT system, Urbain would opt for a cardiac dream machine.

“From the medical/scientific aspect, I’d like to see a CZT [cadmium zinc telluride digital detector] SPECT paired with at least a 64-slice CT to do cardiac work,” he says.

Oncologic localization

Donald Neumann, MD, PhD, director of nuclear oncologic imaging in the department of nuclear medicine at the Cleveland Clinic in Cleveland, says he was impressed with SPECT/CT from the time it was brought on-board the facility in 2005.

The department uses a 6-slice Siemens Medical Solutions Symbia T6 TruePoint SPECT·CT system to conduct a variety of studies including: MPI, thyroid and parathyroid, brain (cerebrovascular disease and seizure imaging), a variety of octreotide exams, gastrointestinal, ProstaScint (a Cytogen-developed