Manufacturers expect single photon emission computed tomography (SPECT)/CT to outpace dedicated standalone SPECT systems in the near future. This surge comes as early adopters of the combination scanners tout their patient care benefits in major medical journals. Encouraged by this reception, manufacturers and clinicians are exploring additional SPECT/CT applications and developing new hardware and software upgrades.

"Most clinicians recognize the clinical benefits of SPECT/CT, including improved localization and attenuation correction," said Nathan Hermony, general manager for GE Healthcare's SPECT/CT business.

Many clinicians have indicated a preference for SPECT/CT in evaluating prostate cancer, endocrine tumors and sentinel node imaging, where a SPECT-only study may be considered more difficult to interpret. "The same study performed with SPECT/CT includes easily identifiable anatomical landmarks from the CT," says Hermony.

SPECT/CT's use in characterizing bone scan lesions, for example, is improving specificity, said Horace Hines, PhD, chief technology officer for the nuclear medicine division of Philips Healthcare. "The bone scan is very sensitive in detecting bone lesions, but it is not specific," said Dr. Hines. "A high-resolution CT image of the lesion provides information on the cause of the abnormality, so SPECT/CT is the ideal combination to improve diagnostic information."

The sports medicine field, in particular, combines the bone SPECT scan with CT images to guide therapy. "[SPECT/CT] is especially important in stress fractures to find the lesion on the bone scan and register it accurately with a high-resolution CT scan," said Dr. Hines. "This is an application where millimeters can make a significant difference in treatment due to the fine bones in the feet, ankle, hands and wrist."

SPECT/CT also continues to enjoy a role in cardiac imaging-specifically, for attenuation correction and calcium scoring using low-dose CT, says Hermony. Advanced CT scanners are challenging system designs, said Sergio Calvo, director of marketing for Siemens Healthcare's molecular imaging division. "We don't see high-end cardiac CT integrating into SPECT in one system," he says.

Some physicians and customers cite the suboptimal workflow from a high-end SPECT/CT scanner as a drawback to the fusion technology, claiming little benefit from a combined machine, said Dr. Hines. "The CT exam can be performed more rapidly than the SPECT [study], so the financial justification is very difficult-four to six CT exams can be done in an hour while only two SPECT studies can be performed," he said. "Furthermore, in a SPECT/CT machine, the CT technology is always behind state-of-the-art CT since there is a delay in the development and integration process."

To offer a speedier SPECT/CT cardiac option, Siemens introduced IQ•SPECT at the 2008 Society of Nuclear Medicine (SNM) annual meeting in New Orleans. The system offers quick turnaround on cardiac SPECT studies via a combination of a collimator that magnifies the heart in a cardiocentric orbit and the ability to acquire the image in five minutes, said Calvo.

Looking beyond matters of the heart, engineers are working to improve acquisition speed, resolution and image quality for all areas of the body.

"We need systems that are faster, lower dose and capable of enabling new applications," said Hermony. "We continue to explore new applications [that] can provide additional information to clinicians from SPECT/CT exams and/or improve the experience of interpreting studies."

Scott Hatfield is senior industry editor of ADVANCE.