High-res detectors improve SPECT/CT evaluation of skeletal disease

SPECT/CT using high-resolution CT detector technology has been found to increase the diagnostic capabilities of SPECT when used to detect diseased bone, including osteomyelitis and other peripheral skeletal disease, and at a lower cost than high-resolution multi-detector CT, according to a study published May 23 in the Journal of Nuclear Medicine.

Christian Lohrmann, MD, from the department of nuclear medicine at the University Hospital Freiburg in Freiburg, Germany, and colleagues conducted a study of simultaneous SPECT/CT for the detection of bone disease using high-resolution cone-beam and flat-panel detector CT technology, which was shown to be diagnostically superior to SPECT and low-resolution CT.

For this retrospective study, 41 patients with suspected peripheral skeletal disease, including 14 patients being evaluated for arthroplasty or arthrodesis, 14 patients for degenerative joint disorders and 13 patients for osteomyelitis, were imaged with Tc-99m dicarboxypropane diphosphonate SPECT/CT using dual-head gamma camera and low-energy high-resolution collimator technology. Image reconstruction was based on image data with a voxel size of 0.33 x 0.33 x 0.33 mm. To reflect low-resolution CT for comparison study, image reconstruction was conducted with a software filter for image data with the spatial resolution of 1.32 x 1.32 x 10 mm. Resulting images were read independently by two readers.

“The diagnostic accuracy was improved by high-resolution CT because of better identification of nonhealing fractures, better visualization of bone formation in arthrodesis, and more accurate identification of degenerative joint disease,” wrote the authors. “Consequently, a clear differentiation between osteomyelitis, degenerative joint disease, nonhealing fracture or arthrodesis, osteochondritis dissecans, arthritis, and loosening of arthroplasty could be made by the two readers."

Results were scored 1 to 3 based on definitive diagnostic value. A score of 1 indicated definitive patient diagnosis, whereas a 2 indicated a probable diagnosis and 3 indicated no apparent abnormalities in imaging. Findings showed high-resolution CT technology lead to a higher mean of diagnostic confidence, 1.98 for both readers, when compared to low-resolution CT, 1.10 for reader one and 1.3 for reader two (P < 0.01).

A total of 37 out of 41 patients were diagnosed correctly by reader one and  30 out of 41 patients by reader two using high-resolution CT. The results were significantly different when they interpreted the low-resolution CT image data.

“For the SPECT/low-resolution CT images, the diagnostic confidence scores were markedly lower,” the researchers wrote. “A definitive diagnosis was feasible in less than 20 percent of the patients, and most of the scans were rated with a score of 2.”

SPECT and high-resolution CT revealed to have a diagnostic accuracy of 90 percent and SPECT with low-resolution CT was 60 percent accurate for the detection of bone disease.

“High-resolution cone-beam CT with flat-panel detectors is thus a promising technology to improve the diagnostic accuracy of SPECT studies of the peripheral skeleton and may facilitate the diagnostic workup of patients with abnormalities on bone SPECT,” summed the authors.