Usefulness of hybrid SPECT/CT in Tc-99m-HMPAO-labeled leukocyte scintigraphy for bone and joint infections

White blood cell scanning with Tc-99m-hexamethylpropylene amine oxime (HMPAO) has proven highly sensitive and specific in the diagnosis and follow-up of patients with suspected osteomyelitis. The aim of this prospective study was to evaluate the usefulness of SPECT and transmission CT performed simultaneously using a hybrid imaging device for the functional anatomic mapping of bone and joint infections. Methods: Tc-99m-HMPAO scintigraphy was performed on 28 consecutive patients: 15 with suspected bone infection (group 1) and 13 with suspected orthopedic implant infection (group 2). Planar scans were acquired 30 min, 4 h, and 24 h after injection. SPECT/CT was obtained 6 h after tracer injection, using a dual-head gamma-camera coupled with a low-power x-ray tube. In all patients, scintigraphic results were matched with the results of surgery or cultures and of clinical follow-up. Results: Tc-99m-HMPAO scintigraphy was true-positive for infection in 18 of 28 patients (for a total of 21 sites of uptake) and true-negative in 10 of 28 subjects. SPECT/CT provided an accurate anatomic localization of all positive foci. With regard to the final diagnosis, SPECT/CT added a significant clinical contribution in 10 of 28 patients (35.7%). In fact, SPECT/CT differentiated soft-tissue from bone involvement both in patients with osteomyelitis and in patients with orthopedic implants, allowed correct diagnosis of osteomyelitis in patients with structural alterations after trauma, and identified synovial infection without prosthesis involvement in patients with a knee implant. Conclusion: Our results indicate that SPECT/CT performed using a hybrid device can improve imaging with Tc-99m-HMPAO-labeled leukocytes in patients with suspected osteomyelitis by providing accurate anatomic localization and precise definition of the extent of infection.