To determine whether the fast iterative reconstruction method, the ordered-subset expectation maximum (OSEM), is more effective, essentially from a qualitative point of view than classical FBP for bone SPECT in the routine clinical context in patients of painful back and its clinico-radiological correlation.
Thirty four patients referred to the department with low back pain had undergone planar bone scan and SPECT as per standard protocol in a dual head gamma camera. The regions of interest are the pelvic, lumbar spine and the thoraco-lumbar spine. Also,10 patients with no complaints of back pain but referred to the department for bone scanning for some other indications are taken for SPECT imaging, which are considered as controls for image analysis. All acquired raw images were reconstructed by two different SPECT reconstruction methods i.e. FBP and OSEM. Transverse, coronal and sagittal slices are generated and displayed with a gray scale. The images of two different SPECT reconstruction techniques were compared with four parameters (1) the visibility of vertebra (2) vertebral processes (3) spinalcanal (4) the overall impression of the images. A brief history of each patient, other radiologic finding like MRI and X rays are then compared with the localized lesions in SPECT images of FBP and OSEM separately for each patient.
The majority of patients belong to group of 31–45 years of age (35%). 32% of patients belong to 46–60 years of age group. All patients are symptomatic and show 51 lesions in MRI Planar bone scans findings show abnormality in 21 (62%) patients and normal in 13 (38%) patients. 27 patients (80%) show abnormal SPECT. 45 lesions are found on FBP SPECT with maximum lesion at the level of L5-S1. The body and pedicles involvement are the most common among the detected lesions. 28 patients (82%) shows abnormal SPECT. 45 lesions are found on OSEM SPECT.
Symptoms of 62% of patients of chronic back pain correlates with the planar bone scintigraphy while symptoms of 80% of patients correlates with bone SPECT. MR imaging shows good agreement with SPECT scintigraphy but the maximum lesion missed on SPECT scintigraphy, are picked up by MRI which are at the level of L5-S1 vertebrae. OSEM and FBP shows good agreement (Kappa 0.90) while 56% of lesions are definitely better visualized in OSEM algorithm. Streak artifacts are absent in OSEM as compared with FBP but the sensitivity for lesion detection is same with both SPECT reconstruction methods.
Back pain, SPECT, OSEM, FBP
