3-phase bone scan: The blood flow images (phase 1) in the above video show early increased blood flow to the region of right iliac crest. Blood pool images (phase 2) show persistent increased activity in the soft tissues of this region (more medial linear activity is excreted radiotracer in the right ureter). The delayed/osseous images (phase 3) show subtly increased MDP uptake in the right crest compared to the left, which can be seen on both anterior and posterior views.
Although a 3-phase bone scan is usually obtained to evaluate for osteomyelitis, other conditions can also result in a positive study on all 3 phases:
The imaging findings above are diagnostic of right iliac crest osteomyelitis given the clinical setting. However the patient also underwent an MRI given this unusual diagnosis in someone presenting with hip pain.
MR images show loss of normal T1 marrow signal in the right iliac crest, with associated edema/enhancement, confirming the diagnosis of osteomyelitis. Post contrast image demonstrates enhancement and small fluid collections/abscesses in the gluteus and iliopsoas muscles and adjacent fascia, compatible with associated myositis.
Much of the data investigating the accuracy of nuclear medicine studies for the diagnosis of acute osteomyelitis has focused on the neuropathic foot:
Ell PJ, Ghambhir SS, eds. Nuclear Medicine in Clinical Diagnosis and Treatment, 3rd Ed. Elsevier, 2004. Ziessman HA, O’Malley JP, Thrall JH, eds. Nuclear Medicine, the Requisites, 4th ed. Philadelphia: Elsevier, 2014.
The 3 phase bone scan has high sensitivity and may be useful to “rule out” osteomyelitis in the correct clinical setting. This study does suffer from poor specificity, especially in the setting of prior trauma or surgery. Note however that in the setting of a normal radiograph (as in our patient), the specificity of 3-phase bone scan increases to 90-95% and represents a viable option in this situation. Schauwecker DS. The scinitgraphic diagnosis of osteomyelitis. AJR 1992;158:9-18.
