LEARN NUCLEAR MEDICINE
Musculoskeletal · Case 04
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IMAGE PLACEHOLDER · Diagnostic study
Original study · Companion image placeholders
Clinical history
A 48-year-old male status post left below the knee amputation (BKA) presents with a malodorous purulent drainage near the incision. A triple-phase bone scan was ordered, and the results are shown below.
Initial blood flow (inject and begin imaging)
Blood pool (2 minutes)
Delayed (3 hours)
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Osteomyelitis
Imaging Findings
Increased activity is seen in the site of the left BKA on all three phases of the bone scintigraphy (flow, blood pool, and delayed imaging).
Essential Facts
Osteomyelitis is inflammation of the bone marrow secondary to infection. Patients often present with fever, focal pain, and swelling of the region. Common routes for spread of osteomyelitis are haematogenous, contiguous and direct inoculation.
Smokers, IV drug users, and people with chronic health conditions are more at risk of developing osteomyelitis. For example, diabetic foot ulcers can result in osteomyelitis in the feet. Trauma and open injuries are also risk factors.
Staphylococcus aureus is the causative organism in up to 80% of cases of osteomyelitis. Early detection is important for prompt antibiotic therapy, to prevent necrosis of the bone.
Scan Information
Gallium-67 citrate scan is a type of nuclear medicine test that employs gallium-67 or 68 radiopharmaceuticals to image a specific type of tissue. Gallium is taken up by tumors, inflammation, and infections, making it useful to identify osteomyelitis. This technique has a high sensitivity, but lacks specificity. Other common indications include whole-body surveys and pulmonary/mediastinal inflammation. T-99m MDP three-phase bone scans utilizes additional scans at different points after the injection to determine additional diagnostic information. The 1st phase is the imaging immediately after injecting. The 2nd phase is when blood pools (around 2 minutes), and the 3rd phase is delayed (3 hours). This can be useful when distinguishing between cellulitis from osteomyelitis, as the latter requires prolonged treatment. A triple-phase bone scan would show increased uptake on all phases with osteomyelitis, while cellulitis would be positive for flow and blood pool only.
References
Mettler, F., Milton, G. Eseentials of Nuclear Medicine Imaging. Philadelphia: Saunders, 2006.
Federle, Michael. “Ureteropelvic Junction Obstruction”. Statdx. 2011. Amirsys,
Ziessman H., O’Malley J, Thrall J. Nuclear Medicine: The Requisites in Radiology. Philadelphia: Elsevier, 2006.
Nuclear Medicine Case Review Series, by Harvey A. Ziessman, Elsevier, 2011, p. 11-13.