LEARN NUCLEAR MEDICINE
Musculoskeletal · Case 02
Read the history, inspect the study, then reveal the teaching.
IMAGE PLACEHOLDER · Diagnostic study
Original study · Companion image placeholders
Clinical history
A 16-year-old male presents to the ED due to lower extremity pain with activity. He is a member of his highschool track team. Local tenderness and swelling is noted on physical exams. His bone scan is provided below.
Read the images before opening the teaching panel below.
Bilateral metatarsal stress fractures
Imaging Findings
Intense activity in the left metatarsal bone. To a lesser degree there is uptake within a left metatarsal bone. A SPECT/CT could help further localize the abnormality.
Essential Facts
The dynamic nature of bones allows intermittent forces to stimulate remodeling of bone architecture to withstand applied stresses. Osteoclast stimulation during stress injury can lead to microfractures and remodeling within lamellar bone. Increased bone turnover can be seen on bone scans as focal intensities.
When bone formation cannot keep up with resorption, bone weakening results. Repair mechanisms can become overwhelmed if the stress is not reduced, resulting in fracture.
Risk factors include repetitive, high-impact sports (running long distances), osteoporosis, vitamin D deficiency
Scan Information
A whole body bone scintigraphy scan images the metabolic activity of the skeleton by imaging a radionuclide that closely mimics a metabolic process within bone. Nuclear scintigraphy of the bone commonly uses the radionuclides technetium-99m (Tc-99m) or fluoride-18 (F-18) for Positron Emission Tomography exams. Tc-99m is usually attached to medronic acid (Tc-99m MDP), and F-18 is usually incorporated into sodium fluoride (F-18 NaF). Once these molecules are injected, a nuclear camera that contains a salt crystal captures the decay of photons from the radioisotope. The process of scintillation, when the photon emitted by the radionuclide hits the salt crystal within the nuclear camera, allows for this to be achieved. The scintillations are converted to images for interpretation. The radionuclide bone scan is an excellent modality to detect metastases, fracture, and osteomyelitis vs. cellulitis.
References
Nuclear Medicine Case Review Series, by Harvey A. Ziessman, Elsevier, 2011, p. 5-6.
Heston, Thomas. “Bone Scan.” Background, Indications, Contraindications, 31 Mar. 2020, emedicine.medscape.com/article/2109077-overview.