Cerebral Infarction Mimicking Skeletal Metastases on Tc-99m MDP Bone Scintigraphy / 대한핵의학회잡지

A 60-year-old male with carcinoma of the prostate and cerebral infarction underwent a Tc-99m MDP bone scintigraphy for the evaluation of skeletal metastases. Bone scintigraphy (Fig. 1) showed multiple areas of increased uptake of Tc-99m MDP in the skull, spine, and ribs representing skeletal metastases. Two different patterns of uptake occurred in the skull region (Fig. 1A-C); one represents bony metastasis and the other represents cerebral infarction. The shape, size, location, intensity, and border of the increased uptake differed between the two lesions. An oval-shaped pattern with smaller size, greater intensity and more sharply defined border in the frontal region was consistent with bony metastasis. A rectangular-shaped pattern with larger size, lesser intensity and relatively indistinct border in the temporo-parieto-occipital region was consistent with cerebral infarction. Increased uptake of bone-seeking radiotracers in cerebral infarction has been reported previously.1-4) A suggested mechanism by which bone-seeking radiotracers accumulate in the necrotizing cerebral tissue is an alteration of the blood-brain barrier induced during cerebral infarction, which results in entry of the radiotracers into the extracellular space of the brain.4) Brain CT (Fig. 2) performed 7 days before and one month after the bone scintigraphy revealed lesions on the right temporo-parieto-occipital region consistent with acute hemorrhagic and chronic cerebral infarction, respectively.

Unusual Tc-99m MDP Uptake in the Keloid Developed after Subtotal Gastrectomy / 대한핵의학회잡지

A 63-year-old male who had subtotal gastrectomy for early gastric cancer three months ago underwent Tc-99m bone scintigraphy for the evaluation of skeletal metastases. He had no symptoms such as fever, tenderness, or wound discharge. On physical examination, the surgical scar along the midline of the upper abdomen had keloid formation and there was no radiographic evidence of calcification. Bone scintigraphy (Fig. 1A & 1B) demonstrated an unusual linear increased uptake along the midline of the upper abdomen that corresponded to the skin incision for subtotal gastrectomy. Usually, an incisional scar will not be visualized in Tc-99m methylene diphosphate (MDP) scintigraphy beyond two weeks after surgery.1) Upon reviewing the literature, there were only a few reports where localization of Tc-99m MDP in surgical scars were found two months after surgery.2) It was also reported that a few cases with Tc-99m MDP uptake in the keloid scar developed after surgery. Although there are several potential mechanisms that may explain the uptake of Tc-99m MDP in scar tissue, the primary mechanism in older scars is suggested to be a result of pathological calcification.2) Siddiqui et al3) suggested it could be due to microscopic calcification in small resolving hematomas. However, the primary mechanism in keloid scar is not well-known. We should obtain oblique or lateral views to differentiate the uptake in healing surgical scars from the artifactual uptake.