The Fruit of Labour - “Wonder Woman” Sign on ¹⁸F FDG PET/CT

¹⁸F FDG PET/CT in a 40-year-old woman evaluated for suspected inflammatory bowel disease incidentally demonstrated symmetric increased tracer uptake in the bilateral forearms, hands, legs, and feet [Fig 1]. This pattern of muscle uptake, due to the patient’s activity of walking about and wringing her hands due to anxiety during the uptake period of ¹⁸F FDG postinjection, resembles the forearm bracelet and boots worn by Wonder Woman, a fictional comic character. Skeletal muscles constitute a large bulk of our body mass and are one of the major utilisers of glucose.^[1] Conditions such as paralysis, exertion, or stress prior to scanning can result in increased uptake in particular muscle groups used, leading to unusual patterns on FDG PET/CT such as “bilateral hot forearm sign,”^[2] “monocle” sign,^[3] incomplete V sign^[4] and many more. A number of reviews and case reports are available in the literature^[1,5-8] highlighting the pitfalls of muscle uptake on ¹⁸F FDG PET/CT, enumerating the various forms of physiological and pathological uptake, their causes and mitigation. As a nuclear medicine physician, it is important to be aware of such unusual patterns of FDG uptake and inquire about relevant history from patients to know various reasons for the occurrences of the same. Measures such as proper patient preparation, rest in a warm and quiet place during the uptake phase and counselling them regarding the effects of noncompliance with instructions will lead to better quality images for interpretation, avoid false positive findings, and masking of pathological findings due to physiological uptake.

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Fig 1: (A) Maximum-intensity projection images of ¹⁸F Fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F FDG PET/CT) of a 40-year-old woman who was referred to our department with complaints of generalised weakness, altered bowel habits and abdominal pain, with a suspicion of inflammatory bowel disease, shows incidental finding of increased tracer uptake in the regions of bilateral forearms (black arrows), bilateral hands (orange arrows), bilateral legs (blue arrows), and bilateral feet (green arrows), (B) Transaxial CT and fused PET and CT images show symmetrical hypermetabolism in the flexor and extensor muscle groups of bilateral forearms, (C) muscles in the dorsum of bilateral hands, and (D) in flexor and extensor compartments of bilateral legs. FDG: Fluorodeoxyglucose; PET: Positron emission tomography; CT: Computed tomography;

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