Noninvasive Detection of Active Microcalcification in an Occlusive Peripheral Vascular Aneurysm Using 18F-NaF PET/CT Imaging

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  FIGURE 1. CT and digital subtraction angiography (DSA) in a 65-year-old man with peripheral arterial disease (PAD), calf claudication, and an occluded popliteal aneurysm. Four years ago, the patient developed moderate claudication, which resulted in evaluation by CT angiography (A–E) that revealed occlusion of the popliteal artery proximal to the knee (B) and at the site of an extensively calcified aneurysm at the level of the knee (C). CT angiography also demonstrated that the popliteal artery was reopacified distally by collateral vessels (D). The trifurcation distal to the popliteal remained unremarkable with 3-vessel runoff (E). One month after CT angiography, there was worsening of claudication symptoms that led to an abdominal aortogram with runoff using DSA (F). DSA demonstrated popliteal artery occlusion above and at the level of the knee, with reconstitution slightly below the knee and 3-vessel runoff. No intervention was performed, and medical management with aspirin and acetaminophen as well as recommendations for smoking cessation and walking therapy were pursued. Cilostazol was prescribed, which resulted in marked improvement of symptoms, thereby enabling conservative…

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  FIGURE 2. 18F-NaF PET/CT imaging of peripheral atherosclerosis. Four years after angiography imaging, the man continued to have mild claudication symptoms and had an ankle-brachial index of 0.62 and a toe-brachial index of 0.47. At this time, he was prospectively enrolled into an ongoing study evaluating the prognostic value of radiotracer-based imaging in PAD patients (https://clinicaltrials.gov, NCT03622359). As an additional component of this study, PET/CT imaging was performed 75 minutes after IV injection of 18F-NaF (370 MBq) to assess the status of active microcalcification in lower extremity arteries. CT imaging detected the extensive macrocalcification of the popliteal aneurysm (A, arrows) that colocalized with the elevated retention of 18F-NaF around the calcified aneurysm on PET (B, arrows) and PET/CT images (C, arrows), suggesting ongoing remodeling of the aneurysm. PET/CT also demonstrated increased focal uptake of 18F-NaF in 2 distal vascular sites (B and C, arrows) that did not coincide with prominent macrocalcification on CT images, thereby indicating potential early stages of microcalcification in additional atherosclerotic plaques. 18F-NaF PET/CT imaging has emerged as a…