PURPOSE: To present a novel clinical application of silicon-photomultiplier-based positron emission tomography (SiPM-based PET)/computed tomography (CT), detecting a type II endoleak 5 years after endovascular aneurysm repair (EVAR). TECHNIQUE: SiPM-based PET/CT scans with a standard whole-body protocol were performed for a 73-year-old man with a past medical history of abdominal aortic aneurysms treated with EVAR and currently under investigation of his duodenal papillary carcinoma. The PET/CT demonstrated 18F-fluorodeoxyglucose (FDG) accumulation outside the stent graft in the native sac of the aneurysm. The site of accumulation corresponded to that of the contrast enhancement depicted in the CT angiography taken 1 month earlier. Another CT scan performed 3 months later revealed enlargement of the aneurysm. CONCLUSION: SiPM-based PET/CT, with its superior sensitivity and spatial resolution over conventional PET/CT, can detect type II low-flow endoleaks.Clinical ImpactAbnormal intra-aneurysmal FDG activity incidentally detected on SiPM-based PET/CT is worthy of attention because it may be indicative of endoleaks. Additional imaging using different modalities should be considered so that the patient would not miss the additional treatment opportunity upon observing sac enlargement. For patients with contraindications for iodine CT contrast media, SiPM-based PET/CT would serve as a suitable alternative.