18 F-FDG PET/CT is of value in the diagnosis of prosthetic vascular graft infection, but potential pitfalls related to tracer uptake in noninfected implants have been described. The current study assesses the incidence and patterns of 18 F-FDG uptake over time in noninfected grafts, in relationship to prosthetic material and location. Methods: A 12-y PET/CT database was retrospectively searched for cancer patients with prosthetic vascular grafts. Data retrieved from patient files included graft location, material, and time from surgery. Images were reviewed by 2 nuclear medicine physicians in consensus, with the presence and patterns (focal, diffuse homogeneous, inhomogeneous) of increased 18 F-FDG uptake in grafts recorded. The mean standardized uptake value in grafts (SUV-G) and mediastinum (SUV-M) was measured. The ratio of SUV-G to SUV-M (SUV-G/SUV-M) was calculated for each graft. Results: One hundred seven prostheses were identified in 102 studies in 43 cancer patients. Sixty-seven prostheses were made of Dacron, 33 of Gore-Tex, and 7 were native veins. No increased 18 F-FDG uptake was found in 9 grafts (native veins, 4; Gore-Tex, 3; Dacron, 2). There was diffuse homogeneous uptake in 68 and inhomogeneous uptake in 30 grafts. The homogeneous pattern was more prevalent in Gore-Tex whereas the inhomogeneous uptake was seen more in Dacron vascular grafts. None of the grafts demonstrated focal uptake. The SUV-G range was 0.4-6.3 (average, 1.9), and SUV-M range was 0.6-2.4 (average, 1.4). The intensity of uptake was significantly higher in Dacron (SUV-G 5 2.35 and SUV-G/ SUV-M 5 1.72) than in Gore-Tex (SUV-G 5 1.09, SUV-G/SUV-M 5 0.91) and native vein grafts (SUV-G 5 1.07, SUV-G/SUV-M 5 0.75) (P , 0.005). Native vein grafts showed a significant decrease in 18 F-FDG uptake over time whereas synthetic grafts showed no change in intensity for a follow-up of up to 16 y. Conclusion: Diffuse 18 F-FDG uptake was found in 92% of noninfected vascular prostheses, more in Dacron grafts than with other materials. The intensity of 18 F-FDG uptake of synthetic grafts did not change over time. With knowledge of the presence, patterns, and persistence of 18 F-FDG uptake in noninfected vascular prostheses, misinterpretation of PET/CT studies in patients referred for suspected prosthetic infection and in those assessed for diseases unrelated to their graft status can be avoided.

Background68Ga-PSMA PET/CT has an important role in assessment of prostate cancer patients with biochemical recurrence and is evolving in staging high- and intermediate risk disease. The aim of present study was to describe the metastatic patterns and frequency of involved sites of prostate cancer and to assess the incidence of benign Ga68-PSMA avid PET/CT findings in a large patient population.Methods68Ga-PSMA PET/CT studies performed in two tertiary medical centers over a period of 24 months were retrospectively reviewed. The incidence and location of pathological 68Ga-PSMA avid foci, suspicious to represent malignancy, as well as those of unexpected benign foci of increased 68Ga-PSMA activity were documented and analyzed.ResultsThere were 445 68Ga-PSMA studies in 438 men (mean age 72.4, range 51–92 years) with prostate cancer referred for biochemical failure (n = 270, 61%), staging high-risk disease (n = 112, 25%), response assessment (n = 30, 7%), follow-up (n = 22, 5%) and suspected bone metastases (n = 11, 2%). 68Ga-PSMA avid disease sites were observed in 319 studies (72%), in 181 studies (67%) for biochemical recurrence, 94 studies for staging (84%) (p < 0.05), in 22 studies for response assessment (73%), 10 follow up studies (45%) and in five patients with suspected bone metastases (45%). 68Ga-PSMA avid lesions were most commonly detected in the prostate (n = 193, 43%), loco-regional spread (n = 51, 11%), abdomino-pelvic nodes (n = 129, 29%) and distant metastases (n = 158, 36%), including bone metastases (n = 11, 25%), distant lymphadenopathy (n = 29, 7%) and other organs (n = 18, 4%). Distant 68Ga-PSMA-avid metastases were commonly seen in patients with biochemical recurrence (14/21 lesions), but were not seen in patient referred for staging (p < 0.013). There were 96 non-malignant 68Ga-PSMA avid foci in 81 studies, most common in reactive lymph nodes (n = 36, 38%), nonmalignant bone lesions (n = 21, 22%), thyroid nodules (n = 9, 9%), ganglions (n = 9, 9%) and lung findings (n = 8, 8%).ConclusionThe distribution of 68Ga-PSMA avid metastatic lesions is similar to data previously reported mainly from autopsy with comparable detection rates, indicating 68Ga-PSMA PET/CT is an accurate detection tool in patients with metastatic prostate cancer. If confirmed by further prospective studies 68Ga-PSMA PET/CT should be included in the guidelines to evaluate disease extent in these patients.

Previously unreported benign sites of 68Ga-DOTA-NOC uptake were found in the majority of studies, suggesting the presence of somatostatin receptors in physiologic variants or processes with no evidence of tumor. Knowledge of increased tracer uptake in non-NET-related sites is important for accurate interpretation and for avoiding potential pitfalls of 68Ga-DOTA-NOC PET/CT.