The novel Gallium-68 prostate-specific membrane antigen (PSMA)-bis [2-hydroxy-5-(carboxyethyl)benzyl] ethylenediamine-diacetic acid positron emission tomography (PET) tracer is increasingly used in the evaluation of prostate cancer, particularly in the detection of recurrent disease. However, PSMA is expressed in nonprostatic tissues, as well as in other pathologic conditions. Here we illustrate such interpretive pitfalls with relevant images that one may encounter while reporting PSMA PET/CT. This study aims to show variation in physiological distribution of PSMA activity and uptake in various benign and neoplastic disorders that may be misinterpreted as prostatic metastatic disease. These pitfalls are illustrated to enhance awareness, aiding a more accurate interpretation of the study. Retrospective database of all (68)Ga PSMA PET/CT was created and reviewed. In total, 1115 PSMA PET/CT studies performed between February 27, 2015, and May 31, 2017, were reviewed. Any unusual uptake of PSMA was documented, described, and followed up. All cases were then subdivided into the following 4 categories: physiological uptake, benign pathological uptake, nonprostatic neoplastic uptake, and miscellaneous uptake. A variety of nonprostatic tissues and lesions, including accessory salivary gland, celiac ganglion, gall bladder, Paget's bone disease, reactive lymph nodes, non–small cell lung cancer, renal cell cancer, and neuroendocrine tumor, were found to show PSMA uptake. PSMA uptake is not prostate-specific and can be taken up physiologically and pathologically in nonprostatic tissue. It is important for reporting physicians to recognize these findings and instigate appropriate investigations when required while avoiding unnecessary procedures in physiological variation.

Summary. Background: Platelet activation is implicated in thrombotic disorders, but has not been described in acute clinical pulmonary embolism (PE). Objectives: To investigate the natural history of platelet activation in PE and associated markers of inflammation, thrombosis and cardiac dysfunction. Methods: Thirty-five consecutive patients (age 62 ± 17 years) with acute PE were prospectively enrolled and followed for 6 months. Platelet activation was assessed by flow cytometry [measuring expression of platelet P-selectin, conformational activation of glycoprotein IIb/IIIa complex (PAC-1) and formation of platelet-leukocyte complexes] and by plasma soluble P-selectin. Platelet activation, right ventricular (RV) function (assessed as RV ejection area by transthoracic echocardiography), D-dimer and high-sensitivity C-reactive protein (hs-CRP) were measured at presentation and repeated over 6 months follow-up. Results: Soluble P-selectin (56 ± 19 ng mL )1 , ANOVA P < 0.0001) and PAC-1 (1.5 ± 1.8%, ANOVA P = 0.005) were mildly but significantly increased in patients with acute PE relative to healthy young men (soluble P-selectin 33 ± 13 ng mL )1 , P < 0.001; PAC-1 binding 0.5 ± 0.6%, P < 0.01) and age-matched controls (soluble P-selectin 31 ± 9 ng mL )1 , P < 0.001; PAC-1 binding 0.4 ± 0.4%, P < 0.05). Platelet P-selectin expression and plateletleukocyte complexes were not increased during acute PE. Echocardiographic RV ejection area correlated inversely with soluble P-selectin (r = )0.47, P = 0.007) and positively with platelet P-selectin (r = 0.49, P = 0.0007), suggesting P-selectin is shed from activated platelets in proportion to the severity of RV dysfunction. Elevated soluble P-selectin, D-dimer and hs-CRP demonstrated a time-dependent return to normal during 6 months follow-up. Conclusion: Platelet activation is evident after acute PE. Platelet activation correlates with the severity of RV dysfunction, and can persist for several months after acute PE.

A 71-year-old man with a background of treated stage IIIB non-small cell lung cancer was referred for Ga prostate-specific membrane antigen (PSMA) PET/CT for staging of prostate cancer. In addition to the PSMA uptake in the known prostate malignancy, the study also demonstrated increased PSMA uptake in an enlarging left lower lobe lung mass with diffusely increased PSMA uptake in an enlarged thyroid gland and bilateral enlarged supraclavicular lymph nodes. Fine-needle aspiration biopsy of the thyroid gland and a left supraclavicular lymph node demonstrated metastatic adenocarcinoma from a primary lung cancer.

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"Thyroid stunning" from diagnostic iodine-131 imaging prior to ablative therapy with (131)I for well-differentiated thyroid carcinoma has been well reported, but documentation of the effect on clinical outcome is sparse. The purpose of this retrospective study was to investigate the clinical effects of stunning. The outcome of (131)I ablative therapy in a group of patients ( n=36) who had diagnostic scans using 185 MBq (5 mCi) of (131)I was compared with that in a group ( n=36) who had diagnostic scans using 740 MBq (20 mCi) of (123)I. Patients were imaged at least 4 weeks after near-total thyroidectomy, prior to their first (131)I ablative therapy. Follow-up imaging was performed every 3-6 months, and further (131)I treatment administered when indicated. A group of patients ( n=36) who proceeded directly to their first therapy dose without a diagnostic scan and were followed up with (123)I was compared with the group who did have a (123)I diagnostic scan prior to the first ablative therapy. The efficacy of therapy was evaluated using ablation of the thyroid, evidenced by absence of uptake in the thyroid bed on the diagnostic scan, as the endpoint. Only 47% of patients in the (131)I diagnostic group had the thyroid gland ablated after a single administration of (131)I therapy, compared with 86% in the (123)I diagnostic group ( P<0.005). Patients who had (131)I diagnostic scans required higher total (131)I therapeutic activity (6.7 GBq or 180 mCi) to ablate the thyroid gland than those in the (123)I diagnostic group (4.4 GBq or 119 mCi). There was no difference in outcome between the group who did and the group who did not have a diagnostic study with (123)I prior to their first ablative therapy. The difference in outcome between the (131)I and the (123)I diagnostic groups demonstrates that the efficacy of (131)I therapy is reduced subsequent to the use of 185 MBq of (131)I for diagnostic imaging. This indicates that the phenomenon of stunning is clinically significant and affects the outcome of therapy.

Femoroacetabular impingement is a recently described condition thought to be associated with early onset osteoarthritis. We describe 2 cases of femoroacetabular impingement that were initially unrecognized despite multimodality imaging, including radiographs, MRI, and scintigraphy. The scintigraphic appearance may mimic avascular necrosis. There are limited reports of femoroacetabular impingement in the nuclear medicine literature. We propose that the finding of increased uptake in the superior femoral neck associated with osteoarthritic uptake involving the superior hip joint suggests the diagnosis of either cam or mixed cam-pincer impingement.

Ga-PSMA PET/CT is increasingly used to evaluate recurrent prostatic malignancy due to its high specificity. A 75-year-old man with a previous history of treated prostate cancer 3 years earlier presented with rising prostate-specific antigen (PSA) level and underwent Ga-PSMA PET/CT which demonstrated a PSMA-avid focus in the neck of the pancreas. Triple-phase abdominal CT demonstrated enhancement in the arterial phase and to a lesser extent the venous phase of a soft tissue mass in the neck of the pancreas. Cytological and histopathological examination of the soft tissue mass confirmed a low-grade pancreatic neuroendocrine tumor.