Physiologic prostate-specific membrane antigen-targeted 18F-DCFPyL uptake in the epididymis head newly appreciated on digital PET/CT.

PURPOSE: The published physiological distribution of prostate specific membrane antigen (PSMA) PET ligands includes normal uptake in the lacrimal glands, salivary glands, bowel, liver, spleen, kidneys and parasympathetic ganglia but does not include the epididymis. METHODS: Retrospective review of 134 PSMA-targeted 2-(3-(1-carboxy-5-[(6-[18F]fluoropyridine-3-carbonyl)-amino]-pentyl)-ureido)-pentanedioic acid (18F-DCFPyL) PET/CT scans performed on a latest generation digital scanner for radiotracer uptake in the epididymal head region was correlated with multiple clinical and laboratory factors. RESULTS: Physiologic PSMA radiotracer uptake in the epididymal head region was present in 57% of all subjects, including 29% in those with a total serum testosterone ≤ 5 nmol/L and 65% of patients with serum testosterone > 5 nmol/L, odds ratio of 0.21 (P < 0.01). CONCLUSION: Epididymal head uptake is physiologic and very common on digital PSMA PET/CT and is more frequent in patients with higher serum testosterone levels. The enhanced small structure detection of digital PET/CT is the most likely explanation for the novel visualization of this normal variant.

Weight loss as primary indication for FDG-PET/CT.

PURPOSE: Some consider fluorodeoxyglucose positron emission tomography with computed tomography (FDG-PET/CT) clinically useful in patients presenting with nonspecific symptoms of malignancy, weight loss most commonly encountered. However, the appropriateness of such FDG-PET/CT studies remains to be clarified. This study evaluated the clinical value of FDG-PET/CT in patients referred primarily for weight loss. METHODS: From 2010 to 2017 in one academic center, 252 subjects underwent 254 FDG-PET/CT studies for weight loss as primary indication and retrospectively studied. Eighteen subjects were excluded due to ongoing active malignancy, weight loss not ultimately being the main indication for the FDG-PET/CT, technically inadequate FDG-PET/CT and insufficient follow-up. The FDG-PET/CT scans were considered clinically beneficial when true positive for the cause of weight loss that other investigations missed or would have missed, clinically neutral when true negative and clinically detrimental when false positive leading to additional investigations or false negative. RESULTS: Ultimately 234 unique subjects (236 FDG-PET/CT studies) were included. The average subject weight loss prior to the PET was 12 kg and average follow-up time post FDG-PET/CT scan was 3.4 years. The FDG-PET/CT scans were true positive in 24 studies (10%) with 8 studies (3%) clinically beneficial; false positive in 38 studies (16%) of which 26 led to 35 additional procedures and false negative in 13 studies (6%). In total, 39 (17%) FDG-PET/CT studies were clinically detrimental. The other 149 (63%) studies were true negative, clinically neutral. CONCLUSION: FDG-PET/CT appears to have limited value in assessing subjects with weight loss as the leading clinical indication, proving to be five times more often detrimental than beneficial.

Investigation into the effect of transcranial direct current stimulation on cardiac pacemakers.

BACKGROUND: Studies investigating the therapeutic applications of transcranial direct current stimulation (tDCS) in the treatment of age-related neurodegenerative disease have been promising. However, exclusion criteria for these studies invariably disqualify patients implanted with internal cardiac pacemakers, citing safety concerns. Because the majority of cardiac pacemaker implantees are over 65, this criterion may limit candidacy for tDCS based research and/or treatment of age-related neurodegenerative disease. OBJECTIVE/HYPOTHESIS: We will test the hypothesis that tDCS impacts pacemaker function. Strong electrical potentials, such as those generated by external defibrillators (∼500 V, ∼10 A), are known to occasionally damage pacemaker circuitry and software, but it seems unlikely tDCS would damage a pacemaker because it involves about 1/200th the energy (∼12 V, ∼2 mA) of an external defibrillator. METHODS: We delivered tDCS to seven participants (ages 70-92) with bipolar non-dependent pacemakers and subsequently collected data from the internal memory of the pacemakers to assess the tDCS signal detection, as well as alterations in mode switches, impedance levels, and pacing. Subsequently, similar assessments were carried out in participants who were pacemaker-dependent (ages 89-91). RESULTS: After a review of the recordings, it was found that tDCS had no impact on the non-dependant, as well as the dependent, pacemakers. There were zero mode switches nor any impact on impedance levels. CONCLUSION: Results in this small series of cases found no evidence that tDCS interferes with the function of the pacemakers and suggests tDCS can be delivered to patients equipped with a cardiac pacemaker. Further studies are needed to generalize these results to other pacemakers.

18F-FDG PET/CT versus conventional investigations for cancer screening in autoimmune inflammatory myopathy in the era of novel myopathy classifications.

BACKGROUND: To compare the performance of fluorine-18-fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) and conventional tests for cancer screening in autoimmune inflammatory myopathy (AIM) patients. PATIENTS AND METHODS: We carried out a retrospective cohort study of AIM patients from one academic center in Montreal, Canada, classified using myositis-specific antibodies, who underwent F-FDG PET/CT between April 2005 and February 2018 and were followed up on average 3.5±2.4 years. Patients were excluded if follow-up was insufficient, AIM diagnosis was indeterminate, and/or malignancy was diagnosed before an F-FDG PET/CT scan. Demographic/clinical data, F-FDG PET/CT results, and available conventional screening tests results were retrieved from electronic and paper medical records. RESULTS: 100 F-FDG PET/CT studies in 63 unique patients [31/63 dermatomyositis (DM), 25/63 overlap myositis, 1/63 inclusion body myositis, 1/63 polymyositis, 1/63 orbital myositis and 4/63 unspecified myositis] were evaluated. Three patients, all classified as DM, were diagnosed with cancer during follow-up with conventional cancer screening tests: breast cancer detected by mammography; squamous cell carcinoma of the skin detected by physical examination; and multiple myeloma detected by blood work. F-FDG PET/CT did not detect any malignancy and led to more additional biopsies than conventional screening (8 vs. 5). CONCLUSION: F-FDG PET/CT does not appear to be useful in cancer screening for AIM patients compared with conventional screening and carries potential harms associated with follow-up investigations. The risk of cancer in AIM differs by myositis-specific antibodies-defined subsets and cancer screening is likely to be indicated only in high-risk patients, particularly DM. These results, replicated in larger, multicentered studies, may carry significant consequences for optimal management of AIM and health resource utilization.