Image-mode performance characterisation of a positron emission tomography subsystem designed for Biology-guided radiotherapy (BgRT).

OBJECTIVES: In this study, we characterise the imaging-mode performance of the positron emission tomography (PET) subsystem of the RefleXion X1 machine using the NEMA NU-2 2018 standard. METHODS: The X1 machine consists of two symmetrically opposing 900 arcs of PET detectors incorporated into the architecture of a ring-gantry linear accelerator rotating up to 60 RPM. PET emissions from a tumour are detected by the PET detectors and used to guide the delivery of radiation beam. Imaging performance of the PET subsystem on X1 machine was evaluated based on sensitivity of the PET detectors, spatial resolution, count-loss performance, image quality, and daily system performance check. RESULTS: PET subsystem sensitivity was measured as 0.183 and 0.161 cps/kBq at the center and off-center positions, respectively. Spatial resolution: average FWHM values of 4.3, 5.1, and 6.7 mm for the point sources at 1, 10, and 20 cm off center, respectively were recorded. For count loss, max NECR: 2.63 kcps, max true coincidence rate: 5.56 kcps, and scatter fraction: 39.8%. The 10 mm sphere was not visible. Image-quality contrast values were: 29.6%, 64.9%, 66.5%, 81.8%, 81.2%, and background variability: 14.8%, 12.4%, 10.3%, 8.8%, 8.3%, for the 13, 17, 22, 28, 37 mm sphere sizes, respectively. CONCLUSIONS: When operating in an imaging mode, the spatial resolution and image contrast of the X1 PET subsystem were comparable to those of typical diagnostic imaging systems for large spheres, while the sensitivity and count rate were lower due to the significantly smaller PET detector area in the X1 system. Clinical efficacy when used in BgRT remains to be validated. ADVANCES IN KNOWLEDGE: This is the first performance evaluation of the PET subsystem on the novel BgRT machine. The dual arcs rotating PET subsystem on RefleXion X1 machine performance is comparable to those of the typical diagnostic PET system based on the spatial resolution and image contrast for larger spheres.

Evaluating the serological status of COVID-19 patients using an indirect immunofluorescent assay, France.

An indirect immunofluorescent assay was developed in order to assess the serological status of 888 RT-PCR-confirmed COVID-19 patients (1,302 serum samples) and controls in Marseille, France. Incorporating an inactivated clinical SARS CoV-2 isolate as the antigen, the specificity of the assay was measured as 100% for IgA titre [≥] 1:200; 98.6% for IgM titre [≥] 1:200; and 96.3% for IgG titre [≥] 1:100 after testing a series of negative controls as well as 150 serums collected from patients with non-SARS-CoV-2 Coronavirus infection, non-Coronavirus pneumonia and infections known to elicit false-positive serology. Seroprevalence was then measured at 3% before a five-day evolution up to 47% after more than 15 days of evolution. We observed that the seroprevalence as well as the titre of specific antibodies were both significantly higher in patients with a poor clinical outcome than in patients with a favourable evolution. These data, which have to be integrated into the ongoing understanding of the immunological phase of the infection, suggest that serotherapy may not be a therapeutic option in patients with severe COVID-19 infection. The IFA assay reported here is useful for monitoring SARS-CoV-2 exposure at the individual and population levels.

Repeated Thrombosis After Synthetic Cannabinoid Use.

BACKGROUND: Synthetic cannabinoids are swiftly gaining popularity and have earned a reputation of being relatively safer than other illicit drugs. However, there is a growing body of literature associating thromboembolic events with their use. CASE REPORT: A 32-year-old woman presented on four separate occasions with a new thromboemoblic event after smoking synthetic cannabinoids. She had no medical history, and over the span of 9 months she developed two kidney infarcts, pulmonary emboli, and an ischemic stroke. Each of these events occurred within 24 hours of smoking synthetic cannabinoids. During periods of abstinence, she remained free of thrombotic events. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This report shows that an association between thrombosis and the use of synthetic cannabinoids is reproducible and involves both venous and arterial thrombosis, suggesting activation of coagulation or inflammatory pathways. As the popularity of this drug continues to grow, we can expect to see a growing number of these cases. Synthetic cannabinoid use should be included in the differential diagnosis of young patients with no risk factors who present with venous or arterial thrombosis.

Ewing's sarcoma: A case report of a 52-year-old woman with recurrent tumor and literature review.

Ewing's sarcoma is the second most common primary sacral tumor. Ewing's sarcomas are rare, aggressive tumors with a tendency towards recurrence following resection and early metastasis. Although peak incidences are between the ages of 10 and 20 years, patients of younger or older age account for almost 30% of the cases. We report the case of a 52-year-old healthy female who presented with a 2-week history of pain in her right posterior thigh that was unable to be relieved by non-steroidal anti-inflammatory medicine and physical therapy. Magnetic resonance imaging demonstrated an irregular right presacral mass and core needle biopsy revealed a small, round blue cell neoplasm. Staging workup was normal and an open biopsy was positive for the ES translocation (22q12). The patient was treated with 17 cycles of vincristine, adriamycin and cytoxan with mesna rescue, alternating with ifosfamide and etoposide in addition to external beam radiation. Post-treatment imaging demonstrated complete resolution of the tumor. Six weeks post-treatment the patient presented with a recurrent tumor. This case emphasizes the importance of timely establishment of initial diagnosis, early metastasis in treatment responsive patients and under-utilization of positron emission tomography-computed tomography (PET-CT) during the treatment to detect sub-clinical metastasis.

Cardiac arrhythmias and sudden unexpected death in epilepsy (SUDEP).

Sudden unexpected death in epilepsy (SUDEP) is a major clinical problem in epilepsy patients in the United States, especially those with chronic, uncontrolled epilepsy. Several pathophysiological events contributing to SUDEP include cardiac arrhythmias, respiratory dysfunction, and dysregulation of systemic or cerebral circulation. There is a significant body of literature suggesting the prominent role of cardiac arrhythmias in the pathogenesis of SUDEP. There is evidence to say that long-standing epilepsy can cause physiological and anatomical autonomic instability resulting in life-threatening arrhythmias. Tachyarrhythmias, bradyarrhythmias, and asystole are commonly seen during ictal, interictal, and postictal phase in epilepsy patients. It is unclear if these rhythm disturbances need attention as some of them may be just benign findings. Evidence regarding prolonged cardiovascular monitoring or the benefit of pacemaker/defibrillator implantation for primary or secondary prevention in epilepsy patients is limited. Awareness regarding pathophysiology, cardiac effects, and management options of SUDEP will become useful in guiding more individualized treatment in the near future. (PACE 2011; 1-8).

A review of risk factors for stroke in patients with chronic kidney disease.

BACKGROUND: Patients with chronic kidney disease (CKD) are at higher risk for stroke because of higher prevalence of traditional and non-traditional cardiovascular risk factors. METHODS: We performed an extensive literature review with pre-defined keywords. We summarized the results of the studies evaluating for risk factors predisposing to stroke in CKD patients. RESULTS: The incidence of stroke and stroke-related mortality is higher in CKD patients compared with the general population. Presence of anemia, hypoalbuminemia, malnutrition, uremia, and hyperhomocysteinemia in patients with CKD is associated with higher incidence of stroke. Hemodialysis and renal transplant patients are at higher risk of developing stroke compared with those who do not require renal replacement therapy. CONCLUSION: The early recognition of risk factors associated with stroke in CKD population is imperative. Early interventions may potentially decrease the incidence and associated mortality of stroke in CKD patients.