[18F]FDG-PET/CT in mechanically ventilated critically ill patients with COVID-19 ARDS and persistent inflammation.

Purpose: We report the findings of four critically ill patients who underwent an [18F]FDG-PET/CT because of persistent inflammation during the late phase of their COVID-19.Methods: Four mechanically ventilated patients with COVID-19 were retrospectively discussed in a research group to evaluate the added value of [18F]FDG-PET/CT.Results: Although pulmonary PET/CT findings differed, bilateral lung anomalies could explain the increased CRP and leukocytes in all patients. This underscores the limited ability of the routine laboratory to discriminate inflammation from secondary infections. Based on PET/CT findings, a secondary infection/inflammatory focus was suspected in two patients (pancreatitis and gastritis). Lymphadenopathy was present in patients with a detectable SARS-CoV-2 viral load. Muscle uptake around the hips or shoulders was observed in all patients, possibly due to the process of heterotopic ossification.Conclusion: This case series illustrates the diagnostic potential of [18F]FDG-PET/CT imaging in critically ill patients with persistent COVID-19 for the identification of other causes of inflammation and demonstrates that this technique can be performed safely in mechanically ventilated critically ill patients.</p

Current and Future Use of Long Axial Field-of-View Positron Emission Tomography/Computed Tomography Scanners in Clinical Oncology

The latest technical development in the field of positron emission tomography/computed tomography (PET/CT) imaging has been the extension of the PET axial field-of-view. As a result of the increased number of detectors, the long axial field-of-view (LAFOV) PET systems are not only characterized by a larger anatomical coverage but also by a substantially improved sensitivity, compared with conventional short axial field-of-view PET systems. In clinical practice, this innovation has led to the following optimization: (1) improved overall image quality, (2) decreased duration of PET examinations, (3) decreased amount of radioactivity administered to the patient, or (4) a combination of any of the above. In this review, novel applications of LAFOV PET in oncology are highlighted and future directions are discussed.</p

A Case of Clinical Uncertainty Solved: Giant Cell Arteritis with Polymyalgia Rheumatica Swiftly Diagnosed with Long Axial Field of View PET

The clinical presentation of giant cell arteritis (GCA) is often nonspecific. Differentiating GCA from infectious, malignant, or other autoimmune pathology based on signs, symptoms, and laboratory parameters may therefore be difficult. Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) imaging is an established tool in the diagnostic workup of GCA. An advantage of 18F-FDG-PET/CT is its ability to assist in the differential diagnosis by being able to demonstrate infection, inflammation, and malignancy when used in conjunction with clinical and laboratory data. Downsides to the use of 18F-FDG-PET/CT include its relatively low spatial resolution, associated radiation exposure, and the relatively long duration of imaging, causing limited availability and patient inconvenience. The advent of long axial field-of-view (LAFOV) PET/CT systems allows for PET imaging at a reduced imaging time or reduced tracer dose while maintaining high image quality. Here, we provide the first reported case of a patient with GCA and polymyalgia rheumatica (PMR) diagnosed using LAFOV PET/CT imaging. The patient presented in this case report had already been experiencing nonspecific symptoms for several years for which no cause was found. Lab investigations showed increased inflammatory parameters as well as persistent anemia. 18F-FDG LAFOV PET/CT attained high-quality images with clear signs of GCA and PMR even at 1 min of scan duration

Capillary gravity waves on the free surface of an inviscid fluid of infinite depth. Existence of solitary waves

Purpose Neuroendocrine tumors (NETs) can produce neuroendocrine amines resulting in symptoms. Selecting the most active amine-producing tumor lesions for local treatment might be beneficial for patients with metastatic small intestinal NET. Tumor burden correlates with catecholamine pathway activity. We analyzed interlesional heterogeneity with 18F-DOPA PET scans in patients with small intestinal NET and investigated if lesions with substantially higher 18F-DOPA uptake could be identified. Methods In this retrospective, observational study, the 18F-DOPA uptake was calculated by dividing SUVpeak of the lesion by the SUVmean of the background organ. The magnitude of heterogeneity between lesions within a patient was calculated by dividing the lesion with the highest by the one with the lowest 18F-DOPA uptake. Lesions with a higher 18F-DOPA uptake than the upper inner or outer fence (>1.5 or 3 times the interquartile range above the third quartile) were defined as lesions with mild or extreme high 18F-DOPA uptake, respectively, and presence of these was determined in patients with 10 lesions or more. Results 18F-DOPA was detected over 680 lesions in 38 patients, of which 35 were serotonin producing. 18F-DOPA uptake varied with a median of 8-fold up to 44-fold between lesions within a patient. In 12 of 20 evaluable patients, lesions with mild high 18F-DOPA uptake were found, and in 5, lesions with extreme high 18F-DOPA uptake. Conclusions 18F-DOPA-PET showed considerable heterogeneity in 18F-DOPA uptake between tumor lesions and identified lesions within patients with mild or extreme high 18F-DOPA uptake

Extending the clinical capabilities of short- and long-lived positron-emitting radionuclides through high sensitivity PET/CT

This review describes the main benefits of using long axial field of view (LAFOV) PET in clinical applications. As LAFOV PET is the latest development in PET instrumentation, many studies are ongoing that explore the potentials of these systems, which are characterized by ultra-high sensitivity. This review not only provides an overview of the published clinical applications using LAFOV PET so far, but also provides insight in clinical applications that are currently under investigation. Apart from the straightforward reduction in acquisition times or administered amount of radiotracer, LAFOV PET also allows for other clinical applications that to date were mostly limited to research, e.g., dual tracer imaging, whole body dynamic PET imaging, omission of CT in serial PET acquisition for repeat imaging, and studying molecular interactions between organ systems. It is expected that this generation of PET systems will significantly advance the field of nuclear medicine and molecular imaging

Shortened duration whole body 18F-FDG PET Patlak imaging on the Biograph Vision Quadra PET/CT using a population-averaged input function

Background: Excellent performance characteristics of the Vision Quadra PET/CT, e.g. a substantial increase in sensitivity, allow for precise measurements of image-derived input functions (IDIF) and tissue time activity curves. Previously we have proposed a method for a reduced 30 min (as opposed to 60 min) whole body 18F-FDG Patlak PET imaging procedure using a previously published population-averaged input function (PIF) scaled to IDIF values at 30–60 min post-injection (p.i.). The aim of the present study was to apply this method using the Vision Quadra PET/CT, including the use of a PIF to allow for shortened scan durations. Methods: Twelve patients with suspected lung malignancy were included and received a weight-based injection of 18F-FDG. Patients underwent a 65-min dynamic PET acquisition which were reconstructed using European Association of Nuclear Medicine Research Ltd. (EARL) standards 2 reconstruction settings. A volume of interest (VOI) was placed in the ascending aorta (AA) to obtain the IDIF. An external PIF was scaled to IDIF values at 30–60, 40–60, and 50–60 min p.i., respectively, and parametric 18F-FDG influx rate constant (Ki) images were generated using a t* of 30, 40 or 50 min, respectively. Herein, tumour lesions as well as healthy tissues, i.e. liver, muscle tissue, spleen and grey matter, were segmented. Results: Good agreement between the IDIF and corresponding PIF scaled to 30–60 min p.i. and 40–60 min p.i. was obtained with 7.38% deviation in Ki. Bland–Altman plots showed excellent agreement in Ki obtained using the PIF scaled to the IDIF at 30–60 min p.i. and at 40–60 min p.i. as all data points were within the limits of agreement (LOA) (− 0.004–0.002, bias: − 0.001); for the 50–60 min p.i. Ki, all except one data point fell in between the LOA (− 0.021–0.012, bias: − 0.005). Conclusions: Parametric whole body 18F-FDG Patlak Ki images can be generated non-invasively on a Vision Quadra PET/CT system. In addition, using a scaled PIF allows for a substantial (factor 2 to 3) reduction in scan time without substantial loss of accuracy (7.38% bias) and precision (image quality and noise interference)

EARL compliance and imaging optimisation on the Biograph Vision Quadra PET/CT using phantom and clinical data

PURPOSE: Current European Association of Nuclear Medicine (EANM) Research Ltd. (EARL) guidelines for the standardisation of PET imaging developed for conventional systems have not yet been adjusted for long axial field-of-view (LAFOV) systems. In order to use the LAFOV Siemens Biograph Vision Quadra PET/CT (Siemens Healthineers, Knoxville, TN, USA) in multicentre research and harmonised clinical use, compliance to EARL specifications for 18F-FDG tumour imaging was explored in the current study. Additional tests at various locations throughout the LAFOV and the use of shorter scan durations were included. Furthermore, clinical data were collected to further explore and validate the effects of reducing scan duration on semi-quantitative PET image biomarker accuracy and precision when using EARL-compliant reconstruction settings. METHODS: EARL compliance phantom measurements were performed using the NEMA image quality phantom both in the centre and at various locations throughout the LAFOV. PET data (maximum ring difference (MRD) = 85) were reconstructed using various reconstruction parameters and reprocessed to obtain images at shorter scan durations. Maximum, mean and peak activity concentration recovery coefficients (RC) were obtained for each sphere and compared to EARL standards specifications. Additionally, PET data (MRD = 85) of 10 oncological patients were acquired and reconstructed using various reconstruction settings and reprocessed from 10 min listmode acquisition into shorter scan durations. Per dataset, SUVs were derived from tumour lesions and healthy tissues. ANOVA repeated measures were performed to explore differences in lesion SUVmax and SUVpeak. Wilcoxon signed-rank tests were performed to evaluate differences in background SUVpeak and SUVmean between scan durations. The coefficient of variation (COV) was calculated to characterise noise. RESULTS: Phantom measurements showed EARL compliance for all positions throughout the LAFOV for all scan durations. Regarding patient data, EARL-compliant images showed no clinically meaningful significant differences in lesion SUVmax and SUVpeak or background SUVmean and SUVpeak between scan durations. Here, COV only varied slightly. CONCLUSION: Images obtained using the Vision Quadra PET/CT comply with EARL specifications. Scan duration and/or activity administration can be reduced up to a factor tenfold without the interference of increased noise

Extending the clinical capabilities of short- and long-lived positron-emitting radionuclides through high sensitivity PET/CT

This review describes the main benefits of using long axial field of view (LAFOV) PET in clinical applications. As LAFOV PET is the latest development in PET instrumentation, many studies are ongoing that explore the potentials of these systems, which are characterized by ultra-high sensitivity. This review not only provides an overview of the published clinical applications using LAFOV PET so far, but also provides insight in clinical applications that are currently under investigation. Apart from the straightforward reduction in acquisition times or administered amount of radiotracer, LAFOV PET also allows for other clinical applications that to date were mostly limited to research, e.g., dual tracer imaging, whole body dynamic PET imaging, omission of CT in serial PET acquisition for repeat imaging, and studying molecular interactions between organ systems. It is expected that this generation of PET systems will significantly advance the field of nuclear medicine and molecular imaging