Purpose The main objective of this study was to evaluate the ability of a large field Cadmium Zinc Telluride (CZT) camera to estimate thyroid uptake (TU) on single photon emission computed tomography (SPECT) images with and without attenuation correction (Tomo-AC and Tomo-NoAC) compared with Planar acquisition in a series of 23 consecutive patients. The secondary objective was to determine radiation doses for the tracer administration and for the additional Computed Tomography (CT) scan. Methods Cross-calibration factors were determined using a thyroid phantom, for Planar, Tomo-AC and Tomo-NoAC images. Then Planar and SPECT/CT acquisitions centered on the thyroid were performed on 5 anthropomorphic phantoms with activity ranging from 0.4 to 10 MBq, and 23 patients after administration of 79.2 ± 3.7 MBq of [ 99m Tc]-pertechnetate. We estimated the absolute thyroid activity (AThA) for the anthropomorphic phantoms and the TU for the patients. Radiation dose was also determined using International Commission on Radiological Protection (ICRP) reports and VirtualDose TM CT software. Results Cross-calibration factors were 66.2 ± 4.9, 60.7 ± 0.7 and 26.5 ± 0.3 counts/(MBq s), respectively, for Planar, Tomo-AC and Tomo-NoAC images. Theoretical and estimated AThA for Planar, Tomo-AC and Tomo-NoAC images were statistically highly correlated ( r < 0.99; P < 10 –4 ) and the average of the relative percentage difference between theoretical and estimated AThA were (8.6 ± 17.8), (− 1.3 ± 5.2) and (12.8 ± 5.7) %, respectively. Comparisons between TU based on different pairs of images (Planar vs Tomo-AC, Planar vs Tomo-NoAC and Tomo-AC vs Tomo-NoAC) showed statistically significant correlation ( r = 0.972, 0.961 and 0.935, respectively; P < 10 –3 ). Effective and thyroid absorbed doses were, respectively (0.34 CT + 0.95 NM ) mSv, and (3.88 CT + 1.74 NM ) mGy. Conclusion AThA estimation using Planar and SPECT/CT acquisitions on a new generation of CZT large-field cameras is feasible. In addition, TU on SPECT/CT was as accurate as conventional planar acquisition, but the CT induced additional thyroid exposure. Trial registration Name of the registry: Thyroid Uptake Quantification on a New Generation of Gamma Camera (QUANTHYC). Trial number: NCT05049551. Registered September 20, 2021—Retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT05049551?cntry=MC&draw=2&rank=4 .

Purpose: We aimed to better understand the pathophysiology of SARS-CoV-2 pneumonia in non-critically ill hospitalized patients secondarily presenting with clinical deterioration and increase in oxygen requirement without any identified worsening factors. Methods: We consecutively enrolled patients without clinical or biological evidence for superinfection, without left ventricular dysfunction and for whom a pulmonary embolism was discarded by computed tomography (CT) pulmonary angiography. We investigated lung ventilation and perfusion (LVP) by LVP scintigraphy, and, 24 h later, left and right ventricular function by Tc-99m-labeled albumin-gated blood-pool scintigraphy with late (60 mn) tomographic albumin images on the lungs to evaluate lung albumin retention that could indicate microvascular injuries with secondary edema. Results: We included 20 patients with confirmed SARS-CoV-2 pneumonia. All had CT evidence of organizing pneumonia and normal left ventricular ejection fraction. No patient demonstrated preserved ventilation with perfusion defect (mismatch), which may discard a distal lung thrombosis. Patterns of ventilation and perfusion were heterogeneous in seven patients (35%) with healthy lung segments presenting a relative paradoxical hypoperfusion and hypoventilation compared with segments with organizing pneumonia presenting a relative enhancement in perfusion and preserved ventilation. Lung albumin retention in area of organizing pneumonia was observed in 12 patients (60%), indicating microvascular injuries, increase in vessel permeability, and secondary edema. Conclusion: In hospitalized non-critically ill patients without evidence of superinfection, pulmonary embolism, or cardiac dysfunction, various types of damage may contribute to clinical deterioration including microvascular injuries and secondary edema, inconsistencies in lung segments vascularization suggesting a dysregulation of the balance in perfusion between segments affected by COVID-19 and others. Summary Statement Microvascular injuries and dysregulation of the balance in perfusion between segments affected by COVID-19 and others are present in non-critically ill patients without other known aggravating factors. Key Results In non-critically ill patients without evidence of superinfection, pulmonary embolism, macroscopic distal thrombosis or cardiac dysfunction, various types of damage may contribute to clinical deterioration including 1/ microvascular injuries and secondary edema, 2/ inconsistencies in lung segments vascularization with hypervascularization of consolidated segments contrasting with hypoperfusion of not affected segments, suggesting a dysregulation of the balance in perfusion between segments affected by COVID-19 and others.

Purpose: We aimed to better understand the pathophysiology of SARS-CoV-2 pneumonia in non-critically ill hospitalized patients secondarily presenting with clinical deterioration and increase in oxygen requirement. Methods: We consecutively enrolled patients without clinical or biological evidence for superinfection, without left ventricular (LV) dysfunction and for whom a pulmonary embolism was discarded by computed tomography pulmonary angiography. We investigated lung ventilation and perfusion (LVP) by LVP scintigraphy, and, 24 hours later, left and right ventricular function by 99m Tc-labelled albumin gated-blood-pool scintigraphy with late (60 mn) tomographic albumin images on the lungs to evaluate lung albumin retention that could indicate microvascular injuries with secondary edema. Results: We included 13 patients with confirmed SARS-CoV-2 pneumonia. All had CT evidence of organizing pneumonia and normal LV ejection fraction.No patient demonstrated preserved ventilation with perfusion defect (mismatch), which may eliminate a distal lung thrombosis. Patterns of ventilation and perfusion were heterogeneous with sometimes healthy lung segments paradoxically hypoperfused and hypoventilated while both normal perfusion and ventilation were maintained in segments with organizing pneumonia (n=4). Lung albumin retention in area of organizing pneumonia was observed in 9 patients, indicating microvascular injuries, vessel permeability increase and secondary edema. Conclusion: In hospitalized non-critically ill patients without pulmonary embolism or LV dysfunction, various types of damage may contribute to clinical deterioration including microvascular injuries and secondary edema, broncho and vasoconstriction of area not involved by organizing pneumonia while no evidence was found for significant distal thrombosis detectable by LVP scintigraphy.

Purpose Physiological myocardial accumulation of FDG impairs the diagnosis of inflammatory/infectious or tumoral myocardial detection by FDG PET/CT. We prospectively evaluated the addition, 3 hours before imaging, of an intravenous 100-mL lipid emulsion infusion (Intralipid) to a high-fat, low-carbohydrate diet (HFLCD) for at least 2 meals followed by a fast of at least 6 to 12 hours in patients referred for the diagnosis of myocardial inflammation, endocarditis, cardiac or paracardiac masses, intracardiac device, or prosthetic valve infections. Methods Data of 58 patients consecutively included (28 Intralipid patients, 30 controls with HFLCD alone) were compared. FDG uptake in normal myocardium was scored from 0 (complete myocardial suppression) to 3 (high diffuse uptake). Myocardial maximal, peak, and mean SUV and the rate of interpretable images according to the clinical indication were measured. Results Compared with controls, Intralipid infusion significantly improved the rate of score 0 (89% vs 63%, P = 0.021), of interpretable images according to the clinical indication (100% vs 72%, P = 0.0047) and decreased all myocardial SUV values (eg, SUVmax median, 1.9 [interquartile range, 1.7–2.5] vs 3.1 [interquartile range, 2.3–4.1]; P < 0.001). Conclusions A lipid emulsion infusion in addition to HFLCD better suppresses cardiac glucose metabolism than HFLCD alone.

[18F]-2-Fluoro-2-deoxy-D-glucose PET/CT (FDG PET/CT) is a sensitive and quantitative technic for detecting inflammatory process. Glucose uptake is correlated with an increased anaerobic glycolysis seen in activated inflammatory cells such as monocytes, lymphocytes, and granulocytes. The aim of the study was to assess the inflammatory status at the presumed peak of the inflammatory phase in non-critically ill patients requiring admission for COVID-19. Patients admitted with COVID-19 were prospectively enrolled. FDG PET/CT was performed from day 6 to day 14 of the onset of symptoms. Depending on FDG PET/CT findings, patients’ profiles were classified as “inflammatory” or “low inflammatory.” FDG PET/CT data were compared with chest CT evolution and short-term clinical outcome. All inflammatory sites were reported to screen potential extra-pulmonary tropism. Thirteen patients were included. Maximum standardized uptake values ranged from 4.7 to 16.3 in lungs. All patients demonstrated increased mediastinal lymph nodes glucose uptake. Three patients (23%) presented mild nasopharyngeal, two patients (15%) bone marrow, and five patients (38%) splenic mild increase in glucose uptake. No patient had significant digestive focal or segmental glucose uptake. There was no significant physiological myocardial glucose uptake in all patients except one. There was no correlation between PET lung inflammatory status and chest CT evolution or short-term clinical outcome. Inflammatory process at the presumed peak of the inflammatory phase in COVID-19 patients is obvious in FDG PET/CT scans. Glucose uptake is heterogeneous and typically focused on lungs. NCT04441489. Registered 22 June 2020 (retrospectively registered).

Calculating attenuation correction for brain PET imaging rather than using CT presents opportunities for low radiation dose applications such as pediatric imaging and serial scans to monitor disease progression. Our goal is to evaluate the iterative time-of-flight based maximum-likelihood activity and attenuation correction factors estimation (MLACF) method for clinical FDG brain PET imaging. FDG PET/CT brain studies were performed in 57 patients using the Biograph mCT (Siemens) four-ring scanner. The time-of-flight PET sinograms were acquired using the standard clinical protocol consisting of a CT scan followed by 10 min of single-bed PET acquisition. Images were reconstructed using CT-based attenuation correction (CTAC) and used as a gold standard for comparison. Two methods were compared with respect to CTAC: a calculated brain attenuation correction (CBAC) and MLACF based PET reconstruction. Plane-by-plane scaling was performed for MLACF images in order to fix the variable axial scaling observed. The noise structure of the MLACF images was different compared to those obtained using CTAC and the reconstruction required a higher number of iterations to obtain comparable image quality. To analyze the pooled data, each dataset was registered to a standard template and standard regions of interest were extracted. An SUVr analysis of the brain regions of interest showed that CBAC and MLACF were each well correlated with CTAC SUVrs. A plane-by-plane error analysis indicated that there were local differences for both CBAC and MLACF images with respect to CTAC. Mean relative error in the standard regions of interest was less than 5% for both methods and the mean absolute relative errors for both methods were similar (3.4%  ±  3.1% for CBAC and 3.5%  ±  3.1% for MLACF). However, the MLACF method recovered activity adjoining the frontal sinus regions more accurately than CBAC method. The use of plane-by-plane scaling of MLACF images was found to be a crucial step in order to obtain improved activity estimates. Presence of local errors in both MLACF and CBAC based reconstructions would require the use of a normal database for clinical assessment. However, further work is required in order to assess the clinical advantage of MLACF over CBAC based method.

Purpose To compare the accuracy of a single 20-second deep-inspiration breath hold (DIBH) in fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) to that with conventional free-breathing (FB) whole-body PET/CT for the assessment, characterization, and quantification of lung lesions in terms of the blurring effect of respiratory motion. Materials and Methods Institutional review board approval was obtained, and the requirement to obtain informed consent was waived. A preclinical study was performed in a test population of 19 patients to evaluate the feasibility and consistency of DIBH techniques compared with phase-based respiratory gating (PBRG). One hundred fifteen patients with lung lesions were then prospectively included and assessed with FB PET/CT followed by 20-second DIBH PET/CT. Maximum standardized uptake value (SUVmax), peak standardized uptake value (SUVpeak), and number and size of nodules were reported for each acquisition and then compared with findings from histopathologic examination and/or clinical-radiologic follow-up. Statistical analysis was performed with the t test, χ2 test, Pearson correlation coefficient, and receiver operating characteristic analysis. Results In the test population, data obtained with DIBH PET and PBRG PET showed close correlation (r = 0.94, P < .001 for SUVmax and r = 0.98, P < .001 for SUVpeak). In the clinical population, both SUVmax and SUVpeak were significantly increased with DIBH compared with FB (5.60 ± 4.20 vs 3.11 ± 1.80 and 2.25 ± 1.75 vs 1.71 ± 0.96, respectively; P < .001). A significantly greater number of lung lesions was detected with DIBH PET/CT compared with FB PET/CT (P < .001), with the detection of 70 additional nodules and more accurate coregistration of 84. According to the area under the receiver operating characteristic curve for SUVpeak, DIBH demonstrated a higher level of accuracy than did FB (P = .039). Conclusion The DIBH PET/CT technique is feasible in routine clinical practice and is more sensitive for quantitative measurements and lesion localization. This technique reduces the blurring effect of respiratory motion, thus improving the diagnostic accuracy for lung nodules. © RSNA, 2017.

To assess the feasibility and benefit of integrating four-dimensional (4D) Positron Emission Tomography (PET) – computed tomography (CT) for liver stereotactic body radiation therapy (SBRT) planning.

554 Objectives Respiratory movements are an important concern impairing PET acquisition accuracy, leading to a decrease in SUVmax of the moving targets. Nevertheless, respiratory gating system is time-consuming and not always friendly to implement. We aimed to compare the respiratory gating (G) and 20s breath-hold (BH) inspiratory acquisitions on PET scans in terms of detectability and quantification. Methods We compared on a Siemens (mCT), the maximal uptake level using the SUVmax and the signal to noise (S/N) ratio of 28 lung target lesions in 22 consecutive patients (43 to 81 years). The SUV max were measured : - on the sum of three consecutive 20s BH PET acquisitions, coupled with a single breath 5s CT, - on PET images obtained by G-PET using an Anzai system (belt with pressure sensor) by computing the average value of each of the six phases for both parameters, - on a standard free-breathing whole body (SWB) acquisition. S/N was defined as the ratio of targets9 SUVmax and a spherical ROI of 2 cm3 drawn on the pulmonary artery. Results were expressed as mean ± sd. Results All patients sustained the 3 series of 20s apnea. For each BH-PET acquisition, reproducibility of SUVmax and S/N was high (respectively r = 0.97, p = 0.001 and r = 0.93, p = 0.001 between two consecutive acquisitions). 100% of lesions were detected on both BH and G-PET images. Lesion size (11 in the lower and 10 in the upper lobe) varied from 4 to more than 20 mm with movements in the three directions from 0 to 35 mm. Compared to SWB, SUVmax and S/N increased significantly on 20s BH-PET images (respectively 57 ± 68 %, p Conclusions Compared to respiratory gating, three consecutive apneas of 20s, increased similarly SUVmax and improved S/N ratio while reducing the examination time and improving the simplicity of patients9 workflow

Background We aimed to evaluate the additional information of 18 fluorodeoxyglucose (FDG) arterial uptake with respect to other conventional cardiovascular risk factors and arterial calcifications in patients with stable cancer. Methods and Results We compared the rate of cardiovascular events in 2 groups of patients with (n=45) and without (n=56) enhanced arterial 18FDG uptake, matched for the main clinical parameters. The extent and intensity of 18FDG uptake were quantified. A calcification index was also determined. About one third of the selected patients had a history of cardiovascular events and thus could be defined as “vulnerable patients.” Old cardiovascular events (>6 months before or after positron emission tomography [PET]) and recent cardiovascular events (<6 months before or after PET) were significantly more frequent in the high-FDG uptake group than in the low-FDG uptake group (48% vs 15%, respectively [ P =.0006], and 30% vs 1.8%, respectively [ P =.0002]). The extent of 18FDG arterial uptake was the unique factor significantly related to the occurrence of a recent event by either logistic regression or discriminant analysis ( P =.004 for all). Conversely, calcium index was the single factor related to old events ( P =.004 and P =.002, respectively). Conclusions Extensive arterial 18FDG uptake might be an indicator of an evolving atherosclerotic process and should be mentioned in PET/computed tomography reports.