Brain Glucose Metabolism in Cerebral Amyloid Angiopathy: An FDG-PET Study.

BACKGROUND AND PURPOSE: The in vivo diagnosis of cerebral amyloid angiopathy (CAA) is currently based on the Boston criteria, which largely rely on hemorrhagic features on brain magnetic resonance imaging. Adding to these criteria 18F-fluoro-deoxy-D-glucose (FDG) positron emission tomography, a widely available imaging modality, might improve their accuracy. Here we tested the hypothesis that FDG uptake is reduced in posterior cortical areas, particularly the primary occipital cortex, which pathologically bear the brunt of vascular Aß deposition. METHODS: From a large memory clinic database, we retrospectively included all patients in whom both brain magnetic resonance imaging and FDG positron emission tomography had been obtained as part of routine clinical care and who fulfilled the Boston criteria for probable CAA. None had a history of symptomatic intracerebral hemorrhage. FDG data processing involved (1) spatial normalization to the Montreal Neurology Institute/International Consortium for Brain Mapping 152 space and (2) generation of standardized FDG uptake (relative standardized uptake value; relative to the pons). The relative standardized uptake value data obtained in 13 regions of interest sampling key cortical areas and the cerebellum were compared between the CAA and age-matched control groups using 2 separate healthy subject databases and image-processing pipelines. The presence of significant hypometabolism (2-tailed P<0.05) was assessed for the bilaterally averaged regions-of-interest relative standardized uptake values. RESULTS: Fourteen patients fulfilling the Boston criteria for probable CAA (≥2 exclusively lobar microbleeds) were identified. Significant hypometabolism (P range, 0.047 to <0.0001) consistently affected the posterior cortical areas, including the superior and inferior parietal, primary visual, lateral occipital, lateral temporal, precuneus, and posterior cingulate regions of interest. The anterior cortical areas were marginally or not significantly hypometabolic, and the cerebellum was spared. CONCLUSIONS: Supporting our hypothesis, significant glucose hypometabolism predominantly affected posterior cortical regions, including the visual cortex. These findings from a small sample may have diagnostic implications but require replication in larger prospective studies. In addition, whether they generalize to CAA-related symptomatic intracerebral hemorrhage warrants specific studies.

[18 F]FDG PET may differentiate cerebral amyloid angiopathy from Alzheimer's disease.

BACKGROUND: Cerebral amyloid angiopathy (CAA) is a frequent cause of both intracerebral hemorrhage (ICH) and cognitive impairment in the elderly. Diagnosis relies on the Boston criteria, which use magnetic resonance imaging markers including ≥2 exclusively lobar cerebral microbleeds (lCMBs). Although amyloid positron emission tomography (PET) may provide molecular diagnosis, its specificity relative to Alzheimer's disease (AD) is limited due to the prevalence of positive amyloid PET in cognitively normal elderly. Using early-phase 11 C-Pittsburgh compound B as surrogate for tissue perfusion, a significantly lower occipital/posterior cingulate (O/PC) tracer uptake ratio in probable CAA relative to AD was recently reported, consistent with histopathological lesion distribution. We tested whether this finding could be reproduced using [18 F]fluorodeoxyglucose (FDG)-PET, a widely available modality that correlates well with early-phase amyloid PET in both healthy subjects and AD. METHODS: From a large memory clinic database, we retrospectively included 14 patients with probable CAA (Boston criteria) and 21 patients with no lCMB fulfilling AD criteria including cerebrospinal fluid biomarkers. In all, [18 F]FDG-PET/computed tomography (CT) was available as part of routine care. No subject had a clinical history of ICH. Regional standardized [18 F]FDG uptake values normalized to the pons (standard uptake value ratio [SUVr]) were obtained, and the O/PC ratio was calculated. RESULTS: The SUVr O/PC ratio was significantly lower in CAA versus AD (1.02 ± 0.14 vs. 1.19 ± 0.18, respectively; p = 0.024). CONCLUSIONS: Despite the small sample, our findings are consistent with the previous early-phase amyloid PET study. Thus, [18 F]FDG-PET may help differentiate CAA from AD, particularly in cases of amyloid PET positivity. Larger prospective studies, including in CAA-related ICH, are however warranted.

Ventilation/perfusion SPECT/CT findings in different lung lesions associated with COVID-19: a case series.

PURPOSE: The aim of this series of cases is to show the aspects of ventilation/perfusion single-photon emission computed tomography combined with computed tomography (V/Q SPECT/CT) in patients hospitalized for COVID-19 pneumonia, with the worsening of respiratory symptoms raising the suspicion of a pulmonary embolism. Patients did not benefit from CT angiography for various reasons: a contraindication, unavailability of the CT angiography, or a low clinical probability for pulmonary embolism. METHODS: We retrospectively describe the results of the V/Q SPECT/CT of five patients hospitalized for COVID-19 pneumonia in the nuclear medicine departments of the Centre Cardiologique du Nord and of the Delafontaine hospital in Saint-Denis (Ile-de-France, France) between April 2, 2020, and April 10, 2020. These patients had persistent dyspnea or chest pain suggesting pulmonary embolism. RESULTS: The V/Q SPECT/CT allowed to diagnose a pulmonary embolism in one of these five patients. We also noted several characteristics of the perfusion and ventilation depending on the lung lesions on the CT scan. The areas affected by COVID-19 were most often responsible for ventilatory anomalies with a relatively preserved perfusion. In more advanced cases of pneumonia, with alveolar fillings, the perfusion was also reduced or absent in accordance with large ventilation defects. In addition, the healthy parenchyma appeared to benefit from an uptake in ventilation and perfusion. CONCLUSION: V/Q SPECT/CT can play a role in the management of patients hospitalized for COVID-19 for the diagnosis of embolic complications with meticulous hygienic precautions. The different characteristics of the ventilatory and perfusion anomalies related to COVID-19 pneumonia will be confirmed with the next cases. In addition, in this pandemic context and facing a significant infectious risk, the utility of ventilation will also have to be specified.

Brain 18FDG-PET pattern in patients with alcohol-related cognitive impairment.

PURPOSE: Brain positron emission tomography using 18F-fluorodeoxyglucose (18FDG-PET) provides a metabolic assessment of brain function that is useful for differential diagnosis among several neurodegenerative diseases manifested by cognitive impairment (CI). The purpose of the study is to describe the pattern of 18FDG-PET abnormalities in patients with CI related to alcohol use disorder. METHODS: Patients admitted to the addiction medicine department of a university hospital in Paris between January 2017 and October 2018 with a confirmed diagnosis of alcohol-related cognitive impairment (ARCI) or Wernicke encephalopathy (WE) were included. Brain 18FDG-PET uptake was measured after at least 1 month of monitored abstinence from alcohol. Standardized uptake values were obtained for 13 regions of interest (ROI) and normalized to the pons. Individual patients' ROI Z-scores were calculated from healthy sex- and age-matched controls provided by Cortex ID software. RESULTS: Twenty-five patients were included in the analysis (20 males and 5 females; mean age 57.6 years (45-76 years old)). The group consisted of 19 ARCI and 6 WE cases. The mean hypometabolism was most severe in the prefrontal medial cortex (PFM) (- 2.80 (± 1.30)), the prefrontal lateral cortex (- 2.20 (± 1.35)), and the anterior cingulate cortex (- 2.24 (± 1.19)). Hypometabolism (Z-score < - 2) was most frequent in the PFM (72.0% of the sample, N = 18). Other regions were also affected (with 5.32/13 hypometabolic ROIs on average (SD = 4.16, range 0-13)). The Z-scores in the 13 ROIs did not differ significantly between the ARCI and WE patients (p ≥ 0.05). CONCLUSIONS: Predominant prefrontal and cingulate cortex hypometabolism was the most frequent brain 18FDG-PET pattern in our sample of patients with ARCI and WE.

Feasibility of simultaneous dual isotope acquisition for myocardial perfusion imaging with a cadmium zinc telluride camera.

BACKGROUND: We studied the impact of technetium-99m (99mTc) in the thallium-201 (201Tl) energy window (70 keV) to determine if CZT cardiac cameras allow us to perform simultaneous dual-isotope acquisition for myocardial perfusion imaging. METHODS: We included 117 consecutive patients. We injected 0.7 MBq/kg of 201Tl at stress, performed the first scan (image T1), then injected at rest 2 MBq/kg of 99mTc-tetrofosmin and immediately acquired a second scan with reconstruction in the energy window of thallium (image T2). A corrected thallium image was created by the subtraction of 99mTc downscattered photons (image TS). We compared spectra, image quality, and semiquantitative scores on T1, T2, and TS images. RESULTS: Though T2 images were of worse quality, TS images were of equal quality compared to T1 images in most cases. Scores show an underestimation of abnormalities in 20% of patients on T2 images and in 10% on TS images. CONCLUSIONS: Despite the improved energy resolution of CZT cameras, downscatter of technetium in the 201Tl window leads to an underestimation of the pathological territory in 10% to 20% of cases. It does not allow us to use simultaneous dual-isotope acquisition in clinical practice without additional tools for scatter correction.

Prognostic value of one millisievert exercise myocardial perfusion imaging in patients without known coronary artery disease.

The aim of this study was to assess the prognostic value of normal ultra-low-dose exercise MPI with a CZT camera. METHODS: 1901 consecutive patients without known CAD referred for exercise MPI with 1.8 MBq/kg (0.05 mCi) of Tc99m sestamibi or tetrofosmin and a CZT camera were included prospectively. Patients with an abnormal scan requiring an additional resting image (230) or a submaximal exercise test (271) were excluded. The 1400 remaining patients were followed for 39 months. The primary end-point was cardiac events (cardiac death, nonfatal myocardial infarction, and revascularization). The secondary end-point was noncardiac death. RESULTS: The mean injected activity was 145 ± 37 MBq (3.9 ± 1 mCi), the mean acquisition duration was 10 ± 0.7 minutes, and the mean effective dose was 0.91 ± 0.13 mSv. 1288 patients (92%) achieved full follow-up. We observed 22 cardiac events and 16 noncardiac deaths. The annualized rates were equivalent to 0.55% for cardiac events and 0.37% for noncardiac mortality. CONCLUSIONS: Normal ultra-low-dose exercise MPI with a CZT camera has a high negative predictive value. The effective dose was less than 1 mSv, and the study thus allays concerns about radiation burden.

Long COVID: cognitive complaints (brain fog) and dysfunction of the cingulate cortex.

Many patients who have suffered from acute COVID infections have long-lasting symptoms affecting several organs including the brain. This long COVID status can include "brain fog" and cognitive deficits that can disturb activities of daily living and can delay complete recovery. Here, we report two cases of neurological long COVID with abnormal FDG PET findings marked by hypometabolic regions of the cingulate cortex.

Cognitive decline and brainstem hypometabolism in long COVID: A case series.

OBJECTIVE: To assess FDG cerebral PET in patients suffering from cognitive impairment linked to Long COVID. The COVID pandemic has affected dozens of millions of people around the world and has resulted in the deaths of more than 3 million people. Following the acute forms, it has been reported sometimes long forms of COVID, with involvements of several organs including the brain. Neurological complications can include cognitive disturbances (brain fog) that are very common and can seriously disturb the life of patients. METHODS: Fluorodeoxyglucose PETs were performed in 3 patients with cognitive decline following COVID infection. RESULTS: We report here 3 cases of brain fog with major hypometabolic areas of the pons revealed by the cerebral FDG PET. CONCLUSION: The dysfunction of the locus coeruleus in these patients could partly explain the cognitive disorders observed. Further studies involving larger cohorts of patients suffering from cognitive dysfunction will be needed to determine if the brainstem is frequently affected in these patients.

Clinical and phantom validation of a deep learning based denoising algorithm for F-18-FDG PET images from lower detection counting in comparison with the standard acquisition.

BACKGROUND: PET/CT image quality is directly influenced by the F-18-FDG injected activity. The higher the injected activity, the less noise in the reconstructed images but the more radioactive staff exposition. A new FDA cleared software has been introduced to obtain clinical PET images, acquired at 25% of the count statistics considering US practices. Our aim is to determine the limits of a deep learning based denoising algorithm (SubtlePET) applied to statistically reduced PET raw data from 3 different last generation PET scanners in comparison to the regular acquisition in phantom and patients, considering the European guidelines for radiotracer injection activities. Images of low and high contrasted (SBR = 2 and 5) spheres of the IEC phantom and high contrast (SBR = 5) of micro-spheres of Jaszczak phantom were acquired on 3 different PET devices. 110 patients with different pathologies were included. The data was acquired in list-mode and retrospectively reconstructed with the regular acquisition count statistic (PET100), 50% reduction in counts (PET50) and 66% reduction in counts (PET33). These count reduced images were post-processed with SubtlePET to obtain PET50 + SP and PET33 + SP images. Patient image quality was scored by 2 senior nuclear physicians. Peak-signal-to-Noise and Structural similarity metrics were computed to compare the low count images to regular acquisition (PET100). RESULTS: SubtlePET reliably denoised the images and maintained the SUVmax values in PET50 + SP. SubtlePET enhanced images (PET33 + SP) had slightly increased noise compared to PET100 and could lead to a potential loss of information in terms of lesion detectability. Regarding the patient datasets, the PET100 and PET50 + SP were qualitatively comparable. The SubtlePET algorithm was able to correctly recover the SUVmax values of the lesions and maintain a noise level equivalent to full-time images. CONCLUSION: Based on our results, SubtlePET is adapted in clinical practice for half-time or half-dose acquisitions based on European recommended injected dose of 3 MBq/kg without diagnostic confidence loss.

Images of COVID-19 Infection Cases in Asymptomatic or Paucisymptomatic Patients With Neoplastic Diseases on 18F-FDG PET/CT.

We describe the results of F-FDG PET/CT of 3 patients referred to our institution during the single day of Monday, March 23, 2020, for an initial assessment of cancer extension or for the therapeutic evaluation of chemotherapy of neoplastic pathology, with no obvious infectious or respiratory symptoms at the time of examination. A retrospective review of the recent clinical history of patients in association with the typical pulmonary images on CT scan suggested the diagnosis of COVID-19. The characteristic aspects of COVID-19 infection should be recognized on F-FDG PET/CT, even if patients are asymptomatic or minimally symptomatic.

The Use of FDG PET-CT Imaging for the Assessment of Early Antifungal Treatment Response in Disseminated Fusariosis.

Fusariosis is an opportunistic infection, caused by a filamentous fungus, found on plants and in soil. The treatment of disseminated pattern, seen in immunocompromised patients with severe neutropenia, is difficult because of antifungal therapy resistance. A 12-year-old girl, who was diagnosed with B-cell acute lymphoblastic leukemia, developed multiple widespread skin papules and subcutaneous nodules, at day 20 of consolidation therapy. Histological examination with cultures of skin tissue revealed Fusarium species. Treatment was started with intravenous liposomal amphotericin B and voriconazole. To assess treatment response, FDG PET/CT performed at baseline, at 2 and 4 months, showed a partial response.

Secondary Hyperparathyroidism With "Superscan-Like" Hypermetabolic FDG PET/CT Pattern.

A 26-year-old man with chronic terminal renal insufficiency under dialysis was referred in our institution for a checkup before kidney transplantation to ensure the absence of malignant neoplasm. The patient had a biological secondary hyperparathyroidism with highly elevated serum parathormon, and treatment with parathyroid surgery was planned before the kidney transplant. Whole-body FDG PET/CT showed no apparent malignant neoplasm, but increased metabolism of the 4 parathyroid gland and the other pitfalls of advanced secondary hyperparathyroidism on chronic renal insufficiency: pseudotumoral calcification in soft tissues, diffuse hypermetabolic bone dystrophy, and osteolytic lesion of pelvic and peripheral skeleton corresponding to brown tumors.

Low-dose thallium-201 protocol with a cadmium-zinc-telluride cardiac camera.

OBJECTIVES: Thallium-201 is efficient for myocardial perfusion imaging, but leads to relatively high radiation exposure in patients. The purpose of this study was to compare the efficiency of low-dose thallium-201 imaging with cadmium-zinc-telluride (CZT) cameras with regular-dose thallium-201 imaging with conventional cameras. METHODS: We prospectively studied 137 consecutive patients referred for stress myocardial perfusion imaging who had previously had a myocardial single-photon emission computed tomography with thallium-201. We injected at stress a low dose of thallium-201 (1.1 MBq/kg, 28 µCi/kg), performed a 5-7 min scan with a CZT camera (GE DNM 530c), and assessed redistribution imaging when the initial images were abnormal. We compared the CZT scan with the conventional dual-head tomographic camera scan taken previously with a regular dose of thallium-201. RESULTS: The average delay between both scans was 22 months. The stress dose was 88 ± 16 (2.38 ± 0.43 mCi) versus 125 ± 13 MBq (3.38 ± 0.34 mCi; a 30% reduction). The time for camera acquisition was 6 versus 13 min (a 54% reduction). The myocardial counts were increased two-fold with CZT (mean: 446 Kcounts). The quality of CZT images was better in 69% of the cases. There were 59 artifacts with conventional cameras and 29 artifacts with CZT (P<0.01). The diagnostic agreement was calculated in patients without clinical or angiographic changes between both scans (115 patients) and was high (97%). The effective dose at stress was less than 12 mSv. High myocardial counting allowed for further decrease in the injected activity, leading to an effective dose as low as 8 mSv. CONCLUSION: With reduced activities of thallium-201 and low effective doses, the CZT camera provides reliable, high-quality imaging.

First experience DaTSCAN imaging using cadmium-zinc-telluride gamma camera SPECT.

We report our first experience of brain DaTSCAN SPECT imaging using cadmium-zinc-telluride gamma camera (CZT-GC) in 2 cases: a 64-year-old patient suffering from essential tremor and a 73-year-old patient presenting with atypical bilateral extrapyramidal syndrome. In both cases, 2 different acquisitions were performed and compared, using a double-head Anger-GC, followed immediately by a second acquisition on CZT-GC. There were no significant visual differences between images generated by different GC. Our first result suggests that DaTSCAN SPECT is feasible on CZT-GC, allowing both injected dose and acquisition time reductions without compromising image quality. This experience needs to be evaluated in larger series.

Comparison of myocardial perfusion imaging using thallium-201 between a new cadmium-zinc-telluride cardiac camera and a conventional SPECT camera.

PURPOSE OF THE REPORT: Cadmium zinc telluride (CZT) solid-state detectors have been recently introduced in myocardial perfusion imaging. However, they had not been yet validated with thallium-201. This study compares the clinical performances of the CZT ultrafast camera GE DNM 530c with a conventional SPECT camera (CC) using thallium-201. MATERIALS AND METHODS: We prospectively studied with thallium-201 a total of 153 consecutive patients referred for myocardial perfusion imaging at exercise (3-4 mCi) then redistribution (with 1 mCi reinjection). Sequential acquisitions were performed first with a conventional dual-head tomographic Anger camera (CC) in 10 to 15 minutes and then with a CZT camera (CZT) in 5 minutes, in prone position. RESULTS: In all, 9 patients were excluded: 1 for mispositioning, 3 for camera failure, 3 for delayed acquisition after exercise, 1 for nonacceptance of redistribution, 1 for motion. Acquisition was more comfortable with CZT for all patients. Global counts rate was higher with CZT than with CC (3.6±0.57 KCts/s vs. 1.14±0.16). CZT has a 5-fold increased myocardial counts rate compared with CC (448±69 Kcts in 5 minutes vs. 209±40 Kcts in 12.5±1.8 minutes). Quality of CZT images was considered as better in 40%, equal in 56%, and worse in 4% of cases; we found less artifacts with CZT; diagnostic conclusions were the same in 140 of 144 cases (97%); discordances were 2 artifacts with CC and 2 small ischemia (less than 2 segments) missed by CZT. CONCLUSIONS: This new dedicated cardiac CZT camera allows with thallium-201 five minutes acquisitions with an increased image quality and a reliable diagnosis quality.

Brain SPECT thallium using cadmium zinc telluride: a first experience.

A 70-year-old man underwent a thallium-201 brain SPECT in the work-up and characterization of a frontotemporal mass. SPECT images were performed on cadmium zinc telluride system during only 5 minutes and after the injection of only 2 mCi. Images demonstrated high thallium uptake in frontotemporal areas considered as a potential malignant tumor. Surgical removal confirmed the diagnosis of malignant glioblastoma. The thallium SPECT fast acquisition imaging on cadmium zinc telluride systems is feasible with reduced injected dose. This method allows a significantly decrease of patient radiation exposure without compromising the image quality. This initial experience needs to be confirmed and optimized in larger clinical studies.