Phantom-based image quality assessment of clinical 18F-FDG protocols in digital PET/CT and comparison to conventional PMT-based PET/CT.

BACKGROUND: We assessed and compared image quality obtained with clinical 18F-FDG whole-body oncologic PET protocols used in three different, state-of-the-art digital PET/CT and two conventional PMT-based PET/CT devices. Our goal was to evaluate an  improved trade-off between administered activity (patient dose exposure/signal-to-noise ratio) and acquisition time (patient comfort) while preserving diagnostic information achievable with the recently introduced digital detector technology compared to previous analogue PET technology. METHODS: We performed list-mode (LM) PET acquisitions using a NEMA/IEC NU2 phantom, with activity concentrations of 5 kBq/mL and 25 kBq/mL for the background (9.5 L) and sphere inserts, respectively. For each device, reconstructions were obtained varying the image statistics (10, 30, 60, 90, 120, 180, and 300 s from LM data) and the number of iterations (range 1 to 10) in addition to the employed local clinical protocol setup. We measured for each reconstructed dataset: the quantitative cross-calibration, the image noise on the uniform background assessed by the coefficient of variation (COV), and the recovery coefficients (RCs) evaluated in the hot spheres. Additionally, we compared the characteristic time-activity-product (TAP) that is the product of scan time per bed position × mass-activity administered (in min·MBq/kg) across datasets. RESULTS: Good system cross-calibration was obtained for all tested datasets with < 6% deviation from the expected value was observed. For all clinical protocol settings, image noise was compatible with clinical interpretation (COV < 15%). Digital PET showed an improved background signal-to-noise ratio as compared to conventional PMT-based PET. RCs were comparable between digital and PMT-based PET datasets. Compared to PMT-based PET, digital systems provided comparable image quality with lower TAP (from ~ 40% less and up to 70% less). CONCLUSIONS: This study compared the achievable clinical image quality in three state-of-the-art digital PET/CT devices (from different vendors) as well as in two conventional PMT-based PET. Reported results show that a comparable image quality is achievable with a TAP reduction of ~ 40% in digital PET. This could lead to a significant reduction of the administered mass-activity and/or scan time with direct benefits in terms of dose exposure and patient comfort.

Associations between Neuropsychiatric Symptoms and Cerebral Amyloid Deposition in Cognitively Impaired Elderly People.

BACKGROUND: Neuropsychiatric symptoms, also known as behavioral and psychological symptoms of dementia (BPSD), affect the majority of patients with dementia, and result in a greater cognitive and functional impairment. OBJECTIVE: To investigate associations between BPSD and amyloid cerebral deposition as measured by 18F-Florbetapir-PET quantitative uptake in elderly subjects with and without cognitive impairment. METHODS: Participants with cognitive impairment [mild cognitive impairment (MCI) or Alzheimer's disease (AD)] and healthy controls (HC) from the ADNI cohort (Alzheimer Disease Neuroimaging Initiative) who underwent an 18F-florbetapir PET scan between May 2010 and March 2014 were included. Clinical assessments included the Clinical Dementia Rating, the Mini-Mental State Examination (MMSE), and the Neuropsychiatric Inventory. Freesurfer software was used to extract PET counts based on T1-based structural ROI (frontal, cingulate, parietal, and temporal). Spearman's partial correlation scores between BPSD severity and regional amyloid uptake were calculated. RESULTS: Data for 657 participants [age = 72.6 (7.19); MMSE = 27.4 (2.67)] were analyzed, including 230 HC [age = 73.1 (6.02); MMSE = 29 (1.21)], 308 MCI [age = 71.5 (7.44); MMSE = 28.0 (1.75)], and 119 AD subjects [age = 74.7 (8.05); MMSE = 23.1 (2.08)]. Considering all diagnostic groups together, positive significant correlations were found between anxiety and 18F-florbetapir uptake in the frontal (r = 0.102; p = 0.009), cingulate (r = 0.083; p = 0.034), and global cerebral uptake (r = 0.099; p = 0.011); between irritability and frontal (r = 0.089; p = 0.023), cingulate (r = 0.085; p = 0.030), parietal (r = 0.087; p = 0.025), and global cerebral uptake (r = 0.093; p = 0.017); in the MCI subgroup, between anxiety and frontal (r = 0.126; p = 0.03) and global uptake (r = 0.14; p = 0.013); in the AD subgroup, between irritability and parietal uptake (r = 0.201; p = 0.03). CONCLUSION: Anxiety and irritability are associated with greater amyloid deposition in the neurodegenerative process leading to AD.

No association between striatal dopamine transporter binding and body mass index: a multi-center European study in healthy volunteers.

INTRODUCTION: Dopamine is one among several neurotransmitters that regulate food intake and overeating. Thus, it has been linked to the pathophysiology of obesity and high body mass index (BMI). Striatal dopamine D(2) receptor availability is lower in obesity and there are indications that striatal dopamine transporter (DAT) availability is also decreased. In this study, we tested whether BMI and striatal DAT availability are associated. METHODS: The study included 123 healthy individuals from a large European multi-center database. They had a BMI range of 18.2-41.1 kg/m(2) and were scanned using [(123)I]FP-CIT SPECT imaging. Scans were analyzed with both region-of-interest and voxel-based analysis to determine the binding potential for DAT availability in the caudate nucleus and putamen. A direct relation between BMI and DAT availability was assessed and groups with high and low BMI were compared for DAT availability. RESULTS: No association between BMI and striatal DAT availability was found. CONCLUSION: The lack of an association between BMI and striatal DAT availability suggests that the regulation of striatal synaptic dopamine levels by DAT plays no or a limited role in the pathophysiology of overweight and obesity.

Clinical applications of hybrid PET/MRI in neuroimaging.

PURPOSE: We tested the performance and clinical applicability of combined protocols for brain imaging studies acquired on a new whole-body hybrid PET/MR scanner. PATIENTS AND METHODS: Fifteen patients [6 male and 9 female patients; mean (SD) age, 51 (30) y; range, 6-89 y] were scanned on a Philips Ingenuity TF PET/MR. Standard imaging protocols of both modalities were combined, using a "head coil" and contrast-enhanced fully diagnostic MR protocols. Attenuation correction of the PET images was performed using tissue segmentation of the MR image and incorporation of attenuation templates measured for coils and table.The clinical indications evaluated are as follows: patients with cognitive disturbance of suspected neurodegenerative origin, presurgical evaluation of drug-refractory epilepsy, and brain tumor staging. For the first 2 indications, FDG PET imaging was performed, whereas for the last, fluoroethyltyrosine, an amino acid tracer, was used. RESULTS: In all cases (4 patients with neurodegenerative disease, 6 patients with epilepsy, and 5 patients with high-grade tumor), we obtained full diagnostic quality of both modalities and the total duration of the examination remained within a tolerable range (<2 hours). Twelve subjects had pathological findings: 11 of which were confirmed by clinical follow-up as true positive and 1 was confirmed as a false-positive result. For the 3 normal studies, the clinical follow-up confirmed the imaging findings as true-negative. CONCLUSIONS: Acquiring both PET and MR in a single session on a hybrid system minimized patient discomfort while maximizing clinical information and optimizing registration of both modalities. In addition, in comparison to PET/CT, the effective dose (related to CT) was reduced, and this is particularly beneficial in the pediatric population.

Peripheral nerves, tumors, and hybrid PET-MRI.

The study of peripheral nerves (PN) is a challenge because of the orientation, size, and also because of the fact that these pathologies are not well known. The diagnosis of PN damage was based exclusively on clinical examination and electrophysiologic testing until few years ago. MRI is the examination of choice for studying peripheral nerves; recently, magnetic resonance neurography has been added as a part of clinical routine. However, the analysis of PN after surgical treatment remains difficult. This clinical case of a sarcoma of the right brachial plexus illustrates how hybrid PET-MRI in postsurgical evaluation will clearly improve the exact delimitation of residual metabolically active tumor after surgery.

18F-FDG PET/CT and contrast-enhanced CT in a one-stop diagnostic procedure: a better strategy for management of patients suffering from retroperitoneal fibrosis?

PURPOSE: Effective management of patients affected by retroperitoneal fibrosis (RPF) is an important issue because of lack of relevant parameters to objectively assess the degree of inflammation. We evaluated added value of contrast-enhanced computed tomography (CE-CT) combined with fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) as a one-stop diagnostic procedure for the assessment and follow-up of patients with RPF. MATERIALS AND METHODS: (18)F-FDG PET and CE-CT findings were reviewed in 10 patients suffering from RPF. Maximum standard uptake values (on native and contrast-enhanced [ESUV(max)] CT) were calculated. Dimensions of periaortitis were measured on CT scans. Observed clinical changes between baseline PET scan (T0) and at 6 months follow-up (T6) were analyzed regarding differences of initial values for clinic and paraclinic parameters. RESULTS: Patients still suffering from pain 6 months after baseline PET scan had initially higher FDG uptake (ESUV(max): 5.7 ± 0.9 vs. 2.4 ± 0.9, P < 0.01). Unlike biologic and CT parameters, FDG uptake was the most relevant parameter to measure severity of inflammation (ESUV(max) threshold: 4.3; Se = Sp = 1.0). CE-CT exclusively allowed better delineation and more accurate assessment of FDG uptake of periaortitis and its extension to adjacent structures. CONCLUSIONS: Our results clearly show the usefulness of PET/CT for better evaluation and management of patients with fibroblast proliferation disease. Accurate determination of inflammation level is significantly improved when PET/CT and CE-CT are performed in the same study and used for better delineation of areas of residual inflammation.

Utility of postsurgical renal scintigraphy to predict one-year outcome of renal transplants in patients with delayed graft function.

OBJECTIVE: Delayed graft function is a frequent complication after kidney transplantation impacting aversely on graft survival. The aim of this study was to assess the prognostic value of quantitative scintigraphic parameters immediately after transplantation in this population. METHODS: One hundred patients with renal transplants suffering from delayed graft function were included in this study. All patients underwent Tc-mercaptoacetyltriglycine renal scintigraphy within 72 h of transplantation and were followed for 1 year. Various isotopic parameters were evaluated based on time-activity curves for angiographic and tubular phases. Threshold values for each parameter were derived from receiver operating characteristic curves to study their predictive values for transplant success at 1 year. RESULTS: Mean values of the Kirchner index, tubular function slope, graft/aorta perfusion ratio, or graft uptake/perfusion ratio were significantly higher in successfully grafted patients (P<0.05). The Kirchner index yielded the largest area under the receiver operating characteristic curves (0.75). The tubular function slope (odds ratio>1.4) was found to be an independent prognostic factor for 1-year renal graft failure. CONCLUSION: Our study confirms the prognostic value of vascular parameters in renal transplants, especially the Kirchner index whose negative predictive value was more than 90% for kidney transplantation 1-year success. In addition, isotopic parameters assessing the nephronic functional mass or the functional renal reserve seemed to be relevant prognostic tools with respect to 1-year outcomes. Therefore, the assessment of vascularization and renal function using an early Tc-mercaptoacetyltriglycine renal scintigraphy seems to be a powerful tool in establishing 1-year prognosis of renal allografts.