Positron Emission Tomography Acquisition Research Articles

Investigation of intra-fractionated range guided adaptive proton therapy (RGAPT): II. Range-shift compensated on-line treatment adaptation and verification

We previously proposed range-guided adaptive proton therapy (RGAPT) that uses mid-range treatment beams as probing beams and intra-fractionated range measurements for online adaptation. In this work, we demonstrated experimental verification and reported the dosimetric accuracy for RGAPT. A STEEV phantom was used for the experiments, and a 3 × 3 × 3 cm3 cube inside the phantom was assigned to be the treatment target. We simulated three online range shift scenarios: reference, overshoot, and undershoot, by placing upstream Lucite sheets, 4, 0, and 8 that corresponded to changes of 0, 6.8, and −6.8 mm, respectively, in water-equivalent path length. The reference treatment plan was to deliver single-field uniform target doses in pencil beam scanning mode and generated on the Eclipse treatment planning system. Different numbers of mid-range layers, including single, three, and five layers, were selected as probing beams to evaluate beam range (BR) measurement accuracy in positron emission tomography (PET). Online plans were modified to adapt to BR shifts and compensate for probing beam doses. In contrast, non-adaptive plans were also delivered and compared to adaptive plans by film measurements. The mid-range probing beams of three (5.55MU) and five layers (8.71MU) yielded accurate range shift measurements in 60 s of PET acquisition with uncertainty of 0.5 mm while the single-layer probing (1.65MU) was not sufficient for measurements. The adaptive plans achieved an average gamma (2%/2 mm) passing rate of 95%. In contrast, the non-adaptive plans only had an average passing rate of 69%. RGAPT planning and delivery are feasible and verified by the experiments. The probing beam delivery, range measurements, and adaptive planning and delivery added a small increase in treatment delivery workflow time but resulted in substantial dose improvement. The three-layer mid-range probing was most suitable considering the balance of high range measurement accuracy and the low number of probing beam layers.

Diagnosis of giant cell arteritis by 18F-FDG PET/CT in patients on glucocorticoid therapy: importance of delayed imaging.

The aim of this study is to analyse the diagnostic value of positron emission tomography (PET) in patients with giant cell arteritis (GCA) despite glucocorticoid (GC) therapy before PET acquisition. Consecutive patients with strongly suspected GCA according to 2022 EULAR/ACR criteria were included. The physician diagnosis of GCA after 6 months of follow-up was the gold standard. PET was performed at baseline and 6 months later. In patients with negative results at 60 min, delayed imaging was performed at 180 min. Twenty-six patients were included with a median (IQR) age of 70.5 (57-88) years. Baseline PET was positive in all but one: 18 patients at 60 min and 7 patients after delayed imaging at 180 min. The median (IQR) GC dose at the time of baseline PET was 45 mg/d (26.2-45) of prednisone equivalent with a median exposure of 14 days (7-76.2). At 6 months of follow-up, PET was performed in 22 patients, with positive results in 16. Delayed imaging was performed in 6 patients due to negative PET at 60 min, with positive results in all cases, despite treatment with GC and/or biological therapy. In patients on GC therapy, delayed imaging protocols applying procedural recommendations for vascular quantification could improve diagnostic accuracy. Therefore, we suggest performing imaging only at 180 min in patients who have been on GCs for more than 3 days as well as in those with highly suspected GCA but negative findings in baseline PET at 60 min.

Florbetaben amyloid PET acquisition time: Influence on Centiloids and interpretation.

Amyloid positron emission tomography (PET) acquisition timing impacts quantification. In florbetaben (FBB) PET scans of 245 adults with and without cognitive impairment, we investigated the impact of post-injection acquisition time on Centiloids (CLs) across five reference regions. CL equations for FBB were derived using standard methods, using FBB data collected between 90 and 110 min with paired Pittsburgh compound B data. Linear mixed models and t-tests evaluated the impact of acquisition time on CL increases. CL values increased significantly over the scan using the whole cerebellum, cerebellar gray matter, and brainstem as reference regions, particularly in amyloid-positive individuals. In contrast, CLs based on white matter-containing reference regions decreased across the scan. The quantification of CLs in FBB PET imaging is influenced by both the overall scan acquisition time and the choice of reference region. Standardized acquisition protocols or the application of acquisition time-specific CL equations should be implemented in clinical protocols. Acquisition timing affects florbetaben positron emission tomography (PET) scan quantification, especially in amyloid-positive participants. The impact of acquisition timing on quantification varies across common reference regions. Consistent acquisitions and/or appropriate post-injection adjustments are needed to ensure comparability of PET data.

Simultaneous 18-FDG PET and MR imaging in lower extremity arterial disease.

Simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) is a novel hybrid imaging method integrating the advances of morphological tissue characterization of MRI with the pathophysiological insights of PET applications. This study evaluated the use of simultaneous 18-FDG PET/MR imaging for characterizing atherosclerotic lesions in lower extremity arterial disease (LEAD). Eight patients with symptomatic stenoses of the superficial femoral artery (SFA) under simultaneous acquisition of 18-FDG PET and contrast-enhanced MRI using an integrated whole-body PET/MRI scanner. Invasive plaque characterization of the SFA was performed by intravascular imaging using optical coherence tomography. Histological analysis of plaque specimens was performed after directional atherectomy. MRI showed contrast enhancement at the site of arterial stenosis, as assessed on T2-w and T1-w images, compared to a control area of the contralateral SFA (0.38 ± 0.15 cm vs. 0.23 ± 0.11 cm; 1.77 ± 0.19 vs. 1.57 ± 0.15; p-value <0.05). On PET imaging, uptake of 18F-FDG (target-to-background ratio TBR > 1) at the level of symptomatic stenosis was observed in all but one patient. Contrast medium-induced MR signal enhancement was detected in all plaques, whereas FDG uptake in PET imaging was increased in lesions with active fibroatheroma and reduced in fibrocalcified lesions. In this multimodal imaging study, we report the feasibility and challenges of simultaneous PET/MR imaging of LEAD, which might offer new perspectives for risk estimation.

Rationale and design of the RAPID-WATER-FLOW trial: Radiolabeled perfusion to identify coronary artery disease using water to evaluate responses of myocardial FLOW

ObjectivesThe objective of this study was to determine the diagnostic performance of 15O-water positron emission tomography (PET) myocardial perfusion imaging to detect coronary artery disease (CAD) using the truth-standard of invasive coronary angiography (ICA) with fractional flow reserve (FFR) or instantaneous wave-Free Ratio (iFR) or coronary computed tomography angiogram (CCTA). Background15O-water has a very high first-pass extraction that allows accurate quantification of myocardial blood flow and detection of flow-limiting CAD. However, the need for an on-site cyclotron and lack of automated production at the point of care and relatively complex image analysis protocol has limited its clinical use to date. MethodsThe RAPID WATER FLOW study is an open-label, multicenter, prospective investigation of the accuracy of 15O-water PET to detect obstructive angiographic and physiologically significant stenosis in patients with suspected CAD. The study will include the use of an automated system for producing, dosing, and injecting 15O-water and enrolling approximately 215 individuals with suspected CAD at approximately 10 study sites in North America and Europe. The primary endpoint of the study is the diagnostic sensitivity and specificity of the 15O-water PET study using the truth-standard of ICA with FFR or iFR to determine flow-limiting stenosis, or CCTA to rule out CAD and incorporating a quantitative analytic platform developed for the 15O-water PET acquisitions. Sensitivity and specificity are to be considered positive if the lower bound of the 95% confidence interval is superior to the threshold of 60% for both, consistent with prior registration studies.Subgroup analyses include assessments of diagnostic sensitivity, specificity, and accuracy in female, obese, and diabetic individuals, as well as in those with multivessel disease. All enrolled individuals will be followed for adverse and serious adverse events for up to 32 hours after the index PET scan.The study will have >90% power (one-sided test, α = 0.025) to test the hypothesis that sensitivity and specificity of 15O-water PET are both >60%. ConclusionsThe RAPID WATER FLOW study is a prospective, multicenter study to determine the diagnostic sensitivity and specificity of 15O-water PET as compared to ICA with FFR/iFR or CCTA. This study will introduce several novel aspects to imaging registration studies, including a more relevant truth standard incorporating invasive physiologic indexes, coronary CTA to qualify normal individuals for eligibility, and a more quantitative approach to image analysis than has been done in prior pivotal studies. Clinical trial registration informationClinical-Trials.gov (#NCT05134012).

Evaluation of Hematopoiesis and Disease Status in Patients with Hematologic Malignancies Using Whole-Body Bone Marrow Imaging with 18 F-FLT PET/MRI

Introduction Bone marrow examination is primarily focused on a limited region of the ilium, thereby inadequately assessing systemic hematopoiesis or residual tumor cells after therapy. Magnetic resonance imaging (MRI) of the spine can examine the fat marrow, but does not provide a direct assessment of hematopoietic cells. The use of the radiopharmaceutical 3‘-deoxy-3‘- 18F-fluorothymidine ( 18F-FLT) positron emission tomography (PET), which measures nucleic acid synthesis, can provide a quantifiable means of assessing hematopoietic cell proliferation. The combination of whole-body MRI and 18F-FLT PET may provide a more accurate assessment of whole-body bone marrow hematopoiesis in hematologic malignancies. Methods A prospective, open-label, exploratory study (UMIN000041491) was conducted to evaluate hematopoiesis using 18F-FLT PET/MRI imaging in patients planned for allogeneic hematopoietic stem cell transplantation. Subjects were patients over 20 years of age with hematologic malignancies who underwent 18F-FLT PET/MRI imaging before transplantation and at 50 and 180 days after transplantation. After an intravenous injection of 185 MBq 18F-FLT, patients were transferred to a simultaneous 3.0 T PET/MR scanner (Signa PET/MR; GE Healthcare, Waukesha, WI). The PET acquisition was performed in 3D mode with a 5.5 min/bed position (89 slices/bed) and a 24-slice overlap in 5 to 6 beds. The percentage of fat marrow was determined using MRI proton density fat fraction (PDFF) with a 1 cm 2 region of interest at 26 sites: cervical spine (C2-C7), thoracic spine (Th1-Th12), lumbar spine (L1-L5), and superior posterior iliac spine (two sites on each side). Similarly, the standardized uptake value (SUV) of 18F-FLT was measured. Results Thirteen patients with hematologic malignancies (8 with acute myeloid leukemia, 2 with acute lymphoblastic leukemia, and 3 with malignant lymphoma) were evaluated between August 2020 and April 2023. The median age of the patients was 46 years (range: 23 ~ 65). Seven patients underwent cord blood transplantation, while the remainder received peripheral blood stem cell transplantation. Prior to transplantation, all 13 patients underwent 18F-FLT PET/MRI scans. After transplantation, due to treatment-related death or worsening of the primary disease, 11 patients underwent scans on day 50, while 8 patients underwent scans on day 180, resulting in a total of 32 evaluable scans. In the 28 cases in hematologic remission at imaging, mean PDFF values were higher in the iliac (63.3% ± standard deviation 13.9) and lumbar (60.4% ± 14.9) than in the thoracic (47.2% ± 17.1) and cervical (37.5% ± 14.8) spines. Conversely, mean 18F-FLT SUV was higher in the thoracic (6.98 ± 2.31) and cervical (6.82 ± 2.03) than in the lumbar (5.06 ± 2.39) and iliac (3.95 ± 1.88) spine. This site-specific disparity in PDFF and 18F-FLT SUV was consistent both before and after transplantation. In all 32 cases, the median correlation coefficient between PDFF and 18F-FLT SUV was -0.60 (range: -0.92 ~ 0.17, Pearson's cumulative correlation coefficient), and 25 cases (78.1%) had a negative correlation coefficient below -0.4. Comparing the 12 cases with residual disease (4 cases with hematologic non-remission and 8 cases with hematologic remission but abnormal G-banding or quantitative polymerase chain reaction) with the 20 cases in complete remission, the correlation between PDFF and 18F-FLT SUV was significantly weaker in the residual disease group (-0.37 vs. -0.75, p&amp;lt;0.001, Mann-Whitney U test). When the correlation coefficient threshold was set at -0.57, the ROC curve for determining residual disease had an AUC of 0.86, a sensitivity of 83.3%, and a specificity of 85.0%. Discussion It is important to understand that the fat marrow and hematopoiesis degree in the iliac bone differs from that in the thoracic and cervical spine throughout the transplantation process, thereby influencing the disease status evaluation in hematological malignancies. The correlation between PDFF and 18F-FLT SUV, which is strong in cases of remission, weakens in cases of residual disease, even at the level of minimal residual disease. This discrepancy may reflect aberrant tumorigenic cell proliferation that differs from the norm. Thus, 18F-FLT PET/MRI was useful in understanding the hematopoietic and disease state of the systemic bone marrow in patients with hematologic malignancies.

Abstract 13712: Imaging Short-Chain Fatty Acid Metabolism and Transport in the Failing Heart by PET

Introduction: Heart failure compromises the transport and oxidation of long chain fatty acids. Cardiomyocytes can compensate by using short-chain fatty acids (SCFA) which rely on other transport mechanisms. Based on this principle, we used 2-[ 18 F]fluoropropionic acid ([ 18 F]FPA), a radiolabeled SCFA analog, to assess these metabolic changes and image them by positron emission tomography (PET) in a doxorubicin-induced mouse model of cardiotoxicity. Hypothesis: We hypothesize that the increased demand for SCFA by the failing heart promotes cardiac accumulation of [ 18 F]FPA which can be imaged by PET. Methods: [ 18 F]FPA was injected intravenously into male C57BL/6J mice 10 weeks following intraperitoneal injections of 8 x 3 mg/kg doxorubicin (DOX). Dynamic PET acquisitions were performed from 60-120 min post injection of 9.25-11 MBq [ 18 F]FPA. These images were acquired in the presence or absence of 5 mg/kg AZD3965, an inhibitor of monocarboxylate transporters. Heart uptake of [ 18 F]FPA was determined by image-based quantitation and confirmed by a biodistribution study. Mechanistic [ 18 F]FPA uptake studies were also conducted in primary human cardiomyocyte (HCM) cultures. Results: Mice experiencing DOX-induced cardiotoxicity exhibited statistically significant increases in cardiac [ 18 F]FPA. AZD3965 did not significantly alter cardiac uptake but reduced uptake in all other tissues except the kidneys, the route of excretion. Additionally, [ 18 F]FPA uptake is lost in HCM for which mitochondrial acyl-CoA synthetase (ACSS) 1, but not cytosolic ACSS2, is inhibited. Conclusions: Our findings present both mechanistic and translational applications for [ 18 F]FPA. AZD3965 effectively reduced [ 18 F]FPA uptake in other tissues except for the heart and can therefore be co-administered to enhance the heart-to-background ratio. Altogether, our results indicate that [ 18 F]FPA may enter cardiac tissues by diffusion and become metabolically trapped in mitochondria.

Reconstruction of multi-animal PET acquisitions with anisotropically variant PSF

Among other factors such as random, attenuation and scatter corrections, uniform spatial resolution is key to performing accurate quantitative studies in Positron emission tomography (PET). Particularly in preclinical PET studies involving simultaneous acquisition of multiple animals, the degradation of image resolution due to the depth of interaction (DOI) effect far from the center of the Field of View (FOV) becomes a significant concern. In this work, we incorporated a spatially-variant resolution model into a real time iterative reconstruction code to obtain accurate images of multi-animal acquisition. We estimated the spatially variant point spread function (SV-PSF) across the FOV using measurements and Monte Carlo (MC) simulations. The SV-PSF obtained was implemented in a GPU-based Ordered subset expectation maximization (OSEM) reconstruction code, which includes scatter, attenuation and random corrections. The method was evaluated with acquisitions from two preclinical PET/CT scanners of the SEDECAL Argus family: a Derenzo phantom placed 2 cm off center in the 4R-SuperArgus, and a multi-animal study with 4 mice in the 6R-SuperArgus. The SV-PSF reconstructions showed uniform spatial resolution without significant increase in reconstruction time, with superior image quality compared to the uniform PSF model.

Semi-Supervised Standard-Dose PET Image Generation via Region-Adaptive Normalization and Structural Consistency Constraint.

Positron Emission Tomography (PET) is an important nuclear medical imaging technique, and has been widely used in clinical applications, e.g., tumor detection and brain disease diagnosis. As PET imaging could put patients at risk of radiation, the acquisition of high-quality PET images with standard-dose tracers should be cautious. However, if dose is reduced in PET acquisition, the imaging quality could become worse and thus may not meet clinical requirement. To safely reduce the tracer dose and also maintain high quality of PET imaging, we propose a novel and effective approach to estimate high-quality Standard-dose PET (SPET) images from Low-dose PET (LPET) images. Specifically, to fully utilize both the rare paired and the abundant unpaired LPET and SPET images, we propose a semi-supervised framework for network training. Meanwhile, based on this framework, we further design a Region-adaptive Normalization (RN) and a structural consistency constraint to track the task-specific challenges. RN performs region-specific normalization in different regions of each PET image to suppress negative impact of large intensity variation across different regions, while the structural consistency constraint maintains structural details during the generation of SPET images from LPET images. Experiments on real human chest-abdomen PET images demonstrate that our proposed approach achieves state-of-the-art performance quantitatively and qualitatively.

Fast and low-dose medical imaging generation empowered by hybrid deep-learning and iterative reconstruction

Fast and low-dose reconstructions of medical images are highly desired in clinical routines. We propose a hybrid deep-learning and iterative reconstruction (hybrid DL-IR) framework and apply it for fast magnetic resonance imaging (MRI), fast positron emission tomography (PET), and low-dose computed tomography (CT) image generation tasks. First, in a retrospective MRI study (6,066 cases), we demonstrate its capability of handling 3- to 10-fold under-sampled MR data, enabling organ-level coverage with only 10- to 100-s scan time; second, a low-dose CT study (142 cases) shows that our framework can successfully alleviate the noise and streak artifacts in scans performed with only 10% radiation dose (0.61 mGy); and last, a fast whole-body PET study (131 cases) allows us to faithfully reconstruct tumor-induced lesions, including small ones (<4mm), from 2- to 4-fold-accelerated PET acquisition (30-60 s/bp). This study offers a promising avenue for accurate and high-quality image reconstruction with broad clinical value.

Spatiotemporal Learning of Dynamic Positron Emission Tomography Data Improves Diagnostic Accuracy in Breast Cancer

Positron emission tomography (PET) is a noninvasive imaging technology able to assess the metabolic or functional state of healthy and/or pathological tissues. In clinical practice, PET data are usually acquired statically and normalized for the evaluation of the standardized uptake value (SUV). In contrast, dynamic PET acquisitions provide information about radiotracer delivery to tissue, its interaction with the target and its physiological washout. The shape of the time activity curves (TACs) embeds tissue-specific biochemical properties. Conventionally, TACs are employed along with information about blood plasma activity concentration, i.e., the arterial input function, and tracer-specific compartmental models to obtain a full quantitative analysis of PET data. This method’s primary disadvantage is the requirement for invasive arterial blood sample collection throughout the whole PET scan. In this study, we employ a variety of deep learning models to illustrate the diagnostic potential of dynamic PET acquisitions of varying lengths for discriminating breast cancer lesions in the absence of arterial blood sampling compared to static PET only. Our findings demonstrate that the use of TACs, even in the absence of arterial blood sampling and even when using only a share of all timeframes available, outperforms the discriminative ability of conventional SUV analysis.

PET/MRI for evaluation of patients with pancreatic cancer.

Pancreatic cancers are the third leading cause of cancer-related death in the USA and outcomes remain poor despite improvements in imaging and treatment paradigms. Currently, computed tomography (CT) and magnetic resonance imaging (MRI) are frequently utilized for staging and restaging of these malignancies, but positron emission tomography (PET)/CT can play a role in troubleshooting and improve whole-body staging. PET/MRI is a novel imaging modality that allows for simultaneous acquisition of PET and MRI images, leading to improved image quality and potential increased sensitivity. Early studies suggest that PET/MRI may play a larger role in pancreatic cancer imaging in future. This manuscript will briefly discuss current imaging approaches to pancreatic cancer and outline existing evidence and published data supporting the use of PET/MRI for pancreatic cancers.

Design of a generic method for single dual-tracer PET imaging acquisition in clinical routine

Using different tracers in positron emission tomography (PET) imaging can bring complementary information on tumor heterogeneities. Ideally, PET images of different tracers should be acquired simultaneously to avoid the bias induced by movement and physiological changes between sequential acquisitions. Previous studies have demonstrated the feasibility of recovering separated PET signals or parameters of two or more tracers injected (quasi-)simultaneously in a single acquisition. In this study, a generic framework in the context of dual-tracer PET acquisition is proposed where no strong kinetic assumptions nor specific tuning of parameters are required. The performances of the framework were assessed through simulations involving the combination of [18F]FCH and [18F]FDG injections, two protocols (90 and 60 min acquisition durations) and various activity ratios between the two injections. Preclinical experiments with the same radiotracers were also conducted. Results demonstrate the ability of the method both to extract separated arterial input functions (AIF) from noisy image-derived input function and to separate the dynamic signals and further estimate kinetic parameters. The compromise between bias and variance associated with the estimation of net influx rate K i shows that it is preferable to use the second injected radiotracer with twice the activity of the first for both 90 min [18F]FCH+[18F]FDG and 60 min [18F]FDG+[18F]FCH protocols. In these optimal settings, the weighted mean-squared-error of the estimated AIF was always less than 7%. The K i bias was similar to the one of single-tracer acquisitions; below 5%. Compared to single-tracer results, the variance of K i was twice more for 90 min dual-tracer scenario and four times more for the 60 min scenario. The generic design of the method makes it easy to use for other pairs of radiotracers and even for more than two tracers. The absence of strong kinetic assumptions and tuning parameters makes it suitable for a possible use in clinical routine.

A simplified method to correct saturation of arterial input function for cardiac magnetic resonance first-pass perfusion imaging: validation with simultaneously acquired PET

BackgroundFirst-pass perfusion imaging in magnetic resonance imaging (MRI) is an established method to measure myocardial blood flow (MBF). An obstacle for accurate quantification of MBF is the saturation of blood pool signal intensity used for arterial input function (AIF). The objective of this project was to validate a new simplified method for AIF estimation obtained from single-bolus and single sequence perfusion measurements. The reference MBF was measured simultaneously on 13N-ammonia positron emission tomography (PET). MethodsSixteen patients with clinically confirmed myocardial ischemia were imaged in a clinical whole-body PET-MRI system. PET perfusion imaging was performed in a 10-min acquisition after the injection of 10 mCi of 13N-ammonia. The MRI perfusion acquisition started simultaneously with the start of the PET acquisition after the injection of a 0.075 mmol/kg gadolinium contrast agent. Cardiac stress imaging was initiated after the administration of regadenoson 20 s prior to PET-MRI scanning. The saturation part of the MRI AIF data was modeled as a gamma variate curve, which was then estimated for a true AIF by minimizing a cost function according to various boundary conditions. A standard AHA 16-segment model was used for comparative analysis of absolute MBF from PET and MRI. ResultsOverall, there were 256 segments in 16 patients, mean resting perfusion for PET was 1.06 ± 0.34 ml/min/g and 1.04 ± 0.30 ml/min/g for MRI (P = 0.05), whereas mean stress perfusion for PET was 2.00 ± 0.74 ml/min/g and 2.12 ± 0.76 ml/min/g for MRI (P < 0.01). Linear regression analysis in MBF revealed strong correlation (r = 0.91, slope = 0.96, P < 0.001) between PET and MRI. Myocardial perfusion reserve, calculated from the ratio of stress MBF over resting MBF, also showed a strong correlation between MRI and PET measurements (r = 0.82, slope = 0.81, P < 0.001). ConclusionThe results demonstrated the feasibility of the simplified AIF estimation method for the accurate quantification of MBF by MRI with single sequence and single contrast injection. The MRI MBF correlated strongly with PET MBF obtained simultaneously. This post-processing technique will allow easy transformation of clinical perfusion imaging data into quantitative information.

Comparison of dual-energy CT with positron emission tomography for lung perfusion imaging in patients with non-small cell lung cancer

Objective. Functional lung avoidance (FLA) radiotherapy treatment aims to spare lung regions identified as functional from imaging. Perfusion contributes to lung function and can be measured from the determination of pulmonary blood volume (PBV). An advantageous alternative to the current determination of PBV from positron emission tomography (PET) may be from dual energy CT (DECT), due to shorter examination time and widespread availability. This study aims to determine the correlation between PBV determined from DECT and PET in the context of FLA radiotherapy. Approach. DECT and PET acquisitions at baseline of patients enrolled in the HI-FIVE clinical trial (ID: NCT03569072) were reviewed. Determination of PBV from PET imaging (), from DECT imaging generated from a commercial software (Syngo.via, Siemens Healthineers, Forchheim, Germany) with its lowest () and highest () smoothing level parameter value (R), and from a two-material decomposition (TMD) method () with variable median filter kernel size (L) were compared. Deformable image registration between DECT images and the CT component of the PET/CT was applied to PBV maps before resampling to the PET resolution. The Spearman correlation coefficient (r s) between PBV determinations was calculated voxel-wise in lung subvolumes. Main results. Of this cohort of 19 patients, 17 had a DECT acquisition at baseline. PBV maps determined from the commercial software and the TMD method were very strongly correlated [r s( ) = 0.94 ± 0.01 and r s( ) = 0.94 ± 0.02]. was strongly correlated with [r s( ) = 0.67 ± 0.11]. Perfusion patterns differed along the posterior-anterior direction [r s( ) = 0.77 ± 0.13/0.57 ± 0.16 in the anterior/posterior region]. Significance. A strong correlation between DECT and PET determination of PBV was observed. Streak and smoothing effects in DECT and gravitational artefacts and misregistration in PET reduced the correlation posteriorly.

The amyloid imaging for the prevention of Alzheimer's disease consortium: A European collaboration with global impact.

Amyloid-β (Aβ) accumulation is considered the earliest pathological change in Alzheimer's disease (AD). The Amyloid Imaging to Prevent Alzheimer's Disease (AMYPAD) consortium is a collaborative European framework across European Federation of Pharmaceutical Industries Associations (EFPIA), academic, and 'Small and Medium-sized enterprises' (SME) partners aiming to provide evidence on the clinical utility and cost-effectiveness of Positron Emission Tomography (PET) imaging in diagnostic work-up of AD and to support clinical trial design by developing optimal quantitative methodology in an early AD population. In the Diagnostic and Patient Management Study (DPMS), 844 participants from eight centres across three clinical subgroups (245 subjective cognitive decline, 342 mild cognitive impairment, and 258 dementia) were included. The Prognostic and Natural History Study (PNHS) recruited pre-dementia subjects across 11 European parent cohorts (PCs). Approximately 1600 unique subjects with historical and prospective data were collected within this study. PET acquisition with [18F]flutemetamol or [18F]florbetaben radiotracers was performed and quantified using the Centiloid (CL) method. AMYPAD has significantly contributed to the AD field by furthering our understanding of amyloid deposition in the brain and the optimal methodology to measure this process. Main contributions so far include the validation of the dual-time window acquisition protocol to derive the fully quantitative non-displaceable binding potential (BP ND ), assess the value of this metric in the context of clinical trials, improve PET-sensitivity to emerging Aβ burden and utilize its available regional information, establish the quantitative accuracy of the Centiloid method across tracers and support implementation of quantitative amyloid-PET measures in the clinical routine. The AMYPAD consortium has succeeded in recruiting and following a large number of prospective subjects and setting up a collaborative framework to integrate data across European PCs. Efforts are currently ongoing in collaboration with ARIDHIA and ADDI to harmonize, integrate, and curate all available clinical data from the PNHS PCs, which will become openly accessible to the wider scientific community.

Exploring cognitive and biological correlates of sleep quality and their potential links with Alzheimer’s disease (ALFASleep project): protocol for an observational study

IntroductionThe growing worldwide prevalence of Alzheimer’s disease (AD) and the lack of effective treatments pose a dire medical challenge. Sleep disruption is also prevalent in the ageing population and is...

Feasibility of using abbreviated scan protocols with population-based input functions for accurate kinetic modeling of [18F]-FDG datasets from a long axial FOV PET scanner

BackgroundAccurate kinetic modeling of 18F-fluorodeoxyglucose ([18F]-FDG) positron emission tomography (PET) data requires accurate knowledge of the available tracer concentration in the plasma during the scan time, known as the arterial input function (AIF). The gold standard method to derive the AIF requires collection of serial arterial blood samples, but the introduction of long axial field of view (LAFOV) PET systems enables the use of non-invasive image-derived input functions (IDIFs) from large blood pools such as the aorta without any need for bed movement. However, such protocols require a prolonged dynamic PET acquisition, which is impractical in a busy clinical setting. Population-based input functions (PBIFs) have previously shown potential in accurate Patlak analysis of [18F]-FDG datasets and can enable the use of shortened dynamic imaging protocols. Here, we exploit the high sensitivity and temporal resolution of a LAFOV PET system and explore the use of PBIF with abbreviated protocols in [18F]-FDG total body kinetic modeling.MethodsDynamic PET data were acquired in 24 oncological subjects for 65 min following the administration of [18F]-FDG. IDIFs were extracted from the descending thoracic aorta, and a PBIF was generated from 16 datasets. Five different scaled PBIFs (sPBIFs) were generated by scaling the PBIF with the AUC of IDIF curve tails using various portions of image data (35–65, 40–65, 45–65, 50–65, and 55–65 min post-injection). The sPBIFs were compared with the IDIFs using the AUCs and Patlak Ki estimates in tumor lesions and cerebral gray matter. Patlak plot start time (t*) was also varied to evaluate the performance of shorter acquisitions on the accuracy of Patlak Ki estimates. Patlak Ki estimates with IDIF and t* = 35 min were used as reference, and mean bias and precision (standard deviation of bias) were calculated to assess the relative performance of different sPBIFs. A comparison of parametric images generated using IDIF and sPBIFs was also performed.ResultsThere was no statistically significant difference between AUCs of the IDIF and sPBIFs (Wilcoxon test: P > 0.05). Excellent agreement was shown between Patlak Ki estimates obtained using sPBIF and IDIF. Using the sPBIF55–65 with the Patlak model, 20 min of PET data (i.e., 45 to 65 min post-injection) achieved < 15% precision error in Ki estimates in tumor lesions compared to the estimates with the IDIF. Parametric images reconstructed using the IDIF and sPBIFs with and without an abbreviated protocol were visually comparable. Using Patlak Ki generated with an IDIF and 30 min of PET data as reference, Patlak Ki images generated using sPBIF55–65 with 20 min of PET data (t* = 45 min) provided excellent image quality with structural similarity index measure > 0.99 and peak signal-to-noise ratio > 55 dB.ConclusionWe demonstrate the feasibility of performing accurate [18F]-FDG Patlak analysis using sPBIFs with only 20 min of PET data from a LAFOV PET scanner.

Development of the Normalization Method for the Jagiellonian PET Scanner

This work aims at applying the theory of the component-based normalization for the Jagiellonian PET scanner, currently under development at the Jagiellonian University. In any Positron Emission Tomography acquisition, efficiency along a line-of-response can vary due to several physical and geometrical effects, leading to severe artifacts in the reconstructed image. To mitigate these effects, a normalization coefficient is applied to each line-of-response, defined as the product of several components. Specificity of the Jagiellonian PET scanner geometry is taken into account. Results obtained from GATE simulations are compared with preliminary results obtained from experimental data.

Artificial intelligence guided enhancement of digital PET: scans as fast as CT?

PurposeBoth digital positron emission tomography (PET) detector technologies and artificial intelligence based image post-reconstruction methods allow to reduce the PET acquisition time while maintaining diagnostic quality. The aim of this study was to acquire ultra-low-count fluorodeoxyglucose (FDG) ExtremePET images on a digital PET/computed tomography (CT) scanner at an acquisition time comparable to a CT scan and to generate synthetic full-dose PET images using an artificial neural network.MethodsThis is a prospective, single-arm, single-center phase I/II imaging study. A total of 587 patients were included. For each patient, a standard and an ultra-low-count FDG PET/CT scan (whole-body acquisition time about 30 s) were acquired. A modified pix2pixHD deep-learning network was trained employing 387 data sets as training and 200 as test cohort. Three models (PET-only and PET/CT with or without group convolution) were compared. Detectability and quantification were evaluated.ResultsThe PET/CT input model with group convolution performed best regarding lesion signal recovery and was selected for detailed evaluation. Synthetic PET images were of high visual image quality; mean absolute lesion SUVmax (maximum standardized uptake value) difference was 1.5. Patient-based sensitivity and specificity for lesion detection were 79% and 100%, respectively. Not-detected lesions were of lower tracer uptake and lesion volume. In a matched-pair comparison, patient-based (lesion-based) detection rate was 89% (78%) for PERCIST (PET response criteria in solid tumors)-measurable and 36% (22%) for non PERCIST-measurable lesions.ConclusionLesion detectability and lesion quantification were promising in the context of extremely fast acquisition times. Possible application scenarios might include re-staging of late-stage cancer patients, in whom assessment of total tumor burden can be of higher relevance than detailed evaluation of small and low-uptake lesions.