Min Scan Research Articles

Low-activity [18F]-somatostatin receptor (SSTR) imaging using [18F]SiTATE on a long axial field-of-view PET/CT scanner

Purpose18F-labelled somatostatin receptor tracers have recently gained popularity due to their better spatial resolution, longer half-life and lower costs compared to 68Ga-labeled tracers. The aim of this study was to evaluate the impact and limitations of reduced administered activities of [18F]SiTATE on image quality, lesion detectability and quantitative PET parameters in a long axial field-of-view (LAFOV) PET/CT scanner.MethodsTwenty-four patients with histologically confirmed neuroendocrine tumor, who underwent clinically indicated [18F]SiTATE PET/CT examination (3.0 MBq/kg, 5 min PET scan time) on a Siemens Biograph Vision Quadra LAFOV PET/CT, were included retrospectively in this study. PET list-mode data were rebinned for shorter frame durations to simulate 5 min scans with lower activities of injected radiotracer. A comparison of image reconstruction in high sensitivity (HS) and ultra-high sensitivity mode (UHS) mode was performed. Subjective image quality, noise and lesion detectability of n = 122 lesions were rated using a 5-point Likert scale. The molecular tumor volume (MTV), signal-to-noise ratio (SNR), tumor-to-liver activity concentration ratio (TLR) and standardized uptake values (SUV) were analyzed.ResultsSubjective image quality decreased with simulated reduction of injected activity with generally superior ratings in the UHS mode compared to the HS mode. Despite a reduction to 1 MBq/kg of [18F]SiTATE all lesions were still detected while at 0.25 MBq/kg lesion detectability decreased to 70% (HS) and 93% (UHS). Only minor changes in SUVmean and TLR were detected with reduced activity. However, reduced activities led to an increase in SUVSD, which in turn caused a decrease in SNR (at 1 MBq/kg: 7.3 in HS and 9.0 in UHS mode and an increase in deviation of the MTV.ConclusionReducing the administered activity of injected [18F]SiTATE by 66% to 1 MBq/kg (HS & UHS) is feasible in a LAFOV PET/CT scanner, maintaining clinically diagnostic image quality without statistically significant deviations in PET uptake parameters and MTV. Furthermore, in low activity [18F]SiTATE PET/CT, the UHS mode improves image quality and noise as well as lesion detectability compared to HS mode, further reinforcing the clinical benefits of this recently introduced reconstruction mode.

Simultaneous Concentration and T2 Mapping of Brain Metabolites by Fast Multi-Echo Spectroscopic Imaging.

The purpose of this study was to produce metabolite-specific T2 and concentration maps in a clinically compatible time frame. A multi-TE 2D MR spectroscopic imaging (MRSI) experiment (multi-echo single-shot MRSI [MESS-MRSI]) deployed truncated and partially sampled multi-echo trains from single scans and was combined with simultaneous multiparametric model fitting. It was tested invivo for the brain in five healthy subjects. Cramér-Rao lower bounds (CRLB) were used as the measure of performance. The novel method was compared with (1) traditional multi-echo multi-shot (MEMS) MRSI and, as proof of concept, with (2) a truncated version of MEMS, which mimics the MESS acquisition (MESS-mocked) on the original fully sampled MEMS dataset. MESS-MRSI simultaneously yields concentration and T2 maps with a nominal voxel size of ~2 cm3 with a 16 × 16 FOV matrix in 7 min scan time. The estimated values not only align well with the equivalent mocked experiment but are also in good agreement with the traditional threefold longer MEMS acquisition. The MESS-MRSI scheme extends former findings for single-voxel MESS, with improvements in CRLB ranging from 17% to 45% for concentrations and 10% to 23% for T2s when compared to traditional MEMS. This finding suggests that concentrations and T2 times can be reliably estimated in a multi-echo spectroscopic imaging exam by trading off spectral resolution (for some of the acquired TEs) with a significant reduction in scan time, as long as (1) an appropriate bidimensional frequency-TE model is deployed and (2) one TE is sampled in full. Thus, high spectral resolution information can be injected to the partially sampled TEs during fitting by prior knowledge from the one fully sampled TE. Tissue-type and regional distributions of 16 metabolite concentrations align well with the literature, and T2 distributions for five major metabolites are described by region and tissue. The novel MRSI acquisition strategy, based on partially sampled single-shot multi-echo trains twinned to multiparametric fitting, is optimally suited to provide simultaneous 2D concentration and T2 maps in clinic-compatible scan times. MESS principles allow embedding advanced MRSI techniques to further improve speed, coverage, or resolution. Preliminary findings from a cohort of five subjects reveal correlations between T2 relaxation times and the relative fraction of gray/white matter, suggesting tissue-type-dependent microstructural changes.

Leveraging small voxel with optimal acquisition time for [18F]mFBG total-body PET/CT imaging in pediatric patients with neuroblastoma: a preliminary study.

The advent of total-body PET/CT presents an opportunity for significant advancements in imaging of neuroblastoma with [18F]meta-fluorobenzylguanidine ([18F]mFBG). Small voxel imaging has proven to have better lesion detectability but need enough radioactivity counts. This study aims to balance shortened acquisition times and small voxel reconstruction to keep sufficient image quality and diagnostic confidence on [18F]mFBG total-body PET for neuroblastoma. We retrospectively enrolled 33 pediatric patients with neuroblastoma who underwent 37 [18F]mFBG total-body uEXPLORER PET/CT scans of 10-min duration. PET images were reconstructed with varying acquisition times (0.5-10min) and three matrix sizes (192 × 192, 512 × 512 and 1024 × 1024). The subjective (scored on a 5-point scale) and objective image quality (signal-to-noise ratio, SNR) of all the sets of reconstructed images were analyzed by nuclear medicine physicians. For indeterminate lesions identified in the group of 192 × 192 matrix with the 10-min scan (G192-10), diagnostic confidence was further evaluated in images reconstructed with the 512 × 512 and 1024 × 1024 matrices (G512 and G1024). Of the 33 patients with 37 [18F]mFBG PET/CT scans, 17 patients with 20 scans had positive [18F]mFBG PET/CT findings. Sufficient subjective image quality was achieved with at least 2-min acquisition of 192 × 192 matrix and 4-min acquisition of 512 × 512 matrix (with all scores ≥ 3). SNR increased with longer acquisition times for the same voxel size, while decreased as voxel size shrunk. Although the Curie and SIOPEN scores remained consistent across G192, G512, and G1024-10 groups, the G512 groups with at least 2-min acquisition and G1024-10 showed significantly higher confidence scores for characterizing indeterminate lesions on the G192-10 images, with almost all indeterminate lesions being rated as very confident. A matrix of 512 × 512 with a minimum of 4-min acquisition on [18F]mFBG total-body PET/CT is recommended for sufficient image quality and improved diagnostic confidence, particularly in detecting indeterminate lesions.

Fast and reliable quantitative measures of white matter development with magnetic resonance fingerprinting

Abstract Developmental cognitive neuroscience aims to shed light on evolving relationships between brain structure and cognitive development. To this end, quantitative methods that reliably measure individual differences in brain tissue properties are fundamental. Standard qualitative MRI sequences are influenced by scan parameters and hardware-related biases, and also lack physical units, making the analysis of individual differences problematic. In contrast, quantitative MRI can measure physical properties of the tissue but with the cost of long scan durations and sensitivity to motion. This poses a critical limitation for studying young children. Here, we examine the reliability of an efficient quantitative multiparameter mapping method - Magnetic Resonance Fingerprinting (MRF) - in children scanned longitudinally. We focus on T1 values in white matter, since quantitative T1 values are known to primarily reflect myelin content, a key factor in brain development. Forty-nine children aged 8-13y (mean 10.3y ±1.4) completed two scanning sessions 2-4 months apart. In each session, two 2-minute 3D-MRF scans at 1mm isotropic resolution were collected to evaluate the effect of scan duration on image quality and scan-rescan reliability. A separate calibration scan was used to measure B0 inhomogeneity and correct for bias. We examined the impact of scan time and B0 inhomogeneity correction on scan-rescan reliability of values in white matter, by comparing single 2-min and combined two 2-min scans, with and without B0-correction. Whole-brain voxel-based reliability analysis showed that combining two 2-min MRF scans improved reliability (pearson’s r=0.87) compared with a single 2-min scan (r=0.84), while B0-correction had no effect on reliability in white matter (r=0.86 and 0.83 4-min vs 2-min). Using diffusion tractography, we segmented major white matter fiber tracts and examined the profiles of MRF-derived T1 values along each tract. We found that T1 values from MRF showed similar or greater reliability compared with diffusion parameters. Lastly, we found that R1 (1/T1) values in multiple white matter tracts were significantly correlated with age. In sum, MRF-derived T1 values were highly reliable in a longitudinal sample of children and replicated known age effects. Reliability in white matter was improved by longer scan duration but was not affected by B0-correction, making it a quick and straightforward scan to collect. We propose that MRF provides a promising avenue for acquiring quantitative brain metrics in children and patient populations where scan time and motion are of particular concern.

A deep learning method for total-body dynamic PET imaging with dual-time-window protocols.

Prolonged scanning durations are one of the primary barriers to the widespread clinical adoption of dynamic Positron Emission Tomography (PET). In this paper, we developed a deep learning algorithm that capable of predicting dynamic images from dual-time-window protocols, thereby shortening the scanning time. This study includes 70 patients (mean age ± standard deviation, 53.61 ± 13.53years; 32 males) diagnosed with pulmonary nodules or breast nodules between 2022 to 2024. Each patient underwent a 65-min dynamic total-body [18F]FDG PET/CT scan. Acquisitions using early-stop protocols and dual-time-window protocols were simulated to reduce the scanning time. To predict the missing frames, we developed a bidirectional sequence-to-sequence model with attention mechanism (Bi-AT-Seq2Seq); and then compared the model with unidirectional or non-attentional models in terms of Mean Absolute Error (MAE), Bias, Peak Signal-to-Noise Ratio (PSNR), and Structural Similarity (SSIM) of predicted frames. Furthermore, we reported the comparison of concordance correlation coefficient (CCC) of the kinetic parameters between the proposed method and traditional methods. The Bi-AT-Seq2Seq significantly outperform unidirectional or non-attentional models in terms of MAE, Bias, PSNR, and SSIM. Using a dual-time-window protocol, which includes a 10-min early scan followed by a 5-min late scan, improves the four metrics of predicted dynamic images by 37.31%, 36.24%, 7.10%, and 0.014% respectively, compared to the early-stop protocol with a 15-min acquisition. The CCCs of tumor' kinetic parameters estimated with recovered full time-activity-curves (TACs) is higher than those with abbreviated TACs. The proposed algorithm can accurately generate a complete dynamic acquisition (65min) from dual-time-window protocols (10 + 5min).

Evaluation of the safety, biodistribution, dosimetry of [18F]AlF-NYM005 and initial experience in clear cell renal cell carcinoma: an interim analysis of a prospective trial.

This first-in-human study aimed to evaluate the radiation dosimetry and whole-body biodistribution of [18F]AlF-NYM005, a novel small-molecule carbonic anhydrase IX (CAIX) targeting agent, and to investigate its ability to detect CAIX-positive tumors using PET scans in a cohort of clear cell renal cell carcinoma (ccRCC) patients. [18F]AlF-NYM005 was synthesized using a fully automatic cassette module Mortenon M1 (Nuoyu, China). Thirty-five patients with a suspicious lesion considered primary renal malignancy or a history of ccRCC were prospectively recruited and studied. All patients underwent [18F]AlF-NYM005 PET/CT examinations and the maximum standardized uptake value (SUVmax) was measured on conventional [18F]AlF-NYM005 PET/CT images. Among these patients, five patients underwent dynamic [18F]AlF-NYM005 PET/CT scanning (120min) of the lower abdomen. Another subset of five ccRCC patients underwent sequential whole-body PET scans at 30, 60, 90, and 120min (one of the five patients underwent additional 150min and 180min scans) after [18F]AlF-NYM005 injection to assess biodistribution and dosimetry. The influx constant (Ki) was calculated from the dynamic [18F]AlF-NYM005 PET/CT data using the Patlak model. Whole-body biodistribution was calculated as time-activity curves (TACs) describing dynamic uptake patterns in the patients' major organs, followed by calculation of tracer kinetics and cumulative organ activity. Effective doses of [18F]AlF-NYM005 and individual organ doses were also calculated. [18F]AlF-NYM005 was successfully synthesized with a radiochemical purity of > 95% and an average labeling yield of 36.5 ± 8.3%. All patients tolerated the PET examinations well, and no adverse side effects were observed. The total body effective dose was 7.6E-03 mSv/MBq. The highest agent uptake was observed in the kidneys, stomach, and liver, contributing to an effective dose of 0.0126 ± 0.0029 mSv/MBq. The TACs showed optimal normal organ uptake with high tumor uptake and long retention of up to 2h post-injection. Notably, a rapid increase of the tracer followed by a rapid decrease in the blood pool, kidney, liver, and tumor lesions was observed, indicating that [18F]AlF-NYM005 was rapidly eliminated from blood and urine. For the kinetic data analysis, the Ki for the primary kidney lesions had a mean of 0.082 ± 0.057ml/g/min. The CAIX-positive tumors displayed rapid uptake, and all lesions were detectable within 30min, with no additional lesions observed in the subsequent multi-time point scans. The patient-level sensitivity, specificity, and accuracy of [18F]AlF-NYM005 PET/CT were 93.8%, 75.0%, and 90% for group 1 and 92.3%, 100%, and 93.3% for group 2, respectively. For per-lymph node analysis, [18F]AlF-NYM005 PET/CT demonstrated 92.9% sensitivity, 90.5% specificity, and 91.8% accuracy in diagnosing metastatic lymph nodes. For per-distant metastasis analysis, it showed 90.5% sensitivity, 91.3% specificity, and 90.6% accuracy. The SUVmax of [18F]AlF-NYM005 PET/CT for primary ccRCC lesions was 15.5 ± 7.35. Tumor uptake was positive correlated with immunohistochemical staining findings. This pilot study in ccRCC patients has demonstrated the safety, acceptable radiation dosimetry, favorable biodistribution, and exceptional tumor uptake of [18F]AlF-NYM005. The preliminary diagnostic study indicated the potential utility of [18F]AlF-NYM005 PET/CT, showing promising results in the diagnosis of primary or metastatic ccRCC. This study was registered at ClinicalTrial.gov (ChiCTR2200058108) as NYPILOT on 29 March, 2022.

Improved gradient echo magnitude- and phase-based mapping of using multiple RF spoiling increments at 3T and 7T.

The transverse relaxation time T holds significant relevance in clinical applications and research studies. Conventional T mapping approaches rely on spin-echo sequences, which require lengthy acquisition times and involve high radiofrequency (RF) power deposition. An alternative gradient echo (GRE) phase-based T mapping method, utilizing steady-state acquisitions at one small RF spoil phase increment, was recently demonstrated. Here, a modified magnitude- and phase-based T mapping approach is proposed, which improves estimations by simultaneous fitting of and signal amplitude ( ) at three or more RF spoiling phase increments, instead of assuming a fixed value. The feasibility of the magnitude-phase-based method was assessed by simulations, in phantom and in vivo experiments using skipped-CAIPI three-dimensional-echo-planar imaging (3D-EPI) for rapid GRE imaging. , and PD estimations obtained by our method were compared to of the phase-based method and and PD of spoiled GRE-based multi-parameter mapping using a multi-echo version of the same sequence. The agreement of the proposed with ground truth and reference values was higher than that of phase-based in simulations and in phantom data. While phase-based overestimation increases with actual and , the proposed method is accurate over a large range of physiologically meaningful and values. At the same time, precision is improved. In vivo results were in line with these observations. Accurate magnitude-phase-based T mapping is feasible in less than 5 min scan time for 1 mm nominal isotropic whole-head coverage at 3T and 7T.

Optimization of reconstruction in quantitative brain PET images: Benefits from PSF modeling and correction of edge artifacts.

Modern PET reconstruction algorithms incorporate point-spread-function (PSF) correction to mitigate partial volume effect. However, PSF correction can introduce edge artifacts that lead to quantification errors. Consequently, current international guidelines advise against using PSF correction in brain PET reconstruction. We aimed to investigate PSF-induced quantification errors in recent digital PET systems and identify conditions that mitigate them. This study utilized brain PET imaging with alginate-based realistic phantoms, simulating lesion-to-background activity ratios of 10:1 and 2:1, with eleven reconstruction parameter sets. Phantoms were prepared using a commercial anthropomorphic head phantom and two homemade inserts. Each insert contained a homogeneous 18F-FDG alginate background with hot spheres of varying diameter (3, 4, 6, 8, 10, 12, and 15mm). PET imaging was conducted on a digital PET-CT system Biograph Vision 600 (Siemens), with a 10 min scan duration. Imaging was performed with and without PSF correction, with 2, 4, 6, 12, 18, or 24 iterations in reconstruction, and with or without additional Gaussian postfiltering. We assessed the recovery coefficient (RC), contrast recovery coefficient (CRC), variability, and CRC-to-variability ratios for each sphere size and reconstruction parameter set. PSF-corrected images of the 10:1 spheres exhibited a nonmonotonic CRC-to-sphere diameter relationship due to edge artifacts overshoot in the 10mm-diameter sphere. In contrast, PSF images of the 2:1 spheres showed a monotonically increasing relationship. Non-PSF images of both phantoms showed an expected monotonically increasing CRC-to-sphere diameter relationship but with lower CRC values compared to PSF images. The nonmonotonic relationship observed with 10:1 spheres was mitigated by applying a 3-mm FWHM Gaussian postfiltering. For both phantoms, reconstructions with 6 iterations, PSF correction, and additional 3-mm FWHM Gaussian postfiltering demonstrated the highest CRC-to-variability ratios. Our findings indicate that Gaussian postfiltering suppresses PSF artifacts. This parameter set corrected the nonmonotonic CRC-to-sphere diameter relationship and improved the CRC-to-variability ratio compared to non-PSF reconstructions. Therefore, to enhance lesion detectability without compromising quantification accuracy, PSF correction coupled with Gaussian postfiltering should be used in brain PET.

Fast and reliable quantitative measures of white matter development with magnetic resonance fingerprinting.

Developmental cognitive neuroscience aims to shed light on evolving relationships between brain structure and cognitive development. To this end, quantitative methods that reliably measure individual differences in brain tissue properties are fundamental. Standard qualitative MRI sequences are influenced by scan parameters and hardware-related biases, and also lack physical units, making the analysis of individual differences problematic. In contrast, quantitative MRI can measure physical properties of the tissue but with the cost of long scan durations and sensitivity to motion. This poses a critical limitation for studying young children. Here, we examine the reliability and validity of an efficient quantitative multiparameter mapping method - Magnetic Resonance Fingerprinting (MRF) - in children scanned longitudinally. We focus on T1 values in white matter, since quantitative T1 values are known to primarily reflect myelin content, a key factor in brain development. Forty-nine children aged 8-13y (mean 10.3y ±1.4) completed two scanning sessions 2-4 months apart. In each session, two 2-minute 3D-MRF scans at 1mm isotropic resolution were collected to evaluate the effect of scan duration on image quality and scan-rescan reliability. A separate calibration scan was used to measure B0 inhomogeneity and correct for bias. We examined the impact of scan time and B0 inhomogeneity correction on scan-rescan reliability of values in white matter, by comparing single 2-min and combined two 2-min scans, with and without B0-correction. Whole-brain voxel-based reliability analysis showed that combining two 2-min MRF scans improved reliability (pearson's r=0.87) compared with a single 2-min scan (r=0.84), while B0-correction had no effect on reliability in white matter (r=0.86 and 0.83 4-min vs 2-min). Using diffusion tractography, we delineated MRF-derived T1 profiles along major white matter fiber tracts and found similar or higher reliability for T1 from MRF compared to diffusion parameters (based on a 10-minute dMRI scan). Lastly, we found that T1 values in multiple white matter tracts were significantly correlated with age. In sum, MRF-derived T1 values were highly reliable in a longitudinal sample of children and replicated known age effects. Reliability in white matter was improved by longer scan duration but was not affected by B0-correction, making it a quick and straightforward scan to collect. We propose that MRF provides a promising avenue for acquiring quantitative brain metrics in children and patient populations where scan time and motion are of particular concern.

Comprehensive examination of resting state fMRI connectomics yields new insights into brain function deficits in Gulf War illness after accounting for heterogeneity in brain impairment across the ill veteran population

An estimated 200,000 veterans (up to 32% of those deployed) of the 1991 Gulf War (GW) suffer from GW illness (GWI), an incompletely understood chronic medical condition, characterized by multiple symptoms indicative of brain function deficits in various domains. Epidemiologic and animal studies have associated GWI with exposure to neurotoxic chemicals such as nerve agents, organophosphate pesticides and pyridostigmine bromide. One factor that hampers mechanistic investigations into GWI is that there is considerable heterogeneity in brain impairments across the ill GW veteran population. This could reflect the underlying heterogeneity in both exposure to neurotoxic substances, as well as genetic predisposition or resistance to neurotoxicity. Only one of the validated case definitions, the Haley GWI criteria addresses this heterogeneity. It does so by breaking down GWI into three main syndrome variants (GWS1, GWS2, and GWS3) based on factor analysis of symptoms presented by GWI veterans. Resting state fMRI (rsfMRI) is a uniquely useful brain imaging technique in that in a 10-min fMRI scan it can probe numerous brain function domains simultaneously. In this study, we employed a connectomics approach and machine learning on rsfMRI data from a cohort of GW veterans to extract neuroimaging biomarkers specific to each of the three Haley GWI syndromes. Our results revealed a number of new insights into brain function impairment specific to each syndrome group. The findings indicate that these deficits may by and large be driven by brain mechanisms. We also found that pooling the data of all three syndromes in GWI group, as is done by commonly employed case definitions of GWI resulted in failure to detect the fMRI signatures of a lot of these brain impairments.

Automatic Brain Tissue and Lesion Segmentation and Multi-Parametric Mapping of Contrast-Enhancing Gliomas without the Injection of Contrast Agents: A Preliminary Study.

This study aimed to develop a rapid, 1 mm3 isotropic resolution, whole-brain MRI technique for automatic lesion segmentation and multi-parametric mapping without using contrast by continuously applying balanced steady-state free precession with inversion pulses throughout incomplete inversion recovery in a single 6 min scan. Modified k-means clustering was performed for automatic brain tissue and lesion segmentation using distinct signal evolutions that contained mixed T1/T2/magnetization transfer properties. Multi-compartment modeling was used to derive quantitative multi-parametric maps for tissue characterization. Fourteen patients with contrast-enhancing gliomas were scanned with this sequence prior to the injection of a contrast agent, and their segmented lesions were compared to conventionally defined manual segmentations of T2-hyperintense and contrast-enhancing lesions. Simultaneous T1, T2, and macromolecular proton fraction maps were generated and compared to conventional 2D T1 and T2 mapping and myelination water fraction mapping acquired with MAGiC. The lesion volumes defined with the new method were comparable to the manual segmentations (r = 0.70, p < 0.01; t-test p > 0.05). The T1, T2, and macromolecular proton fraction mapping values of the whole brain were comparable to the reference values and could distinguish different brain tissues and lesion types (p < 0.05), including infiltrating tumor regions within the T2-lesion. Highly efficient, whole-brain, multi-contrast imaging facilitated automatic lesion segmentation and quantitative multi-parametric mapping without contrast, highlighting its potential value in the clinic when gadolinium is contraindicated.

Spatiotemporal encoding MRI in a portable low-field system.

Demonstrate the potential of spatiotemporal encoding (SPEN) MRI to deliver largely undistorted 2D, 3D, and diffusion weighted images on a 110 mT portable system. SPEN's quadratic phase modulation was used to subsample the low-bandwidth dimension of echo planar acquisitions, delivering alias-free images with an enhanced immunity to image distortions in a laboratory-built, low-field, portable MRI system lacking multiple receivers. Healthy brain images with different SPEN time-bandwidth products and subsampling factors were collected. These compared favorably to EPI acquisitions including topup corrections. Robust 3D and diffusion weighted SPEN images of diagnostic value were demonstrated, with 2.5 mm isotropic resolutions achieved in 3 min scans. This performance took advantage of the low specific absorption rate and relative long TEs associated with low-field MRI. SPEN MRI provides a robust and advantageous fast acquisition approach to obtain faithful 3D images and DWI data in low-cost, portable, low-field systems without parallel acceleration.

Simulation of time-intensity curve based on k-space filling in breast dynamic contrast-enhanced three-dimensional magnetic resonance imaging.

This study elucidated the effects of a three-dimensional k-space trajectory incorporating the partial Fourier (PF) technique on a time-intensity curve (TIC) in a dynamic contrast-enhanced magnetic resonance imaging of a typical malignant breast tumor using a digital phantom. Images were obtained from the Cancer Imaging Archive Open Data for Breast Cancer, and 1-min scans with high temporal resolution were analyzed. The order of the k-space trajectory was set as Linear (sequential), Low-High (centric), PF (62.5%; Z-, Y-, and both directions), and Low-High Radial. k0 (center of the k-space) timing and TIC shape were affected by the chosen k-space trajectory and implementation of the PF technique. A small TIC gradient was obtained using a Low-High Radial order. If the k-space filling method (particularly the radial method) produces a gentle TIC gradient, misinterpretation could arise during the assessment of tumor malignancy status.

Dopamine Transporter SPECT with 12-Minute Scan Duration Using Multiple-Pinhole Collimators.

This study evaluated the potential to reduce the scan duration in dopamine transporter (DAT) SPECT when using a second-generation multiple-pinhole (MPH) collimator designed for brain SPECT with improved count sensitivity and improved spatial resolution compared with parallel-hole and fanbeam collimators. Methods: The retrospective study included 640 consecutive clinical DAT SPECT studies that had been acquired in list mode with a triple-head SPECT system with MPH collimators and a 30-min net scan duration after injection of 181 ± 10 MBq of [123I]FP-CIT. Raw data corresponding to scan durations of 20, 15, 12, 8, 6, and 4 min were obtained by restricting the events to a proportionally reduced time interval of the list-mode data for each projection angle. SPECT images were reconstructed iteratively with the same parameter settings irrespective of scan duration. The resulting 5,120 SPECT images were assessed for a neurodegeneration-typical reduction in striatal signal by visual assessment, conventional specific binding ratio analysis, and a deep convolutional neural network trained on 30-min scans. Results: Regarding visual interpretation, image quality was considered diagnostic for all 640 patients down to a 12-min scan duration. The proportion of discrepant visual interpretations between 30 and 12 min (1.2%) was not larger than the proportion of discrepant visual interpretations between 2 reading sessions of the same reader at a 30-min scan duration (1.5%). Agreement with the putamen specific binding ratio from the 30-min images was better than expected for 5% test-retest variability down to a 10-min scan duration. A relevant change in convolutional neural network-based automatic classification was observed at a 6-min scan duration or less. Conclusion: The triple-head SPECT system with MPH collimators allows reliable DAT SPECT after administration of about 180 MBq of [123I]FP-CIT with a 12-min scan duration.

The clinical acceptability of short versus long duration acquisitions for head and neck cancer using long-axial field-of-view PET/CT: a retrospective evaluation

PurposeTo evaluate the utility of long duration (10 min) acquisitions compared to standard 4 min scans in the evaluation of head and neck cancer (HNC) using a long-axial field-of-view (LAFOV) system in 2-[18F]FDG PET/CT.MethodsHNC patients undergoing LAFOV PET/CT were included retrospectively according to a predefined sample size calculation. For each acquisition, FDG avid lymph nodes (LN) which were highly probable or equivocal for malignancy were identified by two board certified nuclear medicine physicians in consensus. The aim of this study was to establish the clinical acceptability of short-duration (4 min, C40%) acquisitions compared to full-count (10 min, C100%) in terms of the detection of LN metastases in HNC. Secondary endpoints were the positive predictive value for LN status (PPV) and comparison of SUVmax at C40% and C100%. Histology reports or confirmatory imaging were the reference standard.ResultsA total of 1218 records were screened and target recruitment was met with n = 64 HNC patients undergoing LAFOV. Median age was 65 years (IQR: 59–73). At C40%, a total of 387 lesions were detected (highly probable LN n = 274 and equivocal n = 113. The total number of lesions detected at C100% acquisition was 439, of them 291 (66%) highly probable LN and 148 (34%) equivocal. Detection rate between the two acquisitions did not demonstrate any significant differences (Pearson’s Chi-Square test, p = 0.792). Sensitivity, specificity, PPV, NPV and accuracy for C40% were 83%, 44%, 55%, 76% and 36%, whilst for C100% were 85%, 56%, 55%, 85% and 43%, respectively. The improved accuracy reached borderline significance (p = 0.057). At the ROC analysis, lower SUVmax was identified for C100% (3.5) compared to C40% (4.5).ConclusionIn terms of LN detection, C40% acquisitions showed no significant difference compared to the C100% acquisitions. There was some improvement for lesions detection at C100%, with a small increment in accuracy reaching borderline significance, suggestive that the higher sensitivity afforded by LAFOV might translate to improved clinical performance in some patients.

A Novel 2D/3D X-ray Microscopy Alignment and Inspection Solution for Thermocompression Bonding (TCB) in a Highly Integrated Flip Chip Fan-Out Wafer Level Package (FO-WLP)

As packaging drives to extend the capabilities of Moore’s Law via heterogenous integration, numerous bonding technologies have emerged as potential pathways, allowing for integration of both a variety of devices in the lateral space as well as vertical integration of chips via stacking. As vertical integration on interposer becomes more complex due to shrinking CDs and increasing die layers, alignment and shape control in the bonding process becomes critical. Thermocompression bonding (TCB) is particularly well-suited for larger die, where localized reflow allows a better control of chip gap height and tilt throughout the bonding process. TCB systems require both high accuracy and repeatability in all dimensions to provide a reliable system in package. While a 2D system can provide a plan view assessment of a single bond layer between two chips, it falls short in characterizing the critical z-dimension in a highly integrated chip stacking scenario. Therefore a robust solution is needed for both system alignment validation in the x,y plane as well as a capability to explore gap height and bump quality/buried issues in high aspect ratio TSV. This paper will explore an x-ray application of a stacked 15-layer die-to-interposer structure to qualitatively validate overall health of the TSV (bond, pad, fill) via a nondestructive volumetric method as well as quantitatively evaluate stacked die for via/ball/pad alignment to determine overall alignment shift during the bonding process. In the test vehicle for a flip chip FO-WLP process flow first presented by IMEC, a silicon (Si) bridge is utilized to connect the logic and through-package via dies with a bump pitch of 20µm for the logic die interconnect. This is done by carefully aligning the logic dies on the carrier and then placing the through-package dies aligned to the carrier and logic dies. In the final step, a high accuracy placement and stacking TCB tool attaches the Si bridge. To perform an accurate assessment for bump alignment and bond quality, an initial high-resolution 3D x-ray scan is performed on a 1.5mm3 region of interest with over 2,000 individual projections at a 1.4µm voxel resolution with a 4x objective, taking approximately two hours. The dataset is put through a deep-learning algorithm which generates an AI model. This model is then applied to a faster scan of 15 minutes with a 1.4µm voxel resolution for the same field of view (FOV) on a nearby array and the data is collected and processed. To verify alignment of the entire sample, data is collected on the tightest pitch (in this case 20µm) oriented in both the vertical (x) and horizontal (y) plane in the through-silicon via (TSV) region. The z-plane is analyzed and processed by computer vision algorithms, and individual interconnects are then quantified and sorted for solder height (z), width (x,y) and TSV misalignment (deviation from expected center, x1y1 → x2y2). To validate the model, a high-resolution uncorrected 20h scan and a 15min scan based on deep learning are collected for the same region of interest (ROI). The data is comparable. Furthermore, the global misalignment data between both datasets demonstrates similar misalignment propagating through the 15-layer stack.

The effect of a mindfulness-based body scan exercise on food intake during TV watching

In some studies mindfulness is associated with reduced food consumption, but the underlying mechanisms are less well researched. One potential mechanism is that mindfulness increases attention toward feelings of fullness. Additionally, experimental research on mindfulness and food intake has primarily been conducted in constrained laboratory settings, where it may be easier for participants to notice their internal bodily signals, as opposed to the real world where individuals are often engaged in other activities while eating. The effect of mindfulness on food intake while participants are distracted remains unexplored. This study therefore aimed to examine whether a mindfulness-based body scan exercise reduced food consumption within a distracted environment by increasing attention toward feelings of fullness. Participants (n = 137) listened to a 10-minute body scan meditation, or a 10-minute visualisation (control) meditation. They were then given a bowl of crisps to consume while watching a 10-minute TV show segment. Participants also completed measures assessing proposed mediators, including state mindfulness, attention to bodily sensations and eating automaticity. The body scan manipulation increased state mindfulness but had no direct effect on the other mediators or on food intake (intervention M = 34.79g, SD = 24.06; control M = 33.16g, SD = 23.88). State mindfulness was positively correlated with attention to bodily sensations while eating. Lower eating automaticity and greater reliance on decreased food appeal and physical satisfaction to stop eating were found to be associated with lower food intake. Contrary to previous studies, we found no evidence that a mindfulness body scan reduces food consumption when participants are distracted. Future research should examine the specific conditions under and mechanisms by which mindfulness may influence food consumption.

Ex vivo imaging of subacute myocardial ischemia with ultra-short echo time 3-D quantitative T1-mapping MRI in mice

Abstract Introduction Cardiac magnetic resonance (CMR) is important tool for assessment of structure and function of the myocardium in various cardiac conditions, such as after myocardial infarction (MI). CMR methods rely solely on multi-slice 2-D imaging, which tends to be slow, since every slice is imaged separately with the &amp;gt;3 min scan time. Furthermore, multi-slice methods are somewhat approximate, due to the slice thickness, which is usually around 1 mm for mice and 8 mm for humans. Therefore, 3-D CMR imaging methods with isotropic resolution are urgently needed. In this study, we present quantitative, ultra-short echo time 3-D Look-Locker T1[1] Multi-Band SWeep Imaging with Fourier Transform[2] and Compressed Sensing[3] (LL MB-SWIFT-CS) technique for imaging in MI mice hearts ex vivo. Purpose To develop an ultra-short echo time 3-D CMR method for imaging subacute myocardial ischemia quantitatively and in an accelerated way. Materials and Methods Hearts were collected 7 days after Left Anterior Descending (LAD) Coronary Artery was ligated in C57BL mice, fixated in 4% PFA in PBS and imaged with LL MB-SWIFT-CS MRI. The heart was scanned in 3-D with a total acquisition time of 3.25 min with resolution of 256³. For T1 determination, saturation recovery (SR) of the longitudinal magnetization was measured with following parameters: TR=3 ms, FA=4º, FOV=25 mm³, total number of unique spokes acquired=16384 and spokes per LL curve=1024, filling the 3-D data space homogeneously 16 times during the recovery. Total scan time was 52 min. After imaging, the SR LL curve was reconstructed into 32 images with CS reconstruction. For comparison, we imaged the hearts with 2-D MRI TRAFF2-mapping method[4] and histology. For regions of interests (ROIs) analysis, the damaged and remote ROI areas were observed from 2-D MR images and drawn to corresponding anatomical 3-D images. The same ROIs were then used to collect the T1 relaxation time data. For histology, standard paraffin embedding, and tissue processing protocols were used. 4 μm thick sections were cut and stained with Hematoxylin Eosin and Sirius Red staining. Results and Discussion The T1 relaxation time values were elevated in the damaged areas (p&amp;lt;0.005) (Fig. 1), as shown earlier[5,6]. The T1 values in the ischemic and remote myocardium were 0.76±0.03s and 0.70±0.02s, respectively. Ischemic areas can also be observed visually in the T1- and 2D TRAFF2-maps (Fig. 2). Sirius Red staining showed increased collagen formation in the ischemic myocardium, supporting the CMR findings. Moreover, hematoxylin-eosin staining showed loss of cardiomyocytes and coronary capillaries, and infiltration of inflammatory cells, like macrophages and lymphocytes. Conclusion With this method, we were able to detect the statistically significant differences between damaged and remote tissue based on the T1-relaxation times within the myocardium, allowing isotropic quantitative 3-D assessment of the entire myocardium.T1 values for MB-SWIFT-CSVisual validation of MB-SWIFT-CS

Optimization of Y-90 Radioembolization Imaging for Post-Treatment Dosimetry on a Long Axial Field-of-View PET/CT Scanner.

PET imaging after yttrium-90 (Y-90) radioembolization is challenging because of the low positron fraction of Y-90 (32 × 10-6). The resulting low number of events can be compensated by the high sensitivity of long axial field-of-view (LAFOV) PET/CT scanners. Nevertheless, the reduced event statistics require optimization of the imaging protocol to achieve high image quality (IQ) and quantification accuracy sufficient for post-treatment dosimetry. Two phantoms (NEMA IEC and AbdoMan phantoms, mimicking human liver) filled with Y-90 and a 4:1 sphere (tumor)-to-background ratio were scanned for 24 h with the Biograph Vision Quadra (Siemens Healthineers). Eight patients were scanned after Y-90 radioembolization (1.3-4.7 GBq) using the optimized protocol (obtained by phantom studies). The IQ, contrast recovery coefficients (CRCs) and noise were evaluated for their limited and full acceptance angles, different rebinned scan durations, numbers of iterations and post-reconstruction filters. The s-value-based absorbed doses were calculated to assess their suitability for dosimetry. The phantom studies demonstrate that two iterations, five subsets and a 4 mm Gaussian filter provide a reasonable compromise between a high CRC and low noise. For a 20 min scan duration, an adequate CRC of 56% (vs. 24 h: 62%, 20 mm sphere) was obtained, and the noise was reduced by a factor of 1.4, from 40% to 29%, using the full acceptance angle. The patient scan results were consistent with those from the phantom studies, and the impacts on the absorbed doses were negligible for all of the studied parameter sets, as the maximum percentage difference was -3.89%. With 2i5s, a 4 mm filter and a scan duration of 20 min, IQ and quantification accuracy that are suitable for post-treatment dosimetry of Y-90 radioembolization can be achieved.

Calf or grass – What would the cow choose?

The growing interest for keeping dairy cows with their calves for an extended period after calving is putting pressure on the scientific community to investigate the effects of cow-calf contact systems on the animals´ welfare. The main aims of this study were to investigate the dairy cows´ motivation for accessing their calves over a fresh pasture, and to evaluate if their motivation decreased with increasing calf age. Twenty-two Swedish Red and Swedish Holstein cow-calf pairs were enrolled at calving. The dams were housed in a robotic barn with free access to outdoor pasture, where the calves were kept during pasture season. The behaviours of the dams were recorded on three separate test days occurring every two weeks, starting when the calves were on average 10 weeks old. During test days, the calves were confined to a heavily grazed area, while the dams had free access both to the calf area and to an adjacent fresh pasture. Which of the areas the dams entered first upon returning outdoors from the barn, and what behaviours they performed in which area were registered using 10-min scan sampling during 8 h per day. The dams spent more time outdoors on Test day I (76.8±3.09%; LSMeans±SEM) compared to Day II (60.9±3.86%; P=0.006), while Day III (66.8±4.38%) did not differ from Day I (P=0.15) or Day II (P=0.55). On Test day II, they chose the calf area 54±10.05% of the times they returned to pasture, which was significantly more often than during Day I (18.2±4.96%; P=0.01), while no difference was found between Day III (37.1±9.86%) and Day I (P=0.17) or Day II (P=0.5). There was no effect of breed on total time spent outdoors, but Holstein dams tended to spend more outdoor time in the calf area (36.4±5.28%) than Swedish Red dams (24.2±3.95%; P=0.09). Upon returning outdoors, Holstein dams also chose the calf area over fresh pasture more often (46.0±7.19%) than did Swedish Red dams (25.2±6.21%; P=0.05). Primiparous cows tended to choose the calf area over fresh pasture more often (46.9±6.11%) than multiparous cows (24.5±7.25%; P=0.06). Exploratory analyses suggest that the effects of test day were more affected by the ambient weather than by the age of the calves. The study results provide some further information about factors influencing maternal motivation to reunite with their calves on pasture. However, further research is needed so that cow-calf contact systems can be designed to enable good welfare.