Prior to the implementation of arterial spin labeling (ASL) in clinical multi-center studies, it is important to establish its status quo inter-vendor reproducibility. This study evaluates and ...compares the intra- and inter-vendor reproducibility of pseudo-continuous ASL (pCASL) as clinically implemented by GE and Philips.
22 healthy volunteers were scanned twice on both a 3T GE and a 3T Philips scanner. The main difference in implementation between the vendors was the readout module: spiral 3D fast spin echo vs. 2D gradient-echo echo-planar imaging respectively. Mean and variation of cerebral blood flow (CBF) were compared for the total gray matter (GM) and white matter (WM), and on a voxel-level.
Whereas the mean GM CBF of both vendors was almost equal (p = 1.0), the mean WM CBF was significantly different (p<0.01). The inter-vendor GM variation did not differ from the intra-vendor GM variation (p = 0.3 and p = 0.5 for GE and Philips respectively). Spatial inter-vendor CBF and variation differences were observed in several GM regions and in the WM.
These results show that total GM CBF-values can be exchanged between vendors. For the inter-vendor comparison of GM regions or WM, these results encourage further standardization of ASL implementation among vendors.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Objectives
Alzheimer’s disease (AD) and frontotemporal (FTD) dementia can be differentiated using
18
F-2-deoxy-2-fluoro-D-glucose (FDG)-PET. Since cerebral blood flow (CBF) is related to glucose ...metabolism, our aim was to investigate the extent of overlap of abnormalities between AD and FTD.
Methods
Normalized FDG-PET and arterial spin labelling (ASL-MRI)-derived CBF was measured in 18 AD patients (age, 64 ± 8), 12 FTD patients (age, 61 ± 8), and 10 controls (age, 56 ± 10). Voxel-wise comparisons, region-of-interest (ROI), correlation, and ROC curve analyses were performed.
Results
Voxel-wise comparisons showed decreased CBF and FDG uptake in AD compared with controls and FTD in both precuneus and inferior parietal lobule (IPL). Compared with controls and AD, FTD patients showed both hypometabolism and hypoperfusion in medial prefrontal cortex (mPFC). ASL and FDG were related in precuneus (
r
= 0.62,
p
< 0.001), IPL (
r
= 0.61,
p
< 0.001), and mPFC across groups (
r
= 0.74,
p
< 001). ROC analyses indicated comparable performance of perfusion and metabolism in the precuneus (AUC, 0.72 and 0.74), IPL (0.85 and 0.94) for AD relative to FTD, and in the mPFC in FTD relative to AD (both 0.68).
Conclusions
Similar patterns of hypoperfusion and hypometabolism were observed in regions typically associated with AD and FTD, suggesting that ASL-MRI provides information comparable to FDG-PET.
Key Points
•
Similar patterns of hypoperfusion and hypometabolism were observed in patients with dementia.
•
For both imaging modalities, parietal abnormalities were found in Alzheimer’s disease.
•
For both imaging modalities, prefrontal abnormalities were found in frontotemporal dementia.
Background
Multiple sclerosis (MS) is characterized by pathology in white matter (WM) and atrophy of grey matter (GM), but it remains unclear how these processes are related, or how they influence ...clinical progression.
Objective
To study the spatial and temporal relationship between GM atrophy and damage in connected WM in relapsing–remitting (RR) MS in relation to clinical progression.
Methods
Healthy control (HC) and early RRMS subjects visited our center twice with a 1-year interval for MRI and clinical examinations, including the Expanded Disability Status Scale (EDSS) and Multiple Sclerosis Functional Composite (MSFC) scores. RRMS subjects were categorized as MSFC decliners or non-decliners based on ΔMSFC over time. Ten deep (D)GM and 62 cortical (C) GM structures were segmented and probabilistic tractography was performed to identify the connected WM. WM integrity was determined per tract with, amongst others, fractional anisotropy (FA), mean diffusivity (MD), neurite density index (NDI), and myelin water fraction (MWF). Linear mixed models (LMMs) were used to investigate GM and WM differences between HC and RRMS, and between MSFC decliners and non-decliners. LMM was also used to test associations between baseline WM
z
-scores and changes in connected GM
z
-scores, and between baseline GM
z
-scores and changes in connected WM
z
-scores, in HC/RRMS subjects and in MSFC decliners/non-decliners.
Results
We included 13 HCs and 31 RRMS subjects with an average disease duration of 3.5 years and a median EDSS of 3.0. Fifteen RRMS subjects showed declining MSFC scores over time, and they showed higher atrophy rates and greater WM integrity loss compared to non-decliners. Lower baseline WM integrity was associated with increased CGM atrophy over time in RRMS, but not in HC subjects. This effect was only seen in MSFC decliners, especially when an extended WM
z
-score was used, which included FA, MD, NDI and MWF. Baseline GM measures were not significantly related to WM integrity changes over time in any of the groups.
Discussion
Lower baseline WM integrity was related to more cortical atrophy in RRMS subjects that showed clinical progression over a 1-year follow-up, while baseline GM did not affect WM integrity changes over time. WM damage, therefore, seems to drive atrophy more than conversely.
Objectives
To investigate whether a new magnetic resonance image (MRI) technique called T2*-weighted fluid attenuation inversion recovery (FLAIR*) can differentiate between multiple sclerosis (MS) ...and vascular brain lesions, at 7 Tesla (T).
Methods
We examined 16 MS patients and 16 age-matched patients with (risk factors for) vascular disease. 3D-FLAIR and T2*-weighted images were combined into FLAIR* images. Lesion type and intensity, perivascular orientation and presence of a hypointense rim were analysed.
Results
In total, 433 cerebral lesions were detected in MS patients versus 86 lesions in vascular patients. Lesions in MS patients were significantly more often orientated in a perivascular manner: 74 % vs. 47 % (
P
< 0.001). Ten MS lesions (2.3 %) were surrounded by a hypointense rim on FLAIR*, and 24 MS lesions (5.5 %) were hypointense on T2*. No lesions in vascular patients showed any rim or hypointensity. Specificity of differentiating MS from vascular lesions on 7-T FLAIR* increased when the presence of a central vessel was taken into account (from 63 % to 88 %), most obviously for deep white matter lesions (from 69 % to 94 %). High sensitivity remained (81 %).
Conclusion
7-T FLAIR* improves differentiation between MS and vascular lesions based on lesion location, perivascular orientation and presence of hypointense (rims around) lesions.
Key Points
•
A new MRI technique T2*-weighted fluid attenuation inversion recovery (FLAIR*) was investigated.
• FLAIR* at 7-T MRI combines FLAIR and T2* images into a single image.
• FLAIR* at 7 T does not require enhancement with contrast agents.
•High-resolution 7-T FLAIR* improves differentiation between MS and vascular brain lesions.
• FLAIR* revealed a central vessel more frequently in MS than vascular lesions.
Aim
A pilot study to phenotype young adults (< 40 years) with Type 2 diabetes mellitus.
Methods
Twenty people with Type 2 diabetes (aged 18–40 years), 10 lean and 10 obese control subjects underwent ...detailed assessment, including tagged cardiac magnetic resonance imaging, inflammatory proteins, lipids, vitamin D and maximal oxygen uptake. Outcomes were compared between the group with Type 2 diabetes and the control group.
Results
Mean (standard deviation) age, Type 2 diabetes duration and BMI in the group with Type 2 diabetes were 31.8 (6.6) years, 4.7 (4.0) years and 33.9 (5.8) kg/m2 respectively. Compared with lean control subjects, those with Type 2 diabetes had more deleterious profiles of hyperlipidaemia, vitamin D deficiency, inflammation and maximal oxygen uptake relative to body mass. However, there was no difference between the group with Type 2 diabetes and the obese control group. The group with Type 2 diabetes had a higher left ventricular mass and a trend towards concentric remodelling compared with the lean control group (P = 0.002, P = 0.052) but not the obese control group (P > 0.05). Peak early diastolic strain rate was reduced in the group with Type 2 diabetes 1.51 (0.24)/s compared with the lean control 1.97 (0.34)/s, P = 0.001 and obese control 1.78 (0.39)/s, P = 0.042 group.
Conclusions
Young adults with Type 2 diabetes and those with obesity have similar adverse cardiovascular risk profiles, higher left ventricular mass and a trend towards left ventricular concentric remodelling. In addition, those with Type 2 diabetes demonstrate diastolic dysfunction, a known risk marker for future heart failure and mortality.
What's new?
Twenty young adults with Type 2 diabetes mellitus were extensively phenotyped, including tagged cardiac magnetic resonance imaging, and variables compared with lean and obese control subjects.
Young adults with Type 2 diabetes were characterized by dyslipidaemia, hypertension, abnormal liver function, vitamin D deficiency, a pro‐inflammatory state, a higher cardiac mass and a trend towards left ventricular concentric remodelling compared with lean, but not obese control subjects.
Diastolic dysfunction was identified in this group with Type 2 diabetes.
Although the added diagnostic value of arterial spin-labeling is shown in various cerebral pathologies, its use in clinical practice is limited. To encourage clinical adoption of ASL, we investigated ...the reproducibility of CBF measurements and the effects of variations in acquisition parameters compared to the recommended ASL implementation.
Thirty-four volunteers (mean age, 57.8 ± 17.0 years; range, 22-80 years) underwent two separate sessions (1.5T and 3T scanners from a single vendor) using a 15-channel head coil. Both sessions contained repeated 3D and 2D pseudocontinuous arterial spin-labeling scans using vendor-recommended acquisition parameters (recommendation paper-based), followed by three 3D pseudocontinuous arterial spin-labeling scans, two with postlabeling delays of 1600 and 2000 ms and one with increased spatial resolution. All scans were single postlabeling delay. Intrasession (identical acquisitions, scanned five minutes apart) and intersession (first 2D and 3D acquisitions of two sessions) reproducibility was examined as well as the effect of parameter variations on CBF.
Intrasession CBF reproducibility was similar across image readouts and field strengths (within-subject coefficient of variation between 4.0% and 6.7%). Intersession within-subject coefficient of variation ranged from 6.6% to 14.8%. At 3T, the 3D acquisition with a higher spatial resolution resulted in less mixing of GM and WM signal, thus decreasing the bias in GM CBF between the 2D and 3D acquisitions (ΔCBF = 2.49 mL/100g/min
< .001). Postlabeling delay variations caused a modest bias (ΔCBF between -3.78
< .001 and 2.83
< .001 mL/100g/min).
Arterial spin-labeling imaging is reproducible at both field strengths, and the reproducibility is not significantly correlated with age. Furthermore, 3T tolerates more acquisition parameter variations and allows more extensive optimizations so that 3D and 2D acquisitions can be compared.
Arterial spin labeling (ASL) has undergone significant development since its inception, with a focus on improving standardization and reproducibility of its acquisition and quantification. In a ...community-wide effort towards robust and reproducible clinical ASL image processing, we developed the software package ExploreASL, allowing standardized analyses across centers and scanners.
The procedures used in ExploreASL capitalize on published image processing advancements and address the challenges of multi-center datasets with scanner-specific processing and artifact reduction to limit patient exclusion. ExploreASL is self-contained, written in MATLAB and based on Statistical Parameter Mapping (SPM) and runs on multiple operating systems. To facilitate collaboration and data-exchange, the toolbox follows several standards and recommendations for data structure, provenance, and best analysis practice.
ExploreASL was iteratively refined and tested in the analysis of >10,000 ASL scans using different pulse-sequences in a variety of clinical populations, resulting in four processing modules: Import, Structural, ASL, and Population that perform tasks, respectively, for data curation, structural and ASL image processing and quality control, and finally preparing the results for statistical analyses on both single-subject and group level. We illustrate ExploreASL processing results from three cohorts: perinatally HIV-infected children, healthy adults, and elderly at risk for neurodegenerative disease. We show the reproducibility for each cohort when processed at different centers with different operating systems and MATLAB versions, and its effects on the quantification of gray matter cerebral blood flow.
ExploreASL facilitates the standardization of image processing and quality control, allowing the pooling of cohorts which may increase statistical power and discover between-group perfusion differences. Ultimately, this workflow may advance ASL for wider adoption in clinical studies, trials, and practice.
The relevance of cortical grey matter pathology in multiple sclerosis has become increasingly recognized over the past decade. Unfortunately, a large part of cortical lesions remain undetected on ...magnetic resonance imaging using standard field strength. In vivo studies have shown improved detection by using higher magnetic field strengths up to 7 T. So far, a systematic histopathological verification of ultra-high field magnetic resonance imaging pulse sequences has been lacking. The aim of this study was to determine the sensitivity of 7 T versus 3 T magnetic resonance imaging pulse sequences for the detection of cortical multiple sclerosis lesions by directly comparing them to histopathology. We obtained hemispheric coronally cut brain sections of 19 patients with multiple sclerosis and four control subjects after rapid autopsy and formalin fixation, and scanned them using 3 T and 7 T magnetic resonance imaging systems. Pulse sequences included T1-weighted, T2-weighted, fluid attenuated inversion recovery, double inversion recovery and T2*. Cortical lesions (type I-IV) were scored on all sequences by an experienced rater blinded to histopathology and clinical data. Staining was performed with antibodies against proteolipid protein and scored by a second reader blinded to magnetic resonance imaging and clinical data. Subsequently, magnetic resonance imaging images were matched to histopathology and sensitivity of pulse sequences was calculated. Additionally, a second unblinded (retrospective) scoring of magnetic resonance images was performed. Regardless of pulse sequence, 7 T magnetic resonance imaging detected more cortical lesions than 3 T. Fluid attenuated inversion recovery (7 T) detected 225% more cortical lesions than 3 T fluid attenuated inversion recovery (Z = 2.22, P < 0.05) and 7 T T2* detected 200% more cortical lesions than 3 T T2* (Z = 2.05, P < 0.05). Sensitivity of 7 T magnetic resonance imaging was influenced by cortical lesion type: 100% for type I (T2), 11% for type II (FLAIR/T2), 32% for type III (T2*), and 68% for type IV (T2). We conclude that ultra-high field 7 T magnetic resonance imaging more than doubles detection of cortical multiple sclerosis lesions, compared to 3 T magnetic resonance imaging. Unfortunately, (subpial) cortical pathology remains more extensive than 7 T magnetic resonance imaging can reveal.
Background
Amide proton transfer (APT) imaging is a chemical exchange saturation transfer (CEST) technique offering potential clinical applications such as diagnosis, characterization, and treatment ...planning and monitoring in glioma patients. While APT‐CEST has demonstrated high potential, reproducibility remains underexplored.
Purpose
To investigate whether cerebral APT‐CEST with clinically feasible scan time is reproducible in healthy tissue and glioma for clinical use at 3 T.
Study Type
Prospective, longitudinal.
Subjects
Twenty‐one healthy volunteers (11 females; mean age ± SD: 39 ± 11 years) and 6 glioma patients (3 females; 50 ± 17 years: 4 glioblastomas, 1 oligodendroglioma, 1 radiologically suspected low‐grade glioma).
Field Strength/Sequence
3 T, Turbo Spin Echo ‐ ampling perfection with application optimized contrasts using different flip angle evolution ‐ chemical exchange saturation transfer (TSE SPACE‐CEST).
Assessment
APT‐CEST measurement reproducibility was assessed within‐session (glioma patients, scan session 1; healthy volunteers scan sessions 1, 2, and 3), between‐sessions (healthy volunteers scan sessions 1 and 2), and between‐days (healthy volunteers, scan sessions 1 and 3). The mean APTCEST values and standard deviation of the within‐subject difference (SDdiff) were calculated in whole tumor enclosed by regions of interest (ROIs) in patients, and eight ROIs in healthy volunteers—whole‐brain, cortical gray matter, putamen, thalami, orbitofrontal gyri, occipital lobes, central brain—and compared.
Statistical Tests
Brown‐Forsythe tests and variance component analysis (VCA) were used to assess the reproducibility of ROIs for the three time intervals. Significance was set at P < 0.003 after Bonferroni correction.
Results
Intratumoral mean APTCEST was significantly higher than APTCEST in healthy‐appearing tissue in patients (0.5 ± 0.46%). The average within‐session, between‐sessions, and between‐days SDdiff of healthy control brains was 0.2% and did not differ significantly with each other (0.76 > P > 0.22). The within‐session SDdiff of whole‐brain was 0.2% in both healthy volunteers and patients, and 0.21% in the segmented tumor. VCA showed that within‐session factors were the most important (60%) for scanning variance.
Data Conclusion
Cerebral APT‐CEST imaging may show good scan–rescan reproducibility in healthy tissue and tumors with clinically feasible scan times at 3 T. Short‐term measurement effects may be the dominant components for reproducibility.
Level of Evidence
2
Technical Efficacy
Stage 2
Purpose To investigate whether multivariate pattern recognition analysis of arterial spin labeling (ASL) perfusion maps can be used for classification and single-subject prediction of patients with ...Alzheimer disease (AD) and mild cognitive impairment (MCI) and subjects with subjective cognitive decline (SCD) after using the W score method to remove confounding effects of sex and age. Materials and Methods Pseudocontinuous 3.0-T ASL images were acquired in 100 patients with probable AD; 60 patients with MCI, of whom 12 remained stable, 12 were converted to a diagnosis of AD, and 36 had no follow-up; 100 subjects with SCD; and 26 healthy control subjects. The AD, MCI, and SCD groups were divided into a sex- and age-matched training set (n = 130) and an independent prediction set (n = 130). Standardized perfusion scores adjusted for age and sex (W scores) were computed per voxel for each participant. Training of a support vector machine classifier was performed with diagnostic status and perfusion maps. Discrimination maps were extracted and used for single-subject classification in the prediction set. Prediction performance was assessed with receiver operating characteristic (ROC) analysis to generate an area under the ROC curve (AUC) and sensitivity and specificity distribution. Results Single-subject diagnosis in the prediction set by using the discrimination maps yielded excellent performance for AD versus SCD (AUC, 0.96; P < .01), good performance for AD versus MCI (AUC, 0.89; P < .01), and poor performance for MCI versus SCD (AUC, 0.63; P = .06). Application of the AD versus SCD discrimination map for prediction of MCI subgroups resulted in good performance for patients with MCI diagnosis converted to AD versus subjects with SCD (AUC, 0.84; P < .01) and fair performance for patients with MCI diagnosis converted to AD versus those with stable MCI (AUC, 0.71; P > .05). Conclusion With automated methods, age- and sex-adjusted ASL perfusion maps can be used to classify and predict diagnosis of AD, conversion of MCI to AD, stable MCI, and SCD with good to excellent accuracy and AUC values.
RSNA, 2016.
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