Background
Magnetic Resonance Spin TomogrAphy in Time‐domain (MR‐STAT) can reconstruct whole‐brain multi‐parametric quantitative maps (eg, T1, T2) from a 5‐minute MR acquisition. These quantitative ...maps can be leveraged for synthetization of clinical image contrasts.
Purpose
The objective was to assess image quality and overall diagnostic accuracy of synthetic MR‐STAT contrasts compared to conventional contrast‐weighted images.
Study Type
Prospective cross‐sectional clinical trial.
Population
Fifty participants with a median age of 45 years (range: 21–79 years) consisting of 10 healthy participants and 40 patients with neurological diseases (brain tumor, epilepsy, multiple sclerosis or stroke).
Field Strength/Sequence
3T/Conventional contrast‐weighted imaging (T1/T2 weighted, proton density PD weighted, and fluid‐attenuated inversion recovery FLAIR) and a MR‐STAT acquisition (2D Cartesian spoiled gradient echo with varying flip angle preceded by a non‐selective inversion pulse).
Assessment
Quantitative T1, T2, and PD maps were computed from the MR‐STAT acquisition, from which synthetic contrasts were generated. Three neuroradiologists blinded for image type and disease randomly and independently evaluated synthetic and conventional datasets for image quality and diagnostic accuracy, which was assessed by comparison with the clinically confirmed diagnosis.
Statistical Tests
Image quality and consequent acceptability for diagnostic use was assessed with a McNemar's test (one‐sided α = 0.025). Wilcoxon signed rank test with a one‐sided α = 0.025 and a margin of Δ = 0.5 on the 5‐level Likert scale was used to assess non‐inferiority.
Results
All data sets were similar in acceptability for diagnostic use (≥3 Likert‐scale) between techniques (T1w:P = 0.105, PDw:P = 1.000, FLAIR:P = 0.564). However, only the synthetic MR‐STAT T2 weighted images were significantly non‐inferior to their conventional counterpart; all other synthetic datasets were inferior (T1w:P = 0.260, PDw:P = 1.000, FLAIR:P = 1.000). Moreover, true positive/negative rates were similar between techniques (conventional: 88%, MR‐STAT: 84%).
Data Conclusion
MR‐STAT is a quantitative technique that may provide radiologists with clinically useful synthetic contrast images within substantially reduced scan time.
Evidence Level: 1
Technical Efficacy: Stage 2
Stroke and related cerebrovascular diseases are a major cause of mortality and disability. Even at standard-field-strengths (1.5T), MRI is by far the most sensitive imaging technique to detect acute ...brain infarctions and to characterize incidental cerebrovascular lesions, such as white matter hyperintensities, lacunes and microbleeds. Arterial time-of-flight (TOF) MR angiography (MRA) can depict luminal narrowing or occlusion of the major brain feeding arteries, and this without the need for contrast administration. Compared to 1.5T MRA, the use of high-field strength (3T) and even more so ultra-high-field strengths (7T), enables the visualization of the lumen of much smaller intracranial vessels, while adding a contrast agent to TOF MRA at 7T may enable the visualization of even more distal arteries in addition to veins and venules. Moreover, with 3T and 7T, the arterial vessel walls beyond the circle of Willis become visible with high-resolution vessel wall imaging. In addition, with 7T MRI, the brain parenchyma can now be visualized on a submillimeter scale. As a result, high-resolution imaging studies of the brain and its blood supply at 7T have generated new concepts of different cerebrovascular diseases. In the current article, we will discuss emerging clinical applications and future directions of vascular imaging in the brain at 7T MRI.
Carotid atherosclerotic plaque rupture and its sequelae are among the leading causes of acute ischemic stroke. The risk of rupture and subsequent thrombosis is, among others, determined by vulnerable ...plaque characteristics and linked to activation of the immune system, in which neutrophil extracellular traps (NETs) potentially play a role. The aim of this study was to investigate how plaque vulnerability is associated with NETs levels. We included 182 patients from the Plaque At RISK (PARISK) study in whom carotid imaging was performed to measure plaque ulceration, fibrous cap integrity, intraplaque hemorrhage, lipid-rich necrotic core, calcifications and plaque volume. Principal component analysis generated a 'vulnerability index' comprising all plaque characteristics. Levels of the NETs marker myeloperoxidase-DNA complex were measured in patient plasma. The association between the vulnerability index and low or high NETs levels (dependent variable) was assessed by logistic regression. No significant association between the vulnerability index and NETs levels was detected in the total population (odds ratio 1.28, 95% confidence interval 0.90-1.83, p = 0.18). However, in the subgroup of patients naive to statins or antithrombotic medication prior to the index event, this association was statistically significant (odds ratio 2.08, 95% confidence interval 1.04-4.17, p = 0.04). Further analyses revealed that this positive association was mainly driven by intraplaque hemorrhage, lipid-rich necrotic core and ulceration. In conclusion, plaque vulnerability is positively associated with plasma levels of NETs, but only in patients naive to statins or antithrombotic medication prior to the index event.
Purpose
CXCR4 (over)expression is found in multiple human cancer types, while expression is low or absent in healthy tissue. In glioblastoma it is associated with a poor prognosis and more extensive ...infiltrative phenotype. CXCR4 can be targeted by the diagnostic PET agent
68
GaGa-Pentixafor and its therapeutic counterpart
177
LuLu-Pentixather. We aimed to investigate the expression of CXCR4 in glioblastoma tissue to further examine the potential of these PET agents.
Methods
CXCR4 mRNA expression was examined using the R2 genomics platform. Glioblastoma tissue cores were stained for CXCR4. CXCR4 staining in tumor cells was scored. Stained tissue components (cytoplasm and/or nuclei of the tumor cells and blood vessels) were documented. Clinical characteristics and information on IDH and
MGMT
promoter methylation status were collected. Seven pilot patients with recurrent glioblastoma underwent
68
GaGa-Pentixafor PET; residual resected tissue was stained for CXCR4.
Results
Two large mRNA datasets (
N
= 284;
N
= 540) were assesed. Of the 191 glioblastomas, 426 cores were analyzed using immunohistochemistry. Seventy-eight cores (23 tumors) were CXCR4 negative, while 18 cores (5 tumors) had both strong and extensive staining. The remaining 330 cores (163 tumors) showed a large inter- and intra-tumor variation for CXCR4 expression; also seen in the resected tissue of the seven pilot patients—not directly translatable to
68
GaGa-Pentixafor PET results. Both mRNA and immunohistochemical analysis showed CXCR4 negative normal brain tissue and no significant correlation between CXCR4 expression and IDH or
MGMT
status or survival.
Conclusion
Using immunohistochemistry, high CXCR4 expression was found in a subset of glioblastomas as well as a large inter- and intra-tumor variation. Caution should be exercised in directly translating ex vivo CXCR4 expression to PET agent uptake. However, when high CXCR4 expression can be identified with
68
GaGa-Pentixafor, these patients might be good candidates for targeted radionuclide therapy with
177
LuLu-Pentixather in the future.
We present a fully automated method for carotid artery (CA) outer wall segmentation in black blood MRI using partially annotated data and compare it to the state-of-the-art reference model. Our model ...was trained and tested on multicentric data of patients (106 and 23 patients, respectively) with a carotid plaque and was validated on different MR sequences (24 patients) as well as data that were acquired with MRI systems of a different vendor (34 patients). A 3D nnU-Net was trained on pre-contrast T1w turbo spin echo (TSE) MR images. A CA centerline sliding window approach was chosen to refine the nnU-Net segmentation using an additionally trained 2D U-Net to increase agreement with manual annotations. To improve segmentation performance in areas with semantically and visually challenging voxels, Monte-Carlo dropout was used. To increase generalizability, data were augmented with intensity transformations. Our method achieves state-of-the-art results yielding a Dice similarity coefficient (DSC) of 91.7% (interquartile range (IQR) 3.3%) and volumetric intraclass correlation (ICC) with ground truth of 0.90 on the development domain data and a DSC of 91.1% (IQR 7.2%) and volumetric ICC with ground truth of 0.83 on the external domain data outperforming top-ranked methods for open-source CA segmentation. The uncertainty-based approach increases the interpretability of the proposed method by providing an uncertainty map together with the segmentation.
Clinical applications of 7 T MRI in the brain van der Kolk, Anja G; Hendrikse, Jeroen; Zwanenburg, Jaco J.M ...
European journal of radiology,
05/2013, Letnik:
82, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Abstract This review illustrates current applications and possible future directions of 7 Tesla (7 T) Magnetic Resonance Imaging (MRI) in the field of brain MRI, in clinical studies as well as ...clinical practice. With its higher signal-to-noise (SNR) and contrast-to-noise ratio (CNR) compared to lower field strengths, high resolution, contrast-rich images can be obtained of diverse pathologies, like multiple sclerosis (MS), brain tumours, aging-related changes and cerebrovascular diseases. In some of these diseases, additional pathophysiological information can be gained compared to lower field strengths. Because of clear depiction of small anatomical details, and higher lesion conspicuousness, earlier diagnosis and start of treatment of brain diseases may become possible. Furthermore, additional insight into the pathogenesis of brain diseases obtained with 7 T MRI could be the basis for new treatment developments. However, imaging at high field comes with several limitations, like inhomogeneous transmit fields, a higher specific absorption rate (SAR) and, currently, extensive contraindications for patient scanning. Future studies will be aimed at assessing the advantages and disadvantages of 7 T MRI over lower field strengths in light of clinical applications, specifically the additional diagnostic and prognostic value of 7 T MRI.
Background and purpose
Dolichoarteriopathies of the extracranial part of the internal carotid artery (ICA) are associated with cerebrovascular events, yet information on their prevalence and risk ...factors remains limited. The aim of the present study therefore was to study the prevalence and risk factors of dolichoarteriopathies in a sample of patients with cerebrovascular symptoms from the Plaque At RISK (PARISK) study.
Methods
In a random sample of 100 patients from the PARISK study, multidetector computed tomography angiography (MDCTA) was performed as part of clinical workup. On MDCTA, we evaluated the extracranial trajectory of the ICA by measuring the length (in millimeters), the tortuosity index (TI; defined as the ICA length divided by the shortest possible distance from bifurcation to skull base), and dolichoarteriopathy type (tortuosity, coiling or kinking). Next, we investigated the association between cardiovascular risk factors and these measurements using linear and logistic regression analyses.
Results
The mean (standard deviation) length of the ICA was 93 (± 14) mm, with a median (interquartile range) TI of 1.2 (1.1–1.3). The overall prevalence of dolichoarteriopathies was 69%, with tortuosity being the most common (72%), followed by coiling (20%), and kinking (8%). We found that age and obesity were associated with a higher TI: difference per 10‐year increase in age: 0.05 (95% confidence interval CI 0.02–0.08) and 0.16 (95% CI 0.07–0.25) for obesity. Obesity and hypercholesterolemia were associated with a more severe type of dolichoarteriopathy (odds ratio OR 2.07 95% CI 1.04–4.12 and OR 2.17 95% CI 1.02–4.63, respectively).
Conclusion
Dolichoarteriopathies in the extracranial ICA are common in patients with cerebrovascular symptoms, and age, obesity and hypercholesterolemia may play an important role in the pathophysiology of these abnormalities.
We investigated the prevalence of internal carotid artery dolichoarteriopathies using quantitative measurements and traditional visual rating in a random sample of patients with cerebrovascular symptoms who underwent multidetector computed tomography angiography. Tortuosity was the most common type of dolichoarteriopathy (72%), followed by coiling (20%), and kinking (8%). Age, obesity, and hypercholesterolemia were significantly associated with a more severe type of dolichoarteriopathy and/or tortuosity index. Therefore, these cardiovascular risk factors may play an important role in the pathophysiology of these abnormalities.
Purpose
There is a continuous search for imaging techniques with high sensitivity and specificity for brain tumors. Positron emission tomography (PET) imaging has shown promise, though many PET ...agents either have a low tumor specificity or impractical physical half-lives.
124
ICLR1404 is a small molecule alkylphosphocholine analogue that is thought to bind to plasma membrane lipid rafts and has shown high tumor-to-background ratios (TBR) in a previous pilot study in brain tumor patients. This study attempts to define the clinical value of
124
ICLR1404 PET/CT (aka CLR124).
Procedures
Adult patients with new or suspected recurrence of high-grade primary or metastatic brain tumors (
N
= 27) were injected with
124
ICLR1404 followed by PET/CT at 6, 24, and 48 h. Standard uptake values (SUV) and TBR values were calculated for all time points. Uptake of
124
ICLR1404 was qualitatively assessed, compared with magnetic resonance imaging (MRI), and correlated with clinical outcome. Final diagnosis (
N
= 25) was established based on surgically resected tissue or long-term follow-up.
Results
Positive uptake with high TBR was detected in all but one patient with a final diagnosis of primary/recurrent brain tumor (12/13) and in less than half of patients with treatment-related changes (5/12). Concordance between
124
ICLR1404 uptake and contrast enhancement on MRI was seen in < 40 %, with no concordance between T
2
-hyperintensities and uptake. No significant difference in overall outcome was found between patients with and without
124
ICLR1404 uptake.
Conclusions
The uptake pattern in these patients suggests a very high sensitivity of
124
ICLR1404 PET/CT for diagnosing tumor tissue; however, tumor specificity needs to be further defined. Relative lack of concordance with standard MRI characteristics suggests that
124
ICLR1404 PET/CT provides additional information about brain tumors compared to MRI alone, potentially improving clinical decision-making.
Different studies already demonstrated the benefits of 7T for precontrast TOF-MRA in the visualization of intracranial small vessels. The aim of this study was to assess the performance of ...high-resolution 7T TOF-MRA after the administration of a gadolinium-based contrast agent in visualizing intracranial perforating arteries.
Ten consecutive patients (7 male; mean age, 50.4 ± 9.9 years) who received TOF-MRA at 7T after contrast administration were retrospectively included in this study. Intracranial perforating arteries, branching from the parent arteries of the circle of Willis, were identified on all TOF-MRA images. Provided a TOF-MRA before contrast administration was present, a direct comparison between pre- and postcontrast TOF-MRA was made.
It was possible to visualize intracranial perforating arteries branching off from the entire circle of Willis, and their proximal branches. The posterior cerebral artery (P1 and proximal segment of P2) appeared to have the largest number of visible perforating branches (mean of 5.1 in each patient, with a range of 2-7). The basilar artery and middle cerebral artery (M1 and proximal segment M2) followed with a mean number of 5.0 and 3.5 visible perforating branches (range of 1-9 and 1-8, respectively). Venous contamination in the postcontrast scans sometimes made it difficult to discern the arterial or venous nature of a vessel.
High-resolution postcontrast TOF-MRA at 7T was able to visualize multiple intracranial perforators branching off from various parts of the circle of Willis and proximal intracranial arteries. Although confirmation in a larger study is needed, the administration of a contrast agent for high-resolution TOF-MRA at 7T seems to enable a better visualization of the distal segment of certain intracranial perforators.
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