| 1. |
- Chougar, Lydia, et al.
(författare)
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Signal Intensity within Cerebral Venous Sinuses on Synthetic MRI
- 2020
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Ingår i: MAGNETIC RESONANCE IN MEDICAL SCIENCES. - : JPN SOC MAGNETIC RESONANCE MEDICINE. - 1347-3182 .- 1880-2206. ; 19:1, s. 56-63
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Flowing blood sometimes appears bright on synthetic T-1-weighted images, which could be misdiagnosed as a thrombus. This study aimed to investigate the frequency of hyperintensity within cerebral venous sinuses on synthetic MR images and to evaluate the influence of increasing flow rates on signal intensity using a flow phantom. Materials and Methods: Imaging data, including synthetic and conventional MRI scans, from 22 patients were retrospectively analyzed. Signal intensities at eight locations of cerebral venous sinuses on synthetic images were graded using the following three-point scale: 0, "dark vessel"; 1, "hyperintensity within the walls"; and 2, "hyperintensity within the lumen:" A phantom with gadolinium solution inside a U-shaped tube was acquired without flow and then with increasing flow rates (60, 100, 200, 300, 400 ml/min). Results: Considering all sinus locations, the venous signal intensity on synthetic T-1-weighted images was graded as 2 in 79.8% of the patients. On synthetic T-2-weighted images, all sinuses were graded as 0. On fluid-attenuated inversion recovery (FLAIR) images, sinuses were almost always graded as 0 (99.4%). In the phantom study, the signal initially became brighter on synthetic T-1-weighted images as the flow rate increased. Above a certain flow rate, the signal started to decrease. Conclusion: High signal intensity within the cerebral venous sinuses is a frequent finding on synthetic T-1-weighted images. This corresponds to the hyperintensity noted at certain flow rates in the phantom experiment.
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| 2. |
- Fujita, Shohei, et al.
(författare)
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Cross-vendor multiparametric mapping of the human brain using 3D-QALAS: A multicenter and multivendor study
- 2024
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Ingår i: Magnetic Resonance in Medicine. - : WILEY. - 0740-3194 .- 1522-2594.
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate a vendor-agnostic multiparametric mapping scheme based on 3D quantification using an interleaved Look-Locker acquisition sequence with a T2 preparation pulse (3D-QALAS) for whole-brain T1, T2, and proton density (PD) mapping.Methods: This prospective, multi-institutional study was conducted between September 2021 and February 2022 using five different 3T systems from four prominent MRI vendors. The accuracy of this technique was evaluated using a standardized MRI system phantom. Intra-scanner repeatability and inter-vendor reproducibility of T1, T2, and PD values were evaluated in 10 healthy volunteers (6 men; mean age +/- SD, 28.0 +/- 5.6 y) who underwent scan-rescan sessions on each scanner (total scans = 100). To evaluate the feasibility of 3D-QALAS, nine patients with multiple sclerosis (nine women; mean age +/- SD, 48.2 +/- 11.5 y) underwent imaging examination on two 3T MRI systems from different manufacturers.Results: Quantitative maps obtained with 3D-QALAS showed high linearity (R2 = 0.998 and 0.998 for T1 and T2, respectively) with respect to reference measurements. The mean intra-scanner coefficients of variation for each scanner and structure ranged from 0.4% to 2.6%. The mean structure-wise test-retest repeatabilities were 1.6%, 1.1%, and 0.7% for T1, T2, and PD, respectively. Overall, high inter-vendor reproducibility was observed for all parameter maps and all structure measurements, including white matter lesions in patients with multiple sclerosis.Conclusion: The vendor-agnostic multiparametric mapping technique 3D-QALAS provided reproducible measurements of T1, T2, and PD for human tissues within a typical physiological range using 3T scanners from four different MRI manufacturers.
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| 3. |
- Hagiwara, Akifumi, et al.
(författare)
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Incidence, molecular characteristics, and imaging features of "clinically-defined pseudoprogression" in newly diagnosed glioblastoma treated with chemoradiation
- 2022
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Ingår i: Journal of Neuro-Oncology. - : Springer. - 0167-594X .- 1573-7373. ; 159, s. 509-518
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Pseudoprogression (PsP) remains an elusive and clinically important, yet ill-defined, phenomena that, generally, involves a period of early radiographic progression (enhancement) followed by a period of radiographic stability or regression. In the current study, we utilized data from the control arm of a phase III clinical trial in newly-diagnosed glioblastoma to explore imaging characteristics of “clinically-defined PsP”, or early radiographic progression (PFS < 6 months from chemoradiation) followed by a long post-progression residual overall survival (ROS > 12 months).Methods: One hundred sixty-nine patients with newly-diagnosed GBM from the control arm of the AVAglio trial (NCT00943826) who presented with early radiographic progressive disease (PD) (< 6 months) were included. Clinical characteristics, topographical patterns, and radiomic features were compared between newly-diagnosed GBM exhibiting early PD and early death (< 12-month ROS, “true PD”) with those exhibiting early PD and a long residual survival (> 12-month ROS, “clinically-defined PsP”).Results: “Clinically-defined PsP” occurred to 38.5% of patients with early PD, and was more associated with MGMT methylation (P = 0.02), younger age (P = 0.003), better neurological performance (P = 0.01), and lower contrast-enhancing tumor volume (P = 0.002) at baseline. GBM showing “true PD” occurred more frequently in the right internal capsule, thalamus, lentiform nucleus, and temporal lobe than those with “clinical PsP”. Radiomic analysis predicted “clinical PsP” with > 70% accuracy on the validation dataset.Conclusion: Patients with early PD that eventually exhibit “clinically-defined PsP” have distinct clinical, molecular, and MRI characteristics. This information may be useful for treating clinicians to better understand the potential risks and outcome in patients exhibiting early radiographic changes following chemoradiation.
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| 4. |
- Hagiwara, Akifumi, et al.
(författare)
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Myelin Measurement : Comparison Between Simultaneous Tissue Relaxometry, Magnetization Transfer Saturation Index, and T1w/T2w Ratio Methods
- 2018
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Magnetization transfer (MT) imaging has been widely used for estimating myelin content in the brain. Recently, two other approaches, namely simultaneous tissue relaxometry of R1 and R2 relaxation rates and proton density (SyMRI) and the ratio of T1-weighted to T2-weighted images (T1w/T2w ratio), were also proposed as methods for measuring myelin. SyMRI and MT imaging have been reported to correlate well with actual myelin by histology. However, for T1w/T2w ratio, such evidence is limited. In 20 healthy adults, we examined the correlation between these three methods, using MT saturation index (MTsat) for MT imaging. After calibration, white matter (WM) to gray matter (GM) contrast was the highest for SyMRI among these three metrics. Even though SyMRI and MTsat showed strong correlation in the WM (r?=?0.72), only weak correlation was found between T1w/T2w and SyMRI (r?=?0.45) or MTsat (r?=?0.38) (correlation coefficients significantly different from each other, with p values?amp;lt;?0.001). In subcortical and cortical GM, these measurements showed moderate to strong correlations to each other (r?=?0.54 to 0.78). In conclusion, the high correlation between SyMRI and MTsat indicates that both methods are similarly suited to measure myelin in the WM, whereas T1w/T2w ratio may be less optimal.
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| 5. |
- Hagiwara, Akifumi, et al.
(författare)
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SyMRI of the Brain : Rapid Quantification of Relaxation Rates and Proton Density, With Synthetic MRI, Automatic Brain Segmentation, and Myelin Measurement
- 2017
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Ingår i: Investigative Radiology. - : Lippincott Williams & Wilkins. - 0020-9996 .- 1536-0210. ; 52:10, s. 647-657
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Forskningsöversikt (refereegranskat)abstract
- Conventional magnetic resonance images are usually evaluated using the image signal contrast between tissues and not based on their absolute signal intensities. Quantification of tissue parameters, such as relaxation rates and proton density, would provide an absolute scale; however, these methods have mainly been performed in a research setting. The development of rapid quantification, with scan times in the order of 6 minutes for full head coverage, has provided the prerequisites for clinical use. The aim of this review article was to introduce a specific quantification method and synthesis of contrast-weighted images based on the acquired absolute values, and to present automatic segmentation of brain tissues and measurement of myelin based on the quantitative values, along with application of these techniques to various brain diseases. The entire technique is referred to as "SyMRI" in this review. SyMRI has shown promising results in previous studies when used for multiple sclerosis, brain metastases, Sturge-Weber syndrome, idiopathic normal pressure hydrocephalus, meningitis, and postmortem imaging.
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| 6. |
- Johansson, Erik, et al.
(författare)
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Exogenous introduction of tissue inhibitor of metalloproteinase 2 reduces accelerated growth of TGF-β-disrupted diffuse-type gastric carcinoma.
- 2010
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Ingår i: Cancer science. - : Wiley. - 1349-7006 .- 1347-9032. ; 101:11, s. 2398-403
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Tidskriftsartikel (refereegranskat)abstract
- Diffuse-type gastric carcinoma is characterized by rapid progression and poor prognosis. High expression of transforming growth factor (TGF)-β and thick stromal fibrosis are observed in this type of gastric carcinoma. We have previously shown that disruption of TGF-β signaling via introduction of a dominant negative form of the TGF-β type II receptor (dnTβRII) into diffuse-type gastric cancer cell lines, including OCUM-2MLN, caused accelerated tumor growth through induction of tumor angiogenesis in vivo. In the present study, we show that TGF-β induces upregulation of expression of tissue inhibitor of metalloproteinase 2 (TIMP2) in the OCUM-2MLN cell line in vitro, and that expression of TIMP2 is repressed by dnTβRII expression in vivo. Transplantation of the OCUM-2MLN cells to nude mice exhibited accelerated tumor growth in response to dnTβRII expression, which was completely abolished when TIMP2 was coexpressed with dnTβRII. Although the blood vessel density of TIMP2-expressing tumors was only slightly decreased, the degree of hypoxia in tumor tissues was significantly increased and pericytes covering tumor vasculature were decreased by TIMP2 expression in OCUM-2MLN cells, suggesting that the function of tumor vasculatures was repressed by TIMP2 and consequently tumor growth was reduced. These findings provide evidence that one of the mechanisms of the increase in angiogenesis in diffuse-type gastric carcinoma is the downregulation of the anti-angiogenic protein TIMP2.
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