4D flow MRI in abdominal vessels: prospective comparison of k-t accelerated free breathing acquisition to standard respiratory navigator gated acquisition

Volumetric phase-contrast magnetic resonance imaging with three-dimensional velocity encoding (4D flow MRI) has shown utility as a non-invasive tool to examine altered blood flow in chronic liver disease. Novel 4D flow MRI pulse sequences with spatio-temporal acceleration can mitigate the long acquisition times of standard 4D flow MRI, which are an impediment to clinical adoption. The purpose of our study was to demonstrate feasibility of a free-breathing, spatio-temporal (k-t) accelerated 4D flow MRI acquisition for flow quantification in abdominal vessels and to compare its image quality, flow quantification and inter-observer reproducibility with a standard respiratory navigator-gated 4D flow MRI acquisition. Ten prospectively enrolled patients (M/F: 7/3, mean age = 58y) with suspected portal hypertension underwent both 4D flow MRI acquisitions. The k-t accelerated acquisition was approximately three times faster (3:11 min ± 0:12 min/9:17 min ± 1:41 min, p < 0.001) than the standard respiratory-triggered acquisition. Vessel identification agreement was substantial between acquisitions and observers. Average flow had substantial inter-sequence agreement in the portal vein and aorta (CV < 15%) and poorer agreement in hepatic and splenic arteries (CV = 11-38%). The k-t accelerated acquisition recorded reduced velocities in small arteries and reduced splenic vein flow. Respiratory gating combined with increased acceleration and spatial resolution are needed to improve flow measurements in these vessels

Toward Uniform Implementation Of Parametric Map Digital Imaging And Communication In Medicine Standard In Multisite Quantitative Diffusion Imaging Studies

This paper reports on results of a multisite collaborative project launched by the MRI subgroup of Quantitative Imaging Network to assess current capability and provide future guidelines for generating a standard parametric diffusion map Digital Imaging and Communication in Medicine (DICOM) in clinical trials that utilize quantitative diffusion-weighted imaging (DWI). Participating sites used a multivendor DWI DICOM dataset of a single phantom to generate parametric maps (PMs) of the apparent diffusion coefficient (ADC) based on two models. The results were evaluated for numerical consistency among models and true phantom ADC values, as well as for consistency of metadata with attributes required by the DICOM standards. This analysis identified missing metadata descriptive of the sources for detected numerical discrepancies among ADC models. Instead of the DICOM PM object, all sites stored ADC maps as DICOM MR objects, generally lacking designated attributes and coded terms for quantitative DWI modeling. Source-image reference, model parameters, ADC units and scale, deemed important for numerical consistency, were either missing or stored using nonstandard conventions. Guided by the identified limitations, the DICOM PM standard has been amended to include coded terms for the relevant diffusion models. Open-source software has been developed to support conversion of site-specific formats into the standard representation

Accuracy, repeatability, and interplatform reproducibility of T1 quantification methods used for DCEâ MRI: Results from a multicenter phantom study

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142505/1/mrm26903_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142505/2/mrm26903.pd

Multiparametric FDG-PET/MRI of Hepatocellular Carcinoma: Initial Experience

Purpose. To compare multiparametric (mp)FDG-PET/MRI metrics between hepatocellular carcinoma (HCC) and liver parenchyma and to assess the correlation between mpMRI and FDG-PET standard uptake values (SUVs) in liver parenchyma and HCC. Methods. This prospective, institutional review board-approved study enrolled 15 patients (M/F 12/3; mean age 61 y) with HCC. mpMRI including blood-oxygen-level-dependent (BOLD) MRI, intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI), and dynamic contrast-enhanced-(DCE-) MRI was performed simultaneously with 18F-FDG-PET on a 3T PET/MRI hybrid system. Quantitative BOLD, IVIM and DCE-MRI parameters (Tofts model (TM) and shutter-speed model (SSM)), and PET parameters (SUVmean and SUVmax) were quantified and compared between HCC lesions and liver parenchyma using Wilcoxon signed-rank tests. SUV ratios between HCCs and liver were also calculated (SUVmean T/L and SUVmax T/L). Diagnostic performance of (combined) mp-PET/MRI parameters for characterization of HCC was assessed using ROC analysis. Spearman correlations between PET and mpMRI parameters in HCC tumors and liver parenchyma were evaluated. Results. 21 HCC lesions (mean size 4.0 ± 2.4 cm; range 2–13 cm) were analyzed. HCCs exhibited significantly higher arterial fraction (from DCE-MRI) and lower R2∗ pre-O2 and post-O2 (from BOLD-MRI) versus liver parenchyma (P<0.032). The highest diagnostic performance for differentiation between HCC and liver parenchyma was achieved for combined ART SSM and R2∗ post-O2 (AUC = 0.91). SUVmax showed reasonable performance for differentiation of HCC versus liver (AUC = 0.75). In HCC, DCE-MRI parameters Ktrans (TM and SSM) and ve TM exhibited significant negative correlations with SUVmax T/L (r ranges from −0.624 to −0.566; FDR-adjusted P<0.050). Conclusions. Despite the observed reasonable diagnostic performance of FDG-PET SUVmax for HCC detection and several significant correlations between FDG-PET SUV and DCE-MRI parameters, FDG-PET did not provide clear additional value for HCC characterization compared to mpMRI in this pilot study

Automatic segmentation of subcutaneous mouse tumors by multiparametric MR analysis based on endogenous contrast

\u3cp\u3eObject: Contrast-enhanced T\u3csub\u3e1\u3c/sub\u3e-weighted imaging is usually included in MRI procedures for automatic tumor segmentation. Use of an MR contrast agent may not be appropriate for some applications, however. We assessed the feasability of automatic tumor segmentation by multiparametric cluster analysis that uses intrinsic MRI contrast only. Materials and methods: Multiparametric MRI consisting of quantitative T\u3csub\u3e1\u3c/sub\u3e, T\u3csub\u3e2\u3c/sub\u3e, and apparent diffusion coefficient (ADC) mapping was performed in mice bearing subcutaneous tumors (n = 21). k-means and fuzzy c-means clustering with all possible combinations of MRI parameters, i.e. feature vectors, and 2–7 clusters were performed on the multiparametric data. Clusters associated with tumor tissue were selected on the basis of the relative signal intensity of tumor tissue in T\u3csub\u3e2\u3c/sub\u3e-weighted images. The optimum segmentation method was determined by quantitative comparison of automatic segmentation with manual segmentation performed by three observers. In addition, the automatically segmented tumor volumes from seven separate tumor data sets were quantitatively compared with histology-derived tumor volumes. Results: The highest similarity index between manual and automatic segmentation (SI\u3csub\u3emanual,automatic\u3c/sub\u3e = 0.82 ± 0.06) was observed for k-means clustering with feature vector {T\u3csub\u3e2\u3c/sub\u3e, ADC} and four clusters. A strong linear correlation between automatically and manually segmented tumor volumes (R\u3csup\u3e2\u3c/sup\u3e = 0.99) was observed for this segmentation method. Automatically segmented tumor volumes also correlated strongly with histology-derived tumor volumes (R\u3csup\u3e2\u3c/sup\u3e = 0.96). Conclusion: Automatic segmentation of mouse subcutaneous tumors can be achieved on the basis of endogenous MR contrast only.\u3c/p\u3

13-MI11515-03M

Magnetic resonance imaging data of animal 13-MI11515-03M, acquired with a Bruker 7 T magnet, with ParaVision 5.1 software. Each subfolder contains a ParaVisions study. The name of the subfolder refers to the date of data acquisition. An overview of all animals is provided in 'animal_overview.xlsx'

14-MI11768-01M

Magnetic resonance imaging data of animal 14-MI11768-01M, acquired with a Bruker 7 T magnet, with ParaVision 5.1 software. Each subfolder contains a ParaVisions study. The name of the subfolder refers to the date of data acquisition. An overview of all animals is provided in 'animal_overview.xlsx'

15-MI10230-01M

Magnetic resonance imaging data of animal 15-MI10230-01M, acquired with a Bruker 7 T magnet, with ParaVision 5.1 software. Each subfolder contains a ParaVisions study. The name of the subfolder refers to the date of data acquisition. An overview of all animals is provided in 'animal_overview.xlsx'

14-MI12026-07M

Magnetic resonance imaging data of animal 14-MI12026-07M, acquired with a Bruker 7 T magnet, with ParaVision 5.1 software. Each subfolder contains a ParaVisions study. The name of the subfolder refers to the date of data acquisition. An overview of all animals is provided in 'animal_overview.xlsx'