Impact of Field Strength and Respiratory Motion Control on Diffusion-Weighted MR Imaging of the Liver (original) (raw)
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Error model for reduction of cardiac and respiratory motion effects in quantitative liver DW-MRI
Magnetic Resonance in Medicine, 2012
Diffusion-weighted images of the liver exhibit signal dropout from cardiac and respiratory motion, particularly in the left lobe. These artifacts cause bias and variance in derived parameters that quantify intra-voxel incoherent motion (IVIM). Many models of diffusion have been proposed, but few separate attenuation from diffusion or perfusion from that of bulk motion. The error model proposed here (Beta*LogNormal) is intended to accomplish that separation by modeling stochastic attenuation from bulk motion as multiplication by a Beta-distributed random variate. Maximum likelihood estimation with this error model can be used to derive IVIM parameters separate from signal dropout, and does not require a priori specification of parameters to do so. Liver IVIM parameters were derived for six healthy subjects under this error model and compared with leastsquares estimates. Least-squares estimates exhibited bias due to cardiac and respiratory gating and due to location within the liver. Bias from these factors was significantly reduced under the Beta*LogNormal model, as was within-organ parameter variance. Similar effects were appreciable in diffusivity maps in two patients with focal liver lesions. These results suggest that, relative to least-squares estimation, the Beta*LogNormal model accomplishes the intended reduction of bias and variance from bulk motion in liver diffusion imaging.
American Journal of Roentgenology, 2009
iffusion-weighted MRI (DWI) of the abdomen has seen significant improvements since the earliest reports more than two decades ago [1]. Several publications have endorsed its usefulness for the detection and characterization of focal hepatic lesions [2-13], for assessing treatment response [14-16], and for the evaluation of diffuse liver diseases [17]. Unfortunately, DWI is yet to find a place in routine MRI of the liver, partly because the sequence lacks standardization [18]. DWI for liver imaging is typically a spinecho acquisition with motion-probing gradients on either side of the 180° refocusing pulse, followed by a single-shot echoplanar imaging readout. Unequivocal evidence supports the use of parallel imaging for liver DWI [19]; however, the same is not true for some other imaging parameters. DWI
MRI-based Estimation of Liver Function by Intravoxel Incoherent Motion Diffusion-weighted Imaging
Magnetic resonance imaging, 2016
To explore the usefulness of intravoxel incoherent motion (IVIM) to evaluate the hepatic functional reserve as expressed by the model for Child-Pugh class.. IVIM diffusion-weighted imaging (DWI) using 10 different b values were performed on a Philips 3.0T MR scanner in 70 patients with liver cirrhosis and 60 healthy volunteers as the control group. Patients with liver cirrhosis were subdivided into three groups: Child-Pugh class A: 29 cases; Child-Pugh class B: 19 cases; Child-Pugh class C: 22 cases. Pure molecular diffusion (D), pseudo-diffusion (D*), perfusion fraction (f) and apparent diffusion coefficient (ADC) values were calculated, and used to determine liver function, as indicated by the Child-Pugh class. The ICC values of D, D*, f and ADC between two radiologists were 0.997, 0.986, 0.985 and 0.995, respectively. D*, f and ADC values of liver cirrhosis group were significantly lower than control group (P<0.001, P = 0.016, P = 0.042, respectively). D*, f and ADC values sig...
Journal of the Korean Society of Radiology
To compare the image quality and stability of apparent diffusion coefficient (ADC) in diffusion-weighted MRI (DWI) of the upper abdomen among the breath-hold (BH), free-breathing (FB) and respiratory-triggered (RT) techniques. Materials and Methods: We analyzed the qualitative and quantitative parameters of 204 consecutive patients who underwent DWI (BH-DWI, FB-DWI or RT-DWI; n=68 in each technique). Qualitative parameters included liver contour, vascular landmarks, intra-slice homogeneity, and inter-slice discontinuity on DWI with a b-factor of 800 s/mm 2 and a four-grade scale. Quantitative parameters included inter-slice or intraslice inhomogeneity of ADC in the spleen. Results: RT-DWI showed better liver contour compared to BH-DWI (p <0.001) or FB-DWI (p = 0.001). As for the quality of the vascular landmarks, BH-DWI was inferior to FB-DWI (p = 0.025) and RT-DWI (p < 0.001). FB-DWI had the poorest result (p <0.001) for inter-slice discontinuity compared to the other techniques. FB-DWI showed significantly larger inter-slice differences between the highest and the lowest ADCs in the spleen compared with those of RT-DWI (p < 0.001). Intra-slice homogeneity was significantly better in RT-DWI and FB-DWI than in BH-DWI (p < 0.001). Conclusion: Compared with BH or FB techniques, RT-DWI appears to result in the best imaging by providing better anatomic detail without skipping continuous slices, in addition to more homogeneous ADCs.
Liver Cirrhosis: Intravoxel Incoherent Motion MR Imaging—Pilot Study
Radiology, 2008
To retrospectively evaluate a respiratory-triggered diffusion-weighted (DW) magnetic resonance (MR) imaging sequence combined with parallel acquisition to allow the calculation of pure molecular-based (D) and perfusionrelated (D*, f) diffusion parameters, on the basis of the intravoxel incoherent motion (IVIM) theory, to determine if these parameters differ between patients with cirrhosis and patients without liver fibrosis. Materials and Methods: The institutional review board approved this retrospective study; informed consent was waived. IVIM DW imaging was tested on three alkane phantoms, on which the signalintensity decay curves according to b factors were logarithmically plotted. Ten b factors (0, 10, 20, 30, 50, 80, 100, 200, 400, 800 sec/mm 2) were used in patients. Patients with documented liver cirrhosis (cirrhotic liver group, n ϭ 12) and patients without chronic liver disease (healthy liver group, n ϭ 25) were included. The mean liver D, D*, and f values were measured and compared with the apparent diffusion coefficient (ADC) computed by using four b values (0, 200, 400, 800 sec/mm 2). Liver ADC and D, f, and D* parameters were compared between the cirrhotic liver group and healthy liver group. Means were compared by using the Student t test. Results: Signal-intensity decay curves were monoexponential on phantoms and biexponential in patients. In vivo, mean ADC values were significantly higher than D in the healthy liver group (ADC ϭ 1.39 ϫ 10 Ϫ3 mm 2 /sec Ϯ 0.2 [standard deviation] vs D ϭ 1.10 ϫ 10 Ϫ3 mm 2 /sec Ϯ 0.7) and in the cirrhotic liver group (ADC ϭ 1.23 ϫ 10 Ϫ3 mm 2 /sec Ϯ 0.4 vs D ϭ 1.19 ϫ 10 Ϫ3 mm 2 /sec Ϯ 0.5) (P ϭ .03). ADC and D* were significantly reduced in the cirrhotic liver group compared with those in the healthy liver group (respective P values of .03 and .008). Conclusion: Restricted diffusion observed in patients with cirrhosis may be related to D* variations, which reflect decreased perfusion, as well as alterations in pure molecular water diffusion in cirrhotic livers.
Whole-liver diffusion-weighted MRI histogram analysis
European Journal of Gastroenterology & Hepatology, 2015
To explore whether whole-liver diffusion-weighted MRI analysis (of the apparently normal liver parenchyma) can help differentiate between patients with colorectal liver metastasis and controls without liver disease. Ten patients with colorectal liver metastasis and 10 controls with no focal/diffuse liver disease underwent liver MRI at 1.5 T including diffusion-weighted imaging (DWI; b-values 0, 50, 100, 500, 750, 1000). Apparent diffusion coefficient (ADC) maps were calculated from the DWI images to carry out quantitative diffusion analyses. An experienced reader performed segmentation of the apparently nondiseased liver (excluding metastases/focal liver lesions) on the ADC maps. Histogram ADC parameters were calculated and compared between the patients and the controls. The mean liver ADC was 0.95×10 mm/s for the patients versus 1.03×10 mm/s for the controls (P=0.42). The fifth percentile of the ADC was significantly lower for the patients compared with the controls (0.45 vs. 0.69 10 mm/s, P=0.01). The SD was significantly higher in the patient group (0.30 vs. 0.22, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). Median, skewness, kurtosis, and 30th-95th percentile were not significantly different between the two groups. Areas under the receiver operator characteristics curves to differentiate patients with metastatic liver involvement from healthy controls without liver disease were 0.79 for the fifth percentile and 0.95 for the SD. Whole-liver diffusion-weighted MRI histogram analysis showed a significant shift towards lower fifth percentile ADC values and higher SD in patients with colorectal liver metastasis compared with controls without liver disease.
Diffusion-Weighted MR Imaging of Focal Liver Lesions in the Left and Right Lobes
Academic Radiology, 2013
Rationale and Objectives: To determine possible differences between the left and right hepatic lobes in apparent diffusion coefficient (ADC) values of benign and malignant focal liver lesions (FLLs) and normal liver parenchyma. Materials and Methods: Thirty-six patients (16 males, 20 females; mean age 56.8 years) with FLLs of the same etiology in both the left and right hepatic lobes (13 patients with 26 benign FLLs and 23 patients with 46 malignant FLLs) who underwent 1.5T magnetic resonance imaging (MRI) including diffusion-weighted MRI (b values: 0 and 800 seconds/mm) with respiratory gating and without cardiac gating were included in this Health Insurance Portability and Accountability Act-compliant and institutional review board-approved study. ADC values of normal liver parenchyma and FLLs in each hepatic lobe were calculated and compared by using Student's t-test and Wilcoxon signed-rank test, respectively.
Simultaneous Multislice Accelerated Free-Breathing Diffusion-Weighted Imaging of the Liver at 3T
Abdominal Imaging, 2015
Purpose: To perform image quality comparison between accelerated multiband diffusion acquisition (mb2-DWI) and conventional diffusion acquisition (c-DWI) in patients undergoing clinically indicated liver MRI. Methods: In this prospective study 22 consecutive patients undergoing clinically indicated liver MRI on a 3-T scanner equipped to perform multiband diffusionweighed imaging (mb-DWI) were included. DWI was performed with single-shot spin-echo echo-planar technique with fat-suppression in free breathing with matching parameters when possible using c-DWI, mb-DWI, and multiband DWI with a twofold acceleration (mb2-DWI). These diffusion sequences were compared with respect to various parameters of image quality, lesion detectability, and liver ADC measurements. Results: Accelerated mb2-DWI was 40.9% faster than c-DWI (88 vs. 149 s). Various image quality parameter scores were similar or higher on mb2-DWI when compared to c-DWI. The overall image quality score (averaged over the three readers) was significantly higher for mb-2 compared to c-DWI for b = 0 s/mm 2 (3.48 ± 0.52 vs. 3.21 ± 0.54; p = 0.001) and for b = 800 s/mm 2 (3.24 ± 0.76 vs. 3.06 ± 0.86; p = 0.010). Total of 25 hepatic lesions were visible on mb2-DWI and c-DWI, with identical lesion detectability. There was no significant difference in liver ADC between mb2-DWI and c-DWI (p = 0.12). Bland-Altman plot demonstrates lower mean liver ADC with mb2-DWI compared to c-DWI (by 0.043 9 10-3 mm 2 /s or 3.7% of the average ADC). Conclusion: Multiband technique can be used to increase acquisition speed nearly twofold for free-breathing DWI of the liver with similar or improved overall image quality and similar lesion detectability compared to conventional DWI.