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Background Prediction of early progression in glioblastoma may provide an opportunity to personalize treatment. Simplified intravoxel incoherent motion (IVIM) MRI offers quantitative estimates of diffusion and perfusion metrics. We investigated whether these metrics, during chemoradiation, could predict treatment outcome. Methods 38 patients with newly diagnosed IDH-wildtype glioblastoma undergoing 6-week/30-fraction chemoradiation had standardized post-operative MRIs at baseline (radiation planning), and at the 10th and 20th fractions. Non-overlapping T1-enhancing (T1C) and non-enhancing T2-FLAIR hyperintense regions were independently segmented. Apparent diffusion coefficient (ADCT1C, ADCT2-FLAIR) and perfusion fraction (fT1C, fT2-FLAIR) maps were generated with simplified IVIM modelling. Parameters associated with progression before or after 6.9 months (early vs late progression, respectively), overall survival (OS) and progression-free survival (PFS) were investigated. Results Higher ADCT2-FLAIR at baseline [Odds Ratio (OR) = 1.06, 95% CI 1.01–1.15, p = 0.025], lower fT2-FLAIR at fraction 10 (OR = 2.11, 95% CI 1.04–4.27, p = 0.018), and lack of increase in ADCT2-FLAIR at fraction 20 compared to baseline (OR = 1.12, 95% CI 1.02–1.22, p = 0.02) were associated with early progression. Combining ADCT2-FLAIR at baseline, fT2-FLAIR at fraction 10, ECOG and MGMT promoter methylation status significantly improved AUC to 90.3% compared to a model with only ECOG and MGMT promoter methylation status (p = 0.001). Using multivariable analysis, neither IVIM metrics were associated with OS but higher fT2-FLAIR at fraction 10 (HR = 0.72, 95% CI 0.56–0.95, p = 0.018) was associated with longer PFS. Conclusion ADCT2-FLAIR at baseline, its lack of increase from baseline to fraction 20, or fT2-FLAIR at fraction 10 significantly predicted early progression. fT2-FLAIR at fraction 10 was associated with PFS.

PurposeTo determine whether intravoxel incoherent motion (IVIM) parameters correlate with liver regeneration and function recovery after partial hepatectomy (PH) in rats with carbon tetrachloride (CCl4)-induced liver fibrosis.MethodsSixty-two adult Sprague-Dawley rats were divided into the control group and the fibrosis group with CCl4 injection for 8 weeks. At the end of the 8th week, all rats received left lateral lobe liver resection. Within each group, IVIM imaging (n = 10/group) and histologic and biochemical analyses (n = 3/group/time point) were performed pre- and post-PH (on days 1, 2, 3, 5, 7, 14, and 21). Differences in liver IVIM parameters and correlation between IVIM parameters and Ki-67 indices, hepatocyte diameter, alanine transaminase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBil) values were analyzed.ResultsPost-PH, liver true diffusion coefficient (D) values decreased and pseudodiffusion coefficient (D*) and perfusion fraction (PF) values increased, then recovered to pre-PH levels gradually in both fibrosis and control rats. PF in fibrosis group were significantly higher than in controls from 3 to 21 days (P < 0.05). In fibrosis rats, both Ki-67 indices and hepatocyte diameters increased, and a strong correlation was found between PF and Ki-67 indices (r = −0.756; P = 0.03), D* and PF values and ALT, AST, and TBil values (r = −0.762 to −0.905; P < 0.05). In control rats, only hepatocyte diameters increased, and all IVIM parameters correlated well with hepatocyte diameters, ALT, AST and TBil values (r = 0.810 to −1.000; P < 0.05).ConclusionThe regeneration pattern in fibrotic liver tissue was different compared with control livers. IVIM parameters can monitor liver regeneration and functional recovery non-invasively after PH.

The intravoxel incoherent motion (IVIM) model allows to map diffusion (D) and perfusion-related parameters (F and D*). Parameter estimation is, however, error-prone due to the non-linearity of the signal model, the limited signal-to-noise ratio (SNR) and the small volume fraction of perfusion in the in-vivo brain. In the present work, the performance of Bayesian inference was examined in the presence of brain pathologies characterized by hypo- and hyperperfusion. In particular, a hierarchical and a spatial prior were combined. Performance was compared relative to conventional segmented least squares regression, hierarchical prior only (non-segmented and segmented data likelihoods) and a deep learning approach. Realistic numerical brain IVIM simulations were conducted to assess errors relative to ground truth. In-vivo, data of 11 central nervous system cancer patients and 9 patients with acute stroke were acquired. The proposed method yielded reduced error in simulations for both the cancer and acute stroke scenarios compared to other methods across the whole investigated SNR range. The contrast-to-noise ratio of the proposed method was better or on par compared to the other techniques in-vivo. The proposed Bayesian approach hence improves IVIM parameter estimation in brain cancer and acute stroke., Medical Image Analysis, 73, ISSN:1361-8415, ISSN:1361-8423

Introduction Cerebral small vessel disease (cSVD) is associated with microvascular and parenchymal alterations. Intravoxel incoherent motion (IVIM) MRI has been proposed to simultaneously measure both the microvascular perfusion and parenchymal diffusivity. This study aimed to evaluate the application of IVIM in cSVD to assess the microvasculature and parenchymal microstructure. Methods Seventy-three patients with cSVD (age 70 ± 11 y) and thirty-nine controls (age 69 ± 12 y) underwent IVIM imaging (3T). Group differences of the perfusion volume fraction f and the parenchymal diffusivity D were investigated using multivariable linear regression accounted for age, sex and cardiovascular factors. To examine the relation between the IVIM measures and the disease severity on structural MRI, white matter hyperintensity (WMH) load served as surrogate measure of the disease severity. Results Patients had a larger f (p, Highlights • The application of IVIM in cSVD was investigated. • IVIM shows a predicted microstructure impairment in cSVD. • Unexpected increased perfusion volume fraction is observed using IVIM. • Perfusion volume fraction and parenchymal diffusivity increase with disease severity. • IVIM imaging may provide a potential surrogate marker for the progression of cSVD.

Background: Differentiation of high-grade gliomas (HGGs) and low-grade gliomas (LGGs) is an important clinical problem because treatment strategies vary greatly. This study was performed to investigate the potential diagnostic value of incoherent intravoxel motion imaging (IVIM) to distinguish HGG from LGG by meta-analysis. Methods: A computerized search of the literature was performed using the free-access PubMed database, Web of Science, and Chinese biomedical database, and relevant articles until September 18, 2018 that used IVIM to distinguish HGG from LGG were included. All analyses were performed using Review Manager 5.3 and Stata. Mean difference (MD) at 95% confidence interval (CI) of the apparent diffusion coefficient (ADC), diffusion coefficient value (D), perfusion fraction value (f), and perfusion coefficient value (D∗) were summarized. Results: Nine studies were used for general data pooling. In the tumor parenchyma (TP) regions, subgroup analysis revealed D∗ in HGG is higher than in LGG (MD = 1.19, P = .002), and D in HGG is lower than in LGG (MD = −1.06, P = .001). However, no significant difference in f (MD = 0.89, P = .056) was detected between HGG and LGG. In the white matter regions, HGG had higher D∗ (MD = 0.76, P = .04) compared with LGG, while no marked differences between the D value (P = .07) and f (P = .09) values. Conclusion: The present meta-analysis shows that the ADC, D, and D∗ values derived from IVIM may be useful in differentiating HGG from LGG. Considering the small sample of this study, we need to be cautious when interpreting the results of this study. Other prospective and large-sample randomized controlled trials were needed to establish the value of IVIM in differentiating HGG from LGG.

Background Intravoxel incoherent motion magnetic resonance imaging (IVIM) enables non-invasive measurement of brain perfusion. Purpose To investigate whether IVIM could be used to evaluate the hemodynamic disturbance of Moyamoya disease (MMD) by comparison with the gold-standard 15O-gas positron emission tomography (PET) method. Material and Methods Ten consecutive patients with MMD (six women; mean age = 42.8 years) and 10 age-matched healthy controls were evaluated by diffusion-weighted images with 12 different b values in the range of 0–900 s/mm2 and 15O-gas PET. Tomographic maps of IVIM parameters, perfusion fraction (f ), pseudo-diffusion coefficient (D*), and f・D*, as well as cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) maps obtained with PET, were normalized and hemispheric gray and white matter values were calculated. IVIM parametric values were compared with PET parameters and with clinically assessed disease severity. Results There was significant correlation between D* and MTT (r = –0.74, P

Diagnosing diffuse liver disease first involves measurement of blood enzymes followed by biopsy. However, blood markers lack spatial and diagnostic specificity and biopsy is highly risky and variable. Although structural changes have been evaluated using diffusion weighted imaging (DWI), the technique is minimally quantitative. Quantitative MR diffusion approaches, such as intra-voxel incoherent motion (IVIM) and diffusion tensor imaging (DTI) have been proposed to better characterize diseased liver. However, the so called pseudo-hepatic artefact due to cardiac motion, drastically affects DWI results. The overall goals of this thesis were thus to evaluate the pseudo-hepatic anisotropy artefact on the quality of diffusion tensor (DT) and IVIM metrics, and to identify potential solutions. Intra- and intersession DTI repeatability was evaluated in healthy human livers when varying the number of diffusion encoding gradients (NGD) and number of signal averages (NSA). Although no further advantage was observed with increasing NGD beyond 6 directions, increased NSA improved intra- and inter-session repeatability. The pseudo-hepatic artefact resulted in increased fractional anisotropy (FA) and tensor eigenvalues (λ1, λ2, λ3), most prominent in the left liver lobe during systole of the cardiac cycle. Without taking advantage of tensor directional information, increasing the acquired NGD slightly improved IVIM fit quality thus helping to minimize the pseudo-hepatic artefact. Combining IVIM and DTI resulted in FA values closer to the hypothesized value of 0.0, which, based on liver microstructure is most logical. Although both IVIM-DTI and DTI-IVIM exhibited similar fit R2 values, the latter failed more often, especially near major blood vessels. Thus, IVIM-DTI was concluded to be more robust and thus the better approach. Thesis Doctor of Philosophy (PhD)