Intravoxel Incoherent Motion Magnetic Resonance Imaging Research Articles

Evaluation parameters between intra-voxel incoherent motion and diffusion-weighted imaging in grading and differentiating histological subtypes of meningioma: A prospective pilot study

PurposeTo prospectively evaluate the usage of intra-voxel incoherent motion (IVIM) magnetic resonance imaging (MRI) parameters in grading and differentiating histological subtypes of meningiomas and in comparing their ability with the traditional diffusion-weighted imaging (DWI) parameter (apparent diffusion coefficient, ADC). MethodsIn this prospective study, 102 participants underwent IVIM MRI and DWI. Traditional DWI and IVIM MRI were performed by using 2 b values (0, 1000s/mm2) and 12 b values (0–3500s/mm2), respectively. Finally, the values of ADC and IVIM parameters were collected from 72 Grade I and 11 Grade II meningiomas. ResultsThe mean ADC values of Grade II and Grade I meningiomas were 0.909±0.268×10−3mm2/s and 0.905±0.194×10−3mm2/s, respectively, p=0.967. The D values were lower in Grade II meningiomas than in Grade I meningiomas (0.459±0.072×10−3mm2/s vs. 0.524±0.030×10−3mm2/s, respectively, p=0.005). In ROC curves, the cut-off D value that separated Grade II meningiomas from Grade I meningiomas was 0.479×10−3mm2/s with a sensitivity of 90.9% and a specificity of 76.7%. The secretory and angiomatous meningiomas had higher IVIM parameters than the other subtypes (all p<0.05). D* was significantly lower in fibrous meningiomas than in other meningiomas (2.783±1.179×10−3mm2/s vs. 5.125±1.918×10−3mm2/s, p<0.001). D, rD and rf values correlated negatively with Ki-67 index while D* and rD* value had positive relation with Ki-67 values. ConclusionIVIM MRI is a promising technique for distinguishing different grades of meningiomas. Different subtypes of meningiomas have different IVIM features, which may help to treatment decision and prognosis evaluation.

Early evaluation of irradiated parotid glands with intravoxel incoherent motion MR imaging: correlation with dynamic contrast-enhanced MR imaging.

BackgroundRadiation-induced parotid damage is one of the most common complications in patients with nasopharyngeal carcinoma (NPC) undergoing radiotherapy (RT). Intravoxel incoherent motion (IVIM) magnetic resonance (MR) imaging has been reported for evaluating irradiated parotid damage. However, the changes of IVIM perfusion-related parameters in irradiated parotid glands have not been confirmed by conventional perfusion measurements obtained from dynamic contrast-enhanced (DCE) MR imaging. The purposes of this study were to monitor radiation-induced parotid damage using IVIM and DCE MR imaging and to investigate the correlations between changes of these MR parameters.MethodsEighteen NPC patients underwent bilateral parotid T1-weighted, IVIM and DCE MR imaging pre-RT (2 weeks before RT) and post-RT (4 weeks after RT). Parotid volume; IVIM MR parameters, including apparent diffusion coefficient (ADC), pure diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f); and DCE MR parameters, including maximum relative enhancement (MRE), time to peak (TTP), Wash in Rate, and the degree of xerostomia were recorded. Correlations of parotid MR parameters with mean radiation dose, atrophy rate and xerostomia degree, as well as the relationships between IVIM and DCE MR parameters, were investigated.ResultsFrom pre-RT to post-RT, all of the IVIM and DCE MR parameters increased significantly (p < 0.001 for ADC, D, f, MRE, Wash in Rate; p = 0.024 for D*; p = 0.037 for TTP). Change rates of ADC, f and MRE were negatively correlated with atrophy rate significantly (all p < 0.05). Significant correlations were observed between the change rates of D* and MRE (r = 0.371, p = 0.026) and between the change rates of D* and TTP (r = 0.396, p = 0.017). The intra- and interobserver reproducibility of IVIM and DCE MR parameters was good to excellent (intraclass correlation coefficient, 0.633–0.983).ConclusionsEarly radiation-induced changes of parotid glands could be evaluated by IVIM and DCE MR imaging. Certain IVIM and DCE MR parameters were correlated significantly.

Intravoxel incoherent motion magnetic resonance imaging for evaluation of the efficacy of concurrent chemoradiotherapy in treatment of cervical cancer

Objective To assess the histological characteristics of cervical cancer using intravoxel incoherent motion magnetic resonance imaging (IVIMMRI) and to investigate the performance of IVIMMRI in evaluation of the efficacy of concurrent chemoradiotherapy in the treatment of intermediate/advanced cervical cancer. Methods Pelvic MRI scans, containing T2WI, IVIM (14 b values, b=0-1 000 s/mm2), and contrast-enhanced T1 scans were performed in 23 patients pathologically diagnosed with intermediate/advanced cervical cancer (stage ≥Ⅱb) before chemoradiotherapy, after two and four weeks of treatment, and at the end of treatment. The IVIMMRI data were processed with the bi-exponential model to generate three parameters, containing pure diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f). Apparent diffusion coefficient (ADC) was obtained using the mono-exponential model. The IVIMMRI parameters were measured at each time point and their dynamics and correlation were analyzed. Results The ADC, D, and f values were significantly higher after complete treatment (0.96×10-3vs. 1.77×10-3 mm2/s, P=0.000; 0.76 ×10-3vs. 1.34±0.12×10-3 mm2/s, P=0.000; 0.14% vs. 0.24%, P=0.012). The above three values significantly increased after two weeks of treatment (all P=0.000) and kept increasing until the end of the treatment. In contrast, the D* value was reduced from the second week to the end of the treatment. Conclusions IVIMMRI can monitor the dynamic functional changes and early tumor responses during chemoradiotherapy for cervical cancer, which holds promise for clinical application. Key words: Intravoxel incoherent motion; Magnetic resonance imaging; Diffusion-weighted imaging; Cervical neoplasms/radiochemotherapy

The Role of Intravoxel Incoherent Motion MRI in Predicting Early Treatment Response to Chemoradiation for Metastatic Lymph Nodes in Nasopharyngeal Carcinoma.

Pilot studies have suggested potential clinical applications for intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in head and neck cancers. This study aimed to characterize metastatic lymph nodes using IVIM MRI, and to evaluate the role of IVIM MRI in the prediction of the early treatment response of lymph node metastasis from nasopharyngeal carcinoma (NPC). A total of 122 patients with metastatic lymph nodes from NPC underwent two MRI examinations, pre-treatment and post-treatment (at 4weeks and at ≥2years from the end of chemoradiotherapy). Treatment response was assessed using the Response Evaluation Criteria in Solid Tumors version 1.1. Differences in the initial IVIM parameters [pure molecular diffusion (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f)] between nodes with a partial response (PR) and a complete response (CR) were analyzed in 102 patients after the exclusion of 20. The initial D*, D, and apparent diffusion coefficient (ADC) did not reveal a significant difference between nodes showing a PR or a CR. The mean initial f value was significantly higher in patients with a PR relative to patients with a CR (p=0.003), and its sensitivity and specificity in predicting treatment response to chemoradiotherapy were 86.7% and 100%, respectively. The present study indicated that the initial f value may be more accurate than the initial D*, D, and ADC in the early prediction of treatment response to chemoradiotherapy for metastatic lymph nodes in patients with NPC.

Intravoxel incoherent motion MRI in differentiation between recurrent carcinoma and postchemoradiation fibrosis of the skull base in patients with nasopharyngeal carcinoma

To determine the capacity of intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in differential diagnosis between recurrent carcinoma and postchemoradiation fibrosis of skull base in patients with nasopharyngeal carcinoma (NPC). Eleven patients with recurrent NPC and 21 patients with postchemoradiation fibrosis in the skull base were enrolled. All the diagnoses were proved by endoscopic biopsy or imaging follow-up. IVIM MRI was performed to obtain quantitative parameters including D (pure diffusion), f (perfusion fraction), and D* (pseudodiffusion). D, f, and D* were compared between two groups; the diagnostic performances of D and f were evaluated using the receiver operating characteristic (ROC) analysis. D and f values were significantly lower in recurrent carcinoma than that in fibrosis (P < 0.001; P = 0.001). No significant difference was found in D* values between recurrent carcinoma and fibrosis (P = 0.229). ROC curve analysis showed that the area under the curve of D and f values were 0.996 and 0.838, respectively. Respective cutoff values with sensitivity, specificity, and accuracy were: D = 1.161 × 10-3 mm2 /s (sensitivity 100.0%, specificity 95.2%, accuracy 96.9%), f = 0.109 (sensitivity 81.8%, specificity 71.4%, accuracy 75.0%). Recurrent NPC and postchemoradiation fibrosis in the skull base have distinctive D and f values. IVIM MRI could be used to differentiate between recurrent carcinoma and postchemoradiation fibrosis in patients with NPC. J. Magn. Reson. Imaging 2016;44:1556-1564.

Use of intravoxel incoherent motion MRI to assess renal fibrosis in a rat model of unilateral ureteral obstruction

To investigate the potential of intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in assessment of renal fibrosis using a rat model of unilateral ureteral obstruction (UUO). Thirty-two UUO rats were created by complete ligation of the left ureter. IVIM was performed on a clinical 3.0T whole-body MRI scanner before the ligation (day 0) and on days 1, 3, 5, and 7 after ligation, and followed by histological analysis to examine α-smooth muscle actin (α-SMA) expression and tubulointerstitial lesion (TIL). IVIM parameters of renal cortex and medulla were measured. Changes in each parameter with time were analyzed and correlated with α-SMA expression level and grades of TIL. The apparent diffusion coefficient (ADC), true diffusion (D), and fractional perfusion (f) values between the cortex and inner medulla and between the cortex and outer medulla were found to be significantly different (P < 0.01). The average ADC, D, D*, and f values of renal cortex, outer medulla, and inner medulla on the UUO side significantly decreased over time (P < 0.05), and negatively correlated with both α-SMA expression level and TIL grades (Spearman Correlation Coefficient r: ADC and α-SMA.805, -0.707, -0.805; ADC and TIL: -0.758, -0.761, -0.810; D and α-SMA: -0.782, -0.486, -0.833; D and TIL: -0.518, -0.504, -0.826; D* and α-SMA: -0.707, -0.605, -0.639; D* and TIL: -0.450, -0.670, -0.701; f and α-SMA: -0.866, -0.872, -0.863; and TIL: -0.870, -0.875, -0.863). IVIM MRI shows great potential in noninvasive assessment of renal fibrosis induced by UUO. J. Magn. Reson. Imaging 2016;44:698-706.

Feasibility study of using intravoxel incoherent motion mri to detect parotid gland abnormalities in early-stage Sjögren syndrome patients.

To determine whether intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) could detect parotid gland abnormalities in Sjögren's syndrome (SS) patients who were not identified by conventional MRI. Ten consecutive patients with clinically proven SS who were not identified by conventional MRI were assessed by IVIM MRI with a 3.0T MRI scanner. Quantitative parameters (tissue diffusivity, D; pseudodiffusion coefficient, D*; perfusion fraction, f) derived from IVIM MRI were compared between the SS group and healthy control group (n = 15). A receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of each significant parameter. Excellent inter- and intrareader agreements were obtained during the measurement of D, f, and D* values (interreader, 0.980, 0.942, and 0.883; intrareader, 0.991, 0.952, and 0.896, respectively). All three parameters of the SS group were significantly higher than those of the healthy group (D, 1.049 ± 0.056 × 10(-3) mm(2) /s vs. 0.976 ± 0.116 × 10(-3) mm(2) /s, P = 0.012; D*, 20.410 ± 1.786 × 10(-3) mm(2) /s vs. 18.764 ± 2.433 × 10(-3) mm(2) /s, P = 0.013; f, 0.207 ± 0.003 vs. 0.182 ± 0.002, P = 0.004). ROC analysis showed that the f value had the best diagnostic performance (AUC, 0.712; Sensitivity, 0.80; Specificity, 0.57; Cutoff value, 0.185) in detecting the parotid gland abnormalities in early SS patients. IVIM MRI detected parotid gland abnormalities in early-stage SS patients. J. Magn. Reson. Imaging 2016;43:1455-1461.

Intravoxel incoherent motion magnetic resonance imaging for diagnosis of cervical cancer and evaluation of response of uterine cervical cancer to radiochemotherapy: A pilot study ⁎

Abstract Objective The aim of this study was to investigate the ability of intravoxel incoherent motion (IVIM) diffusion-weighted magnetic resonance imaging (MRI) to diagnose cervical cancer and to evaluate the response of uterine cervical cancer to radiochemotherapy (CRT). Methods This prospective study was approved by the institutional review board, and informed consent was obtained from all patients. A total of 23 patients with primary cervical cancer who were undergoing CRT and 16 age-matched healthy subjects were prospectively recruited for IVIM (b = 0-800 s/mm2) and standard pelvic MRI. Bi-exponential analysis was performed to derive f (perfusion fraction), D⁎ (pseudo-diffusion coefficient), and D (true molecular diffusion coefficient) in cervical cancer (n = 23) and the normal cervix (n = 16). The apparent diffusion coefficient (standard ADC) was calculated. The independent-samples t-test and paired-samples t-test were used for comparisons. Results Pre-treatment cervical cancer had the lowest standard ADC (1.15 ± 0.13 × 10-3 mm2/s) and D (0.89 ± 0.10 × 10-3 mm2/s) values, and these were significantly different from the normal cervix and posttreatment cervical cancer (P = 0.00). The f (16.67 ± 5.85%) was lowest in pre-treatment cervical cancer and was significantly different from the normal cervix and post-treatment cervical cancer (p = 0.012 and 0.00, respectively). No difference was observed in D⁎. Conclusion IVIM is potentially promising for differentiating between the normal cervix and cervical cancer because pre-treated cervical cancer has low perfusion and diffusion IVIM characteristics. Further, the standard ADC, D, and f of cervical cancer showed a tendency to normalize after CRT; thus, IVIM may be useful for monitoring the response to CRT in cervical cancer.

Intravoxel Incoherent Motion-Magnetic Resonance Imaging as an Early Predictor of Treatment Response to Neoadjuvant Chemotherapy in Locoregionally Advanced Nasopharyngeal Carcinoma

Intravoxel Incoherent Motion-Magnetic Resonance Imaging as an Early Predictor of Treatment Response to Neoadjuvant Chemotherapy in Locoregionally Advanced Nasopharyngeal Carcinoma

Intravoxel Incoherent Motion-Magnetic Resonance Imaging as an Early Predictor of Treatment Response to Neoadjuvant Chemotherapy in Locoregionally Advanced Nasopharyngeal Carcinoma.

The aim of the study was to prospectively evaluate the clinical value of intravoxel incoherent motion (IVIM)-magnetic resonance imaging (MRI) in early predicting the treatment response to neoadjuvant chemotherapy (NAC) for nasopharyngeal carcinoma (NPC).Forty-eight patients with locoregionally advanced NPC were imaged with IVIM-MRI (14 b-factors, 0 – 1000 s/mm2) on a 3.0-T Magnetic resonance system, at the baseline, and repeatedly at the third and 21st day after NAC started. The IVIM-derived parameters (D, pure diffusion coefficient; f, perfusion fraction; and D∗, pseudodiffusion coefficient) were calculated with the Interactive Data Language version 6.3 software. The baseline parameters and their corresponding changes (Δparameter(day)) during NAC were compared using the Student t test or Mann-Whitney U test. Variation analyses of IVIM-derived parameters were tested with intraclass correlation coefficient. Receiver-operating characteristic (ROC) curve analysis was conducted to estimate the best diagnostic accuracy. Statistical analyses were performed on the SPSS 18.0 software, with a 2-tailed probability value, P < 0.05 was considered significant.Among recruited patients, 37 cases were categorized as responders and 11 cases as nonresponders after NAC completed. The intra- and interobserver intraclass correlation coefficient of IVIM-derived parameters were excellent, which ranged from 0.858 to 0.971. Compared with the baseline value, at the third and 21st day, the D value was significantly higher and the D∗ value significantly lower (P < 0.05, P < 0.001, respectively). In contrast, f parameter only changed slightly (P > 0.05). Compared with nonresponders, responders presented a notably lower baseline D value and higher ΔD3, ΔD21, ΔD3∗, ΔD21∗, and Δf21 (P < 0.05), but no significant change in Δf3 was observed (P > 0.1). The receiver-operating characteristic curve analyses indicated that the threshold of baseline D values that best predicted the responders for primary nasopharynx tumors and metastatic lymph nodes were 0.911 × 10−3 mm2/s versus 0.951 × 10−3 mm2/s, and their corresponding area under curve, sensitivity, and specificity were 0.714 versus 0.774, 0.658 versus 0.538, and 0.818 versus 0.944, respectively.IVIM-MRI can potentially early predict the treatment response of NAC for NPC patients. The baseline D value, and early changes in D and D∗ value are better predictors of the chemotherapeutic responsiveness.

Quantitative non-Gaussian diffusion and intravoxel incoherent motion magnetic resonance imaging: differentiation of malignant and benign breast lesions.

The purpose of this study was to explore the potential of non-Gaussian diffusion and perfusion magnetic resonance imaging (MRI) using intravoxel incoherent motion (IVIM) MRI for the diagnosis of breast lesions. This study included 26 women with breast lesions. Diffusion-weighted images were acquired using 16 b values up to 2500 s/mm and analyzed using a kurtosis diffusion model (apparent diffusion coefficient [ADC0] and kurtosis [K]) for the diffusion component and IVIM model (perfusion fraction [fIVIM] and pseudodiffusion coefficient [D*]) for the perfusion component. Diagnostic performance of diffusion and perfusion parameters was evaluated from receiver operating characteristic analyses. The ADC0 in malignant lesions was significantly lower than that in benign lesions and normal tissue (P < 0.001, P < 0.001), whereas K was significantly higher (P < 0.05, P < 0.001), as well as fIVIM (P < 0.05, P < 0.01). No significant difference was found in D*. The receiver operating characteristic analysis gave high area under the curve values for ADC0, K, and fIVIM for distinguishing malignant from benign lesions (0.99, 0.85, and 0.82, respectively). The ADC0 allowed benign tumors to be identified with 100% negative predictive value and malignant tumors with 100% sensitivity. The malignant/benign diagnosis thresholds were 1.4 × 10 mm/s as well as 0.6 and 7%, respectively, for ADC0, K, and fIVIM. With a proper methodological framework, IVIM MRI can provide valuable information on tissue structure and microvasculature beneficial for the diagnosis of breast cancer lesions.

Functional mapping of the human visual cortex with intravoxel incoherent motion MRI.

Functional imaging with intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) is demonstrated. Images were acquired at 3 Tesla using a standard Stejskal-Tanner diffusion-weighted echo-planar imaging sequence with multiple b-values. Cerebro-spinal fluid signal, which is highly incoherent, was suppressed with an inversion recovery preparation pulse. IVIM microvascular perfusion parameters were calculated according to a two-compartment (vascular and non-vascular) diffusion model. The results obtained in 8 healthy human volunteers during visual stimulation are presented. The IVIM blood flow related parameter fD* increased 170% during stimulation in the visual cortex, and 70% in the underlying white matter.

Intravoxel incoherent motion MRI evaluation for the staging of liver fibrosis in a rat model.

To explore the characteristics of intravoxel incoherent motion (IVIM) in various stages of liver fibrosis, and their relationships with fibrotic stages in rats. Fifty rats were given various doses of carbon tetrachloride (CCl4 ) to induce various fibrotic stages in rats; 15 untreated rats served as controls. Diffusion-weighted magnetic resonance imaging (MRI) was performed and eight b-values (0-800 s/mm(2) ) were applied to obtain IVIM parameters (D, pure molecular diffusion; f, perfusion fraction; D*, pseudodiffusion). The stages of liver fibrosis (stages F0-F4) were evaluated histologically using METAVIR scores. Fifty-seven rats (15 controls and 42 with fibrosis) were analyzed by nonparametric methods and receiver operating characteristic curves to determine diagnostic accuracy. Significant differences (P < 0.001) were found between stages (stages F0-F4) by D, f, D*, and apparent diffusion coefficient (ADC). There were inverse correlations between fibrosis stages and D, f, D*, ADC (r = -0.657, r = -0.631, r = -0.711 r = -0.719, respectively). Multivariate analysis showed that the combination models (D, f, D*) were better than the individual parameter (ADC) for the evaluation fibrosis stages (area under the curve [AUC]: 0.821-1.000 vs. AUC: 0.753-0.918) CONCLUSION: IVIM-derived parameters showed significant correlations with stages of liver fibrosis in a rat model.

Association of placental perfusion, as assessed by magnetic resonance imaging and uterine artery Doppler ultrasound, and its relationship to pregnancy outcome

PurposeTo investigate (a) if placental perfusion in the second trimester of pregnancy, measured by two non-invasive magnetic resonance imaging (MRI) techniques, is related to impedance to flow in the uterine arteries, as assessed by Doppler ultrasound; and (b) if these measures are associated with future gestational outcome. MethodsIn 37 singleton pregnancies at 24–29 weeks' gestation, uterine artery pulsatility index (PI) was measured by Doppler ultrasound and placental perfusion was measured by Arterial Spin Labelling (flow-sensitive alternating inversion recovery (FAIR)) and intravoxel incoherent motion (IVIM) echo-planar imaging at 1.5 T in basal, central and placental regions of interest. The values were compared between those delivering small for gestational age (SGA) and appropriate for gestational age (AGA) neonates. ResultsIn 23 pregnancies that resulted in delivery of SGA neonates, compared to the 14 with AGA neonates, the median basal FAIR measure was significantly lower (923.0 vs. 2359.0 arbitrary units; p = 0.003) as were IVIM measures of perfusing fraction (f) in basal, central and whole-placental regions (37.8 vs. 40.7%; p = 0.046; 24.3 vs. 35.1%; p = 0.014 and 27.9% vs. 36.2%; p = 0.001, respectively). In the SGA group, the median uterine artery PI was increased (1.96 vs. 1.03; p = 0.001). There were significant associations between uterine artery PI and placental perfusion assessed by both FAIR and IVIM. ConclusionPregnancies that result in SGA neonates exhibited reduced placental perfusion as assessed by MRI during the second trimester. This measurement was found to be strongly associated with impedance to flow in the uterine arteries. We suggest that FAIR or IVIM MRI examinations may be used to directly and non-invasively determine placental perfusion, and that the measured values are strong indicators of future gestational outcome.

Intravoxel incoherent motion MR imaging: comparison of diffusion and perfusion characteristics between nasopharyngeal carcinoma and post-chemoradiation fibrosis

To compare the intravoxel incoherent motion (IVIM) diffusion and perfusion characteristics of nasopharyngeal carcinoma (NPC) and post-chemoradiation fibrosis to aid in their differentiation. Fifty-three (64 %) patients with newly diagnosed NPC and 30 (36 %) patients with biopsy-proven post-chemoradiation fibrosis were recruited into tumour and fibrosis groups respectively. Diffusion-weighted magnetic resonance (MR) imaging was performed using 13 b values (0-1,000 s/mm(2)). Their respective IVIM parameters (D, pure diffusion; f, perfusion fraction; D, pseudodiffusion coefficient) were obtained. D and f were significantly lower in NPC (D = 0.752 ± 0.194 × 10(-3) mm(2)/s, P <0.001; f = 0.122 ± 0.095, P <0.001) than in fibrosis (D = 1.423 ± 0.364 × 10(-3) mm(2)/s; f = 0.190 ± 0.120); while D was significantly higher in NPC (111.366 ± 65.528 × 10(-3) mm(2)/s, P <0.001) than in fibrosis (77.468 ± 62.168 × 10(-3) mm(2)/s). Respective cut-off values with sensitivity, specificity and accuracy were: D = 1.062 × 10(-3) mm(2)/s (100 %, 100 %, 100 %); f = 0.132 (66.0 %, 100 %, 78.3 %); D = 85.283 × 10(-3) mm(2)/s (100 %, 90.7 %, 96.4 %). NPC and post-chemoradiation fibrosis have distinctive IVIM parameters. IVIM MR imaging is potentially useful in discrimination between NPC and fibrosis. • New MRI techniques offer greater help in the assessment of nasopharyngeal carcinoma. • Tumour and post-chemoradiation fibrosis have distinctive intravoxel incoherent motion diffusion/perfusion parameters. • Non-invasive IVIM MRI may help differentiate between tumour and fibrosis. • Pure diffusion is a robust independent discriminating factor which improves diagnostic confidence.

Intra-voxel incoherent motion MRI in rodent model of diethylnitrosamine-induced liver fibrosis

Rationale and ObjectivesTo compare the apparent diffusion coefficient (ADC) and the perfusion fraction measured by intra-voxel incoherent motion (IVIM) Magnetic Resonance Imaging (MRI) with liver fibrosis degrees in a rodent model. Materials and MethodsAll experiments received approval from our institutional animal care and use committee. Liver fibrosis was induced in 13 rats by oral gavage with diethylnitrosamine; 4 untreated rats with normal livers were used as controls. Diffusion Weighted MRI was performed and 8 gradient factors (0, 50, 100, 150, 200, 300, 400 and 500s/mm2) were acquired. The values of ADC, true diffusion coefficient D and perfusion fraction f were measured based on Li Bihan’s method. The percentage of liver fibrosis was assessed via quantitative analysis of Masson trichrome staining using an average of 30 fields per section. The MRI measurements were compared to the histological fibrotic grade to evaluate the correlation between them. ResultsADC contained the contribution of diffusion and perfusion. The ADC and f values decreased significantly with the increasing fibrosis level (correlation coefficient: ADC: ρ=−0.781, p<0.001; f: ρ=−0.720, p=0.001); but D was poorly correlated with fibrosis level (ρ=−0.502, p=0.040). ConclusionThe hepatic ADC and the perfusion fraction f were significantly correlated with the liver fibrosis level; however, D was not. This might suggest that hepatic perfusion is altered during the progression of hepatic fibrosis.

Effect of mannitol on focal cerebral ischemia evaluated by magnetic resonance imaging.

We have evaluated the effect of mannitol on focal cerebral ischemia using T2-weighted magnetic resonance (MR) imaging and intravoxel incoherent motion (IVIM) MR imaging. The left middle cerebral artery (MCA) was exposed via the transorbital approach in 20 adult cats and occluded just proximal to the origin of the perforating arteries. Seven cats in treatment group received mannitol (0.5 g/kg i.v.) at 0, 6, 12 and 18 hours after MCA occlusion. The other 13 cats received saline and served as controls. Sequential MR coronal images were obtained at 2, 4, 6, and 24 hours after MCA occlusion using a GE Signa (1.5 tesla) system. IVIM MR imaging demonstrated ischemic cerebral injury as a sharply demarcated area at 2 hours after MCA occlusion in control group, while T2-weighted MR imaging failed to show clear evidence of the injury until 2-6 hours. At 24 hours after MCA occlusion, the infarcted area in the mannitol treatment group was 36.9 +/- 7.7% (S.E.M) of the left hemisphere, as compared to 57.3 +/- 5.3% in control group (p < 0.05). Mannitol has beneficial effect on ischemic injury.