Intravoxel Incoherent Motion Diffusion-weighted MR Imaging for Monitoring the Therapeutic Efficacy of Interventional Photothermal Therapy with Nanoparticles in Rabbit VX2 Tumors.

To determine whether intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) derived parameters can be associated with tumour stage of oesophageal squamous cell carcinoma (SCC). 60 patients with resectable oesophageal SCC and 20 healthy individuals underwent oesophageal DWI-using multi b-values with a 3.0 T MR system. Pure diffusion coefficient (D), perfusion-related incoherent microcirculation (D*), microvascular volume fraction (f) and apparent diffusion coefficient (ADC) were measured on DWI. Statistical analyses were performed to determine associations of DWI-derived parameters with T-stage. ADC (r = -0.842), D (r = -0.729), D* (r = -0.301) and f (r = -0.817) were negatively correlated with T-stage of oesophageal SCC (all p < 0.01), and the multinominal regression analyses revealed that IVIM-derived parameters including D (p = 0.038; odds ratio <1) and f (p < 0.001; odds ratio <1) were associated with T-stage. The Mann-Whitney U tests with Bonferroni correction showed that D, f and ADC could discriminate oesophageal SCC, especially T1-staged tumour, from normal oesophagus (all p < 0.05) while D* could not (p > 0.05). By receiver operating characteristic analyses, f could be the best indicator for detecting oesophageal SCC with an area under receiver operating characteristic (AUC) of 0.964, especially T1-staged cancer with an AUC of 0.984, and for discriminating T1-stages between T0-1 and T2-3 with an AUC of 0.957, and between T0-2 and T3 with an AUC of 0.945 in comparison with any other DWI-derived parameter. IVIM derived parameters can be associated with T-stage of oesophageal SCC. Advances in knowledge (1) IVIM-derived parameters are negatively correlated with stage of oesophageal SCC. (2) Among IVIM-derived parameters, microvascular volume fraction helps detect and stage oesophageal SCC.

Intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) parameters may reflect perfusion and diffusion changes in hepatic sinusoidal obstruction syndrome (SOS). To investigate the feasibility of IVIM-DWI in the noninvasive assessment of hepatic SOS in an experimental rat model. Animal study. Forty-four rats were administered different doses (90 or 160 mg/kg) of monocrotaline by gavage either 48 or 72 hours before MRI to induce different degrees of hepatic SOS, and another 10 rats served as controls. 3T scanner, IVIM-DWI using nine b values (0-800 sec/mm2 ). Histologically, rats were classified as having none (n = 10), mild (n = 8), moderate (n = 19), or severe SOS (n = 17). The apparent diffusion coefficient (ADC) and IVIM-derived parameters (D: true diffusion coefficient, D*: pseudo-diffusion coefficient, and f: perfusion fraction) of the liver parenchyma were measured. IVIM-DWI parameters were compared according to histologic grades of SOS (none, mild, moderate, and severe), and receiver operating characteristic (ROC) curve analysis was performed to determine the diagnostic accuracy. ADC, D, and f of the liver parenchyma were significantly different according to SOS severity groups (Ps < 0.01) and significantly decreased as SOS severity increased (rho = -0.323, -0.313, and -0.700; P = 0.017, 0.021, and <0.001, respectively). Means of f in none, mild, moderate, and severe SOS were 17.2%, 13.3%, 12.3%, and 11.1%, respectively. Among ADC and IVIM-derived parameters, f provided the highest area under the ROC curves for detecting ≥mild, ≥moderate, and severe SOS (0.991, 0.890, and 0.803, respectively). IVIM-DWI may be useful in the diagnosis and severity assessment of hepatic SOS. 2 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:81-89.

Intravoxel Incoherent Motion Diffusion-weighted MR Imaging for Early Evaluation of the Effect of Radiofrequency Ablation in Rabbit Liver VX2 Tumors

To compare the diffusion parameters of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) between the "reflux" and the "non-reflux" kidneys, and to evaluate the feasibility of using IVIM DWI to predict vesicoureteral reflux (VUR) in children with a urinary tract infection (UTI). Eighty-three kidneys from 57 pediatric patients with a UTI were classified into "reflux" and "non-reflux" groups according to voiding cystourethrography (VCUG) results. The apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (PF) were measured and compared in the renal pelvis of both groups. Four indices (D*/ADC, PF/ADC, D*/D, and PF/D) were calculated and receiver operating characteristic (ROC) curve analyses were performed. VURs were detected on VCUG in 21 kidneys. PF and D* were significantly higher in the "reflux" group than in the "non-reflux" group. The indices were all significantly higher. The PF/D index showed the best diagnostic performance in predicting VUR in children with UTI (Az = 0.864). PF and D* were significantly higher in the "reflux" kidney than in the "non-reflux" kidney. Our new index (PF/D) could prove useful for predicting VUR. • IVIM DWI is both radiation-free and contrast media-free. • IVIM DWI index is easily calculated by combining diffusion parameters. • IVIM DWI may help predict VUR in children with UTI. • PF is significantly higher in the "reflux" than the "non-reflux" kidneys. • A new VUR index, PF/D could prove useful for predicting VUR.

Purpose To evaluate the feasibility of using intravoxel incoherent motion (IVIM) diffusion-weighted imaging with multiple b values for the noninvasive diagnosis of nonalcoholic fatty liver disease (NAFLD). Materials and Methods This study was approved by the institutional animal care and use committee. Twenty-seven 8-week-old rabbits were fed a variety of diets (from a standard diet to a high-fat, high-cholesterol diet) before IVIM diffusion-weighted imaging was performed with seven b values by using a 3-T magnetic resonance (MR) imaging unit. At histologic analysis of the animals, livers were categorized by NAFLD severity as normal, NAFLD, borderline nonalcoholic steatohepatitis (NASH), or NASH. The apparent diffusion coefficient and IVIM-derived parameters including true diffusion coefficient, pseudodiffusion coefficient, and perfusion fraction of the liver parenchyma were measured. Each parameter was correlated with NAFLD severity, and optimal cutoff values were determined by means of receiver operating characteristics analysis. Results Perfusion fraction was significantly lower in rabbits with NAFLD than in those with a normal liver, and it decreased further as severity of NAFLD increased, with medians of 22.2%, 14.8%, 11.3%, and 9.5% in the rabbits in the normal, NAFLD, borderline, and NASH groups, respectively (ρ = -0.83, P < .001). Apparent diffusion coefficient, true diffusion coefficient, and pseudodiffusion coefficient were not significantly different between the NAFLD severity groups. In terms of the diagnostic performance of perfusion fraction, area under the curve values were 0.984 (normal vs NAFLD or more severe disease), 0.959 (NAFLD or less severe vs borderline or more severe disease), and 0.903 (borderline or less severe vs NASH) with optimal cutoff values of 15.2%, 13.2%, and 11.0%, respectively. Conclusion Perfusion fractions extracted from IVIM diffusion-weighted imaging may help in the differentiation of early stage NASH from simple steatosis. © RSNA, 2013.

To evaluate the feasibility of using intravoxel incoherent motion (IVIM) diffusion-weighted imaging with multiple b values for the noninvasive diagnosis of nonalcoholic fatty liver disease (NAFLD). This study was approved by the institutional animal care and use committee. Twenty-seven 8-week-old rabbits were fed a variety of diets (from a standard diet to a high-fat, high-cholesterol diet) before IVIM diffusion-weighted imaging was performed with seven b values by using a 3-T magnetic resonance (MR) imaging unit. At histologic analysis of the animals, livers were categorized by NAFLD severity as normal, NAFLD, borderline nonalcoholic steatohepatitis (NASH), or NASH. The apparent diffusion coefficient and IVIM-derived parameters including true diffusion coefficient, pseudodiffusion coefficient, and perfusion fraction of the liver parenchyma were measured. Each parameter was correlated with NAFLD severity, and optimal cutoff values were determined by means of receiver operating characteristics analysis. Perfusion fraction was significantly lower in rabbits with NAFLD than in those with a normal liver, and it decreased further as severity of NAFLD increased, with medians of 22.2%, 14.8%, 11.3%, and 9.5% in the rabbits in the normal, NAFLD, borderline, and NASH groups, respectively (ρ = -0.83, P < .001). Apparent diffusion coefficient, true diffusion coefficient, and pseudodiffusion coefficient were not significantly different between the NAFLD severity groups. In terms of the diagnostic performance of perfusion fraction, area under the curve values were 0.984 (normal vs NAFLD or more severe disease), 0.959 (NAFLD or less severe vs borderline or more severe disease), and 0.903 (borderline or less severe vs NASH) with optimal cutoff values of 15.2%, 13.2%, and 11.0%, respectively. Perfusion fractions extracted from IVIM diffusion-weighted imaging may help in the differentiation of early stage NASH from simple steatosis.

To evaluate the diagnostic potential of intravoxel incoherent motion (IVIM) DWI for differentiating metastatic and non-metastatic lymph node stations (LNS) in pancreatic ductal adenocarcinoma (PDAC). 59 LNS histologically diagnosed following surgical resection from 15 patients were included. IVIM DWI with 12 b values was added to the standard MRI protocol. Evaluation of parameters was performed pre-operatively and included the apparent diffusion coefficient (ADC), pure diffusion coefficient (D), pseudo-diffusion coefficient (D*) and perfusion fraction (f). Diagnostic performance of ADC, D, D* and f for differentiating between metastatic and non-metastatic LNS was evaluated using ROC analysis. Metastatic LNS had significantly lower D, D*, f and ADC values than the non-metastatic LNS (p< 0.01). The best diagnostic performance was found in D, with an area under the ROC curve of 0.979, while the area under the ROC curve values of D*, f and ADC were 0.867, 0.855 and 0.940, respectively. The optimal cut-off values for distinguishing metastatic and non-metastatic lymph nodes were D = 1.180 × 10-3 mm2/s; D* = 14.750 × 10-3 mm2/s, f = 20.65 %, and ADC = 1.390 × 10-3 mm2/s. IVIM DWI is useful for differentiating between metastatic and non-metastatic LNS in PDAC. • IVIM DWI is feasible for diagnosing LN metastasis in PDAC. • Metastatic LNS has lower D, D*, f, ADC values than non-metastatic LNS. • D-value from IVIM model has best diagnostic performance, followed by ADC value. • D* has the lowest AUC value.

To investigate dynamic characteristics and pathological mechanism of signal in rabbit VX-2 tumor model on diffusion-weighted imaging (DWI) after chemoembolization. Forty New Zealand rabbits were included in the study and forty-seven rabbit VX-2 tumor models were raised by implanting directly and intrahepatically after abdominal cavity opened. Forty VX-2 tumor models from them were divided into four groups. DWI was performed periodically and respectively for each group after chemoembolization. All VX-2 tumor samples of each group were studied by pathology. The distinction of VX-2 tumors on DWI was assessed by their apparent diffusion coefficient (ADC) values. The statistical significance between different time groups, different area groups or different b-value groups was calculated by using SPSS12.0 software. Under b-value of 100 s/mm(2), ADC values were lowest at 16 h after chemoembolization in area of VX-2 tumor periphery, central, and normal liver parenchyma around tumor, but turned to increase with further elongation of chemoembolization treatment. The distinction of ADC between different time groups was significant respectively (F = 7.325, P < 0.001; F = 2.496, P < 0.048; F = 6.856, P < 0.001). Cellular edema in the area of VX-2 tumor periphery or normal liver parenchyma around tumor, increased quickly in sixteen h after chemoembolization but, from the 16th h to the 48th h, cellular edema in the area of normal liver parenchyma around tumor decreased gradually and that in the area of VX-2 tumor periphery decreased lightly at, and then increased continually. After chemoembolization, Cellular necrosis in the area of VX-2 tumor periphery was more significantly high than that before chemoembolization. The areas of dead cells in VX-2 tumors manifested low signal and high ADC value, while the areas of viable cells manifested high signal and low ADC value. DWI is able to detect and differentiate tumor necrotic areas from viable cellular areas before and after chemoembolization. ADC of normal liver parenchyma and VX-2 tumor are influenced by intracellular edema, tissue cellular death and microcirculation disturbance after chemoembolization.

Intravoxel incoherent motion diffusion-weighted magnetic resonance imaging in characterization of axillary lymph nodes: Preliminary animal experience

To investigate prospectively dynamic characteristics of the apparent diffusion coefficient (ADC) on MR diffusion-weighted imaging (DWI) in a rabbit VX-2 tumor model. Forty New Zealand rabbits were included in the study, and 47 rabbit VX-2 tumor models were developed by direct and intrahepatic implantation after opening the abdominal cavities. DWI was carried out periodically and respectively on days 7, 14 and 21 after implantation. The VX-2 tumor samples were studied by pathology. The distinction of VX-2 tumors on DWI was assessed by their ADC values by analysis of variance (ANOVA) using SPSS12.0 software. The ADC values (mean ± SD) × 10(-3) mm(2)/s of 47 VX-2 tumors in the peripheral and central areas were 2.18 ± 0.29, 1.96 ± 0.33, 1.80 ± 0.35, 2.20 ± 0.29, 2.05 ± 0.30 and 1.96 ± 0.48, respectively, on days 7, 14 and 21 after implantation. ADC values of 47 VX-2 tumors in the area of the tumor periphery, center and normal parenchyma were higher when the b-value was 100 s/mm(2) than those when the b-value was 300 s/mm(2) (F = 17.964, p < 0.001; F = 13.986, p < 0.001; F = 128.681, p < 0.001). ADC values in the area of normal liver parenchyma were higher than those in the area of the VX-2 tumor periphery and center when the b-value was 100 or 300 s/mm(2). ADCs of viable tumor cells in VX-2 tumors were lower on DWI than those in the area of normal liver parenchyma around the tumor, and ADCs of dead tumor cells in VX-2 tumors were unequal, including high, equal and low values, but they were higher than in the area of normal liver parenchyma around tumors after dead tumor cells had been liquefied or had become cystic. ADC is correlated with the tumor histology and degree of malignancy, and DWI has potential value for dynamically monitoring tumors and evaluating the degree of malignancy and therapeutic effect.

The purpose of this study is to investigate whether the intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) parameters are different between prostate cancer, benign prostatic hyperplasia (BPH), and healthy peripheral zone (PZ). Detailed diffusion measurements of 26 patients with histologically proven prostate cancer have been made in this retrospective study. Trace IVIM DWI was performed using 10 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, and 1000 s/mm2). Biexponential fits were applied to diffusion decay curves to calculate molecular diffusion coefficient, perfusion-related diffusion coefficient, and perfusion fraction on the basis of the IVIM model. Decay curves were also fit with monoexponential decay functions, and a statistical comparison between mono- and biexponential fits was performed. Paired t tests were performed to evaluate the statistical significance of the parameters of IVIM DWI and apparent diffusion coefficient (ADC) between prostate cancer, BPH, and PZ. The chi-square values of biexponential fits were smaller than those from monoexponential fits in all cases. Biexponential functions provided statistically improved fits over monoexponential functions in 81% of cases. The ADC, molecular diffusion coefficient, and perfusion fraction in prostate cancer were significantly lower than those found in the PZ; however, perfusion fractions in prostate cancer and BPH were not significantly different. There were no significant differences in the prostate cancer, BPH, and PZ for the perfusion-related diffusion coefficient, which had large SDs. IVIM DWI parameters are significantly different between prostate cancer and PZ. IVIM DWI may offer additional information for tissue characterization in the prostate gland.

To evaluate the intravoxel incoherent motion (IVIM) diffusion-weighted (DW) MRI for differentiating between benign and malignant musculoskeletal tumours at 3 T. 65 patients with treatment-naïve musculoskeletal tumours (47 malignant and 23 benign lesions) who underwent 3 T MRI including IVIM DW imaging were included. IVIM-derived parameters included pure diffusion coefficient (D), perfusion related incoherent microcirculation (D*, pseudodiffusion coefficient), and perfusion fraction (f). IVIM parameters and mono-exponential apparent diffusion coefficient (ADC) were retrospectively measured by two independent musculoskeletal radiologists. D and ADC values of malignant tumours (923 ± 360, 965 ± 353 µm2 s-1, respectively) were significantly lower than those of benign tumours (1668 ± 546, 1689 ± 526 µm2 s-1) (p < 0.001). F values of malignant tumours (9.6%) were significantly higher than those of benign tumours (7.2%) (p = 0.021), whereas D* values showed no significant difference (p > 0.05). The area under the receiver operating characteristic (ROC) curve of D, ADC and f were 0.874, 0.880 and 0.671, respectively. Using cut-off values of D and ADC of 1200 µm2 s-1, the sensitivity, specificity and accuracy were 92, 83, 89%, 92, 87 and 90%, respectively. D and ADC may be more accurate and reliable for differentiation of malignant from benign musculoskeletal tumours than f and D* at 3 T IVIM DW imaging. Advances in knowledge: Among IVIM-derived parameters, D is more accurate and reliable in differentiating malignant from benign musculoskeletal tumours than f and D* at 3.0T IVIM DW imaging. There was no significant difference in the diagnostic performance of D and ADC.

Gliomas grading is important for treatment plan; we aimed to investigate the application of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) in gliomas grading, by comparing with the three-dimensional pseudocontinuous arterial spin labeling (3D pCASL). 24 patients (13 high grade gliomas and 11 low grade gliomas) underwent IVIM DWI and 3D pCASL imaging before operation; maps of fast diffusion coefficient (D ∗), slow diffusion coefficient (D), fractional perfusion-related volume (f), and apparent diffusion coefficient (ADC) as well as cerebral blood flow (CBF) were calculated and then coregistered to generate the corresponding parameter values. We found CBF and D ∗ were higher in the high grade gliomas, whereas ADC, D, and f were lower (all P < 0.05). In differentiating the high from low grade gliomas, the maximum areas under the curves (AUC) of D ∗, CBF, and ADC were 0.857, 0.85, and 0.902, respectively. CBF was negatively correlated with f in tumor (r = −0.619, P = 0.001). ADC was positively correlated with D in both tumor and white matter (r = 0.887, P = 0.000 and r = 0.824, P = 0.000, resp.). There was no correlation between CBF and D ∗ in both tumor and white matter (P > 0.05). IVIM DWI showed more efficiency than 3D pCASL but less validity than conventional DWI in differentiating the high from low grade gliomas.

The value of intravoxel incoherent motion diffusion-weighted imaging in predicting perineural invasion for resectable gastric cancer: a prospective study

To compare the value of reduced field-of-view (FOV) intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) and arterial spin labeling (ASL) for assessing renal allograft fibrosis and predicting long-term dysfunction. This prospective study included 175 renal transplant recipients undergoing reduced FOV IVIM DWI, ASL, and biopsies. Renal allograft fibrosis was categorized into ci0, ci1, ci2, and ci3 fibrosis according to biopsy results. A total of 83 participants followed for a median of 39 (IQR, 21-42) months were dichotomized into stable and impaired allograft function groups based on follow-up estimated glomerular filtration rate. Total apparent diffusion coefficient (ADCT), pure diffusion ADC, pseudo-perfusion ADC, perfusion fraction f from IVIM DWI, and renal blood flow (RBF) from ASL were calculated and compared. The area under the receiver operating characteristic curve (AUC) was calculated to assess the diagnostic and predictive performances. RBF was different in ci0 vs ci1 (147.9 ± 46.3 vs 126.0 ± 49.4 ml/min/100 g, p = .02) and ci2 vs ci3 (92.9 ± 46.9 vs 70.8 ± 37.8 ml/min/100 g, p = .03). RBF in the stable group was higher than that in the impaired group (144.73 ± 49.33 vs 102.19 ± 47.58 ml/min/100 g, p < .001). AUCs in distinguishing renal allograft fibrosis and predicting long-term allograft dysfunction for RBF were higher than cortical ADCT (ci0 vs ci1-3, 0.76 vs 0.59, p < .001; ci0-1 vs ci2-3, 0.79 vs 0.68, p = .01; ci0-2 vs ci3, 0.79 vs 0.68, p = .01; 0.76 vs 0.60, p = .04, respectively). Compared to reduced FOV IVIM DWI, ASL was a more promising technique for noninvasively distinguishing renal allograft fibrosis degree and predicting long-term allograft dysfunction. • Compared to total ADC from rFOV IVIM DWI, RBF from ASL can distinguish no fibrosis (ci0) vs mild fibrosis (ci1) (p = .02) and moderate fibrosis (ci2) vs severe fibrosis (ci3) (p = .04). • RBF had superior performance than diffusion parameters in discriminating fibrosis (no fibrosis [ci0] vs fibrosis [ci1-3], mild fibrosis [ci0-1] vs moderate to severe fibrosis [ci2-3], non-severe [ci0-2] vs severe [ci3] fibrosis; AUC = 0.76 vs 0.59, p < .001; 0.79 vs 0.68, p = .01; 0.79 vs 0.68, p = .01). • Compared to reduced FOV IVIM DWI, ASL was a more promising technique for noninvasively predicting long-term allograft dysfunction (AUC = 0.76 vs 0.60, p = .04).