Pseudo-diffusion Coefficient Research Articles

Ultrahigh b-values MRI in normal human prostate: Initial research on reproducibility and age-related differences.

To investigate the reproducibility of diffusion-weighted imaging (DWI) with ultrahigh b-values, and analyze the age-related differences in normal prostates. In all, 67 healthy participants were divided into three age groups (group A, 15-30 years; group B, 31-50 years; group C, ≥51 years), and underwent DWI scanning twice with 15 b-factors from 0 to 3000 at 3.0T. Triexponential fits were applied to calculate the molecular diffusion coefficient (D), the pseudo-diffusion coefficient (D*), the ultrahigh apparent diffusion coefficient (ADCuh ), and perfusion fraction (f). The interobserver and short-term interscan reproducibility were evaluated, and the change in these parameters with age were assessed. The D, ADCuh , and f values presented good to excellent reproducibility. With increasing age, a trend of increasing D values was observed, with significant difference in both peripheral zone (PZ, P = 0.01) and central gland (CG, P = 0.01) of normal prostate tissue. The f value increased in the CG beginning at 50 years of age while the ADCuh value decreased in the PZ after 50 years of age; all of them showed significant differences between groups A and C and groups B and C (P = 0.01/0.01). The D, ADCuh , and f values have good to excellent reproducibility in the normal prostate, and these values change with age. The ultrahigh b-values magnetic resonance imaging (MRI) can provide additional information (ADCuh ), which is different from the IVIM (intravoxel incoherent motion)-derived parameters. 1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:801-812.

Intravoxel incoherent motion diffusion-weighted magnetic resonance imaging of focal vertebral bone marrow lesions: initial experience of the differentiation of nodular hyperplastic hematopoietic bone marrow from malignant lesions.

To evaluate the ability of intravoxel incoherent motion (IVIM) diffusion-weighted magnetic resonance imaging (MRI) parameters to differentiate nodular hyperplastic hematopoietic bone marrow (HHBM) from malignant vertebral bone marrow lesions (VBMLs). A total of 33 patients with 58 VBMLs, including 9 nodular HHBM lesions, 39 bone metastases, and 10 myelomas, were retrospectively assessed. All diagnoses were confirmed either pathologically or via image assessment. IVIM diffusion-weighted MRI with 11 b values (from 0 to 800s/mm2) were obtained using a 3.0-T MR imager. The apparent diffusion coefficient (ADC), pure diffusion coefficient (D), perfusion fraction (f), and pseudodiffusion coefficient (D*) were calculated. ADC and IVIM parameters were compared using the Mann-Whitney U test. Receiver operating characteristic (ROC) curve analysis was performed to assess the diagnostic performances of ADC, D, f, and D* in terms of VBML characterization. The diagnostic performance of morphological MR sequences was also assessed for comparison. The ADC and D values of nodular HHBM were significantly lower than those of malignant VBML (both p values < 0.001), whereas the f value was significantly higher (p < 0.001). However, there were no significant differences in D* between the two groups (p = 0.688). On ROC analysis, the area under the curve (AUC) for D was 1.000, which was significantly larger than that for ADC (AUC = 0.902). Intravoxel incoherent motion diffusion-weighted MRI can be used to differentiate between nodular HHBM and malignant VBML. The D value was significantly lower for nodular HHBM, and afforded a better diagnostic performance than the ADC, f, and D* values in terms of such differentiation.

Correlations between intravoxel incoherent motion (IVIM) parameters and histological findings in rectal cancer: preliminary results.

Our purpose was to correlate different intravoxel incoherent motion (IVIM), histopathological and clinical parameters in rectal cancer. 17 patients with histologically proven rectal cancer investigated on a 3.T device were included into the study. DWI was performed using a multi-slice single-shot echo-planar imaging sequence with b values of 0, 50, 200, 500 and 1000 s/mm.2 A polygonal region of interest was drawn within the tumors on every b image. The following parameters were retrieved from IVIM: apparent diffusion coefficient (ADC), true diffusion (D), pseudo diffusion coefficient (D*), perfusion factor (f), and relative perfusion f·D*. In every case, cell count, nucleic areas, proliferation index KI 67, and microvessel density were estimated on histopathological specimens. Pearson's correlation coefficient was used to analyze the association between the parameters. ADC correlated well with KI 67 index and D tended to correlate with cell count and KI 67. ADC and D tended to correlate with total nucleic area. The perfusion factor f correlated well with stained vessel area, total vessel area, and vessel count. D* and fD* correlated with mean vessel diameter. Distant metastasized tumors had higher D* and fD* values. IVIM parameter reflected different clinical and histopathological features in rectal cancer.

Intravoxel incoherent motion diffusion-weighted MR imaging in assessing and characterizing solitary pulmonary lesions

This study aimed to investigate the potential of intravoxel incoherent motion (IVIM) diffusion-weighted MR imaging in assessing solitary pulmonary lesions (SPLs). Sixty-two patients with pathologically confirmed SPLs, including 51 and 11 cases of malignant and benign lesions, respectively, were assessed. Diffusion weighted imaging (DWI) with 13 b values was used to derive apparent diffusion coefficient (ADC) and IVIM parameters, including true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f). Our results showed that, there was an excellent inter-observer agreement on the measurements of D and ADC between observers (inter-class correlation coefficient, ICC = 0.902 and 0.884, respectively). Meanwhile, f and D* showed good and substantial reproducibility (ICC = 0.787 and 0.623, respectively). D and ADC of malignant lesions were significantly lower than those of benign lesions (both P ≤ 0.001), while similar values were obtained in both groups for D* and f (both P > 0.05). In receiver operating characteristic (ROC) analysis, D showed the highest area under curve (AUC) for distinguishing malignant from benign lesions, followed by ADC. Accompanying signs of SPLs have specific features on IVIM maps. In conclusion, IVIM provides functional information in characterizing SPLs which is helpful to differential diagnosis. D and ADC have a significantly higher diagnostic value than f and D*.

Can diffusion-weighted imaging serve as a biomarker of fibrosis in pancreatic adenocarcinoma?

To assess the relationship between diffusion-weighted imaging (DWI) and intravoxel incoherent motion (IVIM)-derived quantitative parameters (apparent diffusion coefficient [ADC], perfusion fraction [f], Dslow , diffusion coefficient [D], and Dfast , pseudodiffusion coefficient [D*]) and histopathology in pancreatic adenocarcinoma (PAC). Subjects with suspected surgically resectable PAC were prospectively enrolled in this Health Insurance Portability and Accountability Act (HIPAA)-compliant, Institutional Review Board-approved study. Imaging was performed at 1.5T with a respiratory-triggered echo planar DWI sequence using 10 b values. Two readers drew regions of interest (ROIs) over the tumor and adjacent nontumoral tissue. Monoexponential and biexponential fits were used to derive ADC2b , ADCall , f, D, and D*, which were compared to quantitative histopathology of fibrosis, mean vascular density, and cellularity. Two biexponential IVIM models were investigated and compared: 1) nonlinear least-square fitting based on the Levenberg-Marquardt algorithm, and 2) linear fit using a fixed D* (20 mm2 /s). Statistical analysis included Student's t-test, Pearson correlation (P < 0.05 was considered significant), intraclass correlation, and coefficients of variance. Twenty subjects with PAC were included in the final cohort. Negative correlation between D and fibrosis (Reader 2: r = -0.57 P = 0.01; pooled P = -0.46, P = 0.04) was observed with a trend toward positive correlation between f and fibrosis (r = 0.44, P = 0.05). ADC2b was significantly lower in PAC with dense fibrosis than with loose fibrosis ADC2b (P = 0.03). Inter- and intrareader agreement was excellent for ADC, D, and f. In PAC, D negatively correlates with fibrosis, with a trend toward positive correlation with f suggesting both perfusion and diffusion effects contribute to stromal desmoplasia. ADC2b is significantly lower in tumors with dense fibrosis and may serve as a biomarker of fibrosis architecture. 1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:393-402.

Intravoxel incoherent motion (IVIM) analysis of vertebral bone marrow changes after radiation exposure from diagnostic imaging and interventional procedures.

Background High cumulative radiation dose in cancer patients warrants systemic examination of possible changes in bone marrow. Purpose To assess retrospectively changes in vertebral bone marrow diffusion and perfusion using intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) in hepatocellular carcinoma (HCC) patients after exposure to radiation from diagnostic imaging and interventional procedures. Material and Methods A total of 21 IVIM-DWI sets in 20 HCC patients, consisting of baseline and follow-up liver magnetic resonance imaging (MRI) with an interval less than 100 days, were reviewed after varying levels of radiation exposure from transarterial chemoembolization (TACE), multiphase liver CT, and abdominal radiography. IVIM parameters (apparent diffusion coefficient [ADC], true diffusion coefficient [D], pseudodiffusion coefficient [D*], and perfusion fraction [PF]) of vertebral bone marrow were analyzed for significant differences between baseline and follow-up MRI using Wilcoxon signed-rank test, and for correlations with cumulative effective dose, as well as time interval between last radiation exposure and follow-up MRI using Spearman's correlation. Results Compared to baseline MRI, ADC, D*, and PF significantly decreased on follow-up MRI (ADC: median [interquartile range], 0.405 × 103 mm2/s [0.364-0.477] versus 0.390 [0.348-0.461]; D*: 24.011 [18.141-29.584] versus 20.815 [15.022-28.347]; PF: 10.960% [8.828-12.985] versus 9.125 [8.606-12.803]) ( P < 0.05). There was no significant difference in D ( P = 0.807). Cumulative effective dose was moderately correlated with decrease in D* (r = 0.434). In addition, longer intervals between last exposure and follow-up MRI showed negative correlations with changes in D and ADC (r = -0.352 and -0.333, respectively). Conclusion Vertebral bone marrow diffusion and perfusion parameters were significantly changed after exposure to medical radiation.

Lung adenocarcinoma: Assessment of epidermal growth factor receptor mutation status based on extended models of diffusion-weighted image.

To evaluate the diagnostic performance of extended models of diffusion-weighted (DW) imaging to help differentiate the epidermal growth factor receptor (EGFR) mutation status in stage IIIA-IV lung adenocarcinoma. This retrospective study had institutional research board approval and was HIPAA compliant. Preoperative extended DW imaging including intravoxel incoherent motion (IVIM) and diffusional kurtosis imaging (DKI) 3 Tesla MRI were retrospectively evaluated in 53 patients with pathologically confirmed non-early stage (IIIA-IV) lung adenocarcinoma. EGFR mutationsat exons 18-21 were determined by using polymerase chain reaction-based ARMS. Quantitative parameters (mean, kurtosis, skewness, 10th and 90th percentiles) of IVIM (true-diffusion coefficient D, pseudo-diffusion coefficient D*, and perfusion fraction f) and DKI (kurtosis value Kapp, kurtosis corrected diffusion coefficient Dapp) were calculated by outlining entire-volume histogram analysis. Receiver operating characteristic analysis was constructed to determine the diagnostic performance of each parameter. Multivariate logistic regression was used to differentiate the probability of EGFR mutation status. Twenty-four of 53 patients with lung adenocarcinoma were EGFR mutations, which occurred most often in acinar (10 of 13 [76.9%]) and papillary predominant tumors (9 of 13 [69.2%]). Patients with EGFR mutation showed significant higher 10th percentile of D, lower D* value in terms of kurtosis, and lower Kapp value in terms of mean, skewness, 10th and 90th percentiles (all P values < 0.05). The 90th Kapp showed significantly higher sensitivity (97%; P < 0.05) and Az (0.817; P < 0.05) value. Multivariate logistic regression showed 90th Kapp was a independent factor for determining EGFR mutation with odds ratio -1.657. Multiple IVIM and DKI parameters, especially the histogram 90th Kapp value, helped differentiate EGFR mutation status in stage IIIA-IV lung adenocarcinoma. 3 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:281-289.

Non-parametric intravoxel incoherent motion analysis of the thyroid gland.

PurposeTo implement a protocol for intravoxel incoherent motion (IVIM) of the thyroid, to determine base parameters in healthy volunteers, and to provide preliminary experience on clinical applicability in one patient.Materials and methodsEight healthy volunteers underwent 3T MRI using a diffusion weighted echo-planar imaging sequence with 12 different b-values between 0–800 s/mm2. The IVIM parameters diffusion coefficient D, pseudo-diffusion coefficient D*, perfusion fraction Fp, and the optimal b-values thresholds were calculated for each thyroid lobe, muscle tissue and the cerebrospinal fluid (CSF) using a non-parametric multi-step algorithm and compared with a Student's t-test. A p-value <0.05 was considered significant.ResultsMean values for healthy thyroid tissue were: D 1.01 ± 0.13 × 10−3 mm2/s, D* 71.0 ± 52.5 × 10−3 mm2/s and Fp 17.1 ± 4.2%; for muscle: D 0.50 ± 0.21 × 10−3 mm2/s, D* 58.3 ± 99.2 × 10−3 mm2/s and Fp 26.5 ± 9.3%; and for CSF D 2.18 ± 0.93 × 10−3 mm2/s, D* 99.2 ± 41.2 × 10−3 mm2/s and Fp 74.6 ± 12.7%. The optimal b-value threshold separating diffusion and perfusion effects in thyroid ranged between 0–70 s/mm2. Healthy thyroid tissue showed similar Fp compared to muscle, both lower than CSF.ConclusionsThe proposed IVIM protocol provides surrogate markers on cellular diffusion restriction and perfusion; thereby providing a more comprehensive description of tissue properties compared to conventional DWI.

Correlation between Intravoxel Incoherent Motion Magnetic Resonance Imaging Derived Metrics and Serum Soluble CD40 Ligand Level in an Embolic Canine Stroke Model.

ObjectiveTo determine the relationship between intravoxel incoherent motion (IVIM) imaging derived quantitative metrics and serum soluble CD40 ligand (sCD40L) level in an embolic canine stroke model.Materials and MethodsA middle cerebral artery occlusion model was established in 24 beagle dogs. Experimental dogs were divided into low- and high-sCD40L group according to serum sCD40L level at 4.5 hours after establishing the model. IVIM imaging was scanned at 4.5 hours after model establishment using 10 b values ranging from 0 to 900 s/mm2. Quantitative metrics diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) of ischemic lesions were calculated. Quantitative metrics of ischemic lesions were normalized by contralateral hemisphere using the following formula: normalized D = Dstroke / Dcontralateral. Differences in IVIM metrics between the low- and high-sCD40L groups were compared using t test. Pearson's correlation analyses were performed to determine the relationship between IVIM metrics and serum sCD40L level.ResultsThe high-sCD40L group showed significantly lower f and normalized f values than the low-sCD40L group (f, p < 0.001; normalized f, p < 0.001). There was no significant difference in D*, normalized D*, D, or normalized D value between the two groups (All p > 0.05). Both f and normalized f values were negatively correlated with serum sCD40L level (f, r = −0.789, p < 0.001; normalized f, r = −0.823, p < 0.001). However, serum sCD40L level had no significant correlation with D*, normalized D*, D, or normalized D (All p > 0.05).ConclusionThe f value derived from IVIM imaging was negatively correlated with serum sCD40L level. f value might serve as a potential imaging biomarker to assess the formation of microvascular thrombosis in hyperacute period of ischemic stroke.

Intravoxel Incoherent Motion Diffusion for Identification of Breast Malignant and Benign Tumors Using Chemometrics.

The aim of the paper is to identify the breast malignant and benign lesions using the features of apparent diffusion coefficient (ADC), perfusion fraction f, pseudodiffusion coefficient D⁎, and true diffusion coefficient D from intravoxel incoherent motion (IVIM). There are 69 malignant cases (including 9 early malignant cases) and 35 benign breast cases who underwent diffusion-weighted MRI at 3.0 T with 8 b-values (0~1000 s/mm2). ADC and IVIM parameters were determined in lesions. The early malignant cases are used as advanced malignant and benign tumors, respectively, so as to assess the effectiveness on the result. A predictive model was constructed using Support Vector Machine Binary Classification (SVMBC, also known Support Vector Machine Discriminant Analysis (SVMDA)) and Partial Least Squares Discriminant Analysis (PLSDA) and compared the difference between them both. The D value and ADC provide accurate identification of malignant lesions with b = 300, if early malignant tumor was considered as advanced malignant (cancer). The classification accuracy is 93.5% for cross-validation using SVMBC with ADC and tissue diffusivity only. The sensitivity and specificity are 100% and 87.0%, respectively, r2cv = 0.8163, and root mean square error of cross-validation (RMSECV) is 0.043. ADC and IVIM provide quantitative measurement of tissue diffusivity for cellularity and are helpful with the method of SVMBC, getting comprehensive and complementary information for differentiation between benign and malignant breast lesions.

Assessment of Cervical Cancer with a Parameter-Free Intravoxel Incoherent Motion Imaging Algorithm.

ObjectiveTo evaluate the feasibility of a parameter-free intravoxel incoherent motion (IVIM) approach in cervical cancer, to assess the optimal b-value threshold, and to preliminarily examine differences in the derived perfusion and diffusion parameters for different histological cancer types.Materials and MethodsAfter Institutional Review Board approval, 19 female patients (mean age, 54 years; age range, 37–78 years) gave consent and were enrolled in this prospective magnetic resonance imaging study. Clinical staging and biopsy results were obtained. Echo-planar diffusion weighted sequences at 13 b-values were acquired at 3 tesla field strength. Single-sliced region-of-interest IVIM analysis with adaptive b-value thresholds was applied to each tumor, yielding the optimal fit and the optimal parameters for pseudodiffusion (D*), perfusion fraction (Fp) and diffusion coefficient (D). Monoexponential apparent diffusion coefficient (ADC) was calculated for comparison with D.ResultsBiopsy revealed squamous cell carcinoma in 10 patients and adenocarcinoma in 9. The b-value threshold (median [interquartile range]) depended on the histological type and was 35 (22.5–50) s/mm2 in squamous cell carcinoma and 150 (100–150) s/mm2 in adenocarcinoma (p < 0.05). Comparing squamous cell vs. adenocarcinoma, D* (45.1 [25.1–60.4] × 10−3 mm2/s vs. 12.4 [10.5–21.2] × 10−3 mm2/s) and Fp (7.5% [7.0–9.0%] vs. 9.9% [9.0–11.4%]) differed significantly between the subtypes (p < 0.02), whereas D did not (0.89 [0.75–0.94] × 10−3 mm2/s vs. 0.90 [0.82–0.97] × 10−3 mm2/s, p = 0.27). The residuals did not differ (0.74 [0.60–0.92] vs. 0.94 [0.67–1.01], p = 0.32). The ADC systematically underestimated the magnitude of diffusion restriction compared to D (p < 0.001).ConclusionThe parameter-free IVIM approach is feasible in cervical cancer. The b-value threshold and perfusion-related parameters depend on the tumor histology type.

Green Banana (Musa cavendishii) Osmotic Dehydration by Non-Caloric Solutions: Modeling, Physical-Chemical Properties, Color, and Texture

Osmotic dehydration effects on the kinetics and on some quality attributes of green banana slices (Musa cavendishii) at 25 °C with non-caloric solutes (glycerol, sorbitol, and a mixture of both) at concentrations varying from 40 to 60 g/100 g for up to 6 h were studied. The three-component diagram showed that the first pseudo-equilibrium was achieved, and the water pseudo-diffusion coefficient presented higher values with glycerol solutions. A modified Peleg’s model was applied to obtain the maximum water loss. Changes in green banana physical-chemical properties were observed: moisture content from 1.25 to 0.19 kg/kg dry basis, soluble solute content from 5.4 to 16.9 °Brix; total color-difference from 2.7 to 15.8; and the maximum biaxial extensional viscosity from 0.63 to 1.53 MPa s. Moreover, the obtained low chroma difference values suggest that the osmotically drying process may be a suitable technique to preserve the final color of green banana slices.

Quantitative assessment of hyperacute cerebral infarction with intravoxel incoherent motion MR imaging: Initial experience in a canine stroke model.

To evaluate the feasibility of intravoxel incoherent motion (IVIM) for the measurement of diffusion and perfusion parameters in hyperacute strokes. An embolic ischemic model was established with an autologous thrombus in 20 beagles. IVIM imaging was performed on a 3.0 Tesla platform at 4.5 h and 6 h after embolization. Ten b values from 0 to 900 s/mm2 were fitted with a bi-exponential model to extract perfusion fraction f, diffusion coefficient D, and pseudo-diffusion coefficient D*. Additionally, the apparent diffusion coefficient (ADC) was calculated using the mono-exponential model with all the b values. Statistical analysis was performed using the pairwise Student's t test and Pearson's correlation test. A significant decrease in f and D was observed in the ischemic area when compared with those in the contralateral side at 4.5 h and 6 h after embolization (P < 0.01 for all). No significant difference was observed in D* between the two sides at either time point (P = 0.086 and 0.336, respectively). In the stroke area, f at 6 h was significantly lower than that at 4.5 h (P = 0.016). A significantly positive correlation was detected between ADC and D in both stroke and contralateral sides at 4.5 h and 6 h (P < 0.001 for both). Significant correlation between ADC and f was only observed in the contralateral side at 4.5 h and 6 h (P = 0.019 and 0.021, respectively). IVIM imaging could simultaneously evaluate the diffusion and microvascular perfusion characteristics in hyperacute strokes. 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:550-556.

Correlation between intravoxel incoherent motion MR parameters and MR nodular grade of parotid glands in patients with Sjögren’s syndrome: A pilot study

PurposeTo explore the correlation between intravoxel incoherent motion (IVIM) magnetic resonance (MR) parameters and MR nodular grade of parotid glands in patients with Sjögren’s syndrome (SS). Materials and methodsA total of 31 consecutive patients with SS and 28 gender- and age-matched healthy volunteers underwent bilateral parotid 3.0T MR examination including the IVIM sequence (9 b values, 0–800s/mm2). The apparent diffusion coefficient (ADC), diffusion coefficient D, pseudo-diffusion coefficient D*, and perfusion fraction f of bilateral parotid glands were obtained, and the nodular grade of each parotid gland was evaluated according to the MR morphological appearance. ResultsSixty-two parotid glands in 31 patients with SS consisted of 32, 14, 8, and 8 parotid glands at MR nodular grades 0, 1, 2, and 3, respectively. In parotid glands of grade 0, 1, 2, 3 and healthy volunteers, the ADC values were (1.13±0.25, 1.11±0.17, 1.05±0.24, 0.89±0.04 and 1.00±0.21)×10−3mm2/s, D values were (0.92±0.13, 0.90±0.19, 0.90±0.03, 0.67±0.03, 0.81±0.03)×10−3mm2/s, f values were 0.20±0.04, 0.18±0.02, 0.15±0.01, 0.11±0.01, 0.15±0.06, and D*values were (53.89±28.26, 41.78±16.35, 51.24±18.69, 31.83±18.03, 36.83±16.14)×10−3mm2/s respectively. The ADC, D, f, and D* values of parotid glands in patients with SS at grade 0 were significantly higher than those in healthy volunteers (all P<0.05). Significant differences were observed in the D and f values of parotid glands in patients with SS among different grades (P=0.003,<0.001, respectively). The IVIM parameters (D, f) of parotid glands at early (grades 0–1) and advanced (grades 2–3) stages in patients with SS were significantly higher and lower, respectively, than those in healthy volunteers (all P<0.05). The D and f values inversely correlated with MR nodular grades significantly (r=− 0.297, P=0.019; r=− 0.653, P<0.001, respectively) ConclusionThe parotid glands with different MR nodular grades in patients with SS showed different IVIM parameters, reflecting different pathophysiological characteristics of parotid glands at different stages.

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.

Total variation-based method for generation of intravoxel incoherent motion parametric images in MRI.

Total variation (TV) method has been used widely for image restoration and reconstruction. In this work, we propose a TV-based algorithm for parametric image generation in intravoxel incoherent motion (IVIM) diffusion-weighted magnetic resonance imaging (DW-MRI). We used simulated and real data to investigate whether the proposed TV-based method can provide reliable parametric images. Parametric images of IVIM parameters including perfusion fraction (PF), diffusion coefficient (D), and pseudo-diffusion coefficient (D*) were estimated using DW-MRI data and TV through fitting the IVIM model. The Levenberg-Marquardt (LM) method, which has often been used in the context of IVIM analysis, was employed as the standard method for comparison of the resulting parametric images. The simulation results show that the proposed method outperforms the LM algorithm in terms of precision, providing a 40-81%, 90-93%, and 68-84% improvement for PF, D and D*, respectively, at signal-to-noise ratio (SNR) of 30. For real data, the proposed method showed an average five-fold, three-fold, and four-fold improvement in the SNR for PF, D and D*, respectively. We introduced the use of TV to produce parametric images, and demonstrated that the proposed TV-based method is effective in improving the parametric image quality. Magn Reson Med 78:1383-1391, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Intravoxel incoherent motion (IVIM) in diffusion-weighted imaging (DWI) for Hepatocellular carcinoma: correlation with histologic grade.

PurposeTo assess the correlation between DWI diffusion parameters obtained using Intravoxel Incoherent Motion Method (IVIM) and histological grade of Hepatocellular carcinoma (HCC).ResultsAccording to Edmondson-Steiner grade lesions were classified with grade 1 (14), grade 2 (30), grade 3 (18), and grade 4 (0). Apparent Diffusion Coefficient (ADC), perfusion fraction (fp), tissue diffusion coefficient (Dt) median values were statistically different in HCC groups with 1, 2, 3 histological grade (p<0.001). A significant correlation was reported between ADC, fp, Dt and histologic grade respectively of 0.687, 0.737 and 0.674. Receiver operating characteristic (ROC) analysis demonstrated that an ADC of 2.11×10-3 mm2/sec, an fp of 47.33% and an Dt of 0.94×10-3 mm2/sec were the optimal cutoff values to differentiate high histological grade (3) versus low histological grade (1-2), with a sensitivity and specificity for ADC of 100% and 100%, for fp of 100% and 89%, for Dt of 100% and 74%, respectively.Material and MethodsA retrospective approved study was performed including 34 patients with 62 HCCs. IVIM was performed to obtain ADC, fp, pseudo-diffusion coefficient (Dp), Dt coefficients. Kruskal Wallis, Spearman Correlation Coefficient, ROC analysis were performed.ConclusionsADC and IVIM-derived fp showed significantly better diagnostic performance in differentiating high-grade from low-grade HCC, and significant correlation was observed between ADC, fp, Dt and histological grade.

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

Assessment of early renal allograft function after transplantation using renal intravoxel incoherent motion imaging and T1 mapping

Objectives To investigate the ability of T1 mapping and intravoxel incoherent motion imaging (IVIM) parameters for evaluating renal allografts at the early stage after renal transplantation. Methods This prospective study protocol was approved by the local ethics committee, and written informed consent was obtained from all subjects. Sixty two recipients 2 to 4 weeks after kidney transplantation and 20 healthy volunteers (control group) underwent routine MRI, T1 mapping, and IVIM imaging (11 b values, 0 to 700 s/mm2). Recipients were divided into two groups base on their estimated glomerular filtration rate (eGFR): 37 recipients with good allograft function (eGFR ≥60 ml·min-1·1.73 m-2) and 25 recipients with impaired allograft function (eGFR<60 ml·min-1·1.73 m-2). The ADC, true diffusion coefficient (ADCslow), pseudo-diffusion coefficient (ADCfast), perfusion fraction (f) and T1 values were measured on both cortex and medulla. Differences among groups were compared using the one-way analysis of variance. Correlations between eGFR and the parameters in renal allografts were assessed by using Pearson correlation analysis. ROC was performed to assess the diagnostic utilities of using these parameters to discriminate allografts with impaired function from good function. Results Excepting for cortical T1, ADCfast and medullary T1, f values, allografts with good function showed no differences in other parameters compared with healthy control. Excepting for medullary T1 and ADCfast, the other values showed significantly differences in allografts with impaired function compared to allografts with good function (all P<0.05). Excepting for medullary f and ADCfast values, allografts with impaired function showed significantly differences in the parameters compared with good function group(all P<0.05). In renal allografts, excepting for medullary T1, ADCfast, and f values, cortical T1 exhibited a negative correlation with renal function, and there was a significant positive correlation between eGFR and other parameters. Cortical T1 value showed high sensitivity(91.9%) to discriminate renal allografts with different function, with the threshold of 17.36× 102 ms, and ADC value showed high specificity(96.0%)with the threshold of 1.98×10-3 mm2/s. Conclusion T1 mapping and IVIM technique may be useful for detecting renal allograft dysfunction, and be a reliable imaging for evaluating and monitoring allograft function. Key words: Kidney transplantation; Magnetic resonance imaging; Renal insufficiency

Modulation of renal oxygenation and perfusion in rat kidney monitored by quantitative diffusion and blood oxygen level dependent magnetic resonance imaging on a clinical 1.5T platform.

BackgroundTo investigate the combined use of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) and blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) to assess rat renal function using a 1.5T clinical platform.MethodsMultiple b-value DW and BOLD MR images were acquired from adult rats using a parallel clinical coil arrangement, enabling quantitation of the apparent diffusion coefficient (ADC), IVIM-derived diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f), and the transverse relaxation time T2*, for whole kidney, renal cortex, and medulla. Following the acquisition of two baseline datasets to assess measurement repeatability, images were acquired following i.v. administration of hydralazine, furosemide, or angiotensin II for up to 40 min.ResultsExcellent repeatability (CoV <10 %) was observed for ADC, D, f and T2* measured over the whole kidney. Hydralazine induced a marked and significant (p < 0.05) reduction in whole kidney ADC, D, and T2*, and a significant (p < 0.05) increase in D* and f. Furosemide significantly (p < 0.05) increased whole kidney ADC, D, and T2*. A more variable response to angiotensin II was determined, with a significant (p < 0.05) increase in medulla D* and significant (p < 0.05) reduction in whole kidney T2* established.ConclusionsMultiparametric MRI, incorporating quantitation of IVIM DWI and BOLD biomarkers and performed on a clinical platform, can be used to monitor the acute effects of vascular and tubular modulating drugs on rat kidney function in vivo. Clinical adoption of such functional imaging biomarkers can potentially inform on treatment effects in patients with renal dysfunction.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-016-0356-x) contains supplementary material, which is available to authorized users.