Three-dimensional turbo-spin-echo amide proton transfer-weighted and intravoxel incoherent motion MR imaging for type I endometrial carcinoma: Correlation with Ki-67 proliferation status

BackgroundTo evaluate 3-dimensional amide proton transfer weighted (APTw) imaging for type I endometrial carcinoma (EC), and investigate correlations of Ki-67 labelling index with APTw and intravoxel incoherent motion (IVIM) imaging.Methods54 consecutive patients suspected of endometrial lesions underwent pelvic APTw and IVIM imaging on a 3 T MR scanner. APTw values and IVIM-derived parameters (Dt, D*, f) were independently measured by two radiologists on 22 postoperative pathological confirmed of type I EC lesions. Results were compared between histological grades and Ki-67 proliferation groups. ROC analysis was performed. Pearson's correlation analysis was performed for APTw values and IVIM-derived parameters with Ki-67 labeling index.ResultsAPTw values and Dt, D*, f of all type I EC were 2.9 ± 0.1%, 0.677 ± 0.027 × 10⁻³ mm²/s, 31.801 ± 11.492 × 10⁻³ mm²/s, 0.179 ± 0.050 with inter-observer ICC 0.996, 0.850, 0.956, 0.995, respectively. APTw values of Ki-67 low-proliferation group (<30%, n = 8) were 2.5 ± 0.2%, significantly lower than the high-proliferation group (>30%, n = 14) with APTw values of 3.1 ± 0.1% (p = 0.016). Area under the curve was 0.768. APTw values of type I EC were moderately positively correlated with Ki-67 labelling index (r = 0.583, p = 0.004). There was no significant difference of Dt (p = 0.843), D* (p = 0.262), f (p = 0.553) between the two groups. No correlation was found between IVIM-derived parameters and Ki-67 labelling index (Dt, p = 0.717; D* p = 0.151; f, p = 0.153).Conclusion3D TSE APTw imaging is a feasible approach for detecting type I EC. Ki-67 labeling index positively moderately correlates with APTw not with IVIM.     

Associations between histogram analysis parameters derived from dynamic-contrast enhanced MRI and PD L1-expression in head and neck squamous cell carcinomas. A preliminary study

PurposeProgrammed death 1 ligand (PD-L 1) plays an essential role in oncology. It might be crucial to predict its expression non-invasively by imaging. Dynamic-contrast enhanced MRI (DCE MRI) is one of the important imaging modalities in head and neck squamous cell cancer (HNSCC). The aim of the present study was to analyze possible associations between histogram analysis parameters of DCE MRI and PD-L 1 expression in HNSCCMethodsOverall, 26 patients with primary HNSCC of different localizations were involved in the study. DCE MRI was obtained on a 3 T MRI and analyzed with a whole lesion measurement using a histogram approach. PD-L 1 expression was estimated on bioptic samples before any form of treatment using 3 scores (Tumor positive score (TPS), Immune cell score (ICS) and Combined positive score (CPS)).ResultsCPS correlated with mode derived from Ktrans (r = 0.40, p = .04). Also CPS correlated with P90 derived from Kep (r = 0.40, p = .04). ICS correlated with the maximum derived from Kep (r = 0.41, p = .03) and entropy derived from Kep (r = 0.43, p = .02). There were no associations between DCE MRI parameters and TPS.ConclusionKtrans and Kep related histogram analysis parameters derived from DCE MRI correlated moderately with PD-L 1 expression of immune cells in HNSCC.     

Predicting the nodal status in gastric cancers: The role of apparent diffusion coefficient histogram characteristic analysis

PurposeTo explore the application of histogram analysis in preoperative T and N staging of gastric cancers, with a focus on characteristic parameters of apparent diffusion coefficient (ADC) maps.Materials and methodsEighty-seven patients with gastric cancers underwent diffusion weighted magnetic resonance imaging (b = 0, 1000 s/mm²), which generated ADC maps. Whole-volume histogram analysis was performed on ADC maps and 7 characteristic parameters were obtained. All those patients underwent surgery and postoperative pathologic T and N stages were determined.ResultsFour parameters, including skew, kurtosis, s-sD_av and sample number, showed significant differences among gastric cancers at different T and N stages. Most parameters correlated with T and N stages significantly and worked in differentiating gastric cancers at different T or N stages. Especially skew yielded a sensitivity of 0.758, a specificity of 0.810, and an area under the curve (AUC) of 0.802 for differentiating gastric cancers with and without lymph node metastasis (P < 0.001). All the parameters, except AUC_low, showed good or excellent inter-observer agreement with intra-class correlation coefficients ranging from 0.710 to 0.991.ConclusionCharacteristic parameters derived from whole-volume ADC histogram analysis could help assessing preoperative T and N stages of gastric cancers.     

Intravoxel incoherent motion magnetic resonance imaging for breast cancer: A comparison with molecular subtypes and histological grades

PurposeThe purpose of this paper is to investigate whether the IVIM parameters (D, D *, f) helps to determine the molecular subtypes and histological grades of breast cancer.MethodsFifty-one patients with breast cancer were included in the study. All subjects were examined by 3 T Magnetic Resonance Imaging (MRI). Diffusion-weighted imaging (DWI) was undertaken with 16 b-values. IVIM parameters [D (true diffusion coefficient), D* (pseudo-diffusion coefficient), f (perfusion fraction)] were calculated. Histopathological reports were reviewed to histological grade, histological type, and immunohistochemistry. IVIM parameters of tumors with different histological grades and molecular subtypes were compared.ResultsD* and f were significantly different between molecular subtypes (p = 0.019, p = 0.03 respectively). D* and f were higher in the HER-2 group and lower in Triple negative (−) group (D*:36.8 × 10⁻³ ± 5.3 × 10⁻³ mm²/s, f:29.5%, D*:29.8 × 10⁻³ ± 5.6 × 10⁻³ mm²/s, f:21.5% respectively). There was a significant difference in D* and f between HER-2 and Triple (−) subgroups (p = 0,028, p = 0.024, respectively). D* was also significantly different between the HER-2 group and the Luminal group (p = 0,041). While histological grades increase, D and f values tend to decrease, and D* tends to increase. While the Ki-67 index increases, D* and f values tend to increase, and D tend to decrease.ConclusionD* and f values measured with IVIM imaging were useful for assessing breast cancer molecular subtyping. IVIM imaging may be an alternative to breast biopsy for sub-typing of breast cancer with further research.     

Histogram parameters derived from T1 and T2 weighted images correlate with tumor infiltrating lymphocytes and tumor-stroma ratio in head and neck squamous cell cancer

PurposeThe present study used histogram analysis values derived from T1- and T2- weighted (w) images to elucidate possible associations with Tumor-infiltrating lymphocytes (TIL) and Vimentin expression in head and neck squamous cell cancer (HNSCC).Materials and methodsOverall, 28 patients (n = 8 female patient, 28.6%) with primary HNSCC of different localizations were involved in the study. Magnetic resonance imaging (MRI) was obtained on a 3 T MRI. The images were analyzed with a whole lesion measurement using a histogram approach. TIL- and vimentin-expression was calculated on biopsy samples before any form of treatment.ResultsSeveral T1-derived parameters correlated with the expression of TIL within the stroma compartment: mean (r = 0.42, p = 0.025), p10 (r = 0.50, p = 0.007), p25 (r = 0.42, p = 0.025), median (r = 0.39, p = 0.036), and mode (r = 0.39, p = 0.04). No T2-derived parameter correlated with the TIL within the stroma compartment. Several T2-derived parameters correlated with the expression of TIL within the tumor compartment: mean (r = −0.52, p = 0.004), max (r = −0.43, p = 0.02), p10 (r = −0.38, p = 0.04), p25 (r = −0.53, p = 0.004), p75 (r = −0.52, p = 0.004), p90 (r = −0.48, p = 0.009), median (r = −0.52, p = 0.004), mode (r = −0.40, p = 0.03). Kurtosis derived from T2w images had significant higher values in tumor-rich tumors, compared to stroma-rich tumors, (mean 5.5 ± 0.5 versus 4.2 ± 1.2, p = 0.028).ConclusionsHistogram analysis parameters derived from T1w and T2w images might be able to reflect tumor compartments and TIL expression in HNSCC.     

Characterization of mediastinal lymphadenopathy with diffusion-weighted imaging

Purpose

To predict malignancy of mediastinal lymphadenopathy with diffusion-weighted imaging.

Material and methods

A prospective study was conducted on 35 patients with mediastinal lymphadenopathy (28 malignant and seven benign nodes). They underwent echoplanar diffusion-weighted magnetic resonance imaging of the mediastinum with b-factors of 0, 300 and 600 s/mm². The apparent diffusion coefficient (ADC) values of the mediastinal lymph nodes were calculated. The ADC values were correlated with the biopsy results and statistical analysis was done. A value of P<.05 was considered significant.

Results

The mean ADC value of malignant mediastinal lymphadenopathy (1.06±0.3×10⁻³ mm²/s) was significantly lower (P=.001) than that of benign lymphadenopathy (2.39±0.7×10⁻³ mm²/s). There was an insignificant difference in the ADC values between metastatic and lymphomatous mediastinal lymph nodes (P=.32) as well as within benign nodes (P=.07). When an ADC value of 1.85×10⁻³ mm²/s was used as a threshold value for differentiating malignant mediastinal nodes from benign nodes, the best results were obtained with an accuracy of 83.9%, a sensitivity of 96.4%, a specificity of 71.4%, a negative predictive value of 95.2% and a positive predictive value of 77.1%. The area under the curve was 0.98.

Conclusion

Diffusion weighted magnetic resonance imaging is a promising noninvasive imaging modality that can be used for characterization of mediastinal lymphadenopathy and differentiation of malignant from benign mediastinal lymph nodes.     

Correlation between Hepatic Fat Content Using 3-Echo 3-D Dixon Method and Intravoxel Incoherent Motion (IVIM) Perfusion MR Imaging

Fat accumulates as droplets in the hepatocyte swelling, distortion of microcirculatory anatomy and compression of sinus. This study aims to investigate the correlation between the T2*-corrected fat fraction (FF) value acquired via gradient echo with a low flip angle and parenchymal pseudorandom blood perfusion (P _fraction), microcirculation (D _fast), and slow component of diffusion (D _slow), acquired via intravoxel incoherent motion (IVIM), and to investigate the blood microcirculation and diffusion components of liver parenchyma, according to fat deposition. A total of 126 patients underwent 3-T magnetic resonance imaging, including a 3-echo three-dimensional (3-D) gradient echo sequence with T2*-corrected Dixon reconstruction and IVIM sequence. Pearson’s correlation analysis was conducted to investigate the correlation of the FF obtained via the Dixon method with the apparent diffusion coefficient (ADC), D _slow, P _fraction, and D _fast obtained via IVIM. Correlation analysis was also conducted for the IVIM mapping images. A confidence level of p < 0.05 was set. A negative correlation was found between the T2*-corrected FF acquired using the 3-echo 3-D Dixon method and D _slow acquired via IVIM (r = ?0.181, p < 0.05). It was likely due to the increased extracellular collagen deposition and increased intracellular fat droplets during the progression of liver fibrosis.     

Interrelationships between 3-T-MRI-derived cortical and trabecular bone structure parameters and quantitative-computed-tomography-derivedbone mineral density

Recently, 3-T magnetic resonance imaging (MRI) has been introduced for bone imaging. Through higher signal-to-noise ratios, as compared to 1.5-T MRI, it promises to be a more powerful tool for the assessment of cortical and trabecular bone measures. The goal of our study was to compare MRI-derived cortical and trabecular bone measures to quantitative computed tomography (QCT)-derived bone mineral density (BMD). Using 3-T MRI in 51 postmenopausal women, apparent (app.) measures of bone volume/total volume, trabecular number (Tb.N), trabecular thickness (Tb.Th) and trabecular separation were derived at the distal radius, distal tibia and calcaneus. Cortical thickness (Ct.Th) was calculated at the distal radius and distal tibia. These measures were compared to QCT-derived BMD of the spine, hip and radius. Significant correlations (^?P<.05; ^??P<.001; ^???P<.0001) were found between spine BMD- and MRI-derived Ct.Th (r_radius=.55, ^?P<.05; r_tibia=.67, ^???P<.0001) and app. Tb.N (r_radius=.33, ^?P<.05; r_tibia=.35, ^?P<.05) at the radius and tibia. Furthermore, within the first 10 mm at the radius, an inverse correlation for Ct.Th and app. BV/TV (r_6mm=−.56, P<.001; r_10mm=−.36, P<.05) and app. Tb.Th (r_6mm=−.54, P<.001; r_10mm=−.41, P<.05) was found.     

Comparison of accuracy of intravoxel incoherent motion and apparent diffusion coefficient techniques for predicting malignancy of head and neck tumors using half-Fourier single-shot turbo spin-echo diffusion-weighted imaging

Purpose

To evaluate the use of the intravoxel incoherent motion (IVIM) technique in half-Fourier single-shot turbo spin-echo (HASTE) diffusion-weighted imaging (DWI), and to compare its accuracy to that of apparent diffusion coefficient (ADC) to predict malignancy in head and neck tumors.

Patients and methods

HASTE DW images of 33 patients with head and neck tumors (10 benign and 23 malignant) were evaluated. Using the IVIM technique, parameters (D, true diffusion coefficient; f, perfusion fraction; D*, pseudodiffusion coefficient) were calculated for each tumor. ADC values were measured over a range of b values from 0 to 1000 s/mm². IVIM parameters and ADC values in benign and malignant tumors were compared using Student's t test, receiver operating characteristics (ROC) analysis, and multivariate logistic regression modeling.

Results

Mean ADC and D values of malignant tumors were significantly lower than those of benign tumors (P < 0.05). Mean D* values of malignant tumors were significantly higher than those of benign tumors (P < 0.05). There was no significant difference in mean f values between malignant and benign tumors (P > 0.05). The technique of combining D and D* was the best for predicting malignancy; accuracy for this model was higher than that for ADC.

Conclusions

The IVIM technique may be applied in HASTE DWI as a diagnostic tool to predict malignancy in head and neck masses. The use of D and D* in combination increases the diagnostic accuracy in comparison with ADC.     

Feasibility of T1 mapping with histogram analysis for the diagnosis and staging of liver fibrosis: Preclinical results

PurposeTo compare the diagnostic accuracy of parameters derived from the histogram analysis of precontrast, 10-min hepatobiliary phase (HBP) and 20-min HBP T1 maps for staging liver fibrosis (LF).MethodsLF was induced in New Zealand white rabbits by subcutaneous injections of carbon tetrachloride for 4–16 weeks (n = 120), and 20 rabbits injected with saline served as controls. Precontrast, 10-min and 20-min HBP modified Look-Locker inversion recovery (MOLLI) T1 mapping was performed. Histogram analysis of T1 maps was performed, and the mean, median, skewness, kurtosis, entropy, inhomogeneity and 10th/25th/75th/90th percentiles of T1_native, T1_10min and T1_20min were derived. Quantitative histogram parameters were compared. For significant parameters, further receiver operating characteristic (ROC) analyses were performed to evaluate the potential diagnostic performance in differentiating LF stages.ResultsFinally, 17, 20, 21, 21 and 20 rabbits were included for the F0, F1, F2, F3, and F4 pathological grades of fibrosis, respectively. The mean/75th of T1_native, entropy of T1_10min and entropy/mean/median/10th of T1_20min demonstrated a significant good correlation with the LF stage (|r| = 0.543–0.866, all P < 0.05). The 75th of T1_native, entropy_10min, and entropy_20min were the three most reliable imaging markers in reflecting the stage of LF. The area under the ROC curve of entropy_20min was larger than that of entropy_10min (P < 0.05 for LF ≥ F2, ≥F3, and ≥ F4) and the 75th of T1_native (P < 0.05 for LF ≥ F2 and ≥ F3) for staging LF.ConclusionMagnetic resonance histogram analysis of T1 maps, particularly the entropy derived from 20-min HBP T1 mapping, is promising for predicting the LF stage.     

Biexponential analysis of intravoxel incoherent motion in calf muscle before and after exercise: Comparisons with arterial spin labeling perfusion and T2

PurposeThis study aimed to clarify exercise-induced changes in intravoxel incoherent motion (IVIM) parameters obtained from diffusion-weighted imaging (DWI) of the calf muscle, as well as the relationships between IVIM parameters, perfusion, and water content in muscle tissue.Materials and methodsThirteen healthy volunteers underwent IVIM-DWI, arterial spin labeling (ASL), and multi-echo spin-echo T₂ mapping of the right calf on a 3.0-T magnetic resonance imaging scanner before and after performing dorsiflexion exercise. From the data, we derived the perfusion-related diffusion coefficient (D^⁎), perfusion component fraction (F), blood flow parameter (FD^⁎), and restricted diffusion coefficient (D) in the tibialis anterior muscle. The muscle blood flow (MBF) and transverse relaxation time (T₂) were also calculated from the ASL and multi-echo spin-echo data, respectively. We compared the parameters measured before and after exercise and assessed the relationship of each IVIM-derived perfusion parameter (D^⁎, F, and FD^⁎) with MBF and each diffusion parameter (D and ADC) or F with T₂.ResultsNotably, all these parameters were significantly increased after exercise. Before exercise, the FD^⁎ exhibited a significant positive correlation with the MBF, whereas no significant correlation was observed between D^⁎ or F and MBF. After exercise, both D^⁎ and FD^⁎ exhibited significant positive correlations with MBF, whereas F was not significantly correlated with MBF. Additionally, D was significantly correlated with T₂ after exercise, but not before exercise. No significant correlations were found between ADC and T₂ either before or after exercise.ConclusionsThe IVIM analyses before and after exercise enable the simultaneous evaluation of exercise-induced changes in perfusion and water diffusion in the muscle and increases the body of information on muscle physiology.     

Correlation analysis of apparent diffusion coefficient value and P53 and Ki-67 expression in esophageal squamous cell carcinoma

PurposesTo investigate the relationship between apparent diffusion coefficient (ADC) value and p53 and ki-67 expression in esophageal squamous cell carcinoma (ESCC) patients.Materials and methodsClinical, pathologic and MRI findings of 55 ESCC patients were retrospectively analyzed. Immunohistochemical assay was used to determine the expression level of p53 and ki-67 in esophageal carcinoma tissues. The correlations between the ADC value (including ADCmax, ADCmean and ADCmin) and p53 and ki-67 expression level were explored.ResultsSignificant differences of the ADCmean values were found between positive and negative expression of p53 and between high and low expression of ki-67 in 55 patients of ESCC (P = 0.008, P = 0.036). Receiver operation characteristic (ROC) curve analysis showed that the cutoff value of ADCmean value with positive expression of p53 was 1.475 × 10⁻³ mm²/s, the area under the curve (AUC) was 0.775, and the sensitivity and specificity were 80.0%, 70.0%, respectively. While the cutoff value for the ADCmean value with high expression of ki-67 was 1.590 × 10⁻³ mm²/s, the AUC was 0.713, and the sensitivity and specificity were 66.7%, 76.5%, respectively. The ADCmean values were significantly negatively correlated with the expression level of p53 and ki-67 (r = −0.403, P = 0.008; r = −0.329, P = 0.036).ConclusionThe ADCmean values of ESCC were related with the expression level of p53 and ki-67 in tumor tissue, which may be served as a non-invasive biological indicator to predict the proliferation of ESCC cells and judge the prognosis of patients.     

Enhanced Laws textures: A potential MRI surrogate marker of hepatic fibrosis in a murine model

PurposeTo compare enhanced Laws textures derived from parametric proton density (PD) maps to other MRI surrogate markers (T₂, PD, apparent diffusion coefficient (ADC)) in assessing degrees of liver fibrosis in an ex vivo murine model of hepatic fibrosis imaged using 11.7T MRI.MethodsThis animal study was IACUC approved. Fourteen male, C57BL/6 mice were divided into control and experimental groups. The latter were fed a 3,5-dicarbethoxy-1,4-dihydrocollidine (DDC) supplemented diet to induce hepatic fibrosis. Ex vivo liver specimens were imaged using an 11.7T scanner, from which the parametric PD, T₂, and ADC maps were generated from spin-echo pulsed field gradient and multi-echo spin-echo acquisitions. A sequential enhanced Laws texture analysis was applied to the PD maps: automated dual-clustering algorithm, optimal thresholding algorithm, global grayscale correction, and Laws texture features extraction. Degrees of fibrosis were independently assessed by digital image analysis (a.k.a. %Area Fibrosis). Scatterplot graphs comparing enhanced Laws texture features, T₂, PD, and ADC values to degrees of fibrosis were generated and correlation coefficients were calculated.ResultsHepatic fibrosis and the enhanced Laws texture features were strongly correlated with higher %Area Fibrosis associated with higher Laws textures (r = 0.89). Without the proposed enhancements, only a moderate correlation was detected between %Area Fibrosis and unenhanced Laws texture features (r = 0.70). Correlation also existed between %Area Fibrosis and ADC (r = 0.86), PD (r = 0.65), and T₂ (r = 0.66).ConclusionsHigher degrees of hepatic fibrosis are associated with increased Laws textures. The proposed enhancements could improve the accuracy of Laws texture features significantly.     

Investigation of prostate cancer using diffusion-weighted intravoxel incoherent motion imaging

Purpose

The objective of this work was to evaluate the diagnostic performance of the intravoxel incoherent motion (IVIM) model to differentiate between healthy and malignant prostate tissue.

Materials and Methods

Regions of interest were drawn in healthy and cancerous tissue of 13 patients with histologically proven prostate carcinoma and fitted to a monoexponential model [yielding the apparent diffusion coefficient (ADC)] and the IVIM signal equation (yielding the perfusion fraction f, the diffusion constant D and the pseudodiffusion coefficient of perfusion D?). Parameter maps were calculated for all parameters.

Results

The ADC, D and f were significantly (P<.005) lowered in cancerous tissue (1.01±0.22 μm²/ms, 0.84±0.19 μm²/ms and 14.27±7.10%, respectively) compared to benign tissue (1.49±0.17 μm²/ms, 1.21±0.22 μm²/ms and 21.25±8.32%, respectively). Parameter maps of D and f allowed for a delineation of the tumor, but showed higher variations compared to the ADC map.

Conclusion

Apparent diffusion coefficient maps provide better diagnostic performance than IVIM maps for tumor detection. However, the results suggest that the reduction of the ADC in prostate cancer stems not only from changes in cellularity but also from perfusion effects. IVIM imaging might hold promise for the diagnosis of other prostatic lesions.     

Diffusion tensor imaging reveals microstructural alteration of the trigeminal nerve root in classical trigeminal neuralgia without neurovascular compression and correlation with outcome after internal neurolysis

ObjectivesDiffusion tensor imaging (DTI) has been used to detect microstructural alteration and effect of surgical treatment of the trigeminal nerve root (TR) in patients with classical trigeminal neuralgia (CTN) underwent microvascular decompression (MVD). Patients with CTN without neurovascular compression (woNVC) is a special population of TN, however, the pathogenesy of CTN woNVC and the mechanism of internal neurolysis (IN) remain unknown.Materials and methods21 patients with CTN woNVC who underwent IN and 20 healthy controls were included in this study. The differences in the means, kurtosis and skewness of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) between the affected and unaffected nerves in patients and both nerves in controls were investigated by independent t-test and paired t-test respectively. Longitudinal changes of FA and ADC were correlated with outcome of IN via Spearman correlation coefficient.ResultsSignificant differences were found in preoperative mean and kurtosis values for both FA and ADC of the affected side TR, compared to the unaffected side and control group respectively. However, these differences remarkably reduced postoperatively. Further, the Spearman correlation coefficient showed a strong negative correlation between decrease of ADC in the affected side and the surgical outcome in BNI total score.ConclusionThe changes of diffusive property of TR, especially the FA and ADC, provide alternative radiological evidence for evaluating the mechanism of CTN woNVC. The modification of DTI metrics could be an effective factor for providing potential noninvasive biomarkers for determining the prognosis of patients with CTN woNVC underwent IN.     

Assessment of hepatocellular carcinoma using apparent diffusion coefficient and diffusion kurtosis indices: preliminary experience in fresh liver explants

Objectives

The objective was to perform ex vivo evaluation of non-Gaussian diffusion kurtosis imaging (DKI) for assessment of hepatocellular carcinoma (HCC), including presence of treatment-related necrosis, using fresh liver explants.

Methods

Twelve liver explants underwent 1.5-T magnetic resonance imaging using a DKI sequence with maximal b-value of 2000 s/mm². A standard monoexponential fit was used to calculate apparent diffusion coefficient (ADC), and a non-Gaussian kurtosis fit was used to calculate K, a measure of excess kurtosis of diffusion, and D, a corrected diffusion coefficient accounting for this non-Gaussian behavior. The mean value of these parameters was measured for 16 HCCs based upon histologic findings. For each metric, HCC-to-liver contrast was calculated, and coefficient of variation (CV) was computed for voxels within the lesion as an indicator of heterogeneity. A single hepatopathologist determined HCC necrosis and cellularity.

Results

The 16 HCCs demonstrated intermediate-to-substantial excess diffusional kurtosis, and mean corrected diffusion coefficient D was 23% greater than mean ADC (P=.002). HCC-to-liver contrast and CV of HCC were greater for K than ADC or D, although these differences were significant only for CV of HCCs (P≤.046). ADC, D and K all showed significant differences between non-, partially and completely necrotic HCCs (P≤.004). Among seven nonnecrotic HCCs, cellularity showed a strong inverse correlation with ADC (r=−0.80), a weaker inverse correlation with D (− 0.24) and a direct correlation with K (r= 0.48).

Conclusions

We observed non-Gaussian diffusion behavior for HCCs ex vivo; this DKI model may have added value in HCC characterization in comparison with a standard monoexponential model of diffusion-weighted imaging.     

In vivo multiparametric magnetic resonance imaging study for differentiating the severity of hepatic warm ischemia-reperfusion injury in a rabbit model

ObjectivesTo assess the value of multiparametric magnetic resonance imaging including intravoxel incoherent motion (IVIM), diffusion tensor imaging (DTI) and blood oxygen level dependent (BOLD) MRI in differentiating the severity of hepatic warm ischemia-reperfusion injury (WIRI) in a rabbit model.MethodsFifty rabbits were randomly divided into a sham-operation group and four test groups (n = 10 for each group) according to different hepatic warm ischemia times. IVIM, DTI and BOLD MRI were performed on a 3 T MR scanner with 11 b values (0 to 800 s/mm²), 2 b values (0 and 500 s/mm²) on 12 diffusion directions, multiple-echo gradient echo (GRE) sequences (TR/TE, 75/2.57–24.25 ms), respectively. IVIM, DTI and BOLD MRI parameters, hepatic biochemical and histopathological parameters were compared. Pearson and Spearman correlation methods were performed to assess the correlation between these MRI parameters and laboratory parameters. Furthermore, receiver operating characteristic (ROC) curves were compiled to determine diagnostic efficacies.ResultsTrue diffusion (Dslow), pseudodiffusion (Dfast), perfusion fraction (PF), mean diffusivity (MD) significantly decreased, while R2* significantly increased with prolonged warm ischemia times, and significant differences were found in all of biochemical and histopathological parameters (all P < 0.05). Dslow, PF, and R2* correlated significantly with all of biochemical and histopathological parameters (all |r| = 0.381–0.746, all P < 0.05). ROC analysis showed that the area under the ROC curve (AUC) of IVIM across hepatic WIRI groups was the largest among IVIM, DTI and BOLD.ConclusionsMultiparametric MRI may be helpful with characterization of early changes and determination of severity of hepatic WIRI in a rabbit model.     

Perfusion parameters derived from MRI for preoperative prediction of IDH mutation and MGMT promoter methylation status in glioblastomas

PurposeTo investigate the feasibility for preoperative prediction of IDH mutation and MGMT promoter methylation status in glioblastomas(GBMs) by intravoxel incoherent motion(IVIM) and dynamic susceptibility contrast(DSC).MethodsPreoperative IVIM and DSC images of 71 patients(IDH mutation:45, IDH wildtype: 26; MGMT methylation: 31, MGMT unmethylation:40) with glioblastomas were analyzed retrospectively. Perfusion parameters including microcirculation perfusion coefficient(D*), perfusion fraction(f), cerebral blood volume(CBV) and cerebral blood flow(CBF) were measured. Corrected perfusion parameters containing corrected perfusion coefficient(ADC_perf) and simplified perfusion fraction(SPF) were from the simplified IVIM with 3 b values. Correlations among parameters were analyzed by Spearman correlation. All parameters were compared with Mann-Whitney U test. Univariate and multivariate logistic regression models were constructed. The receiver operating characteristic(ROC) curve was analyzed.ResultsThe IVIM parameters showed merely moderate correlations with CBV and showed no correlation with CBF. IDH mutation GBMs showed lower D*, ADC_perf, SPF, CBV and higher f than IDH wildtype GBMs(all p < 0.05). D* was the independent predictor for IDH mutation with the highest AUC of 0.912(95%CI: 0.821–0.966). The D*, ADC_perf, SPF and CBV of MGMT promoter methylation GBMs were lower than unmethylation GBMs while f was higher(all p < 0.05). Multivariate model showed the highest prediction efficacy for MGMT promoter methylation with an AUC of 0.915(95%CI: 0.824–0.968). The CBF was not useful in distinguishing IDH mutation and MGMT promoter methylation status(p = 0.055, 0.215).ConclusionIDH mutation and MGMT promoter methylation status in GBMs can be assessed effectively by IVIM and DSC. Besides, D* was the independent predictor of IDH mutation status.     

Gas challenge-blood oxygen level-dependent (GC-BOLD) MRI in the rat Novikoff hepatoma model

Purpose

The purpose of the study was to investigate the relationship between gas challenge-blood oxygen level-dependent (GC-BOLD) response angiogenesis and tumor size in rat Novikoff hepatoma model.

Materials and Methods

Twenty adult male Sprague-Dawley rats (weighting 301-325 g) were used for our Animal Care and Use Committee-approved experiments. N1-S1 Novikoff hepatomas were grown in 14 rats with sizes ranging from 0.42 to 2.81 cm. All experiments were performed at 3.0 T using a custom-built rodent receiver coil. A multiple gradient-echo sequence was used for R2^? measurements, first during room air (78% N₂/20% O₂) breathing and then after 10 min of carbogen (95% O₂/5% CO₂) breathing. After image acquisition, rats were euthanized, and the tumors were harvested for histological evaluation.

Results

The R2^? change between air and carbogen breathing for small hepatomas was positive; R2^? changes changed to negative values for larger hepatomas. We found a significant positive correlation between tumor R2^? change and tumor microvessel density (MVD) (r=0.798, P=.001) and a significant inverse correlation between tumor R2^? change and tumor size (r=−0.840, P<.0001).

Conclusions

GC-BOLD magnetic resonance imaging measurements are well correlated to MVD levels and tumor size in the N1-S1 Novikoff hepatoma model; GC-BOLD measurements may serve as noninvasive biomarkers for evaluating angiogenesis and disease progression and/or therapy response.