Intravoxel Incoherent Motion Magnetic Resonance Imaging for Assessing Parotid Gland Tumors: Correlation and Comparison with Arterial Spin Labeling Imaging

Objective@#To compare and correlate the findings of intravoxel incoherent motion (IVIM) magnetic resonance (MR) imaging and arterial spin labeling (ASL) imaging in characterizing parotid gland tumors. @*Materials and Methods@#We retrospectively reviewed 56 patients with parotid gland tumors evaluated by MR imaging. The true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and fraction of perfusion (f) values of IVIM imaging and tumor-to-parotid gland signal intensity ratio (SIR) on ASL imaging were calculated. Spearman rank correlation coefficient, chi-squared, Mann-Whitney U, and Kruskal-Wallis tests with the post-hoc Dunn-Bonferroni method and receiver operating characteristic curve assessments were used for statistical analysis. @*Results@#Malignant parotid gland tumors showed significantly lower D than benign tumors (p = 0.019). Within subgroup analyses, pleomorphic adenomas (PAs) showed significantly higher D than malignant tumors (MTs) and Warthin’s tumors (WTs) (p < 0.001). The D* of WTs was significantly higher than that of PAs (p = 0.031). The f and SIR on ASL imaging of WTs were significantly higher than those of MTs and PAs (p < 0.05). Significantly positive correlation was found between SIR on ASL imaging and f (r = 0.446, p = 0.001). In comparison with f, SIR on ASL imaging showed a higher area under curve (0.853 vs. 0.891) in discriminating MTs from WTs, although the difference was not significant (p = 0.720). @*Conclusion@#IVIM and ASL imaging could help differentiate parotid gland tumors. SIR on ASL imaging showed a significantly positive correlation with f. ASL imaging might hold potential to improve the ability to discriminate MTs from WTs.

Thyroid-Associated Orbitopathy: Evaluating Microstructural Changes of Extraocular Muscles and Optic Nerves Using Readout-Segmented Echo-Planar Imaging-Based Diffusion Tensor Imaging

OBJECTIVE: We aimed to investigate the ability of readout-segmented echo-planar imaging (rs-EPI)-based diffusion tensor imaging (DTI) in assessing the microstructural change of extraocular muscles (EOMs) and optic nerves in patients with thyroid-associated orbitopathy (TAO) as well as in evaluating disease activity.MATERIALS AND METHODS: We enrolled 35 TAO patients and 22 healthy controls (HCs) who underwent pre-treatment rs-EPI-based DTI. Mean, axial, and radial diffusivity (MD, AD, and RD) and fractional anisotropy (FA) of the medial and lateral EOMs and optic nerve for each orbit were calculated and compared between TAO and HC groups and between active and inactive TAO groups. Factors such as age, sex, disease duration, mediation, and smoking history between groups were also compared. Logistic regression analysis was used to evaluate the predictive value of significant variables for disease activity.RESULTS: Disease duration was significantly shorter in active TAOs than in inactive ones (p < 0.001). TAO patients showed significantly lower FA and higher MD, AD, and RD than HCs for both medial and lateral EOMs (p < 0.001), but not the AD value of lateral EOMs (p = 0.619). Active patients had significantly higher FA, MD, and AD than inactive patients for medial EOMs (p < 0.005), whereas only FA differed significantly in the lateral EOMs (p = 0.018). The MD, AD, and RD of optic nerves were significantly lower in TAO patients than HCs (p < 0.05), except for FA (p = 0.129). Multivariate analysis showed that the MD of medial EOMs and disease duration were significant predictors for disease activity. The combination of these two parameters showed optimal diagnostic efficiency for disease activity (area under the curve, 0.855; sensitivity, 68.4%; specificity, 96.9%).CONCLUSION: rs-EPI-based DTI is promising in assessing microstructural changes of EOMs and optic nerves and can help to indicate the disease activity of TAO, especially through the MD of medial EOMs.

Utility of Readout-Segmented Echo-Planar Imaging-Based Diffusion Kurtosis Imaging for Differentiating Malignant from Benign Masses in Head and Neck Region

OBJECTIVE: To compare the diagnostic performance of readout-segmented echo-planar imaging (RS-EPI)-based diffusion kurtosis imaging (DKI) and that of diffusion-weighted imaging (DWI) for differentiating malignant from benign masses in head and neck region. MATERIALS AND METHODS: Between December 2014 and April 2016, we retrospectively enrolled 72 consecutive patients with head and neck masses who had undergone RS-EPI-based DKI scan (b value of 0, 500, 1000, and 1500 s/mm2) for pretreatment evaluation. Imaging data were post-processed by using monoexponential and diffusion kurtosis (DK) model for quantitation of apparent diffusion coefficient (ADC), apparent diffusion for Gaussian distribution (Dapp), and apparent kurtosis coefficient (Kapp). Unpaired t test and Mann-Whitney U test were used to compare differences of quantitative parameters between malignant and benign groups. Receiver operating characteristic curve analyses were performed to determine and compare the diagnostic ability of quantitative parameters in predicting malignancy. RESULTS: Malignant group demonstrated significantly lower ADC (0.754 ± 0.167 vs. 1.222 ± 0.420, p < 0.001) and Dapp (1.029 ± 0.226 vs. 1.640 ± 0.445, p < 0.001) while higher Kapp (1.344 ± 0.309 vs. 0.715 ± 0.249, p < 0.001) than benign group. Using a combination of Dapp and Kapp as diagnostic index, significantly better differentiating performance was achieved than using ADC alone (area under curve: 0.956 vs. 0.876, p = 0.042). CONCLUSION: Compared to DWI, DKI could provide additional data related to tumor heterogeneity with significantly better differentiating performance. Its derived quantitative metrics could serve as a promising imaging biomarker for differentiating malignant from benign masses in head and neck region.

Diffusion Weighted Imaging for Differentiating Benign from Malignant Orbital Tumors: Diagnostic Performance of the Apparent Diffusion Coefficient Based on Region of Interest Selection Method

OBJECTIVE: To evaluate the differences in the apparent diffusion coefficient (ADC) measurements based on three different region of interest (ROI) selection methods, and compare their diagnostic performance in differentiating benign from malignant orbital tumors. MATERIALS AND METHODS: Diffusion-weighted imaging data of sixty-four patients with orbital tumors (33 benign and 31 malignant) were retrospectively analyzed. Two readers independently measured the ADC values using three different ROIs selection methods including whole-tumor (WT), single-slice (SS), and reader-defined small sample (RDSS). The differences of ADC values (ADC-ROI(WT), ADC-ROI(SS), and ADC-ROI(RDSS)) between benign and malignant group were compared using unpaired t test. Receiver operating characteristic curve was used to determine and compare their diagnostic ability. The ADC measurement time was compared using ANOVA analysis and the measurement reproducibility was assessed using Bland-Altman method and intra-class correlation coefficient (ICC). RESULTS: Malignant group showed significantly lower ADC-ROI(WT), ADC-ROI(SS), and ADC-ROI(RDSS) than benign group (all p 0.05). The ROI(SS) and ROI(RDSS) required comparable measurement time (p > 0.05), while significantly shorter than ROIWT (p < 0.05). The ROI(SS) showed the best reproducibility (mean difference ± limits of agreement between two readers were 0.022 [-0.080-0.123] × 10(-3) mm2/s; ICC, 0.997) among three ROI methods. CONCLUSION: Apparent diffusion coefficient values based on the three different ROI selection methods can help to differentiate benign from malignant orbital tumors. The results of measurement time, reproducibility and diagnostic ability suggest that the ROI(SS) method are potentially useful for clinical practice.

Value of dynamic ³¹P magnetic resonance spectroscopy technique in in vivo assessment of the skeletal muscle mitochondrial function in type 2 diabetes / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Phosphorous magnetic resonance spectroscopy ((31)P-MRS) has been successfully applied to study intracellular membrane compounds and high-energy phosphate metabolism. This study aimed to evaluate the capability of dynamic (31)P-MRS for assessing energy metabolism and mitochondrial function in skeletal muscle from type 2 diabetic patients.</p><p><b>METHODS</b>Dynamic (31)P-MRS was performed on 22 patients with type 2 diabetes and 26 healthy volunteers. Spectra were acquired from quadriceps muscle while subjects were in a state of rest, at exercise and during recovery. The peak areas of inorganic phosphate (Pi), phosphocreatine (PCr), and adenosine triphosphate (ATP) were measured. The concentration of adenosine diphosphate (ADP) and the intracellular pH value were calculated from the biochemistry reaction equilibrium. The time constant and recovery rates of Pi, PCr, and ADP were analyzed using exponential curve fitting.</p><p><b>RESULTS</b>As compared to healthy controls, type 2 diabetes patients had significantly lower skeletal muscle concentrations of Pi, PCr and β-ATP, and higher levels of ADP and Pi/PCr. During exercise, diabetics experienced a significant Pi peak increase and PCr peak decrease, and once the exercise was completed both Pi and PCr peaks returned to resting levels. Quantitatively, the mean recovery rates of Pi and PCr in diabetes patients were (10.74 ± 1.26) mmol/s and (4.74 ± 2.36) mmol/s, respectively, which was significantly higher than in controls.</p><p><b>CONCLUSIONS</b>Non-invasive quantitative (31)P-MRS is able to detect energy metabolism inefficiency and mitochondrial function impairment in skeletal muscle of type 2 diabetics.</p>