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Abstract Background: The α/β-hydrolase domain 2 (ABHD2) genes which was expressed in the alveolar type II cells (AT-II cells) have been identified as down-regulated genes in human emphysematous lungs. Meanwhile, ABHD2 is considered a triacylglycerol lipase. We investigated how the ABHD2 gene is involved in the development of emphysema by affecting lipid metabolism. Methods: We treated A549 cells (whose biological characteristics were similar to those of AT-II cells) with/without ABHD2 knockdown at 0,50,100umol/L palmitic acid (PA). The cells were stained by Oil Red O, probe DCFH-DA, Annexin V-FITC/PI. The contents of intracellular triglyceride, MDA, Caspase-3 activity and cell viability were determined. We analyzed of C57BL6 and Abhd2 knockdown mice at different ages. The triglyceride, cholesterol and MDA level in mouse serum were measured. The contents of triglyceride, Malondialdehyde (MDA), Caspase-3 activity in mouse lung tissues were determined. The lung tissues were stained with hematoxylin and eosin, Oil Red O and TUNEL. Results: We found that there were excessive deposition of triglyceride, lipid peroxidation, decreased cell viability and increased apoptosis in the cells with ABHD2 knockdown, showing lipid toxicity. At the same time, ABHD2 knockdown aggravates the lipid toxicity induced by PA in the A549 cells. ABHD2 deficiency resulted in abnormal lipid metabolism and lipid peroxidation in serum of mice. Meanwhile, these mice developed spontaneous gradual progression of emphysema, due to abnormal lipid metabolism, lipid peroxidation and enhanced apoptosis in lung tissues of ABHD2 knockdown mice. Conclusions: Our findings suggest that ABHD2 knockdown can induce emphysema by accelerating triglyceride deposition. Keywords: ABHD2 knockdown, Emphysema, ATGL, Triglyceride Deposition, lipid toxicity

Background Intravoxel incoherent motion (IVIM) tensor imaging is a promising technique for diagnosis and monitoring of cardiovascular diseases. Knowledge about measurement repeatability, however, remains limited. Purpose To evaluate short-term repeatability of IVIM tensor imaging in normal in vivo human hearts. Study type Prospective. Population Ten healthy subjects without history of heart diseases. Field strength/sequence Balanced steady-state free-precession cine sequence and single-shot spin-echo echo planar IVIM tensor imaging sequence (9 b-values, 0-400 seconds/mm2 and six diffusion-encoding directions) at 3.0 T. Assessment Subjects were scanned twice with an interval of 15 minutes, leaving the scanner between studies. The signal-to-noise ratio (SNR) was evaluated in anterior, lateral, septal, and inferior segments of the left ventricle wall. Fractional anisotropy (FA), mean diffusivity (MD), mean fraction (MF), and helix angle (HA) in the four segments were independently measured by five radiologists. Statistical tests IVIM tensor indexes were compared between observers using a one-way analysis of variance or between scans using a paired t-test (normal data) or a Wilcoxon rank-sum test (non-normal data). Interobserver agreement and test-retest repeatability were assessed using the intraclass correlation coefficient (ICC), within-subject coefficient of variation (WCV), and Bland-Altman limits of agreements. Results SNR of inferior segment was significantly lower than the other three segments, and inferior segment was therefore excluded from repeatability analysis. Interobserver repeatability was excellent for all IVIM tensor indexes (ICC: 0.886-0.972; WCV: 0.62%-4.22%). Test-retest repeatability was excellent for MD of the self-diffusion tensor (D) and MF of the perfusion fraction tensor (fp ) (ICC: 0.803-0.888; WCV: 1.42%-9.51%) and moderate for FA and MD of the pseudo-diffusion tensor (D* ) (ICC: 0.487-0.532; WCV: 6.98%-10.89%). FA of D and fp and HA of D presented good test-retest repeatability (ICC: 0.732-0.788; WCV: 3.28%-8.71%). Data conclusion The D and fp indexes exhibited satisfactory repeatability, but further efforts were needed to improve repeatability of D* indexes. Level of evidence 2 TECHNICAL EFFICACY: Stage 1.

BACKGROUND Non-monoexponential diffusion models are being used increasingly for the characterization and curative effect evaluation of hepatocellular carcinoma (HCC). But the fitting quality of the models and the repeatability of their parameters have not been assessed for HCC. PURPOSE To evaluate kurtosis, stretched exponential, and statistical models for diffusion-weighted imaging (DWI) of HCC, using b-values up to 2000 s/mm2 , in terms of fitting quality and repeatability. STUDY TYPE Prospective. POPULATION Eighteen patients with HCC. FIELD STRENGTH/SEQUENCE Conventional and DW images (b = 0, 200, 500, 1000, 1500, 2000 s/mm2 ) were acquired at 3.0T. ASSESSMENT The parameters of the kurtosis, stretched exponential, and statistical models were calculated on regions of interest (ROIs) of each lesion. STATISTICAL TESTS The fitting quality was evaluated through comparing the fitting residuals produced on the average data of ROI between different models using a paired t-test or Wilcoxon rank-sum test. Repeatability of the fitted parameters at the median values on the voxelwise data of ROI was assessed using the within coefficient of variation (WCV), the intraclass correlation coefficient (ICC), and the 95% Bland-Altman limits of agreements (BA-LA). The repeatability was divided into four levels: excellent, good, acceptable, and poor, referring to the values of ICC and WCV. RESULTS Among three models, the stretched exponential model provided the best fit to HCC (P < 0.05), whereas the statistical model produced the largest fitting residuals (P < 0.05). The repeatability of K from the kurtosis model was excellent (ICC 0.915; WCV 8.79%), while the distributed diffusion coefficient (DDC) from the stretched model was just acceptable (ICC 0.477; WCV 27.83%). The repeatability was good for other diffusion-related parameters. DATA CONCLUSION Considering the model fit and repeatability, the kurtosis and stretched exponential models are the preferred models for the description of the DW signals of HCC with respect to the statistical model. LEVEL OF EVIDENCE 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:297-304.

PURPOSE To investigate intravoxel incoherent motion (IVIM) tensor imaging of the in vivo human heart and elucidate whether the estimation of IVIM tensors is affected by the complexity of pseudo-diffusion components in myocardium. METHODS The cardiac IVIM data of 10 healthy subjects were acquired using a diffusion weighted spin-echo echo-planar imaging sequence along 6 gradient directions with 10 b values (0~400 s/mm2 ). The IVIM data of left ventricle myocardium were fitted to the IVIM tensor model. The complexity of myocardial pseudo-diffusion components was reduced through exclusion of low b values (0 and 5 s/mm2 ) from the IVIM curve-fitting analysis. The fractional anisotropy, mean fraction/mean diffusivity, and Westin measurements of pseudo-diffusion tensors (fp and D*) and self-diffusion tensor (D), as well as the angle between the main eigenvector of fp (or D*) and that of D, were computed and compared before and after excluding low b values. RESULTS The fractional anisotropy values of fp and D* without low b value participation were significantly higher (P < .001) than those with low b value participation, but an opposite trend was found for the mean fraction/diffusivity values. Besides, after removing low b values, the angle between the main eigenvector of fp (or D*) and that of D became small, and both fp and D* tensors presented significant decrease of spherical components and significant increase of linear components. CONCLUSION The presence of multiple pseudo-diffusion components in myocardium indeed influences the estimation of IVIM tensors. The IVIM tensor model needs to be further improved to account for the complexity of myocardial microcirculatory network and blood flow.

Non-monoexponential diffusion models are being used increasingly for the characterization and curative effect evaluation of hepatocellular carcinoma (HCC). But the fitting quality of the models and the repeatability of their parameters have not been assessed for HCC.To evaluate kurtosis, stretched exponential, and statistical models for diffusion-weighted imaging (DWI) of HCC, using b-values up to 2000 s/mmProspective.Eighteen patients with HCC.Conventional and DW images (b = 0, 200, 500, 1000, 1500, 2000 s/mmThe parameters of the kurtosis, stretched exponential, and statistical models were calculated on regions of interest (ROIs) of each lesion.The fitting quality was evaluated through comparing the fitting residuals produced on the average data of ROI between different models using a paired t-test or Wilcoxon rank-sum test. Repeatability of the fitted parameters at the median values on the voxelwise data of ROI was assessed using the within coefficient of variation (WCV), the intraclass correlation coefficient (ICC), and the 95% Bland-Altman limits of agreements (BA-LA). The repeatability was divided into four levels: excellent, good, acceptable, and poor, referring to the values of ICC and WCV.Among three models, the stretched exponential model provided the best fit to HCC (P0.05), whereas the statistical model produced the largest fitting residuals (P0.05). The repeatability of K from the kurtosis model was excellent (ICC 0.915; WCV 8.79%), while the distributed diffusion coefficient (DDC) from the stretched model was just acceptable (ICC 0.477; WCV 27.83%). The repeatability was good for other diffusion-related parameters.Considering the model fit and repeatability, the kurtosis and stretched exponential models are the preferred models for the description of the DW signals of HCC with respect to the statistical model.2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:297-304.