Jie Deng

Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, United States

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Publications (6)11.36 Total impact

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    ABSTRACT: Background Brown adipose tissue (BAT) is identified in mammals as an adaptive thermogenic organ for modulation of energy expenditure and heat generation. Human BAT may be primarily composed of brown-in-white (BRITE) adipocytes and stimulation of BRITE may serve as a potential target for obesity interventions. Current imaging studies of BAT detection and characterization have been mainly limited to PET/CT. MRI is an emerging application for BAT characterization in healthy children. Objective To exploit Dixon and diffusion-weighted MRI methods to characterize cervical-supraclavicular BAT/BRITE properties in normal-weight and obese children while accounting for pubertal status. Materials and methods Twenty-eight healthy children (9–15 years old) with a normal or obese body mass index participated. MRI exams were performed to characterize supraclavicular adipose tissues by measuring tissue fat percentage, T2*, tissue water mobility, and microvasculature properties. We used multivariate linear regression models to compare tissue properties between normal-weight and obese groups while accounting for pubertal status. Results MRI measurements of BAT/BRITE tissues in obese children showed higher fat percentage (P
    No preview · Article · Jun 2015 · Pediatric Radiology
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    ABSTRACT: Background Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in children. The gold standard for diagnosis is liver biopsy. MRI is a non-invasive imaging method to provide quantitative measurement of hepatic fat content. The methodology is particularly appealing for the pediatric population because of its rapidity and radiation-free imaging techniques. Objective To develop a multi-point Dixon MRI method with multi-interference models (multi-fat-peak modeling and bi-exponential T2* correction) for accurate hepatic fat fraction (FF) and T2* measurements in pediatric patients with NAFLD. Materials and methods A phantom study was first performed to validate the accuracy of the MRI fat fraction measurement by comparing it with the chemical fat composition of the ex-vivo pork liver-fat homogenate. The most accurate model determined from the phantom study was used for fat fraction and T2* measurements in 52 children and young adults referred from the pediatric hepatology clinic with suspected or identified NAFLD. Separate T2* values of water (T2*W) and fat (T2*F) components derived from the bi-exponential fitting were evaluated and plotted as a function of fat fraction. In ten patients undergoing liver biopsy, we compared histological analysis of liver fat fraction with MRI fat fraction. Results In the phantom study the 6-point Dixon with 5-fat-peak, bi-exponential T2* modeling demonstrated the best precision and accuracy in fat fraction measurements compared with other methods. This model was further calibrated with chemical fat fraction and applied in patients, where similar patterns were observed as in the phantom study that conventional 2-point and 3-point Dixon methods underestimated fat fraction compared to the calibrated 6-point 5-fat-peak bi-exponential model (P
    No preview · Article · May 2014 · Pediatric Radiology
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    ABSTRACT: Phase contrast magnetic resonance imaging (MRI) is a powerful tool for evaluating vessel blood flow. Inherent errors in acquisition, such as phase offset, eddy currents and gradient field effects, can cause significant inaccuracies in flow parameters. These errors can be rectified with the use of background correction software. To evaluate the performance of an automated phase contrast MRI background phase correction method in children and young adults undergoing cardiac MR imaging. We conducted a retrospective review of patients undergoing routine clinical cardiac MRI including phase contrast MRI for flow quantification in the aorta (Ao) and main pulmonary artery (MPA). When phase contrast MRI of the right and left pulmonary arteries was also performed, these data were included. We excluded patients with known shunts and metallic implants causing visible MRI artifact and those with more than mild to moderate aortic or pulmonary stenosis. Phase contrast MRI of the Ao, mid MPA, proximal right pulmonary artery (RPA) and left pulmonary artery (LPA) using 2-D gradient echo Fast Low Angle SHot (FLASH) imaging was acquired during normal respiration with retrospective cardiac gating. Standard phase image reconstruction and the automatic spatially dependent background-phase-corrected reconstruction were performed on each phase contrast MRI dataset. Non-background-corrected and background-phase-corrected net flow, forward flow, regurgitant volume, regurgitant fraction, and vessel cardiac output were recorded for each vessel. We compared standard non-background-corrected and background-phase-corrected mean flow values for the Ao and MPA. The ratio of pulmonary to systemic blood flow (Qp:Qs) was calculated for the standard non-background and background-phase-corrected data and these values were compared to each other and for proximity to 1. In a subset of patients who also underwent phase contrast MRI of the MPA, RPA, and LPA a comparison was made between standard non-background-corrected and background-phase-corrected mean combined flow in the branch pulmonary arteries and MPA flow. All comparisons were performed using the Wilcoxon sign rank test (α = 0.05). Eighty-five children and young adults (mean age 14 years; range 10 days to 32 years) met the criteria for inclusion. Background-phase-corrected mean flow values for the Ao and MPA were significantly lower than those for non-background-corrected standard Ao (P = 0.0004) and MPA flow values (P < 0.0001), respectively. However, no significant difference was seen between the standard non-background (P = 0.295) or background-phase-corrected (P = 0.0653) mean Ao and MPA flow values. Neither the mean standard non-background-corrected (P = 0.408) nor the background-phase-corrected (P = 0.0684) Qp:Qs was significantly different from 1. However in the 27 patients with standard non-background-corrected data, the difference between the Ao and MPA flow values was greater than 10%. There were 19 patients with background-phase-corrected data in which the difference between the Ao and MPA flow values was greater than 10%. In the subset of 43 patients who underwent MPA and branch pulmonary artery phase contrast MRI, the sum of the standard non-background-corrected mean RPA and LPA flow values was significantly different from the standard non-background-corrected mean MPA flow (P = 0.0337). The sum of the background-phase-corrected mean RPA and LPA flow values was not significantly different from the background-phase-corrected mean MPA flow value (P = 0.1328), suggesting improvement in pulmonary artery flow calculations using background-phase-correction. Our data suggest that background phase correction of phase contrast MRI data does not significantly change Qp:Qs quantification, and there are residual errors in expected Qp:Qs quantification despite background phase correction. However the use of background phase correction does improve quantification of MPA flow relative to combined RPA and LPA flow. Further work is needed to validate these findings in other patient populations, using other MRI units, and across vendors.
    No preview · Article · Dec 2013 · Pediatric Radiology
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    ABSTRACT: The purpose was to propose and evaluate a semiautomatic postprocessing method to measure liver R2(⁎) values in patients with a broad range of liver iron content. Multiecho gradient echo magnetic resonance images were acquired in patients diagnosed with thalassemia or other types of congenital anemias. Liver R2(⁎) values were measured using a routine manually defined region-of-interest (mROI) method and a semiautomatic (SA) method. In the semiautomatic method, pixelwise (pSA) and averaged (aSA) signal fitting was performed on the segmented liver tissues after hepatic vessel extraction. The pixelwise fitting approach resulted in a liver R2(⁎) map with an overlay of nonfitted pixels associated with noise performance. The following aSA approach derived overall R2(⁎) by fitting the averaged signal intensities of all pixels within the liver ROI excluding vessels and nonfitted pixels. The measurement accuracy and interobserver agreement using mROI and the two semiautomatic approaches (pSA and aSA) were evaluated. In a total of 45 exams with R2(⁎) ranging from 30 to 1500 s(-1), the R2(⁎) measurements using all three methods were overall highly correlated and concordant with each other. R2(⁎) values measured by aSA were consistently higher than those measured by mROI. At lower R2(⁎) (<1000 s(-1)), R2(⁎) values measured by pSA were consistent with aSA but higher than mROI; with increasing R2(⁎), the pSA method became less stable and underestimated R2(⁎) due to increased noise level. The interobserver agreement was higher for the aSA method compared to pSA and mROI. The semiautomatic postprocessing method provides a promising tool for reliable liver R2(⁎) measurement with additional information for overall evaluation of iron distribution and measurement confidence. This method may offer the potential of reducing interoperator variability and improving diagnostic confidence in patients with liver iron overload.
    No preview · Article · Mar 2012 · Magnetic Resonance Imaging
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    ABSTRACT: PURPOSE To implement a semi-automatic post-processing method to evaluate liver R2* values in patients with liver iron overload and to compare this method with a manually defined multiple regions-of-interest (mROIs) method. METHOD AND MATERIALS Liver MRI was performed in 10 patients using a multi-echo GRE sequence: FOV=30-40cm,TR=30ms, matrix=128,BW=1950Hz/px,4 slices,2 acquisitions (8 echoes per acquisition) with interleaved TEs within one breathold (#1:TE=0.99-7.29ms, #2:TE=1.49-7.79ms, ΔTE=0.99ms). Image processing was implemented offline using Matlab. (1) A ROI was drawn on each slice to outline the entire liver. (2) Pixel by pixel T2* was calculated by fitting a mono-exponential signal decay model without data truncation; pixels not be fitted were temporally excluded. (3) A T2* histogram was generated and a threshold was defined to segment vessels and surrounding tissues from liver. (4) Mean liver signal decay was plotted as a function of TE, based on which the noise baseline was determined. (5) Pixel by pixel T2* of the liver was calculated after truncating data points within 20% of the baseline. (6) Determined the poorly fitted pixels with standard deviation (SD) of errors>10%. (7)After excluding all non-fitted and poorly fitted pixels, mean and SD of R2* (1/T2*) over all pixels of all slices were calculated. Resultant R2* were compared to values obtained from mROI’s drawn attempting to avoid vessels and liver periphery. RESULTS In 8 patients with R2*>200Hz, whole liver R2* were higher than mROI R2* by 2.4%~14% (8±4.2%). In 2 patients with R2*<200Hz, whole liver R2* were slightly lower than mROI R2* (1.8%, 5.2%). Higher whole liver R2* are attributed to exclusion of vessels and possible partial volume effects of other tissues. Liver tissues with lower R2* demonstrated fewer poorly/non-fitted pixels located at the edge of the liver or vessels. In contrast, in patients with extremely high iron load the parametric T2* maps showed many poorly/non-fitted pixels caused by decreased SNR and inadequate data points used for parameter fitting. CONCLUSION This semi-automatic method for whole liver R2* measurement eliminates contamination of vessel signal and poorly/non-fitted pixels. This may provide more accurate R2* measurements and improve diagnostic confidence. CLINICAL RELEVANCE/APPLICATION This method may provide accurate assessment of liver iron content and potentially improve workflow while reducing intra/inter-operator differences.
    No preview · Conference Paper · Nov 2010
  • Source

    Full-text · Article · Jan 2010 · Journal of Cardiovascular Magnetic Resonance

Publication Stats

8 Citations
11.36 Total Impact Points


  • 2013-2015
    • Ann & Robert H. Lurie Children's Hospital of Chicago
      Chicago, Illinois, United States
  • 2010-2012
    • Children's Memorial Hospital
      Chicago, Illinois, United States