Introduction

At present, pancreatic fibrosis and steatosis are important pathological processes of pancreatic injury repair caused by acute and chronic pancreatitis, pancreatic tumor and other diseases[1]. Novel quantitative MR imaging techniques such as DWI, IVIM, 3D mdixon-quant[2-3] can provide in vivo characterization of tissues and have the potential to be non-invasive biomarkers to diagnose certain solid organ pathologies. Quantitative imaging metrics can also be used to monitor the course of therapy in clinical trials. However, there are lack of data on normal quantitative metrics of the pancreas and correlation with obesity parameters (e.g. BMI(body mass index, BMI), TAT(total adipose tissue，SAT( subcutaneous adipose tissue) and VAT(visceral adipose tissue)).

Materials and methods

21 inpatients were included in this study, and underwent upper abdomen MRI scans (including 3D mDIXON-quant, DWI, IVIM) at 3.0T. Inpatients had the following characteristics: age range, 22-73 years (average, 53.90 ± 12,837years); BMI range, 18.73-35.75 kg/m2 (average, 24.18 ± 3.93 kg/m2); TAT range, 115.26-355.18 cm2 (average, 226.16 ± 68.90 cm2); SAT range, 48.80-191.44 cm2 (average, 104.72 ± 40.58 cm2); VAT range, 43.39 - 216.37 cm2 (average, 121.44 ± 51.75 cm2). 3D mDIXON-quant sequence scanning parameters：FOV=375mm, TR/TE=6.0/1.05ms, voxel size 2.3mm×1.8mm, slice thick 5.0/-2.5. DWI sequence scanning parameters：FOV=450mm, TR/TE=7700/74ms, voxel size 3.7mm×6.3mm, slice thick 6.0/0. IVIM sequence scanning parameters: FOV=400mm, TR/TE=3000/91ms, voxel size 3.0mm×2.5mm, slice thick 7.0/1.0. On ISP workstation, 2D region of interest (ROI) were placed on the head, body and tail regions of pancreas in DWI, IVIM and 3D mDIXON-quant, respectively(Fig.1). The mean value of three ROIs was calculated as the value of the whole pancreas. ROIs area were approximately 25-100 mm2. All ROIs were placed within the interested tissue by avoiding blood vessels, pancreatic duct and abdominal adipose tissue as much as possible. The TFA and VFA were measured using 3D mDIXON-quant at the level of L1-L2 using Image J (National Institutes of Health, USA). The regions with a fat fraction of >50% were marked red in the image. After manually placing the outlines in the abdominal wall and skeletal muscle, the TFA and VFA could be automatically calculated (Fig.2). The SFA equals to TFA minus VFA. The Spearman test was used to analyze the correlation between imaging parameters and BMI, SAT, VAT and TAT. This study has been approved by the local IRB.

Results

There was significant correlation between R2* and VAT, TAT (r=0.495,0.533, respectively). And, ADC was related to SAT (r=0.460). Other imaging parameters were not related with BMI, SAT, VAT and TAT(P>0.05).

Discussions

This study viewed that R2* was related to VAT and TAT, which demonstrated that central obesity may easily result in iron deposition of pancreas[4]. While there was a positive relationship between ADC and SAT. It may reveal that SAT may have a protective effect on the pancreas.

conclusion

This study measured the ADC, sADC, D*，D, f, FF and R2* of the pancreas in subjects with no pancreas disease. R2* was related to VAT and TAT, as the SAT increases, the ADC value decreases.

Acknowledgements

No acknowledgement found