Traditional Posters: Body Imaging

Weiying Dai¹, Philip M. Robson¹, David C. Alsop<sup>1

1</sup>Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States

SSFP diffusion weighted imaging in the body can have improved image quality relative to echoplanar imaging. Its stronger diffusion attenuation of longer T2 fluid may also be a particular benefit in cancer screening studies, but the slow acquisition speed is a major limitation. Here we propose performing a diffusion weighted SSFP sequence as a preparation for a faster SSFSE sequence. The theoretical signal is described and pulse parameters are optimized. The resulting sequence is then applied to in-vivo diffusion weighted imaging of volunteers. Excellent suppression of fluid and blood signal is demonstrated.

2654. Monitoring Random Molecular Diffusion and Tissue Perfusion in Rat Liver by Diffusion Weighted Proton MRI

Beena George¹, Andriy Babsky¹, Navin Bansal<sup>1

1</sup>Radiology, Indiana University, Indianapolis, IN, United States

Diffusion weighted (DW) 1H MRI may be useful in the diagnosis of liver diseases. Fast and slow apparent diffusion coefficients (ADCfast and ADCslow, respectively) were separated in the normal rat liver by using ten b values. After mortal ischemia, ADCfast disappeared, demonstrating that this component results from microcapillary blood perfusion. ADCslow decreased after ischemia, most likely due to intracellular accumulation of water. DW 1H MRI can provide information about tissue perfusion and molecular diffusion which are both important physiological parameters.

2655. Improved Robustness with a Stretched Exponential Model for Intravoxel Incoherent Motion (IVIM) DW Signal

Yousef Mazaheri¹, Daniel B. Rowe², Jingbo Zhang³, Hedvig Hricak³, Jason A. Koutcher<sup>1

1</sup>Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States; ²Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, WI, United States; ³Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, United States

A stretched exponential model is presented to describe intravoxel incoherent motion (IVIM) signal. Simulations results show that the distributed diffusion coefficient and á is a dimensionless “stretching” parameter have tolerable CV (<15% at 5% noise) and bias (absolute bias< 11% at 5% noise). In vivo renal data suggests that the stretched exponential model has potential to describe the pseudo-diffusion behavior at low b-values.

2656. Relaxation Time Effects in Intra Voxel Incoherent Motion Imaging

Andreas Lemke¹, Frederik Bernd Laun², Dirk Simon³, Bram Stieltjes⁴, Lothar Rudi Schad<sup>1

1</sup>Department of Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany; ²Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; ³Software Development for Integrated Diagnostics and Therapy, German Cancer Research Center, Heidelberg; ⁴Department of Radiology, German Cancer Research Center, Heidelberg, Germany

The DWI signal was measured as a function of the b-value in the pancreas using three different echo times (TE=50, 70, 100 ms) from six healthy volunteers. A modified equation incorporating relaxation effects was introduced and parameters derived from this equation were compared to the original IVIM equation. The perfusion fraction f increased significantly with increasing echo time (P=0.0025) whereas the relaxation time compensated perfusion fraction f' showed no significant dependence on TE (P=0.31). The relaxation time compensation had no influence on the diffusion coefficients.

2657. Whole Body Diffusion Weighted Imaging for Distant Staging in Colorectal Cancer – Feasibility and Future Challenges

Doenja Lambregts¹, Monique Maas¹, Vincent Cappendijk¹, Jan Verwoerd², Iris Rutten¹, Geerard Beets³, Regina Beets-Tan<sup>1

1</sup>Radiology, Maastricht University Medical Center, Maastricht, Limburg, Netherlands; ²Philips Healthcare, Eindhoven, Netherlands; ³Surgery, Maastricht University Medical Center, Maastricht, Limburg, Netherlands

Whole-body diffusion weighted imaging (WB-DWI) could prove to be a promising and feasible alternative to CT and PET-CT for distant metastases screening in colorectal cancer. This study aims to test the feasibility of WB-DWI for metastases screening and to compare the lesion detectability of WB-DWI to conventional staging techniques (CT and PET-CT)

2658. Liver Diffusion/perfusion Using Biexponential Analysis with 30 B-Values

James Lee¹, Masoud Shiehmorteza¹, Michael E. Schroeder¹, Katie H. Hansen¹, Mark Bydder¹, Claude Sirlin<sup>1

1</sup>Radiology, University of California San Diego, San Diego, CA, United States

Diffusion imaging of the liver is reported as having slow and fast components ("perfusion"). We modeled both components before and after a meal to observe the effect of increasing perfusion.