Body Diffusion: Beyond ADC?
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Tuesday May 10th
Room 518-A-C  13:30 - 15:30 Moderators: Dow-Mu Koh and Thomas C. Kwee

13:30 254.   Introduction
David J. Collins


13:42 255.   Short term measurement reproducibility of perfusion fraction (f), pseudo-diffusion coefficient (D*) and diffusion coefficient (D) in colorectal liver metastases derived by intravoxel incoherent motion analysis of respiratory-triggered diffusion-weighted MR imaging 
Adrian Andreou1, Matthew Orton2, David J Collins1,2, Martin O Leach2, and Dow-Mu Koh1
1Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom, 2CRUK-EPSRC Cancer Imaging Centre, Institute of Cancer Research, Sutton, Surrey, United Kingdom

Applying the principles of intravoxel incoherent motion (IVIM) allows quantitative parameters which reflect tissue microcapillary perfusion and tissue diffusivity to be derived. We evaluated the short term measurement reproducibility of the perfusion fraction (f), pseudo-diffusion (D*) and diffusion coefficients (D) of normal appearing liver and colorectal liver metastases in patients. We found that D showed good to moderate measurement reproducibility in liver and metastases. However, the reproducibility of f and D* was relatively poor but using a Bayesian method for analysis significantly improved the reproducibility of f and D* in metastases and D* in the liver.

13:54 256.   Intravoxel Incoherent Motion (IVIM) Analysis of Liver Fibrosis in an Experimental Mouse Model 
April M. Chow1,2, Darwin S. Gao1,3, Shu Juan Fan1,3, Gladys G. Lo4, Siu Ki Yu2, and Ed X. Wu1,3
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China, People's Republic of, 2Medical Physics & Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China, People's Republic of, 3Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China, People's Republic of, 4Department of Diagnostic and Interventional Radiology, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China, People's Republic of

Early diagnosis of liver fibrosis could facilitate early interventions and treatments, preventing its progression to cirrhosis. Recently, diffusing imaging has been shown to be promising in characterization of liver fibrosis. In this study, using intravoxel incoherent motion (IVIM) analysis and a mouse model of CCl4-induced fibrosis, we showed that both molecular water diffusion and blood microcirculation contribute to the alteration in apparent diffusion changes in liver fibrosis. Among all parameters studied, blood pseudodiffusion coefficient (D*) showed largest percentage change at 2 weeks after CCl4 insult. IVIM analysis can be valuable in characterizing liver fibrosis at early phase and monitoring its progression.

14:06 257.   Assessment of Hepatocellular Carcinoma in Fresh Liver Explants Using a Non-Gaussian Diffusion Kurtosis Model 
Andrew B Rosenkrantz1, Eric E Sigmund1, Benjamin E Niver1, Glyn R Morgan2, Bradley Spieler1, Anthony G Gilet1, and Cristina H Hajdu3
1Radiology, NYU Langone Medical Center, New York, New York, United States, 2Transplant Surgery, NYU Langone Medical Center, New York, New York, United States,3Pathology, NYU Langone Medical Center, New York, NY, United States

Eight fresh liver explants in patients with hepatocellular carcinoma (HCC) underwent ex-vivo 1.5T MRI, including diffusion kurtosis imaging (DKI). ADC using mono-exponential (ADC) and non-Gaussian (D) fit, as well as mean kurtosis (K), were calculated. There was significant correlation between ADC and D, but not between ADC or D with K. Relative contrast between liver and HCC was greater for K than for ADC or D. ADC and D were lowest in non-necrotic HCC, while K was not different between viable and necrotic HCC. Alternate diffusion protocols may have potential for DKI of HCC following chemo-embolization in a clinical setting.

14:18 258.   Histopathological correlation of IVIM-derived true diffusion constant in patients with pancreatic carcinoma and chronic pancreatitis 
Miriam Klauss1, Matthias Gaida2, Andreas Lemke3, Katharina Grünberg3, Dirk Simon3, Stefan Delorme3, Hans-Ulrich Kauczor2, Lars Grenacher2, and Bram Stieltjes3
1Diagnostic Radiology, University of Heidelberg, Heidelberg, Baden-Württemberg, Germany, 2University of Heidelberg, 3DKFZ

Fibrosis is the most characteristic histopathological feature of pancreatic carcinoma and chronic pancreatitis. It was shown that the IVIM-derived parameter D (true diffusion constant) did not show differences between these two entities. The aim of this study was to compare differences in D with the histopathological grade of fibrosis in pancreatic diseases. We compared the histopathological grade of fibrosis with the true diffusion constant D calculated from diffusion data in 24 patients. We found significant differences between the D-values for moderate and severe fibrosis. The pure diffusion constant could serve as parameter to monitor tumor response in pancreatic carcinoma.

14:30 259.   Association of the Apparent Diffusion Coefficient of Bladder Cancer with Metastatic Disease: Preliminary Results 
Thais C Mussi1, Bradley Spieler1, and Andrew B Rosenkrantz1
1Radiology, NYU Langone Medical Center, New York, New York, United States

19 patients with urothelial carcinoma of the bladder who underwent MRI including DWI at 1.5T were included. Among these, 8 had nodal or distant metastatic disease, and 11 had an absence of metastatic disease (mean follow-up 434 days). ADC was measured for each lesion and was significantly lower among those cases with metastatic disease (p=0.0012). Using ADC for prediction of metastatic disease, ROC analysis identified an AUC of 0.920, sensitivity of 87.5%, specificity of 100%, PPV of 100%, and NPV of 91.7%.

14:42 260.   Towards Repeatable ADC Mapping of the Liver: Some Guidance for Clinical Use 
Paul Summers1, Antonio Gregoraci2, Giuseppe Petralia1, Anna Caroli3, Roberto Di Filippi1, Luca Antiga3, and Massimo Bellomi1
1Department of Radiology, European Institute of Oncology, Milan, Italy, 2Faculty of Medicine and Surgery, University of Milan, Milan, Italy, 3Mario Negri Institute, Bergamo, Italy

We examined the impact of prandial status, choice of b-values in one or three directions, and ROI definition on repeatability of whole liver ADC measurements in 10 healthy subjects. The inclusion of the b=0 image or limiting the b-values used to those greater than 700 s/mm2 significantly increased both the estimated mean ADC and its variability between subjects. Excluding these choices of b-values, intra- and intersubject standard deviations were similar (< 10%, and 15-22% respectively) for both 1 and 3 encoding directions. Prandial status and exclusion of visible vessels from the ROI had little effect on ADC.

14:54 261.   Quantitative analysis of the diffusion-weighted steady-state free-precession signal in vertebral bone-marrow lesions 
Olaf Dietrich1, Andreas Biffar1, Andrea Baur-Melnyk2, Gerwin Schmidt2, and Maximilian F. Reiser1,2
1Josef Lissner Laboratory for Biomedical Imaging, Department of Clinical Radiology, Ludwig Maximilian University of Munich, Munich, Germany, 2Department of Clinical Radiology, Ludwig Maximilian University of Munich, Munich, Germany

Diffusion-weighted steady-state free-precession (DW-SSFP) sequences are extremely valuable for the differential diagnosis of benign osteoporotic and malignant neoplastic vertebral compression fractures. The purpose of the present study was to provide a detailed theoretical and experimental analysis of the DW-SSFP signal in the spine. It could be demonstrated that the main reasons for the different lesion contrasts are an opposed-phase readout in combination with the differing fat fractions and T2*-values in the fractures as well as in normal-appearing VBM of both entities. The observed signal contrast is therefore rather fat- and T2*-weighted than diffusion-weighted.

15:06 262.   Parallel RF excitation for diffusion-weighted whole body MR imaging with background body signal suppression at 3.0 Tesla  -permission withheld
G. M. Kukuk1, M. Kaschner1, F. Träber1, D. Skowasch2, J. Gieseke1,3, H. H. Schild1, W. A. Willinek1, and P. Mürtz1
1Department of Radiology, University of Bonn, Bonn, NRW, Germany, 2Department of Pneumology, University of Bonn, Bonn, Germany, 3Philips Healthcare, Best, Netherlands

High field MRI has introduced new challenges for DWIBS body imaging with respect to susceptibility artefacts, fat suppression, dielectric shading, and longer acquisition times. Dual-source parallel RF excitation has been shown to allow for a more homogeneous excitation. Therefore, we evaluated the effect of this technique on DWIBS in 40 patients. Shorter acquisition times by 33%, significantly improved signal homogeneity and fat suppression, and reduced dielectric shading without influencing ADC values was found by using parallel RF excitation in DWIBS at 3.0 T.

15:18 263.   Diffusion-Prepared Fast Imaging with Steady-State Free Precession (DP-FISP): A Rapid Diffusion MRI Technique at 7T 
Lan Lu1, Bernadette Erowku1, Gregory R Lee1, Katherine Dell2,3, and Chris A Flask1,4
1Radiology, Case Western Reserve University, Cleveland, OH, United States, 2Pediatrics, Case Western Reserve University, Cleveland, OH, United States, 3MetroHealth Medical Center, Cleveland, OH, United States, 4Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

Diffusion MRI applications typically utilize rapid Echo-Planar Imaging (EPI) acquisition techniques. However, EPI techniques are susceptible to off-resonance distortion and eddy current artifacts, especially for high field MRI applications. We have developed a rapid Diffusion Prepared - Fast Imaging with Steady-State Free Precession (DP-FISP) MRI acquisition for a 7T small animal MRI scanner that combines a diffusion preparation scheme with a rapid FISP imaging readout to provide diffusion-weighted images in less than 500 ms and DTI data (7 directions) in less than 1 minute. Herein, DP-FISP results validated in a water phantom and in vivo polycystic rat kidneys.