High-Resolution Diffusion Tensor MR Imaging for Evaluating Myocardial Anisotropy and Fiber Tracking at 3T: the Effect of the Number of Diffusion- Sensitizing Gradient Directions

다국어 초록 (Multilingual Abstract)

Objective: We wanted to evaluate the effect of the number of diffusion-sensitizing gradient directions on the image quality for evaluating myocardial anisotropy and fiber tracking by using in vitro diffusion tensor MR imaging (DT-MRI).
Materials and Methods: The DT-MR images, using a SENSE-based echoplanar imaging technique, were acquired from ten excised porcine hearts by using a 3T MR scanner. With a b-value of 800 s/mm2, the diffusion tensor images were obtained for 6, 15 and 32 diffusion-sensitizing gradient directions at the midventricular level. The number of tracked fibers, the fractional anisotropy (FA), and the length of the tracked fibers were measured for the quantitative analysis. Two radiologists assessed the image quality of the fiber tractography for the qualitative analysis.
Results: By increasing the number of diffusion-sensitizing gradient directions from 6 to 15, and then to 32, the FA and standard deviation were significantly reduced (p < 0.01), and the number of tracked fibers and the length of the tracked fibers were significantly increased (p < 0.01). The image quality of the fiber tractography was significantly increased with the increased number of diffusionsensitizing gradient directions (p < 0.01).
Conclusion: The image quality of in vitro DT-MRI is significantly improved as the number of diffusion-sensitizing gradient directions is increased.

다국어 초록 (Multilingual Abstract)

Objective: We wanted to evaluate the effect of the number of diffusion-sensitizing gradient directions on the image quality for evaluating myocardial anisotropy and fiber tracking by using in vitro diffusion tensor MR imaging (DT-MRI).
Materials and Methods: The DT-MR images, using a SENSE-based echoplanar imaging technique, were acquired from ten excised porcine hearts by using a 3T MR scanner. With a b-value of 800 s/mm2, the diffusion tensor images were obtained for 6, 15 and 32 diffusion-sensitizing gradient directions at the midventricular level. The number of tracked fibers, the fractional anisotropy (FA), and the length of the tracked fibers were measured for the quantitative analysis. Two radiologists assessed the image quality of the fiber tractography for the qualitative analysis.
Results: By increasing the number of diffusion-sensitizing gradient directions from 6 to 15, and then to 32, the FA and standard deviation were significantly reduced (p < 0.01), and the number of tracked fibers and the length of the tracked fibers were significantly increased (p < 0.01). The image quality of the fiber tractography was significantly increased with the increased number of diffusionsensitizing gradient directions (p < 0.01).
Conclusion: The image quality of in vitro DT-MRI is significantly improved as the number of diffusion-sensitizing gradient directions is increased.

참고문헌 (Reference)

1 장용민, "확산 경사자장의 방향수에 따른 분할 비등방성 뇌자기공명영상의 잡음에 대한 히스토그램 분석" 대한영상의학회 52 (52): 87-92, 2005

2 Jiang Y, "Transmural heterogeneity of diffusion anisotropy in the sheep myocardium characterized by MR diffusion tensor imaging" 293 : H2377-H2384, 2007

3 Pierpaoli C, "Toward a quantitative assessment of diffusion anisotropy" 36 : 893-906, 1996

4 Jones DK, "The effect of gradient sampling schemes on measures derived from diffusion tensor MRI: a Monte Carlo study" 51 : 807-815, 2004

5 Wu EX, "Study of myocardial fiber pathway using magnetic resonance diffusion tensor imaging" 25 : 1048-1057, 2007

6 Cercignani M, "Sensitivityencoded diffusion tensor MR imaging of the cervical cord" 24 : 1254-1256, 2003

7 Pruessmann KP, "SENSE: sensitivity encoding for fast MRI" 42 : 952-962, 1999

8 Jaermann T, "SENSE-DTI at 3 T" 51 : 230-236, 2004

9 Rademakers FE, "Relation of regional cross-fiber shortening to wall thickening in the intact heart. Three-dimensional strain analysis by NMR tagging" 89 : 1174-1182, 1994

10 Naganawa S, "Optimization of diffusion-tensor MR imaging data acquisition parameters for brain fiber tracking using parallel imaging at 3 T" 14 : 234-238, 2004

11 Lee JW, "Optimization of acquisition parameters of diffusion-tensor magnetic resonance imaging in the spinal cord" 41 : 553-559, 2006

12 Nagae-Poetscher LM, "Mori S. High-resolution diffusion tensor imaging of the brain stem at 3 T" 25 : 1325-1330, 2004

13 Taber LA, "Mechanics of ventricular torsion" 29 : 745-752, 1996

14 Spotnitz HM, "Macrodesign, structure, and mechanics of the left ventricle" 119 : 1053-1057, 2000

15 Wu EX, "MR diffusion tensor imaging study of postinfarct myocardium structural remodeling in a porcine model" 58 : 687-695, 2007

16 Choi SI, "Irreversibly damaged myocardium at MR imaging with a necrotic tissue-specific contrast agent in a cat model" 215 : 863-868, 2000

17 Edelman RR, "In vivo measurement of water diffusion in the human heart" 32 : 423-428, 1994

18 Reese TG, "Imaging myocardial fiber architecture in vivo with magnetic resonance" 34 : 786-791, 1995

19 Scollan DF, "Histological validation of myocardial microstructure obtained from diffusion tensor magnetic resonance imaging" 275 : H2308-H2318, 1998

20 Streeter DD Jr, "Fiber orientation in the canine left ventricle during diastole and systole" 24 : 339-347, 1969

21 Jeong AK, "Evaluation by contrast-enhanced MR imaging of the lateral border zone in reperfused myocardial infarction in a cat model" 2 : 21-27, 2001

22 Holmes AA, "Direct histological validation of diffusion tensor MRI in formaldehyde-fixed myocardium" 44 : 157-161, 2000

23 Okada T, "Diffusion-tensor fiber tractography: intraindividual comparison of 3.0-T and 1.5-T MR imaging" 238 : 668-678, 2006

24 Wu MT, "Diffusion tensor magnetic resonance imaging mapping the fiber architecture remodeling in human myocardium after infarction: correlation with viability and wall motion" 114 : 1036-1045, 2006

25 Tseng WY, "Diffusion tensor MRI of myocardial fibers and sheets: correspondence with visible cut-face texture" 17 : 31-42, 2003

26 Zhai G, "Comparisons of regional white matter diffusion in healthy neonates and adults performed with a 3.0-T head-only MR imaging unit" 229 : 673-681, 2003

27 Tseng WY, "Cardiac diffusion tensor MRI in vivo without strain correction" 42 : 393-403, 1999

28 Tanenbaum LN, "3-T MR imaging: ready for clinical practice" 25 : 1626-1627, 2004