| 翻訳と辞書 |
| Speckle tracking echocardiography ： ウィキペディア英語版 |
Speckle tracking echocardiography
In the fields of cardiology and medical imaging, Speckle Tracking Echocardiography (STE) is an echocardiographic imaging technique that analyzes the motion of tissues in the heart by using the naturally occurring speckle pattern in the myocardium or blood when imaged by ultrasonic. This novel method of documentation of myocardial motion represents a noninvasive method of definition of vectors and velocity. When compared to other technologies seeking noninvasive definition of ischemia, speckle tracking seems a valuable endeavor. This speckle pattern is a mixture of interference patterns and natural acoustic reflections. These reflections, also described as ‘‘speckles’’ or ‘‘markers’’. The pattern being random, each region of the myocardium, has a unique speckle pattern (also called ‘‘patterns’’, ‘‘features’’, or ‘‘fingerprints’’), that allows the region to be traced from one frame to the next, and this speckle pattern is relatively stable, at least from one frame to next.〔Bohs LN, Trahey GE. A novel method for angle independent ultrasonic imaging of blood flow and tissue motion. IEEE Trans Biomed Eng. 1991 Mar;38(3):280-6.〕〔Kaluzynski K, Chen X, Emelianov SY, Skovoroda AR, O'Donnell M. Strain rate imaging using two-dimensional speckle tracking. IEEE Trans Ultrason Ferroelectr Freq Control. 2001 Jul;48(4):1111-23.〕 In post processing this can be are tracked consecutively frame to frame and ultimately resolved into angle-independent two-dimensional (2D) and three-dimensional strain-based sequences (3D) 〔〔Leitman M, Lysyansky P, Sidenko S, Shir V, Peleg E, Binenbaum M, et al.Two-dimensional strain-a novel software for real-time quantitative echocardiographic assessment of myocardial function. JAm Soc Echocardiogr 2004;17:1021-9.〕 These sequences provide both quantitative and qualitative information regarding tissue deformation and motion.
==Basic principles==
As the speckle pattern is random, any region of the myocardium, has a unique speckle pattern: Within the picture, a defined area "kernel" can be defined, and as this speckle pattern is relatively stable, the kernel can be recognised in the next frame, within a larger search area, by a "best match" search algorithm. There are different search algorithms, the most commonly used is "sum of absolute differences",〔 shown to be similarly accurate as Cross-correlation, which is an alternative.〔Insana MF, Wagner RF, Garra BS, Momenan R, Shawker TH. Pattern recognition methods for optimizing multivariate tissue signatures in diagnostic ultrasound. Ultrason Imaging. 1986 Jul;8(3):165-80〕〔Bohs LN, Friemel BH, Trahey GE. Experimental velocity profiles and volumetric flow via two-dimensional speckle tracking. Ultrasound Med Biol. 1995;21(7):885-98〕 The movement of the kernel across the image can thus be tracked, in principle independent of the beam angle, as opposed to tissue Doppler. Specle tracking can thus track in two dimensions. However, at the axial (in the direction of the beam) resolution of the ultrasound is far better then the transverse, the tracking ability is less in the transverse direction. Also, the transverse resolution (and hence, tracking ability), decreases with depth, in a sector scan were ultrasound beams diverge.
Different commercial and non commercial operators then use different approaches to derive motion and deformation parameters. The motion of a single kernel can be resolved into displacement curves, and the distance between two kernels into strain (deformation).〔Ingul CB, Torp H, Aase SA, Berg S, Stoylen A, Slordahl SA. Automated analysis of strain rate and strain: feasibility and clinical implications. J Am Soc Echocardiogr. 2005 May;18(5):411-8.〕〔Amundsen BH, Crosby J, Steen PA, Torp H, Slørdahl SA, Støylen A. Regional myocardial long-axis strain and strain rate measured by different tissue Doppler and speckle tracking echocardiography methods: a comparison with tagged magnetic resonance imaging. Eur J Echocardiogr. 2009 Mar;10(2):229-37〕 Strain rate will then be time derivative of strain. In some commercial applications, the acoustic markers are tracked more individually, calculating the velocity from the motion and the sampling interval (inverse of frame rate) generating a velocity field.〔 Unlike Tissue Doppler, this velocity field in not limited to the beam direction. Strain rate and strain are then calculated from the velocities. Speckle tracking has been shown to be comparable to tissue Doppler derived strain,〔Modesto KM, Cauduro S, Dispenzieri A, Khandheria B, Belohlavek M, Lysyansky P, Friedman Z, Gertz M, Abraham TP.Two-dimensional acoustic pattern derived strain parameters closely correlate with one-dimensional tissue Doppler derived strain measurements. Eur J Echocardiogr. 2006 Aug;7(4):315-21〕 and has been validated against MR 〔〔Cho GY, Chan J, Leano R, Strudwick M, Marwick TH. Comparison of two-dimensional speckle and tissue velocity based strain and validation with harmonic phase magnetic resonance imaging. Am J Cardiol 2006; 97:1661-6〕〔Helle-Valle T, Crosby J, Edvardsen T, Lyseggen E, Amundsen BH, Smith HJ, Rosen BD, Lima JA, Torp H, Ihlen H, Smiseth OA. New noninvasive method for assessment of left ventricular rotation: speckle tracking echocardiography. Circulation. 2005 Nov 15;112(20):3149-56〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Speckle tracking echocardiography」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|