L. Axel and L. Dougherty, "Heart wall motion: Improved method of spatial modulation of magnetization for MR imaging," Radiology 172(1), pp. 349--350, 1989.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... 1: A typical first frame of an MRI SPAMM image sequence of the left ventricle (short axis) 1 Introduction A non invasive method for monitoring the deformation of the heart wall is by tagged Magnetic Resonance Imaging (MRI) often called MRI SPAMM (SPAtial Modulation of Magnetization) images [1]. A typical MRI SPAMM initial frame of the left ventricle is shown in Fig. 1. The dark lines forming the grid are tagged to the material points (in planes perpendicular to the imaging plane) and as such follow the material points through time. In subsequent time frames, the contrast between the ....

L. Axel and L. Dougherty, "Heart wall motion: Improved method of spatial modulation of magnetization for MR imaging," Radiology, vol. 172, pp. 349--350, 1989.

....part of the underlying physics and imaging process. In some applications, however, it is possible to control this brightness function. For example, consider the estimation of left ventricular motion from a sequence of magnetic resonance (MR) images of the heart. Recent developments in MR tagging [17, 18, 19, 20] make it possible to modulate the MRI brightness function to make a spatial pattern appear in otherwise homogeneous tissue (see Section VI for more information) Prince et al. 21, 22, 23, 24] have shown that such patterns can be exploited using optical flow processing to detect motion that would ....

....may be changed by injecting dyes and biomechanical studies of limb motion where the brightness function may be changed by painting the body. In MR tagging applications, the spatially modulated magnetization (SPAMM) brightness function can be applied to a given tissue using a standard MR scanner [18, 19, 24]. The SPAMM brightness function is similar to the product of sinusoids pattern used in this paper and can be parameterized by spatial frequency. In separate simulation experiments we have shown that an optimal spatial frequency exists for SPAMM and the optimization methods presented in this paper ....

L. Axel and L. Dougherty. Heart wall motion: improved method of spatial modulation of magnetization for MR imaging. Radiology, 172:349, 1989.

....still too large. Another important criterion, especially for motion analyses, is the ability to obtain data correspondence between the images taken at subsequent time phases. Recently, the introduction of a new technology in Magnetic Resonance Imaging (MRI) in conjunction with magnetic tagging [6, 116] has provided a potentially powerful tool for the study of heart wall motion. The MR tagging method provides a means to noninvasively mark and track a number of material points, and therefore provides a temporal correspondence for the material points on featureless structures like the heart wall. ....

....[60, 63] where the volumetric primitives are converted into models that deform due to forces exerted by the data points. In order to capture the twisting motion of the LV, we have utilized the data obtained from the MR tagging technique known as SPAMM (SPAtial Modulation of Magnetization) [6]. This fast, non invasive technique promises to be very useful in the analysis of heart wall motion because it provides temporal correspondence for material points within the heart wall. The crucial advantage of using the proposed DMPF in conjunction with tagged MRI data is that with a small ....

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L. Axel and L. Dougherty. Heartwall motion: Improved method of spatial modulation of magnetization for MR imaging. Radiology, 172:349--350, 1989.

....of each material point p and must satisfy jf 0 (p)j 1. The design of tagging sequences for creative tag patterns has received much attention in the literature (e.g. 1, 14, 15] but the most commonly used sequence produces the relatively simple spatial modulation of magnetization (SPAMM) pattern [2, 16]. SPAMM tag patterns are imposed by applying a sequence of N hard RF pulses, generally with different tip angles. Between the RF pulses, a gradient pulse with integrated magnitude and direction 1 fl g is applied, where fl is the gyromagnetic ratio. The whole sequence is then followed by a ....

L. Axel and L. Dougherty. Heart wall motion: improved method of spatial modulation of magnetization for MR imaging. Radiology, 172:349, 1989.

....the simple tracking scheme employed in this paper estimates the tangential component of the surface velocity field much less reliably than the normal component. A more accurate estimation of the tangential component would require additional data or a priori information. For example, SPAMM images [27] depict transient magnetic tags within the heart wall whose motion can be followed over several subsequent images, providing both orthogonal components of the local velocity in the image plane [28] Our model can readily assimilate this type of information and that available from other sources. ....

L. Axel and L. Dougherty. Heart Wall Motion: Improved Method of Spatial Modulation of Magnetization for MR Imaging. Radiology, 172:349--350, 1989.

....depicting changes in the data during systole. 1 2 Background 2.1 Previous Work Numerous techniques that use tagged MR images to study heart mechanics have been developed over the past 10 years. We briefly describe those that are most closely related to our intersection tracking algorithm. Axel and Dougherty (1989) first introduced the idea of tracking a tag grid, in their case a 2 D grid within a 2 D image plane. We have extended this idea to 3 D, to capture the complete motion of cardiac material points which generally move through image planes. Because our intersections are not confined to image planes, ....

....the image plane orientation and thickness, pixel size, tag pattern, T 1 , T 2 , and proton density. We chose four SA image planes with an 8 mm separation and six LA image planes with a 30 ffi separation. The tag pattern was generated using a one dimensional 1 2 1 binomial SPAMM sequence (Axel and Dougherty, 1989) with a tag spacing of approximately 6 mm. The pixel size was 1.25 mm and the slice thickness was 5 mm. These parameters are consistent with typical tagged MR studies, except such studies generally use at least 6 SA image planes. We chose 4 SA image planes encompassing a 24 mm slab of the model as ....

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Axel, L. and Dougherty, L. (1989). Heart wall motion: improved method of spatial modulation of magnetization for MR imaging. Radiology, 172:349.

....field. This technique is particularly promising because it avoids the aperture problem altogether, but velocity images are noisy and take longer to acquire than other techniques [3] MR Tagging The image intensity inside the LV wall can be altered non invasively with a technique called MR tagging [20, 21, 22, 23, 24]. Tagged images appear with a spatially encoded pattern that moves with the heart tissue as it moves through the cardiac cycle. The tag pattern creates intensity gradients in the otherwise homogeneous intensity in the LV wall, and as a result alleviates the effects of the aperture problem. For ....

....Initial tagged heart image. d) Deformed tagged heart image. a) b) c) d) Figure 1.12: a) Initial untagged heart image. b) Deformed untagged heart image. c) Initial tagged heart image. d) Deformed tagged heart image. tag patterns can be generated with this technique such as grid patterns [21, 22] and radial line patterns [20, 23] Sinusoidal tag patterns like the one shown in Figure 1.12 can be generated by continuously modulating the magnitude of the spin vector M 0 with a technique called spatial modulation of magnetization (SPAMM) 21, 22] An example of a SPAMM tagging pulse sequence ....

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L. Axel and L. Dougherty. Heart wall motion: improved method of spatial modulation of magnetizati on for MR imaging. Radiology, 172:349, 1989. 192

....perimysial collagen. Thus there is a clear need for non invasive techniques when estimating material properties. Currently the most promising source of non invasive experimental data is from a magnetic resonance imaging (MRI) tagging technique known as spatial modulation of magnetisation (SPAMM) [10, 11]. Using this procedure, three dimensional coordinates of material points within the heart walls are tracked during the heart cycle. Unloaded and deformed heart geometries are then fitted to the measured heart geometries from SPAMM using a finite element model [12] In addition, the left and right ....

Axel, L. and Dougherty, L., August 1989, Heart wall motion: Improved method of spatial modulation of magnetization for MR imaging, Radiology, Vol. 172, pp. 349--350.

....cycle in which a displacement field estimate is desired. It should be noted that although we develop our measurement model in the context of the parallel tag plane technique of O Dell et al. 7] 8] the concepts are the same for the tagging geometries of Zerhouni [1] 6] and Young and Axel [2] [20], 9] The tag lines in each image are tracked within the segmented myocardium using a method such as that proposed by Guttman et al. 3] or Kumar and Goldgof [4] A tracked tag defines the intersection of a deformed tag plane within the image plane, as shown in Figure 4. A point r on a tracked ....

L. Axel and L. Dougherty, "Heart wall motion: improved method of spatial modulation of magnetization for MR imaging ", Radiology, vol. 172, pp. 349, 1989.

....are based on the use of parameters that are either too complex or too few to be used by a physician. Recently, a new magnetic resonance imaging (MRI) technique based on magnetic tagging (MRI SPAMM) has been developed at the University of Pennsylvania for imaging of regional heart wall motion (Axel and Dougherty, 1989). This fast, non invasive technique promises to be very useful in the analysis of heart wall motion because it provides temporal correspondence of material points within the heart wall. This correspondence, in conjunction with the use of the threedimensional (3D) location of each tagged datum, can ....

.... Harrison et al. 1963; Meier et al. 1980) lead beads (Waldman et al. 1985) or ultrasonic crystals (Rankin et al. 1976; Villarreal et al. 1988) use of naturally occurring landmarks (Chen and Huang, 1990; Kim et al. 1985; Young, 1991; Young et al. 1992) and magnetic resonance (MR) tagging (Axel and Dougherty 1989; Azhari et al. 1992; Denney and Prince, 1994; Fischer et al. 1994; Moore et al. 1992; Zerhouni et al. 1988) Although the implantation methods have been used for the LV motion analysis, and provide accurate localization, the invasive nature of the procedures does not allow a sufficient number ....

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Axel L., Dougherty L., (1989) "Heart wall motion: Improved method of spatial modulation of magnetization for MR imaging," Radiology, 172, 349-350.

....cardiac imaging methods in terms of providing good datasets for motion studies, and 2) the absence of computational techniques for automatic extraction of the three dimensional (3D) heart wall motion parameters in a way that is useful to physicians. Recently, the introduction of magnetic tagging [2], 39] in Magnetic Resonance Imaging (MRI) has provided a powerful tool to study the heart wall motion. J. Park and D. Metaxas are with the Department of Computer Information Science at the University of Pennsylvania, Philadelphia, PA 19104 6389 USA; E mail: jinah graphics.cis.upenn.edu or ....

L. Axel, L. Dougherty, "Heart wall motion: Improved method of spatial modulation of magnetization for MR imaging," Radiology, vol. 172, pp. 349-350, 1989.

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L. Axel and L. Dougherty, "Heart wall motion: Improved method of spatial modulation of magnetization for MR imaging," Radiology 172(1), pp. 349--350, 1989.

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