Quasi-3D kinematic modeling and parametric image processing of a multiframe ECG-gated planar 99mTc-SestaMIBI myocardial perfusion scintigraphic study.

Abstract

BNORMALITIES of left ventricular (LV-) regional wall motion (RWM) and myocardial thickening, absolute LV-concentric orthogonal diameters (cords) and the corresponding chord-shortening fractions, circumferential midwall shortening velocities, etc are ordinarily estimated through echocardiographic measurements. Hov;:ever, there is ah increasing interest in extracting venti geometric information from planar as well as SPECT myocardial perfusion scintigrams (MPS). Although, multiframe electrocardiograph (ECG)-gated planar myocardial perfusion scintigraphy (Gp-MPS) is a very useful technique for combined evaluation of LV-hemodynamics (kinematics) and coronary blood flow (myocardial perfusional status) in ischemic heart disease/coronary artery disease, yet there is still no logical and consensus approach for extraction of kinematic information from Gp-MPS. This is partly because no proper kinematic analysis of Gp-MPS to assess spatio-temporal behavior of LV-systolic excursion has been worked out. Lack of in-depth understanding in regard to kinematic information contents (in the time and coordinate space) of Gp-MPS lead to confusion as to endocardial localization and myocardial kinematic analysis. We have developed a hybrid computational-mathematical model of left ventricular kinematics based on Gp-MPS. This model could be used for assessing LV-function in [-+x, _+y, 2z, t]-domain by parametric image processing to achieve quasi-3D functional maps/ images (Stroke-image, Phase-image, Amplitude-image and LV-Edge image) of various pathophysiological parameters of clinical importance in cardiology. Multidimentional analysis of an actual Gp-MPS based on this model has shown many hitherto unknown, yet clinically relevant facts about Gp-MPS. proximal half (O#p) anda distal one (~d) with respect to gamma-camera detector position. The shell is supposed to representan idealized diastolic myocardial wall containing a homogeneously dispersed radioactivity with count density Co > 1 Bq/mm 3. Blood, myocardium, and anterior chest wall have been assumed to be of uniform density with photon attenuation coefficient (q to be equivalent to that of water (ie, 0.0154/mm for 99mTc, 0.022/mm for 201-T1). The anterior chest-wall was supposed to have a uniform thickness (g) in z-direction (the direction of observation; bestseptal left-anterior oblique (BS-LAO) projection in actual scintigraphic settings) such that Co.e -~g = 1 Bq/mm 3, which is represented by 1 voxel mapped on a single pixel (x, y) with unit length and breadth, and having a z-directional unit uay-level (intensity) of the pixel of a picture tube. MTF(v) of the gamma camera system is assumed to be unity over the whole range of spatial frequencies (v) considered. Now, consideran upper right quadrant of a concentric one-pixel thick and circular (x, z)-slice of a sphere with radius Ro (Fig 1). The count rate profile mapped on a pixel-array (xi; i = 1, 2, 3 .... ) is given by, Zo(X )= \R o-x-; x<Ro