Quasi-3D kinematic modeling and parametric image processing of a multiframe ECG-gated planar 99m Tc-sestaMIBI myocardial perfusion scintigraphic study
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
Trajectory of left ventricular true endocardial edge on ECG-gated planar myocardial perfusion scintigraphy: geometric and kinematic implications in nuclear cardiac imaging
From rigorous theoretical and phantom studies, it was found that the true left ventricular endocardial edge coincides with the circumferential trajectory of radioactive count rate maxima of a planar gated myocardial perfusion scintigram. This should invoke a renewed interest in extracting geometric and kinematic information from nuclear (scintigraphic) images of the myocardium, as evidenced by preliminary clinical studies.
Mesozoic rifting and basin inversion along the northern African Tethyan margin: an overview
Abstract The northern African Tethyan margin registered three major rifting episodes from the latest Palaeozoic-earliest Mesozoic to the earliest Cenozoic. Break-up of Gondwana was initiated in the late Carboniferous. Along the northern African-Arabian plate margin rifting propagated westward from the northeastern Arabian margin to Morocco during the Permian and Triassic, and was accompanied by Mid-Late Triassic-earliest Liassic extensive alkaline flow basalts. Rifting continued during the Liassic, e.g. in the Moghrebian Atlas troughs. A second stage of rifting occurred in the Late Jurassic and continued into, or was rejuvenated during, the Early Cretaceous. Along the east Mediterranean margin, some large E-W trending rifts formed, often with associated volcanism, e.g. southern Sirt and Abu Gharadig. Most researchers believe the oceanization of the eastern Mediterranean basin occurred at this time. Flexural subsidence affected the Moghrebian Atlas, including the Riffian-Tellian domain, where a thick flysch series was deposited. Two short-lived, but widespread and tectonically important, compressional or wrench-dominated events occurred during the Santonian and the latest Maastrichtian. From Morocco to Oman, most sedimentary basins were folded and inverted at these times. The Santonian event resulted from onset of the collision between the African-Arabian and Eurasian plates. New stress-fields favoured NE-SW extension along the African plate margin, generating or rejuvenating some rifts, e.g. in the Euphrates trough and in the Libya-Tunisia region (northwestern Sirt, Pelagian Sea). Rifting and magmatism continued in these regions into the Paleocene. During the Mesozoic, therefore, the northern margin of the African-Arabian plate registered both rifting resulting in the oceanization of the Tethys and rifting resulting from the initiation of the closure of the Tethys. The intraplate domain exhibited echoes of the tectonic events affecting the margin.