Myocardial volume perfused by coronary artery branches--a three-dimensional x-ray CT evaluation in human cadaver hearts

An integrated mathematical model of the human cardiopulmonary system: model development

Several cardiovascular and pulmonary models have been proposed in the last few decades. However, very few have addressed the interactions between these two systems. Our group has developed an integrated cardiopulmonary model (CP Model) that mathematically describes the interactions between the cardiovascular and respiratory systems, along with their main short-term control mechanisms. The model has been compared with human and animal data taken from published literature. Due to the volume of the work, the paper is divided in two parts. The present paper is on model development and normophysiology, whereas the second is on the model's validation on hypoxic and hypercapnic conditions. The CP Model incorporates cardiovascular circulation, respiratory mechanics, tissue and alveolar gas exchange, as well as short-term neural control mechanisms acting on both the cardiovascular and the respiratory functions. The model is able to simulate physiological variables typically observed in adult humans under normal and pathological conditions and to explain the underlying mechanisms and dynamics.

Functional anatomy and hemodynamic characteristics of vasa vasorum in the walls of porcine coronary arteries

In this study vasa vasorum in the walls of porcine coronary arteries were examined, using three-dimensional (3D) micro-CT scanning techniques. These techniques leave the 3D structure of the vasa vasorum tree intact and thus provide a much more direct view of this structure than is possible from conventional histological sections. The study demonstrates-for the first time, we believe-both the different types and the fine architecture of these vasa vasorum. Furthermore, with the use of automated tree analysis software, it was possible to obtain quantitative geometrical data on the 3D structure of vasa vasorum trees that have not previously been available. The results indicate that despite the restrictive topology of the space in which they are present, the branching architecture of the vasa vasorum trees, which we surveyed, is surprisingly similar to that of vasculature in general. The volume of vessel wall tissue perfused or drained by a vasa vasorum tree was found to correlate well with the cross-sectional area of the root segment of the vasa vasorum tree, and the luminal surface area corresponding to this volume was found to be comparable with the surface area of an early atherosclerotic lesion. This is consistent with earlier findings that the ligation or removal of vasa vasorum leads to atherogenesis.

Anatomy of the human biliary system studied by quantitative computer-aided three-dimensional imaging techniques

The branching geometry of the normal, cholangiographically identifiable human biliary tree was studied with an innovative computer-aided three-dimensional (3D) imaging technique. In addition, a serially sectioned conventional paraffin block from a normal donor liver was used to create and quantitatively study a microscopic 3D image. Finally, a geometric model was developed to estimate the enlargement of biliary surfaces imparted by microvilli. The images created by these techniques could be viewed in stationary modes or rotating around any preselected axis. Approximately 7 (+/-3) intrahepatic duct orders were cholangiographically identified. Computerized measurements of the images from three normal livers suggested that the mean total volume of duct orders 1 to 7 shown in the cholangiograms was 16.6 cm3. The volume of the entire macroscopic duct system was estimated to be between 14 and 24 cm3 (mean, 20.4 cm3), with an internal surface of 336 to 575 cm2 (mean, 398 cm2). A geometric model based on electron micrographs suggested that this surface is magnified approximately 5.5-fold by the presence of microvilli. Volume and surface area (SA) measurements of all ducts in the same orders increased nearly exponentially from the first toward the seventh branching order (i.e., from the hilus toward the periphery of the liver), and probably beyond. The microscopic computerized reconstruction of a septal bile duct with its tributaries also allowed volume measurements; the imaged duct system represented 2.7% of the portal tract volume. The data presented herein may help to better evaluate branching patterns of the biliary tree and, eventually, the quantitative aspects of site-restricted cholangiocyte function and their role in the development of biliary diseases.

Coronary artery mapping: a method for three-dimensional reconstruction of epicardial anatomy

Evaluation of coronary anatomy with conventional coronary angiography requires visual integration of multiple images from different viewing orientations to generate a mental interpretation of three-dimensional (3D) structure. The epicardial surface is, in many ways, analogous to the earth's surface topography and may be effectively depicted using cartographic methods. To show coronary anatomy visualized as topographic maps, we used cartographic projection methods to analyze the coronary vessels of a canine heart after immediate postmortem injection with a radio-opaque gelatinous solution. A volumetric image data set was obtained with x-ray spiral computed tomography. The principal axis of the image volume was calculated and the image volume reformatted to a reference coordinate system defined by the principal axis as the ordinate. A cylindrical projection map of the epicardial surface was created using a maximum-intensity projection volume-rendering technique. After converting the Cartesian reference coordinate system to a polar coordinate system, additional mapping projections from user-defined orientations were generated. The results show that interpretative difficulties of coronary angiography may be diminished by generating 3D maps of coronary anatomy using volumetric datasets acquired noninvasively and displayed with cartographic methods.

Lumen centerline detection in complex coronary angiograms

We have developed a method for lumen centerline detection in individual coronary segments that is based on simultaneous detection of the approximate positions of the left and right coronary borders. This approach emulates that of a clinician who visually identifies the lumen centerline as the midline between the simultaneously-determined left and right borders of the vessel segment of interest. Our lumen centerline detection algorithm and two conventional centerline detection methods were compared to carefully-defined observer-identified centerlines in 89 complex coronary images. Computer-detected and observer-defined centerlines were objectively compared using five indices of centerline position and orientation. The quality of centerlines obtained with the new simultaneous border identification approach and the two conventional centerline detection methods was also subjectively assessed by an experienced cardiologist who was unaware of the analysis method. Our centerline detection method yielded accurate centerlines in the 89 complex images. Moreover, our method outperformed the two conventional methods as judged by all five objective parameters (p < 0.001 for each parameter) and by the subjective assessment of centerline quality (p < 0.001). Automated detection of lumen centerlines based on simultaneous detection of both coronary borders provides improved accuracy in complex coronary arteriograms.

Myocardial risk area defined by technetium-99m sestamibi imaging during percutaneous transluminal coronary angioplasty: comparison with coronary angiography

OBJECTIVES

The purpose of this study was to compare the assessment of myocardial area at risk in patients with coronary artery stenosis by coronary angiography and quantitative myocardial perfusion imaging with technetium-99m sestamibi.

BACKGROUND

Decisions concerning patient management frequently rely on semiquantitative angiographic estimation of the myocardial area at risk, although this approach has not been well validated. Technetium-99m sestamibi is a perfusion imaging agent with little redistribution after initial myocardial uptake. This characteristic allows for injection during angioplasty and later imaging for visualization and quantitation of the nonperfused area at risk.

METHODS

Thirty-nine patients referred for coronary angioplasty were studied. Technetium-99m sestamibi was injected intravenously during angioplasty balloon inflation. Planar (33 patients) or tomographic (6 patients) imaging was performed after completion of angioplasty. Imaging was repeated 24 to 48 h later. Myocardial risk area (perfusion defect on angioplasty image) was quantified as an integral using circumferential count distribution profiles and normal reference. Angiographic risk area was assessed using five scoring methods.

RESULTS

The scintigraphic risk area was 14 +/- 15 on planar images and 39 +/- 16 on tomography. Scintigraphic risk area of patients with infarction was larger than in patients without (22 +/- 17 versus 7 +/- 8, p = 0.003). The left anterior descending coronary artery had a larger mean risk area than other vessels (22 +/- 15 versus 7 +/- 11, p = 0.002). The presence of angiographic collateral channels was associated with smaller risk areas. Angiographic risk scores correlated only moderately with the technetium-99m sestamibi risk area (r = 0.54 to 0.65), with considerable spread of data.

CONCLUSIONS

Area at risk estimated from coronary angiography does not correlate well with that from quantitative myocardial perfusion imaging with technetium-99m sestamibi. These findings emphasize that the functional significance of coronary artery disease is not predicted by coronary anatomy alone.

Rationale for, and recent progress in, 3D reconstruction of the heart and lungs

Three-dimensional information of the structure and function of the heart and lungs is needed for several reasons including the following: (a) An apparent change in shape or location of the imaged ventricular wall may either be due to the heart moving through the imaged region, or because it truly represents that change in geometry, or a mixture of the two. In addition, as diseases of the heart and lungs are often heterogeneous in their spatial distribution, we expect the structural and functional consequences to also be heterogeneous in their spatial distribution; (b) Comparison of a selected anatomic feature (e.g., a coronary artery stenosis or pulmonary opacity) at long time intervals may make detection and/or quantitation of lesion progression questionable. The use of a 3D reconstruction to calculate a projection image with a reproducible angle of view is a particularly powerful consequence of 3D image reconstruction; (c) Use of image information from one imaging modality helps improve the quantitative characteristics of an image generated with another imaging modality; (d) Radiation treatment planning requires knowledge of the 3D distribution of radiation attenuation coefficients so that 3D distribution of the regional deposition of radiation energy can be quantitated; (e) Allows for indirect estimation of the physiological dimensions of one aspect of an organ so that the degree of disease of that part of the organ can be assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

Shape-based interpolation of tree-like structures in three-dimensional images

Many three-dimensional (3-D) medical images have lower resolution in the z direction than in the x or y directions. Before extracting and displaying objects in such images, an interpolated 3-D gray-scale image is usually generated via a technique such as linear interpolation to fill in the missing slices. Unfortunately, when objects are extracted and displayed from the interpolated image, they often exhibit a blocky and generally unsatisfactory appearance, a problem that is particularly acute for thin treelike structures such as the coronary arteries. Two methods for shape-based interpolation that offer an improvement to linear interpolation are presented. In shape-based interpolation, the object of interest is first segmented (extracted) from the initial 3-D image to produce a low-z-resolution binary-valued image, and the segmented image is interpolated to produce a high-resolution binary-valued 3-D image. The first method incorporates geometrical constraints and takes as input a segmented version of the original 3-D image. The second method builds on the first in that it also uses the original gray-scale image as a second input. Tests with 3-D images of the coronary arterial tree demonstrate the efficacy of the methods.