Jeou-Jong Shyu

Polarization-sensitive optical coherence tomography for imaging human atherosclerosis

Polarization-sensitive optical coherence tomography (PS-OCT) combines the advantages of OCT with image contrast enhancement, which is based on its ability to detect phase retardation and the fast-axis angle. Both PS-OCT images and histopathology have demonstrated similar features that allowed differentiation of atherosclerotic structures (i.e., plaques) from normal tissue. Moreover, the picrosirius polarization method was used to confirm PS-OCT assessment of collagen in the fibrous cap of atherosclerotic plaques, and high-frequency (40 MHz) ultrasound images were used to identify calcium in the vessel wall. Our preliminary ex vivo investigation of human aortic specimens indicated that PS-OCT might help to identify atherosclerotic lesions.

Assessment of arterial characteristics in human atherosclerosis by extracting optical properties from polarization-sensitive optical coherence tomography.

In this research, we assessed arterial characteristics in human atherosclerosis by determining both scattering and birefringence properties of vessel tissue from polarization-sensitive optical coherence tomography (PS-OCT) images. We demonstrated that optical characteristics including scattering coefficient (mu(s)), effective anisotropy factor (g(eff)), birefringence coefficient (Delta n), and fast-axis angle (beta) of normal and different kinds of atherosclerotic lesions in human vessels can be quantitatively described. Based on our findings, a quantitative PS-OCT image criterion for plaque characterization was constructed.

DIAGNOSIS OF ARTICULAR CARTILAGE DAMAGE BY POLARIZATION SENSITIVE OPTICAL COHERENCE TOMOGRAPHY AND THE EXTRACTED OPTICAL PROPERTIES

This paper presents a diagnosis method for articular cartilage damage using polarization-sensitive optical coherence tomography (PS-OCT). Through signal analysis, the optical characteristics of intact cartilage and different types of mild lesions within cartilages can be quantified from measures such as the scattering coefficient (μs), effective anisotropy factor (geff ), and birefringence coefficient (Δn). Our preliminary investigation using porcine articular cartilage indicated that both subsurface morphological changes and apparent variations in optical properties, which may be the early signs of cartilage degeneration, were found in three types of diseased cartilages.

Ultrastructure of intramural coronary arteries in pigs with hypertrophic cardiomyopathy

Pigs with hypertrophic cardiomyopathy diagnosed by echocardiographic examination were selected for study from a genetic breeding herd. Under dissecting microscopic examination, intramural coronary arteries in the septum and left ventricular free wall of euthanized pigs were collected for ultrastructural study. The major lesions of wall thickening included degeneration or denudation of endothelium, subendothelial edema, proliferation of collagen fiber, and hyperplasia of smooth muscle cells. Smooth muscle cells proliferated and migrated through the internal elastic lamella into the intima, which caused the early lesion of wall thickening of the intramural coronary arteries. The extent of smooth muscle cell proliferation was related to the severity of endothelial damage. The smooth muscle cells in the intima were identified by immunohistochemical staining (i.e., smooth muscle actin [SMA] stain). Three major types of severe wall thickening with narrow lumen were observed in the intramural coronary arteries. Edema in the intima caused the major lesion of Type I wall thickening. The internal elastic lamella was broken into small interrupted fragments, and fine fragments of elastic fibers surrounded by the cellular processes of smooth muscle were observed in Type I lesions. Many smooth muscle cells proliferated in the intima and media, which constituted the major lesion of Type II wall thickening of the intramural coronary arteries. Many vacuolized, degenerated smooth muscle cells with fewer sarcoplasmic myofilaments could be clearly observed in the Type II lesions. In advanced cases, severe vacuolization and degeneration of smooth muscle cells with the presence of many bizarrely shaped smooth muscle cells in the walls of the intramural coronary arteries could be observed, which caused the major lesion of Type III wall thickening. Pigs with hypertrophic cardiomyopathy, characterized by spontaneously occurring lesions in intramural coronary arteries, may prove a valuable animal model for human disease.

Imaging of human aortic atherosclerotic plaques by polarization-sensitive optical coherence tomography

Optical coherence tomography (OCT) is analogous to ultrasound imaging except that it uses infrared light instead of sound. Polarization-sensitive optical coherence tomography (PS-OCT) combines the advantages of OCT and provides additional image contrast of the tested sample. We demonstrate this technique for imaging of back-reflected light, birefringence, and fast-axis orientation simultaneously in different kinds of atherosclerosis plaque. This in vitro study suggests birefringence changes in plaque are due to the prominent deposition of collagen or cholesterol by correlating PS-OCT images with histology. Thus the combination of high resolution structural imaging and birefringence detection make PS-OCT a potentially powerful tool for early assessment of atherosclerosis appearance and prediction of plaque rupture.

Quantitative analysis on optical properties of human atherosclerosis by using polarization-sensitive optical coherence tomography

In this research, we have used an algorithm to extract four different optical parameters, including the scattering coefficient (μs), effective anisotropy factor (goff), birefringence coefficient (Δn), and fast-axis angle (β) from polarization-sensitive optical coherence tomography (PS-OCT) images. The proposed method was evaluated from a set of phantoms and it yielded valid results. We demonstrate that the optical characteristic of normal and different kinds of atherosclerotic lesions in human vessel can be quantitatively described. Whether change in these quantified optical properties could be used to discriminate between different types of human atherosclerotic plaques was examined.

Hemodynamic study of left ventricular assist device during laparoscopy in canine model.

To understand the hemodynamic changes and interaction between the operation of left ventricular assist device (LVAD) and laparoscopy, a small Tai-Ta centrifugal impeller pump was applied in a canine model, in which 6 healthy dogs weighted 14-20kg were used. Blood flows in the aortic (AO) arch, common carotid artery (CCA), coronary artery (CA), femoral artery (FA), and the LVAD outlet were measured simultaneously with the arterial blood pressure (ABP), the pump outflow pressure (POP), and the electrocardiograph (ECG). After the centrifugal impeller pump operated, a fluctuated flow was produced by LVAD according to the cardiac cycles. The waveform of ABP and the flows of CA, CCA, and FA had mild change after systole due to the influence from LVAD flow. After abdominal insufflations the LVAD flow increased in 4 cases and decreased in another 2 cases, the CA flow increased in 3 cases and decreased in 1 case, the CCA flow increased in 2 cases and decreased in 4 cases, the FA flow decreased in all 4 cases. However, by increasing the rotational speed of pump to make LVAD flow more than 50% of total cardiac output, both the pump flow and total cardiac output increased, and the affected CA and CCA flows were also increased. These results indicated that the centrifugal impeller pump could safely operate as a LVAD without significant hemodynamic compromise when intervened with laparoscopy.

The Pathological Study of Calves with the Tai-Ta NO. 1 Centrifugal Pump as Left Ventricular Assist Device（LVAD）

Left ventricular assist device (LVAD) with centrifugal pump was designed and calves were used for in vivo experiments. After thoracotomy, the inflow tube was inserted into the left atrium and the outflow graft was sutured onto the descending thoracic aorta. The bypass flow was adjusted to 2-3 L/min. After surgery, all the physiological data were monitored throughout the experimental period. Following the death of calves, the pathological examinations were performed to analyze the etiology of death. Nineteen calves were used for this study. There was no hemolysis problem observed during the experiment. The calves that died within the first two weeks had bleeding disorders and underwent incomplete post-surgical care. Elevation of blood urea nitrogen and severe anemia were observed at the end stage in calves that survived for longer than 40 days. Infarction of the kidney, spleen and myocardium; bacterial infection, pulmonary congestion, and diffuse hemorrhages were the major lesions found. Thrombi were observed in the aortic branches, mesentery artery, renal artery, splenic artery, femoral artery, coronary artery, and some areas of the LVAD pump. Based on the pathological study, improvements have been introduced to the LVAD experiment and calves could survive for longer. The elimination of thrombosis within the LVAD pump will be the major challenge for future study.