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Biomedical subjects

M Y Shao

Publications and source records attributed to M Y Shao.

6 recordsLinked to original sources

Oxidative dehydrogenation on the alpha-carbon of 4-pyridylacetonitrile complexes of pentaammineruthenium(II).

The oxidation of Ru(NH(3))(5)NCCH(2)py(2+) in 0.10 M HCl turns the solution from yellow to greenish blue with an absorption at lambda = 791 nm. The absorbance reaches its maximum value when the complex undergoes a two-electron oxidation. The IR and (1)H NMR spectra of the product indicate that the metal center remains as Ru(II) and that the ligand is oxidized. The (13)C NMR spectral results suggest that the oxidation product is [(NH(3))(5)RuNCC(pyH)C(pyH)CNRu(NH(3))(5)](ClO(4))(6). Cyclic voltammetry of the product solution also indicates that the oxidation proceeds in two one-electron steps corresponding to [Ru(III),Ru(II)] + e(-) <= => [Ru(II),Ru(II)] and [Ru(III),Ru(III)] + e(-) <= => [Ru(III),Ru(II)]. The structure of the product in deprotonated form [(NH(3))(5)RuNCC(py)C(py)CNRu(NH(3))(5)](ClO(4))(4)(H(2)O)(2) was determined crystallographically. [(NH(3))(5)RuNCC(py)C(py)CNRu(NH(3))(5)](ClO(4))(4)(H(2)O)(2) crystallizes in the orthorhombic Pbca space group with cell constants a = 13.7138 (16) A, b = 15.7553 (18) A, c = 17.831(2) A, and Z = 4. A mechanism for the oxidation has been proposed on the basis of the kinetic studies in the region of 0.01-0.20 M acid concentrations.

Journal Article↗

Evaluation of in vitro measurement accuracy of a three-dimensional ultrasound scanner.

We have constructed a three-dimensional (3-D) ultrasound scanner to make examinations easier and more accurate. The accuracy of the 3-D scanner has been determined by scanning a three-dimensional model. Lengths, angles, and volume of the model were computed and compared to values determined from physical measurement. Distances between image planes were computed with a mean error of 0.4% of true value. Volume was computed with a mean error of 1.6%, or 0.64 mL +/- 0.72 mL (1 SD). We conclude that the 3-D scanner has a system error of less than 0.4%, that it does not introduce significant new errors, and that the principal source of measurement error is poor lateral resolution due to ultrasound beam width. We believe that the 3-D scanner may be a clinically useful instrument for quantitative echographic measurements.

Algorithms↗

Three-dimensional spatial registration and interactive display of position and orientation of real-time ultrasound images.

Ultrasound images may be difficult to interpret because of the lack of an image orientation display. To resolve this problem, a three-dimensional (3-D) ultrasound scanner has been constructed that provides spatial registration and display of position and orientation of real-time images while allowing unconstrained movement of the scanning transducer. It consists of a conventional sector scanner, a 3-D acoustical spatial locater, and a personal computer. It displays within each image the line of intersection of two image planes, a reference image, and a live image. This display guides and documents image positioning. The scanner's 3-D data also provide the potential for computergraphic modeling of organs, the ability to calculate volumes using nonparallel, nonintersecting image planes, and the capability for 3-D color flow mapping and measurement of Doppler angle.

Humans↗

Three-dimensional echocardiography: in vitro validation for quantitative measurement of total and "infarct" surface area.

The rapid development of numerous therapeutic options for myocardial revascularization requires more advanced, quantitative echocardiographic methods such as measurement of total endocardial and infarct surface area to evaluate myocardial infarction and assess the effects of therapy. Two-dimensional echocardiography is insufficiently quantitative for this purpose because it cannot directly measure three-dimensional relationships with such as volume and surface area. To limitation this limitation we have developed a three-dimensional echocardiograph capable of measuring total and regional or "infarct" surface area. In vitro validation of this method has been carried out comparing computed areas with true areas of a pin model and fixed hearts. Infarcts were demarcated on the fixed hearts by placing pins in the myocardium. The pin heads on the epicardial surface defined infarct regions that could be imaged. True surface areas of the pin model were determined by physical measurement and calculation. True areas of the fixed hearts were determined by planimetry of surface casts made with plastic tape. Accuracies for total and infarct areas were 1.36% and 2.13% for the pin model and 1.61% and 3.48% for the fixed hearts. Interobserver variability for both phantoms was less than 2.5%. The standard error of the estimate predicting total and infarct surface area for the fixed hearts was 1.53 cm2 and 0.71 cm2, respectively (p < 0.001). Three-dimensional echocardiography provides a new, accurate method for directly measuring global and regional surface areas and holds promise for improved evaluation of myocardial infarction and assessment of its treatment.

Animals↗

Three-dimensional echocardiographic volume computation by polyhedral surface reconstruction: in vitro validation and comparison to magnetic resonance imaging.

Two-dimensional echocardiographic methods of left ventricular volume computation are limited by geometric assumptions and image plane positioning error in the nonvisualized dimension. We evaluated a three-dimensional (3D echocardiographic method that addresses these limitations. Our method uses a volume computation algorithm based on polyhedral surface reconstruction (PSR) and nonparallel, unequally spaced, nonintersecting short-axis planes. Seventeen balloon phantoms were subjected to volume computation by the 3D echocardiography-PSR method and by magnetic resonance imaging (MRI) and compared to true volumes determined by water displacement. The results for 3D echocardiography-PSR were: accuracy = 2.27%, interobserver variability = 4.33%, r = 0.999, SEE = 2.45 ml, and p less than 0.001. Results for MRI were 8.01%, 13.78%, r = 0.995, SEE = 7.01 ml, and p less than 0.001. There was no statistically significant difference between the methods. We conclude that precise image plane positioning and use of the 3D echocardiographic-PSR volume computation method achieves high accuracy and reproducibility in vitro. The excellent in vitro correlation between 3D echocardiography-PSR and MRI indicates that MRI may also serve as an in vivo standard of comparison.

Cardiac Volume↗