Biomedical subjects

M M Doyley

Publications and source records attributed to M M Doyley.

4 recordsLinked to original sources

PubMed2002

Morphological and mechanical information of coronary arteries obtained with intravascular elastography; feasibility study in vivo.

AIMS: Plaque composition is a major determinant of coronary related clinical syndromes. In vitro experiments on human coronary and femoral arteries have demonstrated that different plaque types were detectable with intravascular ultrasound elastography. The aim of this study was to investigate the feasibility of applying intravascular elastography during interventional catheterization procedures. METHODS AND RESULTS: Data were acquired in patients (n=12) during PTCA procedures with an EndoSonics InVision echoapparatus equipped with radiofrequency output. The systemic pressure was used to strain the tissue, and the strain was determined using cross-correlation analysis of sequential frames. A likelihood function was determined to obtain the frames with minimal motion of the catheter in the lumen, since motion of the catheter prevents reliable strain estimation. Minimal motion was observed near end-diastole. Reproducible strain estimates were obtained within one pressure cycle and over several pressure cycles. Validation of the results was limited to the information provided by the echogram. Strain in calcified material (0.20%+/-0.07) was lower (P<0.001) than in non-calcified tissue (0.51%+/-0.20). CONCLUSION: In vivo intravascular elastography is feasible. Significantly higher strain values were found in non-calcified plaques than in calcified plaques.

Adult↗

PubMed2001

A freehand elastographic imaging approach for clinical breast imaging: system development and performance evaluation.

A prototype freehand elastographic imaging system has been developed for clinical breast imaging. The system consists of a fast data acquisition system, which is able to capture sequences of intermediate frequency echo frames at full frame rate from a commercial ultrasound scanner whilst the breast is deformed using hand-induced transducer motion. Two-dimensional echo tracking was used in combination with global distortion compensation and multi-compression averaging to minimise decorrelation noise incurred when stress is applied using hand-induced transducer motion. Experiments were conducted on gelatine phantoms to evaluate the quality of elastograms produced using the prototype system relative to those produced using mechanically induced transducer motion. The strain sensitivity and contrast-to-noise ratio of freehand elastograms compared favourably with elastograms produced using mechanically induced transducer motion. However, better dynamic range and signal-to-noise ratio was achieved when elastograms were created using mechanically induced transducer motion. Despite the loss in performance incurred when stress is applied using hand-induced transducer motion, it was concluded that the prototype system performed sufficiently well to warrant clinical evaluation.

Elasticity↗

PubMed2001

Advancing intravascular ultrasonic palpation toward clinical applications.

This paper describes the first reported attempt to develop a real-time intravascular ultrasonic palpation system. We also report on our first experience in the catherization laboratory with this new elastographic imaging technique. The prototype system was based on commercially available intravascular ultrasound (US) scanner that was equipped with a 20-MHz array catheter. Digital beam-formed radiofrequency (RF) echo data (i.e., 12 bits, 100 Hz) was captured at full frame rate from the scanner and transferred to personal computer (PC) memory using a fast data-acquisition system. Composite palpograms were created by applying a one-dimensional (1-D) echo tracking technique in combination with global motion compensation and multiframe averaging to several pairs of RF echo frames that were obtained in the diastolic phase of the cardiac cycle. The quality of palpograms was assessed by conducting experiments on vessel phantoms and on patients. The results demonstrated that robust and consistent palpograms could be generated in almost real-time using the proposed system. Good correlation was observed between low strain values and regions of calcification as identified from the intravascular US (IVUS) sonograms. Although the clinical results are clearly preliminary, it was concluded that the prototype system performed sufficiently well to warrant further and more in-depth clinical investigation.

Calcium↗

PubMed2000

Evaluation of an iterative reconstruction method for quantitative elastography.

This paper describes an inverse reconstruction technique based on a modified Newton Raphson iterative scheme and the finite element method, which has been developed for computing the spatial distribution of Young's modulus from within soft tissues. Computer simulations were conducted to determine the relative merits of reconstructing tissue elasticity using knowledge of (a) known displacement boundary conditions (DBC), and (b) known stress boundary conditions (SBC). The results demonstrated that computing Young's modulus using knowledge of SBC allows accurate quantification of Young's modulus. However, the quality of the images produced using this reconstruction approach was dependent on the Young's modulus distribution assumed at the start of the reconstruction procedure. Computing Young's modulus from known DBC provided relative estimates of tissue elasticity which, despite the disadvantage of not being able to accurately quantify Young's modulus, formed images that were generally superior in quality to those produced using the known SBC, and were not affected by the trial solution. The results of preliminary experiments on phantoms demonstrated that this reconstruction technique is capable in practice of improving the fidelity of tissue elasticity images, reducing the artefacts otherwise present in strain images, and recovering Young's modulus images that possess excellent spatial and contrast resolution.

Computer Simulation↗