Biomedical subjects

K G Chua

Publications and source records attributed to K G Chua.

20 records · Page 2Linked to original sources

PubMedDate not supplied

Optimal ECG monitoring during percutaneous transluminal coronary angioplasty of the left anterior descending artery.

During percutaneous transluminal coronary angioplasty (PTCA) frontal ECG leads are routinely monitored. The detection of ST segment deviation during the procedure is important for decisions regarding guiding catheter seating and the timing of balloon inflation and deflation. ST segment deviation appears on intracoronary electrograms in the absence of changes on the surface ECG in many patients, while the reverse is true in some individuals. When a precordial lead is employed, V5 or V6 is most commonly selected. The surface ECG leads most sensitive for monitoring ischemia during left anterior descending angioplasty are not known. In nine lead surface ECGs recorded during balloon inflation, a small degree of ST segment elevation occurred in leads I, aVL, and V5. Lead V2 demonstrated an increase in ST displacement from 0.0 +/- 0.03 mV to 0.29 +/- 0.25 mV during coronary occlusion (p less than 0.01). We conclude that if V5 or V6 is used as a single precordial lead, surface ECG alterations are easily overlooked. During left anterior descending occlusion the most sensitive surface lead is V2. Optimal ECG monitoring during PTCA in some cases should involve surface lead V2 or the intracoronary lead.

Adult↗

PubMedDate not supplied

Image feature analysis and computer-aided diagnosis in digital radiography. 2. Computerized determination of vessel sizes in digital subtraction angiography.

We developed an iterative deconvolution technique to determine the size of a "blurred" vessel in a digital subtraction angiographic (DSA) image by taking into account the unsharpness of the DSA system. Initially, a region of interest over a small segment of the contrast-filled vessel was selected in a DSA image, and the center line of the opacified vessel was determined by polynomial curve fitting of the locations of the peak pixel values along the vessel image. The blurred image profile was then obtained from pixel values across the vessel in a direction perpendicular to the center line. This measured profile was compared iteratively with a calculated profile for various size vessels, which was obtained from a cylindrical vessel model and from the line spread function, until the root-mean-square difference between the two profiles was minimized. The size of a cylindrical vessel yielding the matched profile was considered the best estimate of the unknown vessel size. Studies with a blood vessel phantom indicated that vessels larger than 0.5 mm could be measured with an accuracy and precision of approximately 0.1 mm, which is about 1/3 of the pixel size used in our DSA system. Details of our approach and some clinical vessel images with and without simulated stenotic lesions are presented.

Angiography↗