Biomedical subjects

P J Benkeser

Publications and source records attributed to P J Benkeser.

5 recordsLinked to original sources

PubMed1996

A computer-based statistical pattern recognition for Doppler spectral waveforms of intracranial blood flow.

A computer-based statistical pattern recognition system has been developed for the analysis of transcranial Doppler (TCD) spectral waveforms of the intracranial middle cerebral artery with varying degrees of increased intracranial pressure. This system extracts multidimensional features from TCD waveforms and performs a cluster analysis of those features. The system can automatically recognize the pattern of spectral waveform and classify it as a normal, abnormal, or borderline subclass of TCD spectral waveform. An optimum decision function was generated based on the Bayes Gaussian classifier. The accuracy of the Bayes Gaussian model the spectral waveforms reaches 100% by estimating posterior probability and using the resubstituting method of estimating misclassification in the training TCD data.

Artificial Intelligence↗

PubMed1991

Ultrasonic phased array controller for hyperthermia applications.

Multiple and mechanically scanned ultrasound transducer systems have demonstrated the efficacy of using ultrasound to produce deep localized hyperthermia. The use of ultrasonic phased arrays has been proposed as an alternative to these systems. A phased array offers a more flexible approach to heating tumours in that the size, shape, and position of its focal region can be altered during the course of treatment in order to achieve the desired temperature distribution. This added flexibility comes at the cost of increased complexity of the hardware necessary to drive the transducer because each element requires its own amplifer with both phase and amplitude control. In order for phased arrays with large numbers of elements to be feasible for hyperthermia applications, the complexity of this circuitry must be minimized. This paper describes a circuit design which simplifies the electronics required to control a phased array transducer system for hyperthermia applications. The design is capable of controlling virtually any type of phased array transducer operating at frequencies less than 2 MHz. The system performance was verified through beam profile measurements using a 48-element tapered phased array transducer.

Hyperthermia, Induced↗

PubMed1990

A perfused tissue phantom, for ultrasound hyperthermia.

A perfused tissue phantom, developed as a tool for analyzing the performance of ultrasound hyperthermia applicators, was investigated. The phantom, consisting of a fixed porcine kidney with thermocouples placed throughout the tissue, was perfused with degassed water by a variable flow rate pump. The phantom was insonated by an unfocused multielement ultrasound applicator and the temperatures in the phantom were recorded. The results indicate that for testing protocols where tissue phantoms are needed, the fixed kidney preparation offers an opportunity to use a more realistic phantom than has previously been available to assess the heating performance of ultrasound hyperthermia applicators.

Animals↗

PubMedDate not supplied

Resolution limitations in intravascular ultrasound imaging.

Interest in the use of ultrasound to characterize the structure and composition of blood vessel walls has risen dramatically as a result of the development of intravascular ultrasonic imaging transducers mounted on the tips of small-diameter catheters. A study of the resolution of these transducers is needed to understand the limitations in the visualization of these structures. Theoretic and experimental studies of the resolution of the two principal designs of intravascular ultrasonic transducers, the mechanically scanned single element and the multielement circular array, were carried out. Comparisons of the two designs reveal that they have similar resolutions. However, the resolutions in two of the three dimensions are shown to decrease linearly with increasing radial distance. Significant errors in image interpretation, particularly in larger diameter vessels, will result if this variation in resolution is not accounted for.

Blood Vessels↗

PubMedDate not supplied

Comparison of septal defects in 2D and 3D echocardiography using active contour models.

Three-dimensional ultrasound is emerging as a viable resource for the imaging of internal organs. Quantitative studies correlating ultrasonic volume measurements with MRI data continue to validate this modality as a more efficient alternative for 3D imaging studies. However, the processing required to form 3D images from a set of 2D images may result in a loss of spatial resolution and may give rise to artifacts. This paper examines a method of automatic feature extraction and data quantification in 3D data sets as compared with original 2D data. This work will implement an active contour algorithm to automatically extract the endocardial borders of septal defects in echocardiographic images, and compare the size of the defects in the original 2D images and the 3D data sets.

Echocardiography↗