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Nicolaas Bom

Publications and source records attributed to Nicolaas Bom.

4 recordsLinked to original sources
PubMed2006

Design of a multilayer transducer for acoustic bladder volume assessment.

Catheterization remains the "gold standard" for bladder volume assessment, but it is invasive and introduces the risk of infections and traumas. Therefore, noninvasive bladder volume measurement methods have gained interest. In a preceding study a new technique to measure the bladder volume on the basis of nonlinear ultrasound wave propagation was validated. This paper describes a first prototype of a dedicated multilayer transducer to implement this approach. It is composed of a PZT transducer for transmission and a PVDF layer for reception. Acoustical measurements in a water tank and phantom measurements showed that there is a relation between bladder volume and the harmonic contents of the echo obtained from a region of interest behind the bladder. Simulations with an equivalent transducer model on the basis of KLM-circuit modeling closely matched with the results from the acoustical measurements. The results demonstrated the feasibility of the multilayer transducer design for bladder volume assessment on the basis of nonlinear wave propagation.

Animals↗
PubMed2004

Noninvasive bladder volume measurements based on nonlinear wave distortion.

The purpose of this study is to suggest a new approach to measure noninvasively the fluid content of a human cavity; in particular, the bladder volume. Determination of bladder volume is important clinically for patients suffering from bladder dysfunction. Several ultrasonic methods were proposed in the past for such a purpose. Most of these methods are based on multiple cross-sectional images and detection of echoes from the bladder wall. We propose here, in a first step, a simple approach that is able to provide an indication of whether or not the bladder volume has exceeded a certain threshold volume. Second, the possibility of accurate volume assessment will be discussed. The approach takes advantage of the difference in harmonic generation of liquids (urine) and tissues. We know that nonlinear effects occur most strongly when ultrasound (US) propagates through liquids with relatively low acoustic attenuation, such as water or urine. However, within soft tissues, the tendency for wave distortion to occur is limited as a result of different acoustic characteristics, most notably the attenuation. Our method is based on measuring the presence of harmonics in an echo from a region-of-interest (ROI) at fixed depth beyond the bladder. The harmonic content in the echo will increase with increase of fluid in the echo path. Phantom measurements were carried out with a single-element transducer and a phased-array transducer. Phantoms containing different volumes were used. Furthermore, measurements on volunteers were performed. The results confirmed that the harmonic content of an echo measured at a deep ROI increases for a full bladder and decays strongly after the volunteer has voided. These preliminary results demonstrate the feasibility of the approach.

Biophysical Phenomena↗
PubMed1996

Pediatric Transesophageal Echocardiography by Means of a Miniature 5-MHz Multiplane Transducer.

The development of a miniature multiplane transesophageal echocardiographic (TEE) transducer for pediatric use is the latest development in TEE. Horizontal, longitudinal, and all possible intermediate oblique planes can be obtained with minimal transducer manipulation. We studied 48 patients with an experimental 5-MHz transducer, which contains 48 transmitting elements. The dimensions of the tip are 27 x 10.6 x 7.9 mm. Patients ages ranged from 2 days to 16 years, their weights from 3.6-67 kg. Multiplane TEE proved to be complementary to the single horizontal plane in assessing the right ventricular outflow tract, the left ventricular outflow tract, ascending aorta, the atrial septum, the atrioventricular (AV) valves, especially in AV septal defects, and double inlet left ventricle (DILV). Moreover, multiplane TEE was extremely helpful in judging the outflow tracts and ventricular septal defects in more complex heart defects such as DILV, double outlet right ventricle, and hearts with discordant connections. Multiplane TEE offered superb monitoring of cardiac interventions. We conclude that multiplane TEE provides new imaging planes and enables visualization of every major structure of the heart by unlimited scan planes. Multiplane TEE is indispensable in congenital heart defects. Thus, multiplane TEE adds to diagnostic assurance and enhances decision making for surgery. (ECHOCARDIOGRAPHY, Volume 13, November 1996)

Journal Article↗