E.J.W. Merks

Design of a multi-layer transducer for acoustic bladder volume assessment

Catheterization remains the golden standard for bladder volume assessment, but it is invasive and introduces the risk of infection and trauma. Therefore, noninvasive bladder volume measurement methods are of high interest. In a preceding study, we proposed a new technique to measure bladder volume based on nonlinear ultrasound wave distortion. A dedicated multi-layer transducer, composed of a PZT layer for transmission and a PVDF-layer for reception, has been constructed to verify and implement this approach. Measurements in a water tank and phantom measurements show that there is a correlation between bladder volume and the harmonic contents within a region of interest (ROI) behind the bladder. The results also demonstrate the usability of the multi-layer PZT-PVDF transducer design for bladder volume assessment on the basis of nonlinear wave distortion dependency.

Screening for abdominal aortic aneurysms using a dedicated portable ultrasound system: early results

AIMS Abdominal aortic aneurysms (AAA) are often diagnosed at time of (impending) rupture leading to a dramatic increase of morbidity and mortality. A simple screening device might be the key solution for widespread AAA screening. This study evaluated the diagnostic accuracy of a new portable ultrasound scanner (Aortascan BVI 9600) developed for automatic AAA detection. METHODS AND RESULTS A total of 150 patients with presumed aneurysmatic peripheral atherosclerotic disease were included in the study. Patients were first scanned with conventional ultrasound (US), serving as reference technique. An infra-renal abdominal aorta diameter of > or =30 mm was defined as an AAA. Hereafter, the aorta was scanned using the Aortascan BVI 9600. Statistical analyses were performed using SPSS version 15.0 statistical software. Abdominal aortic aneurysms were detected with conventional US in 78 (52%) patients, compared with 74 (49%) AAAs detected with Aortascan BVI 9600. The Aortascan BVI 9600 demonstrated a sensitivity, specificity, positive and negative predictive value of 90, 94, 95, and 89%, respectively, in the detection of AAAs. CONCLUSION The Aortascan BVI 9600 automatically detects the aortic diameter with a 90% sensitivity without the need for a trained operator. Because of these unique capabilities, it can be used for AAA screening outside the hospital.

Quantitative bladder volume assessment on the basis of nonlinear wave propagation

Catheterization remains the gold standard for bladder volume assessment, but it is invasive, uncomfortable to the patient, and introduces the risk of infections and trauma. To reduce the need for a urinary catheter, a new method has recently been introduced that non-invasively and instantaneously measures the bladder volume on the basis of nonlinear wave propagation and using a single diverging acoustic beam. The performance of the original computational method to quantitatively measure volume was compared with an alternative algorithm using simulations on nonlinear wave propagation and in-vivo measurements. Measurements were performed with an experimental setup including a custom designed multilayer transducer.

Comparison of three different transducer concepts for acoustic bladder volume measurements

In a preceding study the importance of noninvasive bladder volume measurements was addressed, and a new technique to measure the bladder volume on the basis of nonlinear ultrasound wave propagation was validated. It was shown that the harmonic level generated at the posterior bladder wall increases for larger bladder volumes. The objective of this study is to design an optimal transducer to implement this approach. For this purpose, three different transducer concepts, i.e. a multi-layer transducer, a broadband piezo-composite transducer and a multi-element transducer, were mutually compared using calibrated hydrophone measurements in water and pulse-echo measurements on a bladder test phantom. The effects of an additional acoustic lens on the beamwidth and generated peak pressures were also considered.