Power Consumption Considerations for Ultrasound Capsule Endoscopy

Ultrasound capsule endoscopy (USCE) promises to combine the usefulness of the traditional endoscope with the increased comfort, reduced risks, and wider reach of a capsule for diagnosis of gastrointestinal tract (GIT) diseases. Equipped with a microultrasound (µUS) array operating at frequencies higher than 20 MHz, the USCE device can benefit from increased axial resolution, while the use of an array can provide a wider field of view via electronic beam-steering. However, reduced available power and limited physical dimensions are obstacles presently hindering the development of such medical devices. This paper proposes and evaluates US array driving techniques to reduce power consumption, discusses the limitations of receiving electronics and considers achievable B-mode imaging frame rates. Two array drivers were used in this study: a custom-made CMOS pulser, with details published previously, and a commercial research array controller (Vantage HF 128, Verasonics, WA, USA). Peak (ipeak) and average (iavg) supply current measurements performed for a variable number of elements transmitting (Tx) simultaneously in a 28 MHz µUS array (Vermon, France) show that Tx apertures comprising <7 active elements are most suitable. Furthermore, because of the high ipeak supplied to the array, charge storage on board the USCE device is required for any Tx configuration.