Progress towards a multi-modal capsule endoscopy device featuring microultrasound imaging

et al. 2017

Sensors

Video capsule endoscopy (VCE) is now a clinically accepted diagnostic modality in which miniaturized technology, an on-board power supply and wireless telemetry stand as technological foundations for other capsule endoscopy (CE) devices. However, VCE does not provide therapeutic functionality, and research towards therapeutic CE (TCE) has been limited. In this paper, a route towards viable TCE is proposed, based on multiple CE devices including important acoustic sensing and drug delivery components. In this approach, an initial multimodal diagnostic device with high-frequency quantitative microultrasound that complements video imaging allows surface and subsurface visualization and computer-assisted diagnosis. Using focused ultrasound (US) to mark sites of pathology with exogenous fluorescent agents permits follow-up with another device to provide therapy. This is based on an US-mediated targeted drug delivery system with fluorescence imaging guidance. An additional device may then be utilized for treatment verification and monitoring, exploiting the minimally invasive nature of CE. While such a theranostic patient pathway for gastrointestinal treatment is presently incomplete, the description in this paper of previous research and work under way to realize further components for the proposed pathway suggests it is feasible and provides a framework around which to structure further work.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Acoustic Sensing and Ultrasonic Drug Delivery in Multimodal Theranostic Capsule Endoscopy

Stewart

Qiu

et al. 2017

Sensors

“…However, this leads to concerns about thermal behavior. To address these, trial capsules were designed and manufactured to determine a viable power budget [22]. These capsules used a set of external thermistors and internal temperature sensors to determine the heating caused by various currents flowing through a power resistor.…”

Section: Usce Imaging System Contextmentioning

confidence: 99%

Design and Simulation of a Ring-Shaped Linear Array for Microultrasound Capsule Endoscopy

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

Cox

Seetohul

et al. 2018

Video capsule endoscopy (VCE) has significantly advanced visualization of the gastrointestinal tract since its introduction in the last 20 years. Work is now under way to combine VCE with microultrasound imaging. However, small maximum capsule dimensions, coupled with the electronics required to integrate ultrasound imaging capabilities, pose significant design challenges. This paper describes a simulation process for testing transducer geometries and imaging methodologies to achieve satisfactory imaging performance within the physical limitations of the capsule size and outlines many of the tradeoffs needed in the design of this new class of ultrasound capsule endoscopy (USCE) device. A hybrid MATLAB model is described, incorporating Krimholtz-Leedom-Matthaei circuit elements and digitizing and beamforming elements to render a gray-scale B-mode. This model is combined with a model of acoustic propagation to generate images of point scatterers. The models are used to demonstrate the performance of a USCE transducer configuration comprising a single, unfocused transmit ring of radius 5 mm separated into eight segments for electrical impedance control and a 512-element receive linear array, also formed into a ring. The MATLAB model includes an ultrasonic pulser circuit connected to a piezocrystal composite transmit transducer with a center frequency of 25 MHz. B-scan images are simulated for wire target phantoms, multilayered phantoms, and a gut wall model. To demonstrate the USCE system's ability to image tissue, a digital phantom was created from single-element ultrasonic transducer scans of porcine small bowel ex vivo obtained at a frequency of 45 MHz.

“…Once the porcine model had been established, preliminary translational trials were undertaken with a set of tethered ultrasound capsules which were previously developed [10], featuring four 30 MHz PVDF single element transducers and an internal receive amplification circuit comprising 4 channel transmit/receive protection (MD0101, Microchip Technology, Chandler, USA) and operation amplifiers (ADA4807, Analog Devices, Norwood, USA) set for 12 dB of gain. Multiple identical capsules were prepared prior to the trials, with 2 capsules being used in the final experiment.…”

Section: Translational Trialsmentioning

confidence: 99%

Translational trial outcomes for capsule endoscopy test devices

2017 IEEE International Ultrasonics Symposium (IUS)

Cummins

Cox

et al. 2017

Current clinical standards in the endoscopic diagnosis of gastrointestinal diseases are primarily based on the use of optical systems. Ultrasound has established diagnostic credibility in the form of endoscopic ultrasound (EUS), however it is limited to examination of the upper gastrointestinal tract (oesophagus, stomach and upper (proximal) small bowel). Access to the remainder of the small bowel is currently limited to optical capsule endoscopes and a limited number of other modalities as these capsules are restricted to visual examination of the surface or mucosa of the gut wall. Ultrasound capsule endoscopy has been proposed to integrate microultrasound imaging capabilities into the existing capsule format and extend examination capabilities beyond the mucosa. To establish the ability of high frequency ultrasound to resolve the histological structure of the gastrointestinal tract, ex vivo scans of pig and human tissue were performed. This was done using 25 and 34 MHz single element, physically focused composite transducers mechanically scanned along the tissue. Tethered prototype devices were then developed with 30 MHz physically focused polyvinylidene fluoride (PVDF) single element transducers embedded for use in initial translational trials in the small bowel of porcine subjects. B-scan images from the ex vivo model validation and the in vivo trials are presented.