Wireless Capsule Endoscopy System Research Articles

Specific absorption rate reduction based on outage probability analysis for wireless capsule endoscope with spatial receive diversity

This study investigates the effect of spatial receive diversity on specific absorption rate (SAR) reduction based on outage probability analysis for wireless capsule endoscope (WCE). The communication performance of WCE depends much on the transmit power, which is strictly regulated in order to satisfy a safety guideline in terms of SAR, whereas WCE requires high communication performance due to its real-time data transmission. For the purpose of SAR reduction for a WCE scenario, the authors pay attention to the expectation that applying spatial diversity reception to WCE systems can not only improve the wireless communication performance but also reduce SAR. To begin with, based on finite-difference time-domain simulations with a numerical human body model, the outage probability is calculated under this implant propagation channel and the required transmit power is derived to secure a permissible outage probability. Then, the local peak SAR is calculated under the required transmit power when the WCE moves through the digestive organs. Finally, the simulation results demonstrate that applying spatial diversity reception can significantly reduce SAR for WCE.

Blind Signal Processing for Medical Sensing Systems with Optical-Fiber Signal Transmission

Abstract In many medical image devices, dc noise often prevents normal diagnosis. In wireless capsule endoscopy systems, multipath fadingthrough indoor wireless links induces inter-symbol interference (ISI) and indoor electric devices generate impulsive noise in the receivedsignal. Moreover, dc noise, ISI, and impulsive noise are also found in optical fiber communication that can be used in remote medicaldiagnosis. In this paper, a blind signal processing method based on the biased probability density functions of constant modulus errorthat is robust to those problems that can cause error propagation in decision feedback (DF) methods is presented. Based on this propertyof robustness to error propagation, a DF version of the method is proposed. In the simulation for the impulse response of optical fiberchannels having slowly varying dc noise and impulsive noise, the proposed DF method yields a performance enhancement of approx-imately 10 dB in mean squared error over its linear counterpart.

Low power FPGA-based image processing core for wireless capsule endoscopy

The paper presents an FPGA-based image and data processing core for future generation wireless capsule endoscopy (WCE). The main part of the presented core is an image compressor, for which a hardware implementation architecture requiring only two clock cycles for processing a single image pixel is proposed. Apart from the image compressor, the presented core includes a camera interface, a FIFO queue storing the compressed image bitstream, a forward error correction encoder protecting transmitted data against random and burst transmission errors, and a system controller supervising internal WCE operations. The presented core has been implemented in a single ultra low power, 65 nm FPGA chip. Power consumption of the designed FPGA core was determined to be comparable to other ASIC-based WCE systems.

A video wireless capsule endoscopy system powered wirelessly: design, analysis and experiment

Wireless capsule endoscopy (WCE), as a relatively new technology, has brought about a revolution in the diagnosis of gastrointestinal (GI) tract diseases. However, the existing WCE systems are not widely applied in clinic because of the low frame rate and low image resolution. A video WCE system based on a wireless power supply is developed in this paper. This WCE system consists of a video capsule endoscope (CE), a wireless power transmission device, a receiving box and an image processing station. Powered wirelessly, the video CE has the abilities of imaging the GI tract and transmitting the images wirelessly at a frame rate of 30 frames per second (f/s). A mathematical prototype was built to analyze the power transmission system, and some experiments were performed to test the capability of energy transferring. The results showed that the wireless electric power supply system had the ability to transfer more than 136 mW power, which was enough for the working of a video CE. In in vitro experiments, the video CE produced clear images of the small intestine of a pig with the resolution of 320 × 240, and transmitted NTSC format video outside the body. Because of the wireless power supply, the video WCE system with high frame rate and high resolution becomes feasible, and provides a novel solution for the diagnosis of the GI tract in clinic.

A Wideband Spiral Antenna for Ingestible Capsule Endoscope Systems: Experimental Results in a Human Phantom and a Pig

This paper presents the design of a wideband spiral antenna for ingestible capsule endoscope systems and a comparison between the experimental results in a human phantom and a pig under general anesthesia. As wireless capsule endoscope systems transmit real-time internal biological image data at a high resolution to external receivers and because they operate in the human body, a small wideband antenna is required. To incorporate these properties, a thick-arm spiral structure is applied to the designed antenna. To make practical and efficient use of antennas inside the human body, which is composed of a high dielectric and lossy material, the resonance characteristics and radiation patterns were evaluated through a measurement setup using a liquid human phantom. The total height of the designed antenna is 5 mm and the diameter is 10 mm. The fractional bandwidth of the fabricated antenna is about 21% with a voltage standing-wave ratio of less than 2, and it has an isotropic radiation pattern. These characteristics are suitable for wideband capsule endoscope systems. Moreover, the received power level was measured using the proposed antenna, a circular polarized receiver antenna, and a pig under general anesthesia. Finally, endoscopic capsule images in the stomach and large intestine were captured using an on-off keying transceiver system.

An efficient hardware-optimized compression algorithm for wireless capsule endoscopy image transmission

A dedicated image compression algorithm was developed for wireless capsule endoscopy (WCE). The proposed approach reduces the amount image data without compromising the image quality. This allows an increase in image throughput to improve the real-time vision capabilities of a WCE system. The algorithm is based on a normalized Haar-wavelet transformation, aiming at a hardware-optimized implementation in a low-power FPGA or telemetry ASIC for wireless capsule endoscopes. Taking advantage of the limited color content of endoscopic images, this solution uses the YCbCr color space combined with efficient recoding of the wavelet transformation data. In this way adequate compression ratios at decent image qualities can be achieved in a hardware efficient thus low power implementation, outperforming existing hardware implemented algorithms.

A Wireless Capsule Endoscope System With Low-Power Controlling and Processing ASIC

This paper presents the design of a wireless capsule endoscope system. The proposed system is mainly composed of a CMOS image sensor, a RF transceiver and a low-power controlling and processing application specific integrated circuit (ASIC). Several design challenges involving system power reduction, system miniaturization and wireless wake-up method are resolved by employing optimized system architecture, integration of an area and power efficient image compression module, a power management unit (PMU) and a novel wireless wake-up subsystem with zero standby current in the ASIC design. The ASIC has been fabricated in 0.18-mum CMOS technology with a die area of 3.4 mm * 3.3 mm. The digital baseband can work under a power supply down to 0.95 V with a power dissipation of 1.3 mW. The prototype capsule based on the ASIC and a data recorder has been developed. Test result shows that proposed system architecture with local image compression lead to an average of 45% energy reduction for transmitting an image frame.

Performance Characteristics of the Suspected Blood Indicator Feature in Capsule Endoscopy According to Indication for Study

The suspected blood indicator (SBI) feature of wireless capsule endoscopy (WCE) was developed for rapid screening of intestinal lesions with bleeding potential. Our aim was to assess the accuracy and performance characteristics of the SBI according to the indications for study in a large cohort of patients. We reviewed collected data on all WCE studies performed at Johns Hopkins Hospital from January 2006 to June 2007. Study indications were as follows: anemia of unknown origin (n = 53), obscure gastrointestinal bleeding (n = 112), suspected Crohn's disease (n = 122), and other (n = 4). Concordant and discordant findings between gastroenterologists' readings and SBI were recorded for each patient. A total of 221 lesions with bleeding potential was detected. The overall sensitivity, specificity, positive predictive value, and negative predictive value for the SBI were 56.4%, 33.5%, 24.0%, and 67.3%, respectively. For actively bleeding lesions, the SBI sensitivity and positive predictive value were only 58.3% and 70%, respectively. The sensitivity was highest (64%) in patients undergoing WCE for suspected Crohn's disease, with a negative predictive value of 80.4%. The sensitivity was only 58.3% and 41.3%, respectively, in studies performed for obscure gastrointestinal bleeding and anemia. Performance characteristics of the currently available SBI feature in WCE are suboptimal and insufficient to screen for lesions with bleeding potential. Even in patients with active intestinal bleeding, the sensitivity of SBI was less than 60%, which is lower than previously reported. However, in patients with suspected Crohn's disease, the high sensitivity and negative predictive value of SBI may make it a useful tool for the detection of large areas of abnormal mucosa.

Wireless capsule endoscopy for obscure small-bowel disorders: Final results of the first pediatric controlled trial

Obscure small-bowel disorders are jejunal and ileal lesions undiagnosed by traditional imaging techniques (endoscopic, radiologic). We evaluated the diagnostic usefulness and safety of capsule endoscopy for obscure small-bowel disorders in children and adolescents. Comparative, prospective, self-controlled trials in patients (age, 10-18 y) suspected to have either small-bowel Crohn's disease, polyps, or obscure gastrointestinal (GI) bleeding. Capsule results were compared with the diagnostic imaging studies normally used in this age group. Among 20 patients suspected of Crohn's disease, multiple lesions consistent with this diagnosis were observed by capsule endoscopy in 50%. Small-bowel Crohn's disease was ruled out in 8 patients. Eosinophilic enteropathy was found in 2 others. For polyp detection (n = 6), capsule endoscopy yielded 100% concordance with the control studies when analyzed per patient. However, capsule endoscopy revealed a greater number (50%) of polyps. Among patients with obscure bleeding (n = 4), the capsule examination confirmed a diagnosis of vascular malformations in 3. Capsule endoscopy more accurately identified the precise source of bleeding compared with angiography. All 30 capsule studies were well tolerated, although 1 capsule was retained owing to an inflammatory stenosis. The capsule eventually was expelled after corticosteroid therapy. Capsule endoscopy correctly diagnosed or excluded a bleeding source, small-bowel polyps, or Crohn's disease of the small bowel in 29 of 30 patients. Capsule endoscopy permits an accurate, noninvasive approach for diagnosing obscure small bowel lesions in children over the age of 10.