Tareq Hasan Khan

Low Power and Low Complexity Compressor for Video Capsule Endoscopy

The main challenge in video capsule endoscopic system is to reduce the area and power consumption while maintaining acceptable video reconstruction. In this paper, a subsample-based data compressor for video endoscopy application is presented. The algorithm is developed around the special features of endoscopic images that consists of a differential pulse-coded modulation (DPCM) followed by Golomb-Rice coding. Based on the nature of endoscopic images, several subsampling schemes on the chrominance components are applied. This video compressor is designed in a way to work with any commercial low-power image sensors that outputs image pixels in a raster scan fashion, eliminating the need of memory buffer and temporary storage (as needed in transform coding schemes). An image corner clipping algorithm is also introduced. The reconstructed images have been verified by five medical doctors for acceptability. The proposed low-complexity design is implemented in a 0.18 μm CMOS technology and consumes 592 standard cells, 0.16 × 0.16 mm silicon area, and 42 μW of power. Compared to other algorithms targeted to video capsule endoscopy, the proposed raster-scan-based scheme performs strongly with a compression ratio of 80% and a very high reconstruction peak signal-to-noise ratio (over 48 dB).

Lossless and low-power image compressor for wireless capsule endoscopy

We present a lossless and low-complexity image compression algorithm for endoscopic images. The algorithm consists of a static prediction scheme and a combination of golomb-rice and unary encoding. It does not require any buffer memory and is suitable to work with any commercial low-power image sensors that output image pixels in raster-scan fashion. The proposed lossless algorithm has compression ratio of approximately 73% for endoscopic images. Compared to the existing lossless compression standard such as JPEG-LS, the proposed scheme has better compression ratio, lower computational complexity, and lesser memory requirement. The algorithm is implemented in a 0.18 µm CMOS technology and consumes 0.16mm × 0.16mm silicon area and 18 µW of power when working at 2 frames per second.

New color image enhancement method for endoscopic images

This paper presents a simple and efficient color image enhancement method for endoscopic images. The proposed image enhancement method works by two interrelated steps: image enhancement at gray level and color reproduction. At, first, the captured RGB endoscopic image is converted into 2 dimensional gray level spectral images using a well-known method called FICE (Fuji Intelligent Color Enhancement). In the next stage the image with maximum entropy is selected as the base image to be used for color reproduction. Maximum entropy value indicates the maximum enhanced image. In color reproduction, the entire chrominance map of a source image is transferred into the base image by matching luminance and texture information between two images. The distance between luminance components of target (base image) and source images are calculated using 2-norm Euclidean distance. The proposed color image enhancement method is compared with popular narrow-band imaging on the scale of image quality, image enhancement, simulation speed and efficiency of color reproduction and distortion. The proposed method can be applied on any RGB images collected from any white light endoscopic devices. Is highlights the tissue characterization on the surface part of base endoscopic image that enables better diagnosis.

An advanced physiological data logger for medical imaging applications

The interest of physiological data sensing and recording using wireless body sensor network has increased in recent years due to the advancement of miniature and portable electronic devices. In this study, the design of a portable and rechargeable data logger with high data rate multiple wireless connectivity (Bluetooth and 2.4-GHz radio frequency) is discussed. The data are logged in micro secure digital (SD) cards and can be transferred to PC or Smartphone using SD card reader, USB interface, or Bluetooth wireless link. Analog signals can also be logged through an 8-channel analog-to-digital interface. A graphical LCD with touch screen is added for control and diagnosis. The hardware is generic and targeted for various medical imaging and data collection applications. The functionality of the prototype is later tested for wireless capsule endoscopy and skin temperature logging application.

White and narrow band image compressor based on a new color space for capsule endoscopy

In this paper, we present the design of a low power and hardware efficient image compressor integrated circuit for wireless capsule endoscopy application. The proposed compression algorithm supports dual-band imaging, that is, works on both white-band imaging (WBI) and narrow-band imaging (NBI). The scheme uses a novel color-space and simple predictive coding for optimized performance. Based on the nature of the narrow- and white-band endoscopic images and video sequences, several sub-sampling schemes are introduced. The proposed dual-band compressor is designed in such as way that it can easily be interfaced with any commercial low power image sensor that outputs RGB image pixels in a raster scan fashion, eliminating the need of large buffer memory and temporary storage. Both NBI and WBI reconstructed images have been verified by medical doctors for acceptability. Compared to other designs targeted to video capsule endoscopy, the proposed algorithm performs strongly with a compression ratio of 80.4% (for WBI) and 79.2% (for NBI), and a high reconstruction peak-signal-to-noise-ratio (over 43.7dB for both bands). The results of the fabricated chip are also presented.

Design of a lossless image compression system for video capsule endoscopy and its performance in in-vivo trials.

In this paper, a new low complexity and lossless image compression system for capsule endoscopy (CE) is presented. The compressor consists of a low-cost YEF color space converter and variable-length predictive with a combination of Golomb-Rice and unary encoding. All these components have been heavily optimized for low-power and low-cost and lossless in nature. As a result, the entire compression system does not incur any loss of image information. Unlike transform based algorithms, the compressor can be interfaced with commercial image sensors which send pixel data in raster-scan fashion that eliminates the need of having large buffer memory. The compression algorithm is capable to work with white light imaging (WLI) and narrow band imaging (NBI) with average compression ratio of 78% and 84% respectively. Finally, a complete capsule endoscopy system is developed on a single, low-power, 65-nm field programmable gate arrays (FPGA) chip. The prototype is developed using circular PCBs having a diameter of 16 mm. Several in-vivo and ex-vivo trials using pigs intestine have been conducted using the prototype to validate the performance of the proposed lossless compression algorithm. The results show that, compared with all other existing works, the proposed algorithm offers a solution to wireless capsule endoscopy with lossless and yet acceptable level of compression.

A DVP-Based Bridge Architecture to Randomly Access Pixels of High-Speed Image Sensors

A design of a novel bridge is proposed to interface digital-video-port (DVP) compatible image sensors with popular microcontrollers. Most commercially available CMOS image sensors send image data at high speed and in a row-by-row fashion. On the other hand, commercial microcontrollers run at relatively slower speed, and many embedded system applications need random access of pixel values. Moreover, commercial microcontrollers may not have sufficient internal memory to store a complete image of high resolution. The proposed bridge addresses these problems and provides an easy-to-use and compact way to interface image sensors with microcontrollers. The proposed design is verified in FPGA and later implemented using CMOS 0.18 um Artisan library cells. The design costs 4,735 gates and 0.12 mm2 silicon area. The synthesis results show that the bridge can support a data rate up to 254 megasamples/sec. Its applications may include pattern recognition, robotic vision, tracking system, and medical imaging.

Colour-reproduction algorithm for transmitting variable video frames and its application to capsule endoscopy

Presented is a new power-efficient colour generation algorithm for wireless capsule endoscopy (WCE) application. In WCE, transmitting colour image data from the human intestine through radio frequency (RF) consumes a huge amount of power. The conventional way is to transmit all R, G and B components of all frames. Using the proposed dictionary-based colour generation scheme, instead of sending all R, G and B frames, first one colour frame is sent followed by a series of grey-scale frames. At the receiver end, the colour information is extracted from the colour frame and then added to colourise the grey-scale frames. After a certain number of grey-scale frames, another colour frame is sent followed by the same number of grey-scale frames. This process is repeated until the end of the video sequence to maintain the colour similarity. As a result, over 50% of RF transmission power can be saved using the proposed scheme, which will eventually lead to a battery life extension of the capsule by 4-7 h. The reproduced colour images have been evaluated both statistically and subjectively by professional gastroenterologists. The algorithm is finally implemented using a WCE prototype and the performance is validated using an ex-vivo trial.

A portable wireless body sensor data logger and its application in video capsule endoscopy

Due to the advancement of low power miniature electronic devices, there is growing interest of physiological data sensing and recording using wireless body sensor networks. The paper presents the design of a portable physiological data logger that includes rechargeable battery, wireless radio frequency and Bluetooth connectivity, and graphical display with touch screen capability. The target application is video capsule endoscopy. Image data are logged in micro SD cards which can be easily transferred to PC or Smartphone using SD card reader, USB interface or Bluetooth wireless link. The hardware design is general and can be used in various medical or industrial applications by changing only the firmware of the microcontroller. The design is prototyped in 109x107x20mm printed circuit board (PCB). Tests with animal tissues have been conducted to demonstrate the performance advantages of the data logger. A demonstration of wireless heart pulse monitoring and data logging is also presented.

Design of a DVP compatible bridge to randomly access pixels of high speed image sensors

An efficient design of a digital-video-port (DVP) compatible bridge architecture to randomly access image pixels of a high speed image sensor is presented. FPGA synthesis results show that the bridge can support a data rate up to 215 MHz. The design is also synthesized using CMOS 0.18um technology.