20-08-2013, 04:26 PM
Low Cost Subcutaneous Vein Detection System Using ARM9 Single Board Computer
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Abstract
Vein detection is one of the latest biomedical techniques researched today.
While the concept behind the method is simple, there are various challenges to be
found throughout the design and implementation of a device concerning the light-
ing system and the image processing algorithms. While a very few devices based
on the infrared technique have been implemented, there still exists a strong need
to develop such medical devices. The major problem faced by the doctors today is
difficulty in accessing veins for intra-venous drug delivery. With improper detec-
tion of veins, severe problems like bruises,rashes, blood clot etc. occur. Therefore
a non-invasive subcutaneous vein detection system has been developed success-
fully based on near infrared imaging using the ARM 9 single board computer as
the development platform. A customized webcam is used for capturing the vein
images. These images are low in contrast and clarity, therefore, contrast enhance-
ment histogram equalization algorithm is tested using Scilab tool. The results
are compared and implemented on the hardware. The hardware comprises of the
Friendly ARM mini2440 SBC, customized IR sensitive camera, VGA monitor and
a limb resting base. The software implementation is based on the Linux kernel
and Qt framework with porting of cross-compiled OpenCV and Gui libraries. Ow-
ing to the use of open source technologies and choosing embedded linux as the
development platform, the development cost has reduced tremendously.
Introduction
Developments in imaging technologies are advancing rapidly. The current state-
of-the-art technologies have provided new insights and capabilities which were
never known to mankind before. A huge progress is made in the field of biomed-
ical imaging technologies but generally have resulted in high product costs. As
compared to infrared imaging, significant amount of work is done in other areas
of imaging techniques. The use of infrared imaging technique is a relatively less
explored area and it promises to deliver high-end results at low development costs.
The major clinical problem faced by the physicians is difficulty in accessing veins
for intra-venous drug delivery. It is relevant that in case of pediatrics, obese, dark
toned people and sometimes in adult patients, locating veins becomes a very dif-
ficult task. Unnecessary puncturing of veins is done by the physicians because
the visibility of veins is not clear. Therefore this causes various problems to the
patients and especially in children. The results are swelling, irritation, leaking of
blood and blackening of the skin. Although a significant amount of work has been
done in this area and devices like Accuvien have come up, but the major problem
lies in their cost and portability.Therefore, a low-cost, portable, compact and effi-
cient infrared imaging detection system is the need of the hour. In this report, the
system implememtation and development using embedded linux on ARM9 SBC
is described and the details of the work is explained.
The Need of Vein Detection
When doctors are treating trauma patients, every second counts. Bruises, burns
and other physical injuries make it difficult to locate veins and administer life
saving drugs or solutions. In such cases it becomes very necessary to have a device
that detects the exact location of veins. Also in case of blood transfusion, blood
donation, blood withdrawal, etc. it is necessary to know the exact position of the
veins. Even trained nurses and doctors many times find it difficult to exactly locate
the blood veins, on the first hit, especially for obese people. In various medical
situations, the exact location of veins needs to be identified.
System Overview
The subcutaneous vein detection system is based on the concept of infrared tech-
nique which uses infrared as the optical source to capture vein images, processes
(enhances contrast) these images, and displays them on screen. A vein imaging
and detection system has been implemented successfully using the ARM 9 sin-
gle board computer as the development platform. A customized webcam is used
for capturing vein images which has been interfaced to the board. Thereafter,
contrast enhancement by histogram equalization method is done on the captured
image and finally the better contrast enhanced image is displayed on the monitor.
These images can also be projected on the limb. This type of non-invasive system
will provide an easy access to the location of veins for giving drug delivery and
will aid the doctors in making the process of intra-venous injections less painful
and more efficient.Refer Figure 3.1
Infrared technique
In many medical practices, X-Ray and ultrasonic scanners are used to form
vascular images. Whilst these methods can produce high quality images, it is an
invasive technique as it requires injection of agents into the blood vessels. Infrared
is a non-invasive technique and is capable of capturing subcutaneous veins, i.e.
veins on the surface of skin. Therefore by exposing the subjects vein to infrared
illumination of a specific wavelength, vein images can be captured and analyzed.
There are two types of infra-red imaging techniques: Far-Infrared (FIR) and Near-
Infrared (NIR). As will be discussed in later sections, Infrared imaging in these
two regions is capable of capturing the superficial or the subcutaneous veins inside
the human body. It provides a contactless, non-invasive method and requires no
injection of any agents into the blood vessels. Hence, by far it is the best known
non-contact, non-invasive method to capture vein images. NIR gives better results
for vein detection because of its certain attributes as compared to FIR, [18].
Absorption
Most of the absorption in the wavelength range of interest, 400-1000 nm, is by the
various pigments and enzymes in the cells, by water and by body fats. The major
chromophores are: melanin, which is found mainly in the skin, haemoglobin, biliru-
bin and beta-carotene in the blood, myoglobin in muscle cells, and the cytochromes
which are found mainly in the mitochondrial membranes. The absorption of water,
as can be seen in the above Figure, has a minimum at 500 nm, with a reasonably
low value in the wavelength range from 200 to 900 nm. Outside this range the
absorption rises strongly. This low absorption region gives rise to what is often
called the ’window of transparency’ or the ’optical window’ in the tissues. Out-
side this region very little light can penetrate the tissues. The difference in the
absorption coefficients lies in the oygenation of the blood vessels. The veins carry
the de-oxidized blood due to which they absorb the radiation completely, and the
arteries which carry the oxydized blood become almost transparent. The Figure
3.4 shows the interaction of human tissue with light.
Embedded Systems in Biomedical Applica-
tions
Embedded Systems in the field of medicine have been for a long time. Start-
ing from sensing and measurment of the patient parameters, monitoring, clinical
diagnosis to the specialized communication links, embedded systems play a very
important role in medical systems too. Examples of such embedded devices are
pacemakers, non-invasive blood monitoring systems, arterial blood gas monitor
etc. Its only been a decade since the embedded systems have started gaining pop-
ularity due to recent technological advances in fabrication of more tiny powerful
processors. Small devices like blood insulin tester, electronic thermometer all em-
plot embedded devices. The recent trends of medical devices prove that embedded
systems have drastically changed the role of doctors in healthcare sector. Without
medical devices, procedures like examination, clinical diagnosis, monitoring and
control are not possible solely with the presence of a doctor. Now the medical
practioners and medical devices share a symbiotic relationship due to which nei-
ther can work without each other. The future of embedded devices in medicine
lies in the plug and play reconfigurable embedded component for interface beteen
different spheres of medicine, laying a foundation for biomedical applications.
Toolchain
A toolchain is collection of software that helps in converting High Level Lan-
guages like C/C++, ADA, Pascal to machine level code that can be executed by
the micro-processor/micro-controller. It is a collection of tools such as compiler
and binutils programs. A simple software development toolchain consists of a text
editor for editing source code, a compiler and linker to transform the source code
into an executable program, libraries to provide interfaces to the operating system,
and a debugger. The cross-toolchain for the class of 8/16 bit HARVARD architec-
ture micro-controllers like 8x51, Z80 etc. is the SDCC (Small Device C Compiler)
The cross-toolchain for AVR class of micro-processors is AVR-GCC. The cross-
toolchain for ARM architecture is mainly provided by ARM-GCC but there are
various versions of it. The toolchain used for the development of the system is
GNU ARM toolchain v4.3.2.
ARM Architecture
ARM is a 32-bit Reduced Instruction Set Computer (RISC) instruction set ar-
chitecture (ISA) developed by ARM Holdings. It was known as the Advanced
RISC Machine, and before that as the Acorn RISC Machine. The relative sim-
plicity of ARM processors makes them suitable for low power applications. As a
result, they have become dominant in the mobile and embedded electronics mar-
ket, as relatively low-cost, small microprocessors and microcontrollers. In 2005,
about 98% of the more than one billion mobile phones sold each year used at
least one ARM processor. As of 2009, ARM processors account for approximately
90% of all embedded 32-bit RISC processors and are used extensively in consumer
electronics, including PDAs, mobile phones, digital media and music players, hand-
held game consoles, calculators and computer peripherals such as hard drives and
routers. Prominent ARM processor families developed by ARM Holdings include
the ARM7, ARM9, ARM11 and Cortex.
Single Board Computer
In order to drive any GUI and provide specific features on the embedded device,
we need some hardware which is capable of delivering such tasks. For eg. an
embedded device which does dedicated video processing and has a camera interface
along with a display interface may require considerable RAM and good processing
power (maybe a DSP core too). Lots of these things can be taken care of by the
use of SBCs which provide ample amount of processing power and a wide array of
peripheral interface choices as required by us. They come in various configurations
and literally are just scaled down versions of the desktop computers.
Physical Design
A lamp stand with adjustable height is used for integrating the whole lighting
system which comprises of the LED source and the camera. The camera is mounted
using screw arrangement at the top and the LED assembly is kept below. The
position of the assembly is kept in such a way, so that minimum scattering of
raditaion takes place. The limb under observation is kept at the base of the stand.
A base limb resting assembly is designed using acrylic material and additonal
reflectors can be attached for getting a concentrated radiation over the region of
interest. Moreover a switch is provided for switching on and off the LED source
as required. Hence the complete arrangement of Subcutaneous Vein Detection
System is shown in Figure 4.9.
Software Implementation
Before defining the software requirements, let us take a look at the basic flow
of the process of Subcutaneous Vein Detection System, figure 5.1. The first task
of the system is to switch on the camera and start the application. After the
startup, the camera will start capturing images, the image will get stored in the
board and after that image processing is done on those images using the histogram
equalization algorithm. Finally the processed contrast enhanced image is displayed
on the monitor.