Summary
Diseases of Gastro Intestinal tract such as intestinal bleeding and ulcer are very common in order to determine the local of the disease as well as diagnose the problem various techniques are using. But those are not a dedicated for that purpose. This paper discuss the various techniques with merits and demerits and a comparison with the novel, dedicated technique called wireless capsule endocopy(WCE) for GI Tract visualization. WCE is a pill sized device for the patient to swallow. It equips with a camera and a wireless transmitter so that as it travels to the patient’s GI tract it takes pictures of the GI tract and transmit the information out wirelessly.
Introduction
Basic curiosity of human being to look inside and understand the human body dates back to prehistoric times and in this day and age is of diagnostic relevance .It has led to the development of a variety of technologies to imaging nuke and corners of the human body for medical purposes. The development of radiology and extensive use of X-ray imaging during the second world war, and the advent of the digital computer and new imaging modalities like Ultrasound and Magnetic Resonance Imaging have combined to create an explosion of diagnostic imaging techniques in the past 25 years. In the early 1900s, the first attempts to view inside the body with lighted telescopes were made and these initial devices were often fully rigid. In the 1930s, semi-flexible endoscopes called gastro scopes developed to visualize the GI tracts .
The gastrointestinal (GI) tract consists of 4 feet long esophagus, followed by 20 ft of small bowel and the last 6 feet is of colon. The digestive system plays an important role in four major functions: ingestion, digestion, absorption, and elimination of food and do away with waste.
Commonly diagnosed diseases and disorders of GI tract are :
Swallowing problems
Reflux symptoms (dyspepsia or heartburn)
Abdominal pain
Diarrhea
Unexplained vomiting, weight loss, or bleeding
Colon polyps
Tumors
Technologies for diagnosing GI tract
There are invasive and non invasive methods available to diagnose the GI tract. Non invasive technique involves sophisticated machineries to imaging and diagnoses the GI tract. At the same time breaching of skin is not necessary. Due to this advantage non invasive technique has an upper hand in GI tract visualization techniques. hoes techniques can be summarized as
Non-Invasive Methods
Radiological instruments like X-ray, MRI, PET and different type of endoscope techniques comes under non-invasive methods.
1.Radiological Instruments
1.1 X-ray
The invention of X – ray by a German physicist Wilhelm Conrad Roentgen in1895 revolutionalised the medical diagnosis field. In 20th century, pre era of cross sectional imaging radio graphical image of the GI tract was limited to the plane film. A major development along the way was the application of pharmaceutical contrast medium to help visualize organs and blood vessels with more clarity and image contrast.
Several types of X-ray tests are available to view the GI tract including: Barium swallows, Modified barium swallow, Upper GI series, Small bowel series, SBFT Barium enema, Air contrast barium enema (double contrast barium enema)
1.2 CT SCAN
In the mid 1970s Computed tomography (CT) - at times called CAT (Computed Axial Tomography) scanners revolutionized the medical imaging.
CAT uses x-rays and complex computers to create a cross sectional slice of the body examination of the gastrointestinal tract requires a contrast agent to enhance the visibility of certain tissues. CT is often the preferred method for diagnosing many different GI tract cancers, including colon cancer.CT Coronagraphy (virtual colonoscopy) is an enhanced abdominal CT scan where computer reconstruction allows detailed longitudinal 3D examination of the bowel for polyps, cancer, or other disease
Benefits
The units are comfortable for the patient and software development has permitted imaging techniques that were not available just a few short years ago.
1.)CT scanning is painless, noninvasive, accurate, fast and simple.
2.)High accuracy enabling faster treatment and often eliminating the need for additional, more invasive diagnostic procedures.
3.)CT scanning offers detailed views of many types of tissues.
4.)CT scanning can identify normal and abnormal structures, making it a useful tool to guide radiotherapy, needle biopsies and other minimally invasive procedures.
5.)CT is a cost-effective imaging tool for a wide range of clinical problems.
Risks
At the same time this technology involves many risks such as:
1.)Exposure to radiation in the form of x ray is the major risk, but the benefit of an accurate diagnosis far outweighs the risk
2.)Contrast administration is not safe for nursing mothers.
3.)Pregnancy is a contra indication for under going this procedure.
4.)Some people may have an allergic reaction to the dye.
5.)In rare cases, the dye can cause further kidney damage in people who already have kidney problems
6.)Inflating the colon with air could injure or perforate the bowel. This has been estimated to happen in less than one in 2,000 patients.
7.)CT colonography provides a black-and-white picture of the bowel wall. The lack of true-color images makes it more difficult to assess lesions
1.3 Magnetic Resonance Imaging (MRI)
An equally impressive technology, Magnetic Resonance Imaging or MRI, has greatly improved the sensitivity and specificity (accuracy) of diagnostic imaging. A great advantage of MRI is that the patient is not exposed to x-rays. The images are created with the use of strong magnetic fields, radiofrequency transducers (commonly called coils), and computer assisted image processing.
Advantages
1.)Patients feel no pain during the MRI examination.
2.)MRI uses non-ionizing radiation, and has a high soft-tissue resolution
3.)Direct multiplanar imaging, slices in the sagittal, coronal and oblique directions can be obtained directly.
4.)It can also provide both morphological and functional information.
5.)To date, no ill health effects have been reported by use of super conducting magnets or radio frequency pulses in the diagnostic range.
Disadvantages
1.)MRI takes much longer time to construct an image
2.)MRI signal is inherently of low sensitivity because it is based on a very weak non-ionizing radio frequency phenomenon
3.)This test is not safe for the patients with implanted pace maker and metallic particles
1.4 Positron Emission Tomography (FDG PET)
Over the past decade positron emission tomography (PET) has changed from a research tool to a full-fledged clinical tool. ‘In this technique a chemical compound with desired biological activity is labeled with a radio active isotop that decays by emitting positron or positive electron’.The concept of this technology is based on the fact that tumor cells have a greater avidity for using glucose via glycolysis than most non-cancerous cells.
In the gastrointestinal tract PET-CT is used mainly for oncological applications and has been shown to have greater overall accuracy and cost-effectiveness compared to other imaging modalities. PET-CT in the GI tract is commonly sed for initial staging, response to therapy and detection of recurrence of esophageal, gastric, colorectal, and gastrointestinal stromal tumors. Additional applications that are showing initial promise include the evaluation of Crohn’s disease.
This modality also has health hazards due to the radiopharmaceuticals used in such cases.Also the resolution of PET is very poor
2. Endoscopy
2.1 Regular Endoscopy
An endoscope is a device by means of fiber optics and powerful lens systems to provide lighting and Visualization of the interior body organs.
The introduction of endoscopy is one of the biggest success stories in the history of medicine. As a concept, endoscopy was developed nearly a hundred years ago in Germany by Dr. Adolf Kussmaul1 . He used a rigid stainless steel tube, a rather crude instrument, causing a lot of discomfort to patients. The very thought of endoscopy was scary because over half of those undergoing the procedure would end up with major complications such as a perforated food pipe or stomach.
Main disadvantages are
1.)Endoscopy carries a risk of perforation of the bowel
2.)Need to study the colon separately using colonoscopy
3.)During colonoscopy, the scope may not be able to get all the way around to the caecum so the examination is incomplete
4.)The main indication for endoscopy of the upper gastrointestinal tract is the suspicion of stomach pathology, which may be benign or malignant, and the procedure allows to do biopsies or resections.
Enteroscopy
Enteroscopy allows for the examination of a good portion of the upper small bowel via the use of an extended length endoscope. It is about two and a half times as long as a standard upper endoscope. It is typically used to identify and treat potential sources of bleeding in patients with acute or chronic anemia believed secondary to gastrointestinal bleeding in whom a previous endoscopy and colonoscopy have been normal. In addition, enteroscopy may be performed in patients with suspected mucosal disease of the small bowel, with tissue biopsies being obtained at the time of the procedure.
2.2 Ultrasound Endoscopy
Ultrasound is defined as sound with a frequency greater than 20,000 cycles/sec (20KHz), which is the upper limit of audible sound. Major applications of ultrasound include obstetrical imaging, abdominal imaging, and Doppler imaging, a variant technique used in heart and vascular diagnosis. In some instances, biopsies are performed under the guidance of ultrasound, permitting more accurate and less invasive tissue sampling.
Endoscope Ultrasound, also known as EUS, combines ultrasonic imaging capabilities onto a flexible video endoscope. EUS arose from the ability to mount an ultrasound processor on the tip of an endoscope. The prototype device, known as an echo endoscope, was developed in the early 1980's. With technical improvements, EUS has now become an established technique in the evaluation of a variety of benign and malignant diseases.
Endoscope ultrasound may be used to determine the cause of symptoms such as abdominal pain, to evaluate a growth, to diagnose diseases of the pancreas, bile duct and gall bladder when other tests are inconclusive and to determine the extent of certain cancers of the lungs or digestive tract. State-of-the-art, EUS is the minimally invasive alternative to exploratory surgery to remove tissue samples from abdominal and other organs.
3.Wireless Capsule Endoscopy
Wireless Video capsule endoscopy or simply capsule endoscopy is an important innovation in diagnostic endoscopy. As a simple, non-invasive, ambulatory procedure, capsule endoscopy has hailed as one of the technological marvels of the millennium In this system, the patient swallows a miniature high-resolution camera that is propelled by peristalsis through the gastrointestinal tract1. It was approved in 2001 by FDA and is now widely available2 . It is particularly useful in examining the small intestine, which is difficult to visualize by conventional endoscopic techniques.
With capsule endoscopy we can view the entire small intestine without pain, sedation, or air insufflations, it has many advantages over traditional diagnostic studies.
For the first time, doctors are able to see inside of the entire six-meter-long small intestinal tract, which had previously remained beyond the reach of any diagnostic device. It has the size of an Aspirin pill and it is wirefree. A sensor and a transmitter are the foremost element of this technology and can transmit two frames per second and provides 8 hrs continuous monitoring of the small intestine.
Major Instrumentation of a Pill cam is stated below :
CAPSULE
Sub systems are Camera system and Power supply system
DATA RECORDER
Subsystems are Sensor array and signal recorder
VIEWING STATION/WORK STATION
Data processing software and Computer workstation
Procedure
The patient swallows aspirin pill sized miniature camera sum up in a biocompatible material. Natural digestive contractions help to propel the disposable pill through the GI tract, and are passed naturally and painlessly from the body, usually within 24 hours. Images and data acquired are transmitting via an array of sensors, to the Data Recorder worn around the patient’s waist. Particular software enables the physician to view and analyze the problems.
Advantages of Capsule Endoscopy
Little discomfort
100% Patient satisfaction
Ambulatory procedure
Absolutely non invasible
Does not require sedation
Immediate recovery
Offers a simple, safe and less invasive alternative
Wireless procedure.
Owing to the significance of this technology, Research and Development of Capsule Endoscopy have been running by many companies and institutions internationally
Conclusion
Though there are techniques available for GI tract visualization, Capsule endoscope is the only dedicated instrument for small bowel imaging. Compared to other techniques it has many advantages including ambulatory procedure and no sedation.
Capsule endoscopy is a superior and more sensitive procedure than barium follow-through and Entero-CT for Crohn's disease.
The video capsule endoscope was found to be superior to small bowel radiograph for evaluation of small bowel diseases
Ulcers, erosions, and polyps that are shown by capsule imaging are reported to be frequently missed by using the SBFT examination
The possibilities of Capsule Endoscopy as a platform technology are immense and have revolutionary potential. This technology is only a plateau and several variant of the capsule, on which research and trials could be possible.
For instance, if the capsule can be controlled using a joystick then can be halted, moved and directed, and its progress can be seen on a monitor.
Another possibility is if it is jet-propelled, the entire G.I. tract can be screened in less than the eight and a half hours that are required now.
A therapeutic capsule that can treat a lesion is also possible in an advanced stage of trial.
Biopsies can be done using retractable arms
Capsules are also being developed to obtain a magnified view of lesions so that detailed examinations can be carried out.
It's easy to imagine adding motility, pressure, and temperature sensors in the future.
It won’t be a romanticism to use this in vascular areas in the very near future
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