What if swallowing a pill with a camera could detect
the earliest signs of cancer?
The tiny camera is designed to take high-quality, color pictures in confined
spaces. Such a device could find warning signs of esophageal cancer, the fastest
growing cancer in the United States.
A fundamentally new design has created a smaller endoscope that is more
comfortable for the patient and cheaper to use than current technology. Its
first use on a human, scanning for early signs of esophageal cancer, will be
reported in an upcoming issue of IEEE
Transactions on Biomedical Engineering.
"Our technology is completely different from what's available now. This
could be the foundation for the future of endoscopy," said lead author Eric J. Seibel,
Ph.D., a University of
Washington research associate professor of mechanical engineering.
In the past 30 years diagnoses of esophageal cancer have more than tripled.
The esophagus is the section of digestive tract that moves food from the throat
down to the stomach. Esophageal cancer often follows a condition called
Barrett's esophagus, a noticeable change in the esophageal lining. Patients with
Barrett's esophagus can be healed, avoiding the deadly esophageal cancer. But
because internal scans are expensive most people don't find out they have the
condition until it's progressed to cancer, and by that stage the survival rate
is less than 15 percent.
"These are needless deaths," Seibel said. "Any screen that
detected whether you had a treatable condition before it had turned into cancer
would save lives."
An endoscope is a flexible camera that travels into the body's cavities to
directly investigate the digestive tract, colon or throat. Most of today's
endoscopes capture the image using a traditional approach where each part of the
camera captures a different section of the image. These tools are long, flexible
cords about 9 mm wide, about the width of a human fingernail. Because the cord
is so wide patients must be sedated during the scan.
The scanning endoscope developed at the UW is fundamentally different. It
consists of just a single optical fiber for illumination and six fibers for
collecting light, all encased in a pill. Seibel acted as the human volunteer in
the first test of the UW device. He reports that it felt like swallowing a
regular pill, and the tether, which is 1.4 mm wide, did not bother him.
Once swallowed, an electric current flowing through the UW endoscope causes
the fiber to bounce back and forth so that its lone electronic eye sees the
whole scene, one pixel at a time. At the same time the fiber spins and its tip
projects red, green and blue laser light. The image processing then combines all
this information to create a two-dimensional color picture.
In the tested model the fiber swings 5,000 times per second, creating 15
color pictures per second. The resolution is better than 100 microns, or more
than 500 lines per inch. Although conventional endoscopes produce images at
higher resolution, the tethered-capsule endoscope is designed specifically for
low-cost screening.
Using the scanning device is cheap because it's so small it doesn't require
anesthesia and sedation, which increase the cost of the traditional procedure.
"The procedure is so easy I could imagine it being done in a shopping
mall," Seibel said.
A wireless scope manufactured by a different group, originally designed to
pass through the body and detect intestinal cancer, is now being marketed for
esophageal cancer screening. The competing technology comes in a pill about the
width of an adult fingernail and twice as long. By contrast, the UW's scanning
fiber endoscope's dimensions are about half as big and the device fits inside a
standard pill capsule. The pill could be even smaller, Seibel said, but the
researchers chose a size that would be easy to handle and swallow.
Another disadvantage of wireless capsules is they only allow a single fly-by
view.
"You have no control over the other pill once it's swallowed. It just
flutters down," Seibel said. But since the UW scope is tethered, the doctor
can move it up and down along the region of interest.
Only a small percentage of people who get Barrett's esophagus, about 5
percent to 10 percent, develop cancer. So any screening method must have a low
price to be cost-effective.
"The next big challenge is to make this cheaply," Seibel said. The
researchers are negotiating a contract to commercialize the technology. In the
future they hope to not only take pictures, but also deliver treatments through
the device, and to apply it to other diseases.
Note for Esophageal Cancer
Esophageal cancer is malignancy of the esophagus. There are various subtypes. Esophageal tumors usually lead to dysphagia (difficulty swallowing), pain and other symptoms, and are diagnosed with biopsy. Small and localized tumors are treated with surgery, and advanced tumors are treated with chemotherapy, radiotherapy or combinations. Prognosis depends on the extent of the disease and other medical problems, but is fairly poor.
Dysphagia (difficulty swallowing) is the first symptom in most patients. Odynophagia (painful swallowing) may be present. Fluids and soft foods are usually tolerated, while hard or bulky substances (such as bread or meat) cause much more difficulty. Substantial weight loss is characteristic as a result of poor nutrition and the active cancer. Pain, often of a burning nature, may be severe and worsened by swallowing, and can be spasmodic in character. An early sign may be an unusually husky or raspy voice.
The presence of the tumor may disrupt normal peristalsis (the organised swallowing reflex), leading to nausea and vomiting, regurgitation of food, coughing and an increased risk of aspiration pneumonia. The tumor surface may be fragile and bleed, causing hematemesis (vomiting up blood). Compression of local structures occurs in advanced disease, leading to such problems as superior vena cava syndrome. Fistulas may develop between the esophagus and the trachea, increasing the pneumonia risk; this symptom is usually heralded by cough, fever or aspiration.
Note for Barrett's Esophagus
Barrett's esophagus refers to an abnormal change (metaplasia) in the cells of the lower end of the esophagus thought to be caused by damage from chronic acid exposure, or reflux esophagitis. Barrett's esophagus is found in about 10% of patients who seek medical care for heartburn (gastroesophageal reflux). It is considered to be a premalignant condition and is associated with an increased risk of esophageal
cancer.
The condition is named after Dr. Norman Barrett (1903–1979), Australian-born British surgeon at St Thomas' Hospital, who described the condition in 1957.
Barrett's esophagus is caused by gastroesophageal reflux disease, which allows the stomach's contents to damage the cells lining the lower esophagus. However, not every person who has GERD will develop Barrett's esophagus. Researchers are unable to predict which heartburn sufferers will develop Barrett's esophagus. While there is no relationship between the severity of heartburn and the development of Barrett's esophagus, there is a relationship between chronic heartburn and the development of Barrett's esophagus. Sometimes people with Barrett's esophagus will have no heartburn symptoms at all. In rare cases, damage to the esophagus may be caused by swallowing a corrosive substance such as lye.
The research was funded by the National
Cancer Institute and Pentax
Corp. Early funding was provided by the Whitaker
Foundation and the Washington
Technology Center. Co-authors at the UW are Drs. Michael Kimmey and Jason
Dominitz in gastroenterology at the UW
Medical Center; Richard Johnston, C. David Melville and Cameron Lee in UW
Mechanical engineering; Steve Seitz in UW
Computer Science and Engineering; and Robert Carroll, now in electrical
engineering and computer science at the University
of California, Berkeley.
