Communications - April 2009

is being addressed in a technique called low dose, which Kaufman’s group is researching, with a grant from the National Institutes of Health (NIH). Another drawback of a virtual colonoscopy is it can’t remove polyps; patients still need an optical colonoscopy for their surgical excision. However, a virtual colonoscopy study has shown that only about 7% of patients required such follow-up.

Insurers, however, have been slow to catch on. Medicare, for example, announced a tentative decision earlier this year to not pay for virtual colonoscopies. And some insurers have setup the payment codes that healthcare providers need to be reimbursed for the procedure, but the money has yet to materialize. However, Kaufman says the political will to mandate coverage is growing, and patients can pressure their insurer to pay for a virtual colonoscopy by refusing to undergo optical colonoscopy.

early Detection

Screening is critical because a patient’s successful outcome often hinges on the early detection of polyps. A virtual colonoscopy removes many of the uncomfortable hurdles. “Only 15%–19% of individuals eligible for screening currently undergo colon evaluation,” says Hiroyuki Yoshida, an associate professor at Harvard Medical School and director of 3D Imaging Research at Massachusetts General Hospital. “The cathartic cleansing required for bowel preparation is the biggest barrier.”

A virtual colonoscopy still requires preparation, so developing a laxative-free procedure will be indispensable to its practicality, Yoshida says. One hitch: eliminating laxatives leaves more fecal matter in the colon, which requires improvements in electronic cleansing. What’s more, patients still must ingest an oral contrast agent, such as barium or iodine, and air or carbon dioxide must still be used to distend the colon. Yet, a laxative-free virtual colonoscopy could be ready for public use in the near future, Yoshida says.

Many of the challenging issues with virtual colonoscopies involve software applications. Computer-aided detection (CAD), the focus of Yoshida’s re-

Virtual colonoscopies
could become
more available
in remote places
via telemedicine.

search, brings much-needed automation to electronic cleansing and polyp detection. It holds great promise, says Kaufman. “In mammography, this has been entirely successful,” he notes. “Basically, the computer is another set of eyes.”

Skill in interpreting diagnostic images varies among radiologists, who can mistake the colon’s normal valves and folds for polyps. Yoshida says CAD could make results more objective and consistent, and shorten radiologists’ learning curve. It could also be useful in hospitals that lack expertise with virtual colonoscopies.

However, CAD presents its own challenges. “Sometimes CAD’s weak spots are comparable to human viewers’ weak spots,” says Dr. Ronald Summers, a radiologist and senior investigator at NIH. One important challenge is detecting flat lesions, which are more difficult to detect with a virtual or optical colonoscopy, but constitute a higher risk for cancer.

Kaufman has co-developed a novel CAD technique, utilizing colon flattening and volume rendering, which has achieved perfect sensitivity and tolerable specificity, and could function as either a first or second reader.

Another problem is false positives: they require patients to undergo an optical colonoscopy. Of course, false positives aren’t as deadly as false negatives, and doctors can dismiss false positives with a second read. Ideally, Kaufman says, CAD should be a first reader for radiologists, who can inspect the regions flagged by it. “I think the second read is the one the radiologist should use, because it has the highest sensitivity, but we’re still working that out,” Dr. Summers says.

There is also considerable debate

Technology
TechFest
2009

microsoft research unveiled more than 100 innovations at its annual techfest showcase in late february in redmond, Wa. among the emerging technologies projects were:

SeconDLiGht
used with microsoft Surface,
Secondlight can project images
and detect gestures in mid-air
above Surface’s display (in
addition to supporting its
multitouch capabilities). the
magic behind Secondlight
involves Surface’s lcd screen
that can switch between opaque
and translucent, alternating
60 times per second. a pair of
recessed projectors alternate
flickering 30 times per second,
with one projector timed to
illuminate the screen when
it is opaque and the second
projector timed to illuminate
when it is transparent. When
the screen is transparent, any
object held above the screen will
reveal what is being output by
the second projector.

RenLifAnG
When you conduct a Web search
for information about a specific
person—say, an ex-girlfriend—
you still need to examine all
of the search results and piece
together the information
before being able to ascertain
the parameters of her social
universe. renlifang is a Web
entity-summarization system
that automatically creates a
biography page of the person;
a social-network graph for the
person; a shortest relationship
path between the person and
someone else; titles for the
person found on the Web; and
all of the structured information
that microsoft possesses on the
person in its local database.

ReAL-time StitchinG of
moBiLe-GeneRAteD ViDeoS
microsoft demonstrated a real-
time video-stitching system from
multiple mobile phones that
produces a wide field-of-view
experience with high resolution.
Possible applications include
citizen journalism; virtual
attendance of family events and
gatherings; and emergencies
in which citizens provide a
real-time video feed for first
responders before they reach the
scene of the emergency.