1
Virtual Colonoscopy: The Inside Story
David J. Vining
My inspiration for developing virtual colonoscopy (VC) was born of the mar- riage of two very different technologies—each significant in its own right but never before brought together. As a Winthrop fellow in Body Imaging/3D Imag- ing research at the Johns Hopkins Hospital from 1992 to 1993, I was exposed to many new and exciting technologies, including the introduction of spiral com- puted tomography (CT) scanning and the latest in virtual reality (VR) computer processing. It occurred to me early on that the computer technology I used to op- erate a flight simulator game on my home computer might also allow me to nav- igate the volume of data provided by spiral CT. In other words, combining these two technologies would enable me literally to travel inside the human body.
It was not until July 1993 that I began serious research into the development of VC. In my pursuit of an academic career, I interviewed with over half a dozen institutions, sharing with each department chairman my crazy idea to “fly inside the bowels.” Only one individual took me seriously, however—C. Douglas May- nard, MD, Chairman of Radiology at the Bowman Gray School of Medicine of Wake Forest University.
When confronted with my request for expensive computer equipment, Dr.
Maynard responded “No problem. Tell me what you need.” I asked Dr. May- nard, “How about $25,000 to start?” and he quipped, “No problem!” I countered with “$50,000?” and “$75,000?” only to hear “No problem!” each time. Finally, I challenged him with “How about $250,000?” to which he said calmly, “That might be a problem, but I’ll work on getting it for you.”
When I arrived at Bowman Gray in summer 1993, Dr. Maynard had over
$100,000 of equipment and software waiting for me in a dedicated research lab- oratory. He told me to “Go to work and do good things.” Eventually, Dr. May- nard’s original investment led to more than $5 million in research funding and more than a dozen US patents. His vision, generosity, and support made it pos- sible for me to create and develop an entirely new segment of the health-care in- dustry, now widely recognized as virtual endoscopy.
The essence of VC is simply to cleanse a patient’s bowels, distend the colon with gas, scan the abdomen and pelvis with spiral CT, and use computers to con- struct a 3D virtual environment of the colon. The system allows a radiologist to 1
fly through the colon to look for polyps and masses. One of my brave radiology colleagues, David Gelfand, MD, volunteered for the first “virtual colonoscopy”
examination in September 1993. Dr. Gelfand underwent a standard bowel cleans- ing regimen and allowed me to insert a barium enema catheter into his rectum and insufflate his colon with room air using a hand-bulb insufflator. The spiral CT scan was performed on a General Electric HiSpeed Advantage Helical scan- ner that took approximately 50 seconds to complete with 5-mm collimation at 2:1 pitch.
The overall computer processing time required to generate the first VC fly- through took more than 8 hours to complete using a Silicon Graphics Crimson computer and Explorer software. Since then, there have been substantial im- provements in several key technologies—a multislice helical CT scan now takes about 15 seconds to cover the abdomen and pelvis, and image analysis can be completed in approximately 10 minutes. However, in the early days there were many challenges such as the absence of the DICOM image standard required for proprietary CT images to be extracted from the scanner and transferred to the Silicon Graphics computer during a pain-staking operation. The computational power required to process the 250 Mb of CT data (500 images reconstructed at 1-mm intervals) was substantial for that time, so the data had to be divided into
“colon segments” to perform segmental fly-throughs. Thankfully, technology has advanced a long way since then!
In February 1994, Dr. Gelfand and I presented the first VC fly-through video accompanied by the sounds of Wagner’s “Ride of the Valkyries” at the annual meeting of the Society of Gastrointestinal Radiologists held in Maui. Needless to say, the audience was left with a lasting impression.
The next public VC presentation occurred at the National Cancer Institute’s International Workshop on Colorectal Cancer Screening held in Bethesa, Md, in June 1994. This 3-day multidisiplinary conference covered all aspects of col- orectal cancer research, prevention, diagnosis, and treatment. The gastroenterol- ogists in attendance were having a great time bashing the radiologists’ defense of the barium enema. When I introduced the VC concept at that meeting, I be- gan my presentation with, “It’s the bottom of the 9th inning, score is 3 to 0 in favor of the gastroenterologists, bases are loaded, and a new radiologist is up to bat.” It was clear that the gastroenterology community, after seeing VC in ac- tion, realized that a new radiological procedure could impact the future of their practice.
Grants awarded from the North Carolina Baptist Hospital in 1993 and by the National Science Foundation in 1995 supported my continuing research in the field. Since those early days, researchers at Wake Forest University, as well as from around the world, have pursued improvements to the VC procedure, in- cluding the use of volume rendering, stool opacification and subtraction, elec- tronic carbon dioxide insufflators, and computer-assisted diagnosis (CAD) of colon polyps. However, most practitioners of VC today agree that 2D review of CT images at a workstation is sufficient for lesion detection and that 3D imag- 2 Chapter 1. Virtual Colonoscopy: The Inside Story
ing can be reserved for problem solving (e.g., determining if a suspicious find- ing represents a true polyp or merely a complex haustral fold).
The first commercial VC product to appear on the market was General Elec- tric’s Navigator, introduced at the Radiological Society of North America’s an- nual meeting in November 1995. Today, more than 20 virtual endoscopy prod- ucts are available.
Future Developments
Future challenges for VC are not necessarily technical in nature but related more to economics and public policy. Acceptance, pricing, reimbursement, and com- peting technologies are all major hurdles to be overcome. The public is enam- ored by this new VC procedure, but the medical community and public policy groups are more cautious with their support—convincing evidence from large- scale clinical trials comparing VC to conventional colonoscopy will be neces- sary to sway these groups in favor of VC. Affordable pricing for the VC proce- dure, especially to make it competitive against other available colon screening methods, will require consensus among radiology practices. Finally, it is impor- tant to recognize the fact that evolving technologies, such as stool screening for DNA markers, could also impact the value of VC as a screening tool. Never- theless, VC is poised today to make an important contribution in the fight against colorectal cancer, the second-leading cancer killer in America.
David J. Vining 3
