Vivid Images from 3-D Scans Give Seattle Children's Doctors a Powerful Diagnostic Tool
Following his operation, Jay's headaches waned and the bulge above his eyebrow retreated.
Jay, 12, had just completed a CT (computerized tomographic) exam to check the outcome of an earlier surgery. This was no ordinary CT exam, though.
Thanks to advancements in CT technology and a sophisticated 3-D imaging system, the exam was not only many times faster than a conventional CT, it produced far more vivid — and valuable — images.
"Just awesome," says Lona Jensen of the detail revealed by the images.
How awesome? "It blows away what we were working with before," says Dr. Raymond Sze, Seattle Children's radiologist.
While the system's gee-whiz quotient is off the charts, its many practical advantages over previous imaging technologies — speed, accuracy, versatility — are what have Seattle Children's physicians so excited about the hospital's high-speed scanner and powerful Vitrea 2 computer workstation — the only such three-dimensional imaging system at a pediatric hospital in the region.
Dr. Michael Cunningham
"We're making diagnoses we otherwise wouldn't have been able to make," says Dr. Michael Cunningham, director of Seattle Children's Craniofacial Center.
The emergence of 3-D imaging is the latest step in the evolution of CT technology. The basics remain the same: Patients lie still on a moving couch that is advanced through the rotating X-ray beam of the scanner. Data from the scan are then fed into a computer, which creates composite images of the patient's anatomy.
That's pretty much where the similarities between conventional CT imaging and CT with 3-D imaging stop. Conventional CT imaging produces flat, black-and-white cross-sections with limited depth information.
The new 16-slice multi detector CT captures more detailed data, enabling the Vitrea 2 workstation to create realistic color images bursting with depth, context and detail — all of it invaluable for diagnosis.
Dr. Sze recalled the reaction of a group of Children's surgeons as they witnessed their first demonstration of the Vitrea 2's wizardry: "You could almost hear the thunk of their jaws hitting the floor."
Our multidisciplinary team provides diagnosis and long-term management for children with craniofacial abnormalities. We have a large craniofacial team of 39 healthcare providers from 19 specialty areas, dedicated to the care of children with craniofacial conditions.
Each child is assigned a craniofacial pediatrician who coordinates the care provided by the other team specialists and tailors a plan to each child's situation.
Surgical techniques developed by our craniofacial surgeons are revolutionizing the way craniofacial surgery is done all over the world.
These innovative procedures enable doctors to address even the most serious and complex craniofacial abnormalities and provide the benefits of a more normal appearance for an increasing number of children.
Getting a Better Look
Connor Wakefield, the 5-month-old son of Wes and Kira Wakefield, was born with craniosynostosis, a condition in which a portion of the plates that form the skull are fused, potentially interfering with the normal growth of the skull and development of the brain.
In Connor's case, the fused plates are inside his left orbit, behind his eye — a rare form of the disease that is virtually impossible to see in two-dimensional CT scans. By providing the element of depth and anatomical detail, magnified images from a 3-D scan indicated the precise location of the tiny fusion, setting the stage for an upcoming surgery.
"The images speak for themselves," says Wes Wakefield. "Without this technology, they never would have been able to pinpoint the problem."
Figure 1 shows how Conner's head is misshapen.
Other examples of the system's applications abound. Hydrocephalus — sometimes called water on the brain — is a condition in which fluid builds up within the brain.
Surgeons typically install a shunt to drain the excess fluid away and prevent brain damage. Traditional methods for determining whether fluid levels have changed have an accuracy range of ±20-30%, says Dr. Sze.
Using a 3-D volume-calculation feature of Vitrea 2, Dr. Sze and Victor Ghioni, Children's chief CT technologist, developed a highly accurate technique to measure the volume of fluid within the brain to determine if the shunt is working.
The system also helps surgeons address situations in which a child's facial structure is pushed too far inward.
Correcting the condition involves separating the facial bones from the skull and attaching a metal halo around the child's head, explains Dr. Richard Hopper, a craniofacial surgeon at Children's.
Over time, the halo slowly moves the entire face forward, a procedure known as distraction osteogenesis. Prior to surgery, 3-D imaging is used to determine the best angles at which to make the cuts.
After surgery, 3-D images help determine when the time is right to remove the halo.
Although Seattle Children's has utilized a version of 3-D imaging for more than 10 years, the current system is a quantum leap forward. The old system worked well with bone, but not soft tissue.
The current system excels with both. Better still, the system enables CT technologists to magnify, isolate, dissect or rotate images to reveal precisely as much or as little as doctors want to see and provide perspectives that would otherwise be impossible to obtain.
"You can take those images and do pretty much anything you want to do with them," says Dr. Hopper. "It's hard to imagine life before Vitrea. It's become a common tool now."
The clarity of the 3-D images also improves communication between doctors and patient families. "I can show a family what's wrong with their child and they can understand it easily," says Dr. Cunningham.
In Jay Jensen's case, his clinical diagnosis was clear — arteriovenous malformation (AVM), in which a spidery mass of blood vessels forms in a concentrated area.
A bright red mass covered the left side of his face and created a bulge above his eyelid, marring his appearance, wrecking his vision and causing severe headaches.
The super-accurate 3-D images from an angiogram performed with the high-speed scanner — impossible with older, slower scanners — helped surgeons better plan Jay's delicate surgeries.
Dr. Raymond Sze
Angiograms involve injecting contrast (X-ray dye) that highlights blood vessels as the dye passes through them. The CT scan is taken of the targeted area.
Since the dye remains in one place for only a few seconds, the window to acquire images is small. Conventional CT technology is too slow to capture the dye within the blood vessels before it flows away.
By capturing 16 slices per half-second, the high-speed scanner gets the job done before the dye disappears.
The use of CT angiograms in AVM cases has become one of the leading applications for 3-D imaging. "Normally, we can't see all the blood vessels clearly," says Dr. Jonathan Perkins, a head and neck surgeon with Children's Vascular Anomalies program.
"With a CT angiogram, it lights up very clearly. I can look at it and get a grasp on what needs to be done."
Speed pays other dividends as well. With the high-speed scanner, CT exams that once took many minutes to complete now take less than 10 seconds, reducing the need to sedate fidgety young patients.
Radiation exposure is also limited, because the speed of the scanner reduces the need for repeat imaging due to patient motion. Because the images can be rotated for any point of view, patients needn't repeat exams when doctors want more than one perspective.
While 3-D imaging was always theoretically possible, it didn't become practical until computers became fast enough and powerful enough to capture and process the additional data needed to account for density and add the dimension of depth to images that previously featured only length and width.
The result is a vivid, selective and enlightening virtual window into patients that even surgery can't always provide. "It's as if you could reach into a patient and remove a piece of bone or tissue and examine it in your hand," says Ghioni.
In fact, the system's data can be translated into physical models that enable doctors to create synthetic reproductions that are so realistic surgeons can rehearse upcoming operations.
Just as important as presurgery preparation is postsurgery evaluation — another instance in which the superior visuals produced by 3-D imaging paint a more telling picture for patients.
In the months following a September 2002 operation to remove the mass of blood vessels from his face, Jay's headaches waned, his skin regained its normal color and the bulge above his eyebrow retreated, leading him and his mother to cross their fingers that the AVM was gone for good.
Victor Ghioni, chief CT technologist
Their faith was confirmed in April of this year, when 3-D images from a follow-up exam — taken in preparation for a surgery by Children's head of plastic surgery, Dr. Joseph Gruss, to remove the last tiny mass of blood vessels and repair a droopy eyelid — revealed no evidence the mass was regrowing.
"You could definitely see the difference between the first set of images and the latest set of images," says Lona Jensen. "I'm not sure who invented 3-D imaging, but I'm sure glad they did."
Understanding What We See
Not only does 3-D imaging help Children's radiologists and their colleagues see what's wrong with their patients more clearly, it is also a powerful catalyst for research.
Currently, Dr. Raymond Sze is working with computer scientists and electrical engineers at the University of Washington to develop tools that better analyze the information captured by the 3-D imaging system.
"We hope these tools will identify specific shapes and measurements that will predict how patients are going to do, what complications they might have and how they will respond to various therapies," he explains.
Tools that quantify and categorize various conditions will enable doctors to look for patterns, including genetic links, that can help them understand potential causes — and treatments.
Although Dr. Sze is focusing on craniofacial abnormalities, the tools he hopes to create could potentially apply to any bone, tissue or organ. "Radiologists are always pushing for better and more accurate images.
Right now there is a need to better understand what the image we see actually means," he says.