BALTIMORE-The advent of spiral CT offers advantages over regular
CT scans, Elliot K. Fishman, MD, said at a conference sponsored
by the Johns Hopkins School of Medicine, where he is professor
of radiology and oncology.
With spiral CT, Dr. Fishman said, a scan can be completed in a
single breathhold, minimizing inconsistencies. By keeping the
x-ray turned on and moving the patient, the entire abdomen can
be scanned in only 32 to 40 seconds. This faster throughput improves
patient cooperation and compliance.
More important, spiral CT creates images with close interscan
spacing. Data accumulate as volumes, not slices, so radiologists
can sample data at any interval. "Compared to standard dynamic
CT," he said, "spiral CT offers increasedsensitivity,
more accurate staging, and an increased role in patient care."
Recent advances in spiral CT scanning have highlighted the liver
(Figures ), he said. With CT, optimal lesion detection requires
separate scans of both arterial and venous phases, to increase
the chance of detecting both hyper- and hypovascular tumors. Now,
a single spiral CT scan can do both at the same time.
Equipped with a Silicon Graphics work station, Dr. Fishman has
used real-time 3D rendering to create vascular maps in less than
10 minutes. "Spiral CT costs only $500 to $600 per scan,
compared to $3,000 to $4,000 for an angiogram," he said.
"It provides the same information but is far less invasive."
While standard CT usually maps data at 8 mm intervals, spiral
CT can go down to 4 mm without additional radiation dose or scan
time. This has increased detection by 10% and accuracy by almost
a third in both the liver and lung.
Once the lesion is found, Dr. Fishman said, the objective of scanning
shifts to patient management. "You can create 3D imaging
maps to assess resectability, plan surgery, or simulate surgery
Spiral CT is proving useful in other disease sites. Research from
Japan into gastric carcinomas, for example, indicates that the
technique can look at the depth of invasion of the gastric wall.
Spiral CT has also been used to help maximize cortical-medulla
differentiation in kidney tumors. For pancreatic cancer, it has
proved to be better than 95% accurate in detecting lesions, and
85% accurate for staging. "Overall," he said, "spiral
CT offers a tremendous opportunity for surgical planning, monitoring,
and rapid tumor volumetrics."