In 1980, computerized tomographic (CT) scanning was an established medical tool that some called the greatest advance in diagnostic medicine since the discovery of the X-ray. One measure of the significance of this advance was the awarding of a Nobel Prize in medicine in 1979 to the inventors of CT technology, G. N. Hounsfield and A. M. Cormack.
However, some critics labeled CT scanners expensive toys that were overused and unnecessarily increased the cost of health care.
Two Mayo Clinic radiologists, Drs. Patrick F. Sheedy, II, and Glenn Forbes, discussed some of the changes that had occurred in this field and shared some of their thoughts about the place of CT scanning, based on Mayo’s extensive experience with it.
Dr. Sheedy was one of several radiologists involved in body scanning in the department and Dr. Forbes was one of a group of neuroradiologists who carried out head scanning. Below is their interview from 1980:
In the short time that CT scanning has been in existence, has it carved out any particular role for itself in diagnostic medicine?
“I don’t know how to summarize that for you,” said Dr. Sheedy. “We have a fairly long list of disease entities that can be discovered and evaluated with body scanning.” He said that, in general, the majority of patients on which it used have either cancer or an inflammatory disease.
What are the peculiar advantages of CT scanning?
The main advantage say the doctors, is its ability to gain precise anatomical information in a noninvasive way, that is, with little risk and no pain for the patient.
Both men say that the tremendous amount of information provided by a CT scan is of great diagnostic value.
“CT scanning has shown us views of the inside of the brain, the living brain, that were literally unobtainable before,” said Dr. Forbes.
Dr. Sheedy said that CT has the unique ability to detect unsuspected disease in non-suspect organs.
“If we perform, for example, an excretory urogram—a kidney X-ray,” he explained, “we expect to view primarily the structures of the urinary tract. But if we perform a CT scan of the kidneys, besides the urinary tract, we also clearly visualize adjacent organs such as the pancreas, liver, adrenal glands, the retroperiotoneum, and vascular structures.”
Dr. Sheedy said that CT has been particularly useful with patients who have relatively vague symptoms, allowing doctors to not only diagnose a disease if present but also to confidently exclude diseases not present.
Has the advent of CT technology caused any changes in the care or diagnosis of patients?
Dr. Sheedy said that one significant change has been the alteration of indications for many diagnostic examinations and a change in the preferred sequence for performing them.
As an example, he said that before CT, a patient with a suspected liver tumor would often have had a radionuclide scan followed by an angiogram. Now, he said, the CT scan is generally performed before an angiogram because frequently what is found on the scan makes performance of the angiogram unnecessary.
Has CT scanning eliminated the need for many examinations?
Some, but its effect in this area is variable. For example, Dr. Forbes pointed out that CT scanning has almost made obsolete the performance of pneumoencephalograms—an examination in which air is injected into the brain to outline structures for better viewing; it requires hospitalization and involves some serious risks. Before CT scanning, Mayo performed 350 to 400 of these exams per year; last year, the total was less than 15.
The effect has been otherwise, however, in the case of cerebral angiograms, a test in which contrast material is injected into vessels in the brain. “CT scanning has raised many questions that we just didn’t know before and has pressed angiography to answer them. So angiography has become more complex and sophisticated, and we are doing slightly more of them than before the CT scanner,” said Dr. Forbes.
Has CT scanning reduced or added to patients’ costs?
“It’s hard to prove either way,” said Dr. Sheedy. “You gain some information from CT scanning that you couldn’t have obtained by other methods. Some of these methods are more expensive than CT, others less expensive. If it does add to patient cost, the increased cost is often more than offset by improved accuracy of diagnosis, decreased risk, and less pain.
“Could we get by with cheaper methods? Sure, but the question is, 'Are you going to get the same results?' For that matter, 'What’s a cheaper method?' Angiography is not. Radionuclide scanning is, but CT scanning is often more specific for certain disease. CT costs more than ultrasound, but in certain circumstances, it produces better results. An abdominal CT scan is more expensive than a plain film of the abdomen, but you gain much more information from the scan.”
Do you think CT scanning is being overused?
“I have a file of correspondence belonging to Dr. Russell Carman, the first chairman of radiology at the Clinic,” said Dr. Sheedy. “It contains an interesting exchange of letters with Drs. Will and Charlie discussing the question of whether the colon X-ray was being overused. That was in 1923. They were wrestling with the same philosophic problem that we are with CT scanning today. You will rarely find anyone questioning whether a patient needs a colon examination today—it’s routine, like a chest X-ray.
"When you’re dealing with something that’s in its infancy, like CT scanning is today, it’s difficult to predict how it will be viewed in retrospect,” he said.
What do you see in the future for CT scanning?
Dr. Sheedy said he thinks that a plateau of technology may now be being reached in conventional CT technology with the development of recent two- and three-second scanners and that any great advances in the CT area beyond this may be in the nature of the Dynamic Spatial Reconstructor, (the new X-ray diagnostic system being developed here that has the capability of stop-action visualization of moving organs.)
Dr. Forbes mentioned that one point in CT scanning’s favor for the future is that it can be done on an outpatient basis. “This is very important,” he said, “because I think the thrust of medical care and diagnosis in the future is going to be on taking care of more people on an ambulatory basis.”
Dr. Forbes added that future uses of CT scanners and other similar high-technology diagnostic equipment may well be determined by social and economic criteria rather than by technical and scientific criteria.
As CT radiologists, do you share a sense of pride in the awarding of the Nobel Prize to the inventors of this new technology?
Said Dr. Sheedy, “One thing you could hope for is that the awarding of the Nobel Prize may decrease the volume of criticism that has been laid on CT as ‘a toy.'
“It is not a toy,” he said with some heat, “it is a serious, clinically viable tool. It is certainly not a toy to the patient when a CT examination has just revealed a small tumor, previously unsuspected, which was responsible for his or her symptoms.
“Perhaps the awarding of the Nobel Prize will add credibility to the CT method and help it become accepted by the medical profession, the government, and by the public as a valuable and necessary diagnostic instrument,” he said.