Program director highlights CT's past and future course

Given its history, the point of diminishing returns in innovation may be years away for CT technology and applications

This article was adapted from Dr. Gary Glazer's opening presentation as course director at the Stanford Multidetector-Row CT symposium in San Francisco in June. Glazer is chair of radiology at Stanford University School of Medicine.

In recent decades, speed gains in CT have been stunning. Minimum scan time with the current generation of 64-slice scanners is 3000 times faster than when the technology was implemented in 1972. The amount of data captured per scan has increased on an even greater scale.

On top of speed gains, the number of slices on scanners has increased dramatically, while slice thickness has diminished substantially. The net effect of all this has been the development of a much faster modality and a truly revolutionary tool.

Sir David Humphrey said, "Nothing tends so much to the advancement of knowledge as the application of a new instrument. The native intellectual powers of men are not so much the causes of the different successes of their labors as the peculiar nature of the means and artificial resources in their possession."

Humphrey's statement holds true in medicine.

Speed gains combined with higher spatial resolution have given birth to very robust images, and specific applications have benefited immensely from the introduction of powerful tools. In the vascular system, for example, a CT scan taken in several seconds can clearly depict all the major named vessels of the human body.

Despite striking gains, more speed is required for visualization of small, rapidly moving structures, such as the coronary arteries. There would be a huge public health benefit if we were able to image coronary arteries noninvasively in a few seconds. New technology presented at the Stanford symposium demonstrates better temporal resolution for greater speed gains.

In addition to CT methods that increase temporal resolution, developments will also increase spatial resolution and coverage. Dr. Norbert Pelc of Stanford University has developed a concept for an inverse geometry CT scanner that should offer higher spatial resolution and wider coverage. We hope to see scanners based on novel geometries move from the research lab to the clinic in the near future.

Improvements in temporal and spatial resolution will aid visualization in high-contrast situations, such as in the lung and bones. Due to limitations inherent in the physics of CT, however, contrast resolution has not improved in decades, and the modality is still limited in low-contrast situations. If limited to intrinsic tissue composition differences, CT cannot advance in the evaluation of soft-tissue abnormalities, such as depicting lesions in the brain and liver. Efforts need to be directed toward developing targeted contrast agents to increase contrast of otherwise low-contrast lesions.

Following dramatic developments in recent decades, some question whether continued progress in technical aspects of CT will lead to quantum leaps in diagnosis, or, conversely, whether we are reaching a point of diminishing returns.

It is my belief that even if there were no further technical progress in CT, it is highly likely that we would find novel ways of using CT to significantly improve diagnosis and health. Consider that it took 45 years before mammography was proven to save lives.

Based on the amount of innovation and nearly revolutionary changes in CT we have seen since implementation in the 1970s, it seems to me that we have a long way to go before we even think about reaching the point of diminishing returns.

Ms. Hayes is feature editor of Diagnostic Imaging.