Imaging predictions

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As Radiologist-in-Chief at Massachusetts General Hospital, one of the world's most renowned academic medical centres, Dr. James Thrall helps oversee the movement of major innovations in medical technology from concept to practice. Dr. Thrall will give the keynote address at the Imaging & Diagnostics Congress as part of Arab Health 2008. Here, he goes back to basics in his ever-changing field, and charts the course of radiology as it moves forward in the coming years.

How can we take a step back from the modalities we see in practice and learn how to think about the concept of imaging?

Every medical imaging procedure involves the interaction of some kind of energy with the tissues of the body. So depending on which tissue we want to examine, we may choose one energy source or another, such as X-ray to look for a broken bone or ultrasound to look at a foetus inside the womb.

Before we move into the future of radiology, can you help us understand where we are now, in terms of present capabilities and the clear opportunities for the future?

The history of radiology has been at the level of organs and organ systems-one of the first things that X-rays were used for was to diagnose broken bones. In the lung, we use X-rays and CAT scans to diagnose tumours and pneumonia, and in fact we use X-rays in almost every part of the body to diagnose tumours and infectious disease.

The future is going to take us to smaller dimensions. Just as there are many areas of science where people are very excited about nanotechnology, we are very excited in imaging with the ability to now image not just at the level of the whole organ, but at the level of molecules and cells. The wonderful new term ‘molecular imaging' is used to describe this trend.

The other thing that we've been able to do is take advantage of the change in the function of an organ in order to watch organs process signals from the outside world. This is most important in the brain, where we are able to actually watch the brain think by observing changes in the energy metabolism of the brain, and changes in the blood flow to different parts of the brain as it processes a thought. It's really quite astonishing because there is a tight coupling between energy utilisation, blood flow, and the amount of work that the brain is doing. So if we expose a subject to a visual stimulus, the parts of the brain that process the signals in the eyes will light up on the scan. Or if we play a musical note, a different part of the brain that's involved in auditory processing lights up.

Molecular imaging is a new term but maybe not such a new concept, right? There are things we have been using for years which can be considered molecular imaging.

Yes. Molecular imaging got its start 50 years ago or more in nuclear medicine. But we didn't conceptualize what we were doing as molecular imaging. Today we would call what we did 50 years ago molecular imaging. In the meantime, the number of different applications has simply skyrocketed. So it's no longer just nuclear medicine-it's now ultrasound, MRI, and even visible light sources or near-infrared light sources used as the energy for molecular imaging.

A lot of focus in imaging is on the machines, but the science is a complicated mix of physics, engineering, chemistry/biology, and now IT. What is the process by which advances in imaging science become part of imaging practice?

It is a complex process. To shorten the story, think of some other thing that we use in every day life, like a television set, and consider how it has been improved over the years: the advent of high-definition recording, flat panel displays, and other innovations. The same thing is happening in imaging, where every component of everything we do is simply getting better, allowing us to see finer detail with higher resolution. We can capture changes in organ function more rapidly, and we can use pharmaceuticals as enhancement agents to light up certain parts of the body that are involved in a disease process.

What is the interplay between academic medical centres and industry that brings these sorts of advances into practical application?

Typically, industry does the engineering and physics and comes to us and we do what's called translational research with every new product to demonstrate its usefulness clinically. In fact, this is required by the U.S. Food & Drug Administration. So there's necessary partnership between industry and the academic world because the only place you can do that kind of clinical research is in a hospital. You cannot do that in the manufacturer's research laboratory.

So that would probably go hand in hand with training and education. Students come up through academic medical centres where new technologies are being tested.

Absolutely. In fact, people train in academic centres where all the cutting-edge devices and concepts are being tested. Often when they leave those centres, for example to go into private practice, it's like stepping back in time, sometimes to their surprise.

Today magnetic resonance imaging (MRI) is thought of mainly as a modality for diagnosing neurological and musculoskeletal problems. Where do you see the use of MRI expanding?

MRI is now being used in cancer diagnosis. For example, in prostate cancer it's possible to obtain highly detailed spectroscopy images to distinguish benign from malignant prostate tissue. This will be extremely valuable.

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