Interview - Radiology


Scanning the road ahead

Dr James Thrall, considered by many to be the world’s pre-eminent authority on radiology in medicine, presented the keynote lecture at the diagnostic imaging symposium at Arab Health 2008. Following the presentation Middle East Health editor Callan Emery spoke with the esteemed radiologist.

Dr James Thrall is radiologist-inchief at Massachusetts General Hospital (MGH) in Boston. He also serves as the Juan M. Taveras Professor of Radiology at Harvard Medical School in Boston. He chairs the executive committee of the Harvard Departments of Radiology and is a member of the RSNA Research & Education Foundation Board of Trustees. He was awarded the RSNA gold medal in 2007 for his “invaluable visionary insight and dedication which have helped chart a course for the specialty”. Dr James Thrall, radiologist-in-chief, Massachusetts General Hospital

Dr James Thrall knows the future of radiology. Well maybe not exactly, but he can hazard a very good guess at where it’s going. As radiologist-in-chief at Massachusetts General Hospital (MGH) in Boston, United States, and holding several distinguished positions on leading radiological boards, committees and foundations, he is widely regarded as being at the forefront of the field – the course of which over the years he has had significant influence in charting.

So where does he think radiology is going? In essence he believes that all of clinical medicine will begin to be structured around radiology as it becomes more specialised and increasingly provides physicians “spectacular, accurate and efficient diagnoses”. And looking at current trends, he says, the quality, accuracy and speed of imaging can only get better and better.

Dr Thrall was in Dubai in January to present the keynote lecture at the Arab Health diagnostic imaging symposium. These trends, which “are going to shape medical imaging in the future”, formed the basis of his talk. He looked at these trends according to a number of themes.

Dr Thrall began by highlighting the fact that “continued advances in physics, engineering, electronics and computer processing are resulting in unprecedented performance on even wellestablished imaging methods”. As an example he noted that we have been imaging 1.5 Tesla (T) MRI for the past 25 years, but have now recognised that imaging at 3T is much more sensitive for many applications. “This is giving us better diagnostic capability.” Dr Thrall added that on the research side 7T MRI is taking imaging to a completely new level. He noted, for example, that with 7T MRI neuroradiologists are able to resolve the “islands of the endo rhinal cortex” of the brain which had not been possible previously. Diagnosing abnormalities in these structures is a breakthrough for Alzheimer’s patients, as it is these structures that become abnormal first at the onset of Alzheimer’s disease.

“So we have gone from 1.5 to 3 to 7 Tesla, which is indicative of how the power of physics and engineering is propelling radiology forward,” Dr Thrall said.

Flat panel CT

He noted that this advance is also evident in CT. He said his radiology department at MGH has been working with a “flat panel’ detector from Siemens for the past few years and that it is able to provide much higher resolution images than the multi-detector CT (MDCT), the resolution of which is limited by the width of each detector.

In an exclusive conversation with Middle East Health following the symposium Dr Thrall explained: “In multidetector imaging, the width of the detector determines the resolution – so if you have 0.5 mm detector you can’t do any better than 0.5 mm and you are likely to do not quite that well. Whereas with flat-panel CT it is just a continuous surface like a monitor or TV and the resolution is determined by the sampling frequency. Like the difference between standard TV and Hi-Definition TV – flat panel offers hi-definition imaging because there is no physical limit to the imaging detector width.

However, he added that flat panel CT did not appear to be on the main development pathway as data acquisition is slower. The emphasis at the moment, he said, is on speed of acquisition to capture, for example, a volume image of the entire heart in a single beat. He said this was not clear if the flat panel CT, compared to MDCT, would in effect reduce radiation dose, an important issue in CT.

Discussing the issue of radiation dose he remarked that unfortunately many radiologists are using the same protocols for multi-detector scanners as they did for single detector scanners – resulting in higher radiation than is necessary. “So the radiology world is now looking again at their protocols.”

The second theme of his presentation dealt with the trend of increasingly sophisticated digital image processing which “permits the extraction of more medical value from image data”. “With improved resolution of CT, MR and ultrasound and with the massive computing capability that is available it is possible to project images in 3D and look at maximum intensity images,” he said.

“Such powerful digital image processing is allowing us to extract medical value beyond anything we could have imagined just 10 or 15 years ago.” Dr Thrall used for example an image from a coronary angiogram to show a vascular stenosis and compared this with an image of the same stenosis imaged with a multidetector CT – the difference being that the CT image took 30 seconds to acquire as opposed to the considerably longer and invasive procedure of the arterial catheterisation.

Human resource

In conversation I asked Dr Thrall if he thought that the rapid advance in imaging technology was running ahead of our ability to interpret the increasingly detailed images. Or in other words, are we matching the human resource to the sophistication of the technology? And what can be done to resolve this situation?

He replied that the technical sophistication is challenging the human resource “as the days for the general radiologist – a person who can interpret a scan from any part of the body with any kind of imaging system – are rapidly passing”.

“On the other hand a lot of patients are being taken care of in small towns, in smaller institutions, where it is simply impractical to have 20 to 30 radiologists each of whom have a different sub-specialty. The answer is in telecommunications – telemedicine. What we are seeing more and more are small institutions establishing telecommunications links with larger institutions and if they have a case that requires a higher level of sub-specialty they will send that case to that institution.

“This is a pattern I think we will see increasingly in the Middle East – for the same reasons,” he added. In Saudi, for example, large sophisticated medical institutions like King Faisal Specialist Hospital and Research Center in Riyadh can link up electronically with smaller centres in the country.

He said that radiology is becoming increasingly specialised.

“To put it in perspective we train about 10 students a year in medical school to become general radiologists, however, we train about 35-40 people each year who have decided to specialise in one application or another – such as neuroradiology or cardiac radiology. About three-quarters of those who graduate from general radiology go on to fellow-ship – that is, train in a sub-specialty. This figure has definitely increased over the years.”

Molecular imaging

The third theme of his presentation looked at how molecular imaging is being increasingly incorporated into clinical practice.

Dr Thrall explained that molecular imaging is in fact a combination of three disciplines – biology, to identify the target molecule; chemistry, to develop a reporter label so that the molecule can be identified; and physics, to capture the image.

He referred to the recently developed PET-CT scanner which enables radiographers to fuse metabolic information (from the PET scan) with high-resolution anatomic information from the CT scan. As an example, he noted that physicians had not noticed a metastatic lesion in a patient with melanoma when using only the CT scan, but once combined with PET imaging the site of the lesion became clear.

“The power of molecular imaging lies in the molecular imaging agents which will go anywhere in the body to find the disease. Add to this the ability to fuse this information with anatomic information and we have a very powerful tool to localise disease in the body.”

Functional imaging

Functional imaging (fMRI and fPET) – the fourth theme of Dr Thrall’s presentation – is continuing to expand along with increasing sophistication in spatial resolution, temporal resolution and image processing.

He pointed out that functional imaging is now so sensitive that if you just wiggle your fingers or waggle your tongue the change in oxygen level associated with that in the brain is detectable by either fMRI of fPET.

Before a brain cancer patient goes to the operating theatre this technology enables the neurosurgeon to systematically study the sensory and motor areas around a tumour and know exactly where these areas are before and during surgery.

Dr Thrall spoke briefly about advanced fMRI, specifically diffusion spectrum tractography, which shows up the nerve fibre tracts in the brain. “We can actually determine which fibre tracts link up one part of the brain with another.” He said this “very spectacular application of functional imaging” is also proving incredibly valuable in guiding neurosurgery.

Biomarkers

One aspect of radiological imaging which is set to dramatically transform clinical research – making it faster and less costly – involves the use of imaging biomarkers.

In discussion with Middle East Health, Dr Thrall explained: “It is something that has been practised for a long while, but like many other things it is now in its exponential growth phase.

“To put it in perspective, there are something like 12,000 to 14,000 pharmaceuticals currently in development worldwide. There are somewhere in the region of 2,500 to 3,000 cancer drugs in development. Focussing just on cancer drugs, if you have to wait five years to check survival rates we will never develop a drug. And so it makes a lot of sense to use biomarkers.

“Imaging biomarkers are just a way to determine what the effect of the drug is on the tumour. Did the tumour shrink? It’s not a perfect linkage, but intuitively you can say that if the tumour doesn’t shrink it is unlikely the drug is working. If the tumour does shrink you can infer that the drug works.

“You can measure this in a matter of weeks instead of years.”

He pointed out another benefit, saying that in survival studies for a specific cancer drug, for example, if you know the size of each person’s tumour and whether it is shrinking or expanding, you may be able carry out the study without a patient control group.

“In this way the trial will go a lot faster. They are less expensive and it becomes practical to evaluate more drugs.”

Image-guided therapy

Dr Thrall noted in his presentation that image-guided therapy has advanced to a scale that could never have been imagined.

He said that although interventional radiology has been practised for a long time, it is with the relatively recent integration of more sophisticated imaging technology that the specialty has advanced so rapidly.

“Much of clinical medicine – actually all of clinical medicine – is being restructured around diagnostic imaging,” Dr Thrall emphasised.

“Twenty to thirty years ago we were considered an ancillary specialty of medicine. Now we are a necessary specialty of medicine because of the spectacular, accurate and efficient diagnoses we can make.

“And all of this is going to get better because of the trends that are apparent today.”

 Date of upload: 3rd April 2008