The first revolutionary technology that showed pictures from the inner life of a human being was already developed in 1895 by Wilhelm Conrad Röntgen. For the first time ever, his x-rays made photos of organs and bones possible. Since then of course a lot has happened. There is no end in sight for the development of imaging procedures, because the declared goal of many scientists is to take a “very intimate” closer look.
The latest technology that is being researched right now is ranging in the area of nanometer structures. A special nano computed tomography method – developed by a research team from the Technical University Munich, the Paul Scherrer Institute and the ETH Zürich – now for the first time enables examinations of even the smallest of bone structures. Franz Pfeiffer, leader of the research team, explains in a published press report: “With our newly developed Nano-CT-method it is now possible to display the structural- and density changes of bones in high resolution and in 3D. With it you can research the structural changes underlying osteoporosis on the nano scale and develop better treatment approaches.“
This procedure is also intended to be used in other, non-medical areas such as the development of new materials for example.
Computed tomography scanners for the first time enable three-dimensional insights into the inner workings of human beings by means of taking x-ray photographs from different directions. This is helpful for the diagnosis of a complicated bone fracture for instance. But not all structures can be equally well pictured with CT. Images of the heart for example are quickly defective when using older instruments, because the heartbeat – that is the motion of the heart – causes motion blur. The only way to achieve a clear image thus far was to ask the patient to hold his/her breath for several seconds. And some patients with severe heart arrhythmia could not be scanned from the start. In the end, the solution was to have the CT scan only last a fraction of seconds. The motion blur was thereby significantly reduced.
Another procedure, the Positron-Emissions-Tomography (PET), pursues a different approach. Unlike with CT, with this method metabolic processes can be visualized. For this purpose, radioactively marked substances are injected into the bloodstream (radiopharmaceuticals) that display biochemical metabolic processes and features. Newer equipment partly combines both methods – so-called PET-CT-scanners that through combining both technologies are able to deliver comprehensive patient data for diagnostics. Yet the desire to further enhance the image fidelity for better diagnostic investigation still remains.
The invisible is made visible – Molecular imaging
One example for this is the Collaborative Research Center (SFB) 656 at the University of Münster, which researches the area of ”Molecular Cardiovascular Imaging“. The goal of molecular imaging in the area of cardiovascular diseases is, according to Professor Michael Schäfers, scientific coordinator of the SFB 656 at the European Institute for Molecular Imaging, “to be able to provide an image-guided definition of the individual risk for instance for a future heart attack in an arteriosclerosis patient.“ The imaging of a stenosis in vessels for arteriosclerosis is also possible with CT scanners that are already on the market, but these only display the stenosis itself. However, they cannot visualize an inflammation of the vascular walls – and this is precisely what scientists would like to illustrate. Specifically the inflammation of these vessels is the actual cause of acute vascular obliteration and the subsequent heart attack. This is also why the determination of inflammatory responses is supposed to be possible in the future.
PET-CT-scan: The scan of a healthy heart. The tracer shows an active metabolism (red); © SFB 656 MoBil
During a heart attack myocardial tissue dies off. Scar tissue is formed, where no metabolism can be detected anymore (arrow down to the right: heart attack in the apex of the heart); © SFB 656 MoBil
For this purpose, specific tracers are developed at the Institute, radioactive, fluorescent or otherwise marked drugs that attach themselves to certain molecules and thus display inflammation – and that can be made visible with advanced technical methods. Professor Schäfers: “We need a procedure like PET for molecular imaging to be able to show inflammation. Therefore we inject radiopharmaceuticals in the arm vein. For the procedure itself we use a PET-CT-scanner which we have to optimize due to our special requirements. Because particularly in the “cardiovascular“ area we have a specific problem – we monitor structures that move and in part are very small – for example coronary vessels. In terms of measuring, this presents a big challenge. This is why the Collaborative Research Center forms interdisciplinary task forces that work on identifying motion on the image and then take them back out again – virtually freezing the images.“
Early results of the developed software look promising. And although cardiac scientists specialize in cardiovascular diseases, they hope to be able to reach other clinical fields with their procedures, like for example oncology where several of the used devices originally “originate“.
“We specialize in cardiovascular questions, but in part our developments can also be valuable to other fields“, says Schäfers. An important metabolic process both in heart attacks as well as tumors is for instance apoptosis (programmed cell death). One enzyme behind this metabolic process is called Caspase and serves as a target. The physician continues: “Although with cancer the exact opposite is happening – cell growth instead of apoptosis – the goal of cancer treatment however is to render the tumor apoptotic, and so our procedures can be applied for treatment checkups. Like for example after a chemotherapy cycle to be able to determine, whether apoptosis was established or whether the tumor is resistant to treatment. Thus the procedure on the one hand can serve treatment checkups and on the other hand for creating treatment plans, for example in the case of heart attacks.“
When the new procedures will ultimately arrive in day-to-day clinical operations, is not yet foreseeable. This depends less on the development of equipment – in the future PET-MR-scanners are also supposed to get tested – but rather on a possible breakthrough in the development of a specific radiotracer.
(Translated by Elena O'Meara)