Cardiac Imaging: Methods of the Future

The latest achievements in radiology are revolutionizing gentle, non-invasive heart diagnostics. Multi-slice computer tomography (MSCT) can spare patients from invasive cardiac catheter examinations and for example, allow physicians to assess the risk of coronary based on the amount of calcification in coronary vessels. Blood flow rates in the heart muscle can be accurately evaluated today in just 30 seconds using magnetic resonance tomography. Two X-ray tubes rotating parallel to each other (dual source CT) can now also be used to render precise images of fast or irregularly beating hearts. Combining the various imaging methods is a promising approach for the future, as initial results have already shown.

Vienna, Friday, 9 March 2007 – Cardiovascular diseases are the most common cause of death in Europe. The fact that many patients with coronary heart disease are unaware of their malady worsens their prognosis. “That is why radiological examination methods are becoming increasingly important for the early detection of heart diseases,” noted Professor Dr. Claus D. Claussen (University Clinic for Radiology, Tübingen) at the kick-off press conference of the European Congress of Radiology (ECR) 2007, an event held from March 9 to 13, 2007, at Austria Center Vienna and attended by 16,000 participants from 92 countries.

There has been a rapid rise worldwide in the use of multi-slice computer tomography (MSCT) on the heart in recent years. Professor Clausen: “Today’s equipment has 64 detector lines and delivers much better temporal and spatial resolution than the initial generations of equipment did and thus more precise imaging of the heart. Under certain circumstances, cardiac CT allows coronary heart disease to be diagnosed so that preventive steps can be taken on time.”

That is an advantage, especially for patients with risk factors such as obesity or diabetes, unfavorable cholesterol levels or high blood pressure. If a patient has one or more of these factors or atypical chest pain, CT imaging of the coronary vessels can determine whether or not an invasive cardiac catheter examination is necessary. Professor Claussen:  “This is all the more significant because a relevant percentage of cardiac catheter examinations are for strictly diagnostic purposes.”

MSCT also indicates early changes in vascular walls or possible constrictions of the diameter of the vessel. CT can be used for exclusion diagnostics in patients with complaints of unknown origin and only a small probability of significant coronary stenosis. In the case of chest pains and cardiac irregularities of unknown origin, certain cardiac diseases can be excluded in a CT examination without imposing a strain on the patient.

Determining the Risk of Cardiac Infarction
Deposits of calcium in the coronary vessels (plaque) is of particular significance for prevention. Professor Claussen: “With a cardiac CT you can estimate the risk of later cardiac events like a coronary based on the amount of calcium in the coronary vessels. A patient with a large amount of calcium usually has a high risk of cardiac infarction. The prognostic meaning of results like these is definitely significant and has been demonstrated for individual patients.”

Future Prospects of Dual Source CT: Quicker than a Heartbeat
With the introduction of a fast-rotating dual-tube system, examinations in patients with a fast heart rate or an irregularly beating heart can now be conducted even faster and more precisely than with the modern 64-liner. “Unlike conventional single-tube MSCT, the dual source CT has two X-ray sources offset by 90 degrees with a detector system opposite each. The ultra-high speed of rotation delivers an extremely high degree of temporal resolution, which has a lot of advantages especially for non-invasive imaging of the heart,” Professor Claussen explained. “This procedure is not yet applied routinely, but the use of dual X-ray tubes is expected in future to open up entirely new examination possibilities.”

For instance, scans could be conducted with each individual tube set at a different level of energy. That would generate two different sets of data with different measured values for a bodily organ and allow morbid changes in an organ to be imaged more precisely.

New Standards in Magnetic Resonance Tomography (MRT)
The possibilities for quick MRT imaging have also improved substantially. This has been made possible through specially optimized examination conditions on high-field equipment that operates with a field strength of 3 Tesla. Professor Claussen: “Even slight changes in the heart muscle can be verified with high local resolution by checking the heart function in fast moving images of the heart beat. The blood flow rates in the heart muscle can be evaluated with great accuracy today using MRT, compared with earlier known methods such as positron emission tomography and scintigraphy. Five years ago, it took about 5 minutes to make a quantitative evaluation of the heart function. Today we can do it in 30 seconds.”

Lastly, a contrasting medium and special images can be used to check whether scarring exists from cardiac infarction and if so, its extent.

A Look into the Future: Combining Imaging Methods for Optimum Diagnosis
Combining various imaging procedures such as PET and computer tomography or PET and magnetic resonance tomography opens up whole new perspectives. Professor Claussen: “Although clinical use on patients is still in the realm of dreams for the future, initial results already show revolutionary images that contain the widest variety of functional and anatomical information and that enable us to obtain new kinds of insights into cardiac diseases.”

Contact: claus.claussen@med.uni-tuebingen.de

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