CT of the lungs: new method makes structure and function visible at the same time

Using innovative photon-counting computed tomography, a team of radiologists at MHH has developed a new technique for imaging the lungs.

[Translate to Englisch:] Professor Shin (links) und Dr. Scharm begutachten anhand der CT-Aufnahmen die Struktur (grau), die Belüftung (blau) und die Durchblutung (rot) einer Lunge; Copyright: Heike Steinlandt/MHH.

When new techniques are developed in radiology, there are usually two things at stake: the images should be as informative as possible, and the radiation exposure for patients should be as low as possible. A team from the Institute of Diagnostic and Interventional Radiology at the Hannover Medical School (MHH) developed such a procedure together with Dutch colleagues. The new technique brings progress in computed tomography (CT) of the lung: it is possible to visualise the structure, function and blood flow of the organ simultaneously in one examination. The procedure has now been patented. The researchers published their scientific work in the journal Radiology. 

All information in one step

"Computed tomography is the imaging technique of choice for analysing lung diseases," says Professor Dr Hoen-oh Shin, senior physician at the Department of Diagnostic and Interventional Radiology and senior author of the study. "However, if you want to include not only the structure of the lungs but also their ventilation and blood flow in the analysis, additional examinations have to be done so far." For patients, this also means additional radiation exposure. The newly developed CT protocol of Professor Shin's team, on the other hand, provides all the information in just one step. To do this, the experts use photon-counting computed tomography, which enables high image quality with a low radiation dose. In the study, the researchers used the new method on a total of 197 people who needed to be CT scanned due to various lung dysfunctions. "The scan consists of two sections, an inhalation scan, for which contrast is also administered, and an exhalation scan after a delay of 5 minutes," explains Dr Sarah Scharm, lead author of the study. "In 166 people, we were able to capture all CT-derived values. This equates to an 85 per cent success rate."

New diagnostic possibilities

The CT procedure gives radiologists images of the structure, ventilation and blood flow in the lungs. A high regional assignment of function and structure is possible to within one to two millimetres. "The quality of the images is clearly superior to that of a standard CT," notes Professor Dr Shin. With the new imaging options, there are better diagnostic possibilities, for example in the early detection of diseases. "In the course of a lung disease, there are often first functional restrictions and only later structural changes," explains the radiologist. One example is pulmonary fibrosis. The disease begins with disturbances in ventilation. The examiners can already recognise these disturbances on the images before the structural changes, i.e. the scarring, become visible. "This allows us to pinpoint the disease and the areas where it is active at a very early stage. These are valuable insights for treatment," explains Professor Shin.

Helpful before and after surgery

There are other promising applications of the new CT protocol. Before surgery, for example, it can be helpful for patients with chronic thromboembolic pulmonary hypertension (CTEPH). CTEPH is caused by blood clots that become lodged in the pulmonary circulation. "With the help of the images, it is possible to identify preoperatively exactly those areas that are affected by circulatory disorders and need to be treated surgically," explains Dr Scharm. The new procedure is also proving useful after operations. "As part of a complementary study, we are currently investigating how well thrombectomies, i.e. the removal of blood clots, have gone for the patients' lung function in order to check the success of the therapy," reports Dr Scharm. She emphasises that the technique is generally useful in diseases with known or unknown impairment of lung function.

Still much potential

This novel procedure benefits considerably from photon-counting computed tomography. With funding from the state of Lower Saxony, Hannover Medical School was able to put one of the first 20 CT units of this kind in the world into operation. Professor Dr. Frank Wacker, Director of the Institute for Diagnostic and Interventional Radiology, points to the synergy between groundbreaking innovation from industry and the expertise of the researching doctors at his institute. This innovation benefits the patients in Lower Saxony, who also benefit from the lower radiation exposure of modern CT. The research teams in radiology are working intensively to identify further potential applications, for example in cancer medicine.

Text: Tina Götting