Logo PTB
Gateway for school

Quantitative magnetic resonance imaging

Fast and accurate procedure for improved diagnosis of cardiac diseases

PTBnews 1.2019
07.03.2019
Especially interesting for

medical research

manufacturers of medical imaging devices

cardiology

Magnetic resonance imaging (MRI) is an important imaging procedure in cardiology. To date, only qualitative imaging has been possible with MRI, since the measuring time is limited due to heart movements and breathing. A new image reconstruction procedure has now been developed at PTB. This method quantifies the biophysical parameters of the cardiac muscle with high spatial resolution and thus enables an objective diagnosis.

a: T1 map of the heart of a healthy volunteer. b: Evaluation of the accuracy of the T1 values in a phantom for different heart rates (bpm). The accuracy of the T1 values (red) is independent of the heartbeat, whereas MOLLI – the most widely used T1 imaging method – underestimates T1 values at high heart rates (blue).

In conventional diagnosis, the images recorded are interpreted visually, so that the diagnosis depends on the doctor examining the image and on external influence quantities such as the manufacturer of the device and its place of installation. Quantitative imaging is a new field in biomedical research and clinical diagnostics. It consists in acquiring biophysical parameters of the tissue. This leads to more objective diagnoses and improved comparability between images. Developing these parameters allows the course of the therapy to be appraised.

In MRI, the tissue-specific relaxation time T1 is used as a quantitative marker. T1 describes the time-dependent behavior of the nuclear spins after they have been excited by means of a magnetic AC field. Cardiac T1 imaging has great potential for clinical application since it allows pathologies of the heart to be diagnosed without radiation and without contrast agents. However, the major challenge is the heart's movement due to breathing and the heart beating, which limits the measuring time and, thus, the spatial resolution of the images. Furthermore, systematic measurement errors may occur due to simplified signal models.

A novel measurement procedure has now been developed at PTB: it provides T1 maps of the heart with high spatial resolution in only 16 seconds. For this purpose, an iterative, model-based reconstruction procedure has been developed that can be used to determine T1 values from very few measurement values. This has allowed the spatial resolution of the T1 maps to be increased from (1.4nbsp;×nbsp;2.1) mm2 to (1.3 × 1.3) mm2 without changing the measuring time. Furthermore, the measurement provides information on the contraction of the heart during a cardiac cycle. This makes another important clinical parameter on the heart function available without requiring any additional measurement. The patient is thus examined more efficiently. The procedure was evaluated both in a T1 phantom and in healthy volunteers. In contrast to methods that are already available, the accuracy of the T1 values is independent of the heart rate and, with a difference of -0.3 %nbsp;±nbsp;2.5nbsp;%, it is in excellent agreement with the result of a fourhour reference measurement. The procedure is currently being tested on patients within the scope of a cooperation project with the Charité hospital in Berlin.

Contact

Kirsten Becker
Department 8.1
Biomedical Magnetic Resonance
Phone: +49 30 3481-7463
Opens window for sending emailkirsten.becker(at)ptb.de

Scientific publication

K. M. Becker, J. Schulz‐Menger, T. Schaeffter, C. Kolbitsch: Simultaneous high‐resolution cardiac T1 mapping and cine imaging using model‐based iterative image reconstruction. Magn. Reson. Med., 81(2), 1080–1091 (2019)