Simultaneous Positron Emission Tomography (PET) – Magnetic Resonance (MR) combines the excellent sensitivity of PET with the versatility of MRI. PET provides metabolic information, and the range of different PET tracers offers the possibility to image different molecular targets. MRI yields high-resolution anatomical images with different contrasts as well as functional information about blood flow and microscopic tissue structure. This makes simultaneous PET-MR a highly promising imaging technique, especially for cancer diagnosis and cancer management, but also for cardiology.

Attenuation correction (AC) maps provide information about the attenuation of the PET signal due to different tissue types with different densities (e.g. bone mass has a high density and strong attenuation, lung tissue has a low density and weak attenuation). AC maps are required to compensate for this effect and allow for quantitative PET reconstructions.

For simultaneous PET-MR acquisitions in the thorax or abdomen these AC maps are obtained in a single breathhold. This can lead to misregistration errors between breathhold AC and free-breathing PET data. We are working on methods to obtain accurate AC information during free-breathing and to yield additional respiratory motion fields which can be utilised in motion-compensated MR and PET reconstructions to improve image quality and quantification accuracy (Link to motion compensation project).

The combination of PET and MR allows for advanced motion-compensated image reconstruction approaches. Physiological motion information obtained with one of the two modalities can also be utilised for the image reconstruction of the other modality. Furthermore, the two data streams can be combined to obtain motion information with improved accuracy.

In cardiac applications PET-MR allows for example for the correction of both respiratory and cardiac motion information leading to an improvement of more than 30 % in PET tracer quantification.

Further information on motion compensation

A wide range of complementary diagnostic information can be obtained with PET-MR within one scan. PET-MR holds the promise to become an important tool especially for cancer diagnostics and modern cancer management, but also for cardiac applications.

The PTB is part of a consortium led by Charité-Universitätsmedizin Berlin, which has purchased and installed the first simultaneous whole-body PET-MR scanner in Berlin. We are collaborating closely with Dr. Winfried Brenner from the Department of Nuclear Medicine and Dr. Marcus Makowski from the Department of Radiology at Charité Berlin to develop novel PET-MR techniques which will have a direct impact on patient care.