PET/MRI

Efforts have long been made to combine the PET technique with MRI instead of with CT. The advantage of this would be that as opposed to CT, the soft tissue contrast available with MRI is excellent, thus it would be more useful as far as tumour diagnosis is concerned. The basic difficulty in coupling the two modalities is that the PMTs used in PET do not operate above a certain magnetic field (~100 G) and the magnetic field occurring because of the presence of the MRI exceeds this value. However, the coupling of the two modalities can be performed by replacing the PMTs (see Chapter 2.3.2.3. Semiconductor Photodetectors). PET/MRI devices already exist, even if they are not used in clinical practice. A PET/MRI image:

Figure 1 PET-MRI image (from Siemens manufacturer page)