Combined PET/MRI: from Status Quo to Status Go. Summary Report of the Fifth International Workshop on PET/MR Imaging; February 15-19, 2016; Tübingen, Germany

This article provides a collaborative perspective of the discussions and conclusions from the fifth international workshop of combined positron emission tomorgraphy (PET)/magnetic resonance imaging (MRI) that was held in Tübingen, Germany, from February 15 to 19, 2016. Specifically, we summarise the second part of the workshop made up of invited presentations from active researchers in the field of PET/MRI and associated fields augmented by round table discussions and dialogue boards with specific topics. This year, this included practical advice as to possible approaches to moving PET/MRI into clinical routine, the use of PET/MRI in brain receptor imaging, in assessing cardiovascular diseases, cancer, infection, and inflammatory diseases. To address perceived challenges still remaining to innovatively integrate PET and MRI system technologies, a dedicated round table session brought together key representatives from industry and academia who were engaged with either the conceptualisation or early adoption of hybrid PET/MRI systems. Discussions during the workshop highlighted that emerging unique applications of PET/MRI such as the ability to provide multi-parametric quantitative and visual information which will enable not only overall disease detection but also disease characterisation would eventually be regarded as compelling arguments for the adoption of PET/MR. However, as indicated by previous workshops, evidence in favour of this observation is only growing slowly, mainly due to the ongoing inability to pool data cohorts from independent trials as well as different systems and sites. The participants emphasised that moving from status quo to status go entails the need to adopt standardised imaging procedures and the readiness to act together prospectively across multiple PET/MRI sites and vendors.

Control of threading dislocations in lattice-mismatched heteroepitaxy

It is generally observed that strain relaxation, which occurs by misfit dislocation formation, in lattice-mismatched heteroepitaxial layers is accompanied by the formation of threading dislocations. However, our group and others have observed that strain-relaxed epitaxial layers of In1−xGaxAs on GaAs substrates can be grown without the formation of threading dislocations in the epitaxial layer. We have been able to grow strain-relaxed layers up to 13% In concentration without observable densities of threading dislocations in the epilayer but do observe a large number of dislocations pushed into the GaAs substrate. The ability to grow strain-relaxed, lattice-mismatched heteroepitaxial layers has important practical applications. We have succeeded in growing dislocation-free layers of ZnSe on appropriately lattice-matched layers of In1−xGaxAs.