The interaction between ionizing radiation and materials composed of high Z-number elements could be applied to enhance radiotherapy. In this work, we fabricated an ionizing radiation-sensitive nanoplatform by grafting chlorin e6 (Ce6) onto the surface of ultrasmall gold nanoparticles (Au NPs), aiming to enhance the radiation effects induced by different radiation sources. Poly(ethylene glycol) (PEG) was applied as the shape-controlling agent during the synthesis of Au nanoparticles. The as-prepared Au NPs show excellent monodispersity, with an average hydrodynamic diameter of around 5 nm. U87 and HeLa cell lines were utilized to evaluate the biological properties of the as-prepared Ce6–Au NPs. The Cell Counting Kit-8 (CCK-8) results reveal that the Ce6–Au NPs conjugate can significantly affect the growth of U87 cells under X-ray and 68Ga exposure, which is not seen for the pure Au NPs, Ce6, and physically mixed Ce6 and Au NPs. Moreover, the Ce6–Au NPs conjugate show evident cell prefoliation inhibition of U87 and HeLa cells under both X-ray and 18F-radiolabeled fluorodeoxyglucose (18F-FDG) exposure. These results indicate that interaction exists between Ce6 and Au NPs under radiation exposure. The mRNA sequencing results show that the tumor killing performance induced by Ce6–Au NPs may be due to regulation of the tumor microenvironment (TME) and immune-relevant signaling pathway. Our research proves that the rational combination of Au NPs and Ce6 can make better use of ionizing radiation energy and thus improve the therapeutic outcome of radiotherapy.

Purpose
To harmonize the use of color for MR relaxometry maps and therefore recommend the use of specific color-maps for representing T1, T2, and T2* maps and their inverses.

Methods
Perceptually linearized color-maps were chosen to have similar color settings as those proposed by Griswold et al. in 2018. A Delphi process, polling the opinion of a panel of 81 experts, was used to generate consensus on the suitability of these maps.

Results
Consensus was reached on the suitability of the logarithm-processed Lipari color-map for T1 and the logarithm-processed Navia color-map for T2 and T2*. There was consensus on color bars being mandatory and on the use of a specific value indicating “invalidity.” There was no consensus on whether the ranges should be fixed per anatomy.

Conclusion
The authors recommend the use of the logarithm-processed Lipari color-map for displaying quantitative T1 maps and R1 maps; likewise, the authors recommend the logarithm-processed Navia color-map for displaying T2, T2*, R2, and R2* maps.

This work originated with the Quantitative MR Study Group of the International Society of Magnetic Resonance in Medicine (ISMRM); it has the approval of the Publication Committee and of the Board of the ISMRM.

The development of clinical imaging techniques significantly improves diagnostic accuracy and provides guidance for personalized treatment of individuals. However, every single imaging modality has its distinct drawbacks that cannot fully fulfil the diagnosis requirement. Thus, rational combination of different imaging modalities can achieve more comprehensive information of disease and in this way provide better personalized treatment strategy. The hybrid PET/MRI has drawn increasing attention since its first clinical application. Imaging probes play an essential role in achieving qualified figures with accurate information of diseases. The application of nanotechnology promotes the development of versatile molecular probes for PET/MRI technique. Though there is an emerging clinical requirement, only a small number of multimodal PET/MRI probes have been investigated in preclinical research. Thus, this review tries to thoroughly summarize the nano-sized PET/MRI probes on their design, preparation and biological application. By discussing the strength and limitations of these current available PET/MRI multimodal probes, this work aims to figure out the further research direction and promote the possible clinic translation of the novel PET/MRI probes.