Title: Diffusion and contrast-enhancement MRI phenotypes associated with immune checkpoint inhibitor exposure and with immune cell infiltration in brain metastases

Keypoints: 

• Question- Can MRI phenotypes combining diffusion (ADC) and contrast-enhancement (CE) noninvasively track immune checkpoint inhibitor (ICI)-induced immune infiltration and tissue changes in brain metastases?

• Findings- ICI-treated metastases showed elevated highADC-highCE voxels (linked to higher diffusivity and vascular permeability) and reduced lowADC-lowCE voxels, correlating with increased CD45+ immune cell density (ρ = 0.56) and inversely with sparse infiltration (ρ = -0.64). Corticosteroids masked these ICI-driven MRI changes, diminishing their predictive utility.

• Meaning - ADC-CE phenotypes offer a practical, noninvasive method to monitor ICI effects on brain metastases, emphasizing their value in steroid-free contexts. This advances personalized immunotherapy by enabling real-time assessment of immune activity without biopsies, while cautioning against steroid interference in biomarker interpretation.

Title: A Histopathologic Correlation Study Evaluating Glymphatic Function in Brain Tumors by Multiparametric MRI

Keypoints: 

• Question - Is there a correlation between quantitative parameters related to brain tumors and the function of the lymphatic system and the expression level of aquaporin-4 (AQP4)? What are the differences in the effects of different types of brain tumors on intracerebral lymphatic drainage?
• Findings - Tumor-induced mechanical compression leads to lymphatic system dysfunction, which increases peritumoral fluid accumulation, which in turn upregulates peritumoral AQP4 expression to promote molecular efflux. Tumor volume was negatively correlated with the clearance capacity of the lymphatic system, and AQP4 expression in the peritumoral edema area was positively correlated with the volume of edema.
• Meaning - This study revealed the effects of brain tumors on lymphatic system function and cerebrospinal fluid dynamics, and clarified the relationship between tumor size, lymphatic system function, AQP4 expression and peritumoral edema. These results help to understand intracranial fluid dynamics and provide ideas for the treatment of tumor-associated cerebral edema.