This paper describes a new rapid steady-state T₁ (RSS T₁) method for mapping the cerebral blood volume fraction ( CBVf) by magnetic resonance imaging (MRI). The principle is based on a two-compartment model of the brain (intra- and extravascular), and the effects of paramagnetic contrast agents on the intravascular longitudinal relaxation time T₁. Using appropriate parameters, an Inversion-Recovery-Fast-Low-Angle-Shot sequence acts like a low pass T₁ filter, suppressing signals from tissues with T₁≫ TR ( TR=repetition time). It was shown in vivo that, exceeding a particular contrast agent dose, the signal reaches its maximum (corresponding to the intravascular equilibrium magnetization), and is maintained for a duration related to the dose. Acquisitions during this steady state divided by an additional measure of the overall (intra- and extravascular) magnetization at thermal equilibrium provides the CBVf. Experiments were performed on healthy rats at 2.35 T using P760 (Gd³⁺—compound from Guerbet Laboratories) and Gd-DOTA. Because of its high longitudinal relaxivity, P760 is more convenient, and was used to show the feasibility of the method. The CBVf in different structures of the rat brain was compared. The average CBVf for the whole brain slice is 3.29%±0.69% ( n=15). The influence of transendothelial water exchange was quantified and transversal relaxation effects were found negligible in microvasculature. Finally, the sensitivity of the method to CBVf increases under hypercapnia was evaluated (1%/mm Hg PaCO₂), demonstrating its potential for longitudinal studies and functional MRI. Clinical applications are feasible since equivalent results were obtained with Gd-DOTA.

Understanding how localized brain interventions influence whole-brain dynamics is essential for deciphering neural function and designing therapeutic strategies. Using longitudinal functional MRI datasets collected from mice, we investigated the effects of focal interventions, such as thalamic lesions and chemogenetic silencing of cortical hubs. We found that these local manipulations disrupted the brain’s ability to sustain network-wide activity, leading to global functional connectivity (FC) reconfigurations. Personalized mouse brain simulations based on experimental data revealed that alterations in local excitability modulate firing rates and frequency content across distributed brain regions, driving these FC changes. Notably, the topography of the affected brain regions depended on the intervention site, serving as distinctive signatures of localized perturbations. These findings suggest that focal interventions produce consistent yet region-specific patterns of global FC reorganization, providing an explanation for the seemingly paradoxical observations of hypo- and hyperconnectivity reported in the literature. This framework offers mechanistic insights into the systemic effects of localized neural modulation and holds potential for refining clinical diagnostics in focal brain disorders and advancing personalized neuromodulation strategies.

Cardiotoxicity, especially human ether-a-go-go–related gene (hERG)–related toxicity, is a leading cause of drug failure or market withdrawal. Reducing hERG binding to obviate potential cardiac toxicity is crucial. Nanotechnology has been applied to drug delivery for reducing drug toxicity and improving efficacy, but few studies have addressed hERG-related cardiotoxicity. We report the use of self-assembling dendrimer nanosystems for drug formulation and delivery, which effectively reduced hERG binding and associated toxicity while promoting therapeutic efficacy. Specifically, these dendrimer nanosystems efficiently encapsulated the antimalarial drug chloroquine, the anticancer agent doxorubicin, and the NUPR1 inhibitor ZZW115, all three having high affinity to hERG channels. These nanoformulations showed three- to eightfold reduced hERG binding affinity, which, in animal models, translated to abolished toxicity. These nanodrugs exhibited prolonged circulation, leading to enhanced accumulation at disease sites and improved treatment outcomes. This study highlights the potential of nanotechnology to reduce hERG binding and related toxicity while improving drug efficacy, offering valuable perspectives for drug development.