Magnetic resonance imaging (MRI) is a non-invasive imaging technology to diagnose health conditions, showing the weakness of low sensitivity. Herein, we synthesize a contrast agent, SPIO@SiO₂@MnO₂, which shows decreased T₁ and T₂ contrast intensity in normal physiological conditions. In the acid environment of tumor or inflamed tissue, the manganese dioxide (MnO₂) layer decomposes into magnetically active Mn²⁺ (T₁-weighted), and the T₁ and T₂ signals are sequentially recovered. In addition, both constrast quenching-activation degrees of T₁ and T₂ images can be accurately regulated by the silicon dioxide (SiO₂) intermediate layer between superparamagnetic iron oxide (SPIO) and MnO₂. Through the “dual-contrast enhanced subtraction” imaging processing technique, the contrast sensitivity of this MRI contrast agent is enhanced to a 12.3-time difference between diseased and normal tissue. Consequently, SPIO@SiO₂@MnO₂ is successfully applied to trace the tiny liver metastases of approximately 0.5 mm and monitor tissue inflammation.

磁共振成像（MRI）是一种诊断健康状况的非侵入性成像技术，显示出灵敏度低的弱点。在此，我们合成了一种造影剂 SPIO@SiO ₂ @MnO ₂，​​它在正常生理条件下显示出降低的 T ₁和 T ₂对比强度。在肿瘤或发炎组织的酸性环境中，二氧化锰（MnO ₂）层分解成磁活性Mn ²⁺（T ₁加权），T ₁和T ₂信号依次恢复。此外，T ₁和 T _{2的淬火激活度}超顺磁性氧化铁 (SPIO) 和 MnO ₂之间的二氧化硅 (SiO ₂ ) 中间层可以精确调节图像。通过“双对比增强减影”成像处理技术，该MRI造影剂的对比敏感度增强至病变组织与正常组织的12.3倍差。因此，SPIO@SiO ₂ @MnO ₂成功应用于追踪约 0.5 mm 的微小肝转移并监测组织炎症。