Nuclear medicine imaging visualizes specific molecules in vivo using positron-emitting nuclides such as 18F. For example, tumors often metabolize more glucose than normal tissues; thus, the PET tracer [18F]FDG (glucose labeled with 18F) is widely used clinically. Nuclear medicine provides high quantitativity and whole‑body coverage, making it valuable for early detection and therapy assessment.

We analyze in vivo changes induced by treatments in cancer and inflammatory disease models via nuclear medicine imaging, and we work to establish robust imaging‑based methods for evaluating therapeutic efficacy.

Fluorescence imaging uses molecules that emit fluorescence after light absorption to track drug biodistribution and probe biological functions. We also advance photoacoustic imaging, which detects acoustic waves generated from photoexcited molecules. Compared with light, acoustic waves are less attenuated by tissue, enabling imaging at greater depths.

We integrate fluorescence imaging for pharmacokinetic analyses and develop new fluorescent probes for diagnosis. In photoacoustics, we design agents whose signals change only at target sites, achieving high‑contrast lesion visualization.

Beta‑emitting radioisotopes have long been used in cancer therapy. Recently, however, alpha particles and Auger electrons—with much shorter ranges than beta particles—have drawn attention. In tissue, alphas travel only a few cells and Auger electrons only a few molecules, confining dose to extremely narrow regions and enabling highly selective ablation of target molecules and cells.

We establish stable labeling methods for alpha‑ and Auger‑emitting nuclides and evaluate therapeutic effects of the labeled agents. In particular, we investigate 211At (alpha emitter) and 191Pt (Auger emitter) to define clinical opportunities for each modality.

Caged compounds release bioactive molecules upon external stimuli (e.g., light), enabling localized control of biological functions. To date, activation typically relies on UV–visible light due to energy requirements, but limited tissue penetration constrains in vivo use to superficial regions (e.g., mouse brain cortex), hindering translation to humans.

We therefore focus on X‑rays, which penetrate deep tissues, as an external trigger for caged compounds in vivo. We search for structures that undergo deprotection upon X‑ray irradiation and develop agents activated only within the irradiated area, aiming to treat lesions while minimizing side effects on healthy tissues.

Near‑infrared photoimmunotherapy (PIT) is a cancer therapy that selectively kills tumor cells by irradiating NIR‑responsive agents localized at tumors. PIT spares surrounding normal cells and stimulates host immunity, yielding strong therapeutic effects. However, incomplete understanding of the cytotoxic mechanism hinders broader drug discovery.

We dissect PIT mechanisms using multiple approaches. For example, we discovered that photoresponsive agents aggregate upon light exposure and physically disrupt cancer cell membranes. We also develop novel agents that react efficiently even to weak light, aiming for higher therapeutic efficacy.