Biomedical imaging is an essential tool for diagnosis and therapy of diseases such as cancers. It is
likely true that medicine has developed with biomedical imaging methods. Sensitivity and resolution of biomedical
imaging methods can be improved with imaging agents. Furthermore, it will be ideal if imaging agents could be
also used as therapeutic agents. Therefore, one dose can be used for both diagnosis and therapy of diseases (i.e., theragnosis).
This will simplify medical treatment of diseases, and will be also a benefit to patients. Mixed (Ln1xLn2yO3, x + y = 2)
or unmixed (Ln2O3) lanthanide (Ln) oxide nanoparticles (Ln = Eu, Gd, Dy, Tb, Ho, Er) are potential multi-modal imaging
and cancer therapeutic agents. The lanthanides have a variety of magnetic and optical properties, useful for magnetic
resonance imaging (MRI) and fluorescent imaging (FI), respectively. They also highly attenuate X-ray beam, useful for
X-ray computed tomography (CT). In addition gadolinium-157 (157Gd) has the highest thermal neutron capture cross section
among stable radionuclides, useful for gadolinium neutron capture therapy (GdNCT). Therefore, mixed or unmixed
lanthanide oxide nanoparticles can be used for multi-modal imaging methods (i.e., MRI-FI, MRI-CT, CT-FI, and MRICT-
FI) and cancer therapy (i.e., GdNCT). Since mixed or unmixed lanthanide oxide nanoparticles are single-phase and
solid-state, they can be easily synthesized, and are compact and robust, which will be beneficial to biomedical applications.
In this review physical properties of the lanthanides, synthesis, characterizations, multi-modal imagings, and cancer
therapy of mixed and unmixed lanthanide oxide nanoparticles are discussed.