A miniaturized endoscopic laser system with laser steering has great potential to expand the application of minimally invasive laser treatment for micro-lesions inside narrow organs. The conventional systems require separate optical paths for endoscopic imaging and laser steering, which limits their application inside narrower organs. Herein, we present a novel endoscopic image-guided laser treatment system with a thin tip that can access inside narrow organs. The system uses a single fiber bundle to simultaneously acquire endoscopic images and modulate the laser-irradiated area. The insertion and operation of the system in a narrow space were demonstrated using an artificial vascular model. Repeated laser steering along set targets demonstrated accurate laser irradiation within a root-mean-square error of 28 $$\mu$$ μ m, and static repeatability such that the laser irradiation position was controlled within a 12 $$\mu$$ μ m radius of dispersion about the mean trajectory. Unexpected irradiation on the distal irradiated plane due to fiber bundle crosstalk was reduced by selecting the appropriate laser input diameter. The laser steering trajectory spatially controlled the photothermal effects, vaporization, and coagulation of chicken liver tissue. This novel system achieves minimally invasive endoscopic laser treatment with high lesion-selectivity in narrow organs, such as the peripheral lung and coronary arteries.

Mass spectrometry imaging (MSI) without labeling has the potential for faster screening in drug development. Matrix-assisted laser desorption/ionization (MALDI) is typically used, but it has a large matrix size and uneven drug distribution. Surface-assisted laser desorption/ionization (SALDI) using nanoparticles (NPs) may overcome these issues. Here, the influence of NPs, solvent ratio, and order of dropping of NPs on SALDI-MSI of protoporphyrin IX (PpIX), a cancer drug, are reported. A solution of PpIX in a 50% aqueous solution of 50% acetonitrile at a concentration of 10 μM was used. The NPs include ZnO, Fe 3 O 4 , and four types of TiO 2 . The NPs were fabricated by dissolving them on an aqueous 90% acetonitrile solution. Mass spectra were obtained with a time-of-flight mass spectrometer using a Nd:YAG laser at a 355-nm wavelength. The signal intensity using TiO 2 at a 0.5 mg/mL concentration in 50% acetonitrile was increased by 1.6-fold compared to that without TiO 2 . Changing the solvent to 90% acetonitrile gave a uniform TiO 2 distribution and a 9-fold increase in the signal intensity for PpIX. Among the four types of TiO 2 with different particle sizes and crystal structures, TiO 2 with a smaller particle size and a rutile crystal structure produced the highest signal intensity. Forming a layer on top of the PpIX also resulted in an increased signal intensity. Hence, SALDI using TiO 2 provides effective ionization of the drug. In the future, we plan to investigate a spray method for the ionization of PpIX using TiO 2 for the MSI of various drugs.