Shigetoshi Okazaki

Optical diagnosis of gastric cancer using near-infrared multichannel Raman spectroscopy with a 1064-nm excitation wavelength

BackgroundGastric cancer is one of the most common cancers in Japan. The use of endoscopy is increasing, along with the number of histological examinations of specimens obtained by endoscopy. However, it takes several days to reach a diagnosis, which increases the medical expense. Raman spectroscopy is one of the available optical techniques, and the Raman spectrum for each molecule and tissue is characteristic and specific. The present study investigated whether Raman spectroscopy can be used to diagnose gastric cancer.MethodsA total of 251 fresh biopsy specimens of gastric carcinoma and non-neoplastic mucosa were obtained from 49 gastric cancer patients at endoscopy. Without any pretreatment, the fresh specimens were measured with a near-infrared multichannel Raman spectroscopic system with an excitation wavelength of 1064 nm, and Raman spectra specific for the specimens were obtained. A principal component analysis (PCA) was performed to distinguish gastric cancer and non-neoplastic tissue, and a discriminant analysis was used to evaluate the accuracy of the gastric cancer diagnosis.ResultsThe Raman spectra for cancer specimens differed from those for non-neoplastic specimens, especially at around 1644 cm−1. Sensitivity was 66%, specificity was 73%, and accuracy was 70%. The accuracy of diagnosis using the single Raman scattering intensity at 1644 cm−1 was 70%, consistent with the PCA result.ConclusionsThe present results indicate that near-infrared multichannel Raman spectroscopy with a 1064-nm excitation wavelength is useful for gastric cancer diagnosis. Establishment of a Raman diagnostic system for gastric cancer may improve the clinical diagnosis of gastric cancer and be beneficial for patients.

Production of Short-Lived Positron-Emitting Radioactive Nuclei Using a 2.4 TW, 50 fs Tabletop Laser

We produced a short-lived positron-emitting radioisotope 13N by using MeV-order deuterons emitted from relativistic laser plasma generated by a tabletop laser. For generation of the plasma, laser pulses with a peak power of 2.4 TW and a pulse duration of 50 fs were focused with a 10 Hz repetition rate onto a microporous polytetrafluoroethylene film loaded with deuterated polystyrene, where the maximum intensity at the focal point was 3 ×1018 W/cm2. The irradiation of melamine resins by deuterons for 55 s produced 13N of 1.00 ±014 Bq through a nuclear reaction of 12C(d,n)13N. This is the first report on an actual activation using a table-sized femtosecond laser.

Generation of over 5MeV carbon ions from a fibrous polytetrafluoroethylene film irradiated with a 2.4TW, 50fs tabletop laser

The authors generated energetic carbon ions C4+ above 5MeV by focusing 2.4TW, 50fs, 10Hz laser pulses onto a fibrous polytetrafluoroethylene (PTFE) film. The PTFE film is composed only of carbon and fluorine and has microporous structure. A laser target made of this film is useful in generating carbon ions. A polyethyleneterephthalate film was also used as an alternative target for comparison. The results show that the number of carbon ions emitted from the PTFE target was approximately two orders of magnitude greater than that from a polyethyleneterephthalate target.

Generation of MeV-Order Deuterons by Focusing Low-Terawatt Tabletop Laser Pulses onto Microporous Polytetrafluoroethylene Film Loaded with Deuterated Polystyrene

By focusing 2.4 TW, 50 fs laser pulses onto a microporous polytetrafluoroethylene film loaded with deuterated polystyrene, we successfully generated MeV-order deuterons. The number of over-1-MeV deuterons generated during 640 shots is estimated to be about 8 ×106.

Energetic proton and deuteron generation from a microporous polytetrafluoroethylene film with deuterated polystyrene using a 2.4-TW table-top laser

Protons and deuterons over 1 MeV in energy were generated by 2.4-TW, 50-fs, 10-Hz laser pulses interacting with a film target. In particular, microporous polytetrafluoroethylene film infiltrated with deuterated polystyrene was effective for this target.