The diagnosis of gastrointestinal stromal tumor (GIST) using conventional endoscopy is difficult because submucosal tumor (SMT) lesions like GIST are covered by a mucosal layer. Near-infrared hyperspectral imaging (NIR-HSI) can obtain optical information from deep inside tissues. However, far less progress has been made in the development of techniques for distinguishing deep lesions like GIST. This study aimed to investigate whether NIR-HSI is suitable for distinguishing deep SMT lesions. In this study, 12 gastric GIST lesions were surgically resected and imaged with an NIR hyperspectral camera from the aspect of the mucosal surface. Thus, the images were obtained ex-vivo. The site of the GIST was defined by a pathologist using the NIR image to prepare training data for normal and GIST regions. A machine learning algorithm, support vector machine, was then used to predict normal and GIST regions. Results were displayed using color-coded regions. Although 7 specimens had a mucosal layer (thickness 0.4–2.5 mm) covering the GIST lesion, NIR-HSI analysis by machine learning showed normal and GIST regions as color-coded areas. The specificity, sensitivity, and accuracy of the results were 73.0%, 91.3%, and 86.1%, respectively. The study suggests that NIR-HSI analysis may potentially help distinguish deep lesions.

In this study, plasma gas species and temperature were varied to evaluate the reactive species produced and the bactericidal effect of plasma. Nitrogen, carbon dioxide, oxygen, and argon were used as the gas species, and the gas temperature of each plasma was varied from 30 to 90 °C. Singlet oxygen, OH radicals, hydrogen peroxide, and ozone generated by the plasma were trapped in a liquid, and then measured. Nitrogen plasma produced up to 172 µM of the OH radical, which was higher than that of the other plasmas. In carbon dioxide plasma, the concentration of singlet oxygen increased from 77 to 812 µM, as the plasma gas temperature increased from 30 to 90 °C. The bactericidal effect of carbon dioxide and nitrogen plasma was evaluated using bactericidal ability, which indicated the log reduction per minute. In carbon dioxide plasma, the bactericidal ability increased from 5.6 to 38.8, as the temperature of the plasma gas increased from 30 to 90 °C. Conversely, nitrogen plasma did not exhibit a high bactericidal effect. These results demonstrate that the plasma gas type and temperature have a significant influence on the reactive species produced and the bactericidal effect of plasma.

Recently, atmospheric low-temperature plasma (LTP) has attracted attention as a novel medical tool that might be useful for achieving hemostasis. However, conventional plasma sources are too big for use with endoscopes, and the efficacy of LTP for achieving hemostasis in cases of gastrointestinal bleeding is difficult to investigate. In this study, to solve the problem, we developed a 3D-printed LTP jet that has a diameter of 2.8 mm and metal body for endoscopic use. The characteristics, hemostasis efficacy, and safety were investigated. On investigating the basic characteristics of the developed plasma jet, the electron densities, gas temperatures, and reactive species were measured by emission spectroscopy and thermocouple. To evaluate the efficacy of such hemostatic treatment, porcine gastrointestinal bleeding was treated with the device. In addition, to investigate the safety of such treatment, the CO₂ LTP-treated tissue was compared with tissue that was treated with clipping-based or argon plasma coagulation–based hemostasis for 5 d, and hematoxylin and eosin staining was used to evaluate tissue damage in the treated regions. The measurement of emission spectroscopy, power, and electron density of various gas plasmas suggested that a high-density (10¹⁴ cm⁻³) LTP of CO₂ was generated by the LTP jet, and the gas temperature was 41.5°C at 3 mm from the outlet of the LTP jet. The CO₂ LTP achieved hemostasis of oozing blood by 70 ± 20 s. In addition, the CO₂ LTP resulted in earlier recovery than clipping-based or argon plasma coagulation–based hemostases, and the treated regions had no damage by the CO₂ LTP treatment. These results indicated that the developed LTP plasma jet has the potential to be used for endoscopic hemostasis.

In this study, a laparoscopic imaging device and a light source able to select wavelengths by bandpass filters were developed to perform multispectral imaging (MSI) using over 1000 nm near-infrared (OTN-NIR) on regions under a laparoscope. Subsequently, MSI (wavelengths: 1000–1400 nm) was performed using the built device on nine live mice before and after tumor implantation. The normal and tumor pixels captured within the mice were used as teaching data sets, and the tumor-implanted mice data were classified using a neural network applied following a leave-one-out cross-validation procedure. The system provided a specificity of 89.5%, a sensitivity of 53.5%, and an accuracy of 87.8% for subcutaneous tumor discrimination. Aggregated true-positive (TP) pixels were confirmed in all tumor-implanted mice, which indicated that the laparoscopic OTN-NIR MSI could potentially be applied in vivo for classifying target lesions such as cancer in deep tissues.

Gastric cancer (GC) is a commonly diagnosed cancer worldwide and one of the leading causes of cancer-related mortality.¹ Gastrectomy is a curative treatment for GC.² The effect of gastric remnant volume on the postoperative quality of life and nutritional status has been recognized. Furthermore, organ-sparing surgery is increasingly preferred.^{3 – 5} Japanese GC treatment guidelines (5th edition) recommend a proximal resection margin of at least 3 cm for tumors $\ge \mathrm{T}2$ in the case of an expansive growth pattern, whereas a proximal resection margin of at least 5 cm is required in the case of an infiltrative growth pattern.⁶ The large margin in the infiltrative growth patterns is attributed to the extensive submucosal or deeper layer invasions. Hence, if the extent of the non-exposed cancer invasion is identified, the stomach can be resected more appropriately. However, assessing the extent of the tumor and determining the appropriate resection margins during surgery remains difficult. Hence, several methods, including intraoperative endoscopy and endoscopic tattooing or clipping, that can identify the tumor extent and determine the appropriate surgical margins exist.^{7 – 10} However, the endoscopic determination of the extent of the GC that is not exposed to the mucosal surface remains difficult (e.g., the infiltrative growth pattern¹⁰).

The insertion of conventional colonoscopes can sometimes cause patients to experience pain during the procedure owing to the stretching of the mesentery. In this study, a prototype of a robotic colonoscope with a double-balloon and double-bend tube based on the conventional double-balloon endoscope was developed to simplify insertion and prevent the overstretching of the colon. Both the outer and inner tubes were confirmed to be free from interference from wires and sheaths. Additionally, all functions such as tip bending, inflation and deflation of the balloons, and actuator-driven pulling and pushing of the inner tube were operated properly. During the insertion test, the device could be reached the cecum of a colon model in approximately 442 s when operated by a non-medical operator. In addition, the device did not overstretch the colon model, thereby suggesting that the insertion mechanism can follow the shape of the colon model. As a result, the developed mechanism has the potential to navigate through a highly-bent colon without overstretching.