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Positive diagnoses of gastric tumors from photodynamic diagnosis (PDD) images after the administration of 5-aminolevulinic acid are subjectively identified by expert endoscopists. Objective methods of tumor identification are needed to reduce potential misidentifications. We developed two methods to identify gastric tumors from PDD images. Method one was applied to segmented regions in the PDD endoscopic image to determine the region in LAB color space to be attributed to tumors using a multi-layer neural network. Method two aimed to diagnose tumors and determine regions in the PDD endoscopic image attributed to tumors using the convoluted neural network method. The efficiencies of diagnosing tumors were 77.8% (7/9) and 93.3% (14/15) for method one and method two, respectively. The efficiencies of determining tumor region defined as the ratio of the area were 35.7% (0.0–78.0) and 48.5% (3.0–89.1) for method one and method two, respectively. False-positive rates defined as the ratio of the area were 0.3% (0.0–2.0) and 3.8% (0.0–17.4) for method one and method two, respectively. Objective methods of determining tumor region in 5-aminolevulinic acid-based endoscopic PDD were developed by identifying regions in LAB color space attributed to tumors or by applying a method of convoluted neural network.

[Background] The 5-aminolevulinic acid (ALA)-based photodynamic diagnosis is based on the accumulation of photosensitizing protoporphyrin IX in the tumor after ALA administration. However, the mechanisms connecting exogenous ALA and tumor fluorescence in pancreatic cancer remain unclear. We aimed to elucidate the mechanism underlying the ALA-induced fluorescent. [Methods] Human pancreatic duct epithelial cells (hPDECs) and pancreatic cancer cell lines were used. The expressions of ALA-associated enzymes and membrane transporters in these cell lines were investigated. ALA-induced fluorescence was also investigated. [Results] The expression of oligopeptide transporter-1 (PEPT-1), through which ALA is absorbed, was significantly higher in AsPC-1 cells and lower in MIA PaCa-2 cells than in hPDECs. AsPC-1 cells showed rapid and intense fluorescence after ALA administration, and that was attenuated by PEPT-1 inhibition. ALA-induced fluorescence was not sufficiently strong in MIA PaCa-2 cells to distinguish the cells from hPDECs. [Conclusion] We revealed the association of PEPT-1 with ALA-induced fluorescence. Cancers expressing PEPT-1 could be easily distinguished by this technique from normal cells. These findings help develop novel diagnostic modalities for pancreatic cancer.

[Background] Endoscopy of the digestive tract is useful but is associated with significant pain to the patient. Its safety and tolerability could be improved by an immediate and objective method to evaluate the pain level and give feedback to the examiner. However, under the current circumstances, it is difficult to measure and assess the pain level objectively.[Methods] We previously developed a discomfort assessment device that measures the changes in brain activity caused by changes in the pain level by extracting the changes in the erythema index from facial color data. In this study, to evaluate the usefulness of this discomfort assessment device, the association between the changes in the erythema index of facial images during colonoscopy and the subjective pain level during the examination were evaluated. For the recording of the subjective pain level during the examination, a subjective pain level recording device that we developed to measure grip strength over time was used. The subjective pain level, facial image, and percutaneous venous oxygen saturation during the examination were recorded in 30 patients who underwent colonoscopy at our hospital. [Results] The duration of colonoscopy was divided into the insertion section and the removal section. The subjective pain level was found to be significantly greater during the insertion section than during the removal section, and the changes in the erythema index of the facial images were significantly different between the two groups. [Conclusion] These findings indicate that the erythema index changes on facial images determined by the discomfort assessment device may facilitate objective evaluation of the pain level during colonoscopy.

Background Recent improvement of the endoscopic system such as image enhancement has led to the better accuracy of the diagnosis of the gastric cancer. However, the objective and efficient detection method of the gastric cancer is still needed because the detection efficiency could sometimes be low due to the fact that the image enhancement diagnosis needs magnification for its full utilization. The photodynamic diagnosis (PDD) with oral intake of 5-aminolevulinic acid (5-ALA) has been widely used for the detection of the cancerous region for bladder cancer and glioblastoma. The application of the 5-ALA based PDD (5-ALA PDD) to the diagnosis of gastric cancer is recently reported. The efficiency of the detection is reported to be good, however, the objectivity of the method can be impaired by the photobleaching effect with fast decreasing of the intensity of the fluorescence under light exposure. In this article, we investigated the fluorescence spectrum of the gastric tumor and non-tumor mucosa of 5-ALA PDD and revealed the property of the photobleaching effect. Methods Example cases of PDD endoscopy of gastric tumor were investigated for cases of endoscopic submucosal dissection (ESD). Newly developed spectrometer using a spectrometer with a liquid crystal tunable filter was used for investigating the fluorescence spectrum of 5-ALA PDD. The assumed tumor region and non-tumor region in gastric mucosa were biopsied and the fluorescence spectrum was measured using the spectrometer consecutively several times, to estimate the photobleaching effect. Results The fluorescence spectrum has a primary peak at 630 nm, with a broad peak ranging from 660 to 700 nm. The 630 nm peak diminished quickly upon ultraviolet light exposure, whereas the broad peak from 660 to 700 nm diminished slowly. The sum of the altitudes at 660-700 nm, normalized to the altitude at 600 nm, was not as affected by the photobleaching effect as the 630 nm peak was, and can thus be used for 5-ALA-based PDD. Conclusions The 5-ALA PDD using the average fluorescence altitude of 660-700 nm instead of the peak altitude at 630 nm, is shown to be more effective in distinguishing between tumorous and non-tumorous tissues, because of the lower photobleaching effect at this specific spectral range. The finding is expected to greatly improve the objective diagnosis of gastrointestinal cancers by 5-ALA-based photodynamic diagnostic endoscopy.

Background Photodynamic diagnosis (PDD) is an optical imaging technology based on the fundamental biological features of porphyrin metabolized in cancer cells. We reported the usefulness of laser-based photodynamic endoscopic diagnosis (LPDED) with 5-aminolevulinic acid (5-ALA) for early gastric cancers. However, the first-generation prototype endoscope system had the flaw that the images captured were rather dark. To overcome this, we constructed a next-generation endoscope system for LPDED. Methods We evaluated the usefulness of the next-generation prototype endoscope system, called Sie-P2, for brighter LPDED to detect early gastric cancer (EGC) and gastric adenoma. The 14 patients diagnosed with EGC and/or gastric adenoma who underwent endoscopic submucosal dissection (ESD) at our hospital between April 2018 and March 2019 were enrolled consecutively in this study. Patients were administered 5-ALA orally and LPDED was performed 3 h later. The primary endpoint was the presence of fluorescence in tumors when we performed LPDED. The secondary endpoint was to assess the adverse events related to each LPDED procedure. Results One patient was excluded because of a contraindication, while the remaining 13 patients (median 72 years, range 56-77; one female) with 16 lesions were assessed. There were 10 elevated lesions and 6 flat/depressed lesions; there were 10 EGCs and 6 adenomas. LPDED-fluorescence was detected in all 16 lesions (sensitivity 100%, 95% confidence interval 79-100%). Two cases showed temporary, though not substantial, elevation in blood liver function tests. Conclusion All lesions examined were LPDED-positive, indicating that the Sie-P2 system could be useful.

Photodynamic therapy (PDT) is a therapeutic method used to destroy tumor tissue via reactive oxygen. Notably, reactive oxygen is induced by a combination of photosensitizers, including talaporfin sodium (TS) and laser light. Gastric cancer cell lines, MKN45 and MKN74, were used to evaluate the effect of TS-PDT in vitro. The antitumor effect of TS-PDT, which was evaluated via cellular viability assay, on MKN74 was weaker than that on MKN45 cells, suggesting that MKN74 cell could be resistant to TS-PDT. However, using a higher TS concentration or setting a longer treatment time (24 h) resulted in effective TS-PDT treatment on MKN74 cells. In addition, when irradiation power of LED was raised up to 5.06 J/cm2, TS-PDT was able to induce an antitumor effect on MKN74 cells. This suggested that the difference in TS-PDT efficacy between MKN45 and MKN74 cells is based on the difference in cellular uptake of TS. As expected, uptake of TS by MKN74 cells was lower than that by MKN45 cells. The expression levels of low-density lipoprotein (LDL) receptor in MKN74 cells were lower than those in MKN45 cells. With GW3965 treatment, an agonist/activator of Liver X Receptor, LDL receptor expression was reduced, weakening the TS-PDT effect. Furthermore, as a hydroxymethylglutaryl-Coenzyme A reductase inhibitor, treatment using simvastatin increased LDL receptor expression, leading to enhancement of the TS-PDT effect on MKN74 cells. In conclusion, the difference in LDL receptor expression between the two gastric cell lines could influence TS-PDT efficacy; simvastatin may enhance the antitumor effect of TS-PDT through upregulating the LDL receptor even on PDT-resistant gastric cancer cells.