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Present condition and activities of Jeddah Endoscopy Center managed in cooperation with Saudian and Japanese doctors are reported. Total number of patients examined are 1,183 cases; 73% of which were subjected to endoscopy and 27% were to fluoroscopy. With respect to the stomach diseases, gastric cancer and ulcer were found in 16% and 14.7%, respectively. On the other hand, high incidences of severe atrophic gastritis and haemorrhagic or erosive gastritis accounted totally 64.7% of all stomach diseases were noted. Out of 264 cases of duodenal diseases, duodenal ulcer was diagnosed in number of 202 cases (76%). The ratio between gastric and duodenal ulcer was, therefore, approximately 1:6. It was further noted that most of patients with esophagus cancer were found in males having the local habit of taking green tobacco. From the results obtained, discussions were made on the statistical differences of gastrointestinal diseases between Saudi Arabia and Japan. [ABSTRACT FROM AUTHOR]

Background: Nivolumab monotherapy is the standard second-line treatment for advanced esophageal squamous cell carcinoma (ESCC) after failure of platinum-based chemotherapy without anti-PD-1 antibody. Fixed dosing with 240 mg every 2 weeks was approved initially, followed by fixed dosing with 480 mg every 4 weeks based on pharmacokinetics data. However, information on the comparative efficacy and safety of the two doses remains limited., Methods: We compared progression-free survival (PFS), overall survival (OS), objective response rate (ORR), and the incidence of adverse events (AEs) between the two doses in 117 patients who received second-line (n = 85) or later-line (n = 32) nivolumab monotherapy at our institution between January 2016 and December 2021., Results: In the second-line group, patient characteristics for the 240 mg and 480 mg groups were as follows (240 mg vs. 480 mg): performance status (PS) 0/1/2 was 34/61/5% vs. 54/42/4%, and prior fluoropyrimidine plus platinum therapy (FP) was 81.3% vs. 42.3%. In the later-line group, the characteristics were: PS 0/1/2 was 28/60/12% vs. 14/86/0%, and prior FP was 60.0% vs. 42.8%. ORR was 11.9 vs. 24.0% in the second-line group (p = 0.19) and 0 vs. 14.3% in the later-line group (p = 0.22). Median PFS was 1.7 vs. 4.1 months on second-line (hazard ratio [HR] 0.60, 95% confidence interval [CI] 0.35-1.01, p = 0.056) and 1.4 vs. 1.8 months on later-line (HR 0.58, 95% CI 0.23-1.46, p = 0.25); AEs of any grade were observed in 58.3 vs. 69.7%, respectively., Conclusions: The efficacy and safety of the two doses of nivolumab monotherapy were comparable in patients with advanced ESCC., (© 2024. The Author(s).)

Pancreatic mixed neoplasms are very rare. We herein report a unique case of pancreatic mixed acinar-neuroendocrine-ductal carcinoma with trilineage differentiation. The patient was an 83-year-old woman referred to our hospital due to anemia and a pancreatic mass. Contrast-enhanced computed tomography revealed a 60-mm mass in the pancreas. Subtotal stomach-preserving pancreaticoduodenectomy was performed. The postoperative pathological diagnosis was mixed acinar-neuroendocrine-ductal carcinoma. Postoperative chemotherapy was conducted according to the adenocarcinoma and neuroendocrine carcinoma protocols. The patient died 26 months postoperatively. Choosing appropriate chemotherapy for mixed neoplasms is difficult. Cancer gene panel testing, if possible, may support the choice of therapeutic agents.

Objectives: Most research on duodenal ulcers has focused on bulbar ulcers; details on post-bulbar ulcers remain largely unknown. This study was conducted to determine the characteristics of patients with post-bulbar duodenal ulcers depending on their location., Methods and Materials: We conducted a retrospective study of hospitalized patients newly diagnosed with duodenal ulcers on endoscopy at a tertiary referral center in Japan between April 2004 and March 2019. Five hundred fifty-one patients diagnosed with duodenal ulcers were extracted for analysis., Results: Ulcers were observed only in the bulbus in 383 cases, only in the post-bulbar duodenum in 82 cases, and were co-existing in both areas in 86 cases. The Bulbar group had less comorbidities and was more likely to have atrophic gastritis, while the Post-bulbar and Co-existing groups were more likely to be admitted for non-gastrointestinal conditions. Regular acid suppressant use was more common in the post-bulbar group than in the Bulbar group. Bulbar ulcers were associated with a shorter length of stay relative to post-bulbar and co-existing ulcers, but ulcer location was not an independent predictor of length of stay. Patients with co-existing bulbar and post-bulbar ulcers have characteristics similar to those with post-bulbar ulcers alone., Conclusion: Patients with post-bulbar ulcers and those with co-existing bulbar and post-bulbar ulcers have different characteristics and outcomes relative to patients with bulbar ulcers., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background and Objectives: During EUS-guided choledochoduodenostomy (EUS-CDS), fistula dilation before stent insertion is associated with adverse events (AEs), such as bile leakage and peritonitis. We hypothesized that EUS-CDS without fistula dilation using a novel self-expandable metal stent (SEMS) with a thin delivery system could overcome this problem, and we conducted this study to evaluate its feasibility and safety., Methods: This was an open-label, single-arm, phase II study at a single institution. We planned EUS-CDS without fistula dilation using a fully covered SEMS with a 5.9-Fr delivery system for unresectable malignant distal biliary obstruction. The primary outcome was overall technical success. Secondary outcomes were technical success without fistula dilation, procedure time, functional success, time to recurrent biliary obstruction, and AEs. The planned sample size was 25 patients., Results: In total, 24 patients were included in this study. In 21 patients, EUS-CDS was performed as primary drainage. The overall technical success rate was 100% (24 of 24 patients). The technical success rate without fistula dilation was 96% (23 of 24). The median procedure time was 16 min (range, 10-66 min). The functional success rate was 96% (23 of 24). The median time to recurrent biliary obstruction was 148 days (95% confidence interval, 29-266 days). There were no procedure-related AEs. Furthermore, computed tomography immediately after the procedure showed no leakage of contrast medium into the abdominal cavity in any patient., Conclusions: EUS-guided choledochoduodenostomy without fistula dilation using a fully covered SEMS with a 5.9-Fr delivery system is feasible with a high probability and can be achieved quickly while effectively preventing bile leakage and peritonitis., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2023 The Author(s). Published by Wolters Kluwer on behalf of Scholar Media Publishing.)

Pancreatic cancer is one of the most lethal human malignancies, in part because it is often diagnosed at late stages when surgery and systemic therapies are either unfeasible or ineffective. Therefore, diagnosing pancreatic cancer in earlier stages is important for effective treatment. However, because the signs and symptoms may be nonspecific and not apparent until the disease is at a late stage, the timely diagnoses of pancreatic cancer can be difficult to achieve. Recent studies have shown that selective screening and increased usage of biomarkers could improve the early diagnosis of pancreatic cancer. In this review, we discuss recent advancements in the early detection of pancreatic ductal carcinoma and precancerous lesions. These include innovations in imaging modalities, the diagnostic utility of various biomarkers, biopsy techniques, and population-based surveillance approaches. Additionally, we discuss how machine learning methods are being applied to develop integrated methods of identifying individuals at high risk of developing pancreatic disease. In the future, the overall survival of pancreatic cancer patients could be improved by the development and adoption of these new methods and techniques.

Aims: Peroxisome proliferator-activated receptor-alpha (PPARα) levels are markedly lower in the kidneys of chronic kidney disease (CKD) patients. Fibrates (PPARα agonists) are therapeutic agents against hypertriglyceridemia and potentially against CKD. However, conventional fibrates are eliminated by renal excretion, limiting their use in patients with impaired renal function. Here, we aimed to evaluate the renal risks associated with conventional fibrates via clinical database analysis and investigate the renoprotective effects of pemafibrate, a novel selective PPARα modulator mainly excreted into the bile., Main Methods: The risks associated with conventional fibrates (fenofibrate, bezafibrate) to the kidneys were evaluated using the Food and Drug Administration Adverse Event Reporting System. Pemafibrate (1 or 0.3 mg/kg/day) was administered daily using an oral sonde. Its renoprotective effects were examined in unilateral ureteral obstruction (UUO)-induced renal fibrosis model mice (UUO mice) and adenine-induced CKD model mice (CKD mice)., Key Findings: The ratios of glomerular filtration rate decreased and blood creatinine increased were markedly higher after conventional fibrate use. Pemafibrate administration suppressed increased gene expressions of collagen-I, fibronectin, and interleukin 1 beta (IL-1β) in the kidneys of UUO mice. In CKD mice, it suppressed increased plasma creatinine and blood urea nitrogen levels and decreased red blood cell count, hemoglobin, and hematocrit levels, along with renal fibrosis. Moreover, it inhibited the upregulation of monocyte chemoattractant protein-1, IL-1β, tumor necrosis factor-alpha, and IL-6 in the kidneys of CKD mice., Significance: These results demonstrated the renoprotective effects of pemafibrate in CKD mice, confirming its potential as a therapeutic agent for renal disorders., Competing Interests: Declaration of competing interest Pemafibrate was provided by Kowa Company, Ltd. (Tokyo, Japan). There are no further patents, products in development, or marketed products to declare., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Competing Interests: Competing interests The authors declare that they have no conflict of interest.

Attempts at performing endoscopic ultrasound-guided tissue acquisition (EUS-TA) with a 19G needle are increasing because histological diagnosis and comprehensive genomic profiling are a necessity. However, the diagnostic ability of the 19G fine-needle biopsy (FNB) needle, especially the third-generation FNB needle, is unclear and has been retrospectively reviewed. The 19G TopGain needle was used in 147 patients and 160 lesions between September 2020 and December 2021. The technical success rate of the biopsies was 99.4% (159/160). The early adverse event rate was 4.1% (6/147), and moderate or severe adverse event rate occurrence was 2.0% (3/147). The sensitivity, specificity, and accuracy of the 19G TopGain needle for 157 lesions with a confirmed diagnosis were 96.7%, 100%, and 96.8%, respectively. Rescue EUS-TA using the 19G TopGain needle was performed for nine lesions, and a successful diagnosis was made in six of these lesions (66.7%). The diagnostic ability of EUS-TA using the third-generation 19G TopGain needle was favorable. However, the use of 19G FNB needles may increase adverse events. Therefore, EUS-TA with a 19G FNB needle is mainly indicated in lesions where comprehensive genomic profiling may be necessary or the diagnosis could not be determined via EUS-TA using the 22G needle.

Background and study aims  Recently, the utility of endoscopic ultrasound-guided intervention without fistula dilation (EUS-IV WoD) has been reported to prevent adverse events. We clinically evaluated cases in which EUS-IV WoD was attempted using a novel self-expandable metallic stent (SEMS); this is a fully covered, laser-cut SEMS that has a tapered and stiff tip specifically designed for a 0.025-inch guidewire and a relatively thin, 7F delivery system. Patients and methods  We retrospectively evaluated cases wherein EUS-IV WoD was attempted using the novel SEMS between March and December 2021. Results  Treatment of 11 patients by EUS-IV WoD with the novel SEMS was attempted. The technical success rate for EUS-IV was 100 % and the clinical success rate was 100 %; the success rate for EUS-IV WoD was 72.8 %. Of these, the procedural success rate for EUS-IV WoD was 100 % in EUS-biliary drainage (BD) and 57.1 % in non-EUS-BD. Early adverse events were observed in 27.3 % of patients (3/11): mild abdominal pain in two patients and moderate bleeding in one patient. The abdominal pain cases were both cases of EUS-IV WoD failure and required fistula dilation. Conclusions  The novel stent may be useful for EUS-IV WoD, especially in EUS-BD., Competing Interests: Competing interests The authors declare that they have no conflict of interest., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).)

Objectives: Comprehensive genomic profiling (CGP) has been approved in Japan since June 2019, enabling mutation-specific therapy. Although tissue sampling via endoscopic ultrasound-guided tissue acquisition (EUS-TA) is standard in pancreatic cancer, reports on obtaining appropriate samples for CGP, especially for the OncoGuide NCC Oncopanel System (NOP) and FoundationOne CDx (FOne), are lacking. Therefore, we investigated the success rate and factors related to appropriate EUS-TA sampling for CGP analysis suitability in unresectable pancreatic ductal adenocarcinoma (UR-PDAC)., Methods: Participants comprised 150 UR-PDAC patients who underwent EUS-TA and tumor sample evaluation for CGP analysis suitability between June 2019 and December 2021. The proportion of patients meeting the criteria was evaluated considering tumor size, puncture lesion, presence of metastasis, type and size of puncture needle, suction method, number of punctures, and puncture route., Results: In total, 39.2% (60/153) of samples met NOP analysis suitability criteria and 0% met FOne analysis suitability criteria. The suitability rate was significantly higher with 19G fine-needle biopsy (FNB) (56.0%; 42/75) than with 22G FNB (32.6%; 14/43) and 22G fine-needle aspiration (11.4%; 4/35). Nineteen-gauge needle (odds ratio [OR] 2.53; 95% confidence interval [CI] 1.15-5.57; P = 0.021) and FNB (OR 3.57; 95% CI 1.05-12.20; P = 0.041) were independent factors contributing to NOP analysis suitability. Among 30 patients who underwent actual NOP analysis, the analysis success rate was 100% (30/30)., Conclusion: In sample collection via EUS-TA, 19G and FNB needles contribute to NOP analysis suitability., (© 2022 Japan Gastroenterological Endoscopy Society.)

Background: In recent years, the number of patients with hepaticojejunostomy anastomotic strictures has increased. Balloon dilation and placement of multiple plastic stents have proven effective for hepaticojejunostomy anastomotic strictures. However, for refractory strictures, there is often a need for repeated endoscopic procedures within a short period. This study aimed to assess the efficacy and safety of the new saddle-cross technique, which uses two fully covered self-expandable metallic stents., Methods: This was a retrospective analysis of 20 patients with benign hepaticojejunostomy anastomotic strictures who underwent placement of two fully covered self-expandable metallic stents at the National Cancer Center, Japan, from November 2017 to June 2021., Results: The technical and clinical success rates were 100% (20/20). The median time of the procedure was 61 (range 25-122) min. The scheduled stent removal rate was 70% (14/20). Spontaneous dislodgement of the stent was observed on computed tomography in five patients (25.0%). The non-restenosis rate 12 months after the saddle-cross technique was 88.2% (15/17). Procedure-related early adverse events included mild ascending cholangitis in three patients (15.0%) and sepsis in one patient (5.0%). Procedure-related late adverse events included mild ascending cholangitis in three patients (15.0%) and bile duct hyperplasia in one patient (5.0%)., Conclusions: The saddle-cross technique performed using two fully covered self-expandable metallic stents resulted in promising long-term stricture resolution with a high technical success rate. Based on these findings, the saddle-cross method can be considered an option for the standard procedure for benign hepaticojejunostomy anastomotic strictures., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: There are limited studies on the results of comprehensive genomic profiling testing for pancreatic cancer tissue specimens by endoscopic ultrasound-guided tissue acquisition (EUS-TA). This study aimed to evaluate the proportion of specimens obtained by EUS-TA using a 19-gauge (G) fine-needle biopsy (FNB) needle for unresectable pancreatic cancer (UR-PC) that met the OncoGuide ™ NCC Oncopanel System (NOP) analysis suitability criteria., Methods: In this single-arm, prospective, phase II study, EUS-TA was performed using a 19G FNB biopsy needle in patients with suspected UR-PC based on a contrast-enhanced computed tomography scan. The primary endpoint was the proportion of patients who met the NOP analysis suitability criteria, with a threshold, expected value, α-error, and power of 40%, 70%, 0.025, and 0.9, respectively, and the planned number of enrolled patients was 33. The NOP analysis suitability criteria were defined as tumor cell content ≥ 20% and tissue size ≥ 4 mm 2 ., Results: Thirty-three patients were enrolled. The procedural success rate was 100%, and the cytodiagnosis of class V was observed in all patients. The proportion of patients meeting the NOP analysis suitability criteria was 63.6% (95% CI 47.22-80.05), which satisfied the predefined criteria to be considered valid. Adverse events occurred in 9.0% of the patients., Conclusions: The proportion of patients with UR-PC who met the NOP analysis suitability criteria for EUS-TA using a 19G FNB needle was effective for achieving the primary endpoint, making it a valid test method. Adverse events occurred at a higher rate than that previously reported., (© 2022. Japanese Society of Gastroenterology.)

As COVID-19 continues to spread, infection risk on public transport is concerning. Air exchange rates (ACH) and advection-diffusion of CO 2 and particles were determined in a route bus to evaluate the infection risk. ACH increased with bus speed whether windows were open or closed, and ACH were greater when more windows were open. With two open windows, ACH was greater when a front and rear window were open than when two rear windows were open. With both front and rear ventilation fans set to exhaust, ACH was more than double that when both were set to supply. With air conditioning (AC) off, CO 2 and particles spread proportionally at the same rate from a source, whereas with the AC on, the spread rate of particles was about half that of CO 2 , because particles might be trapped by a prefilter on the AC unit. Infection risk can be reduced by equipping AC unit with an appropriate filter. Calculations with a modified Wells-Riley equation showed that average infection risk was reduced by 92% in the moving bus with windows open comparing to with windows closed. When the bus was moving with windows closed, exhaust fan operation reduced the average risk by 35%., (© 2022 The Authors. Indoor Air published by John Wiley & Sons Ltd.)

Background: Despite the increasing availability of effective drugs, around one-third of patients with epilepsy are still resistant to pharmacotherapy. Gene therapy has been suggested as a plausible approach to achieve seizure control, in particular for patients with focal epilepsy. Because seizures develop across wide spans of the brain in many forms of epilepsy, global delivery of the vectors is necessary to tackle such generalized seizures. Neuroligin 2 (NL2) is a postsynaptic cell adhesion molecule that induces or strengthens inhibitory synaptic function by specifically combining with neurexin 1., Methods: In the present study, we applied an adeno-associated virus (AAV) type 9 vector expressing NL2 to modulate neuronal excitability in broad areas of the brain in epileptic (EL) mice, a model of polygene epilepsy. We administered the AAV vector expressing Flag-tagged NL2 under the synapsin I promoter (AAV-NL2) via cardiac injection 6 weeks after birth., Results: Significant reductions in the duration, strength and frequency of seizure were observed during a 14-week observation period in NL2-treated EL mice compared to untreated or AAV-green fluorescent protein-treated EL mice. No behavioral abnormality was observed in NL2-treated EL mice in an open-field test. Immunohistochemical examination at 14 weeks after AAV-NL2 injection revealed the expression of exogenous NL2 in broad areas of the brain, including the hippocampus and, in these areas, NL2 co-localized with postsynaptic inhibitory molecule gephyrin., Conclusions: Global brain delivery of NL2 by systemic administration of AAV vector may provide a non-invasive therapeutic approach for generalized epilepsy., (© 2021 John Wiley & Sons, Ltd.)

Objectives: To evaluate the feasibility and safety of endoscopic ultrasound-guided choledochoduodenostomy (EUS-CDS) without fistula dilation using a novel self-expandable metal stent (SEMS)., Methods: This retrospective study examined patients who underwent EUS-CDS for malignant distal biliary obstruction between October 2017 and May 2021 at the National Cancer Center, Japan. The primary outcome was a technical success without fistula dilation. Secondary outcomes were the overall technical success, clinical success, adverse events (AEs), procedure time, recurrent biliary obstruction (RBO), and time to RBO (TRBO)., Results: Forty-one patients were enrolled; 31 patients underwent EUS-CDS with fistula dilation using a conventional SEMS with 7.5-8.5-Fr delivery system (conventional SEMS group), and 10 patients underwent EUS-CDS without fistula dilation using the novel SEMS with a 5.9-Fr delivery system (novel SEMS group). In the novel SEMS group, the rate of technical success without fistula dilation was 90%. There were no differences in overall technical success (100% vs. 97%, p = 1.00), clinical success (80% vs. 90%, p = 0.58), and overall AEs (10% vs. 23%, p = 0.65) rates between the novel and conventional SEMS groups. In the novel SEMS group, no early AEs were observed and no bile leakage into the abdominal cavity was observed on the computed tomography scan after the procedure. The median procedure time was significantly shorter in the novel SEMS group (17 min vs. 24 min, p = 0.03). RBO and median TRBO did not differ between the 2 groups., Conclusions: EUS-CDS without fistula dilation using the novel SEMS with a 5.9-Fr delivery system is technically feasible, straightforward, quick, and safe., Competing Interests: The authors declare that they have no conflict of interest., (© 2021 The Authors. DEN Open published by John Wiley & Sons Australia, Ltd on behalf of Japan Gastroenterological Endoscopy Society.)

Background: Oxidative stress is thought to be closely related to epileptogenesis. We have previously reported that nitric oxide (NO) levels are higher in epilepsy-prone EL mice between the ages of 3 and 8 weeks than in control mice. However, NO is divided into two fractions, nitrite (NO 2 ) and nitrate (NO 3 ), which appear to play different roles in epileptogenesis., Methods: NO 2 and NO 3 levels were measured, in EL mice and the control mice, in the parietal cortex, which is thought to be the primary epileptogenetic center in EL mice, and measured in the hippocampus, which is thought to be the secondary center., Results: NO 3 levels in the hippocampus and parietal cortex of the immature EL mice (3 to 8 weeks of age) were significantly higher than those in the control mice; NO 2 levels were significantly higher in the EL mice throughout the study period. The NO 3 levels were significantly higher than the NO 2 levels in the immature EL mice, but after the onset of ictogenesis at 10 weeks of age, the relative levels of the two fractions reversed., Conclusion: The reversal of the NO fraction distribution at the onset of seizures that we observed may be related to the developmental process of seizure susceptibility in the neural network of EL mice.

A public health collaboration between medical professionals and Japan's professional football league for rubella awareness., Competing Interests: This event was funded by LINK‐J SCOOP 2019 and ANA Wonder FLY., (© 2020 The Authors. Journal of General and Family Medicine published by John Wiley & Sons Australia, Ltd on behalf of Japan Primary Care Association.)

Gene therapy has been employed as a therapeutic approach for intractable focal epilepsies. Considering the potential of focal GABAergic neuromodulation in regulating epileptogenesis, the GABA-producing enzyme, γ-aminobutyric acid decarboxylase 67 (GAD67), is highly suitable for epilepsy therapy. The EL/Suz (EL) mouse is a model of multifactorial temporal lobe epilepsy. In the present study, we examined focal gene transduction in epileptic EL mice using recombinant adeno-associated virus serotype 8 (rAAV8) expressing human GAD67 to enhance GABA-mediated neural inhibition. Eight-week-old mice were bilaterally injected with rAAV8-GFP or rAAV8-GAD67 in the hippocampal CA3 region. After four weeks, the GAD67-transduced EL mice, but not the rAAV-GFP-treated EL mice, exhibited a significant reduction in seizure generation. The GAD67-mediated depression became stable after 14 weeks. The excitability of the CA3 region was markedly reduced in the GAD67-transduced EL mice, consistent with the results of the Ca 2+ imaging using hippocampal slices. In addition, downregulation of c-Fos expression was observed in GAD67-transduced hippocampi. Our findings showed that rAAV8-GAD67 induced significant changes in the GABAergic system in the EL hippocampus. Thus, rAAV8-mediated GAD67 gene transfer is a promising therapeutic strategy for the treatment of epilepsies.

Purpose: The Synchrony™ Respiratory Tracking System of the CyberKnife ® Robotic Radiosurgery System (Accuray, Inc., Sunnyvale, CA, USA) enables real-time tracking of moving targets such as lung and liver tumors during radiotherapy. Although film measurements have been used for quality assurance of the tracking system, they cannot evaluate the temporal tracking accuracy. We have developed a verification system using a plastic scintillator that can evaluate the temporal accuracy of the CyberKnife Synchrony., Methods: A phantom consisting of a U-shaped plastic frame with three fiducial markers was used. The phantom was moved on a plastic scintillator plate. To identify the phantom position on the recording video in darkness, four pieces of fluorescent tape representing the corners of a 10 cm × 10 cm square around an 8 cm × 8 cm window were attached to the phantom. For a stable respiration model, the phantom was moved with the fourth power of a sinusoidal wave with breathing cycles of 4, 3, and 2 s and an amplitude of 1 cm. To simulate irregular breathing, the respiratory cycle was varied with Gaussian random numbers. A virtual target was generated at the center of the fluorescent markers using the MultiPlan™ treatment planning system. Photon beams were irradiated using a fiducial tracking technique. In a dark room, the fluorescent light of the markers and the scintillation light of the beam position were recorded using a camera. For each video frame, a homography matrix was calculated from the four fluorescent marker positions, and the beam position derived from the scintillation light was corrected. To correct the displacement of the beam position due to oblique irradiation angles and other systematic measurement errors, offset values were derived from measurements with the phantom held stationary., Results: The average SDs of beam position measured without phantom motion were 0.16 and 0.20 mm for lateral and longitudinal directions, respectively. For the stable respiration model, the tracking errors (mean ± SD) were 0.40 ± 0.64 mm, -0.07 ± 0.79 mm, and 0.45 ± 1.14 mm for breathing cycles of 4, 3, and 2 s, respectively. The tracking errors showed significant linear correlation with the phantom velocity. The correlation coefficients were 0.897, 0.913, and 0.957 for breathing cycles of 4, 3, and 2 s, respectively. The unstable respiration model also showed linear correlation between tracking errors and phantom velocity. The probability of tracking error incidents increased with decreasing length of the respiratory cycles. Although the tracking error incidents increased with larger variations in respiratory cycle, the effect on the cumulative probability was insignificant. For a respiratory cycle of 4 s, the maximum tracking error was 1.10 and 1.43 mm at the probability of 10% and 5%, respectively. Large tracking errors were observed when there was phase shift between the tumor and the LED marker., Conclusion: This technique allows evaluation of the motion tracking accuracy of the Synchrony™ system over time by measurement of the photon beam. The velocity of the target and phase shift have significant effects on accuracy., (© 2018 American Association of Physicists in Medicine.)