Objective To explore the radiation shielding optimization plan for a medical proton cyclotron developing and commissioning building at various commissioning stages. Methods According to the maximum source termsat different commissioning stages, we used the empirical formula to estimate the instantaneous dose rate at the point of interest outside the shield of the building, and optimized the building’s shielding ateach commissioning stage. Results When adding 1.0 m mobile concrete shielding blocks (“blocks” below) each to wall 3 and wall 4 at the cyclotron commissioning stage, 1.0 m blocks to wall 4 and 1.25 m blocks to wall 5 at the beam transport line commissioning stage, and 1.0 m blocks to wall 9 and 0.4 m blocks to the ceiling at the simulated treatment room commissioning stage, the dose rates at the points of interest outside the shield could meet the dose rate limit requirements. Conclusion The application of mobile concrete shielding blocks not only meets the shielding requirements, but also has economical and space-saving advantages, conforming to the principle of shielding optimization. This can be an approach to the optimization of radiation shielding for high-energy particle accelerators or similar scientific projects.

BACKGROUNDEndoscopic submucosal dissection of the esophagogastric junction is the most difficult gastric and esophageal dissection procedure. No reports of endoscopic submucosal dissection for Siewert type II carcinoma of the esophagogastric junction have compared the outcomes of endoscopic submucosal dissection for all three Siewert types of adenocarcinoma. This study aimed to evaluate the efficacy and safety of endoscopic submucosal dissection for intraepithelial neoplasia of the esophagogastric junction.

METHODSFrom October 2008 to June 2013, 73 patients underwent endoscopic submucosal dissection for intraepithelial neoplasia of the esophagogastric junction. The patients were prospectively evaluated regarding the executability of the technique, short-term results of the procedure, en bloc resection rate, curative resection rate, complications and additional treatment after endoscopic submucosal dissection, and follow-up outcomes.

RESULTSSixty-eight of the 73 patients (93.2%) underwent en bloc resection; the mean maximum specimen diameter was 33.7 mm. Fifty-seven of 61 patients (93.4%) who underwent curative resection were successfully followed-up for 1.0 to 56.0 months (average, 24.1 months). Local recurrence developed in one patient with high-grade intraepithelial neoplasm. Twelve patients underwent noncurative resection, including lateral resection margin residues in three, vertical resection margin residues in one, signet ring cell carcinoma or undifferentiated adenocarcinoma in four, lymphatic or vessel invasion in one, vertical residual margin residues combined with signet ring cell carcinoma in one, and undifferentiated adenocarcinoma with lymphatic or vessel invasion in two. In the noncurative resection group, one patient was lost to follow-up, seven underwent additional surgery, and the remaining four were periodically followed up; none had local recurrence or distant metastases. The only complication was delayed bleeding in three patients, which was successfully controlled by conservative treatment or endoscopic therapy.

CONCLUSIONSEndoscopic submucosal dissection is safe and effective for intraepithelial neoplasia of the esophagogastric junction. R0 en bloc resection is possible and can avoid the risk of local recurrence.

Adult ; Aged ; Aged, 80 and over ; Carcinoma in Situ ; surgery ; Dissection ; adverse effects ; methods ; Esophageal Neoplasms ; surgery ; Esophagogastric Junction ; surgery ; Female ; Gastric Mucosa ; surgery ; Humans ; Male ; Middle Aged ; Prospective Studies