Objective To investigate the effect of different strand lengths of 125I seeds with the same activity on the dose of different reference points around the seeds.Methods The scanned images were transferred to the three-dimensional treatment planning system(3D-TPS)according to DICOM format.The target volume was delineated at 5 mm and 10 mm above and below the center of the phantom,and a 0.8 mCi seeds strand was simulated.The 1-20 seeds were arranged with an equal spacing of 5 mm(5 mm-100 mm).The 5 mm points above and below the center of the seeds strand were defined as point A and point A',and the 10 mm points above and below the center were defined as point B and point B'.5 mm above and below the edge of the seeds strand on the left side were defined as AL points and AL'points,and 5 mm above and below the edge of the seeds strand on the right side were defined as AR points and AR'points.Similarly,points 10 mm above the above mentioned positions were defined as BL points,BL'points,BR points,BR'points.The average dose symmetry points were measured at AL,AL',AR,and 5 mm,10 mm,15 mm and 20 mm inside AR' of the 45 mm-100 mm seeds strand.The dose at the center was compared with the dose at the end points.The dose at the center point A was compared with the average dose at the symmetry points of 5 mm,10 mm,15 mm and 20 mm inside of the end points AL,AL',AR and AR',and the dose at each point was curve fitting.The correlation between each point and seeds strands of different lengths was analyzed.Results There was a positive correlation between the dose and the length of each point.There was no statistically significant difference between the center point and the end point.There was a statistically significant difference in dosage at points 5 mm and 10 mm inside from point A,while there was no statistically significant difference in dosage at points 15 mm and 20 mm inside from point A.The dose of A,A',B and B' point increased steadily with the increase of seed chain length,and the fitting curves were obtained respectively:y=e(-0.620/x+5.28)(R2=0.992),y=e(-0.640/x+5.34)(R2=0.987),y=e(-0.82/x+4.80)(R2=0.984),y=e(-0.82/x+4.83)(R2=0.9g1).Conclusion The doses at points A,A',B,and B'are positively correlated with seeds strand length and have a high degree of stability.Point A can be used as a reference point for the target area dose of the seeds strand,and point B can be used as a reference point for the dose to critical organs.The dose at other positions is more variable and thus has a certain degree of uncertainty as a reference point for the seeds strand dose.

Objective To investigate the relationship between the absorbed dose and implantation duration at the target area and at the critical organ dose reference points in the application of radioactive 125I seed strands for the treatment of intraluminal tumors.Methods A self-developed 125I seed strand arc template with a 30-degree angle was used to place 10 seeds(each with activity of 1.0mCi)into the template.CT-based DICOM images were transferred to a treatment planning system(TPS)for dose calculation.Absorbed doses at multiple time points(from day 5 to day 90 with a 5-day interval)were measured at following four specific locations:point A'(5 mm inside the arc center),point A(5 mm outside the arc center),point B(10 mm outside the arc center),and point B'(10 mm inside the arc center).The TPS was first used to calculate the expected absorbed doses,followed by actual absorbed dose measurements over the 90-day period.The expected absorbed doses were calculated,and then the actual absorbed doses were calculated.The time-dose relationship of the above points was analyzed,and the curves and equations were obtained.Results The expected absorbed doses at points A',A,B,and B'were 221.36,196.39,115.78,and 136.32 Gy,respectively.The time(x)-dose(y)relationships of all the above points followed a quadratic function relationship in the form of y=c+bx-ax2.Within the time range of 5-90 days,the actual absorbed dose increased with the prolongation of time,and the increase speed showed a pattern of first fast and then slow.The increase in speed was fast within 20 days,than became stable between 20-75 days,and after 75 days the increase in speed became to slow down.Conclusion When using 125I seed strands to treat intraluminal tumors,the actual absorbed dose of the tumor needs to be accurately calculated based on the implantation duration.The actual absorbed dose initially accumulates rapidly and decreases significantly after 75 days.It is recommended to replace the 125I seed strand with a new one after implanting it for approximately 75 days.

Objective To investigate the impact of different 125I seeds strand radian on the dose of different reference points around the seeds.Methods CT scan of self-developed radioactive particle radiation dose measurement phantom was performed,the scanned images were transferred to the three-dimensional treatment planning system(TPS).The target area at the middle level of the model was drawn.The target volume was delineated at 5 mm and 10 mm above and below the center of the phantom.125I seeds strand plans were designed with different radians,with a total length of 8 cm,seed spacing of 0 cm,activity of 0.8 mCi,and a total of 16 particles,with radians ranging from 30°to 170°,increasing by 10° increment.The point 5 mm vertically away from the center of the seeds strand towards the center was named A',and the point away from the center was named A.The point 10 mm vertically away from the center of the seeds strand towards the center was named B',and the point away from the center was named B.The doses at different radians were recorded,and the actual absorbed dose at 1-2 months after operation was calculated based on the particle activity decay formula.Results The doses at points A'and A were(218.3±23.1)and(201.5±16.0)Gy respectively(P=0.001).The actual absorbed doses at 1 month after operation were(65.5±6.9)and(60.5±4.8)Gy respectively(P=0.001),and the actual absorbed doses at 2 months after operation were(109.2±11.5)Gy and(100±7.9)Gy respectively(P=0.001).The doses at points B'and B were(95.9±11.0)Gy and(81.7±4.9)Gy respectively(P＜0.001),and the actual absorbed doses at 1 month after operation were(28.8±3.3)Gy and(24.5±1.5)Gy respectively(P＜0.001).The actual absorbed doses at 2 month after operation were(48.0±5.5)Gy and(41.0±2.4)Gy respectively(P＜0.001).The doses at points A'and A gradually decreased with the increase of the radians,reaching the minimum value at 100 degrees,and then increased gradually,showing a cubic function change.The actual absorbed dose showed the same trend.The doses at points B'and B increased gradually with the increase of the radians,showing a cubic function change.Conclusion At different radians,the point doses and absorbed doses on the centrifugal side of the seeds strand are both less than those on the centripetal side.There is a cubic function relationship between the dose at the reference points and the radian of the seeds strand.

Objective To evaluate efficacy and safety of Iodine-125 seeds used in brachytherapy for cholangiocarcinoma.Methods A total of 65 cases of cholangiocarcinoma patients were diagnosed and treated with ERCP.The Iodine-125 seeds were implanted into bile duct cavity by self-made carrier (applicator) in various ways, and Iodine-125 seeds were replaced to improve the local irradiation dose.Follow-up was regularly made through endoscopy and ultrasonography to evaluate feasibility, efficacy and complications.Results Self-expanding metal stents, single or double plastic stents were successfully placed in 65 patients.At first , single row of Iodine-125 seeds were inserted to 59 patients, double row Iodine-125 were inserted to 6 patients , and the average activity of the first irradiation was 5.775 mCi.Iodine-125 were replaced in 4 patients after three months, in 41 patients after six months, in 5 patients after one year.The total dose was up to 14 mCi.In the follow-up of 6-35 months, the longest survival time was 35 months in two patients, where the Iodine-125 seeds were replaced 3 times as a whole and there was no serious complications.Conclusion Iodine-125 brachytherapy on cholangiocarcinoma by ERCP, where biliary stents and Iodine-125 seeds can be replaced at any time , is convenient, less invasive and can obviously prolong survival time.

Objective To explore the application value of the guide-wire for selective biliary cannulation of proximal biliary obstruction.Methods A total of 344 patients with proximal biliary obstruction were treated by endosocopic retrograde cholangio-pancreatography.Various guide-wire skills,were applied to pass through the stricture of bile duct,so as to reach the target bile duct,and analyzed for their therapeutic effects.Results Selective biliary cannulation of proximal biliary obstruction was completed in 336 patients,after successful cholangiography for therapeutic operation.The overall success rate was 97.67％.There was no procedure-related complications,such as hemobilia or perforation.Conclusion The guide-wire for selective biliary cannulation of proximal biliary obstruction not only improves the success rate of therapeutic endoscopy but also reduces the procedure time and the incidence of complications.

Objective To evaluate the endoscopic precut sphincterotomy for malignant biliary obstruction. Methods Endoscopic precut sphincterotomy was performed in different ways for 46 patients with malignant biliary obstruction and difficult biliary cannulation according to the anatomic structure of the papilla and cannulation. Ways of precut were summarized and complications were analyzed. Results Precut sphincterotomy was performed with bow-like knife in 4 patients, with needle-knife in 24, with trans-pancreatic sphincterotomy in 12 and with combined ways in 6. The procedure succeeded in 35 cases (76. 1%, 35/46). Post-procedure complications included bleeding in 3 patients, pancreatitis in 1, hyper-amylasemia in 2and cholangitis in 1. No perforation was found. Conclusion Endoscopic precut sphincterotomy is not only able to improve the therapeutic endoscopy achievement rate in patients with malignant biliary obstruction, but also to lower the incidence of complications if used adequately.

Objective To study the relationship of pit pattern in the progress of colorectal and the expression of PCNA and survivin in pit pattern. Methods Chromoendoscopy observation results were recorded according to the pit pattern classification proposed by Kudo. These results were divided into 6 groups according to the pit pattern and the results of histophathology. Expression of PCNA and surviving mRNA was detected by RT-PCR. Statistical analysis was performed using χ2 test , Fisher's exact test or Spearman rank correlation with SPSS 12.0 software package. Results In 6 groups classified according to the pit patterns, the expression rate of PCNA mRNA in type Ⅰ, Ⅱ, Ⅲ L, Ⅳ, V 1 and VN were 0% (0/13), 12.5% (1/8), 38.9% (7/18), 66.7% (12/18), 75.0% (3/4) and 100.0% (9/9), the expression rate of survivin mRNA in type Ⅰ,Ⅱ, Ⅲ L, Ⅳ, V 1 and V N were 0%, (0/13), 12.5% (1/8), 22.2% (4/18), 44.4% (8/18), 50.0% (2/4) and 77.8% (7/9), respectively. Conclusions The expression of survivin and PCNA mRNA had positive correlation in the coloree-tal lesions classified whether by the pit patterns or histophathology. Study of the two genes simultaneously could complement each other and reflect the biological characteristics of colorectal cancer more accurately.

Objective To explore the clinical effect of cholangioscopic Holmium laser lithotripsy for bile duct refractory residual stone and orthomorphia for intrahepatic bile duct membranous stenosis. Methods The final diagnosis was established by T tube retrograde cholangiography and cholangioscopy in 12 patients with refractory bile duct residual stone. Twenty-nine stones distribute in extrahepatic and intrahepatic bile duct and 5 intrahepatic bile duct membraneous stenosis were found in 3 cases. All patients underwent Holmium laser lithotripsy and orthomorphia. Results The stone clearance rate was 100% in 12 patients after cholangioscopic holmium laser lithotripsy. No serious complication occurred in patients after 5 membranous stenosis orthomorphia. Follow-up observation on 11 patients shows no obvious recurrence of symptom and stones. Conclusion Holmium laser lithotripsy and orthomorphia are safe and effective in the treatment of bile duct refractory residual stone and stenosis.