Objective To discuss the effect of different particle activities and tumor shrinkage speed on the dosimetric parameters of the target area at the same prescription dose after 125I particle implantation.Methods A 6cm-sized cube tumor model was outlined by using a computerized three-dimensional treatment planning system(3D-TPS)with a prescription dose(PD)of 100 Gy,and 125I particle activities of 0.4 mCi and 0.8 mCi were selected.Assuming that the tumor shrinks centripetally after seed implantation and that the 125I particles were uniformly and centripetally concentrated without shedding or wandering,the tumor volume shrank at different rates every month after implantation(0,5％,10％,15％,20％,25％,30％,35％,40％,45％and 50％),according to the different activities of 125I particles,the experiments were divided into A1-K1 group(0.4 mCi)and A2-K2 group(0.8 mCi).Based on the 125I particle decay law,the validation program(using TPS simulation of the A1-K1 group and A2-K2 group at postoperative 1,2,3,4,5 and 6 months)obtained the dose received by 90％of the target volume(D90)in the two groups with different 125I particle activities at different postoperative time points,the percentages of the target volume covered by the 100％,150％and 90％prescription dose(V100,V150,V90),and the mean dose(Dmean).By comparing the differences in D90,V100,V150,V90 and Dmean after tumor implantation of 125I particles with different activities,the dosimetric impact of the tumor target area shrinking at a rate of 0～50％after implantation of 125I particles with different activities into tumor tissues was analyzed.Results When the monthly shrinkage rate of the tumor target area was≤30％,there was no obvious difference in D90 between the 0.4 mCi group and 0.8 mCi group in 1～6 months after surgery.When the monthly shrinkage rate of the tumor target area was＞30％,the D90 of 0.8 mCi group was higher than that of 0.4 mCi group;when the monthly shrinkage rate of the tumor target area was＜25％,the V90 of 0.4 mCi group was higher than that of 0.8 mCi group,and the changes of V90 of the two groups tended to be the same in the 5th～6th month after surgery.When the monthly shrinkage rate of the tumor target area was ≥30％,the V90 of 0.8 mCi group was higher than that of 0.4 mCi group,and with the increasing of shrinkage rate,the difference between the two groups become more and more significant,the results of V100 were consistent with those of V90.When the monthly shrinkage rate of tumor target area＜35％,V150 of 0.4 mCi group was higher than that of 0.8 mCi group,when the monthly shrinkage rate of tumor target area ≥35％,V150 of 0.8 mCi group was higher than that of 0.4 mCi group,and with the increasing of shrinkage rate,the difference between the two groups become more and more prominent.When the monthly shrinkage rate of tumor target area＜25％,Dmean of 0.4 mCi group was higher than that of 0.8 mCi group,when the monthly shrinkage rate of tumor target area ≥25％,Dmean of 0.8 mCi group was higher than that of 0.4 mCi group,and with the increasing of shrinkage rate,the difference between the two groups become more and more obvious.Conclusion With the same prescription dose,when the tumor target area shrinks at a rate of＜30％per month,the activity of 125I particles has little effect on D90,and all V90,V100,V150 and Dmean in the low activity group are higher than those in the high activity group,meanwhile the homogeneity of the target area is relatively good;when the monthly shrinkage rate of tumor target area ≥35％,all D90,V90,V100,V150 and Dmean in the high activity group are higher than those in the low activity group,and the duration of the presence of high-dose area is long.This difference becomes more obvious with the increasing of the monthly shrinkage rate of the target area.

Objective:To study the differences in the cumulative dose between deformable image registration (DIR) and simple dose-volume histogram (DVH) summation in the fractionated brachytherapy of cervical cancer, and to analyze the feasibility of the application of DIR in the dosimetry assessment of targets and organs-at-risk (OARs) in the brachytherapy.Methods:A retrospective analysis was conducted for 13 cases with primary cervical cancer treated with four fractions of interstitial brachytherapy guided by CT images. The four CT images of each cases were registered using an intensity-based DIR. Then, the cumulative doses (the D2 cm 3, D1 cm 3, and D0.1 cm 3 of the bladder, rectum, intestine, and colon and the D90for targets) after DIR were calculated and compared to those obtained using simple DVH summation. Afterward, the correlation between the dose difference and dice similarity coefficient (DSC) was analyzed. With the dose difference (the remaining dose of OARs caused by the DIR) as limits, a new plan was made for the latest CT to calculate the dose increase to targets. Results:Compared to simple DVH summation, DIR allowed the cumulative doses of the D2 cm 3 and D1 cm 3 of bladder to be decreased by (2.47±1.92) and (2.82±2.73) Gy, respectively on average ( t=-3.65, -2.93, P < 0.05), those of the D2 cm 3, D1 cm 3, and D0.1 cm 3 of rectum to be decreased by (2.05 ± 1.61) Gy, (1.51 ± 1.58), and (3.21 ± 2.50) Gy, respectively on average ( t=-4.02, -3.02, -4.06, P < 0.05), and those of the D2 cm 3, D1 cm 3, and D0.1 cm 3 to be decreased by (1.42 ± 0.99), (1.55 ± 1.28) Gy, and (2.43 ± 1.95) Gy, respectively on average ( t=-3.52, -2.96, -3.06, P < 0.05). There was no significant statistical difference in the D90 of targets, the D0.1 cm 3 of the bladder, and the D2 cm 3, D1 cm 3, D0.1 cm 3 of the colon ( P > 0.05) between both methods, and there was no distinct correlation between DSC and dose difference ( P > 0.05). The DIR increased the dose to targets, with a median value of 150 cGy. However, the accuracy of the DIR should be improved. Conclusions:In clinical practice of multiple fractions of brachytherapy for cervical cancer, it′s still recommended to adopt the simple dose summation method to assess the doses to targets and OARs.

Objective:To establish a dosimetric method based on the well-chamber to verify the accuracy of the source positioning and dwelling time for the afterloading machine, aiming to provide a new method for the quality control of afterloading machine.Methods:The principle of this method was explained according to the hardware structure of the well-chamber. Then, the precision of this method was analyzed by the simulation test and data fitting. The feasibility test was also performed. And the advantages and disadvantages of this method were compared with those of the traditional method.Results:The precision of this method for detecting the source positioning was 0.07 mm and the dwelling time was 0.09 s, respectively. In the feasibility test, the standard deviation of the measure value was below 3%.Conclusions:The well-chamber method has high precision and convenient operation. It can be applied in the rapid verification of the relative accuracy of the source positioning and dwelling time of well-chamber.

Objective: To study the feasibility of using the PTW729 2D array ion-chamber to verify the relative dose distribution calculated with the Acuros BV algorithm. Both advantages and disadvantages of the method were analyzed to provide reference for practical clinical practices. Methods: Based on self-built measurement phantoms, the dose distribution on the same slice of the phantom was measured with PTW729 and film, respectively, under the same measurement condition and plan. The dose distributions obtained by the two method were compared with the result calculated with Acuros BV, separately, by using γ analytical tool. And the stability of the PTW729 was tested. Results: The γ comparison value was 95.9% between the film and Acuros BV, 98.9% between the PTW729 and Acuros BV and 88.0% between the film and PTW729, with 95.0%, 100.0%, and 100.0%, in their stability test respectively. Conclusions PTW729 2D array ion-chamber can be applied to the rapid verification of Acuros BV algorithm-calculated relative dose distribution.

Objective: To compare the clinical application of three-dimensional laparoscopic pancreatoduodenectomy (3D-LPD) with that of two-dimensional laparoscopic pancreatoduodenectomy (2D-LPD), and to explore the safety and feasibility of 3D-LPD. Methods: A retrospective analysis was made from the data of 45 patients with 3D-LPD and 45 patients with 2D-LPD who underwent total laparoscopic pancreatoduodenectomy from March 2017 to August 2018 at Department of Hepato-Pancreato-Biliary Surgery, the First People′s Hospital of Changzhou.The differences of intraoperative conditions, postoperative complications and postoperative pathological findings between the two methods were compared.Measurement data were compared with independent sample t-test, enumeration data were statistically analyzed with Chi-square test or Fisher exact probability. Results: The operation time of 3D-LPD group was shorter than that of 2D-LPD group ((335±95) min vs. (419±113) min, t=-3.817, P=0.000), which mainly showed that the time of digestive tract reconstruction was reduced ((92±26) min vs. (131±46) min, t=-4.951, P=0.000). The intraoperative blood loss in the 3D-LPD group was significantly less than that in the 2D-LPD group ((242±124) ml vs. (350±176) ml, t=-3.365, P=0.001), and the perioperative blood transfusion in the 3D-LPD group was significantly less than that in the 2D-LPD group (χ²=4.444, P=0.035). Postoperative hospitalization days and ICU stay time were not significantly different between the two groups(both P>0.05). Postoperative complications such as pancreatic fistula, biliary fistula, postoperative bleeding, gastric emptying disorders, abdominal infection, were not significantly different between the two groups(all P>0.05). Conclusions The operation time of 3D-LPD is shorter than that of 2D-LPD, and the amount of bleeding is less. Short-term clinical data showed that, 3D-LPD is effective, safe and worth popularizing.

Objective: To study the learning curve of laparoscopic pacreaticoduodenectomy (LPD) with a view to find an appropriate way to develop LPD step by step. Methods: 112 consecutive patients who completely underwent LPD in a single surgery center at the First People’s Hospital of Changzhou from December 2015 to February 2018 were retrospectively reviewed. By using both the cumulative sum (CUSUM) and the risk-adjusted CUSUM (RA-CUSUM) methods to analyze the perioperative data of these patients, the learning curve of LPD was studied in a more scientific way. Results: The learning curve could be divided into three phases: Phase 1, the initial period (the initial 45 patients); Phase 2, the enhancement period (the subsequent 31 patients); Phase 3, the maturation period (the remaining patients). For these 3 phases, the corresponding operative times were (448.4±75.0), (381.3±74.3), and (336.2±52.1) min, respectively (P<0.05). The intraoperative blood losses were (373.3±250.1), (332.3±211.6), and (265.3±253.2) ml, respectively (P<0.05). The times to oral intake were 6.0(5.0, 8.0), 5.0(3.0, 6.0), and 3.0(3.0, 5.0) days, respectively (P<0.05). The number of lymph nodes harvested were (10.0±7.0), (8.8±4.3), and (13.3±6.2), respectively (P<0.05). All these showed significant improvement through the 3 phases. On the other hand, the postoperative stays, the postoperative pancreatic fistula rates were also decreased. But these failed to reach statistical significance. Vascular reconstruction was carried out in the 48th patient in phase 2 of the study. Conclusions The initial phase of LPD passed after LPD for 46 patients, but the maturation phase occurred after LPD on 76 patients. Vascular reconstruction should be considered as passing through the learning phase rather than reaching the maturity phase. Adjustments made in the enhancement phase helped to get through the maturation phase earlier.

Objective To evaluate the safety and efficacy of CT-guided radioactive 125I seed implantation in treating retroperitoneal lymph node metastasis due to recurrent cervical cancer after radiotherapy.Methods A total of 10 patients with retroperitoneal lymph node metastasis (12 lesions in total)due to recurrent cervical cancer after radiotherapy,who were treated with CT-guided 125I seed implantation during the periodfrom November 2011 to October 2015,were included in this study.The diameters,that were perpendicular to each other,of the involved lymph nodesranged from 1.7 cm×1 cm to 6.5 cm×5 cm,the diameter of 6 involved lymph nodes (50％) was ＜5.0 cm and the diameter of other 6 involved lymph nodes (50％) was ≥5.0 cm.With the help of treatment planning system for brachytherapy,the source distribution was formulated.Under CT guidance,the 125l seedswith the activity of 0.3-0.7 mCi were implanted.Postoperative validation showed that D90 (90％ minimum prescription dose received by the target volume) was 36-110 Gy (median 59 Gy).After the treatment,the changes in lesion size,pain relief and complications were recorded.Results The 10 patients were followed up for 4.3-16.1 months,the median follow-up time was 9.7 months.The 2-month local control rate and the 2-month effective rate were 100％ and 58.3％,respectively.The 2-month,6-month and 12-month survival rates were 100％,66.7％ and 58.3％,respectively.The median survival time was 12.1 months.One patient (10％) died of gastrointestinal bleeding at five months after treatment,six patients (60％) died of distant metastases,three patients (30％) survived withno evidence of local recurrence.No major complications such as massive hemorrhage,intestinal infection,bone marrow suppression or other 125I seed-related complications occurred.Conclusion For the treatment of retroperitoneal lymph node metastasis due to recurrent cervical cancer after radiotherapy,CT-guided radioactive 125I seed implantation has satisfactory short-term curative effect,and this technique is safe and feasible.

Objective To study the dosimetric effect of two source patterns, including equal spacing and peripheral dense intermediate sparse by assuming a tumor shrinking speed of 20%per month after 125 I seed implantation. Methods A virtual cylindrical tumor with 4 cm in height and 5 cm in diameter was contoured on a three-dimensional treatment planning system ( TPS ) . Two groups of preoperative plans were made with 1. 85 × 107 Bq 125 I seeds using two source patterns respectively. It was assumed that the tumor height was unchanged, while the diameter of tumor would decrease at a speed of 20%per month, and the locations of seeds would concentrate towards the tumor core. The 90%target volume dose ( D90 ) , the ratio of 90%isodose volume over the target volume ( V90 ) , and the ratio of 150%isodose volume over the target volume (V150) were calculated at 0, 1, 2, 3 months after 125I implantation respectively. Results In equal spacing group, 85 seeds were implanted. The values of D90 were 126. 20, 130. 41, 133. 82 and 139. 48 Gy after 0, 1, 2 and 3 months respectively. The values of V90 were 97. 0%, 98. 1%, 99. 3%and 100%, while those of V150 were 70. 2%, 69. 9%, 71. 1% and 71. 5%. The dense in-periphery and sparse-in the middle group was loaded with 75 seeds. The D90 values were 126. 46, 125. 41, 123. 50 and 128. 83 Gy, the V9095. 2%, 95. 7%, 94. 9%and 97. 6%, and the V15052. 8%, 60. 4%, 62. 7%and 59. 3%after 0, 1, 2 and 3 months, respectiviely. Conclusions When the tumor diameter reduces at a rate of 20%per month after 125 I seed implantation, the expected tumor dose absorption will gradually increase using the equal spacing sources pattern. However, the expected dose does not vary withsource distribution of dense-in the-surrounding and sparse-in-middle, which also reduces high dose volume more than the equal spacing pattern.

As a standard method for early stage prostate cancer, 125Ⅰ seed implantations are used widely in America. Although there are guidelines from American Brachytherapy Society and American Association of Physicists in Medicine, some hospitals still cannot implant the seeds properly according to the guidelines. Complications were observed inevitably. The medical events about seeds implantation in America from 2002 were investigated and the reasons were analyzed in this paper. Additionally, some solutions were given to avoid the medical events, so that the practitioners in China can learn from it and make sure the 125Ⅰ seeds implantation can be developed healthily and smoothly.