Objective To investigate the surrounding and central dosimetric distribution difference of the same activity, same number of 125I seeds. Methods 3D treatment planning system (3D-TPS) was used to separately sketch out 7 cubes with side length of 2 cm, 2.5 cm, 3 cm, 3.5 cm, 4 cm, 4.5 cm and 5 cm;simulations of different tumor sizes were established, into which 125I seeds with activity of 0.5 mCi were respectively loaded. All seeds were distributed at the periphery of the tumor (peripheral group) with the prescribed dose of 145 Gy. The dose volume histogram (DVH) was printed and the 90% of target volume absorbed dose (D90), 90% of prescription dose coverage target volume percentage (V90), the maximum dose and mean dose were determined. Then the seeds in every cube were distributed into the center (central group) and the above parameters were calculated by using the same method. Results The mean D90 of the peripheral and central group was (147.29 ±0.58) Gy and (106.08 ±9.40) Gy respectively, the difference between the two groups was statistically significant (t=-4.292, P=0.005). The mean V90 of the peripheral and central group was (95.46±0.44)% and (79.07±4.19)% respectively, the difference between the two groups was statistically significant (t=-3.831, P=0.009). The mean maximum dose of the peripheral and central group was (1 224.65 ±12.7) Gy and (1 532.48 ±48.54) Gy respectively, the difference between the two groups was statistically significant (t=6.823, P=0.000). The mean value of average dose of the peripheral and central group was (192.14 ±2.89) Gy and (179.81 ±5.40) Gy respectively, the difference between the two groups was statistically significant (t=-2.847, P=0.029). Conclusion The dose distribution is directly influenced by the distribution pattern of the 125I seeds. When the number and activity of the 125I seeds are the same, the peripheral seeds implantation has a better dose distribution.

Objective To study the dose distribution in tumor target of radioactive esophageal stent covered with 125I seeds which are arranged at different distance. Methods According to the longitudinal and horizontal distance between the 125I seeds, the experiment was divided into group A (0.5 cm), group B (1.0 cm) and group C (1.5 cm). A sheet of white paper, on which a 2cm diameter circle was drawn and was marked with a 5 cm scale, was scanned with a laser scanner, and the scanning data were saved in JPEG format on the computer desktop. By using image conversion program, pictures of 17 layers with the layer space of 5 mm were created. The picture was transmitted to the computer treatment planning system (TPS) to simulate a 2 cm diameter and 8 cm length esophageal stent. Using TPS to delineate the tumor target area (gross tumor volume, GTV), which was used as the simulation of the inner boundary of the tumor target area, outward expansion of 0.5 cm being regarded as the outside border. An annular and 6cm length tube was delineated and it was used as the target area, and the same prescription dose was set, and in each group 125I seeds of 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9 mCi were successively loaded on the simulation of esophageal stent. With the help of TPS the DVH graph was obtained, and the D90 (the dose received by 90% of the target) and V90 (the percentage of the GTV receiving 90% the prescription dose) of the three groups were determined. The results were statistically analyzed. Results The arithmetic mean values of D90 of group A, B and C were (217.15± 19.92), (89.16±32.44) and (31.68±11.52) Gy respectively (F=159.18, P<0.05); and the arithmetic mean values of V90 of group A, B and C were (100.00±0.00)%, (86.47±21.36)%and (29.33±21.54)%respectively (F=32.11, P<0.05). Conclusion The 2 cm-diameter radioactive esophageal stent covered with 125I seeds, which have o.6mci activity and are arranged at 1.0cm distance in both longitudinal and horizontal directions, should be recommended in clinical practice.

Objective To explore the clinical efficacy of CT-Guided radioactive 125I seed implantation in treating retroperitoneal lymph node metastases. Methods Eighteen patients with retroperitoneal lymph node metastases (20 lesions in total) received CT-guided radioactive 125I seed implantation. Treatment planning system (TPS) was used to formulate the therapeutic protocol. The radioactive activity of 125I particle ranged from 1.11 × 107-2.96 × 107 Bq (0.3-0.8 mCi) and the matched peripheral dose (MPD) was 60 -100 Gy. Postoperative dosimetry was routinely performed for all the patients in one week. Postoperative D90 (90%dose received by target volume) was 53 -107 Gy. The patient’s clinical benefit response (CBR), two-month local tumor control rate and one-year survival rate were evaluated, and the complications were recorded. Results All the patients were followed up for 2 -15 months with a median time of 5 months. The one-year survival rate was 22.2%. The clinical benefit rate, overall effective rate and two-month local tumor control rate were 72.2%, 70.0% and 90.0% respectively. No serious complications occurred in all patients. Conclusion For the treatment of retroperitoneal lymph node metastases, CT-guided radioactive 125I seed implantation is mini-invasive with satisfactory short-term effect and fewer complications. Therefore, this technique is a relatively safe therapeutic means.

Objective To discuss the commonly used puncturing approaches in CT-guided 125I seed implantation for lumbar lymph node metastases in order to provide safe and reliable technical guidance for clinical practice.Methods Under CT guidance,125I seed implantation for lumbar lymph node metastases was performed.According to different locations of metastatic lymphadenopathy (left waist,right waist or middle waist),the corresponding puncture route and implantation method were adopted.Meanwhile,different puncturing approach was designed in order to avoid damage to vital organs.Results For the performance of 125I seed implantation for the lymphadenopathy located at the left waist,right waist and middle waist,the commonly used puncturing approaches were percutaneous transthoracic lumboiliac costal muscle method (i.e.back approach),trans-hepatic trans-duodenal method (i.e.lateral approach) or back approach method,and trans-mesenteric approach together with coaxial needle method (i.e.anterior approach) respectively.Conclusion It is clinically feasible to use different puncturing approaches in performing 125I seed implantation for lumbar lymph node metastases,the suitable puncturing approach can ensure a successful and safe operation.

Objective To investigate the dose distribution of esophageal stents carrying different diameters of radioactive 125I seeds in tumor target area. Methods A laser scanner was used to scan a piece of blank paper on which circles of 12 mm, 14 mm and 16 mm diameter and a 5 cm scale were drawn. The data were stored in JPEF format on the computer desktop. According to the circular diameter, simulations of the corresponding esophageal stents were established, which were divided into group A, group B and group C. By using image conversion program, 17 images with 5 mm slice-distance were created for each group; the images were transmitted to the computer treatment planning system (TPS) to simulate the 8 cm long esophageal stents of different diameters. TPS was used to sketch the gross tumor volume (GTV) in order to simulate the esophageal stent border that was used as the inner boundary of GTV, which was expanded 0.5 cm outward to be used as the external boundary of GTV. Beginning from the fifth level, the 4 cm-long GTV was drawn with circles. Setting the same prescription dose, from the fifth level to the thirteenth level the 125I seeds with 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9 mCi were successively loaded on the simulation of the esophageal stents. The distance between 125I seed layers was 1 cm; the average number of seeds distributed on each layer was 4 particles. The dose volume histogram (DVH) was obtained. The D90 (the dose received by 90% of the target) and V90 (the percentage of the GTV volume receiving 90% the prescription dose) were recorded.Result s The arithmetic mean D90 of group A, B and C was (77.24 ±19.92) Gy, (69.56 ±25.27) Gy and (56.38±20.08) Gy respectively, and no statistically significant differences existed between each other among the three groups (F=0.84,P=0.44). The V90 of group A, B and C was (77.76±30.73)%,(76.79±25.92)%and (64.10 ±32.49)% respectively, and no statistically significant differences existed between each other among the three groups (F=0.46,P=0.64). Conclusion When the diameter of radioactive esophageal stent is 12 mm, the activity of 125I seed of 0.6 mCi is recommended. When the diameter of radioactive esophageal stent is 14 mm or 16 mm, the activity of 125I seed of 0.7 mCi is recommended. Nevertheless, when the diameter of radioactive esophageal stent is 16 mm, distribution of every five 125I seeds on each layer is strongly recommended. These three kinds of esophageal stent diameter have no significant effect on the dosimetric parameters.

Objective To investigate the safety and feasibility of different puncturing approaches in the performance of CT-guided 125I seed implantation for the treatment of retroperitoneal malignant tumors. Methods The clinical data of twenty-five patients with retroperitoneal malignant tumors, who had underwent CT-guided 125I seed implantation, were retrospectively analyzed. The puncturing approaches included trans-hepatic route, trans-gastric route, trans-duodenal route, and through mesentery and through thoracolumbar iliocostalis. The malignant tumors included retroperitoneal lymph node metastases (n=21) and pancreatic cancer (n=4). Preoperative full bowel preparation was carried out in all patients, and treatment planning was formulated by using treatment planning system (TPS) before the procedure. Under CT guidance, proper puncturing approach was selected according to lesion's location. One to 3 needles were used to implant 125I seeds. Immediately after 125I seed implantation, CT scanning was performed to check the distribution of 125I seeds. Results CT-guided 125I seed implantation was successfully completed in all patients. The puncturing approaches used in this series included trans-hepatic route (n=21), trans-gastric route (n=9), trans-duodenal route (n=2), through mesentery (n=2) and through thoracolumbar iliocostalis (n=5). After the operation, no procedure-related complications such as bleeding, peritonitis, hematemesis or melena occurred in all patients. The postoperative 125I particle number, total activity and peripheral dose (D90) were not significantly different from the preoperative data. Conclusion The use of the five puncturing approaches mentioned above is clinically safe and feasible. Strict perioperative management measures should be carefully executed when through cavity organ implantation is employed.

Objective To discuss the feasibility, efficacy and complications of CT-guided 125I seed implantation for the treatment of lymph node metastasis nearby the iliac vessels.Methods The clinical data of twelve patients with para-iliac vessel lymph node metastasis, who had been treated with CT-guided 125I seed implantation, were retrospectively analyzed. A total of 12 lesions were detected; the diameter ≤6 cm was seen in seven lesions, and the diameter >6 cm was seen in five lesions. Using computer treatment planning system, the source distribution was calculated. Under CT guidance 125I seeds with the activity of 0.4-0.7 mci were implanted into the metastatic lymph nodes with a seed interval of 0.5-1.0 cm. CT scan was performed immediately after implantation to check the distribution of seeds as well as the possible complications. After the treatment, D90 (90%prescription dose received by target volume) was ≥75 Gy in 6 patients and <75 Gy in other 6 patients. Two months after the treatment CT reexamination was employed, and imaging evaluation was conducted according to WHO Response Evaluation Criteria in Solid Tumors. Results CT-guided 125I seed implantation was successfully accomplished in all 12 patients. Two months after the treatment, the evaluation of the therapeutic effect showed that complete remission (CR) was obtained in 0 patient, partial remission (PR) in 8 patients, stable disease in 3 patients and progress disease in one patient;and the total effect rate(CR+PR) was 66.7%. The local control rate was 91.7%. In eight patients the pain that was caused by metastatic lymph nodes was significantly relieved within 1-14 days after 125I implantation treatment. Before the treatment three patients had lower limb edema, and in two of them the lower limb edema was obviously relieved within 1-14 days after the treatment. All patients were followed up for 3-39 months, and the median follow-up time was 11 months. One-year survival rate was 41.7%. No severe complications such as massive hemorrhage, infection, myelosuppression or seed displacement occurred. Conclusion For the treatment of para-iliac vessel lymph node metastasis, CT-guided 125I seed implantation is safe and feasible. Better curative effect may be achieved when the diameter of the metastatic lymph node is<6 cm and the peripheral radiation dose is>75 Gy.

Objective To investigate the safety and effectiveness of radioactive 125I seed implantation in treating recurrent cervical lymphatic metastases after radiotherapy. Methods During the period from Aug. 2011 to July 2012, 17 patients with recurrent cervical lymphatic metastases who had received radiotherapy before were admitted to authors’ hospital. The clinical data were retrospectively analyzed. A total of 23 metastatic lymph nodes were detected in the 17 patients. Brachytherapy treatment planning system (TPS) was used to formulate the number, activity and distribution of radioactive 125I seeds. The radioactive activity was 0.3 - 0.8 mCi (1.30 × 107- 2.96 × 107 Bq), and the matched peripheral dose (MPD) was 60 - 120 Gy. Guided by ultrasound and CT radioactive 125I seeds were implanted under local anesthesia. CT scanning was performed within 24 hours after the procedure. Postoperative D90 was (81.4 ± 2.1) Gy. CT examination was employed every two months to determine the tumor size and to record the complications. Results All patients were followed up for 6 months. The 6-month local control rate was 65.2%. The control rates (CR+PR) for<4 cm (n=10) and>4 cm (n=13) lymph nodes were 90%and 46%respectively, the difference between the two was statistically significant (P = 0.038). No significant difference existed between the control rate (CR + PR) and the un-control rate (SD + PD) for each lymph node group at cervical Ⅰ, Ⅱ, Ⅲ and Ⅴ grade Ⅱ was seen in 8 cases and grade Ⅰ in 7 cases. No severe complications occurred. Conclusion For the treatment of recurrent cervical lymphatic metastases after radiotherapy, radioactive 125I seed implantation is effective and mini-invasive with fewer complications. This technique is more suitable for < 4 cm solitary metastatic lymph node with clear border.

Objective To study the effective dose and precaution time of the irradiation of the close contact from the radiators who underwent implantation of radioactive 125Ⅰ seeds so as to guide scientifically people how to avoid radiation damage.Methods Twenty patients with different types of cancer underwent implantation of radioactive 125Ⅰ seeds with the median value of implantation depth of 2.16 cm.Within 24hs after the operations the dose rates 30 cm and 100 cm from the skin were measured with pocket-size radiometer so as to imitate the situations of the close contacts.The effective doses and precaution times of different persons were calculated according to relevant formula.Results The dose rate a person received at the same time points (1,54,78,and 109 d,respectively) decreased along with the increase of the distance from the skin (t =5.962,5.961,5.961,5.962,P ＜ 0.05).and the dose rate a person received at the same distance from the skin decreased along with the extension of time (30 cm:t =6.236,6.236,6.235,P＜0.05;100 cm:t=7.310,7.315,7.314,P＜0.05).At different time points,the dose rates at 30 cm distance point were all significant higher than those at the 100 cm point (P ＜0.05).The adult living together,minors and pregnant women sharing the room,colleagues,adults who slept together with the patients began to reach the 50％ dose constraint values 0,54,78 and 109 days after the operation.Conclusions After their precaution time,it's safe to contact with the patients for the groups;otherwise,it's necessary to take some protect works within the precaution time.