|Year : 2016 | Volume
| Issue : 7 | Page : 159-165
Dosimetry study of three-dimensional print template-guided precision 125I seed implantation
Zhang Hongtao, Di Xuemin, Yu Huimin, Wang Zeyang, Zhang Lijuan, Zhao Jinxin, Liu Zezhou, Sui Aixia, Wang Juan
Department of Oncology, The Hebei General Hospital, Shijiazhuang 050051, China
|Date of Web Publication||21-Feb-2017|
Department of Oncology, The Hebei General Hospital, Shijiazhuang 050051
Source of Support: None, Conflict of Interest: None
Objective: This study aimed to compare the dose difference in 125 I seed implantation between three-dimensional (3D) print template-guided operation and traditional implantation.
Materials and Methods: This study retrospectively analyzed 27 patients who underwent 125I seed implantation from August 2015 to December 2015 in Hebei General Hospital. Of these, 13 underwent seed implantation guided by a 3D print template, named the template group, and 14 underwent traditional implantation, named the traditional group. All patients underwent computed tomography (CT) scan. Then, 3D templates were printed in the template group. The implantation was guided by CT and 3D templates. The patients in the traditional group underwent implantation with free hands guided by CT scan. Postplan was performed after the operation. The dose-volume histogram, D90, and V90 were calculated. The D90 values pre- and post-operation were compared in each group. The postoperation V90 values of the two groups were also compared.
Results: The mean D90 values pre- and post-operation in the template group were (87.09 ± 33.63) Gy and (85.31 ± 34.40) Gy, respectively, with no statistically significant difference. The mean D90 values pre- and post-operation in the traditional group were (86.04 ± 29.93) Gy and (74.96 ± 46.10) Gy, respectively, with a statistically significant difference. The mean V90 values postoperation in the template and traditional groups were (92.76% ± 1.89%) and (84.59% ± 7.56%), respectively, with a statistically significant difference.
Conclusions: The postplan and preplan dose parameters of 3D print template-guided seed implantation were nearly consistent. The dose parameters of template group superior to the traditional group. The seeds can be implanted accurately with 3D print template.
Keywords: Brachytherapy, iodine isotopes, radiation dosage, radiotherapy planning, stereotaxic techniques
|How to cite this article:|
Hongtao Z, Xuemin D, Huimin Y, Zeyang W, Lijuan Z, Jinxin Z, Zezhou L, Aixia S, Juan W. Dosimetry study of three-dimensional print template-guided precision 125I seed implantation. J Can Res Ther 2016;12, Suppl S3:159-65
|How to cite this URL:|
Hongtao Z, Xuemin D, Huimin Y, Zeyang W, Lijuan Z, Jinxin Z, Zezhou L, Aixia S, Juan W. Dosimetry study of three-dimensional print template-guided precision 125I seed implantation. J Can Res Ther [serial online] 2016 [cited 2021 Sep 21];12:159-65. Available from: https://www.cancerjournal.net/text.asp?2016/12/7/159/200607
| > Introduction|| |
Prostate cancer brachytherapy is used extensively because of the standard transrectal ultrasound – and template-guided procedures., The dose for prostate can reach the prescribed dose (PD) using pre- and intra-operative plans. Because of the high consistency between pre- and post-operative doses, the technique was accepted in the America. Seed implantation was used in China for the following tumors: head and neck, thorax, abdomen, and pelvic cavity.,,,,, However, no standard procedure was available. Seeds were implanted just by experience, preplan could not be carried out, and the dose and seed location were not the same according to the preplan, thereby leading to tumor recurrence and complications. Since the curative effect was not good, the technique was not extensively used. Three-dimensional (3D) print template-guided seed implantation could puncture the tumor accurately according to the preplan in an arbitrary direction and at the same time, avoid harming the blood vessels and bones. The error was significantly reduced, and the dose distribution was much better. However, it was still not known whether the dose accuracy differed from that of the traditional implantation. Hence, this study was conducted to compare the dose difference in 125 I seed implantation between 3D print template-guided operation and traditional implantation.
| > Materials and Methods|| |
This study was approved by the Ethics Committee of the Hebei General Hospital. All patients provided informed written consent.
From January 2015 to December 2015, 27 patients underwent 125 I brachytherapy. The characteristics of the patients are summarized in [Table 1]. The patients included 21 men and 6 women (mean age 59 years; range, 41–92 years). All patients were diagnosed and pathologically confirmed with cancer. The inclusion criteria for 125 I brachytherapy were as follows: (a) No main organ dysfunction and metastasis, (b) the Eastern cooperative oncology group score <2, and (c) no obvious abnormality in blood examination. Patients who had severe dysfunction of organs, coagulation disorders, acute and chronic infection, and psychiatric history were excluded from the study.
|Table 1: Treatment characteristics before 125I seeds implantation (n=20)|
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Radioactive 125 I seeds (Shanghai Xinke Pharmaceutical Company, Shanghai, China; model 6711-99) was shaped as a cylindrical titanium package body with length 4.5 mm, diameter 0.8 mm (activity: 0.3–0.6 mCi; average energy: 27–35 keV; half-life: 59.4 days; half layer: 0.025 mm of lead; initial dose rate 7 cGy/h) and 0.05-mm wall thickness of titanium in its external shell.
All patients were divided into two groups: traditional group and 3D template group. Before 125 I seed implantation, the patients were immobilized using a vacuum cushion (size: 120 cm × 80 cm × 4 cm; Tianchen Medical Instruments, China). A line was drawn according to a computed tomography (CT) laser on the tumor projection surface of the patient skin, and two marks were posted 3–4 cm away on this position line. CT scan was performed with a slice thickness of 5 mm. A treatment plan was made for each patient using a treatment planning system (TPS) (Panther Brachy v5.0 TPS, Prowess Inc., USA) to determine the number, dose, and location of the radioactive seeds implanted [Figure 1]. The target volume was delineated carefully according to the CT findings. Based on the volume of the tumor and a PD of 35–150 Gy, TPS generated a dose-volume histogram (DVH) [Figure 2]. Clinical target volume (CTV) is defined as a 5-mm expansion external to the gross tumor volume. The CTV edge was covered by an isodose line of 90% PD. The entry site and path of the needle were determined to avoid vital structures such as bone and large vessels. The dose for organs at risk was set below the tolerance dose. In the 3D print template-guided group, reconstructed patient skin contour, needle coordinates, and puncture holes in TPS and a 3D printing output file was generated. Stereolithography-600 3D printer was used to print the 3D template [Figure 3]. One day before the operation, the 3D printing template was sterilized. A radioactivity meter (RM-905a well-type ionization chamber, National Institute of Metrology, China) was used to measure seed activity and spot check 10% of the seeds.
|Figure 1: Preplan made by treatment planning system to determine the number, dose, and location of the radioactive seeds implanted|
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|Figure 2: Dose-volume histogram calculated by treatment planning system in preplan|
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In the 3D print template-guided group, a vacuum cushion was used to fix the patients. The disinfected 3D template was fixed according to the marks on the body surface. CT scan was performed to confirm 3D template location. Then, the tumors were punctured after local anesthesia guided by the 3D print template [Figure 4]. A Mick 200-TPV Needle Applicator (Mick Radionuclear Instruments, Inc., NY, USA) was used to implant the seeds according to the preplan. Every seed was placed at a distance of 0.5–1 cm from each other. The seeds were implanted into the tumor guided by CT according to the preplan in the traditional group.
|Figure 4: Punctured the tumor guided by the three-dimensional print template|
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Right after the brachytherapy, a CT scan was performed to verify the position and intensity of seeds. Postplan was performed, and D90, V90, and DVH were calculated [Figure 5] and [Figure 6]. The difference in pre- and post-operation D90 values was observed in each group. The difference in postoperation V90 values between the two groups was also observed.
|Figure 5: Postplan made by treatment planning system and the isodose line distribution|
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|Figure 6: Dose-volume histogram calculated by treatment planning system in postplan|
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The SPSS version 13.0 statistical software (SPSS, IL, USA) was used for data analysis. The independent-samples t-test and Wilcoxon test were used to analyze the statistical difference in pre- and post-operation D90 values and the difference in postoperation V90 values between the two groups, respectively. P < 0.05 was considered statistically significant.
| > Results|| |
In the 3D template group, 12 patients underwent 3D print template-guided seed implantation successfully. One patient underwent CT-guided brachytherapy because of the shifting of mediastinum caused by pneumothorax. In the traditional group, all 14 patients underwent CT-guided brachytherapy successfully. The pre- and post-operation D90 values of the two groups are summarized in [Table 2]. The postoperation V90 values of the two groups are summarized in [Table 3].
| > Discussion|| |
Brachytherapy is a standard treatment for early-stage prostate cancer according to the NCCN guideline.,,, In China,125 I brachytherapy has been widely applied for tumors formed in all parts of the body. Except for prostate cancer, no standard method is available to treat other tumors. Hence, the pre- and post-operation locations of the seeds are not the same, the dose in tumors is out of control, and the effect varies.,,,,, Bin  implanted seeds into lung cancer guided by CT and template. The satisfaction rates of template-guided brachytherapy and traditional brachytherapy were 92% and 39%, respectively (P = 0.003). It showed that seed implantation guided by template could increase postoperation dose satisfaction rate significantly. However, it was just the parallel needle template-guided puncture. The data about the difference in dose accuracy between 3D print template-guided seed implantation and traditional brachytherapy were not available.
This study showed that 3D print template-guided seed implantation could decrease the dose error significantly compared with traditional brachytherapy. In the traditional group, the preplan D90 was nearly 11 Gy larger than the postplan D90. However, the error was only 2 Gy in the 3D template group. The difference between the two groups was obvious. In addition, the postplan V90 value of the 3D template group was higher than that of the traditional group. It was difficult to implant the seeds accurately into the tumor according to the preplan just guided by the CT scan. It depended on the doctor's skill and experience, and the error among different doctors was large. The error in seed location led to a dose error, which resulted in the difference in efficacy and complications. The error in seed location affected the peripheral dose significantly. When the error in seed location was 5 mm, the variation in D90 value was <5%. An error in seed location of 5 mm could lead to an average decrease in V90 values by 10%. When the error in seed location reached 10 mm, the average variation in D90 values was 33 Gy. Thus, it indicated that the error in seed location can influence the target dose significantly. A study on prostate cancer by Stock showed that the 4-year freedom from biochemical failure rate for patients with D90 values <100 Gy, 100–119.9 Gy, 120–13.9 Gy, 140–159.9 Gy, and ≥ 160 Gy was 53, 82, 80, 95, and 89%, respectively. When D90 was <120 Gy, a small error in dose could lead to a big difference in efficacy. Hence, the accuracy of seed location and dose decided the success of implantation. In this study, the difference in pre- and post-plan D90 values of some cases was more than 30 Gy, which would lead to tumor recurrence and complications. 3D print template-guided brachytherapy could implant seeds into the tumor accurately. The dose distribution was much better than that in traditional brachytherapy. The findings suggested that 3D print template-guided brachytherapy might be used widely as a standard procedure in the future.
The 3D print template has many advantages, but a dose error exists. When the distance between the skin and the tumor is too long, the needle position shifts and leads to a dose error. To avoid this, an intraoperative plan should be used after all the needles are punctured. The seed location and number should be adjusted on the actual needle image to let the dose distribution be consistent with the preplan. In addition, once the tumor shift in the operation, the directions of the needle in the template cannot be adjusted and then the template cannot be used. Hence, the patients should be selected carefully before the operation to avoid failure procedure.
| > Conclusion|| |
For the tumors fixed and not far from the skin surface, 3D print template-guided brachytherapy can be performed easily and may be better than implanted seeds with the traditional method. The dose after the operation can be controlled accurately. The postplan data were consistent with the preplan data. However, since the organs have a big degree of motion, the use of the 3D template still has some limitations.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3]