Heterogeneous physical phantom for I-125 dose measurements and dose-to-medium determination

PURPOSE

In this paper we present a further step in the implementation of a physical phantom designed to generate sets of "true" independent reference data as requested by TG-186, intending to address and mitigate the scarcity of experimental studies on brachytherapy (BT) validation in heterogeneous media. To achieve this, we incorporated well-known heterogeneous materials into the phantom in order to perform measurements of 125I dose distribution. The work aims to experimentally validate Monte Carlo (MC) calculations based on MBDCA and determine the conversion factors from LiF response to absorbed dose in different media, using cavity theory.

METHODS AND MATERIALS

The physical phantom was adjusted to incorporate tissue equivalent materials, such as: adipose tissue, bone, breast and lung with varying thickness. MC calculations were performed using MCNP6.2 code to calculate the absorbed dose in the LiF and the dose conversion factors (DCF).

RESULTS

The proposed heterogeneous phantom associated with the experimental procedure carried out in this work yielded accurate dose data that enabled the conversion of the LiF responses into absorbed dose to medium. The results showed a maximum uncertainty of 6.92 % (k = 1), which may be considered excellent for dosimetry with low-energy BT sources.

CONCLUSIONS

The presented heterogeneous phantom achieves the required precision in dose evaluations due to its easy reproducibility in the experimental setup. The obtained results support the dose conversion methodology for all evaluated media. The experimental validation of the DCF in different media holds great significance for clinical procedures, as it can be applied to other tissues, including water, which remains a widely utilized reference medium in clinical practice.

Comparison of intraluminal brachytherapy combined with and without stent placement for treatment of obstructive jaundice induced by tumor thrombus

PURPOSE

To compare the safety and efficacy of intraluminal brachytherapy with iodine-125 (125I) seed strand implantation combined with and without stent placement to treat patients with obstructive jaundice induced by tumor thrombus.

METHODS

Between January 2018 and June 2022, 42 patients with malignant obstructive jaundice (MOJ) induced by tumor thrombus were included. 20 patients received 125I seed strand implantation and stent placement (group A). The remaining 22 patients, implanted 125I seed strands only, served as control (group B). The two groups' overall survival and jaundice-free survival were compared using the Kaplan-Meier method and log-rank test.

RESULTS

During the follow-up period, the mean survival time of group A was 38.0 ± 4.1 months (95%CI, 30.0-46.1 months), while that of group B was 25.1 ± 2.8 (95% CI, 19.5-30.6 months) (p = 0.406). The mean survival rates of 12 months for all patients, group A, and group B was 66.7%, 65%, and 68%, respectively. The mean jaundice-free survival of group A and group B were 34.0 ± 3.6 months (95% CI, 27.9-41.2months) and 22.9 ± 2.7 months (95%CI, 17.5-28.2months) (p = 0.254), respectively. Two PTBD drainage tube infection cases occurred in group A and group B separately.

CONCLUSIONS

125I intraluminal brachytherapy is an effective and safe therapy for treating patients with obstructive jaundice induced by tumor thrombus.

Clinical efficacy and safety analysis of CT-guided 125I implantation in the treatment of recurrent or metastatic pelvic malignant tumor

PURPOSE

This study was conducted to evaluate the clinical efficacy and safety of computed tomography (CT)-guided ¹²⁵I implantation in the treatment of recurrent or metastatic pelvic malignant tumor.

METHODS AND MATERIALS

This retrospective study analyzed the data of 30 patients with recurrent and metastatic pelvic malignant tumor who were treated with CT-guided ¹²⁵I implantation between January 2016 and December 2020. Disease control rate, objective remission rate, overall survival (OS), pain relief rate, quality of life score, and complications were evaluated after the followup.

RESULTS

Median followup was 20.1 (7-30) months. Disease control rate was 86.67% at 6 months. Objective response rates at 1, 3, and 6 months were 36.67%, 60%, and 56.67%, respectively. OS rates at 12 and 24 months were 76.67% (23/30) and 33.33% (10/30), respectively. Progression-free survival rates at 12 and 24 months were 63.33% (19/30) and 33.33% (10/30), respectively. Postoperative pain relief rate was 86.67% (26/30). There were no major bleeding, pelvic abscess, intestinal fistula, intestinal perforation, and other serious complications.

CONCLUSIONS

CT-guided ¹²⁵I seed implantation in the treatment of patients with pelvic malignant tumor is a simple operation and less traumatic and can improve patients' quality of life and reduce tumor load.

[Analysis of the effect of percutaneous vertebroplasty combined with (125)I seed implantation in the treatment of spinal metastatic epidural spinal cord compression]

Objective: To investigate the clinical efficacy of percutaneous vertebroplasty (PVP) combined with iodine-125 ((125)I) seed brachytherapy in the treatment of spinal metastatic epidural spinal cord compression (MESCC) and toassess the changes inthe grade of epidural spinal cord compression (ESCC) by magnetic resonance imaging (MRI). Methods: A total of 37 MESCC patients treated with PVP combined with (125)I seed brachytherapy in the interventional and vascular surgery department of Zhongda Hospital affiliated to Southeast University from January 2014 to June 2019 were retrospectively analyzed, including 23 cases of bilateral lower limbs paralysis. Total diseased vertebrae are 39 segments. Visual analogue scale (VAS) and paralysis of lower extremities were evaluated regularly before and after treatment, and VAS values at different follow-up time points were compared. At the same time, MRI was used to evaluate the changes of ESCC grade in the spinal canal and calculate the local lesion efficiency after operation. The postoperative local lesion efficiency at different follow-up times was compared. Results: PVP combined with (125)I seed implantation in all diseased vertebral bodies was successful. The average injection volume of polymethylmethacrylate (PMMA) was (3.2±1.3) ml/segment, the average number of (125)I seed implanted was (25.0±8.6) seeds/segment and the average radiation dose was (15.0±5.1) mCi/segment. The VAS before operation was 8.5, and postoperative VAS were respectively 3.6±1.3, 3.8±1.5, 3.4±1.4, 5.5±1.0, 5.9±1.4 at 5 days, 1 month, 3 months, 6 months, and 1 year after operation. The differences between all follow-up time points and preoperative VAS values were statistically significant (all P<0.001). Compared with 5 days, 1 month and 3 months after operation, VAS increased significantly at 6 months and 1 year after operation, and the difference was statistically significant (all P<0.001); there was no significant difference between the VAS value at 6 months after operation and 1 year after operation (P=0.405). At a follow-up of 3 months, 22 of 23 patients with paralysis of bilateral lower limbs regained the functions of autonomous walking and voiding; the effective rates of MESCC local lesions evaluated by MRI at 1 month, 3 months, 6 months, and>1 year were 89.7%, 91.9%, 90.6%, and 94.7%, respectively, and there was no statistically significant differences among those follow-up time points (all P>0.05). Conclusions: PVP combined with (125)I seed brachytherapy in the treatment of MESCC has significant improvement in immediate pain relief and spinal cord function. After combined treatment, MRI showed that the tumors around the spinal cord regressed dramatically, which could considerably reduce the MESCC grade and remain stable for a long time.

[Brachytherapy treatment planning calculation (125)I particle esophageal stent dosimetric study]

Objective: To investigate the dosimetric distribution characteristics of (125)I seed stents with different seed spacing, diameter and length, as well as different (125)I seed activity. The dosimetry table of (125)I seed esophageal stent was derived to provide dosimetry for its clinical application. Methods: The self-expanding coated esophagus stent was designed to carry radioactive (125)I seeds with different length, diameter and seed spacing. A cylindrical organic glass model (Thickness 0.8 cm, diameter 20 cm, height 20 cm) was fixed vertically to a cylindrical organic glass containing a solid paraffin (analytical pure) solution. After paraffin cooling and solidification, CT scan was used to transmit image information to TPS. With the center of the bracket as a dot, the cumulative dose at a distance of 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0 and 8.0 cm away from the dot was simulated respectively in 0° and 9° direction. Results: The radial cumulative dose with the seed spacing which was 1.0 and 1.5 cm were different by 4.8%, 5.8%, 7.2%, 8.0%, 8.6% and 13.3% respectively under the exposure of 18.5, 22.2, 25.9, 29.6, 33.3 and 37.0 MBq. When the seed spacing was the same as the length of the stent, the radial cumulative dose with the stent which diameter was 1.3, 2.0, 2.4 cm were different by 4.9% vs 3.4%, 4.7% vs 3.8%, 5.4% vs 6.6%, 4.5% vs 5.3%, 4.7% vs 4.8%, 4.8% vs 5.4% respectively under the exposure of 18.5, 22.2, 25.9, 29.6, 33.3 and 37.0 MBq. When the seed spacing was the same as the diameter of the stent, the radial cumulative dose with the stent which length was 8, 12, 16 cm were different by 1.9% vs 1.2%, 1.7% vs 0.8%, 1.6% vs 1.3%, 1.9% vs 1.5%, 1.7% vs 1.8%, 1.6% vs 1.3% respectively under the exposure of 18.5, 22.2, 25.9, 29.6, 33.3 and 37.0 MBq. Conclusions: The radial cumulative dose of the (125)I seed stent is positively correlated with the activity of the radioactive seeds, Which means the dose rate of a certain point of the (125)I seed stent increase with the increase of the activity of the radioactive seeds. The stent of the (125)I radioactive seeds is negatively correlated with the distance, the dose rate of the (125)I seed stents decrease rapidly with the increase of distance.

I125 brachytherapy guided by individual three-dimensional printed plates for recurrent ameloblastoma of the skull base

Ameloblastoma is one of the most common benign odontogenic tumours of the mandible and the maxilla. Wide excision of the tumour is the first choice for treatment (except for unicystic ones). Patients with invaded margins or unresectable lesions may require radiotherapy. Today, permanent implantation of I¹²⁵ seeds is widely used in the treatment of cancer of the head and neck. We report a case of recurrent ameloblastoma of the base of the skull that was treated with I¹²⁵ brachytherapy. The outcome has been encouraging, with total disappearance of the tumour on positron emission tomography 18 months later.

A pilot study of intraluminal brachytherapy using 125I seed strand for locally advanced pancreatic ductal adenocarcinoma with obstructive jaundice

PURPOSE

To investigate the safety and feasibility of intraluminal brachytherapy using 125I seed strand for locally advanced pancreatic ductal adenocarcinoma with obstructive jaundice.

METHODS AND MATERIALS

From January 2010 to February 2015, 18 consecutive patients diagnosed with locally advanced, nonmetastatic, inoperable pancreatic ductal adenocarcinoma with obstructive jaundice were enrolled and underwent intraluminal brachytherapy using 125I seed strand. Dose calculation was performed using a software. The procedure-related and radiation complications were assessed. Obstruction-free survival and overall survival were calculated using the Kaplan-Meier method.

RESULTS

The technique successful rate of 125I seed strand implantation was 100%. Successful bile drainage was achieved in all patients. The estimated mean accumulating dose (R = 5 mm, z = 0, 240 days) was 167.2 Gy, from 164.19 to 170.05 Gy. Two patients had adverse event of Grade 3, one of Grade 4. Stent dysfunction occurred in 1/18 (5.6%) patients. The mean and median obstruction-free survival time were 10.61 months (95% confidence interval [CI]: 7.04, 14.18) and 7.26 months (95% CI: 2.14, 12.38). The mean and median overall survival time were 11.91 months (95% CI: 7.39, 16.43) and 7.26 months (95% CI: 2.14, 12.38).

CONCLUSIONS

Intraluminal brachytherapy using 125I seed strand may be consider as a safe treatment option for the therapy of locally advanced pancreatic duct adenocarcinoma complicated by obstructive jaundice with acceptable complication rates.

CT-guided permanent 125I seed interstitial brachytherapy for recurrent retroperitoneal lymph node metastases after external beam radiotherapy

PURPOSE

To evaluate the feasibility, efficacy, and safety of permanent (125)I seed interstitial brachytherapy reirradiation in patients with retroperitoneal lymph node recurrence under CT guidance.

METHODS AND MATERIALS

Seventeen patients with 19 retroperitoneal lymph node recurrence after external beam radiotherapy underwent CT-guided (125)I seed implant brachytherapy from October 2007 to August 2014. Treatment for all patients was preplanned using a three-dimensional radiation therapy planning system 3-5 days before brachytherapy; dosimetry verification was performed immediately after brachytherapy.

RESULTS

The actuarial D90 (dose delivered to 90% of the target volume) was 100-198 Gy (median, 126.5 Gy). In 9 patients, pain intensity decreased to mild pain 1-3 weeks after brachytherapy. Pain-free survival ranged 2-15 months (median, 5 months; 95% confidence interval [CI]: 0.1, 9.9). The overall response rate was 19 of 19 (100%). The median local control time was 15 months (95% CI: 2.3, 27.7). The 6-, 12-, and 24-month local control rate was 88.0%, 63.2%, and 42.1%, respectively. Twelve patients (70.6%) developed distant metastases and died. Two patients (11.8%) are alive with distant metastases but no evidence of local recurrence. Three patients (17.6%) are alive with no evidence of local recurrence. Median overall survival was 10 months (95% CI: 5.7, 14.3); the 1- and 2-year survival rates were 38.1% and 15.3%, respectively. No major complications related to the procedure occurred during or after brachytherapy.

CONCLUSIONS

Reirradiation with CT-guided permanent (125)I seed interstitial brachytherapy is feasible, safe, and effective as pain relief or salvage treatment for patients with recurrent retroperitoneal lymph nodes.

Computed tomographic-guided iodine-125 interstitial implants for malignant thoracic tumors

PURPOSE

To evaluate the feasibility and efficacy of percutaneous interstitial brachytherapy using iodine-125 ((125)I) radioactive seeds under computed tomographic (CT) guidance for malignant thoracic tumors.

MATERIALS AND METHODS

Forty-one patients (34 males, 7 females; 18-90 years; mean, 63.7 years) with 77 lesions (3 in the mediastinum, 7 in the chest wall, 67 in the lung) underwent percutaneous interstitial implantation of (125)I radioactive seeds under CT guidance. A treatment planning system (TPS) was employed to calculate the number and distribution of seeds preoperatively. An 18-G needle was inserted into the lesions under CT guidance and send the seeds according to TPS. Two patients with mediastinal lesions undergoing seed implantation received an artificial pneumothorax. One patient with lung carcinoma adjacent to the anterior mediastinum underwent seed implantation through the sternum. Follow-up CT was done every 2 months postoperatively.

RESULTS

The procedure was successful in all patients. No major procedure-associated death occurred. The mean duration of follow-up was 19.4 ± 1.3 months (3-49 months). A complete response (CR) was seen in 49 lesions (63.6%), partial response (PR) in 9 lesions (11.7%), stable disease (SD) in 12 lesions (12.8%), and progressive disease (PD) in 7 lesions (7.4%). The overall response rate (CR+PR) was 75.3%; the local control rate (CR+PR+SD) was 90.9%. The 1-, 2- and 3-year progression-free rates for local tumors were 91%, 88% and 88%, respectively. The 1-, 2- and 3-year survival rates were 87%, 74% and 68%, respectively.

CONCLUSION

Implantation of CT-guided (125)I seeds is feasible and effective for patients with malignant thoracic tumors.