Quantitative assessment of interstitial implants

Experimental validation of the accuracy of robotic-assisted radioactive seed implantation for tumor treatment

An experimental validation of a robotic system for radioactive iodine-125 seed implantation (RISI) in tumor treatment was conducted using customized phantom models and animal models simulating liver and lung lesions. The robotic system, consisting of planning, navigation, and implantation modules, was employed to implant dummy radioactive seeds into the models. Fiducial markers were used for target localization. In phantom experiments across 40 cases, the mean errors between planned and actual seed positions were 0.98 ± 1.05 mm, 1.14 ± 0.62 mm, and 0.90 ± 1.05 mm in the x, y, and z directions, respectively. The x, y, and z directions correspond to the left-right, anterior-posterior, and superior-inferior anatomical planes. Silicone phantoms exhibiting significantly smaller x-axis errors compared to liver and lung phantoms (p < 0.05). Template assistance significantly reduced errors in all axes (p < 0.05). No significant dosimetric deviations were observed in parameters such as D90, V100, and V150 between plans and post-implant doses (p > 0.05). In animal experiments across 23 liver and lung cases, the mean implantation errors were 1.28 ± 0.77 mm, 1.66 ± 0.69 mm, and 1.86 ± 0.93 mm in the x, y, and z directions, slightly higher than in phantoms (p < 0.05), with no significant differences between liver and lung models. The dosimetric results closely matched planned values, confirming the accuracy of the robotic system for RISI, offering new possibilities in clinical tumor treatment.

Validation of automated post-adjustments of HDR prostate brachytherapy treatment plans by quantitative measures and oncologist observer study

PURPOSE

The aim was to evaluate a postprocessing optimization algorithm's ability to improve the spatial properties of a clinical treatment plan while preserving the target coverage and the dose to the organs at risk. The goal was to obtain a more homogenous treatment plan, minimizing the need for manual adjustments after inverse treatment planning.

MATERIALS AND METHODS

The study included 25 previously treated prostate cancer patients. The treatment plans were evaluated on dose-volume histogram parameters established clinical and quantitative measures of the high dose volumes. The volumes of the four largest hot spots were compared and complemented with a human observer study with visual grading by eight oncologists. Statistical analysis was done using ordinal logistic regression. Weighted kappa and Fleiss' kappa were used to evaluate intra- and interobserver reliability.

RESULTS

The quantitative analysis showed that there was no change in planning target volume (PTV) coverage and dose to the rectum. There were significant improvements for the adjusted treatment plan in: V150% and V200% for PTV, dose to urethra, conformal index, and dose nonhomogeneity ratio. The three largest hot spots for the adjusted treatment plan were significantly smaller compared to the clinical treatment plan. The observers preferred the adjusted treatment plan in 132 cases and the clinical in 83 cases. The observers preferred the adjusted treatment plan on homogeneity and organs at risk but preferred the clinical plan on PTV coverage.

CONCLUSIONS

Quantitative analysis showed that the postadjustment optimization tool could improve the spatial properties of the treatment plans while maintaining the target coverage.

Interstitial Brachytherapy for Lip Cancer: Technical Aspects to Individualize Treatment Approach and Optimize Outcomes

Primary radiation therapy using interstitial brachytherapy (IBT) provides excellent local tumor control for early-stage squamous cell carcinoma of the lip. Technical aspects of treatment are important to optimize outcomes. In this report, we discuss patient selection criteria, procedural details, and dosimetric considerations for performing IBT for cancers of the lip. Catheters are inserted across the length of tumor entering and exiting approximately 5 mm beyond the palpable tumor extent. A custom mouthpiece is fabricated to facilitate normal tissue sparing. Patients undergo computed tomography imaging, the gross tumor volume is contoured based on physical examination and computed tomography findings, and an individualized brachytherapy plan is generated with the goals of achieving gross tumor volume D90% ≥ 90% and minimizing V150%. Ten patients with primary (n = 8) or recurrent (n = 2) cancers of the lip who received high-dose-rate lip IBT using 2.0- to 2.5-week treatment regimens are described (median prescription: 47.6 Gy in 14 fractions of 3.4 Gy). Local tumor control was 100%. There were no cases of acute grade ≥4 or late grade ≥2 toxicity, and cosmesis scores were graded as good to excellent in all patients. IBT represents an excellent treatment option for patients with lip squamous cell carcinoma. With careful attention to technical considerations furthered described in the present report, high rates of tumor control, low rates of toxicity, and favorable esthetic and functional outcomes can be achieved with IBT for lip cancer.

Efficacy and safety of CT-guided 125I seed implantation by coplanar template as a salvage therapy for vertebral metastases after failure of external beam radiation therapy: a retrospective study

Purpose

To evaluate the efficacy safety of computed tomography (CT)-guided ¹²⁵I seed implantation by coplanar template for vertebral metastases after failure of external beam radiation therapy (EBRT).

Material and methods

Retrospective analysis of the clinical outcomes of 58 patients with vertebral metastases after failure of EBRT, who underwent ¹²⁵I seed implantation as a salvage treatment with a CT-guided coplanar template-assisted technique from January 2015 to January 2017.

Results

The mean post-operative NRS score decreased significantly at T_4w (3.5 ± 0.9, p<0.01), T_8w (2.1 ± 0.9, p<0.01), T_12w (1.5 ± 0.7, p< 0.01) and T_6m (1.2 ± 0.6, p< 0.01) respectively. The local control rates after 3, 6, 9 and 12 months were 100% (58/58), 93.1% (54/58), 87.9% (51/58), and 81% (47/58), respectively. The median overall survival time was 18.52months (95% CI, 16.24-20.8), and 1- and 2-year survival rates were 81% (47/58) and 34.5% (20/58), respectively. By performing a paired t-test analysis, there was no significant difference in D90, V90, D100, V100, V150, V200, GTV volume, CI, EI and HI between preoperative and postoperative (p>0.05).

Conclusions

¹²⁵I seed implantation can be used as a salvage treatment for patients with vertebral metastases after failure of EBRT.

Long-term result of 125 I seed brachytherapy for pediatric desmoid tumor in the head and neck

BACKGROUND

Desmoid tumor (DT) is rare and challenging, often affects the head and neck (HN) region in children, and its appropriate treatments are under-discussed. This study aimed to retrospectively evaluate the long-term effectiveness and safety of ¹²⁵ I seed brachytherapy for pediatric DT in HN.

PROCEDURE

Seven pediatric patients with a median age of three years who suffered from DT in HN treated with ¹²⁵ I brachytherapy from January 2008 to June 2018 were included. Among these, five underwent sole brachytherapy and the others combined with surgery under prescription doses ranging from 10,000 to 12,000 cGy. The rate of local control (LC), complete response (CR), and partial response (PR) was calculated after evaluation by radiological and pathological means. Radiation-associated toxicities were also evaluated.

RESULTS

The LC rate was 7/7 during the follow-up time ranging from 43 to 135 months and with a mean of 57 months. No recurrent lesion was found in the patients receiving surgery combined with brachytherapy. In patients treated with sole brachytherapy, the radiological PR rate and CR rate were 4/5 and 1/5, respectively. In those reaching radiological PR, 3/4 were pathological CR. Slight acute radiation-associated toxicities were observed in all patients, and no late or severe acute toxicity was observed.

CONCLUSION

¹²⁵ I brachytherapy is effective and safe in the management of pediatric DT in HN as the sole modality or combined with surgery in the long term.

Dosimetric predictors of local control and complications in gynecologic transperineal implant patients: The medical college of wisconsin experience

PURPOSE

Investigate the relationship between dosimetric parameters with local control (LC) and complications following transperineal high-dose rate (HDR) interstitial brachytherapy (ISBT) for gynecologic (GYN) malignancies.

METHODS AND MATERIALS

Between 2001 and 2016, 59 patients were treated for primary or recurrent GYN malignancies. Most patients received external beam irradiation, followed by transperineal ISBT via the Syed-Neblett applicator set with CT-based planning. Treatment plans were retrospectively reviewed to evaluate for an association among LC or toxicity with the equivalent dose at 2 Gy per fraction (EQD2) for the clinical target volume (CTV), 0.1 cc (D0.1cc), and 2 cc (D2cc) volumes of the organs at risk (OAR), low/high dose volumes for the OAR and CTV, and ratio of dose at the core vs. the implant periphery.

RESULTS

The median follow-up among survivors was 24 months. 34% of patients had a component of local failure and in 12%, this was isolated. Late grade 3 (G3) toxicity occurred in 15% of patients. There were no G4-5 toxicities. Rectal D0.1cc > 75 Gy trended toward significance in predicting the development of non-fistula late G2-3 rectal complications. Bladder D0.1cc > 94 Gy significantly predicted for the development of late G2-3 vesicovaginal fistula formation. The ratio of the total dose at the vaginal surface to the needle periphery above 121% trended in predicting for any complication or fistula formation.

CONCLUSIONS

HDR ISBT combined with EBRT achieved LC in 66% of patients with advanced or recurrent GYN cancers. Rectal and bladder D0.1cc doses may be predictive of complications as may the ratio of the implant dose at the core vs. periphery.

Analysis on the accuracy of CT-guided radioactive I-125 seed implantation with 3D printing template assistance in the treatment of thoracic malignant tumors

This article analyzes the accuracy of needle track and dose of a 3-dimensional printing template (3DPT) in the treatment of thoracic tumor with radioactive I-125 seed implantation (RISI). A total of 28 patients were included. The technical process included: (i) preoperative CT positioning, (ii) preoperative planning design, (iii) 3DPT design and printing, (iv) 3DPT alignment, (v) puncture and seed implantation. The errors of needle position and dosimetric parameters were analyzed. A total of 318 needles were used. The mean errors in needle depth, needle insertion point, needle tip and needle angle were 0.52 ± 0.48 cm, 3.4 ± 1.7 mm, 4.4 ± 2.9 mm and 2.8 ± 1.7°, respectively. The differences between actual needle insertion angle and needle depth and those designed in the preoperative were statistically significant (p < 0.05). The mean values of all the errors of the chest wall cases were smaller than those of the lungs, and the differences were statistically significant (p < 0.05). There was no significant difference between the D90 calculated in the postoperative plan and those designed in the preoperative and intraoperative plans (p > 0.05). Some dosimetric parameters of preoperative plans such as V100, V200, CI and HI were not consistent with that of preoperative plans, and the difference was statistically significant (p < 0.05). However, there were no statistical difference in the dosimetric parameters between the postoperative plans and intraoperative plans (p > 0.05). We conclude that for thoracic tumors, even under the guidance of 3DPT, there will be errors. The plan should be optimized in real time during the operation.

3D-printed template and optical needle navigation in CT-guided iodine-125 permanent seed implantation

Purpose

To preliminarily verify the accuracy of navigation-assisted seed implantation by comparing pre-operative and actual differences in puncture characteristics and dosimetry in computed tomography (CT)-guided, navigation-assisted radioactive iodine-125 seed implantation, using 3D-printed templates for malignant tumors’ treatment.

Material and methods

A total of 27 tumor patients, who were treated with seed implantation under combination guidance in our hospital between December 2019 and December 2020 were enrolled in this study. Navigation needles (n = 1-3) were placed in each patient to obtain pre-operative and intra-operative puncture information, such as angle, depth, insertion point, and tip position. Moreover, dosimetry parameters in pre-operative and post-operative plans, including D₉₀, V₁₀₀, V₁₅₀, V₂₀₀, minimum peripheral dose (MPD), conformal index, external index, and homogeneity index of target area were investigated.

Results

Mean errors of the angle, depth, insertion point, and tip position were 0.5 ±0.5°, 4.0 ±2.0 mm, 1.7 ±1 mm, and 3.1 ±1.8 mm, respectively. There were no significant differences between intra-operative and pre-operative angles (p = 0.271), but there was a significant difference in the depth (p = 0.002). Errors of the angle, depth, and insertion point were larger for the pelvic/retroperitoneal area than for the head and neck/chest wall (p < 0.05). With the exception of MPD, there was no significant difference in dosimetry indices between post-operative and preoperative plans (p > 0.05).

Conclusions

Seed implantation under combination guidance showed good accuracy, and the actual intra-operative puncture information and post-operative doses were in agreement with those in the pre-operative plan, thereby demonstrating promising prospects for further development.

Dosimetric comparison of computed tomography-guided iodine-125 seed implantation assisted with and without three-dimensional printing non-coplanar template in locally recurrent rectal cancer: a propensity score matching study

Purpose

To compare post-implant dosimetric parameters of computed tomography (CT)-guided radioactive iodine-125 (¹²⁵I) seed (RIS) implantation assisted with and without three-dimensional printing non-coplanar template (3D-PNCT) in locally recurrent rectal cancer (LRRC).

Material and methods

One hundred and fifty-five LRRC patients treated by CT-guided RIS implantation assisted with or without 3D-PNCT from October 2003 to May 2019 were included in this study. Propensity score matching (PSM) method (1 : 1) was used to adjust for differences between the 3D-group (with 3D-PNCT) and the CT-group (without 3D-PNCT). After PSM, dosimetric parameters [D₉₀ (dose that covered 90% of target volume), D₁₀₀ (dose that covered 100% of target volume), V₁₀₀ (percentage of gross tumor volume (GTV) receiving 100% of prescription dose), V₁₅₀ (percentage of GTV receiving 150% of prescription dose), HI (homogeneity index), CI (conformity index), and EI (external index)] of the two groups were compared.

Results

After PSM, 45 pairs of matched cases were selected for analysis and differences in variables between the two groups were balanced. For the 3D-group, median values of D₉₀, D₁₀₀, V₁₀₀, V₁₅₀, EI, and HI were 142.6 Gy (73.7-218.2 Gy), 73.7 Gy (26.2-169.3 Gy), 94.1% (74.3-100%), 71.8% (35.4-98.3%), 0.7 (0.1-30.7), and 0.20 (0-0.60), respectively, and corresponding values were 119.9 Gy (39.8-159.3 Gy), 47.0 Gy (13.0-200.9 Gy), 89.9% (38.6-100%), 62.8% (14.8-100%), 0.39 (0-11.01), and 0.30 (0-0.95), respectively, for the CT-group. Parameters including D₉₀, D₁₀₀, V₁₀₀, V₁₅₀, and EI in the 3D-group were significantly higher than those in the CT-group (p < 0.001, p < 0.001, p < 0.001, p < 0.001, and p = 0.006, respectively).

Conclusions

3D-PNCT can improve the accuracy of radioactive seed implantation by increasing the dose delivered to the tumor and reducing the number of “cold” spots of dose.

Accuracy and dosimetric parameters comparison of 3D-printed non-coplanar template-assisted computed tomography-guided iodine-125 seed ablative brachytherapy in pelvic lateral recurrence of gynecological carcinomas

Purpose

To investigate the accuracy of needle distribution and dosimetric parameter differences of 3D-printing non-coplanar template (3D-PNCT)-assisted computed tomography (CT)-guided iodine-125 seed ablative brachytherapy (¹²⁵I-SAB) in gynecological cancer patients with non-central pelvic recurrence between pre-operative plan and post-operative plan.

Material and methods

Thirty-eight patients with forty-one non-central pelvic recurrent gynecological carcinomas after radiotherapy were enrolled in this study. All patients received 3D-PNCT-assisted CT-guided ¹²⁵I-SAB from January 2016 to January 2019. The position, angle, and depth of seed needles were measured in both pre-operative plan and intra-operative real-time plan in brachytherapy treatment planning system (B-TPS). Dosimetric parameters of D₉₀, D₁₀₀, V₁₀₀, V₁₅₀, and V₂₀₀ as well as quality parameters of conformal index (CI), external index (EI), and homogeneity index (HI) were compared between pre-operative plan and post-operative plan. Peri-operation complications and radiation-related toxicity were assessed.

Results

Median follow-up time was 12 months (range, 5-34 months). Prescribed dose was 100-170 Gy (median, 120 Gy). Radioactivity of ¹²⁵I seed was 0.4-0.7 mCi (median, 0.55 mCi). Mean depth deviation for 499 needles was 0.8 ±1.0 cm. Mean angular deviation was 2.2 ±2.1 degrees. Mean tip distance deviation of needles was 0.4 ±0.3 cm. There were significant differences between pre-operative and post-operative plans in CI (p = 0.001) and EI (p = 0.005). No significant differences were shown in D₉₀, D₁₀₀, V₁₀₀, V₁₅₀, V₂₀₀, and HI between pre-operative and post-operative plans. Only few patients suffered from ≤ grade 2 toxicities.

Conclusions

3D-PNCT-assisted CT-guided ¹²⁵I-SAB is safe and feasible for non-central pelvic recurrence of gynecological cancer. All complications are tolerable and mild.

An audit of high dose-rate prostate brachytherapy treatment planning at six Swedish clinics

Purpose

High dose-rate prostate brachytherapy has been implemented in Sweden in the late 1980s and early 1990s in six clinics using the same schedule: 20 Gy in two fractions combined with 50 Gy in 25 fractions with external beam radiation therapy. Thirty years have passed and during these years, various aspects of the treatment process have developed, such as ultrasound-guided imaging and treatment planning system. An audit was conducted, including a questionnaire and treatment planning, which aimed to gather knowledge about treatment planning methods in Swedish clinics.

Material and methods

A questionnaire and a treatment planning case (non-anatomical images) were sent to six Swedish clinics, in which high-dose-rate prostate brachytherapy is performed. Treatment plans were compared using dosimetric indices and equivalent 2 Gy doses (EQD₂). Treatment planning system report was used to compare dwell positions and dwell times.

Results

For all the clinics, the planning aim for the target was 10.0 Gy, but the volume to receive the dose differed from 95% to 100%. Dose constraints for organs at risk varied with up to 2 Gy. The dose to 90% of target volume ranged from 10.0 Gy to 11.1 Gy, equivalent to 26.0 Gy EQD₂ and 31.3 Gy EQD₂, respectively. Dose non-homogeneity ratio differed from 0.18 to 0.32 for clinical target volume (CTV) in treatment plans and conformity index ranged from 0.52 to 0.59 for CTV.

Conclusions

Dose constraints for the organs at risk are showing a larger variation than that reflected in compared treatments plans. In all treatment plans in our audit, at least 10 Gy was administered giving a total treatment of 102 Gy EQD₂, which is in the upper part of the prescription doses published in the GEC/ESTRO recommendations.

Comparison of post-implant dosimetrics between intraoperatively built custom-linked seeds and loose seeds by sector analysis at 24 hours and 1 month for localized prostate cancer

Purpose

To compare post-implant dosimetrics between intraoperatively built custom-linked (IBCL) seeds and loose seeds (LS) at 24 hours and 1 month by sector analysis, and to evaluate the effect of IBCL seeds with regard to change in dosimetric parameters, in patients with prostate cancer treated with brachytherapy.

Material and methods

Consecutive patients treated for localized prostate cancer who received definitive brachytherapy between March 2013 and October 2017 were retrospectively analyzed. Prostate V₁₀₀ (PV₁₀₀), prostate D₉₀ (PD₉₀), prostate V₁₅₀ (PV₁₅₀), urethral D₃₀ (UD₃₀), urethral V₁₅₀ (UV₁₅₀), and rectal V₁₀₀ (RV₁₀₀) were assessed.

Results

Thirty-two patients were treated with LS and 32 patients were treated with IBCL seeds. The median follow-up time was 49.9 months in the LS group and 27.1 months in the IBCL group. PV₁₅₀, UV₁₅₀, and UD₃₀ at 24 hours and UD₃₀ at 1 month showed significant difference (F-test), and standard deviation (SD) tended to be lower in the IBCL group. Analysis of change in the variables revealed significance for ΔPV₁₀₀ and ΔPD₉₀ (F-test, p = 0.014 and < 0.001, respectively), and ΔPV₁₅₀ and ΔUD₃₀ showed marginal significance (p = 0.084 and 0.097, respectively). PV₁₅₀, UV₁₅₀, and UD₃₀ at 24 hours and 1 month were significantly lower in the IBCL group, and there was no significant difference in PV₁₀₀, PD₉₀, and RV₁₀₀ compared with the LS group (t-test). The homogeneity index (HI) was significantly higher in the IBCL group (p < 0.001).

Conclusions

In this retrospective single institutional study, there was a decrease in the SD of the dosimetric parameters in the IBCL group, and it was statistically significant in change in the variables between 24 hours and 1 month (F-test). The use of IBCL seeds significantly decreased PV₁₅₀, UV₁₅₀, and UD₃₀, and significantly improved HI, without lowering PD₉₀ or PD₁₀₀.

The Preliminary Results of 3-Dimensional Printed Individual Template Assisted 192Ir High-Dose Rate Interstitial Brachytherapy for Central Recurrent Gynecologic Cancer

Objective:

To evaluate the feasibility and safety of high dose rate interstitial brachytherapy (HDR-IB) assisted with 3-dimensional printing individual template (3D-PIT) for central pelvic recurrent gynecologic cancer (CR-GYN).

Methods:

Totally 32 patients diagnosed with CR-GYN received iridium-192(192Ir) HDR-IB assisted with 3D-PIT that was classified in 2 types(Type I: transvaginal template/ applicator, and Type II: transvaginal combined transperineal template). The prescribed dose to gross tumor volume (GTV) was 10-36 Gy in 2-6 fractions. We rely on a few dosimetric parameters for quality control. The short-term efficacy was evaluated by RECIST v1.1, and the adverse event was evaluated by CTCAE V4.0.

Results:

The median V100, D100 and D90 of per fraction among all the patients were 88.9%±9.8%, 3.45Gy±0.54 Gy, and 5.79Gy±0.32 Gy, respectively. Dosimetric comparison between preplan and treatment plan of 20/32 patients with Type II 3D-PIT showed no significant difference in GTV volume, V100, D100, D90, conformation index (CI) and homogeneity index (HI). No severe treatment complications occurred. Grade 3 or 4 late toxicities (fistula) were observed in 3 patients (9%). The local response rate (complete remission, CR + partial remission, PR) was 84.4% (27/32) 1 month after completion of treatment. The median time to progression (TTP) was 15.4 months (95% CI 11.3- 19.6 months), 1-year local control (LC) rate were 51.7%.

Conclusions:

HDR-IB assisted by 3D-PIT was a reliable modality for CR-GYN due to the clinical feasibility and accepted complications.

A novel three-dimensional template combined with MR-guided 125I brachytherapy for recurrent glioblastoma

Background

At present, the treatment of recurrent glioblastoma is extremely challenging. In this study, we used a novel three-dimensional non-coplanar template (3DNPT) combined with open MR to guide ¹²⁵I seed implantation for recurrent glioblastoma. The aim of this study was to evaluate the feasibility, accuracy, and effectiveness of this technique.

Methods

Twenty-four patients of recurrent glioblastoma underwent 3DNPT with open MR-guided ¹²⁵I brachytherapy from August 2017 to January 2019. Preoperative treatment plan and 3DNPT were made according to enhanced isovoxel T1-weighted MR images. ¹²⁵I seeds were implanted using 3DNPT and 1.0-T open MR imaging guidance. Dosimetry verification was performed after brachytherapy based on postoperative CT/MR fusion images. Preoperative and postoperative dosimetry parameters of D90, V100, V200, conformity index (CI), external index (EI) were compared. The objective response rate (ORR) at 6 months and 1-year survival rate were calculated. Median overall survival (OS) measured from the date of brachytherapy was estimated by Kaplan-Meier method.

Results

There were no significant differences between preoperative and postoperative dosimetry parameters of D90, V100, V200, CI, EI (P > 0.05). The ORR at 6 months was 75.0%. The 1-year survival rate was 58.3%. Median OS was 12.9 months. One case of small amount of epidural hemorrhage occurred during the procedure. There were 3 cases of symptomatic brain edema after brachytherapy treatment, including grade three toxicity in 1 case and grade two toxicity in 2 cases. The three patients were treated with corticosteroid for 2 to 4 weeks. The clinical symptoms related to brain edema were significantly alleviated thereafter.

Conclusions

3DNPT combined with open MR-guided ¹²⁵I brachytherapy for circumscribed recurrent glioblastoma is feasible, effective, and with low risk of complications. Postoperative dosimetry matched the preoperative treatment plan. The described method can be used as a novel implantation technique for ¹²⁵I brachytherapy in the treatment of recurrent gliomas.

Trial registration

The study was approved by the Institutional Review Board of Shandong Provincial Hospital Affiliated to Shandong University (NSFC:NO.2017–058), registered 1st July 2017.

Dosimetry verification of 3D-printed individual template based on CT-MRI fusion for radioactive 125I seed implantation in recurrent high-grade gliomas

Purpose

To verify the accuracy and efficacy of three-dimensional printing individual template (3D-PIT) with computed tomography-magnetic resonance imaging (CT-MRI) fusion for radioactive iodine-125 (¹²⁵I) seed implantation in high-grade brain gliomas.

Material and methods

Between June 2017 and June 2018, 16 patients with recurrent high-grade gliomas (rHGG) underwent radioactive seed implantation with 3D-PIT. The prescribed dose was 120-140 Gy. We compared the dose distribution of the postoperative plan with the preoperative plan. Dose parameters included D₉₀, V₁₀₀, V₂₀₀, conformity index (CI), and external index of the target volume (EI). Local control and early complications were also analyzed.

Results

Sixteen treatment areas were reported in our study. Median gross tumor volume (preoperative) of patients was 64.2 cm³, median needle number was 8, and median number of implanted ¹²⁵I seeds was 60. For postoperative plans, the median D₉₀, V₁₀₀, and V₂₀₀ was 152.1 Gy, 96.8%, and 49.1%, respectively, and 151.7 Gy, 97.0%, and 48.9%, respectively, in preoperative plans. Comparing with the preplanned cases, the dose of the target volume was slightly higher; the high-dose area of the target volume was larger in postoperative cases, but the difference was not statistically significant (p > 0.05). Actual dose conformity of the target volume was greater than preplanned, and the difference was not statistically significant (p > 0.05). Local control was 81.25% and 75% at 3 and 6 months after implantation, respectively. No serious early toxicities were observed.

Conclusions

3D-PIT based on the CT-MRI fusion images can result in good accuracy for positioning and dose distribution in radioactive seed implantation for treatment of rHGG.

Comparative study for CT-guided 125I seed implantation assisted by 3D printing coplanar and non-coplanar template in peripheral lung cancer

Purpose

We compared the three-dimensional printed non-coplanar template (3DPNCT) plans with 3D-printed coplanar template (3DPCT) plans for radioactive seed implantation (RSI) in lung cancer and explored the differences between the two technologies.

Material and methods

33 patients with peripheral lung cancer that received 3DPCT-assisted RSI in our department between June 2017 and February 2018 were analyzed. A 3DPNCT plan was re-designed for all patients. The prescribed dose and seed activity in the new plan were the same as the 3DPCT plan. The data in the two plans were compared, including seed number, needle number, number of needles needed to cross the ribs, and dosimetry parameters. Dosimetry parameters included D₉₀, D_mean, MPD (minimum peripheral dose), V₁₀₀, V₁₅₀, CI (conformity index), EI (external index), HI (homogeneity index) of target volume, D_2cc of spinal cord and aorta, and V₂₀ of affected side lung. We used a paired t-test and two groups of related non-parameters tests to examine statistical significance. A p value < 0.05 was considered statistically significant.

Results

We found no significant difference in dosimetry parameters (p > 0.05), except MPD. The mean MPD of the 3DPNCT plan was significantly higher than the 3DPCT plan (88.5 Gy and 81.8 Gy, respectively, p = 0.017). The number of needles used in the 3DPNCT plan and the number of needles needed to cross the ribs were significantly less compared with the 3DPCT plan (p = 0.000).

Conclusions

The dose distributions of the two 3DPCT plans were similar. 3DPNCT plan had a higher dose in target volume margin, with fewer needles and fewer breaks to the ribs.

Template-assisted 192Ir-based stereotactic ablative brachytherapy as a neoadjuvant treatment for operable peripheral non-small cell lung cancer: a phase I clinical trial

Purpose

To evaluate safety, feasibility, and efficacy of template-assisted ¹⁹²Ir-based stereotactic ablative brachytherapy (SABT), combined with surgery for peripheral non-small cell lung cancer (NSCLC).

Material and methods

Patients with pathologically confirmed operable peripheral NSCLC, who underwent template-assisted SABT (30 Gy delivered in one fraction) and were scheduled for tumor resection 4-6 weeks after SABT were included in this study. The perioperative adverse reactions of SABT were recorded to evaluate safety and feasibility of SABT for neoadjuvant therapy. Dosimetric data from both simulated and actual plans were collected and compared. Imaging with ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) and dynamic contrast-enhanced computed tomography were scheduled before SABT and surgery to evaluate the efficacy of the neoadjuvant therapy with SABT.

Results

Patients did not experience any serious adverse events. None of the patients had a delay in receiving surgery. After 4-6 weeks, the indicators for the efficacy of neoadjuvant therapy significantly decreased in all patients: gross tumor volume (p < 0.001), maximum standardized uptake value (p < 0.001), tumor blood volume (p < 0.001), and tumor blood flow (p = 0.008). Dosimetric parameters in the delivered SABT plan slightly changed from the preoperative simulation, but the difference was not statistically significant (p > 0.05).

Conclusions

The efficacy of template-assisted SABT for neoadjuvant therapy was significant in operable peripheral NSCLC. Moreover, no serious adverse reactions were observed; when the coplanar template guidance technique was applied, dosimetric parameters were in good agreement between the actual SABT plan and the preoperative simulated plan.

Impact of inter- and intra-observer variabilities of catheter reconstruction on multi-catheter interstitial brachytherapy of breast cancer patients

PURPOSE

The aim of this study was to evaluate inter- and intra-observer variabilities of catheter reconstruction and its dosimetric impact for multi-catheter interstitial breast cancer patients.

METHODS AND MATERIALS

In order to evaluate inter-observer variabilities (IOV) three medical physicists reconstructed the catheter traces of 13 patients. These manual reconstructions were further compared to the automatic reconstruction algorithm integrated into the planning system and one on purpose imprecise manual reconstruction. For intra-observer variabilities (IAV) repeated reconstructions of two physicists were compared for 13 patients. In total 426 catheters were considered. Keeping dwell times, dwell positions, the optimization and the normalization relative points constant the geometrical deviations between the corresponding dwell positions of the reference data set and the investigated reconstructions were evaluated. Also, the effect on the quality indices, such as coverage index (CI), dose non-uniformity ratio (DNR) or conformal index (COIN), and the exposure of the organs at risk were analyzed.

RESULTS

Over all patients and all different catheter reconstructions considered for IOV a mean deviation between the corresponding dwell positions of 0.60 ± 0.35 mm was detected. The first observer had a mean deviation of 0.54 ± 0.32 mm, whereas the second observer yielded a mean deviation of 0.58 ± 0.37 mm. The length of the catheter traces varied in the mean by 0.51 ± 0.45 mm. The mean relative deviation of the CI, DNR, COIN, mean heart dose and mean lung dose varied by 0.27 ± 0.31%, 0.0027 ± 0.0025, 0.0036 ± 0.0033, 0.024 ± 0.019%, 0.05 ± 0.11%, respectively. The skin dose (D_0.2ccm) changed in the maximum 8.52%. On average IAV reached a deviation between the corresponding dwell positions of 0.49 ± 0.30 mm. IOVs and IAVs proved to be significantly different (Wilcoxon's test p < 0.01).

CONCLUSIONS

The study proved that a repeated reconstruction of the catheter traces does not lead to large geometrical deviations or to a significant change in the dose exposure. But the lack of ground truth makes the estimation of the quality of the reconstruction challenging. A precise reconstruction mapping the reality is a necessity for the planned dose delivery. With all considered reconstruction techniques reliable quality indices for the target and the organs at risk could be obtained.

Stenting of the Portal Vein Combined with Different Numbers of Iodine-125 Seed Strands: Dosimetric Analyses

Background:

Portal-vein stent combined with one iodine-125 (¹²⁵I) seed strand has become a new treatment for portal vein tumor thrombosis. However, dosimetric aspects of this irradiation stent have not been reported. Therefore, we aimed to undertake dosimetric analyses comparing portal-vein stents combined with different numbers of ¹²⁵I seed strands.

Methods:

A water cylinder was created by a treatment-planning system to simulate a portal-vein stent. The stent was combined with one, two, or three ¹²⁵I seed strands (Groups I, II, and III, respectively). At different prescribed doses (PDs), ¹²⁵I seeds of identical activities were loaded on Groups I–III. Conformation number (CN), external volume index, and homogeneity index were calculated. Linear regression analyses were used to evaluate the obtained data.

Results:

For identical ¹²⁵I seed activity, when the ¹²⁵I seed strand increased from one chain to two, D₉₀ (dose delivered to 90% of the target volume) increased by ≥184%; when it increased from two chains to three, D₉₀ increased by ≥63%. When the PD was 105 Gy and ¹²⁵I seed strands increased from one chain to two, V₁₀₀ (percentage of the target volume receiving ≥90% of the PD) increased by 158–249%; when it increased from two chains to three, V₁₀₀ increased by 7–175%. CN was correlated positively with ¹²⁵I seed activity (B = 0.479, P < 0.001) and number of ¹²⁵I seed strands (B = 0.201, P < 0.001) and was independent of PD (B = −0.002, P = 0.078).

Conclusions:

A portal-vein stent combined with a single ¹²⁵I seed strand could not meet dosimetry requirements. For a stent combined with two ¹²⁵I seed strands, when the PD was 105 Gy and seed activity was 0.7 mCi, the dose distribution could satisfy dosimetry requirements. For a stent combined with three ¹²⁵I seed strands, if the PD was 105, 125, or 145 Gy, the recommended seed activities were 0.5, 0.5, and 0.6 mCi, respectively.

Analysis of the relationship between prescribed dose and dosimetric advantage of real-time intraoperatively built custom-linked seeds in iodine-125 prostate brachytherapy

Background

The purpose of this study was to investigate the differences in the dosimetric advantage of using intraoperatively built custom-linked (IBCL) seeds between permanent iodine-125 (I-125) seed implantation (PI) alone and PI followed by external-beam radiation therapy (EBRT) for prostate cancer.

Methods

We reviewed the records of 62 patients with localized prostate cancer who received transperineal interstitial brachytherapy with I-125 using free seeds or IBCL seeds. Twenty-four low- and intermediate-risk patients underwent PI alone with the prescribed dose of 160 Gy, and 39 high-risk patients underwent PI with 110 Gy, followed by EBRT with 45 Gy (PI + EBRT). Intraoperative and post-implant dosimetric parameters 1 month after implantation were collected and analyzed.

Results

The numbers of patients implanted with free seeds and IBCL seeds were 14 (58.3%) and 10 (41.7%), respectively, in the PI group and 25 (65.8%) and 13 (34.2%), respectively, in the PI + EBRT group. In the PI group, although there were significant differences in prostate V100 (p = 0.003) and D90 (p = 0.009) and rectum V100 (p = 0.026) on intraoperative dosimetry, these differences were not found on post-implant dosimetry. In the PI + EBRT group, the dosimetric parameters of IBCL seeds, such as prostate V200 (p = 0.013) and V250 (p = 0.010) and urethra D30 (p = 0.038), were better than those of free seeds on intraoperative dosimetry. Furthermore, even on post-implant dosimetry, prostate D90 (p = 0.004), V150 (p = 0.001), and homogeneity index (HI, p = 0.001), as well as V200 (p = 0.001) and V250 (p = 0.020), and urethra D5 (p = 0.008) as well as D30 (p = 0.003) had a better dosimetric quality in IBCL seeds than in free seeds. There was no significant difference in the operation time between free seeds and IBCL seeds in each PI and PI + EBRT group.

Conclusions

Our results reveal that greater dosimetric benefits could be obtained using IBCL seeds in the case of permanent implantation with a lower prescribed dose, such as PI + EBRT, rather than PI alone.

Dosimetric comparison of CT-guided iodine-125 seed stereotactic brachytherapy and stereotactic body radiation therapy in the treatment of NSCLC

This study aimed to assess the dosimetric differences between iodine-125 seed stereotactic brachytherapy (SBT) and stereotactic body radiation therapy (SBRT) in the treatment of non-small cell lung cancer (NSCLC). An SBT plan and an SBRT plan were generated for eleven patients with T1-2 NSCLC. Prescription of the dose and fractionation (fr) for SBRT was 48Gy/4fr. The planning aim for SBT was D90 (dose delivered to 90% of the target volume)≥120Gy. Student’s paired t test was used to compare the dosimetric parameters. The SBT and SBRT plans had comparable PTV D90 (104.73±2.10Gyvs.107.64±2.29Gy), and similar mean volume receiving 100% of the prescription dose (V100%) (91.65% vs.92.44%, p = 0.410). The mean volume receiving 150% of the prescribed dose (V150%) for SBT was 64.71%, whereas it was 0% for SBRT. Mean heterogeneity index (HI) deviation for SBT vs. SBRT was 0.73 vs. 0.19 (p<0.0001), and the mean conformity index (CI) for SBT vs. SBRT was 0.77 vs. 0.81 (p = 0.031). The mean lung doses (MLD) in SBT were significantly lower than those in SBRT (1.952±0.713 vs. 5.618±2.009, p<0.0001). In conclusion, compared with SBRT, SBT can generate a comparable dose within PTV, while the organs at risk (OARs) only receive a very low dose. But the HI and CI in SBT were lower than in SBRT.

Dosimetry Verification of 125I Seeds Implantation With Three-Dimensional Printing Noncoplanar Templates and CT Guidance for Paravertebral/Retroperitoneal Malignant Tumors

OBJECTIVE

To compare dose distributions of postoperative plans with preoperative plans for radioactive seed implantation of paravertebral/retroperitoneal tumors assisted by 3-dimensional printing noncoplanar templates and computed tomography.

METHODS

Sixteen patients with paravertebral/retroperitoneal tumors (21 lesions) underwent radioactive seed implantation with 3-dimensional printing noncoplanar templates. Prescribed dose was 110 to 160 Gy. We compared the dose distribution of the postoperative plan with the preoperative plan. Dose parameters were D90, minimum peripheral dose, V100, V150, conformal index and external index of the target volume, and the dose received by 2 cm³ of normal tissue of organs at risk (spinal cord, aorta, and kidney).

RESULTS

Sixteen 3-dimensional printing noncoplanar templates were produced for 21 treatment areas. Mean gross tumor volume (preoperative) of patients was 61.1 cm³, mean needle number was 17, mean number of implanted ¹²⁵I seeds was 65, and mean D90 of postoperative target area (gross tumor volume) was 131.1 Gy. Actual number of seeds postbrachytherapy increased by 1 to 12 in 8 cases. For postoperative plans, the mean D90, minimum peripheral dose, V100, V150 was 131.1 Gy, 67.1 Gy, 90.2%, and 64.1%, respectively, and 135.0 Gy, 64.7 Gy, 90.9%, and 64.1%, respectively, in preoperative plans. Comparing with the preplanned cases, the dose of the target volume was slightly lower and the high-dose area of the target volume was larger in postoperative cases, but the difference was not statistically significant (P > .05). Actual dose conformity of the target volume was lower than preplanned, and the difference was statistically significant (P = .005).

CONCLUSION

Three-dimensional printing noncoplanar templates can provide good accuracy for positioning and direction in radioactive seed implantation.

Robot-assisted brachytherapy of the bladder with long distance support using video conferencing

PURPOSE

The frontline treatment for localized muscle-invasive bladder carcinoma (MIBC) is radical cystectomy. However, a significant percentage of this population is elderly with either severe co-morbidities or suboptimal general health, increasing the per- and post-operative risk when undergoing a radical cystectomy. Conservative treatment options have been implemented such as robot-assisted laparoscopic brachytherapy (RALB), a minimally invasive therapeutic approach ensuring excellent results in terms of local control, survival, and low morbidity. The treatment was supported successfully long distance using videoconferencing by an expert group from the Netherlands.

MATERIAL AND METHODS

An 81-year-old man was treated with RALB. The patient was submitted to external beam radiotherapy (EBRT) in a total dose of 40 Gy in 20 fractions. A partial cystectomy followed by implantation of three catheters along the scar and brachytherapy was completed. A total dose of 25 Gy in 10 fractions was administered with dose points calculated at 5 mm from the catheters.

RESULTS

Dose planning was characterized by an homogeneity index of 62.3% and overdose index of 19.7%. Other conformity indexes were analyzed. Patient was discharged at the fourth day after the procedure. The clinical response after 6 months was documented.

CONCLUSIONS

The previously reported good rates of tumor control and survival, and the excellent tolerance and low morbidity support RALB as a promising approach for selected groups of patients with localized MIBC. This case illustrates the ability to expand efficiently this technique, particularly among inexperienced medical teams.

Dosimetry verification of radioactive seed implantation for malignant tumors assisted by 3D printing individual templates and CT guidance

OBJECTIVE

We compared the dose distributions of postoperative plans with preoperative plans for 3D printing template-assisted radioactive seed implantations.

METHODS

A total of 14 patients with malignant tumors enrolled in the study. The dose parameters included D90, minimum peripheral dose, V100, V150, and V200. The statistical method was the paired t-test.

RESULTS

There was no significant difference in P values between the two groups for all parameters except for V100.

CONCLUSIONS

The 3D printing guide template can provide good accuracy for radioactive seed implantation.

An open-source genetic algorithm for determining optimal seed distributions for low-dose-rate prostate brachytherapy

PURPOSE

An open source optimizer that generates seed distributions for low-dose-rate prostate brachytherapy was designed, tested, and validated.

METHODS

The optimizer was a simple genetic algorithm (SGA) that, given a set of prostate and urethra contours, determines the optimal seed distribution in terms of coverage of the prostate with the prescribed dose while avoiding hotspots within the urethra. The algorithm was validated in a retrospective study on 45 previously contoured low-dose-rate prostate brachytherapy patients. Dosimetric indices were evaluated to ensure solutions adhered to clinical standards. The SGA performance was further benchmarked by comparing solutions obtained from a commercial optimizer (inverse planning simulated annealing [IPSA]) with the same cohort of 45 patients.

RESULTS

Clinically acceptable target coverage by the prescribed dose (V100) was obtained for both SGA and IPSA, with a mean ± standard deviation of 98 ± 2% and 99.5 ± 0.5%, respectively. For the prostate D90, SGA and IPSA yielded 177 ± 8 Gy and 186 ± 7 Gy, respectively, which were both clinically acceptable. Both algorithms yielded reasonable dose to the rectum, with V100 < 0.3 cc. A reduction in dose to the urethra was seen using SGA. SGA solutions showed a slight prostate volume dependence, with smaller prostates (<25 cc) yielding less desirable, although still clinically viable, dosimetric outcomes. SGA plans used, on average, fewer needles than IPSA (21 vs. 24, respectively), which may lead to a reduction in urinary toxicity and edema that alters post-implant dosimetry.

CONCLUSIONS

An open source SGA was validated that provides a research tool for the brachytherapy community.

Dosimetric comparison of volume-based and inverse planning simulated annealing-based dose optimizations for high-dose rate brachytherapy

The aim of this study was to compare the clinical benefits of inverse planning simulated annealing (IPSA)-based optimization over volume-based optimization for high-dose rate (HDR) cervix interstitial implants. Overall, 10 patients of cervical carcinoma were considered for treatment with HDR interstitial brachytherapy. Oncentra Master Plan brachytherapy planning system was used for generating 3-dimensional HDR treatment planning for all patients. All patient treatments were planned using volume-based optimization and inverse planning optimization (IPSA). The parameters V100, V150, and V200 for the target; D(2 cm³) of bladder, rectum, and sigmoid colon; and V80 and V100 for bladder, rectum, and sigmoid colon were compared using dose-volume histograms (DVHs). The conformity index (CI), relative dose homogeneity index, overdose volume index (ODI), and dose nonuniformity index (DNR) were computed from cumulative DVHs. Good target coverage for prescription dose was achieved with volume-based optimization as compared with IPSA-based dose optimization. Homogeneity was good with the IPSA-based technique as compared with the volume-based dose optimization technique. Volume-based optimization resulted in a higher CI (with a mean value of 0.87) compared with the IPSA-based optimization (with a mean value of 0.76). ODI and DNR are better for the IPSA-based plan as compared with the volume-based plan. Mean doses to the bladder, rectum, and sigmoid colon were least with IPSA. IPSA also spared the critical organs but with considerable target conformity as compared with the volume-based plan. IPSA significantly reduces overall treatment planning time with improved reduced doses to the organs at risk compared with the volume-based optimization treatment planning method.

Interstitial brachytherapy for bladder cancer with the aid of laparoscopy

Since 2009, 40 patients with a T1/T2 bladder cancer have been treated at ARTI with interstitial brachytherapy via laparoscopy. Under general anaesthesia, the tumour area is implanted under cystoscopic control with the aid of a laparoscope, and instruments are attached to the Da Vinci robot. Mapping is then done via a simulator photo and a CT scan. With this method, the patient has fewer complications and the average hospitalization time is halved, while a consistent quality of implant is maintained. This method is also associated with a major reduction in the number of problems that can be attributed to the accessibility of the catheter.

Dosimetric and clinical outcome in image-based high-dose-rate interstitial brachytherapy for anal cancer

PURPOSE

To evaluate dosimetric and clinical outcome in patients of anal cancer treated with image-based interstitial high-dose-rate brachytherapy following chemoradiation.

METHODS AND MATERIALS

Sixteen patients with anal cancer were treated with chemoradiation followed by brachytherapy boost with image-based high-dose-rate interstitial brachytherapy from January 2007 to June 2011. Two brachytherapy dose schedules were used: 21 Gy in seven fractions and 18 Gy in six fractions depending on response to chemoradiation. CT scan was done after placement of needles for confirmation of placement and treatment planning. Target volume was contoured on CT scans. Volumetric quality indices and dose parameters were calculated.

RESULTS

The mean clinical target volume was 17.7 ± 4.98 cm(3), and the median overall tumor size was 4.2cm (3.4-5cm). The mean values of coverage index, dose homogeneity index, overdose volume index, dose non-uniformity ratio, and conformal index were 0.94, 0.83, 0.21, 0.37, and 0.88, respectively. With a median followup of 41 months (range, 20-67.2 months), preservation of the anal sphincter was achieved in 14 patients. The 1- and 2-year local control rates were 93.8% and 87.5%, respectively. Treatment was well tolerated and none of the patients developed Grade 3 or higher late toxicity.

CONCLUSIONS

The combination of external beam radiotherapy with interstitial brachytherapy increases the dose to the tumor volume and limits the volume of irradiated normal tissue, thereby decreasing late toxicity. The use of image-based treatment planning provides better dose conformality with reduced toxicity and helps to prevent a geographic miss.

Dosimetric analysis and comparison of IMRT and HDR brachytherapy in treatment of localized prostate cancer

Radical radiotherapy is one of the options for the management of prostate cancer. In external beam therapy, 3D conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) are the options for delivery of increased radiation dose, as vital organs are very close to the prostate and a higher dose to these structures leads to an increased toxicity. In brachytherapy, low dose rate brachytherapy with permanent implant of radioactive seeds and high dose rate brachytherapy (HDR) with remote after loaders are available. A dosimetric analysis has been made on IMRT and HDR brachytherapy plans. Ten cases from each IMRT and HDR brachytherapy have been taken for the study. The analysis includes comparison of conformity and homogeneity indices, D100, D95, D90, D80, D50, D10 and D5 of the target. For the organs at risk (OAR), namely rectum and bladder, V100, V90 and V50 are compared. In HDR brachytherapy, the doses to 1 cc and 0.1 cc of urethra have also been studied. Since a very high dose surrounds the source, the 300% dose volumes in the target and within the catheters are also studied in two plans, to estimate the actual volume of target receiving dose over 300%. This study shows that the prescribed dose covers 93 and 92% of the target volume in IMRT and HDR brachytherapy respectively. HDR brachytherapy delivers a much lesser dose to OAR, compared to the IMRT. For rectum, the V50 in IMRT is 34.0cc whilst it is 7.5cc in HDR brachytherapy. With the graphic optimization tool in HDR brachytherapy planning, the dose to urethra could be kept within 120% of the target dose. Hence it is concluded that HDR brachytherapy may be the choice of treatment for cancer of prostate in the early stage.

Long term results of PDR brachytherapy for lip cancer

PURPOSE

To evaluate the long time outcome with regard to local tumour control and side effects of a pulsed dose rate (PDR) monobrachytherapy of primary or recurrent cancer of the lip.

MATERIAL AND METHODS

Between 1995 and 2007 we treated 43 patients with primary or recurrent clinical T1-T3N0 lip cancers. There were 22 T1 patients (51%), 16 T2 (37%) and 5 T3 cases (12%). A median dose of 60 (55-66) Gy was given, depending on the tumour volume. The PDR treatment was delivered with 0.83 Gy/pulse every second hour for 5.5-6.5 days. The patients were followed for a median of 55 (1-158) months.

RESULTS

The 2-, 5- and 10-year rates of actuarial local control were 97.6%, 94.5% and 94.5%, overall survival 88.0%, 58.9% and 39.1%, disease free survival 92.7%, 86.4% and 86.4% respectively. The regional control rate was 93%. One patient (2%) developed distant metastases. A dosimetrical analysis showed a mean treated volume of 14.9 (3.0-56.2) cm3. Long-term side effects were mild and the cosmetic outcome excellent, except for 1 case (2%) of soft tissue necrosis and 1 case (2%) of osteoradionecrosis.

CONCLUSIONS

Local outcome is excellent and similar to other published studies of continuous low dose rate (cLDR) brachytherapy.

Quality assessment of interstitial implants in high- dose- rate brachytherapy after lumpectomy in patients of early stage breast cancer

To assess the quality of high dose rate (H,D,R.) interstitial implants in breast cancer by using different volumetric indices and correlating them with skin and subcutaneous tissue toxicity. Out of 15 patients who were selected for interstitial implants after undergoing breast conservation surgery, five were treated radically with 34 Gy in 10 fractions in 5 days @ 3.4 Gy # twice daily and 10 patients recieved boost dose of 12 Gy in 4 fractions @ 3 Gy /# twice daily. The median follow up was 15 months. During each follow up assessment of late skin and subcutaneous tissue toxicity as per RTOG criteria was done . Various dosimetric indices were analysed. Dose Volume Histogram for dose per unit volume of skin for 10cc,5cc,2cc,1cc,0.1cc and 0.01cc was calculated. Best estimates and correlation of toxicity was revealed by assessment of Dose Nonuniformity Ratio(DNR) which also correlated well with geometry defining indices like Uniformity Index (UI).Volumetric assessment of skin dose for less than 2 cc correlated most with toxicity. DNR and UI can help us to assess and correlate late skin and subcutaneous tissue toxicity and thus serve useful to determine the quality of implant.

Pulsed dose rate brachytherapy as the boost in combination with external beam irradiation in base of tongue cancer. Long-term results from a uniform clinical series

PURPOSE

To evaluate long time outcome with regard to local tumour control, side effects and quality of life of combined pulsed dose rate (PDR) boost and hyperfractionated accelerated external beam radiotherapy (EBRT) for primary base of tongue (BOT) cancers.

MATERIAL AND METHODS

Between 1994 and 2007, the number of 83 patients were treated with primary T1-T4 BOT cancers. Seven patients (8%) were T1-2N0 (AJCC stage I-II) and 76 (92%) patients were T1-2N+ or T3-4N0-2 (AJCC stage III-IV). The mean estimated primary tumour volume was 15.4 (1-75) cm3. EBRT was given with 1.7 Gy bid to 40.8 Gy to primary tumour and bilateral neck lymph nodes in 2.5 weeks. PDR boost of 35 Gy and a neck dissection in clinical node positive case was performed 2-3 weeks later. The patients were followed for a median of 54 (2-168) months.

RESULTS

The 2-, 5- and 10-years rates of actuarial local control were 91%, 89% and 85%, overall survival 85%, 65% and 44%, disease free survival 86%, 80% and 76%, respectively. The regional control rate was 95%. Six patients (7%) developed distant metastases. A dosimetric analysis showed a mean of 100% isodose volume of 58.2 (16.7-134) cm3. In a review of late complications 11 cases of minor (13%) and 5 of major soft tissue necroses (6%), as well as 6 cases of osteoradionecroses (7%) were found. The patients median subjective SOMA/LENT scoring at last follow up was as follow: grade 0 for pain and trismus, grade 1 for dysphagia and taste alteration, and grade 2 for xerostomia. Global visual-analogue-scale (VAS) scoring of quality of life was 8.

CONCLUSION

Local and regional tumour control rate was excellent in this treatment protocol. The data shows the PDR boost as at least as effective as published continuous low dose rate (CLDR) results.

Dosimetric comparison of various optimization techniques for high dose rate brachytherapy of interstitial cervix implants

HDR brachytherapy treatment planning often involves optimization methods to calculate the dwell times and dwell positions of the radioactive source along specified afterloading catheters. The purpose of this study is to compare the dose distribution obtained with geometric optimization (GO) and volume optimization (VO) combined with isodose reshaping. This is a retrospective study of 10 cervix HDR interstitial brachytherapy implants planned using geometric optimization and treated with a dose of 6 Gy per fraction. Four treatment optimization plans were compared: geometric optimization (GO), volume optimization (VO), geometric optimization followed by isodose reshape (GO_IsoR), and volume optimization followed by isodose reshape (VO_IsoR). Dose volume histogram (DVH) was analyzed and the four plans were evaluated based on the dosimetric parameters: target coverage (V100), conformal index (COIN), homogeneity index (HI), dose nonuniformity ratio (DNR) and natural dose ratio (NDR). Good target coverage by the prescription dose was achieved with GO_IsoR (mean V100 of 88.11%), with 150% and 200% of the target volume receiving 32.0% and 10.4% of prescription dose, respectively. Slightly lower target coverage was achieved with VO_IsoR plans (mean V100 of 86.11%) with a significant reduction in the tumor volume receiving high dose (mean V150 of 28.29% and mean V200 of 7.3%). Conformity and homogeneity were good with VO_IsoR (mean COIN=0.75 and mean HI=0.58) as compared to the other optimization techniques. VO_IsoR plans are superior in sparing the normal structures while also providing better conformity and homogeneity to the target. Clinically acceptable plans can be obtained by isodose reshaping provided the isodose lines are dragged carefully.

PACS number: 87.53 Bn

Qualitative dosimetric and radiobiological evaluation of high - dose - rate interstitial brachytherapy implants

Radiation quality indices (QI), tumor control probability (TCP), and normal tissue complication probability(NTCP) were evaluated for ideal single and double plane HDR interstitial implants. In the analysis, geometrically-optimized at volume (GOV) treatment plans were generated for different values of inter-source-spacing (ISS) within the catheter, inter-catheter-spacing (ICS), and inter-plane-spacing (IPS) for single - and double - plane implants. The dose volume histograms (DVH) were generated for each plan, and the coverage volumes of 100%, 150%, and 200% were obtained to calculate QIs, TCP, and NTCP. Formulae for biologically effective equivalent uniform dose (BEEUD), for tumor and normal tissues, were derived to calculate TCP and NTCP. Optimal values of QIs, except external volume index (EI), and TCP were obtained at ISS = 1.0 cm, and ICS = 1.0 cm, for single-plane implants, and ISS = 1.0 cm, ICS = 1.0 cm, and IPS = 0.75 to 1.25 cm, for double - plane implants. From this study, it is assessed that ISS = 1.0 cm, ICS = 1.0 cm, for single - plane implant and IPS between 0.75 cm to 1.25 cm provide better dose conformity and uniformity.

Comprehensive I-125 multi-seed comparison for prostate brachytherapy: Dosimetry and visibility analysis

PURPOSE

To compare the visibility of different manufacturers I-125, seeds, and to investigate the effect of differences in dosimetry on treatment planning.

MATERIALS AND METHODS

Oncura Oncoseed, Oncura Echoseed, IBT Intersource, Bebig Isoseed and Nucletron Selectseed were investigated. The point dose at increasing distances from each seed type was calculated for three different angles; theta=0 degrees, 45 degrees and 90 degrees (where theta=0 degrees lies parallel to seed length). 10 patient plans were used to assess the effect of a change in dosimetry on treatment planning and quality of prostate and rectum implant indices such as Vp100, Vp200, Dp90, Vr100 and Vr69. All implant indices and dosimetry data were compared to Oncoseed. Visibility under X-ray, fluoroscopy, CT and MRI was investigated using prostate phantoms created in-house. Statistical significance was calculated using paired two-tailed t-tests.

RESULTS

Dosimetric analysis was carried out for seeds of the same source strength. Differences in dose increase closer to the centre of each source, with the largest changes occurring for the angle theta=0 degrees. Selectseed and Isoseed seed types provide a consistently lower dose in all three directions. Changes to Vp100 are small and statistically insignificant for all seeds except Selectseed which shows a statistically significant decrease of 0.04% (p=0.02). Changes to Vp150 and Vp200 are statistically significant (p<0.01), with Intersource showing the greatest increase in both values. Selectseed shows a decrease in both Vp150 and Vp200. Echoseed shows an increase in both Vp150 and Vp200. Changes to D90 are statistically significant (p<0.01), with Intersource showing the greatest increase, followed by Isoseed then Echoseed. Selectseed shows a decrease in D90. For Vr100 there is no statistically significant change for any seed type. However, all seeds except Selectseed show a statistically significant increase in the value of Vr69, with Intersource showing the greatest increase. On fluoroscopy and X-ray images, Intersource seeds appear least visible, Echoseed and Oncoseed are similar, and Isoseed and Selectseed are most visible. Ultrasound greyscale beam profiles show that all seed images have a FWHM larger than the Oncoseed image. The CT greyscale beam profiles are similar for all seed images. The MRI signal voids are similar for all seed images except Intersource which shows a larger signal void.

CONCLUSIONS

The greatest changes to point dose occur at very close distances to the seeds. Changing seed type may require a treatment replan to maintain satisfactory DVH criteria. Visibility on US and CT is similar, though it may vary on MRI, X-ray and fluoroscopy.

Quality of interstitial PDR-brachytherapy-implants of head-and-neck-cancers: predictive factors for local control and late toxicity?

BACKGROUND AND PURPOSE

Parameters and indices related to the implant geometry in use for describing the quality of volume implants in interstitial brachytherapy were developed on the basis of LDR-brachytherapy. The aim of our study was to evaluate their usefulness for predicting late toxicity and local control in the PDR-brachytherapy of head-and-neck-tumors.

PATIENTS AND METHODS

Between January 2000 and October 2004, 210 patients were treated with PDR-brachytherapy which was administered either postoperatively or as definitive treatment. Brachytherapy was used as sole treatment in some cases while in others a combination with EBRT was used. For assessment of quality of implants we analyzed the following indices and parameters using the univariate chi2 test and multivariate logistic regression analysis: V85, V120 and V150 (volume enclosed by the surface of the 85%-, 120%- and 150%-isodose), UI (uniformity index), QI (quality index), HI (homogeneity index), VGR (volume gradient ratio), DNR (dose non-uniformity ratio), LD (low dose), HD (high dose), PD (peak dose) and the intersource spacing.

RESULTS

After a median follow-up of 24 months (4-50) the rate of - usually transient - soft tissue necrosis (STN) was 11%, osteoradionecrosis (ORN) was seen in 7.6% of cases and local relapse occurred in 7% of cases. Univariate analysis shows a significant influence on the development of soft tissue necrosis for V85, and on osteoradionecrosis for HD and PD. In the multivariate analysis a correlation between soft tissue necrosis and QI was found. For local control a correlation with QI, VGR and minimal tube distance was found using univariate analysis.

CONCLUSIONS

Using interstitial PDR-brachytherapy in head-and-neck-tumors the probability of local control and of the development of soft tissue necrosis or osteoradionecrosis is dependent on dose and volume parameter like the volume of the reference isodose, the high and peak dose values, on the homogeneity of the dose distribution, quantified by the quality index or the volume gradient ratio as well on the minimal tube distance.

Dosimetric comparison of interactive planned and dynamic dose calculated prostate seed brachytherapy

PURPOSE

To compare the dosimetrical results of an interactive planning procedure and a procedure based on dynamic dose calculation for permanent prostate brachytherapy.

MATERIALS AND METHODS

Between 6/2000 and 11/2005, 510 patients underwent (125)I implants for T1-T2 prostate cancer. Before 4/2003, 187 patients were treated using an interactive technique that included needle updating. After that period, 323 patients were treated with a more refined dynamic technique that included constant updating of the deposited seed position. The comparison is based on postimplant dose - volume parameters such as the V(100) and d(90) for the target, V(100)(r) for the rectum and d(10)(u) for the urethra. Furthermore, the target volume ratios (TVR identical with V(100)(body)/V(100)), and the homogeneity indices (HI identical with [V(100)-V(150)]/V(100)) were calculated as additional quality parameters.

RESULTS

The dose outside the target volume was significantly reduced, the V(100)(r) decreased from 1.4 cm(3) for the interactive technique to 0.6 cm(3) for the dynamic technique. Similarly the mean TVR reduced from 1.66 to 1.44. In addition, the mean V(100) increased from 92% for the interactive procedure to 95% for the dynamic procedure. More importantly, the percentage of patients with a V(100) < 80% reduced from 5% to 1%. A slight decline was observed with regard to the d(10)(u) (136% vs. 140%) and the HI (0.58 vs. 0.51).

CONCLUSION

The dynamic implant procedure resulted in improved implants. Almost ideal dose coverage was achieved, while minimizing the dose outside the prostate.

Comparison of (125)I stereotactic brachytherapy and LINAC radiosurgery modalities based on physical dose distribution and radiobiological efficacy

The goal of this study was to make a comparison between stereotactic brachytherapy implants and linear accelerator-based radiosurgery of brain tumors with respect to physical dose distributions and radiobiological efficacy. Twenty-four treatment plans made for irradiation of brain tumors with low-dose-rate (125)I brachytherapy and multiple-arc LINAC-based radiosurgery were analyzed. Using the dose-volume histograms and the linear-quadratic model, the brachytherapy doses were compared to the brachytherapy-equivalent LINAC radiosurgery doses with respect to the predicted late effects of radiation on normal brain tissue. To characterize the conformity and homogeneity of dose distributions, the conformal index, external volume index, and relative homogeneity index were calculated for each dose plan and the mean values were compared. The average tumor volume was 5.6 cm(3) (range: 0.1-19.3 cm(3)). At low doses, the calculated radiobiological late effect on normal tissue was equivalent for external-beam and brachytherapy dose delivery. For brachytherapy at doses greater than 30 Gy, the calculated equivalent dose to normal tissues was less than for external-beam radiosurgery. However, the dose-calculated homogeneity was better for the LINAC radiosurgery, with a mean relative homogeneity index of 0.62 compared to the calculated value of 0.19 for the brachytherapy (P=0.0002). These results are only predictions based on calculations concerning normal tissue tolerance. More data and research are needed to understand the clinical relevance of these findings.

Prostate brachytherapy postimplant dosimetry: A comparison of suture-embedded and loose seed implants

PURPOSE

To compare postimplant dosimetry and seed embolization rates for prostate brachytherapy implants using suture-embedded and loose seeds.

METHODS AND MATERIALS

Dosimetric analysis of the whole prostate, prostate quadrants, rectum, and surrogate urethra was performed on 54 loose seed and 81 RAPIDStrand (RS) patients. Seed embolization rates were determined from chest radiographs.

RESULTS

Whole prostate V100 and D90 did not differ significantly for the loose seed (V100 = 90.5%, D90 =153.2 Gy) and RS groups (V100 = 91.5%, D90 = 151.6 Gy) (p = 0.43 and 0.65, respectively), but V150, V200, and contiguous V200 were higher (p < or = 0.003) for the RS group (59.9%, 28.3%, and 23.2%, respectively) than the loose seed group (52.5%, 22.8%, and 16.1%, respectively). Extraprostatic measures (conformity index and external index) were also different at the p < 0.05 level. The embolization rate was 40% in the loose seed group and 14% in the RS group.

CONCLUSIONS

The most significant difference between the two study groups was a decrease in the embolization rate. Although some statistically significant changes in postimplant dosimetry were observed, they were nevertheless small.

Evaluation of anatomy-based dwell position and inverse optimization in high-dose-rate brachytherapy of prostate cancer: a dosimetric comparison to a conventional cylindrical dwell position, geometric optimization, and dose-point optimization

BACKGROUND AND PURPOSE

To compare treatment planning methods in high-dose-rate (HDR) brachytherapy of prostate cancer. In particular, to assess quantitatively the dosimetric superiority, if any, of the anatomy-based dwell position (ABDP) and inverse optimization (IO) over the conventional cylindrical dwell position (CDP), geometric optimization (GO), and dose-point optimization (DO) in terms of the determination of dwell positions and dwell times.

PATIENTS AND METHODS

Between September 2002 and April 2003, 10 cases of treatment-planning CT images were taken for external radiotherapy for prostate cancer. Treatment planning computer software and the CT data were used to create hypothetical HDR brachytherapy applicator needles, which were properly implanted in the prostate. Six different plans including IO with ABDP (IO(ABDP)), IO with CDP (IO(CDP)), GO with ABDP (GO(ABDP)), GO with CDP (GO(CDP)), DO with ABDP (DO(ABDP)), and DO with CDP (DO(CDP)) were made for each case, that is, 60 plans in total. All plans were normalized so that the D(95) should be equal to 100% of the prescribed dose. Dose-volume histograms from all 60 plans were analyzed, and multiple implant quality indices, including CI, EI, DNR, %V(R 75), %V(B 75), and %V(U 150) for each plan, were extracted and compared. Then, the best settings for IO(ABDP) regarding dwell position and dose limit were sought for.

RESULTS

ABDP showed a statistically significantly lower EI (P<0.001), %V(R 75) (P=0.002), and %V(B 75) (P=0.015) than CDP. IO showed a statistically significantly lower %V(U 150) than GO (P=0.009), or than DO (P<0.001). Given a definition that a figure exceeding three-fold of the minimum figure of the index is clinically unacceptable, only in IO(ABDP) all index figures were clinically acceptable, while in the other five plans at least one index figure was unacceptable.

CONCLUSIONS

In the CT-based treatment planning for prostate HDR brachytherapy, ABDP is useful to achieve a high conformity, which leads to a reduction of the doses to the bladder, rectum, and surrounding normal tissue. IO is useful to lower the urethral dose without sacrificing conformity. IO(ABDP) is recommended on the basis of the current study. However, this conclusion has been drawn from the idealized hypothetical settings, and some possibility remains that this conclusion is not always applicable to the real implants.

Quality of life of patients after permanent prostate brachytherapy in relation to dosimetry

PURPOSE

To investigate changes in quality of life (QoL) after permanent prostate brachytherapy and to correlate these changes with postimplant dosimetry based on magnetic resonance (MR) images.

METHODS AND MATERIALS

For this study, 127 patients with low-stage prostate cancer and treated with brachytherapy received a QoL questionnaire at five time points: before treatment and at 4 weeks, 6 months, 1 year, and 2 years after treatment. The questionnaire included the RAND-36 generic health survey, the cancer-specific European Organization for Research and Treatment of Cancer (EORTC) core questionnaire, the tumor-specific EORTC prostate cancer module, and the American Urological Association symptom index. Postimplant dosimetry was based on registered T1 spin echo transversal, T2 turbo spin echo transversal, and T2 turbo spin echo sagittal MR images and CT images taken 4 weeks after implantation of the iodine-125 seeds. Calculated parameters were prostate volume, prostate volume receiving 100% (V100) and 150% (V150) dose, dose to 90% of the prostate volume (D90), maximum dose in 1-, 2-, and 5-cm3 rectum volume, distance between prostate and anterior rectum wall, and the maximum dose in 1%, 2%, and 5% urethra volume. Analysis of variance for repeated measures was used for comparison of the means of all variables in the different questionnaires. Linear regression analysis (stepwise) was used to investigate the correlations between QoL parameters and dosimetry parameters.

RESULTS

On average, only the QoL at 4 weeks after implant was significantly different from (worse than) the QoL at the other time points. Regression analysis showed a significant correlation between changes in bowel problems and the maximum dose in 2-cm3 rectum volume, between changes in urinary symptoms and prostate volume, and between changes in urinary problems and the D90 value of the prostate.

CONCLUSIONS

The QoL for patients with permanent prostate implants was worse in the first months after treatment but returned to baseline values 1 year after implant. Significant correlations were found between dose distribution and QoL.