Brachytherapy Catheters Research Articles

Pilot Evaluation of Perioperative High Dose Rate Brachytherapy in Head Neck Cancers.

Perioperative high dose rate brachytherapy involves insertion of brachytherapy catheter over the tumor bed during surgical removal of disease followed by radiation in the postoperative period. It has applications in radiotherapy dose escalation or reirradiation and for extending the surgical margins. We report here initial results of treatment in five cases of locally advanced head and neck cancers.

Improving Ultrasound Visualization of Catheters During Interstitial Brachytherapy

Interstitial brachytherapy utilizes catheters to deliver high doses of radiation directly to target tissues. Proper catheter placement is vital to successful treatment and patient outcome. To ensure effective internal guidance, catheters are often positioned under real-time ultrasound (US) in the operating room, with post-operative confirmation using axial imaging. However real-time catheter localization is often difficult due to poor catheter visualization, which can result in ineffectual treatment, reduced organ-sparing, or catheter intrusion into surrounding organs. In the current space for this oncological technique, there are no devices or methods that aim to improve the visualization of catheters which leverage the convenience and accessibility of real-time ultrasound, hindering the optimization of procedural outcomes. To address this need, our team designed a piezo material-integrated medical accessory to integrate the qualitative visualization of color Doppler US into interstitial brachytherapy procedures. The device transduces low-magnitude vibration to brachytherapy catheters to be detected in tissue under real-time B-mode US. Upon activation, the device propagates vibrations down the length of brachytherapy catheters, allowing color Doppler to detect and display repeated, internal movements to assist the operator in catheter placement. Active adjustability over the voltage output using a simple circuit with potentiometer control allows the user to directly control the magnitude and frequency of vibration, offering real-time visualization during interstitial brachytherapy. Pivotal elements of this design include a noninvasive integration into existing brachytherapy workflows, a reproducible and low-cost 3D-printed design, compatibility with real-time US catheter visualization, and highly specific control over the magnitude of Doppler visualization with catheter detachability and dial-regulated voltage/vibration adjustment. The device is able to qualitatively increase the visualization of brachytherapy catheters in a simulated brachytherapy procedure using a custom US phantom at moderate to extreme operational depths, while also staying within safety thresholds set by international standards for medical/electronic/handheld accessories in regards to heat generation, housing weight, and vibrational exposure. Results obtained using an obstructive US phantom with 10-15 cm depth, which consists of fruits, airway through the phantom, and multiple catheters in a localized area, allowed us to clearly distinguish the catheter of interest from the rest of the structures, even in the presence of highly intrusive noise and shadowing CONCLUSION: Brachytherapy catheter visualization can be improved using low-magnitude vibration transmitted through the brachytherapy catheter detected under real-time B-mode US. Further research and clinical testing are ongoing.

Toxicity and Dosimetric Analysis of Reirradiation of Head and Neck Cancers with High Dose Rate Brachytherapy

Reirradiation (reRT) of recurrent or second primary head and neck cancers (HNC) after prior curative-intent external beam radiotherapy (EBRT) has historically achieved local control (LC) rates of 40-50% and been associated with high grade toxicity rates estimated at 25-50%. This study evaluated the hypothesis that patients with small reRT target volumes could be selected for high dose rate brachytherapy (HDR-BT) reRT and achieve similar LC without excess toxicity. Included were all patients with HNC squamous cell carcinoma treated with HDR-BT after having previously received curative-intent EBRT for primary HNC from 2000-2021. Patients were selected by a multidisciplinary tumor board to be appropriate candidates for HDR-BT reRT without EBRT generally for definitive or adjuvant treatment of small primary tumors without neck nodal metastases. Univariate analysis was performed using the logistic regression model. Survival outcomes were estimated with the Kaplan Meier method. Twenty-three patients were evaluated. Median follow up time was 19mo. Median age at time of HDR-BT was 64 years. Thirteen patients (57%) were treated for recurrent HNC, of which 7 were in the oral cavity (OC) and 6 were the oropharynx (OPX). Ten patients (43%) were treated for a second primary HNC, of which 5 were in the OC and 5 were in the OPX. Median time from completion of EBRT to HDR-BT was 41 (IQR 14-73) mo. Within their reRT course, 11 patients (48%) were treated with HDR-BT after resection, 9 patients (39%) received concurrent hyperthermia, and 7 patients (30%) received chemotherapy. HDR-BT regimens included 600cGy x5 (N = 11), 600cGy x6 (N = 6), 450cGy x8 (N = 1), 1500cGy x1 (N = 1),1000cGy x1 (N = 1), 500cGy x8 (N = 1), and 700cGy x5 (N = 1). One patient who was treated with two implants received 450cGy x 3 followed by 475cGy x5. A median of 5 brachytherapy catheters were used. Actuarial 2-year LC and overall survival rate was 68% and 62%, respectively. Of the 17 HDR-BT reRT plans available for review, median (IQR) target volume was 15.8 (10.6-34.9) cc. Median (IQR) target V100% was 90.6 (89.4-90.0)%, V150% was 50.5 (49.7-54.4)%, and V200% was 25.4 (23.8-29.0)%. Median (IQR) target D90% was 30.1 (29.8-35.5) Gy, and median D1cc was 116.4 (100.5-171.4) Gy. The mandible dose [median (IQR)] was D2cc:15.1(9.48-18.9) Gy; D1cc:16.9(11.1-21.3) Gy; and D1%:18.8(13.4-22.7) Gy. Nine of the 23 patients (39%) experienced ≥G3 toxicity including fistula, soft tissue necrosis, osteoradionecrosis, ulcer, hemorrhage, and dysphagia requiring a chronic feeding tube. Target D90% was associated with ≥G3 toxicity (p = 0.045). For D90% greater than the median of 30Gy, 45% ≥G3 toxicity was observed. This study suggests that HDR-BT for reRT of small recurrent or second primary HNC can provide similar LC without excess high-grade toxicities as compared to historical outcomes with EBRT reRT. Delivery of equivalent doses higher than 30Gy in 5 fractions should be approached with caution.

PP03 Presentation Time: 3:48 PM: Realtime Ir-192 Source Localization Employing Spatio-Temporal Sensing along Brachytherapy Catheter

PP03 Presentation Time: 3:48 PM: Realtime Ir-192 Source Localization Employing Spatio-Temporal Sensing along Brachytherapy Catheter

Organ sparing treatment for penile cancer using a 3D-printed high-dose-rate brachytherapy applicator

PURPOSEWe present a case study of the treatment of localized squamous cell carcinoma on the glans penis with a custom-fabricated high-dose-rate (HDR) brachytherapy applicator. METHODS AND MATERIALSA cylindrically shaped applicator was fabricated with eight embedded channels suitable for standard plastic brachytherapy catheters. An additional custom silicone bolus/sleeve was designed to be used with the 3D-printed applicator to provide an additional offset from the source to skin to reduce the surface dose and for patient comfort. RESULTSThe patient (recurrent cT1a penile cancer) underwent CT simulation, and the brachytherapy plan was created with a nominal prescription dose of 40 Gy in 10 fractions given bidaily to the surface, and 35 Gy at 5 mm depth. Dose coverage to the clinical target volume was 94% (D90). Most fractions were treated with only 5-10 min of setup time. Follow up visits up to 1 year showed no evidence of disease with no significant changes in urinary and sexual function and limited cosmetic detriment to the patient. CONCLUSIONSPatient-specific organ-sparing HDR plesiotherapy using 3D printing technology can provide reliable and reproducible patient setup and may be effective in achieving disease control for superficial penile cancer, although preserving patient quality of life.

A Case Report on Brachytherapy in Extremity Soft Tissue Sarcoma (STS)

STS represents a heterogenous group of malignancies with varying pathological grades, sites of origin and histologies. In the olden days, treatment consisted of resections and amputation which led to significant detriment in quality of life(QoL) and structural functions . Here we present a case of 49 year old patients who came with complaints of painless, progressive swelling in the right upper arm. He underwent WLE followed by intraoperative brachytherapy catheter application. He was then planned for HDR brachytherapy 34 Gy in 10 fractions 4 days following surgery. He tolerated the treatment well, the surgical scar healed by primary intention with no complication during or after the procedure. It can be concluded that brachytherapy in soft tissue sarcoma is a feasible option and an effective modality in the treatment of extremity soft tissue sarcoma with adequate local control.

Applying the column generation method to the intensity modulated high dose rate brachytherapy inverse planning problem

Objective. Intensity modulated high dose rate brachytherapy (IMBT) is a rapidly developing application of brachytherapy where anisotropic dose distributions can be produced at each source dwell position. This technique is made possible by placing rotating metallic shields inside brachytherapy needles or catheters. By dynamically directing the radiation towards the tumours and away from the healthy tissues, a more conformal dose distribution can be obtained. The resulting treatment planning involves optimizing dwell position and shield angle (DPSA). The aim of this study was to investigate the column generation method for IMBT treatment plan optimization. Approach. A column generation optimization algorithm was developed to optimize the dwell times and shield angles. A retrospective study was performed on 10 prostate cases using RapidBrachyMCTPS. At every iteration, the plan was optimized with the chosen DPSA which would best improve the cost function that was added to the plan. The optimization process was stopped when the remaining DPSAs would not add value to the plan to limit the plan complexity. Main results. The average number of DPSAs and voxels were 2270 and 7997, respectively. The column generation approach yielded near-optimal treatment plans by using only 11% of available DPSAs on average in ten prostate cases. The coverage and organs at risk constraints passed in all ten cases. Significance. The column generation method produced high-quality deliverable prostate IMBT plans. The treatment plan quality reached a plateau, where adding more DPSAs had a minimal effect on dose volume histogram parameters. The iterative nature of the column generation method allows early termination of the treatment plan creation process as soon as the dosimetric indices from dose volume histogram satisfy the clinical requirements or if their values stabilize.

A feasibility study of utilizing a cadaveric training model for novel robotic bladder cancer brachytherapy techniques

PurposeThe current standard of care for muscle-invasive bladder cancer is neoadjuvant chemotherapy followed by radical cystectomy with lymph node dissection. Although this treatment provides therapeutic benefit, it is associated with notable morbidity. Bladder sparing techniques, such as concurrent chemo-radiation, are less invasive and prioritize organ preservation in individuals with invasive bladder cancer and offer comparable disease control. High-dose-rate brachytherapy is an emerging paradigm in the management of muscle-invasive bladder cancer. During high-dose-rate brachytherapy, radioactive sources are introduced to the area of the primary tumor through specialized catheters. The specific placement of brachytherapy catheters results in heightened effectiveness of the radiation treatment with less radiation damage to surrounding structures. For bladder-sparing therapies such as brachytherapy to rival radical cystectomy, these techniques need to be refined further by radiation oncologists. ProcedureOne such modality for developing and practicing these techniques is the use of cadaveric models in innovation-focused clinical training facilities, which provide a simulated sterile surgical environment without the concern for extending intraoperative time. Findings and conclusionsThe objective of this technical note is to demonstrate how clinical training facilities such as the Houston Methodist Institute for Technology, Innovation & Education are ideal for the development, testing, and training of novel brachytherapy techniques using cadaveric models. By utilizing a network of similarly innovative training centers, research and development of brachytherapy techniques can be expedited, and novel bladder-sparing treatment methods can be implemented as the standard of care for bladder cancer.

MSPP04 Presentation Time: 4:30 PM: Interstitial Brachytherapy Based Accelerated Partial Breast Irradiation After Oncoplastic Breast Conserving Surgery

<h3>Purpose</h3> Oncoplastic surgical procedures are increasingly being performed in patients undergoing breast conserving surgery (BCS). Due to distortion of breast tissue in breast conserving oncoplastic surgery (BCOS), APBI becomes very challenging. The literature on APBI in BCOS is extremely limited. The aim of our study was to analyze the results of interstitial brachytherapy based APBI in early breast cancer patients who underwent BCOS. <h3>Methods and Materials</h3> Between the period from Jan 2015 to Dec 2020, all patients who underwent APBI following BCS + Type 1 oncoplasty were retrospectively analyzed. Patients with other than Type 1 oncoplastic surgery were excluded from this analysis. The APBI was performed with free hand interstitial brachytherapy implant. CT Scan based treatment planning was done and a HDR dose of 35 Gy/10 fractions/ 5 days (two fractions a day) was prescribed for APBI. Patients were kept on regular follow up for assessing local control and cosmesis. <h3>Results</h3> A total of 60 patients were treated with APBI following BCOS procedure. Median age of the patients was 52 years (range 42-63 years). The median tumor size was 2.5 cm (1-3.5 cm). All the patients were pathological node negative. An average of 11 interstitial brachytherapy catheters were inserted using 2-3 planes. For all patients, dose homogeneity index (DHI) ranged from 0.62-0.92 with a median of 0.84. Median follow-up of entire cohort of patients was 34 months (range 6-84 months). Two patients had ipsilateral breast recurrence and one had systemic metastases. All the patients were alive at the time of analysis. Good-excellent cosmesis was observed in 85% patients. <h3>Conclusion</h3> Our short-term clinical results suggest that interstitial brachytherapy based accelerated partial breast irradiation is feasible after Type 1 oncoplastic breast conserving surgery in selected patients with early breast cancer.

Determination of the Optimal Time for Planning Single-Entry Expandable Catheter Brachytherapy for APBI

<h3>Purpose/Objective(s)</h3> APBI treats early-stage carcinoma in women using HDR with a single-entry catheter device with multiple peripheral struts inserted into the cavity post-lumpectomy. A planning CT (CT_plan) is conducted on the day of device implantation (Day 0) or the day after (Day 1). For an asymmetrical implantation, a change in distance between two struts may be seen from day to day, making the device unstable, with no consensus on when struts stabilize in patients. In this retrospective cohort study, the endpoint is the number of days between device implantation and CT_plan to achieve stability. <h3>Materials/Methods</h3> With IRB approval, we retrospectively reviewed 242 women treated with ABPI using HDR from 2014–2021. Daily CT images were reviewed in 34 patients who had qualitative strut instability and asymmetry. Instability was evaluated by superimposing the CT taken each morning to the CT_plan on the Brachytherapy Planning Software (BPS). CT data were exported to BPS, where the percent change of distance between each strut was calculated and compared to the previous day (Days 0–1, Days 1–2, etc.). The average percent change and Standard Deviation (SD) for all distances for each calendar day were determined. Struts were considered unstable if the average percent change from the previous day was greater than 5%. The information biases inherent in retrospective reviews were accounted for by ensuring no missing data. <h3>Results</h3> Strut stability, in terms of the average percent change in all strut-to-strut distances across all patients, occurs on Day 1 (24 hours after device implantation), significantly dropping from 18% (SD = 27%) to 3.6% (SD = 2.8%). Stability remained on subsequent days (Day 1 and beyond), ranging between 2–5% (Table 1). <h3>Conclusion</h3> An increase in days only results in greater strut stability after 24 hours (Days 0–1), demonstrating that waiting for more than 24 hours after device implantation to complete a CT may not be necessary for those with asymmetric and unstable struts. The implication is that this finding can aid in improving treatment efficiency and decreasing infection risk as less time is needed for the device to be inside the cavity to wait for strut stability.

Feasibility of using polytetrafluoroethylene flexible implant tube for interstitial brachytherapy patients

To design the different Polytetrafluoroethylene (PTFE) based flexible implant tubes using an in-house developed device and to evaluate them for High dose rate (HDR) interstitial brachytherapy using computer tomography images. PTFE hollow tube having a 2 mm (6 French) outer diameter (OD) and 1.4 mm inner diameter (ID) was used to design in-house single and/or double leader flexible catheters for interstitial brachytherapy implant. An in-house Plastic Wire Drawing Plate (PWDP) machine was developed. Customization of PTFE hollow flexible implant tube (FIT) was done through PWDP. Different percentages of BaSO4 (5%, 10%, & 15%) were added to Nylon 6 to make radiopaque button. Various quality assurance tests were performed with the PTFE tubes implanted in the brinjal (phantom) before using them on the patients. That is, coupling of brachytherapy machine transfer tube with flexible PTFE Tubes, CT scan artifacts, tube kinks, breast template, and free-hand compatibility. With the help of the PWDP machine, plastic wires of different lengths were made for single leader and double leader tubes. The different plastic leader ends of 1 cm to 50 cm lengths having 1 mm diameter were created. The radiopaque button of Nylon 6 in circular shape having 1 cm diameter and 0.5 cm thick was created. Developed radiopaque buttons were visible on CT scan images as well as on radiograph images. PTFE tubes of the desired length can be made depending upon the size of the brachytherapy implant and are inexpensive than commercially available flexible implant tubes.

Brachytherapy Drainage Catheter and Chemotherapy for Unresectable Pancreatic Carcinoma Combined with Obstructive Jaundice.

BackgroundMost patients with advanced pancreatic cancer do not have the chance to undergo surgery or chemotherapy because of their poor conditions. Biliary drainage is a palliative treatment to restore liver function and alleviate jaundice, but most patients still face the risk of biliary obstruction in the short term after operation. The purpose of this study is to evaluate the efficacy and safety of brachytherapy drainage catheter (BDC)-combined chemotherapy in the treatment of pancreatic cancer complicated with obstructive jaundice.Patients and MethodsFrom November 2017 and May 2019, 48 patients underwent the BDC or conventional drainage catheter (CDC) intervention with chemotherapy. The outcomes/endpoints analyzed were technical and clinical success, early complications, stent patency period, and survival.ResultsThe technical and clinical success rates in both groups were 100%, and the early complication rates were not significantly different (P = 0.43). The median stent patency in the BDC group was significantly longer than that in the CDC group (7.8 ± 1.5 vs. 5.7 ± 0.7 months, P = 0.001), and the median overall survival period in the BDC group was prone to significant difference than that in the CDC group (9.4 ± 4.0 vs. 8.2 ± 0.3 months, P = 0.089).ConclusionThe findings of this study show that BDC with chemotherapy was associated with better stent patency and survival. However, since the sample size was very small, large randomized controlled multicenter studies are needed to further evaluate the long-term survival effects of BDC in patients with advanced pancreatic carcinoma combined with obstructive jaundice.

In Vivo Verification of Treatment Source Dwell Times in Brachytherapy of Postoperative Endometrial Carcinoma: A Feasibility Study.

(1) Background: In brachytherapy, there are still many manual procedures that can cause adverse events which can be detected with in vivo dosimetry systems. Plastic scintillator dosimeters (PSD) have interesting properties to achieve this objective such as real-time reading, linearity, repeatability, and small size to fit inside brachytherapy catheters. The purpose of this study was to evaluate the performance of a PSD in postoperative endometrial brachytherapy in terms of source dwell time accuracy. (2) Methods: Measurements were carried out in a PMMA phantom to characterise the PSD. Patient measurements in 121 dwell positions were analysed to obtain the differences between planned and measured dwell times. (3) Results: The repeatability test showed a relative standard deviation below 1% for the measured dwell times. The relative standard deviation of the PSD sensitivity with accumulated absorbed dose was lower than 1.2%. The equipment operated linearly in total counts with respect to absorbed dose and also in count rate versus absorbed dose rate. The mean (standard deviation) of the absolute differences between planned and measured dwell times in patient treatments was 0.0 (0.2) seconds. (4) Conclusions: The PSD system is useful as a quality assurance tool for brachytherapy treatments.

Intracavitary brachytherapy with additional Heyman capsules in the treatment of cervical cancer

PurposeBrachytherapy is a mandatory component of primary radiochemotherapy in cervical cancer. The dose can be applied with a traditional intracavitary approach (IC alone) or with multiple catheter brachytherapy to optimize dose distribution in an individual concept. We therefore evaluated whether the utilization of a tandem–ring applicator plus additional intracavitary applicators (add IC) provides an advantage over the traditional IC alone approach, as this method is less time consuming and less invasive compared to a combined intracavitary/interstitial brachytherapy.MethodsTwenty three procedures of intracavitary brachytherapy for cervical cancer with additional intracavitary applicators performed in seven patients treated between 2016 and 2018 in our institution were included in this study. Plans were optimized for D90 HR-CTV with and without the utilization of the additional applicators and compared by statistical analysis.ResultsD90 for HR-CTV was 5.71 Gy (±1.17 Gy) for fractions optimized with add IC approach and 5.29 Gy (±1.24 Gy) for fractions without additional applicators (p < 0.01). This translates to a calculated mean EQD2 HR-CTV D90 of 80.72 Gy (±8.34 Gy) compared to 77.84 Gy (±8.49 Gy) after external beam therapy and four fractions of brachytherapy for add IC and IC alone, respectively (p < 0.01). The predictive value of improved coverage of HR-CTV in the first fraction was high.ConclusionIn a subgroup of cases, the addition of intracavitary Heyman capsules can be an alternative to interstitial brachytherapy to improve the plan quality compared to standard IC alone brachytherapy. The benefit from the addition of applicators in the first fraction is predictive for the following fractions.

High-Dose Rate Interstitial Spine Brachytherapy Using an Intraoperative Mobile Computed Tomography-Guided Surgical Navigation System.

Up to 15% of previously irradiated metastatic spine tumors will progress. Re-irradiation of these tumors poses a significant risk of exceeding the radiation tolerance to the spinal cord. High-dose rate (HDR) brachytherapy is a treatment alternative. To develop a novel HDR spine brachytherapy technique using an intraoperative computed tomography-guided navigation (iCT navigation). Patients with progressive metastatic spine tumors were included in the study. HDR brachytherapy catheters were placed under iCT navigation. CT-based planning with magnetic resonance imaging fusion was performed to ensure conformal dose delivery to the target while sparing normal tissue, including the spinal cord. Patients received single fraction radiation treatment. Five patients with thoracolumbar tumors were treated with HDR brachytherapy. Four patients previously received radiotherapy to the same spinal level. Preimplant plans demonstrated median clinical target volume (CTV) D90 of 116.5% (110.8%-147.7%), V100 of 95.7% (95.5%-99.6%), and Dmax of 8.08 Gy (7.65-9.8 Gy) to the spinal cord/cauda equina. Postimplant plans provided median CTV D90 of 113.8% (93.6%-120.1%), V100 of 95.9% (87%-99%), and Dmax of 9.48 Gy (6.5-10.3 Gy) to cord/cauda equina. Patients who presented with back pain (n=3) noted symptomatic improvement at a median follow-up of 22 d after treatment. Four patients demonstrated local tumor control of spinal metastatic tumor at a median follow-up of 92 d after treatment. One patient demonstrated radiographic evidence of local tumor progression 2.7 mo after treatment. HDR spine brachytherapy with iCT navigation is a promising treatment alternative to induce local tumor control and reduce pain symptoms associated with metastatic spine disease.

A high-Z inorganic scintillator-based detector for time-resolved in vivo dosimetry during brachytherapy.

High-dose rate (HDR) and pulsed-dose rate (PDR) brachytherapy would benefit from an independent treatment verification system to monitor treatment delivery and to detect errors in real time. This paper characterizes and provides an uncertainty budget for a detector based on a fiber-coupled high-Z inorganic scintillator capable of performing time-resolved in vivo dosimetry during HDR and PDR brachytherapy. The detector was composed of a detector probe and an optical reader. The detector probe consisted of either a 0.5× 0.4 × 0.4 mm3 (HDR) or a 1.0 × 0.4 × 0.4 mm3 (PDR) cuboid ZnSe:O crystal glued onto an optical-fiber cable. The outer diameter of the detector probes was 1mm, and fit inside standard brachytherapy catheters. The signal from the detector probe was read out at 20Hz by a photodiode and a data acquisition device inside the optical reader. In order to construct an uncertainty budget for the detector, six characteristics were determined: (1) temperature dependence of the detector probe, (2) energy dependence as a function of the probe-to-source position in 2D (determined with 2 mm resolution using a robotic arm), (3) the signal-to-noise ratio (SNR), (4) short-term stability over 8h, and (5) long-term stability of three optical readers and four probes used for in vivo monitoring in HDR and PDR treatments over 21 months (196 treatments and 189 detector calibrations, and (6) dose-rate dependence. The total uncertainty of the detector at a 20 mm probe-to-source distance was<5.1% and<5.8% for the HDR and PDR versions, respectively. Regarding the above characteristics, (1) the sensitivity of the detector decreased by an average of 1.4%/°C for detector probe temperatures varying from 22 to 37°C; (2) the energy dependence of the detector was nonlinear and depended on both probe-to-source distance and the angle between the probe and the brachytherapy source; (3) the median SNRs were 187 and 34 at a 20 mm probe-to-source distance for the HDR and PDR versions, respectively (corresponding median source activities of 4.8 and 0.56Ci, respectively); (4) the detector response varied by 0.6% in 11 identical irradiations over 8h; (5) the sensitivity of the four detector probes decreased systematically by 0-1.2%/100Gy of dose delivered to the probes, and random fluctuations of 4.8% in the sensitivity were observed for the three probes used in PDR and 1.9% for the probe used in HDR; and (6) the detector response was linear with dose rate. ZnSe:O detectors can be used effectively for in vivo dosimetry and with high accuracy for HDR and PDR brachytherapy applications.

A multipurpose brachytherapy catheter to enable intratumoral injection

PurposeTo create and test a multipurpose brachytherapy catheter prototype enabling intratumoral injection and brachytherapy after a single catheter insertion. Methods and MaterialsThe design of the prototype consists of an outer tube and an inner syringe tube that can be filled with injectable agent. The outer sheath and inner syringe tube were constructed using polytetrafluoroethylene tubing, and the other components were 3D printed using dental resin and polylactic acid material. To demonstrate functionality, we injected in vitro phantoms with dyed saline. For proof of concept, we demonstrated the potential for the prototype to deliver cell therapy, enhance tumor delineation, deliver tattoo ink for pathology marking, avoid toxicity through local delivery of chemotherapy, and facilitate combination brachytherapy and immunotherapy. ResultsThe prototype enables accurate injection in vitro and in vivo without altering dosimetry. To illustrate the potential for delivery of cell therapies, we injected luciferase-expressing splenocytes and confirmed their delivery with bioluminescence imaging. To demonstrate feasibility of radiographically visualizing injected material, we delivered iohexol contrast intratumorally and confirmed tumor retention using Faxitron x-ray imaging. In addition, we show the potential of intratumoral administration to reduce toxicity associated with cyclophosphamide compared with systemic administration. To demonstrate feasibility, we treated tumor-bearing mice with brachytherapy (192Ir source, 2 Gy to 5 mm) in combination with intratumoral injection of 375,000 U of interleukin 2 and observed no increased toxicity. ConclusionsThese results demonstrate that a prototype multipurpose brachytherapy catheter enables accurate intratumoral injection and support the feasibility of combining intratumoral injection with brachytherapy.

Dosimetric characteristics of accelerated partial breast irradiation by interstitial multicatheter brachytherapy with intraoperative free-hand implantation in the treatment of early breast cancer.

IntroductionThe aim of this study is to evaluate the characteristics of the dosimetry and the skin dose of interstitial brachytherapy by the use of the free‐hand implantation technique toward the treatment of early breast cancer.Materials & MethodsSeventeen patients diagnosed with early breast cancer were selected for the study. The implantation of the catheters for postoperative interstitial brachytherapy was performed using the free‐hand technique. The total tumor dose to the tumor cavity plus 2 cm margin was 3400 cGy, twice daily for 10 fractions in 5 days. The dosage to the target and the organ at risk (OAR) were recorded for analysis. The skin dose of the patient and the phantom were measured with Gafchromic film (EBT3) and the results were compared with the skin dose calculated by the brachytherapy treatment planning system.ResultsThe median conformal index is 94% (range 89%–99%), and the median homogeneity index is 71%. The median skin dose measured from the skin of the patients was 20.1% lower than the skin dose calculated from the treatment planning system and consistent with the phantom surface measurement experiment. There were no grade 3 or above acute toxicity recorded.ConclusionsInterstitial brachytherapy by the use of the free‐hand implantation technique for early breast cancer is feasible and avoids the need for a second surgical intervention. The calculated skin dose was overestimated by at least 20%. The results of this study may help in building a modification model for the prediction of skin toxicity in any future study.

Endobronchial HDR Brachytherapy for Post-Transplant or Wegener’s Granulomatosis Associated Bronchial Stenosis

Bronchial stenosis is a clinically challenging problem following lung transplant and in Wegener’s Granulomatosis. Despite laser, stenting, balloon dilation among other interventions, worsening of stenosis often occurs. Endobronchial brachytherapy has been implemented for treatment refractory stenotic areas based on limited data. We hypothesize that high dose rate (HDR) Brachytherapy using 3Gy x1 fraction is effective in alleviating treatment refractory stenosis of bronchus. Patients who underwent endobronchial HDR Ir-192 brachytherapy from January 2016 to January 2020 for bronchial stenosis were retrospectively reviewed. Patients were selected for HDR brachytherapy if they had treatment refractory symptomatic re-stenosis. On day of brachytherapy, a flexible bronchoscopy was performed and a brachytherapy catheter was inserted. Intraoperative fluoroscopic imaging confirmed catheter positioning. Treatment length ranged from 3-5cm. The dose of 3Gy in 1 fraction was prescribed 1cm from the catheter surface. Patients were followed with bronchoscopies and pulmonary function testing (PFTs). Four patients were included with median follow-up of 5.2m (range: 0.9-16.8). One patient received brachytherapy 12Gy in 4 fractions 12 years prior to re-treatment. The same patient received a second double lung transplant due to bronchiolitis obliterans. All patients had initial clinical & bronchoscopic improvement with brachytherapy. The one Wegener’s Granulomatosis patient required an additional two courses of brachytherapy due to residual granulation tissue found proximally outside of the prior radiation treatment fields. Median time to next endobronchial intervention after brachytherapy was 5.2m [0.9-18.8]. The median number of interventions pre and post brachytherapy are listed below (Table 1). FEV1 prior to brachytherapy was 33% predicted [27-65] and PFT after brachytherapy was 40% predicted [25-72]. The one Wegener granulomatosis patient had a balloon dilation procedure induced grade 4 bronchopulmonary hemorrhage three months after 3rd brachytherapy treatment, requiring bronchial artery embolization. They were subsequently discharged 36 hours after the initial bleed and remains free of stenosis. Table 1 Endobronchial HDR brachytherapy utilizing 3Gy x 1 fraction was safe and effective in resolving refractory re-stenotic areas of bronchus caused by granulation tissue. There were no toxicities associated with lung transplant patients. The Wegener’s Granulomatosis patient had a potential G4 toxicity after a third brachytherapy treatment. Caution needs to be applied in the setting of repeated endobronchial brachytherapy procedures. More robust follow up is needed to assess long term success.Abstract 2512; TablePatientNumber of Pre-Brachytherapy InterventionNumber of Post-Brachytherapy Intervention12-6 months6-0 months0-6 months6-12 months194191221311303442042900Median [range]6.5 [2-13]6.5 [4-11]2.5 [0-19]0 [0-12] Open table in a new tab

Use of an ultrasound imaging device within the applicator to evaluate placement and support treatment planning for breast brachytherapy and intraoperative radiation therapy

PurposeWe evaluated the use of ultrasound imaging within a brachytherapy applicator as a method for applicator positioning, evaluation, and treatment planning in a series of in vitro, cadaver, and human studies. Methods and MaterialsWe evaluated the performance of a prototype system comprising a small ultrasound imaging catheter inserted within the lumen of a balloon brachytherapy catheter. We tested the device in an ultrasound phantom, in human breast tissue, and in an endoscopic ultrasound catheter in cadaveric breast tissue. We evaluated the visualization of adjacent tissue to consider future development of a similar system for use in brachytherapy and intraoperative radiation therapy. ResultsBased on the ultrasound images obtained in an ultrasound phantom, cadaveric breast, and human participants, we observed that an ultrasound imaging catheter placed within the lumen of a brachytherapy applicator can effectively image adjacent tissue, ribs, and air voids, with appropriate quality to support clinical use. We observed high correlation in clinically useful information detected on ultrasound and comparative CT, with ultrasound spatial resolution near 1 mm (spatially variant). ConclusionsThe findings from our pilot work suggest that real-time ultrasound imaging, operated from within the applicator, is a promising technique for image guidance and treatment planning during brachytherapy and intraoperative radiation therapy. Further expansion of this technology for clinical use will require development of a cohesive system of components to suit specific clinical applications.