Brachytherapy System Research Articles

PO0428: Development of an MRI-Guided Needle Placement System for Prostate Brachytherapy: Proof of Principle

PO0428: Development of an MRI-Guided Needle Placement System for Prostate Brachytherapy: Proof of Principle

Comparative long-term oncological outcomes of intraoperative radiotherapy vs. whole-breast irradiation in early breast cancer: a single institute study.

Intraoperative radiation therapy (IORT) and whole breast irradiation (WBI) are both effective adjuvant radiotherapy methods for ductal carcinoma in situ (DCIS) or early-stage breast cancer (BC) patients undergoing breast-conserving surgery (BCS). We aim to evaluate the long-term oncological efficacy and refine patient selection criteria based on our findings. Female patients who underwent either IORT or WBI from January 2016 to December 2019, with a minimum follow-up of 12 months were collected. IORT was administered as a single fraction of 20 Gray (Gy) to the lumpectomy cavity using the Axxent electronic brachytherapy system, while WBI consisted of a standard fractionation of 50 Gy in 25 fractions, along with a reduced boost of 10 Gy. The clinicopathologic characteristics and oncological outcomes were retrospectively analyzed. A total of 247 patients were enrolled, comprising 164 with BC and 83 with DCIS. Among them, 112 underwent IORT, and 135 received WBI after BCS. The median age was 62.2 years, with median tumor sizes of 1.5cm for BC and 1.2cm for DCIS. At a median follow-up of 64.6 months, IORT demonstrated 11 locoregional recurrences (LRR), 1 metastasis, and 1 death, compared to 4 LRR, 5 metastases, and 2 deaths in the WBI group. WBI yielded significantly higher locoregional control (97.0% vs. 90.2%, p = 0.033), although metastasis-free (96.3% vs. 99.1%, p = 0.166) and overall survival rates (98.4% vs. 99%, p = 0.688) did not differ. The LRR rate was significantly higher in the IORT group among the DCIS or BC patients (p = 0.043). The hazard ratio for locoregional recurrence significantly increased in estrogen-receptor-negative (ER-) patients in both univariate analysis (HR = 4.98, 95% CI = 1.76-14.09, p = 0.002) and multivariate analysis (HR = 40.88, 95% CI = 1.29-1297.84, p = 0.035). Additionally, IORT was associated with increased LRR in the multivariate analysis (HR = 4.71, 95% CI = 1.16-19.06, p = 0.030). At a long-term follow-up, the LRR rate was higher in the BCS followed by IORT, without significant differences in metastasis-free or overall survival rates. Our data confirmed the importance of exclusion ER- patients for IORT.

Technical note: Determination of for a miniature x-ray source using a soft x-ray ionization chamber calibrated in NIST reference beam qualities.

The formalism proposed by Watson etal. allows users of the INTRABEAM (Carl Zeiss Medical AG, Jena, Germany) electronic brachytherapy system to accurately determine the absorbed dose to water, in the absence of a primary dosimetry standard. However, all published values are for PTW 34013 ionization chambers calibrated in a TW30 reference beam, traceable to PTB (Germany). For North American users, it would be advantageous to have data for chambers calibrated in a kV reference beam maintained by the National Institute of Standards and Technology (NIST). In this work, we determine for a PTW 34013 chamber calibrated in three NIST-traceable reference beams: M30, L40, andL50. Using available photon spectra data for M30, L40, and L50 reference beam qualities, Monte Carlo simulations using EGSnrc were performed to calculate the ratio of the absorbed dose to the PTW 34013 chamber air cavity to air-kerma ( ) for these beams. From this ratio, as a function of depth in water was determined. The effect of the use of a buildup foil was also investigated. An uncertainty analysis considering both the Type A and Type B uncertainties in the calculation of was performed. The largest difference in was found between L50 and TW30, with a relative decrease of 1.4% (no buildup) to 1.6% (buildup). For M30 and L40, the differences were minimal compared with measurementuncertainties. We report values for three NIST-traceable kV reference beams. This study reinforces the feasibility of adapting the Watson etal. methodology using different kV reference beams, facilitating the use of INTRABEAM in North America and ensuring the continuity and accuracy of dosimetry standards in intraoperative radiationtherapy.

Impact of dose distribution by a 3D planning system for brachytherapy with 198Au grains for head and neck cancer.

There has been no study in which the correlation between clinical results and dosimetry based on a 3D treatment planning system in patients with 198Au grains for head and neck cancer was evaluated. Thirty-two patients who were treated with 198Au grains for head and neck cancer were reviewed. Twenty-five patients were treated with brachytherapy alone and seven patients were treated with a combination of brachytherapy and neoadjuvant external beam radiation therapy. With a median observation period of 60 months, the 5-year local control rate was 82.9%. V85Gy of CTV in patients with local recurrence tended to be lower than that in patients without local recurrence (p = 0.07). The maximum dose of the keratinized gingiva in patients in whom bone exposure occurred was significantly higher than that in patients in whom bone exposure did not occur (p = 0.001). Dose distribution with 198Au grains can predict local control and late adverse events.

502: Virtual-reality assisted training system for interstitial brachytherapy in cervical cancer

502: Virtual-reality assisted training system for interstitial brachytherapy in cervical cancer

US-guided EM tracked system for HDR brachytherapy: A first in-men randomized study for whole prostate treatment

PURPOSEAn electromagnetic tracking device (EMT) has been integrated in an HDR 3D ultrasound guidance system for prostate HDR. The aim of this study was to compare the efficiency of HDR workflows with and without EM tracking. METHODS AND MATERIALSA total of 58 patients with a 15 Gy HDR prostate boost were randomized in two arms and two operation room (OR) procedures using: (1) the EMT investigational device, and (2) the Oncentra prostate system (OCP). OR times were compared for both techniques. RESULTSThe overall procedure median time was about 20% shorter for EMT (63 min) compared to OCP (79 min). The US acquisition and contouring was longer for OCP compared to EMT (23 min vs. 16 min). The catheter reconstruction's median times were 23 min and 13 min for OCP and EMT respectively. For the automatic reconstruction with EMT, 62% of cases required no or few manual corrections. Using the EM technology in an OR environment was challenging. In some cases, interferences or the stiffness of the stylet introduced errors in the reconstruction of catheters. The last step was the dosimetry with median times of 11 min (OCP) and 15.5 min (EMT). Finally, it was observed that there was no learning curve associated with the introduction of this new technology. CONCLUSIONSThe EMT device offers an efficient solution for automatic catheter reconstruction for HDR prostate while reducing the possibility of mis-reconstructed catheters caused by issues of visualization in the US images. Because of that, the overall OR times was shorter when using the EMT system.

Development of Novel Focal Irradiation Tool for High-Precision Irradiation Using Clinical Brachytherapy System

Several small animals, including mice, are used to conduct research on state-of-the-art radiation therapy techniques or treatment-related toxicity. However, it is difficult to conduct the focal irradiation to a shallow depth on small animals, because irradiation using LINAC has limitations in energy and field size. The purpose of this paper was to develop a focal irradiation tool for high-precision irradiation and to evaluate beam characteristics. We designed the collimator of 1 mm diameter consisting of tungsten material for high-precision irradiation applied to the clinical brachytherapy system and the percent depth dose and horizontal profile were measured. We compared the depth dose and horizontal profile with 4 mm diameter SRS cone for 6 MV in LINAC. We measured the PDD and horizontal profile using EBT3 film for high-precision irradiation of 1 mm diameter using Ir-192 source. In case of 4 mm diameter, the beam was measured using edge detector. In addition, all measurements were compared with the results of planning tool simulation. In case of focal irradiation tool, the maximum dose showed at the surface for both measurement and simulation, and 26% and 32% doses at 1 mm depth, respectively. In addition, FWHM at a 1 mm depth showed that high-precision irradiation was possible with measurement and simulation results of 1.86 and 1.28 mm. In case of LINAC, the maximum dose was showed at a depth of 1 cm and 0.8 cm in the measurement and simulation, respectively. Even if the smallest cone is used, the FWHM at a dmax depth was 4.0 mm in both simulation and measurement. We overcame the limitation for energy and field size through the focal irradiation tool for high-precision irradiation. The focal irradiation tool enables high dose delivery to the shallow depth. In addition, small FWHM reduced dose delivery to the periphery at a specific depth and enabled accurate dose delivery. These results mean that the focal irradiation tool can be useful in small animal experiments that require accurate doses near the shallow depth.

Dose distributions of the INTRABEAM electronic brachytherapy system measured with traceable detectors

In this work, a methodology to determine the absorbed dose rate to water distribution from electronic brachytherapy (eBT) units is suggested. It involves measuring directly in a full scatter water tank with small active detectors whose energy response at low X-ray photon energies have been previously characterized. Dose distributions of an INTRABEAM PRS 500 system in two configurations — bare needle and with the spherical applicator of 40 mm diameter — were measured in water using the Exradin A26 ionization chamber and the PTW 60019 microDiamond detector. The continuous energy response of these two detectors in terms of air kerma from 5 keV to 70 keV (eBT energy range) was available from a previous calibration at several X-ray radiation qualities. Here, it is converted to the response in absorbed dose to water using correction factors obtained with Monte Carlo (MC) particle transport simulations. The detectors were modelled using the MCNP code. The air kerma calibration factors were simulated and compared with measurements to refine and validate the models. A series of simulations of the experimental arrangement of the INTRABEAM and the detector were carried out for determining the system specific detector correction factors. These values are distance-dependent due to the steep dose gradient and the remarkable spectral changes around the eBT source in water. The dose rate with distance from the source, the radial and the polar distributions of the INTRABEAM are reported and compared with the manufacturers supplied data. This work is an effort to provide traceability for detectors and measurement procedures for the determination of 3D dose distributions as part of the European joint research project “Primary standards and traceable measurement methods for X-ray emitting electronic brachytherapy devices” (18NRM02 PRISM-eBT).

Preliminary study of integrated C-arm CT/SPECT imaging system for online adaptive 3D brachytherapy using Monte Carlo simulation

Recent advancements in high-dose-rate brachytherapy have led to remarkable clinical outcomes. However, these new developments can cause unknown uncertainties with respect to actual dose delivery, which are yet to be clarified. Therefore, an accurate dose verification system is required. Currently, procedures for image-guided adaptive brachytherapy are constrained by the following limitations: (1) patient transportation between the treatment room and CT/MR (computerized tomography/magnetic resonance) imaging room can displace the application position, (2) the physiological and anatomical changes in the patient’s body cannot be observed during the treatment schedule involving 3–10 fraction, and (3) the movement of the radioactive source inside the body is impossible to track. This study proposes a concept of an integrated online imaging system, which is based on integrated CT and single-photon emission computed tomography (SPECT), namely, the C-arm CT/SPECT system—a combination of a C-arm fluoroscopic x-ray imaging system and an attachable parallel-hole collimator over the imaging detector. The Geant4 software is used to simulate the application of the C-arm CT/SPECT system for 192Ir-based brachytherapy in a pelvis-like phantom. To improve the image quality of C-arm CT/SPECT acquired with limited-angle information, we utilized an adaptive-steepest-descent-projection-onto-convex-sets framework that incorporates additional prior information for the proposed system. Furthermore, we confirmed that SPECT images can be obtained using a parallel-hole collimator and estimated the dose distribution in the medium and CT/SPECT fusion imaging during treatment. This strategy is expected to be effectively implemented in online image-guided adaptive brachytherapy and patient-dose verification.

Comparison of single catheter versus dual catheter-based EBT3 film calibration for the Ir-192 beam energy

Purpose. Films and TLDs have been the common choices for passive in-vivo dose measurement in radiotherapy. In the brachytherapy applications, it is very difficult to report and verify the dose at multiple localized high dose gradient regions and also the dose to organ at risk. This study was carried out to introduce a new and accurate calibration method for GafChromic EBT3 films irradiated using Ir-192 photon energy from miniature High Dose Rate (HDR) Brachytherapy source. Materials and methods. Film holder made of Styrofoam was used to hold the EBT3 film at its center. It was placed inside the mini water phantom and the films were irradiated by Ir-192 source of microSelectron HDR afterloading brachytherapy system. Two different setups: Single catheter-based film exposure and dual catheter-based film exposure were compared. The films scanned on a flatbed scanner were analysed in three different color channels: red, green, and blue using Image J software. The dose calibration graphs were generated using the third-order polynomial equations fitted on the data points from two different methods of calibration procedure. Maximum and mean dose difference between TPS calculated and measured was analyzed. Results. The measured dose difference from the TPS calculated doses were evaluated for the three groups of dose ranges (low, medium and high). In the high dose range, standard uncertainty of dose difference are ±2.3%, ±2.9%, and ±2.4% respectively for the red, green, and blue color channel when the TPS calculated dose was compared with single catheter based film calibration equation. Whereas it is observed as 1.3%, 1.4% and 3.1% for the red, green, and blue color channels respectively when compared with the dual catheter based film calibration equation. A test film was exposed to a TPS calculated dose of 666 cGy to validate the calibration equations, single catheter based film calibration equation estimated the dose difference as −9.2%, −7.8% and −3.6% respectively in the red, green, and blue color channels whereas the same were observed as 0.1%, 0.2% and 6.1% respectively when dual catheter based film calibration equation was applied. Conclusion. Source miniature size, reproducible positioning of the film and catheter system inside water medium are the major challenges in the film calibration with Ir-192 beam. To overcome these situations dual catheter-based film calibration was found more accurate and reproducible as compare to the single catheter based film calibration.

Determining The Accuracy of Dwell Position by Using Electron Energy with Gafchromic Film in High Dose Rate Brachytherapy Systems

Due to the general lack of darkroom and film processing equipment in many clinics, it is no longer possible to use radiation sensitive Xomat V radiographic film for High Dose Rate brachytherapy quality assurance. An alternative is to use radio chromic film that does not require processing. The aim of this study is to develop and clinically test the GafChromic film-based brachytherapy Quality Assurance (QA) system using different electron energies. As an electron source (6 MeV-9 MeV-12 MeV -15 MeV -18 MeV) (Elekta Synergy® Platform linear accelerator, Varian GM plus IX (Varian Medical Systems, Inc.USA), Varian brand cylinder, ring and tandem double ovoid applicators, RTQA2 and EBT3 GafChromic film were used. In RTQA2 films, images are obtained at high electron energies (12 MeV and above) at 300 Monitor Unit (MU), while images are obtained at all energies at 700 MU in irradiation using different electron energies and MUs. For the desired image quality depending on the material of the applicator used, it was determined that the image clarity increased as the energy, field size and MUs increased. In EBT3, the desired image could be obtained at 18 MeV and 2500 MU. It is possible to obtain the desired image quality by using high-energy electrons, especially RTQA2 Gafchromic film, in determining the accuracy of the dwell position in brachytherapy. Since it has been determined that this method can be used easily in quality control tests, we think that this method is suitable for clinical use when necessary.

Design and Experimental Setup of a Robotic Medical Instrument for Brachytherapy in Non-Resectable Liver Tumors

This paper presents a study regarding the design and the experimental setup of a medical robotic system for brachytherapy using tribology analysis. The robotic system is composed of a collaborative robotic arm and a multi-needle brachytherapy instrument controlled using a unified control system embedding a haptic device and force-feedback. This work is oriented towards identifying the technical characteristics of the system components to determine the accuracy of the procedure, as well as using different scenarios for needle insertion in ex vivo porcine liver tissue in order to determine the forces required for insertion and extraction of the needle and the friction coefficient that accompanies the previously mentioned forces. Subsequent to the computation of the friction forces, the normal forces and the wear during the needle insertion are determined with the scope of predicting the lifecycle of some components of the medical device.

CTNI-51. FEASIBILITY AND SAFETY OF NEUROSURGICAL RESECTION AND INTRA-OPERATIVE RADIATION THERAPY USING THE XOFT AXXENT ELECTRONIC BRACHYTHERAPY SYSTEM AND BEVACIZUMAB IN RECURRENT GLIOBLASTOMA

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain tumor. External beam radiation therapy (EBRT) is widely recognized as an effective treatment for primary GBM. EBRT applied after GBM resection is associated with an increase in overall survival. Beyond upfront therapy with radiation and temozolomide chemotherapy, there is no standard therapy that has been proven effective. Re-irradiation with ERBT is minimally effective and with significant comorbidities. Our study uses IORT at the time of re-resection in patients who have recurrent, operable GBM after failure of who received primary EBRT and temozolamide in their first course of treatment. IORT allows the delivery of a large effective radiation dose applied directly to the tumor bed at the time of resection. This affords direct radiation to be delivered to the micro- and macroscopic tumor remnants in the vicinity of the resection cavity immediately following gross resection. In contrast, the more distant, surrounding brain tissue does not receive high radiation exposure. This Phase II study continues to accrue subjects with the primary endpoint of overall survival and several secondary endpoints that includes progression free survival, quality of life, and adverse events/safety. To date, five patients have been treated on this protocol. The technical feasibility and safety of administering intraoperative radiation with the Xoft System has been established in this cohort. Preliminary GLIOX Trial findings demonstrate the safety and feasibility of using the Xoft Axxent® Electronic Brachytherapy System to administer intracranial radiation during resection of recurrent glioblastomas. We will report new and expansive study results to include these early findings.

PO16: Commissioning of the Varian Universal Interstitial Cylinder (UIC) System for HDR Brachytherapy of Cervical Cancer

<h3>Purpose</h3> Varian Medical Systems (VMS) has recently released the Universal Interstitial Cylinder (UIC) for use with Ir-192 HDR brachytherapy. We commissioned one cylinder with a plastic Universal Cervix Probe (UPC) and plastic interstitial needles using CT and MR images. A phantom specifically designed to avoid the introduction of water or water-like materials into the needle guide tracks was used and various marker strands were investigated to accurately reconstruct source positions. <h3>Materials and Methods</h3> CT and MR scan were taken for the UIC set: one cylinder (30 mm diameter) with plastic UCP (80 mm, 30 degrees) and eight interstitial needles (channel #2-#9). To compare three different methods for channel identification, CT images (Siemens Biograph mCT, Siemens AG) with slice thickness of 0.6 mm were taken with either no radio opaque markers, VMS-numbered markers, or nylon coated stainless steel leader wires ("fish wire") which aid in channel identification and image registration. The MR images were taken on a 3T Magnetom Skyra Siemens MRI scanner using 3D T1 and 2D T2 weighted clinical HDR gynecological MRI protocols. An HDR MRI Lumen Marker (C4 Imaging, LLC) was placed in the channel #9 to check for any applicator rotation. The needle guide track openings at the distal end of the UIC cylinder causes liquid to be introduced into the tracks which results in unintended MR and CT signal. A gynecological phantom was constructed by placing the applicator set into three different phantom materials: wet towels, gelatin, or ground beef. Image quality of the CT and MRI scans for these phantoms were compared for treatment planning. The applicator dimensions were verified on CT and kV planar images. Dimensions from the vendor solid applicator models, which are based on the computer-aided design model files of the specific applicator were compared to those on CT and kV images. <h3>Results</h3> The phantoms made of wet towels or gelatin allowed significant amounts of liquid to enter the needle guide tracks from the holes in the distal end of the cylinder. This can mislead as to the actual source positions in the applicator. Specifically, it resulted in channels with unintended MR and CT signal (Figure 1a). The ground beef phantom was developed to limit this introduction of liquid into the cylinder (Figure 1b). CT scans with no markers displayed substantially wider needle guide tracks than the plastic needles (Figure 1b). CT scans with VMS-markers showed significant artifact (Figure 1c). CT scans with fish wire provided the best visibility of the needles within the needle guide tracks (Figure 1d). This scan along with the solid applicator model was also used to confirm distance from the outer wall to the inside of the needle guide track (8 mm) and to the center of the needle (7 mm) and the 30 mm diameter of the cylinder (Figure 1d). The use of an MR marker allowed that needle (channel #9) to be identified in the T1w MR scan (Figure 1b). The dimensions of the applicators could be validated on CT (Figure 1d) and kV planar images (Figure 1e). <h3>Conclusions</h3> The UIC applicator was commissioned for CT and MR image based treatment planning for HDR brachytherapy. Planar kV images verified dimensions of applicator against vendor specs. Accurate source position reconstruction was feasible using CT scan with 0.6 mm slice thickness and radio-opaque markers. The use of a ground beef phantom rather than a liquid based phantom minimized unintended MR and CT signal by limiting introduction of fluid into the needle guide tracks.

Do HDR Tandem and Ring Interfractional Displacements Predict the Need to Re-Plan?

<h3>Purpose/Objective(s)</h3> To evaluate the effect of changes in HDR tandem and ring applicator position on doses to nearby organs at risk. <h3>Materials/Methods</h3> CT imaging studies (29) and dosimetry of 6 women ages 44 to 86 undergoing tandem/ring based HDR for cervical cancer were used retrospectively. Measures of applicator positional changes (translation and rotation) relative to the pelvis were obtained using image fusion in a commercial image analysis software. Dosimetric data were calculated in the commercial image analysis software using the original (first fraction) dose distribution applied to organs at risk (rectum and bladder) via deformable registration of the original contours. The new contours were examined visually for appropriateness. Differences in translation and rotation between the planning CT and subsequent individual fractions were recorded and plotted against dose changes between each fraction of treatment and the original (first) fraction. Percent differences in positional shifts vs dosimetric changes were calculated and a correlation coefficient between dose parameters and measured positional shifts of the applicator was determined. <h3>Results</h3> Dosimetric parameters for rectum and bladder (D_2cc and V₅₀) calculated using a commercial treatment planning system for HDR brachytherapy and commercial image analysis software gave similar results within 1% of the original plan (Fraction 1 of 5). A summary of positional changes and average and maximum dose changes for each dosimetric endpoint is found in Table 1. Average percent difference between planned dose and fractional doses obtained through deformable registration were 12%, 16%, 4% and 49% for bladder D_2cc, Bladder V₅₀, Rectum D_2cc and Rectum D₅₀, respectively. Correlation between dose parameters and measured positional changes for bladder D₅₀ and displacement and bladder D₅₀ and sagittal plane rotation gave an r² of 0.3. Applicator displacement of approximately 1.6 times greater than average applicator displacement across all plans studied have shown a significant increase in bladder dose. Bladder dose increased by a maximum of 30 Gy and 54.5 Gy for bladder D_2cc and bladder V₅₀, respectively for the patient with the largest catheter shifts. <h3>Conclusion</h3> We have quantified the effects of applicator positional changes on dose differences for bladder and rectum. Even large changes did not result in significant changes in dose to organs at risk, meaning adaptive re-planning is not required in most cases below a certain displacement threshold.

Quality assurance and long-term stability of a novel 3-in-1 X-ray system for brachytherapy.

PurposeA novel, mobile 3‐in‐1 X‐ray system featuring radiography, fluoroscopy, and cone‐beam computed tomography (CBCT) has been launched for brachytherapy recently. Currently, there is no quality assurance (QA) procedure explicitly applicable to this system equipped with innovative technologies such as dynamic jaws and motorized lasers. We developed a dedicated QA procedure and, based on its performance for a duration of 6 months, provide an assessment of the device's stability over time.MethodsWith the developed QA procedure, we assessed the system's planar and CBCT‐imaging performance by investigating geometric accuracy, CT‐number stability, contrast‐noise‐ratio, uniformity, spatial resolution, low‐contrast detectability, dynamic range, and X‐ray exposure using dedicated phantoms. Furthermore, we evaluated geometric stability by using the flexmap‐approach and investigated the device's laser‐ and jaw‐positioning accuracy with an in‐house test phantom. CBCT‐ and planar‐imaging protocols for pelvis, breast, and abdomen imaging were examined.ResultsPlanar‐ and CBCT‐imaging performances were widely stable with a geometric accuracy ≤1 mm, CT‐number stability of up to 46 HU, and uniformity variations of up to 48 HU over time. For planar imaging, low‐contrast detectability and dynamic range exceeded current recommendations. Although geometric stability was considered tolerable, partly substantial positioning inaccuracies of up to more than 120 mm and −13 mm were obtained for lasers and jaws, respectively. X‐ray exposure showed small variations of ≤0.56 μGy and ≤0.76 mGy for planar‐ and CBCT‐imaging, respectively. The conductance of the QA procedure allowed a smooth evaluation of the system's overall performance.ConclusionWe developed a QA workflow for a novel 3‐in‐1 X‐ray system allowing to assess the device's imaging and hardware performance. The system showed in general a reasonable imaging performance and stability over time, whereas improvements regarding laser and jaw accuracy are strictly required.

Fiber-Optic Based Laser Wakefield Accelerated Electron Beams and Potential Applications in Radiotherapy Cancer Treatments

Ultra-compact electron beam technology based on laser wakefield acceleration (LWFA) could have a significant impact on radiotherapy treatments. Recent developments in LWFA high-density regime (HD-LWFA) and low-intensity fiber optically transmitted laser beams could allow for cancer treatments with electron beams from a miniature electronic source. Moreover, an electron beam emitted from a tip of a fiber optic channel could lead to new endoscopy-based radiotherapy, which is not currently available. Low-energy (10 keV–1 MeV) LWFA electron beams can be produced by irradiating high-density nano-materials with a low-intensity laser in the range of ~1014 W/cm2. This energy range could be useful in radiotherapy and, specifically, brachytherapy for treating superficial, interstitial, intravascular, and intracavitary tumors. Furthermore, it could unveil the next generation of high-dose-rate brachytherapy systems that are not dependent on radioactive sources, do not require specially designed radiation-shielded rooms for treatment, could be portable, could provide a selection of treatment energies, and would significantly reduce operating costs to a radiation oncology clinic.

PO-1792 Implementation of IGABT evidence-based planning aims, whilst changing brachytherapy systems

PO-1792 Implementation of IGABT evidence-based planning aims, whilst changing brachytherapy systems

Technological advancements in brachytherapy of cancer

Emerging technological advancements in brachytherapy, when used alone or combined with conventional therapies have improved the therapeutic efficacy, leading to enhanced patient survival. Advancements in the use of various isotopes, delivery methods, incorporation of 3D imaging, and 3D printing, have significantly optimized the treatment planning and increased dose delivery accuracy, achieving high target volume irradiation and low normal tissue exposure. Real-time guidance during the implanting of radiation source into the tumor tissue has shown the promising outcome of brachytherapy. Integration of precise in vivo dosimetry methods have reduced the deviations in the measured dose, and associated operational errors, ensuring brachytherapy is accurate, and delivering more targeted doses over the course of the treatment. The use of new forms of radiation sources such as needles, pellets, tubes, overcomes the risk of source clumping and migration. Personalized applicators, biodegradable brachytherapy systems, injectable radiolabeled thermoresponsive polymers offer yet another promising brachytherapy approaches. Here we describe the recent technological innovations in brachytherapy and discuss various strategies adopted to overcome the associated challenges in preclinical and clinical settings.

Conundrums of coronary brachytherapy

PurposeIn the 1998–2005 heyday of intravascular coronary brachytherapy, a variety of delivery devices were developed and marketed. As the industry shrank, only one device, the Novoste Beta-Cath 3.5F System (Best Vascular, Norcross, GA) remained in commercial production. The 2008 instruction manual, the only official source of technical guidance, lacks recommendations for various common scenarios. Methods and MaterialsThe clinical conundrums described here were encountered during regular use of the Novoste system in 81 patients treated from January to December of 2020 in the course of using the Novoste device in accordance with the 2008 manufacturer's instruction manual. Our experience and strategies are reported and critiqued. ResultsAmbiguous patient selection factors include vein grafts, multiple affected vessels, large vessels, retreatment, multiple overlapping stents and prior radiation. Procedural ambiguities include vessel size determination, proper prescription dose, very long lesions and eccentric source positioning. Potential procedural mishaps include stuck sources and the risk of contamination. ConclusionsThe Novoste intravascular coronary brachytherapy system is the only commercially available brachytherapy delivery catheter, and may remain so for some time. The issues detailed here provide insight and guidance for current users and may prompt research into areas lacking adequate information.