BACKGROUND: Accelerated partial breast irradiation with high dose rate brachytherapy treats early-stage carcinoma. Strut-adjusted volume implant applicators are inserted into the cavity post-lumpectomy. For an unstable applicator, changes in distance are seen each day between struts. If an applicator is asymmetrical with no strut movement on subsequent days, then it is stable. If an asymmetrical applicator continues to change strut distances, it is unstable. Waiting for applicator stabilization improves treatment reproducibility but increases infection risk. There is currently no consensus on stability, with ranges from 24 hours (h) to 72 h. Therefore, this study aims to determine when stability is achieved.
METHODS: We retrospectively reviewed 242 female breast cancer patients (2014-2022). CT was performed the same day as applicator insertion (Day 0) and repeated each treatment day. If applicators were initially asymmetrical, the distance between adjacent struts was measured, and the percentage change between the next and previous treatment day was calculated to determine how many applicators stabilized. Less than 5% change indicated stability.
RESULTS: On Day 0, 208 out of 242 patients (86%) had stable and symmetrical applicators that maintained stability each treatment day, and 34 out of 242 patients (14%) had applicators with asymmetrical struts. Within 24 h post-insertion, 229 out of 242 (95%) patients had stabilized applicators that maintained stability on subsequent treatment days.
CONCLUSIONS: Narrows previously suggested stability (24-72 h) to 24 h, leading to improved treatment efficiency and decreased infection risk as less time is needed to achieve applicator stability.

UNASSIGNED: High dose rate (HDR) image-guided brachytherapy with Cobalt-60 isotope is a relatively recent approach. The aim of the study is to evaluate the clinical and dosimetric parameters in terms of tumour response, bladder, and rectal toxicity in patients undergoing Co-60 HDR brachytherapy.
UNASSIGNED: All patients were initially treated with chemoradiation (CT-RT) at our center or other referral centers with external beam radiation therapy (EBRT) for a dose of 45 Gy-60 Gy at 1.8-2Gy/fraction (including nodal boost) with concomitant chemotherapy with either cisplatin or carboplatin. Patients were then scheduled for brachytherapy within 1 week after completion of CT-RT and are assessed by local examination. Depending on local examination parameters at the time of brachytherapy they were eligible either for intracavitary brachytherapy (ICBT) or interstitial brachytherapy (ISBT).
UNASSIGNED: The complete response (CR) observed in stage I, II, III, IVA were 60%, 79.4%, 86% and 76.2% respectively. Complete response was seen in patients with mean EQD2 of 78.67 Gy10, 83.33 Gy10, 84.23 Gy10, 85.63 Gy10 in stages I, II, III, IVA respectively. 79.2% of cisplatin-treated patients and 87.5% of carboplatin-treated patients had a complete response indicating that patients treated with either chemotherapy had similar response rates.
UNASSIGNED: According to results obtained from the study we conclude by saying that higher rates of complete response to treatment in cervical cancer is seen in patients with shorter overall treatment time (OTT), shorter interval between end of definitive CT-RT and beginning of brachytherapy and squamous cell histology. The study also noted the trend of increasing mean EQD2 to tumor with increasing stage for achieving complete response. Higher acute bladder and rectal toxicity is seen in patients who received EQD2 of ¿70-90Gy3 and ¿70Gy3 respectively. The study findings suggest that the clinical outcomes and the toxicities are clinically comparable with other radioisotope based HDR brachytherapy treatment.

UNASSIGNED: Approximately 20% of women worldwide have a retroverted uterus. A retroverted uterus is closer to the rectum and may cause toxicity during brachytherapy. Upon manipulation, a small percentage turn anteverted. Conventional brachytherapy applicators are designed for an anteverted uterus and can pose issues during insertion. Modified Fletcher suit and ring applicators have major differences in their geometry to achieve similar target coverage, and were analyzed in this study with respect to immediate adverse events and dosimetry.
UNASSIGNED: Three hundred seventy-four consecutive applications performed over a 20-month period were studied retrospectively to identify intra-cavitary applications (ICAs) in retroverted uteri. Cases were divided into 2 groups: modified Fletcher suit applicator with hemi-ovoids (group A) and ring applicator (group B). D2cc for bladder and rectum were noted, and acute adverse events were recorded.
UNASSIGNED: Seventy-five applications were identified, out of which 47 cases used Fletcher suit applicator, and 28 cases used ring applicator. The median bladder D2cc for group A and B were 5.98 Gy and 6.3 Gy, respectively, and the median rectum D2cc was 5.27 Gy and 3.68 Gy, respectively; the median dose prescribed to point A was 6 Gy (range, 5.5-9.0 Gy). All patients had a point A coverage between 97% and 102%. Eighteen cases in both groups complained of pain requiring analgesics. Twenty-five cases (53.2%) and 20 cases (71.4%) in group A and B, respectively, required dose optimization, which was statistically insignificant (p > 0.11). A significant difference was identified (p < 0.00001) in rectal doses. A higher reported pain was noted in ring applicator group (p < 0.03). No patient experienced a profuse bleeding.
UNASSIGNED: In most parameters, the two applicators demonstrated comparable results. The control of rectal dosage is superior in the ring applicator at the cost of higher pain incidence. Patient\'s comfort and rectal dose in EBRT should be taken into consideration, with preference given to the ring applicator.

Introduction: The aim of this study was to demonstrate the potential of an in vivo four-dimensional (4D) tracking system to accurately localize the radiation source, Iridium-192 (Ir-192) in high-dose rate brachytherapy. Methods: To achieve time-dependent 3D positioning of the Ir-192 source, we devised a 4D tracking system employing multiple compact detectors. During the system\'s design phase, we conducted comprehensive optimization and analytical evaluations of the diverging collimator employed for detection purposes. Subsequently, we executed 3D reconstruction and positioning procedures based on the 2D images obtained by six detectors, each equipped with an optimized diverging collimator. All simulations for designing and evaluating the 4D tracking system were performed using the open-source GATE (v9.1) Monte Carlo platform based on the GEANT4 (v10.7) toolkit. In addition, to evaluate the accuracy of the proposed 4D tracking system, we conducted simulations and 3D positioning using a solid phantom and patient data. Finally, the error between the reconstructed position coordinates determined by the tracking system and the original coordinates of the Ir-192 radiation source was analyzed. Results: The parameters for the optimized diverging collimator were a septal thickness of 0.3 mm and a collimator height of 30 mm. A tracking system comprising 6 compact detectors was designed and implemented utilizing this collimator. Analysis of the accuracy of the proposed Ir-192 source tracking system found that the average of the absolute values of the error between the 3D reconstructed and original positions for the simulation with the solid phantom were 0.440 mm for the x coordinate, 0.423 mm for the y coordinate, and 0.764 mm for the z coordinate, and the average Euclidean distance was 1.146 mm. Finally, in a simulation based on data from a patient who underwent brachytherapy, the average Euclidean distance between the original and reconstructed source position was 0.586 mm. Discussion: These results indicated that the newly designed in vivo 4D tracking system for monitoring the Ir-192 source during brachytherapy could determine the 3D position of the radiation source in real time during treatment. We conclude that the proposed positioning system has the potential to make brachytherapy more accurate and reliable.

OBJECTIVE: To present the outcome and toxicity results of a prospective trial of 21 Gy single fraction high-dose-rate (HDR) brachytherapy for men with low- or intermediate-risk prostate cancer.
METHODS: Patients were treated according to an IRB-approved prospective study of single fraction HDR brachytherapy. Eligible patients had low- or intermediate-risk prostate cancer with tumor stage ≤ T2b, PSA ≤ 15, and Gleason score ≤ 7. Patients underwent trans-rectal ultrasound-guided trans-perineal implant of the prostate followed by single fraction HDR brachytherapy to a dose of 21 Gy. The primary endpoint was grade ≥ 2 urinary/GI toxicity rates.
RESULTS: Twenty-six patients were enrolled with a median follow up of 5.1 years and median age of 64 years. 88.5% of patients had T1 disease, 15.4% had Gleason score 6 (84.6% Gleason 7), and median pre-treatment PSA was 5.0 ng/mL. Acute and chronic grade ≥ 2 urinary toxicity rates were 38.5% and 38.5%, respectively. There were no grade ≥ 2 acute or chronic GI toxicities. Six (23.1%) patients experienced biochemical failure, six (23.1%) patients experienced radiographic local failure, and five (19.2%) patients had biopsy-proven local failure. No patients developed regional lymph node recurrence or distant metastasis. 5-year overall survival and cause-specific survival were 96.2% and 100%, respectively.
CONCLUSIONS: 21 Gy single fraction HDR brachytherapy was associated with modestly higher-than-anticipated chronic urinary toxicity, as well as high biochemical and local failure rates. The results from this prospective pilot study do not support the use of this regimen in standard clinical practice.

BACKGROUND: Complex intracavity and interstitial (IC/IS) applicators, such as the Venezia applicator, can improve the HR-CTV coverage while adequately protecting organs at risk in the treatment of cervical cancer with high-dose-rate (HDR) brachytherapy. Although the Venezia applicator offers more choice for catheter selection, commercially available catheter and dose optimization algorithms are still missing for complex applicators. Moreover, studies on catheter and dose optimization for IC/IS implants in the treatment of cervical cancer are still limited.
OBJECTIVE: This work aims to combine a GPU-based multi-criteria optimization (gMCO) algorithm with a sparse catheter (SC) optimization algorithm for the Venezia applicator.
METHODS: Fifty-eight cervical cancer patients who received 28 Gy in 4 fx of HDR brachytherapy with the Venezia applicator (combination to external beam radiation therapy) are retrospectively revisited. The modelization of the applicator is done by virtually reconstructing all the IS catheters passing through the ring. Template catheters are reconstructed using an in-house python script. To perform simultaneous MCO and SC optimization (SC+MCO), the objective function includes aggregated dose objectives in a weighted sum and a group sparsity term that individually penalizes the contribution of IS catheters. Plans generated with the SC+MCO algorithm are compared with plans generated with MCO using clinical catheters (CC+MCO) and the clinical plans (CP). The EMBRACE II soft constraints (planning aims) and hard constraints (limits for prescribed dose) are used as plan evaluation criteria.
RESULTS: CC+MCO gives the most important gain with an increase up to 20.7% in meeting all EMBRACE II soft constraints compared with CP. The SC+MCO algorithm (adding catheter optimization to MCO) provides a second order increase (up to 12.1% with total acceptance rate of 60.3% or 35/58) in the acceptance rate versus CC+MCO (total increase of 32.8% vs. CP). Acceptance rate in EMBRACE II hard constraints is 98.3% (57/58) for both CC+MCO and SC+MCO versus 91.4% (53/58) for CP. The median SC+MCO optimization time is 11 s to generate a total of 5000 Pareto-optimal plans with different catheter configurations (position and number) for each fraction.
CONCLUSIONS: Simultaneous catheter and MCO optimization is clinically feasible for HDR cervical cancer brachytherapy using the Venezia applicator. Clinical catheter configurations could be improved and/or the catheter number could be reduced without decreasing plan quality using SC+MCO compared with the CP.

Objective. Precise monitoring of the position and dwell time of iridium-192 (Ir-192) during high-dose-rate (HDR) brachytherapy is crucial to avoid serious damage to normal tissues. Source imaging using a compact gamma camera is a potential approach for monitoring. However, images from the gamma camera are affected by blurring and statistical noise, which impact the accuracy of source position monitoring. This study aimed to develop a deep-learning approach for estimating ideal source images that reduce the effect of blurring and statistical noise from experimental images captured using a compact gamma camera.Approach. A double pix2pix model was trained using the simulated gamma camera images of an Ir-192 source. The first model was responsible for denoising the Ir-192 images, whereas the second model performed super resolution. Trained models were then applied to the experimental images to estimate the ideal images.Main results. At a distance of 100 mm between the compact gamma camera and the Ir-192 source, the difference in full width at half maximum (FWHM) between the estimated and actual source sizes was approximately 0.5 mm for a measurement time of 1.5 s. This difference has been improved from approximately 2.7 mm without the use of DL. Even with a measurement time of 0.1 s, the ideal images could be estimated as accurately as in the 1.5 s measurements. This method consistently achieved accurate estimations of the source images at any position within the field of view; however, the difference increased with the distance between the Ir-192 source and the compact gamma camera.Significance. The proposed method successfully provided estimated images from the experimental images within errors smaller than 0.5 mm at 100 mm. This method is promising for reducing blurring and statistical noise from the experimental images, enabling precise real-time monitoring of Ir-192 sources during HDR brachytherapy.

To demonstrate novel clinical implementation of a 3D transvaginal ultrasound (3DTVUS) system for intraoperative needle insertion guidance in perineal template interstitial gynecologic high-dose-rate brachytherapy and assess its impact on implant quality.
Interstitial implants began with preimplant 3DTVUS to visualize the tumor and anatomy, with intermittent 3DTVUS to assess the implant and guide needle adjustment. Analysis includes visualization of the implant relative to anatomy, identification of cases where 3DTVUS is beneficial, dosimetry, and a survey distributed to 3DTVUS clinicians.
Seven patients treated between November 2021 and October 2022 were included in this study. Twenty needles were inserted under 3DTVUS guidance. The tumor and vaginal wall were well-differentiated in four and all seven patients, respectively. Patients with tumours below the superior aspect of the vagina are suited for 3DTVUS. Four radiation oncologists responded to the survey. There was general agreement that 3DTVUS improves implant and anatomy visualization and is preferred over standard 2D ultrasound guidance techniques.
Based on qualitative feedback from primary users and a small preliminary patient cohort, 3DTVUS imaging improves tumor and vaginal wall visualization during gynecologic perineal template interstitial needle implant and is a powerful tool for implant assessment in an intraoperative setting.

OBJECTIVE: To calculate the dose distribution using Monte Carlo simulations for a novel high-dose-rate Yttrium-90 (Y-90) disc source recently developed for episcleral brachytherapy and provide a lookup table for treatment planning.
METHODS: Monte Carlo simulations were performed to calculate the in-water dose distribution of the Y-90 disc source using the \"GATE\", a software based on the \"Geant4\" Monte Carlo simulation toolkit developed by the international OpenGATE collaboration. The geometry of this novel beta source, its capsule, and the surrounding water medium were accurately modeled in the simulation input files. The standard Y-90 element beta spectrum from ICRU 72 was used, and the physics processes for beta and photon interactions with matters were all included. The dose distribution of this Y-90 disc source was measured in a separate study using Gafchromic EBT-3 films and the results were reported elsewhere. To match the setup of the experiment, a Gafchromic EBT-3 film was also included in the simulation geometry. The simulated dose profiles were exported from the 3D dose distribution results and compared with the measured dose profiles. Transverse dose profiles at different distances from the seed surface were also obtained to study the lateral coverage of the source.
RESULTS: The measured percent depth dose (PDD) curves along the central axis perpendicular to the surface of the Y-90 disc were constructed from the experimental and simulated data, and normalized to the reference point at 1 mm from the source capsule. Both PDD curves agreed well up to 4 mm from the source surface (maximum difference ± 10%) but deviated from each other beyond 4 mm. The deviation might be caused by the increased measurement uncertainty in the low-dose region. The dose rate at the reference point calculated from the Monte Carlo simulation was 1.09 cGy/mCi-s and agreed very well with the measured dose rate of 1.05 cGy/mCi-s. If the 80% isodose line is selected as the lateral coverage, the lateral dose coverage is maximal (∼4.5 mm) at the plane next to the source surface, and gradually decreases with the increasing distance, approaching 3.5 mm when the plane is 5 mm from the 6-mm diameter source surface.
CONCLUSIONS: Monte Carlo simulations were successfully performed to confirm the measured PDD curve of the novel Y-90 disc source. This simulation work laid a solid foundation for characterizing the full dosimetry parameters of this source for episcleral brachytherapy applications.

OBJECTIVE: To quantify the dose distribution effect of insufficient scattering conditions in keloid HDR brachytherapy with Freiburg fFlap (FF) applicator.
METHODS: A phantom composed of FF applicator, MatriXX and solid water slices was designed and scanned for treatment planning. Bolus with different thicknesses were covered to offer different scatter conditions. Planar dose distributions were measured by MatriXX. The maximum value (Max), average value (Avg) and γ passing rate (3 mm/3%) were evaluated by the software MyQA Platform.
RESULTS: The maximum and average doses measured by MatriXX were lower than the calculated values. The difference increased as field size decreased. The Max value, found at 0.86 cm level in the two tube case, was -20.0%, and the avg value was -11.9%. All the γ values were less than 95%. This difference gradually decreased with increasing bolus thickness and the γ values were significantly improved.
CONCLUSIONS: MatriXX could be used for dose verification of HDR brachytherapy with an FF applicator. When the FF applicator was applied for keloid, insufficient scattering conditions would cause an insufficient target dose. This difference could be reduced by covering the bolus with different thicknesses on the applicator. The smaller the field, the thicker the bolus required.