Comparison of failure modes and effects analyses and time for brachytherapy ring and tandem applicator digitization between manual and solid applicator source placement methods.

PURPOSE: Ring and tandem (R&T) applicator digitization is currently performed at our institution by manually defining the extent of the applicators. Digitization can also be achieved using solid applicators: predefined, 3D models with geometric constraints. This study compares R&T digitization using manual and solid applicator methods through Failure Modes and Effects Analyses (FMEAs) and comparative time studies. We aim to assess the suitability of solid applicator method implementation for R&T cases METHODS: Six qualified medical physicists (QMPs) and two medical physics residents scored potential modes of failure of manual digitization in an FMEA as recommended by TG-100. Occurrence, severity, and detectability (OSD) values were averaged across respondents and then multiplied to form combined Risk Priority Numbers (RPNs) for analysis. Participants were trained to perform treatment planning using a developed solid applicator protocol and asked to score a second FMEA on the distinct process steps from the manual method. For both methods, participant digitization was timed. FMEA and time data were analyzed across methods and participant samples RESULTS: QMPs rated the RPNs of the current, manual method of digitization statistically lower than residents did. When comparing the unique FMEA steps between the two digitization methods, QMP respondents found no significant difference in RPN means. Residents, however, rated the solid applicator method as higher risk. Further, after the solid applicator method was performed twice by participants, the time to digitize plans was not significantly different from manual digitization CONCLUSIONS: This study indicates the non-inferiority of the solid applicator method to manual digitization in terms of risk, according to QMPs, and time, across all participants. Differences were found in FMEA evaluation and solid applicator technique adoption based on years of brachytherapy experience. Further practice with the solid applicator protocol is recommended because familiarity is expected to lower FMEA occurrence ratings and further reduce digitization times.

Dosimetric comparison of volumetric modulated arc therapy (VMAT) and high-dose-rate brachytherapy (HDR-BT) for superficial skin irradiation with significant curvature in one or more planes.

PURPOSE: This study compares the plan quality of high-dose-rate brachytherapy (HDR-BT) and volumetric modulated arc therapy (VMAT) for superficial irradiation of large areas of skin with significant curvature in one or more planes. METHODS: A total of 14 patients from two centres previously treated with either HDR-BT or VMAT were retrospectively replanned using the alternative technique. Sites included scalp and lower limbs. Identical computed tomography (CT) scans, clinical target volume (CTV) and organs at risk (OARs) and prescription were used for both techniques. Conformity, skin surface dose and OAR doses were compared. RESULTS: Conformity index was consistently better with VMAT than HDR-BT (p < 0.01). Maximum skin surface dose (D0.1cc) had a higher mean of 49.6 Gy with HDR-BT compared to 31.4 Gy for VMAT (p < 0.01). Significantly smaller volumes of healthy tissue were irradiated with VMAT than with HDR-BT. This can be seen in brain volumes receiving 10, 20 and 30 Gy EQD2 and in extremities receiving 5 and 10 Gy. When close to the volume, the lens received significantly lower doses with VMAT (p < 0.01). CONCLUSION: In this small sample, VMAT gives equal coverage with lower OAR and skin surface doses than HDR-BT for both scalp and extremities. VMAT is a useful technique for treating large, superficial volumes with significant curvature in one or more planes.

Brachytherapy with Iodine-125 seeds for treatment of portal vein-branch tumor thrombus in patients with hepatocellular carcinoma.

BACKGROUND: There is currently no widely-accepted consensus for the management of hepatocellular carcinoma with portal vein tumor thrombus. We evaluate the safety and efficacy of ultrasound-guided percutaneous brachytherapy with iodine-125 seeds for the treatment of hepatocellular carcinoma with portal vein-branch tumor thrombus (PVBTT). METHODS: Sixty-nine hepatocellular carcinoma patients with PVBTT were enrolled; 34 received transarterial chemoembolization (TACE) combined with iodine-125 seeds implanted in the PVBTT; 35 were treated with TACE alone. Adverse events, objective response rate, disease control rate, progression-free survival, and overall survival were compared between the two groups. Tumor responses of PVBTT and intrahepatic tumor were correlated. Multivariate and subgroup analyses were conducted for overall survival. RESULTS: No grade 3 or 4 adverse events were recorded, and there was no difference in grade 1 or 2 adverse events between the two groups. Objective response rate and disease control rate for PVBTT were 58.9 and 91.2%, respectively, in the combined treatment group, which were significantly greater than the 5.7 and 54.3% rates, respectively, in the TACE-alone group (both p's ≤ 0.001). Intrahepatic tumor response was positively correlated with the PVBTT response (γ = 0.782, p < 0.01). Survival outcomes were better in the combined treatment group than in the TACE-alone group: the median progression-free survival for PVBTT was 9 months versus 3 months (HR = 0.187 [95% CI: 0.101, 0.345], p < 0.001), and the median overall survival was 11 months versus 7 months (HR = 0.448 [95% CI: 0.265, 0.758], p = 0.003). Multivariate analysis revealed that application of brachytherapy and lower grade PVBTT (Vp1 + Vp2 vs. Vp3) were protective predictors of overall survival. In stratified analysis, the benefit of overall survival was more significant in the subgroup of PVBTT Vp1 + Vp2 rather than in Vp3. CONCLUSIONS: The combination of iodine-125 seed brachytherapy guided by ultrasound and TACE is a convenient, safe, and effective treatment for patients with HCC and PVBTT, conferring a better survival benefit than TACE alone.

Dose reduction in HDR brachytherapy of esophageal cancer using gold and gold alloy plaques: a Monte Carlo study.

In this work, the use of gold and gold alloy plaques is proposed for the first time, to reduce the dose to healthy organs in brachytherapy with Ir-192 sources. For dose simulations in tumour and healthy tissue, the MCNPX Monte Carlo code was used. The radiation source implemented in those simulations was benchmarked with well-known TG-43 criteria of dose rate constant, air-kerma strength, radial dose function, and 2D anisotropy function. For various arrangements of iridium sources and plaques of gold and gold alloy of various thicknesses, the dose distributions in an esophagus tumour and in surrounding healthy organs were simulated. The results showed that while the dose to the tumour is not much affected by the presence of gold plaques with a thickness of 3.5 mm in an optimized 192Ir sources' configuration, a relative reduction in average organ dose of 64%, 65%, 73%, 67%, and 35% was observed, for esophagus, thyroid, heart, stomach, and liver, respectively. Moreover, it was found that a gold plaque leads to smaller doses to healthy organs than a gold alloy plaque. It is concluded that gold plaques can be used to improve the treatment of esophageal cancer by HDR brachytherapy and to protect surrounding non-target organs.

Evaluation of radioactive 125I seed implantation for the treatment of refractory malignant tumours based on a CT-guided 3D template-assisted technique: efficacy and safety.

BACKGROUND: To observe the medium- and long-term clinical efficacy and safety of radioactive 125I seed implantation for refractory malignant tumours based on CT-guided 3D template-assisted technique. METHODS: Twenty-five patients with refractory malignant tumours who underwent radioactive 125I seed implantation based on CT-guided 3D template-assisted technique were selected. The post-operative adverse reactions were recorded. The number of puncture needles and particles used in the operation, dosimetric parameters, post-operative physical strength scores, and tumour response were statistically analysed. The overall survival time and survival rate were calculated, and the effect and prognosis were assessed. RESULTS: 125I seed implantation was successful in all patients without serious complications. The average number of implanted puncture needles was 17 (19.12 ± 13.00), and the median number of particles was 52 (55.12 ± 32.97). D90 in the post-operative clinical target volume (CTV) (93.24 ± 15.70 Gy) was slightly lower than that in the pre-operative CTV (93.92 ± 17.60 Gy; P > 0.05). The D90 in the post-operative planning target volume (PTV) (142.16 ± 22.25 Gy) was lower than the pre-operative PTV (145.32 ± 23.48 Gy; P > 0.05). The tumour responses at 6 months post-operatively: complete remission (CR), 20% (5/25); partial remission (PR), 48% (12/25); stable disease (SD), 24% (6/25); progressive disease (PD), 8% (2/25); CR + PR, 68% (17/25); and local control rate, 92% (23/25). The 6-, 12-, and 24-month survival rates were 100, 88, and 52%, respectively. The post-operative physical strength score (Karnofsky performance score, KPS) exhibited a gradual trend towards recovery, which rose to the highest value 12 months after implantation and then decreased slightly, but the average score was still > 90 points. There was one intra-operative pneumothorax, and two patients with superficial malignant tumours developed skin ulcerations. Multivariate analysis of prognosis showed that tumour sites and types were independent risk factors affecting survival. The number of needles and particles and template types were not the factors. CONCLUSIONS: 3D template combined with CT-guided radioactive 125I seed implantation can improve the rational distribution of radiation dose in the tumour target area because accurate radioactive 125I particle implantation was achieved. This technique has fewer complications and can further extend the overall survival and improve the quality of life. TRIAL REGISTRATION: Registration number: ChiCTR2000034566 2020/7/10 0:00:00 Retrospectively registered.

The use of hyperbaric oxygen to treat actinic rectal fistula after SpaceOAR use and radiotherapy for prostate cancer: a case report.

BACKGROUND: In definitive radiation therapy for prostate cancer, the SpaceOAR® System, a hydrogel spacer, is widely used to decrease the irradiated dose and toxicity of rectum. On the other hand, periprostatic abscesses formation and rectal perforation are known as rare adverse effects of SpaceOAR. Nevertheless, there is a lack of reports clarifying the association between aggravation of abscesses and radiation therapy, and hyperbaric oxygen therapy (HBOT) is effective for a peri-SpaceOAR abscess and rectal perforation. CASE PRESENTATION: We report a case of a 78-year-old high-risk prostate cancer patient. After SpaceOAR insertion into the correct space, he started to receive external beam radiation therapy (EBRT). He developed a fever, perineal pain and frequent urination after the completion of EBRT, and the magnetic resonance imaging (MRI) revealed a peri-SpaceOAR abscess. Scheduled brachytherapy was postponed, administration of antibiotics and opioid via intravenous drip was commenced, and transperineal drainage was performed. After the alleviation of the abscess, additional EBRT instead of brachytherapy was performed with MRI-guided radiation therapy (MRgRT). On the last day of the MRgRT, perineal pain reoccurred, and MRI and colonoscopy detected the rectal perforation. He received an intravenous antibiotics drip and HBOT, and fully recovered from the rectal perforation. CONCLUSIONS: Our report indicates that EBRT can lead to a severe rectum complication by causing inflammation for patients with a peri-SpaceOAR abscess. Furthermore, HBOT was effective for the peri-SpaceOAR abscess and rectal perforation associated with EBRT.

A multiwell applicator for conformal brachytherapy of superficial skin tumors: A simulation study.

BACKGROUND: Brachytherapy of thin skin tumors using beta particles can protect underlying sensitive structures such as the bone because of the rapid dose falloff of this type of radiation in tissue. The current work describes a skin brachytherapy applicator, based on beta radiation, that can provide the needed cell-killing radiation dose matched to the shape of individual skin tumors. MATERIALS AND METHODS: The applicator and its template were fabricated using 3D printing technology. Any clinically approved beta-emitting isotope in the form of a radioactive gel could theoretically be used in this applicator. Monte Carlo simulations were employed to study the capability of the applicator in conforming dose distribution based on the shape of the tumor. Dose profile in the shallow depth, transverse dose profiles at different depths, and the percent depth dose from this applicator were calculated. The radioisotope of choice for our calculations was Yttrium-90 (Y-90). RESULTS: Using the proposed applicator, it is possible to create a desired dose profile matching the tumor surface shape. CONCLUSION: The short-range of the beta radiation, together with the dose conforming capability of the applicator, may lead to minimal interactions with the healthy tissue around the skin lesion.

Evaluation of the dosimetric impact of manufacturing variations for the INTRABEAM x-ray source.

INTRODUCTION: INTRABEAM x-ray sources (XRSs) have distinct output characteristics due to subtle variations between the ideal and manufactured products. The objective of this study is to intercompare 15 XRSs and to dosimetrically quantify the impact of manufacturing variations on the delivered dose. METHODS AND MATERIALS: The normality of the XRS datasets was evaluated with the Shapiro-Wilk test, the accuracy of the calibrated depth-dose curves (DDCs) was validated with ionization chamber measurements, and the shape of each DDC was evaluated using depth-dose ratios (DDRs). For 20 Gy prescribed to the spherical applicator surface, the dose was computed at 5-mm and 10-mm depths from the spherical applicator surface for all XRSs. RESULTS: At 5-, 10-, 20-, and 30-mm depths from the source, the coefficient of variation (CV) of the XRS output for 40 kVp was 4.4%, 2.8%, 2.0%, and 3.1% and for 50 kVp was 4.2%, 3.8%, 3.8%, and 3.4%, respectively. At a 20-mm depth from the source, the 40-kVp energy had a mean output in Gy/Minute = 0.36, standard deviation (SD) = 0.0072, minimum output = 0.34, and maximum output = 0.37 and a 50-kVp energy had a mean output = 0.56, SD = 0.021, minimum output = 0.52, and maximum output = 0.60. We noted the maximum DRR values of 2.8% and 2.5% for 40 kVp and 50 kVp, respectively. For all XRSs, the maximum dosimetric effect of these variations within a 10-mm depth of the applicator surface is ≤ 2.5%. The CV increased as depth increased and as applicator size decreased. CONCLUSION: The American Association of Physicist in Medicine Task Group-167 requires that the impurities in radionuclides used for brachytherapy produce ≤ 5.0% dosimetric variations. Because of differences in an XRS output and DDC, we have demonstrated the dosimetric variations within a 10-mm depth of the applicator surface to be ≤ 2.5%.

Development and clinical implementation of SeedNet: A sliding-window convolutional neural network for radioactive seed identification in MRI-assisted radiosurgery (MARS).

PURPOSE: To develop and evaluate a sliding-window convolutional neural network (CNN) for radioactive seed identification in MRI of the prostate after permanent implant brachytherapy. METHODS: Sixty-eight patients underwent prostate cancer low-dose-rate (LDR) brachytherapy using radioactive seeds stranded with positive contrast MR-signal seed markers and were scanned using a balanced steady-state free precession pulse sequence with and without an endorectal coil (ERC). A sliding-window CNN algorithm (SeedNet) was developed to scan the prostate images using 3D sub-windows and to identify the implanted radioactive seeds. The algorithm was trained on sub-windows extracted from 18 patient images. Seed detection performance was evaluated by computing precision, recall, F1 -score, false discovery rate, and false-negative rate. Seed localization performance was evaluated by computing the RMS error (RMSE) between the manually identified and algorithm-inferred seed locations. SeedNet was implemented into a clinical software package and evaluated on sub-windows extracted from 40 test patients. RESULTS: SeedNet achieved 97.6 ± 2.2% recall and 97.2 ± 1.9% precision for radioactive seed detection and 0.19 ± 0.04 mm RMSE for seed localization in the images acquired with an ERC. Without the ERC, the recall remained high, but the false-positive rate increased; the RMSE of the seed locations increased marginally. The clinical integration of SeedNet slightly increased the run-time, but the overall run-time was still low. CONCLUSION: SeedNet can be used to perform automated radioactive seed identification in prostate MRI after LDR brachytherapy. Image quality improvement through pulse sequence optimization is expected to improve SeedNet's performance when imaging without an ERC.

Off-axis dose distribution with stand-in and stand-off configurations for superficial radiotherapy treatments.

Current practice when delivering dose for superficial skin radiotherapy is to adjust the monitor units so that the prescribed dose is delivered to the central axis of the superficial unit applicator. Variations of source-to-surface distance due to patient's anatomy protruding into the applicator or extending away from the applicator require adjustments to the monitor units using the inverse square law. Off-axis dose distribution varies significantly from the central axis dose and is not currently being quantified. The dose falloff at the periphery of the field is not symmetrical in the anode-cathode axis due to the heel effect. This study was conducted to quantify the variation of dose across the surface being treated and model a simple geometric shape to estimate a patient's surface with stand-in and stand-off. Isodose plots and color-coded dose distribution maps were produced from scans of GAFChromic EBT-3 film irradiated by a Gulmay D3300 orthovoltage x-ray therapy system. It was clear that larger applicators show a greater dose falloff toward the periphery than smaller applicators. Larger applicators were found to have a lower percentage of points above 90% of central axis dose (SA90). Current clinical practice does not take this field variation into account. Stand-in can result in significant dose falloff off-axis depending on the depth and width of the protrusion, while stand-off can result in a flatter field due to the high-dose region near the central axis being further from the source than the peripheral regions. The central axis also received a 7% increased or decreased dose for stand-in or stand-off, respectively.

Clinical implementation, logistics and workflow guide for MRI image based interstitial HDR brachytherapy for gynecological cancers.

Interstitial brachytherapy (IBT) is often utilized to treat women with bulky endometrial or cervical cancers not amendable to intracavitary treatments. A modern trend in IBT is the utilization of magnetic resonance imaging (MRI) with a high dose rate (HDR) afterloader for conformal 3D image-based treatments. The challenging part of this procedure is to properly complete many sequenced and co-related physics preparations. We presented the physics preparations and clinical workflow required for implementing MRI-based HDR IBT (MRI-HDR-IBT) of gynecologic cancer patients in a high-volume brachytherapy center. The present document is designed to focus on the clinical steps required from a physicist's standpoint. Those steps include: (a) testing IBT equipment with MRI scanner, (b) preparation of templates and catheters, (c) preparation of MRI line markers, (d) acquisition, importation and registration of MRI images, (e) development of treatment plans and (f) treatment evaluation and documentation. The checklists of imaging acquisition, registration and plan development are also presented. Based on the TG-100 recommendations, a workflow chart, a fault tree analysis and an error-solution table listing the speculated errors and solutions of each step are provided. Our workflow and practice indicated the MRI-HDR-IBT is achievable in most radiation oncology clinics if the following equipment is available: MRI scanner, CT (computed tomography) scanner, MRI/CT compatible templates and applicators, MRI line markers, HDR afterloader and a brachytherapy treatment planning system capable of utilizing MRI images. The OR/procedure room availability and anesthesiology support are also important. The techniques and approaches adopted from the GEC-ESTRO (Groupe Européen de Curiethérapie - European Society for Therapeutic Radiology and Oncology) recommendations and other publications are proven to be feasible. The MRI-HDR-IBT program can be developed over time and progressively validated through clinical experience, this document is expected to serve as a reference workflow guideline for implementing and performing the procedure.

A novel and innovative device to retract rectum during radiation therapy of pelvic tumors.

An effective radiotherapy treatment entails maximizing radiation dose to the tumor while sparing the surrounding and normal tissues. With the advent of SBRT with extreme hypo-fractionation in treating tumors including prostate where ablative dose is delivered in smaller number of fractions, rectum remains a dose-limiting organ and at the risk of rectal toxicity or secondary cancer. The same limitation of rectal toxicity exists for high-dose rate (HDR) treatments of cervical, endometrial, or prostate cancer when creating even a short distance between the anterior rectal wall and field of radiation is ideal in delivering ablative dose to the target. An effective solution to such problem is to physically displace rectum as the organ at risk. This research presents an organ retractor device that is designed to displace the rectum away from the path of radiation beam employing a Nitinol shape memory alloy that is designed for displacing the rectum upon actuation. A control system regulates the motion in a reproducible and safe manner by creating the desirable shape in moving the anterior rectal wall. The study finds the novel organ retractor device to be a promising tool that can be applied in a clinical setting for minimizing dose to the rectum during treatment of pelvic tumors, and creating the potential to deliver an ablative dose to tumor volume or to escalate the dose when needed.

Technical assessment of a mobile CT scanner for image-guided brachytherapy.

PURPOSE: The imaging performance and dose of a mobile CT scanner (Brainlab Airo®, Munich, Germany) is evaluated, with particular consideration to assessment of technique protocols for image-guided brachytherapy. METHOD: Dose measurements were performed using a 100-mm-length pencil chamber at the center and periphery of 16- and 32-cm-diameter CTDI phantoms. Hounsfield unit (HU) accuracy and linearity were assessed using materials of specified electron density (Gammex RMI, Madison, WI), and image uniformity, noise, and noise-power spectrum (NPS) were evaluated in a 20-cm-diameter water phantom as well as an American College of Radiology (ACR) CT accreditation phantom (Model 464, Sun Nuclear, Melbourne, FL). Spatial resolution (modulation transfer function, MTF) was assessed with an edge-spread phantom and visually assessed with respect to line-pair patterns in the ACR phantom and in structures of interest in anthropomorphic phantoms. Images were also obtained on a diagnostic CT scanner (Big Bore CT simulator, Philips, Amsterdam, Netherlands) for qualitative and quantitative comparison. The manufacturer's metal artifact reduction (MAR) algorithm was assessed in an anthropomorphic body phantom containing surgical instrumentation. Performance in application to brachytherapy was assessed with a set of anthropomorphic brachytherapy phantoms - for example, a vaginal cylinder and interstitial ring and tandem. RESULT: Nominal dose for helical and axial modes, respectively, was 56.4 and 78.9 mGy for the head protocol and 17.8 and 24.9 mGy for the body protocol. A high degree of HU accuracy and linearity was observed for both axial and helical scan modes. Image nonuniformity (e.g., cupping artifact) in the transverse (x,y) plane was less than 5 HU, but stitching artifacts (~5 HU) in the longitudinal (z) direction were observed in axial scan mode. Helical and axial modes demonstrated comparable spatial resolution of ~5 lp/cm, with the MTF reduced to 10% at ~0.38 mm-1 . Contrast-to-noise ratio was suitable to soft-tissue visualization (e.g., fat and muscle), but windmill artifacts were observed in helical mode in relation to high-frequency bone and metal. The MAR algorithm provided modest improvement to image quality. Overall, image quality appeared suitable to relevant clinical tasks in intracavitary and interstitial (e.g., gynecological) brachytherapy, including visualization of soft-tissue structures in proximity to the applicators. CONCLUSION: The technical assessment highlighted key characteristics of dose and imaging performance pertinent to incorporation of the mobile CT scanner in clinical procedures, helping to inform clinical deployment and technique protocol selection in brachytherapy. For this and other possible applications, the work helps to identify protocols that could reduce radiation dose and/or improve image quality. The work also identified areas for future improvement, including reduction of stitching, windmill, and metal artifacts.

Preliminary report of a single-channel applicator in high dose rate afterloading brachytherapy for cervical cancer.

The aim of this study was to evaluate whether a patented single-channel applicator, which was modified from the traditional tandem applicator and wrapped with an oval-shield alloy around the source channel, has the same clinical efficacy and safety as the standard Fletcher-type applicator in high dose rate (HDR) brachytherapy for carcinoma of the cervix. Between December 2011 and February 2017, 299 patients with pathologically confirmed International Federation of Gynecology and Obstetrics (2009) stage Ib2-IVa cervical cancer were recruited to the trial and finished the allocated intervention. Of the first 151 patients, 71 were allocated to the Fletcher group and 80 to the single-channel group, satisfying the criteria for a preliminary analysis. All but 3 patients were treated with concurrent cisplatin chemotherapy and external beam radiotherapy followed by HDR brachytherapy. The 2-year overall survival, progression-free survival, and locoregional failure-free survival was 80.3%, 77.5%, and 78.9%, respectively, for the Fletcher group, and 86.3%, 82.5%, and 83.8%, respectively, for the single-channel group. The seriousness of acute treatment-related toxicities was similar in the 2 groups. The cumulative rate of late rectal complications of grade 3-4 in the Fletcher group and the single-channel group was 2.8% and 2.5%, respectively. The cumulative rate of grade 3 bladder complications was 2.8% for the Fletcher group and 1.3% for the single-channel group. The preliminary results of our study show that the patented single-channel intracavitary applicator might be able to provide protection for the rectum and bladder and seems to have the same clinical efficacy as the standard Fletcher-type 3-channel applicator in HDR brachytherapy for carcinoma of the cervix. This trial was registered with the Chinese Clinical Trial Registry (registration no. ChiCTR-TRC-12002321).

Irradiation stents vs. conventional metal stents for unresectable malignant biliary obstruction: A multicenter trial.

BACKGROUND & AIMS: Placement of an irradiation stent has been demonstrated to offer longer patency and survival than an uncovered self-expandable metallic stent (SEMS) in patients with unresectable malignant biliary obstruction (MBO). We aim to further assess the efficacy of an irradiation stent compared to an uncovered SEMS in those patients. METHODS: We performed a randomized, open-label trial of participants with unresectable MBO at 20 centers in China. A total of 328 participants were allocated in parallel to the irradiation stent group (ISG) or the uncovered SEMS group (USG). Endpoints included stent patency (primary), technical success, relief of jaundice, overall survival, and complications. RESULTS: The first quartile stent patency time (when 25% of the patients experienced stent restenosis) was 212 days for the ISG and 104 days for the USG. Irradiation stents were significantly associated with a decrease in the rate of stent restenosis (9% vs. 15% at 90 days; 16% vs. 27% at 180 days; 21% vs. 33% at 360 days; p = 0.010). Patients in the ISG obtained longer survival time (median 202 days vs. 140 days; p = 0.020). No significant results were observed in technical success rate (93% vs. 95%; p = 0.499), relief of jaundice (85% vs. 80%; p = 0.308), and the incidence of grade 3 and 4 complications (8.5% vs. 7.9%; p = 0.841). CONCLUSIONS: Insertion of irradiation stents instead of uncovered SEMS could improve patency and overall survival in patients with unresectable MBO. LAY SUMMARY: For patients with unresectable malignant biliary obstruction (MBO), placement of a self-expandable metallic stent (SEMS) is a recommended palliative modality to relieve pruritus, cholangitis, pain, and jaundice. However, restenosis is a main pitfall after stent placement. Data from this first multicenter randomized controlled trial showed that insertion of an irradiation stent provided longer patency and better survival than a conventional metal stent. ClinicalTrials.gov ID: NCT02001779.

Accuracy assessment of a potential clinical use of navigation-guided intra-operative liver metastasis brachytherapy-a planning study.

For patients with inoperable liver metastases, intra-operative liver high dose-rate brachytherapy (HDR-BT) is a promising technology enabling delivery of a high radiation dose to the tumor, while sparing healthy tissue. Liver brachytherapy has been described in the literature as safe and effective for the treatment of primary or secondary hepatic malignancies. It is preferred over other ablative techniques for lesions that are either larger than 4 cm or located in close proximity to large vessels or the common bile duct. In contrast to external beam radiation techniques, organ movements do not affect the size of the irradiated volume in intra-operative HDR-BT and new technical solutions exist to support image guidance for intra-operative HDR-BT. We have retrospectively analyzed anonymized CT datasets of 5 patients who underwent open liver surgery (resection and/or ablation) in order to test whether the accuracy of a new image-guidance method specifically adapted for intra-operative HDR-BT is high enough to use it in similar situations and whether patients could potentially benefit from navigation-guided intra-operative needle placement for liver HDR-BT.

Decrease in uterine perforations with ultrasound image-guided applicator insertion in intracavitary brachytherapy for cervical cancer: A systematic review and meta-analysis.

PURPOSE: To estimate uterine perforations rates during intracavitary brachytherapy for cervical cancer with and without ultrasound (US) image guidance. MATERIALS AND METHODS: A systematic search of databases (PubMed and EMBASE) was performed. The pooled summary uterine perforation rate (detected by postinsertion CT or MRI) for the un-guided insertion group and the guided insertion group was calculated by using the random-effects model weighted by the inverse variance. RESULTS: A total of 690 articles were initially found, resulting in 12 studies that met the inclusion criteria. A total of 1757 insertions and 766 patients were included in the meta-analysis. The overall uterine perforation rate per insertion was 4.56% (95%CI: 2.35-8.67) and per patient was 7.39% (95%CI: 3.92-13.50). The pooled perforation rate per insertion without image guidance was 10.54% (95%CI: 6.12-17.57) versus 1.06% (95%CI: 0.41-2.67) with image guidance (p < 0.01). The pooled perforation rate per patient without guidance was 16.67% (95%CI: 10.01-26.45) versus 2.54% (95%CI: 1.21-5.24) with image guidance (p < 0.01). The ratio of perforations in the un-guided/guided groups was 9.94 and 6.56, per insertion and per patient, respectively. The most common sites of perforation were the posterior wall (>47 events) and the uterine fundus (24 events). None of the studies reported significant acute clinical consequences. Prophylactic antibiotic after perforation was used in 3 of the 4 studies that described the management. CONCLUSION: Using postinsertion CT or MRI to detect the perforation, the rate of uterine perforation per insertion in patients who received US-guided intracavitary brachytherapy insertion is 90% lower than with un-guided insertion.

Dosimetric assessment of an air-filled balloon applicator in HDR vaginal cuff brachytherapy using the Monte Carlo method.

PURPOSE: As an alternative to cylindrical applicators, air-inflated balloon applicators have been introduced into high-dose-rate (HDR) vaginal cuff brachytherapy to achieve sufficient dose to the vagina mucosa as well as to spare organs at risk, mainly the rectum and bladder. Commercial treatment planning systems which employ formulae in the AAPM Task Group No. 43 (TG 43) report do not take into account tissue inhomogeneity. Consequently, the low-density air in a balloon applicator induces different doses delivered to the mucosa from planned by these planning systems. In this study, we investigated the dosimetric effects of the air in a balloon applicator using the Monte Carlo (MC) method. METHODS: The thirteen-catheter Capri™ applicator by Varian™ for vaginal cuff brachytherapy was modeled together with the Ir-192 radioactive source for the microSelectron™ Digital (HDR-V3) afterloader by Elekta™ using the MCNP MC code. The validity of charged particle equilibrium (CPE) with an air balloon present was evaluated by comparing the kerma and the absorbed dose at various distances from the applicator surface. By comparing MC results with and without air cavity present, dosimetric effects of the air cavity were studied. Clinical patient cases with optimized multiple Ir-192 source dwell positions were also explored. Four treatment plans by the Oncentra Brachy™ treatment planning system were re-calculated with MCNP. RESULTS: CPE fails in the vicinity of the air-water interface. One millimeter beyond the air-water boundary the kerma and the absorbed dose are equal (0.2% difference), regardless of air cavity dimensions or iridium source locations in the balloon. The air cavity results in dose increase, due to less photon absorption in the air than in water or solid materials. The extent of the increase depends on the diameter of the air balloon. The average increment is 3.8%, 4.5% and 5.3% for 3.0, 3.5, and 4.0 cm applicators, respectively. In patient cases, the dose to the mucosa is also increased with the air cavity present. The point dose difference between Oncentra Brachy and MC at 5 mm prescription depth is 8% at most and 5% on average. CONCLUSIONS: Except in the vicinity of the air-mucosa interface, the dosimetric difference is not significant enough to mandate tissue inhomogeneity correction in HDR treatment planning.

COMP report: CPQR technical quality control guidelines for brachytherapy remote afterloaders.

The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an acceptable level of radiation treatment quality. The TQC guidelines have been rigorously reviewed and field tested in a variety of Canadian radiation treatment facilities. The development process enables rapid review and update to keep the guidelines current with changes in technology (the most updated version of this guideline can be found on the CPQR website). This particular TQC details recommended quality control testing of brachytherapy remote afterloaders.

Reduction of seed motion using a bio-absorbable polymer coating during permanent prostate brachytherapy using a mick applicator technique.

PURPOSE: The addition of a braided bio-absorbable vicryl coating to the surface of radioactive seeds used for low dose rate (LDR) prostate brachytherapy is intended to reduce the incidence of seed movement and migration. Here, we present a single-institution study of the frequency and severity of seed slippage (initial seed movement) of coated seeds in comparison with uncoated seeds. METHODS: Forty-seven patients received permanent prostate brachytherapy, with either coated (n = 26) or uncoated (n = 21) seeds. AgX100 125 I seeds, coated or uncoated, and uncoated Model 200 103 Pd seeds were used. During the ultrasound-guided implantation procedure, each implanted seed was categorized as having remained in the implanted position after being placed, having moved slightly, or having left the ultrasound field of view. RESULTS: 3.1% of the coated seeds (AgX100 seeds, n = 70) and 6.9% of the uncoated seeds (AgX100 and Model 200 seeds, n = 128) were observed to have moved at least 2 mm from their initial implant positions, respectively. The difference in incidence of this movement was 54.4% (P = 0.0026). Coated AgX100 seeds demonstrated a 66.7% lower rate of movement of at least 2 mm than that for uncoated AgX100 seeds (P = 0.038), and a 49.0% lower rate than that for Model 200 seeds (P = 0.021). While no significant differences were noted in prescription dose coverage of the prostate or the studied dosimetric parameters for the organs at risk between the coated and uncoated seeds (P > 0.05) in the CT-based Day-0 postoperative plans, the limited sample size and differences in energies between the 125 I and 103 Pd seeds make further analysis of postoperative dosimetric coverage difficult without additional data directly comparing the coated and uncoated 125 I seeds. CONCLUSION: When the vicryl coating is used, seeds have a significantly lower propensity to slip from their initial implant locations. This may help maintain dosimetric integrity, warranting further study of postoperative dosimetry.