ABSTRACT
Purpose: An incident review of errors related to using high-dose-rate brachytherapy (HDR-BT) and associated patient safety program were presented. This study was based on 9 years' experience using VariSource afterloader system. Material and methods: Analysis was made on radiotherapy (RT) incidents (including near-misses) that were routinely recorded using manual and electronic incident reporting systems between July 2012 and December 2021. Each incident's origin was categorized as 'apparatus', 'system functionality', 'treatment procedure', and 'other causes'. Results: From 8,100 fractions and 2,216 patients, there were 164 RT incidents. The most frequent cases included non-dosimetric errors arising from system malfunction (49/151), difficulties caused by insufficient instruments (47/151), problems with treatment delivery (55/151), and planning procedure errors (13/142). Eleven incidents were near-misses, another 11 were not harmful, and zero were harmful. The frequency rate of dosimetric errors was 0.14 per 100 BT insertions, and 0.5 per 100 patients. The review also discovered 45 of the 164 incidents related to tube sensor failures and source blockages. These delivery errors were associated with 0.56 incidents per 100 insertions and 2.03 incidents per 100 patients, inconveniencing patients in treatment delays. Conclusions: The effectiveness of our HDR-BT safety program was evidenced by low-rate of dosimetric errors. Based on the analysis of 9 years of incidents, the error sources included uncommon or complex procedures, human factors, and work environment (equipment availability and maintenance).
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PURPOSE: This study was performed using end-to-end testing and real-time in vivo skin dose measurements, using metal oxide semiconductor field effect transistor (MOSFET) dosimeters on our first chronic psoriasis patient treated with iridium-192 (192Ir) high-dose-rate (HDR) brachytherapy (BT). MATERIAL AND METHODS: Treatment delivery was planned with the prescription dose of 1.8 Gy to a 3 mm depth for 12 fractions, using our custom-fabricated surface mold and Varian soft catheters. The optimal technique to provide an adequate and acceptable skin dose as well as its feasibility were evaluated by an end-to-end exercise using a perspex finger phantom. The accuracy and reliability of MOSFET dose measurement was explored with a thermoluminescence dosimetry (TLD) before being used in vivo to monitor skin doses during treatment delivery for each BT fraction. RESULTS: Using custom-made surface mold (2.4 mm Med-Tec thermoplastic mask for hand fixation and 5 applicators attached to each finger for dose delivery), the optimal skin dose on the phantom was obtained without the need for additional bolus to increase thickness of applicator. We acquired mean skin doses at different skin depths from various dose-volume parameters of no-bolus and 3 mm-added bolus plans. They were 125% and 110% (1 mm), 120% and 108% (2 mm), and 114% and 106% (3 mm), respectively. There was excellent agreement between MOSFET and TLD for 192Ir HDR-BT within ±3% (mean 2.65%, SD = 2.05%). With no energy correction, MOSFET overestimated the Acuros BV surface doses by up to 7% in the phantom study and in the clinical case. CONCLUSIONS: We demonstrated achievable HDR-BT for our first case of nail bed psoriasis. The end-to-end exercise was an efficient methodology to evaluate new feasibility for this technique. Real-time dose monitoring using MOSFET was an effective and reliable tool to ensure treatment quality and patient safety.
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AIM: In this study, an accuracy survey of intensity-modulated radiation therapy (IMRT) and volumetric arc radiation therapy (VMAT) implementation in radiotherapy centers in Thailand was conducted. BACKGROUND: It is well recognized that there is a need for radiotherapy centers to evaluate the accuracy levels of their current practices, and use the related information to identify opportunities for future development. MATERIALS AND METHODS: An end-to-end test using a CIRS thorax phantom was carried out at 8 participating centers. Based on each center's protocol for simulation and planning, linac-based IMRT or VMAT plans were generated following the IAEA (CRP E24017) guidelines. Point doses in the region of PTVs and OARs were obtained from 5 ionization chamber readings and the dose distribution from the radiochromic films. The global gamma indices of the measurement doses and the treatment planning system calculation doses were compared. RESULTS: The large majority of the RT centers (6/8) fulfilled the dosimetric goals, with the measured and calculated doses at the specification points agreeing within ±3% for PTV and ±5% for OARS. At 2 centers, TPS underestimated the lung doses by about 6% and spinal cord doses by 8%. The mean percentage gamma pass rates for the 8 centers were 98.29 ± 0.67% (for the 3%/3 mm criterion) and 96.72 ± 0.84% (for the 2%/2 mm criterion). CONCLUSIONS: The 8 participating RT centers achieved a satisfactory quality level of IMRT/VMAT clinical implementation.
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PURPOSE: The dose distributions obtained from three imaging approaches for target delineation in cervical cancer using high-dose-rate (HDR) brachytherapy were investigated. MATERIAL AND METHODS: Ten cervical cancer patients receiving four fractions of HDR brachytherapy were enrolled. Based on different imaging approaches, three brachytherapy plans were developed for each patient: with the high-risk clinical target volume (HRCTV) delineated on magnetic resonance (MRI) images for every fraction (approach A; MRI-only); on MRI for the first fraction and computed tomography (CT) images for the subsequent fractions (approach B; MRI1st/CT); and on CT images for all fractions (approach C; CT-only). The volume, height, width at point A, width at maximum level, and dosimetric parameters (D100, D98, D95, and D90 of the HRCTV; and D0.1cc, D1cc, and D2cc of all organs at risk, or organ at risk - OAR: bladder, rectum, sigmoid colon, and bowel) provided by each approach were compared. RESULTS: The mean HRCTV volume, width, and height obtained from approach C (CT-only) were overestimated compared to those from approaches A (MRI-only) and B (MRI1st/CT). The doses to the HRCTV for approaches A and B were similar. However, the HRCTV doses for approach C were significantly lower than those for approaches A and B for all parameters (D95-D100). As to the OAR, the three approaches showed no differences. CONCLUSIONS: A combination of MRI and CT is a safe alternative approach for cervical cancer HDR brachytherapy. The technique provides comparable dosimetric outcomes to MRI-based planning, while being more cost-effective.
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PURPOSE: Titanium ring cap applicator (VariSource) was applied in treating cervical cancer patients by using image-guided brachytherapy (IGBT). However, its sizes appeared to be relatively large for most of our patients. Thus, we have developed a specific applicator "Siriraj Ring Cap," which is slightly smaller and more suitable for our patients. This study was to evaluate effectiveness of this equipment. METHODS AND MATERIALS: Locally advanced cervical cancer patients were treated with external beam radiation therapy with or without concomitant chemotherapy. Siriraj Ring Cap was applied in all of the patients for at least one fraction. Dosimetric analysis was performed in each fraction of IGBT. Clinical outcomes of these patients were evaluated. RESULTS: Twenty-nine patients with 117 dosimetric planning were evaluated between January and December of 2014. Siriraj Ring Cap was fit to all patients in this study. By using this applicator, radiation doses to the targets (D90 high-risk clinical target volume and D90 intermediate-risk clinical target volume) were higher in each fraction. There were no statistically differences of radiation doses to the bladder, rectum, sigmoid colon, and small bowel. Within 2-year followup, 3 patients (10.3%) developed locoregional recurrence. Two-year disease-free survival and overall survival were 75.9% and 89.7%, respectively. According to RTOG/EORTC complication criteria, Grade 1, 2, and 3 gastrointestinal complications were developed in 2 (6.9%), 4 (13.8%), and 1 (3.4%) patients, respectively. For genitourinary complications, 3 patients (10.3%) and 1 patient (3.4%) had Grades 1 and 2, respectively. CONCLUSIONS: Siriraj Ring Cap is feasible for IGBT in cervical cancer patients with narrow vagina. Dosimetry and clinical outcomes were satisfactory by using our specific applicator.
