BackgroundBrachytherapy (BT) treatments involving temporary high-dose rate (HDR) sources are extensively employed in clinical practice. Ensuring the consistency of all measurement equipment at the hospital level is crucial, requiring a robust redundancy and consistency program. This enables the institution to verify the stability of the dosimetry system over time.PurposeTo describe, justify, and analyze a component of the redundancy program of the calibration protocols followed by the Radiotherapy Department of the Hospital Universitari i Polit & egrave;cnic La Fe (Val & egrave;ncia, Spain) during the last 10 years for the case of HDR BT as an additional component to ensure long term stability of the measurement equipment.MethodsAt the time the HDR BT source is replaced, its Air Kerma Strength (SK) is measured. By comparing this value with the one obtained at the time of installation (corrected by decay), a clear determination of the stability of the measurement equipment can be performed.ResultsDifference between SK,vendor and SK,hosp as a function of the measurement date is reported for a 10 years' period. All measurements are well within the +/- 3% tolerance level recommended in current international guidelines. Percentage differences of SK,hosp values at the time of replacement compared to SK,hosp ones at the time when the source was installed are within the +/- 0.5% range, reflecting oscillations around a null deviation.ConclusionsThe method proposed allows any hospital to ensure a redundancy component of the long-term stability of all equipment involved in BT measurements in a very simple and time efficient manner. Additionally, it enables the hospital to maintain a detailed log of historical differences, facilitating the identification and correction of potential systematic deviations over time.

The aim of this work was to evaluate the inter- and intra-observer variation in contouring vestibular schwannoma (VS) and the organs-at-risk (OAR), and its dosimetric impact in Volumetric Modulated Arc Therapy (VMAT). Three VS typical cases were contoured by four clinicians. The Agreement Volume Index (AVI) appeared to be notably higher in VS than in OARs, such that the dose coverage of VS is fairly robust. In OARs, the largest variation was +1.02Gy in dmax for the brainstem, +0.78Gy in dmean for the cochlea and +1.05Gy in dmax of the trigeminal nerve. Accordingly, it was decided that all VS delineations for stereotactic radiosurgery (SRS), and all frame-based SRS contouring in general, should always be reviewed by a second physician. In addition, the retrospective presentation of VS cases at daily peer review meetings has also been adopted to ensure that the consensus is constantly updated, as well as for training purposes.

Purpose In the implementation of the use of EncompassTM partially open immobilization mask to perform SRS of multiple brain metastasis, the evaluation of patient's intrafraction motion (IM) is deemed convenient to verify that the margins applied to the GTV are able to ensure adequate dose coverage to each lesion. Methods IM was determined by comparing the pre- and post-treatment CBCT images with respect to the simulation CT for a total of 23 fractions. The dosimetric impact on GTV coverage due to translational errors in patient positioning and rotational uncertainties of LINAC's performance was also evaluated. Results The absolute magnitude of IM was less than 1 mm in all cases. The dosimetric difference on GTV coverage due to patient's IM was inferior to 5%. There was not found any significant correlation between the dosimetric impact of rotational uncertainties with the distance to the isocenter. Conclusion The margins applied to the GTV are adequate when using EncompassTM immobilization device.

La radioterapia adaptativa (Adaptive Radiation Therapy, ART) se puede definir como la modificación del plan de tratamiento administrado a un paciente durante el curso de la radioterapia para tener en cuenta los cambios en la anatomía. La aplicación de ART supone un cambio en el proceso radioterápico que implica el uso de numerosos recursos adicionales, no estando implementada de forma general. Así, aun tratándose de una idea introducida hace más de 20 años, todavía a fecha de hoy son objeto de estudio muchos de los aspectos que definen la ART: la decisión de proceder a la nueva planificación del tratamiento, el momento óptimo para adaptar el plan, el umbral dosimétrico o anatómico que define la necesidad de adaptar y la identificación de los pacientes que realmente se beneficiarían de la adaptación del tratamiento. Este informe del Grupo de Trabajo sobre ART de la Sociedad Española de Física Médica (SEFM) tiene como objetivo describir los principios de esta técnica, así como los elementos necesarios para su implementación. Se exponen las dos estrategias principales atendiendo al momento de su aplicación: offline, para actuar ante los cambios progresivos que se observan durante el tratamiento, y online, para mitigar los cambios aleatorios. Se revisa el estado actual de ART aplicado a la práctica clínica para diferentes localizaciones anatómicas. Se describen algunos de los instrumentos clave para su implementación: los algoritmos de registro deformable (Deformable Image Registration, DIR), exponiendo las principales métricas de similitud, los métodos de optimización de la similitud, y los modelos de deformación utilizados, analizando las características de los algoritmos de los softwares más utilizados. Además, dada la importancia que tiene conocer la incertidumbre adicional que introduce el uso de los algoritmos DIR (sobre todo cuando se utilizan para deformar la matriz de dosis absorbida) se dedica un apartado a la validación de estos algoritmos, incluyendo los resultados para los principales softwares comerciales disponibles actualmente. Por último, se presentan unas recomendaciones a la hora de aplicar ART en la práctica clínica.

Background: Utilization of stereotactic radiosurgery (SRS) for brain metastases (BM) has become the technique of choice as opposed to whole brain radiation therapy (WBRT). The aim of this work is to evaluate the feasibility and potential benefits in terms of normal tissue (NT) and dose escalation of volumetric modulated arc therapy (VMAT) in SRS metastasis treatment. A VMAT optimization procedure has therefore been developed for internal dose scaling which minimizes planner dependence. Materials and methods: Five patient-plans incorporating treatment with frame-based SRS with dynamic conformal arc technique (DA) were re-planned for VMAT. The lesions selected were between 4-6 cm(3). The same geometry used in the DA plans was maintained for the VMAT cases. A VMAT planning procedure was performed attempting to scale the dose in inner auxiliary volumes, and to explore the potential for dose scaling with this technique. Comparison of dose-volume histogram (DVH) parameters were obtained. Results: VMAT allows a superior NT sparing plus conformity and dose scaling using the auxiliary volumes. The VMAT results were significantly superior in NT sparing, improving both the V-10 and V-12 values in all cases, with a 2-3 cm(3) saving. In addition, VMAT improves the dose coverage D-95 by about 05 Gy. The objective of dose escalation was achieved with VMAT with an increment of the Dmean and the Dmedian of about 2 Gy. Conclusions: This work shows a benefit of VMAT in SRS treatment with significant NT sparing. AVMAT optimization procedure, based on auxiliary inner volumes, has been developed, enabling internal dose escalation.

Peer review has been proposed as a strategy to ensure patient safety and plan quality in radiation oncology. Despite its potential benefits, barriers commonly exist to its optimal implementation in daily clinical routine. Our purpose is to analyze peer-review process at our institution. Based on our group peer-review process, we quantified the rate of plan changes, time and resources needed for this process. Prospectively, data on cases presented at our institutional peer-review conference attended by physicians, resident physicians and physicists were collected. Items such as time to present per case, type of patient (adult or pediatric), treatment intent, dose, aimed technique, disease location and receipt of previous radiation were gathered. Cases were then analyzed to determine the rate of major change, minor change and plan rejection after presentation as well as the median time per session. Over a period of 4 weeks, 148 cases were reviewed. Median of attendants was six physicians, three in-training-physicians and one physicist. Median time per session was 38 (4–72) minutes. 59.5% of cases presented in 1–4 min, 32.4% in 5–9 min and 8.1% in ≥ 10 min. 79.1% of cases were accepted without changes, 11.5% with minor changes, 6% with major changes and 3.4% were rejected with indication of new presentation. Most frequent reason of change was contouring corrections (53.8%) followed by dose or fractionation (26.9%). Everyday group consensus peer review is an efficient manner to recollect clinical and technical data of cases presented to ensure quality radiation care before initiation of treatment as well as ensuring department quality in a feedback team environment. This model is feasible within the normal operation of every radiation oncology Department.

Purpose The ICRU 89 recommends reporting a set of vaginal dose points for cervical cancer treatments in order to quantify the goodness of implant. This vaginal dose reporting method for combined external beam radiotherapy and brachytherapy has been adopted by the EMBRACE II study protocol. Large variations in dose between patients and centers have been reported. The aim of this study was to determine possible discrepancies with consensus observers from the same institution. Therefore, the inter- and intra-observer variability were analyzed. Material and methods For five patients, five experienced observers reported dose at the proposed vaginal points twice. The effect of inter- and intra-observer variations on total dose was analyzed by estimating biologically equivalent dose EQD2 (α/β = 3 Gy). Coefficient of variation (CV) was used to provide a measure of data dispersion as a proportion to the mean. Results The maximum inter-observer deviation among all patients and all points ranged from 0.5 Gy to 24.1 Gy in EQD2. The higher inter-observer discrepancies were found at points at 3 o’clock and at 6 o’clock, with respect to ovoids. In case of the maximum intra-observer deviation, it ranged from 0.5 Gy to 14.2 Gy, with higher deviation points at 12 o’clock and 9 o’clock, with respect to ovoids. Conclusions There is a need to ensure consistency in vaginal points reporting. The impact of the dosimetric inter- and intra-observer variability should also be considered when dealing with dose tolerances and limits due to the potential dose gradient.

ESTRO 37 S568 months, 12/41 developed metastases during the observation period.Actuarial LC, PFS, and OS rates at 2/5 years were 94/94%, 69%/66%, and 82%/74%, respectively.All 4 ≥G3 toxicities occurred in this group.Conclusion Loco-regional recurrence in previously surgically treated EC patients can be successfully salvaged with modern radiation techniques including IGABT.Previous radiation does not preclude salvage therapy.If the relapse is limited to the vaginal wall, IGABT may be the therapy of choice, while in recurrences extending beyond the vaginal cuff and/or involving the pelvic lymph nodes a combination with pelvic EBRT seems appropriate.

Purpose:To estimate the sensitivity of TrueBeam 2.0 Imaging System 6DoF automatic matching tool through the acquisition of cone‐beam CT images in different phantoms applying submillimeter translations and rotations of tenths of a degree and registered with image simulation CT.Methods:To evaluate overall system‐wide image, we consider two uncertainties source; First, the uncertainty of the manual phantom displacement (ε_m). This uncertainty is calculated by a digital caliper (0.01 mm) for vertical (Vrt), lateral (Lat) and longitudinal (Lng). A digital inclinometer (0.01°) for the pitch and roll and the own phantom scale to evaluate the coordinate rotation (Rtn). The second uncertainty is the displacement detected by the algorithm system of matching (σ_d) that we obtain from the standard deviations of the different measurements. We use three different phantoms. The BrainLab Radiosurgery system for supporting masks with an anthropomorphic dummy adapted to allow displacements of 0.1 mm in Vrt, Lat and Lng dimensions and rotations of 0.1° in Pitch dimension. For the analysis of the Rtn and Roll dimensions we use two homemade phantoms (RinoRot and RinoRoll, La Fe Hospital, Valencia, Spain) that allow rotations of 0.3°.Results:In the case of manual displacement of 0.10 ± 0.03 mm in the translations, the system detect 0.10 ± 0.07 mm, 0.12 ± 0.07 mm and 0.13 ± 0.07 mm (mean ± SD) in Lat, Vrt and Lng respectively. In the case of rotational dimension, manual displacement of 0.3 ± 0.1° was detected with 0.19 ± 0.06°, 0.29 ± 0.03° and 0.27 ± 0.06° in Pitch, Roll and Rtn.Conclusion:We conclude that the sensitivity of the automatic matching system is within 0.10 mm in translations and 0.3° in rotations. These values are under the own sensitivity of the software.