Is 5 mm MMLC suitable for VMAT‐based lung SBRT? A dosimetric comparison with 2.5 mm HDMLC using RTOG‐0813 treatment planning criteria for both conventional and high‐dose flattening filter‐free photon beams

Subramanian, S.; Subramani, V.; Swamy, Shivakumar; Garg, Arun; Chilukuri, Srinivas; Kathirvel, M

doi:10.1120/jacmp.v16i4.5415

Cited by 10 publications

(10 citation statements)

References 21 publications

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“…In this work, we have investigated only the low‐density range for clinical energies of interest in the small field sizes, due to inherent limitations of the 3'D printing fabrication process employed. That said, the investigation of small field size and low‐density tissue range for AXB validation is of clinical relevance as these conditions are akin to those of lung SBRT treatments, which has been a topic of interest with respect to the application of AXB 21, 22, 23, 24, 25…”

Section: Introductionmentioning

confidence: 99%

Verification of Acuros XB dose algorithm using 3D printed low‐density phantoms for clinical photon beams

Zavan

McGeachy

Madamesila

et al. 2018

J Applied Clin Med Phys

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The transport‐based dose calculation algorithm Acuros XB (AXB) has been shown to accurately account for heterogeneities primarily through comparisons with Monte Carlo simulations. This study aims to provide additional experimental verification of AXB for clinically relevant flattened and unflattened beam energies in low density phantoms of the same material. Polystyrene slabs were created using a bench‐top 3D printer. Six slabs were printed at varying densities from 0.23 to 0.68 g/cm3, corresponding to different density humanoid tissues. The slabs were used to form different single and multilayer geometries. Dose was calculated with Eclipse™ AXB 11.0.31 for 6MV, 15MV flattened and 6FFF (flattening filter free) energies for field sizes of 2 × 2 and 5 × 5 cm2. EBT3 film was inserted into the phantoms, which were irradiated. Absolute dose profiles and 2D Gamma analyses were performed for 96 dose planes. For all single slab configurations and energies, absolute dose differences between the AXB calculation and film measurements remained <3% for both fields in the high‐dose region, however, larger disagreement was seen within the penumbra. For the multilayered phantom, percentage depth dose with AXB was within 5% of discrete film measurements. The Gamma index at 2%/2 mm averaged 98% in all combinations of fields, phantoms and photon energies. The transport‐based dose algorithm AXB is in good agreement with the experimental measurements for small field sizes using 6MV, 6FFF and 15MV beams adjacent to various low‐density heterogeneous media. This work provides preliminary experimental grounds to support the use of AXB for heterogeneous dose calculation purposes.

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Section: Introductionmentioning

confidence: 99%

Verification of Acuros XB dose algorithm using 3D printed low‐density phantoms for clinical photon beams

Zavan

McGeachy

Madamesila

et al. 2018

J Applied Clin Med Phys

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“…14 regards the definition of the clinical target volume (CTV) (RPN = 64). This represents a critical point involving the Radiation Oncologist and the Surgeon: underdosing of the target and/or unintended normal tissues irradiation can occur ( 14 ). The exact evaluation of the dimensions of the tumor on preoperative diagnostic imaging and an accurate intraoperative definition of the CTV determined a significant RPN reduction from 64 to 16 (RR: 48; 75%).…”

Section: Discussionmentioning

confidence: 99%

“…18) involves the Physicist and the preparation of the gafchromic film for in vivo dosimetry (RPN = 60). A wrong calibration of the gafchromic film or an inadequate placement of the film on top of the internal shield can cause a wrong evaluation of the dose delivered ( 14 ). These risks were prevented first of all by following the “ in vivo dosimetry” Procedure, elaborated by the Physicist, with an RPN reduction from 60 to 32 (RR: 28; 46.7%), and then by labeling the gafchromic film and employing a double check in the procedure with a further reduction of RPN from 32 to 4 (RR: 28; 87.5%).…”

Section: Discussionmentioning

confidence: 99%

“…Absent or incomplete adherence of the applicator to the tumor bed, determined by air gap presence, blood accumulation, or very curved tumor bed, can cause a non-homogeneous irradiation ( 14 ). Corrective actions, such as an accurate visual control and the correct placement of the patient on the operating table, reduced the risk ranking from 64 to 36 (RR: 28; 43.8%) after 2 years and from 36 to 24 in the next 2 years (RR: 12; 33.3%) employing a double check.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, to avoid shielding disk misalignment, the Surgeon and the Radiation Oncologist decided to design a new shielding set-up, implementing an elastic band fixed by stitches to the pectoralis fascia, thus preventing the disk slipping ( 14 ) (Figure 3 ).…”

Section: Discussionmentioning

confidence: 99%

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FMECA Application to Intraoperative Electron Beam Radiotherapy Procedure As a Quality Method to Prevent and Reduce Patient’s Risk in Conservative Surgery for Breast Cancer

et al. 2017

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IntroductionFailure Mode Effects and Criticalities Analysis (FMECA) represents a prospective method for risk assessment in complex medical practices. Our objective was to describe the application of FMECA approach to intraoperative electron beam radiotherapy (IOERT), delivered using a mobile linear accelerator, for the treatment of early breast cancer as an anticipated boost.Materials and methodsA multidisciplinary Working Group, including several different professional profiles, was created before the beginning of clinical practice in 2012, with the purpose of writing the Flow Chart and applying the FMECA methodology to IOERT procedure. Several criticalities were identified a priori in the different steps of the procedure and a list of all potential failure modes (FMs) was drafted and ranked using the risk priority number (RPN) scoring system, based on the product of three parameters: severity, occurrence, and detectability (score between 1 and 5). The actions aimed at reducing the risk were then defined by the Working Group and the risk analysis was repeated in 2014 and in 2016, in order to assess the improvement achieved.ResultsFifty-one FMs were identified, which represented the issues prospectively investigated according to the FMECA methodology. Considering a set threshold of 30, the evaluated RPNs show that 33 out of 51 FMs are critical; 6 are included in the moderate risk class (RPN: 31–40); 16 in the intermediate risk class (RPN: 41–50), and 11 in the high risk class (RPN: >50).DiscussionThe most critical steps concerned the surgical procedure and IOERT set-up. The introduction of the corrective actions into the clinical practice achieved the reduction of the RPNs in the re-analysis of the FMECA worksheet after 2 and 4 years, respectively.ConclusionFMECA proved to be a useful tool for prospective evaluation of potential failures in IOERT and contributed to optimize patient safety and to improve risk management culture among all the professionals of the Working Group.

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Dosimetric evaluation of MRI‐guided multi‐leaf collimator tracking and trailing for lung stereotactic body radiation therapy

et al. 2021

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The treatment margins for lung stereotactic body radiotherapy (SBRT) are often large to cover the tumor excursions resulting from respiration, such that underdosage of the tumor can be avoided. Magnetic resonance imaging (MRI)-guided multi-leaf collimator (MLC) tracking can potentially reduce the influence of respiration to allow for smaller treatment margins. However, tracking is accompanied by system latency that may induce residual tracking errors. Alternatively, a simpler mid-position delivery combined with trailing can be used. Trailing reduces influences of respiration by compensating for baseline motion, to potentially improve target coverage. In this study, we aim to show the feasibility of MRI-guided tracking and trailing to reduce influences of respiration during lung SBRT. Methods: We implemented MRI-guided tracking on the MR-linac using an Elekta research tracking interface to track tumor motion during intensity modulated radiotherapy (IMRT). A Quasar MRI 4D phantom was used to generate Lujan motion (cos 4 , 4 s period, 20 mm peak-to-peak amplitude) with and without 1.0 mm/min cranial drift. Phantom tumor positions were estimated from sagittal 2D cine-MRI (4 or 8 Hz) using cross-correlation-based template matching. To compensate the anticipated system latency, a linear ridge regression predictor was optimized for online MRI by comparing two predictor training approaches: training on multiple traces and training on a single trace. We created 15-beam clinical-grade lung SBRT plans for central targets (8 × 7.5 Gy) and peripheral targets (3 × 18 Gy) with different PTV margins for mid-position based motion management (3-5 mm) and for MLC tracking (3 mm). We used a film insert with a 3 cm spherical target to measure the spatial distribution and quantity of the delivered dose. A 1%/1 mm local gamma-analysis quantified dose differences between motion management strategies and reference cases. Additionally, a dose area histogram (DAH) revealed the target coverage relative to the reference scenario. Results: The prediction filter gain was on average 25% when trained on multiple traces and 44% when trained on a single trace. The filter reduced system latency from 313 AE 2 ms to 0 AE 5 ms for 4 Hz imaging and from 215 AE 3 ms to 3 AE 3 ms for 8 Hz. The local gamma analysis for the central delivery showed that tracking improved the gamma pass-rate from 23% to 96% for periodic motion and from 14% to 93% when baseline drift was applied. For the peripheral delivery during periodic motion, delivery pass-rates improved from 22% to 93%. Comparing mid-position delivery to trailing for periodic+drift motion increased the local gamma pass rate from 15% to 98% for a central delivery and from 8% to 98% for a peripheral delivery. Furthermore, the DAHs revealed a relative D 98% GTV coverage of 101% and 97% compared to the reference scenario for, respectively, central and peripheral tracking of periodic+drift motion. For trailing, a relative D 98% of 99% for central and 98% for peripheral trailing was found. Conclusions: We pro...

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Is 5 mm MMLC suitable for VMAT‐based lung SBRT? A dosimetric comparison with 2.5 mm HDMLC using RTOG‐0813 treatment planning criteria for both conventional and high‐dose flattening filter‐free photon beams

Cited by 10 publications

References 21 publications

Verification of Acuros XB dose algorithm using 3D printed low‐density phantoms for clinical photon beams

Verification of Acuros XB dose algorithm using 3D printed low‐density phantoms for clinical photon beams

FMECA Application to Intraoperative Electron Beam Radiotherapy Procedure As a Quality Method to Prevent and Reduce Patient’s Risk in Conservative Surgery for Breast Cancer

Dosimetric evaluation of MRI‐guided multi‐leaf collimator tracking and trailing for lung stereotactic body radiation therapy

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