Physics and Dosimetric Principles of SRS and SBRT

Charlie, C.‐M.

doi:10.30654/mjcs.10022

Cited by 10 publications

(8 citation statements)

References 33 publications

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“…The ITV is the internal target volume margin added to compensate for the internal physiologic movement and variations in tumor position for particular body sites affected by respiratory motion, such as lung or liver tumors. The PTV is a safety margin that accounts for systematic and random uncertainties in dose delivery and treatment planning 23 . In stereotactic radiotherapy, GTV is usually equal to CTV, and both are sometimes equal to the PTV; however, the latter depends upon the immobilization and tracking system used.…”

Section: Technical Prerequisitesmentioning

confidence: 99%

Stereotactic radiotherapy: An educational narrative review

Khan,

Hashmi,

et al. 2024

Precision Radiation Oncology

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Stereotactic radiotherapy is a term collectively used to describe the radiation treatment techniques that allow for the delivery of highly precise ionizing radiation. It is usually a high dose per session in single or few fractions. This treatment approach has been in medical use for over six decades and has primarily evolved in the last two decades. Many patients benefit from this unique non‐conventional radiotherapy approach. Its indications include various malignant, benign and functional problems in cranial and body sites. This technique is not widespread in developing countries compared to developed countries. This work is an educational narrative review for learners in radiation oncology. We aim to share the knowledge of this practice to improve precision radiation oncology globally. This review summarizes the basics of stereotactic radiotherapy, the technical prerequisites, the clinical considerations, the practical recommendations and the learning points from each site‐specific region.

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Section: Technical Prerequisitesmentioning

confidence: 99%

Stereotactic radiotherapy: An educational narrative review

Khan,

Hashmi,

et al. 2024

Precision Radiation Oncology

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“…11,12 Dose calculation algorithms in radiotherapy treatment planning systems have progressed from correctionbased methods to model-based methods (convolution methods), and most recently to Monte Carlo-type algorithms. 13 Among these advancements, tissue and material heterogeneity is increasingly better addressed to improve dose calculation accuracy. Based on different levels of accuracy, modern dose algorithms are often categorized into Type-A (the least accurate algorithms such as pencil beam), Type-B (the middle-tier, currently standard-of -care, algorithms such as convolution superposition algorithms and the analytical anisotropic algorithm or AAA in Varian Eclipse), and Type-C (the most accurate commercial algorithms such as VMC and AXB).…”

Section: Introductionmentioning

confidence: 99%

“…Dose calculation algorithms in radiotherapy treatment planning systems have progressed from correction‐based methods to model‐based methods (convolution methods), and most recently to Monte Carlo‐type algorithms 13 . Among these advancements, tissue and material heterogeneity is increasingly better addressed to improve dose calculation accuracy.…”

Section: Introductionmentioning

confidence: 99%

A comprehensive evaluation of advanced dose calculation algorithms for brain stereotactic radiosurgery

Yoon,

Jung,

Tanny

et al. 2023

J Applied Clin Med Phys

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PurposeAccurate dose calculation is important in both target and low dose normal tissue regions for brain stereotactic radiosurgery (SRS). In this study, we aim to evaluate the dosimetric accuracy of the two advanced dose calculation algorithms for brain SRS.MethodsRetrospective clinical case study and phantom study were performed. For the clinical study, 138 SRS patient plans (443 targets) were generated using BrainLab Elements Voxel Monte Carlo (VMC). To evaluate the dose calculation accuracy, the plans were exported into Eclipse and recalculated with Acuros XB (AXB) algorithm with identical beam parameters. The calculated dose at the target center (Dref), dose to 95% target volume (D95), and the average dose to target (Dmean) were compared. Also, the distance from the skull was analyzed. For the phantom study, a cylindrical phantom and a head phantom were used, and the delivered dose was measured by an ion chamber and EBT3 film, respectively, at various locations. The measurement was compared with the calculated doses from VMC and AXB.ResultsIn clinical cases, VMC dose calculations tended to be higher than AXB. It was found that the difference in Dref showed > 5% in some cases for smaller volumes < 0.3 cm3. Dmean and D95 differences were also higher for small targets. No obvious trend was found between the dose difference and the distance from the skull. In phantom studies, VMC dose was also higher than AXB for smaller targets, and VMC showed better agreement with the measurements than AXB for both point dose and high dose spread.ConclusionThe two advanced calculation algorithms were extensively compared. For brain SRS, AXB sometimes calculates a noticeable lower target dose for small targets than VMC, and VMC tends to have a slightly closer agreement with measurements than AXB.

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“…Highly conformal treatments of small cranial lesions utilize a technique known as Stereotactic Radiosurgery (SRS) which aims to achieve sub‐mm target localization in all three spatial dimensions 1 . Compared with conventionally‐fractionated treatments, single‐fraction SRS and few‐fraction stereotactic radiotherapy (SRT) are characterized by large doses per fraction, high dose conformity, and strict patient positioning tolerances 2 . Several approaches have been developed to deliver these treatments, including VMAT and stereotactic cones.…”

Section: Introductionmentioning

confidence: 99%

Investigating the impacts of intrafraction motion on dosimetric outcomes when treating small targets with virtual cones

Church

Parsons

Syme

2021

J Applied Clin Med Phys

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Purpose: Intrafraction patient motion is a well-documented phenomenon in radiation therapy. In stereotactic radiosurgery applications in which target sizes can be very small and dose gradients very steep, patient motion can significantly impact the magnitude and positional accuracy of the delivered dose. This work investigates the impact of intrafraction motion on dose metrics for small targets when treated with a virtual cone.Materials and Methods: Monte Carlo simulations were performed to calculate dose kernels for treatment apertures ranging from 1 × 2.5 mm 2 to 10 × 10 mm 2 . The phantom was an 8.2-cm diameter sphere and isotropic voxels had lengths of 0.25 mm. Simulated treatments consisted of 3 arcs: 1 axial arc (360°gantry rotation, couch angle 0°) and 2 oblique arcs (180°gantry rotation, couch angle AE45°). Dose distributions were calculated via superposition of the rotated kernels. Two different collimator orientations were considered to create a virtual cone: (a) each treatment arc was delivered twice, once each with a static collimator angle of AE45°, and (b) each treatment arc was delivered once, with dynamic collimator rotation throughout the arc. Two different intrafraction motion patterns were considered: (a) constant linear motion and (b) sudden, persistent motion. The impact of motion on dose distributions for target sizes ranging from 1 to 10 mm diameter spheres was quantified as a function of the aperture size used to treat the lesions.Results: The impact of motion on both the target and the surrounding tissue was a function of both aperture shape and target size. When a 0.5-mm linear drift along each dimension occurred during treatment, targets ≥5 mm saw less than a 10% decrease in coverage by the prescription dose. Smaller apertures accrued larger penalties with respect to dosimetric hotspots seen in the tissues surrounding the target volume during intrafraction motion. For example, treating a 4-mm-sized target that undergoes 2.60 mm (3D vector) of continuous linear motion, the D 5 in the concentric shells that extend 1, 2, and 3 mm from the surface of the target was 39%, 24%, and 14% smaller, respectively when comparing the delivery of a larger aperture (6 × 10 mm 2 ) to a smaller aperture (2 × 5 mm 2 ). Using a static collimator for shaping a virtual cone during treatment minimized the dosimetric impact of motion

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Physics and Dosimetric Principles of SRS and SBRT

Cited by 10 publications

References 33 publications

Stereotactic radiotherapy: An educational narrative review

Stereotactic radiotherapy: An educational narrative review

A comprehensive evaluation of advanced dose calculation algorithms for brain stereotactic radiosurgery

Investigating the impacts of intrafraction motion on dosimetric outcomes when treating small targets with virtual cones

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