A Systematic Analysis of 2 Monoisocentric Techniques for the Treatment of Multiple Brain Metastases

Narayanasamy, G.; Stathakis, Sotirios; Gutiérrez, Alonso N.; Pappas, E.; Crownover, Richard; Floyd, John R.; Papanikolaou, Niko

doi:10.1177/1533034616666998

Cited by 22 publications

(33 citation statements)

References 19 publications

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“…Another study by Narayanasamy et al 25 compared 8 patients (40 targets) and concluded that the 2 techniques achieved comparable CI scores, V 12Gy (cm 3 ), and mean brain dose. However, limited case numbers likely provided insufficient power to detect detailed differences between the 2 treatment planning systems.…”

Section: Comparison Of Mean Brain Dose Between Techniquesmentioning

confidence: 99%

Interinstitutional Plan Quality Assessment of 2 Linac-Based, Single-Isocenter, Multiple Metastasis Radiosurgery Techniques

Liu

Thomas

et al. 2020

Advances in Radiation Oncology

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Purpose: Interest and application of stereotactic radiosurgery for multiple brain metastases continue to increase. Various planning systems are available for linear accelerator (linac)ebased single-isocenter multiple metastasis radiosurgery. Two of the most advanced systems are BrainLAB Multiple Metastases Elements (MME), a dynamic conformal arc (DCA) approach, and Varian RapidArc (RA), a volumetric modulated arc therapy (VMAT) approach. In this work, we systematically compared plan quality between the 2 techniques. Methods and Materials: Thirty patients with 4 to 10 metastases (217 total; median 7.5; V min Z 0.014 cm 3 ; V max Z 17.73 cm 3 ) were planned with both Varian RA and MME at 2 different institutions with extensive experience in each respective technique. All plans had a single isocenter and used Varian linac equipped with high-definition multileaf collimator. RA plans used 2 to 4 noncoplanar VMAT arcs with 10 MV flattening filter-free beam. MME plans used 4 to 9 noncoplanar DCAs and 6 MV flattening filter-free beam, (minimum planning target volume [PTV min] Z 0.49 cm 3 ; PTV max Z 27.32 cm 3 ; PTV median Z 7.05 cm 3 ). Prescriptions were 14 to 24 Gy in a single fraction. Target coverage goal was 99% of volume receiving prescription dose (D99% ! 100%). Plans were evaluated by Radiation Therapy Oncology Group/Paddick conformity index (CI) score, 12 Gy volume (V 12Gy ), V 8Gy , V 5Gy , mean brain dose (D mean ), and beam-on time.Results: Conformity was favorable among RA plans (median: MME CI RTOG Z 1.38; RA CI RTOG Z 1.21; P < .0001). V 12Gy and V 8Gy were lower for RA plans (median: MME V12 Z 23.7 cm 3 ; RA V12 Z 19.2 cm 3 ; P Z .0001; median: MME V 8Gy Z 53.6 cm 3 ; RA V 8Gy Z 44.1 cm 3 ; P Z .024). V 5Gy was lower for MME plans (median: MME V 5Gy Z 141.4 cm 3 ; RA V 5Gy Z 142.8 cm 3 ; P Z .009). Mean brain was lower for MME plans (median: MME D mean Z 2.57 Gy; RA D mean Z 2.76 Gy; P < .0001). Conclusions: For linac-based multiple metastasis stereotactic radiosurgery, RapidArc VMAT facilitates favorable conformity and V 12Gy /V 8Gy volume compared with the MME DCA plan. MME planning facilitates reduced dose spill at levels V 5Gy .

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Section: Comparison Of Mean Brain Dose Between Techniquesmentioning

confidence: 99%

Interinstitutional Plan Quality Assessment of 2 Linac-Based, Single-Isocenter, Multiple Metastasis Radiosurgery Techniques

Liu

Thomas

et al. 2020

Advances in Radiation Oncology

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“…Volumetric modulated arc therapy (VMAT) is commonly employed for SRS treatment delivery. Several studies have demonstrated that multiarc noncoplanar VMAT can deliver highly conformal plans to the target(s) and spare adjacent critical structures . More recently, single‐isocenter VMAT‐SRS treatment techniques were introduced for dose delivery to multiple intracranial targets/lesions concurrently, with the latter being an attractive approach since treatment duration can be further reduced without necessarily compromising plan quality .…”

Section: Introductionmentioning

confidence: 99%

“…Several studies have demonstrated that multiarc noncoplanar VMAT can deliver highly conformal plans to the target(s) and spare adjacent critical structures. [9][10][11][12][13][14][15][16] More recently, single-isocenter VMAT-SRS treatment techniques were introduced for dose delivery to multiple intracranial targets/lesions concurrently, with the latter being an attractive approach since treatment duration can be further reduced without necessarily compromising plan quality. [17][18][19] A single isocenter has been found sufficient for VMAT-SRS of multiple intracranial metastases, whereas minor improvements in plan quality can be achieved when additional isocenter(s) are used.…”

Section: Introductionmentioning

confidence: 99%

Dosimetric impact of rotational errors on the quality of VMAT‐SRS for multiple brain metastases: Comparison between single‐ and two‐isocenter treatment planning techniques

Prentou

Pappas

Logothetis

et al. 2020

J Applied Clin Med Phys

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Purpose In the absence of a 6D couch and/or assuming considerable intrafractional patient motion, rotational errors could affect target coverage and OAR‐sparing especially in multiple metastases VMAT‐SRS cranial cases, which often involve the concurrent irradiation of off‐axis targets. This work aims to study the dosimetric impact of rotational errors in such applications, under a comparative perspective between the single‐ and two‐isocenter treatment techniques. Methods Ten patients (36 metastases) were included in this study. Challenging cases were only considered, with several targets lying in close proximity to OARs. Two multiarc VMAT plans per patient were prepared, involving one and two isocenters, serving as the reference plans. Different degrees of angular offsets at various orientations were introduced, simulating rotational errors. Resulting dose distributions were evaluated and compared using commonly employed dose‐volume and plan quality indices. Results For single‐isocenter plans and 1⁰ rotations, plan quality indices, such as coverage, conformity index and D95%, deteriorated significantly (>5%) for distant targets from the isocenter (at> 4–6 cm). Contrarily, for two‐isocenter plans, target distances to nearest isocenter were always shorter (≤4 cm), and, consequently, 1⁰ errors were well‐tolerated. In the most extreme case considered (2⁰ around all axes) conformity index deteriorated by on‐average 7.2%/cm of distance to isocenter, if one isocenter is used, and 2.6%/cm, for plans involving two isocenters. The effect is, however, strongly associated with target volume. Regarding OARs, for single‐isocenter plans, significant increase (up to 63%) in Dmax and D0.02cc values was observed for any angle of rotation. Plans that could be considered clinically unacceptable were obtained even for the smallest angle considered, although rarer for the two‐isocenter planning approach. Conclusion Limiting the lesion‐to‐isocenter distance to ≤4 cm by introducing additional isocenter(s) appears to partly mitigate severe target underdosage, especially for smaller target sizes. If OAR‐sparing is also a concern, more stringent rotational error tolerances apply.

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“…This concept differs from other conformal techniques such as that employed in Brainlab's Multiple Metastases Element (MME) (Brainlab AG, Munich, Germany), which offers treatment of a subset of targets within a given arc. MME selects the optimal number of arcs based on the number and location of the targets but does not vary which targets are treated between control points within an arc …”

Section: Introductionmentioning

confidence: 99%

“…MME selects the optimal number of arcs based on the number and location of the targets but does not vary which targets are treated between control points within an arc. 6 This study aims to design a system that uses simulated annealing to optimize the collimation of subsets of targets at specified control points, through a process defined as intraarc binary collimation (iABC), along with control point-specific MU weighting, to achieve prescription target coverage and normal tissue sparing, where this would be normally accomplished through MLC modulation in a VMAT plan.…”

Section: Introductionmentioning

confidence: 99%

Intra‐arc binary collimation algorithm for the optimization of stereotactic radiotherapy treatment of multiple metastases with multiple prescriptions

et al. 2018

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Purpose To design and implement a novel treatment planning algorithm based on a modification of dynamic conformal arc (DCA) therapy for the treatment of multiple cranial metastases with variable prescription doses. Methods A workflow was developed in which separate dose matrices were calculated for each target at each control point (i.e., the multileaf collimator (MLC) was fit conformally to that single target). A cost function was used to quantify the relative contributions of each dose matrix in the plan to the overall plan objectives. Simulated annealing was used to allow for the inclusion or exclusion of individual dose matrices at each control point. The exclusion of individual targets at a given control point is termed intra‐arc binary collimation (iABC) in this work and is accomplished by closing the MLCs over the target for a duration specified by simulated annealing optimization. Dynamic collimator motions were employed to minimize the variation between the idealized dose matrices (i.e., perfectly collimated targets) and actual dose matrices (i.e., MLC apertures that include quantities of nontarget tissue due to the relative orientations of targets in the field). An additional simulated annealing optimization was performed to weight the relative contributions of dose at each control point [referred to as the monitor unit distribution (MUD)] to improve compliance with plan objectives. The algorithm was tested on seven previously treated multiple metastases patients and plans were compared to the clinically treated VMAT plans. Results Treatment plans generated with iABC used an average of 2716 (34%) fewer MU in the total plan than VMAT (P = 0.01). All normal tissue metrics for all plans and all patients were clinically acceptable. There were no statistically significant differences in any normal tissue dose metrics. Normalized prescription target coverage accuracy for all targets was 3% better on average for VMAT plans when compared to iABC (P = 0.07), and 14% better on average for iABC when compared to optimized DCA (P = 0.03). Conclusion A novel method of aperture and dose distribution design has been developed to significantly increase the MU efficiency of single isocenter treatment of multiple metastases with variable prescription doses when compared to VMAT, and which improves target coverage accuracy significantly when compared to optimized DCA. By applying a DCA approach to subsets of targets across control points, a hybrid method of treatment delivery has been developed that combines the efficiency of dynamic conformal treatments and the dosimetric flexibility of VMAT.

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A Systematic Analysis of 2 Monoisocentric Techniques for the Treatment of Multiple Brain Metastases

Abstract: For the planning of multiple brain lesions to be treated with stereotactic radiosurgery, Multiple Metastases Element planning software produced equivalent conformity, homogeneity, dose falloff, and brain V but required significantly lower monitor units, when compared to RapidArc plans.

Cited by 22 publications

References 19 publications

Interinstitutional Plan Quality Assessment of 2 Linac-Based, Single-Isocenter, Multiple Metastasis Radiosurgery Techniques

Interinstitutional Plan Quality Assessment of 2 Linac-Based, Single-Isocenter, Multiple Metastasis Radiosurgery Techniques

Dosimetric impact of rotational errors on the quality of VMAT‐SRS for multiple brain metastases: Comparison between single‐ and two‐isocenter treatment planning techniques

Intra‐arc binary collimation algorithm for the optimization of stereotactic radiotherapy treatment of multiple metastases with multiple prescriptions

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