Dynamic conformal arcs-based single-isocenter VMAT planning technique for radiosurgery of multiple brain metastases

Pokhrel, Damodar; Palmiero, Allison N; Bernard, Mark; Clair, William St

doi:10.1016/j.meddos.2020.11.005

Cited by 4 publications

(5 citation statements)

References 28 publications

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“…[ 14 ] In addition, the collimator angles were chosen so that the two targets did not share a leaf pair from the MLC [ Table 1 and Figure 3 ]. [ 12 ]…”

Section: Ethodsmentioning

confidence: 99%

“…To achieve a steep dose gradient and high dose concentration,[ 15 ] the photon optimizer algorithm was used with a structure resolution of 1.25 mm and the following parameters: Maximum dose (Upper) to the PTV,[ 14 ] unrestricted; minimum dose (Lower) to the PTV, 20 Gy (priority = 200); normal tissue objective distance from target border, 0.1 cm; starting dose, 100%; end dose, 30%; fall-off factor, 0.45 (priority = 250). Furthermore, the optimization process used the jaw tracking technique,[ 12 ] which dynamically correlates the MLC aperture with the jaws during irradiation to reduce the size of low-dose regions by minimizing the leakage and transmission of the MLC leaves. [ 16 ]…”

Section: Ethodsmentioning

confidence: 99%

“…A flattening filter-free (FFF) beam is commonly utilized in SIMT SRS VMAT as it can provide shorter irradiation time and steeper dose gradients than a flattening filter beam,[ 5 , 7 , 8 , 10 ] resulting in a smaller radiation dose to healthy brain tissue. [ 10 ] However, in SIMT SRS VMAT planning, targets as small as approximately 1 cm in diameter can be offset from the isocenter by more than 6 cm,[ 11 , 12 ] which may complicate the multi-leaf collimator (MLC) motion and increase the monitor unit (MU) level and thus lead to reduced irradiation accuracy. [ 13 ] Ohira et al .…”

Section: Introductionmentioning

confidence: 99%

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Overcoming Problems Caused by Offset Distance of Multiple Targets in Single-isocenter Volumetric Modulated Arc Therapy Planning for Stereotactic Radiosurgery

Ito,

Kubo,

Monzen

et al. 2023

Journal of Medical Physics

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Purpose: The purpose of the study is to investigate the impact of large target offset distances on the dose distribution and gamma passing rate (GPR) in single-isocenter multiple-target stereotactic radiosurgery (SIMT SRS) using volumetric modulated arc therapy (VMAT) with a flattening filter-free (FFF) beam from a linear accelerator. Methods: Two targets with a diameter of 1 cm were offset by ”±2, ±4, and ±6 cm from the isocenter in a verification phantom for head SRS (20 Gy/fr). The VMAT plans were created using collimator angles that ensured the two targets did not share a leaf pair from the multi-leaf collimator. To evaluate the low-dose spread intermediate dose spill (R50%), GPRs were measured with a criterion of 3%/2 mm using an electronic portal imaging device and evaluated using monitor unit (MU), modulation complexity score for VMAT (MCSv), and leaf travel (LT) parameters. Results: For offsets of 2, 4, and 6 cm, the respective parameters were: R50%, 4.75 ± 0.36, 5.13 ± 0.36, and 5.11 ± 0.33; GPR, 95.01%, 93.82%, and 90.67%; MU, 5893 ± 186, 5825 ± 286, and 5810 ± 396; MCSv, 0.24, 0.16, and 0.13; and LT, 189.21 ± 36.04, 327.69 ± 67.01, and 430.39 ± 114.34 mm. There was a spread in the low-dose region from offsets of ≥4 cm and the GPR negatively correlated with LT (r = −0.762). There was minimal correlation between GPR and MU or MCSv. Conclusions: In SIMT SRS VMAT plans with an FFF beam from a linear accelerator, target offsets of <4 cm from the isocenter can minimize the volume of the low-dose region receiving 10 Gy or more. During treatment planning, it is important to choose gantry, couch, and collimator angles that minimize LT and thereby improve the GPR.

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“…[ 14 ] In addition, the collimator angles were chosen so that the two targets did not share a leaf pair from the MLC [ Table 1 and Figure 3 ]. [ 12 ]…”

Section: Ethodsmentioning

confidence: 99%

Section: Ethodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Overcoming Problems Caused by Offset Distance of Multiple Targets in Single-isocenter Volumetric Modulated Arc Therapy Planning for Stereotactic Radiosurgery

Ito,

Kubo,

Monzen

et al. 2023

Journal of Medical Physics

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show abstract

“…However, conventional SRS requires extensive planning efforts and patient setup for individual isocenters, with separate planning for each lesion. Recently, the volumetric modulated arc therapy (VMAT) technique has emerged as a solution for treating multiple brain lesions using a single isocenter with single or multiple arcs [2,9,16,17]. In 2017, the HyperArc VMAT (HA-VMAT, Varian Medical Systems, Palo Alto, CA, USA) plan was clinically implemented as a new solution to supplement SRS dose delivery demands [5,18].…”

Section: Introductionmentioning

confidence: 99%

“…Treatment precision and geometric accuracy are vital when managing patients with multiple BMs [16,19,21]. SRS demands a high degree of positioning accuracy, a steeper dose gradient, and meticulous dose verification [11].…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Efficacy of Machine Performance Checks as an Alternative to Winston–Lutz Quality Assurance Testing in the TrueBeam Linear Accelerator with HyperArc

Kim,

Park

et al. 2024

Diagnostics

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HyperArc is a preferred technique for treating brain metastases, employing a single isocenter for multiple lesions. Geometrical isocentricity in the TrueBeam linear accelerator with HyperArc is crucial. We evaluated machine performance checks (MPCs) as an alternative to the Winston–Lutz (WL) test to verify the treatment isocenter. Between January and July 2023, we assessed 53 data points using MPC and Winston–Lutz tests. The isocenter size obtained from the MPC and its sum, including the rotation-induced couch shift, were compared with the maximum total delta value from the Winston–Lutz test. The maximum total delta was 0.68 ± 0.10 mm, while the isocenter size was 0.28 ± 0.02 mm. The sum of the isocenter size and rotation-induced couch shift measured by MPC was 0.61 ± 0.03 mm. During the Winston–Lutz test (without couch rotation), the maximum total delta value was 0.56 ± 0.13 mm. A t-test analysis revealed a significant difference in the isocenter size averages between the Winston–Lutz and MPC outcomes, whereas the Pearson’s correlation coefficient yielded no correlation. Our study highlights the necessity for separate MPC and Winston–Lutz tests for isocenter verification. Therefore, the Winston–Lutz test should precede stereotactic radiosurgery for isocenter verification.

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The spatial accuracy of ring-mounted halcyon linac versus C-arm TrueBeam linac for single-isocenter/multi-target SBRT treatment

2023

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Dynamic conformal arcs-based single-isocenter VMAT planning technique for radiosurgery of multiple brain metastases

Cited by 4 publications

References 28 publications

Overcoming Problems Caused by Offset Distance of Multiple Targets in Single-isocenter Volumetric Modulated Arc Therapy Planning for Stereotactic Radiosurgery

Overcoming Problems Caused by Offset Distance of Multiple Targets in Single-isocenter Volumetric Modulated Arc Therapy Planning for Stereotactic Radiosurgery

Evaluating the Efficacy of Machine Performance Checks as an Alternative to Winston–Lutz Quality Assurance Testing in the TrueBeam Linear Accelerator with HyperArc

The spatial accuracy of ring-mounted halcyon linac versus C-arm TrueBeam linac for single-isocenter/multi-target SBRT treatment

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