Simultaneous radiosurgery for multiple brain metastases: technical overview of the UCLA experience

Agazaryan, Nzhde; Tenn, Stephen; Lee, Chul; Steinberg, Michael L.; Hegde, John V.; Chin, Robert; Pouratian, Nader; Yang, Isaac; Kim, Won; Kaprealian, Tania

doi:10.1186/s13014-021-01944-w

Cited by 17 publications

(14 citation statements)

References 19 publications

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“…According to our findings, a 1 mm margin of GTV to PTV is appropriate when the isocenter is located in the center of a target. This is in agreement with the data presented by Agazaryan 20 and Nakan et al.o 21 To achieve targeting accuracy, a greater GTV to PTV margin is required when planning multiple targets and using a single isocenter. In our current practice, we perform MV imaging at every couch angle and limit the residual setup error to 0.5 mm and 1 degree.…”

Section: Discussionsupporting

confidence: 91%

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Li,

Mail,

Stefania diMayorca

et al. 2023

J Applied Clin Med Phys

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Purpose/objectives(A) To examine the alignment accuracy of CBCT guidance for brain metastases with off centered isocenters, (B) to test dose delivery and targeting accuracy for single isocenter treatments with multiple brain metastases. We report the results of the end‐to‐end test for Truebeam stereotactic radiosurgery (SRS).Materials/methodsAn anthropomorphic CT head phantom was drilled with five MOSFET inserts and two PTW Pinpoint chamber inserts. The phantom was simulated, planned, and delivered. For the purpose of comparing the accuracy of alignment, CBCTs were acquired with the isocenter centered and offset superiorly 8 cm, inferiorly 8 cm, anteriorly 7 cm, posteriorly 7 cm, and right 5 cm. There were six degrees of freedom corrections applied to the plans, as well as intentional rotational and translational errors for dose comparisons. Dose accuracy checks were performed with MOSFET and PTW Pinpoint chamber, and targeting accuracy was assessed with GafChromic films.Result(A) Compared to centered CBCT, off‐centered CBCT scan showed some alignment errors, with a maximum difference of 0.6‐degree pitch and 0.9 mm translation when the phantom was placed 8 cm inferior off center. (B) For the single isocenter plan, measured doses of the five MOSFET were 95%–100% of the planned dose, whereas the multiple isocenter plans were 96%–100%. With intentional setup errors of 1‐degree pitch, doses were 97.1%–100.4% compared to the perfect setup. The same was found for the two pinpoint chamber readings with 1‐degree rotation and 1 mm translation. (C) Targeting accuracy for targets at the isocenter is 0.67 mm, within the machine specification of 0.75 mm. Targeting accuracy for isocenters 6–12 cm away from the target is in the range 0.67–1.18 mm.Conclusion(A) Single isocenter HyperArc treatments for multiple brain metastases are feasible and targeting accuracy is clinically acceptable. (B) The vertex in a cranial scan is very important for proper alignment.

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Section: Discussionsupporting

confidence: 91%

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Li,

Mail,

Stefania diMayorca

et al. 2023

J Applied Clin Med Phys

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“…Based on this model, we selected ten patients with multiple brain metastasis targets treated with the single isocenter for multiple targets (SIMT) technique to test the impact of the isocenter selection method in clinical setting.The translation margin was set to 2 mm and rotational uncertainties were set to 1.0 • . [18][19][20][21] The number of brain metastases in each plan ranges from two to six. The separation distance ranges from 28.5 to 135.5 mm.…”

Section: Discussionmentioning

confidence: 99%

Optimization of isocenter position for multiple targets with nonuniform‐margin expansion

Miao

Dai

2022

J Applied Clin Med Phys

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The single isocenter for multiple-target (SIMT) technique has become a popular treatment technique for multiple brain metastases. We have implemented a method to obtain a nonuniform margin for SIMT technique. In this study, we further propose a method to determine the isocenter position so that the total expanded margin volume is minimal. Materials and method:Based on a statistical model, the relationship between nonuniform margin and the distance d (from isocenter to target point), setup uncertainties, and significance level was established. Due to the existence of rotational error, there is a nonlinear relationship between the margin volume and the isocenter position. Using numerical simulation, we study the relationship between optimal isocenter position and translational error, rotational error, and target size. In order to find the optimal isocenter position quickly, adaptive simulated annealing (ASA) algorithm was used. This method was implemented in the Pinnacle 3 treatment planning system and compared with isocenter at center-ofgeometric (COG), center-of -volume (COV), and center-of -surface (COS). Ten patients with multiple brain metastasis targets treated with the SIMT technique was selected for evaluation. Results: When the size of tumors is equal, the optimal isocenter obtained by ASA and numerical simulation coincides with COG, COV, and COS. When the size of tumors is different, the optimal isocenter is close to the large tumor. The position of COS point is closer to the optimal point than the COV point for nearly all cases.Moreover,in some cases the COS point can be approximately selected as the optimal point. The ASA algorithm can reduce the calculating time from several hours to tens of seconds for three or more tumors. Using multiple brain metastases targets, a series of volume difference and calculating time were obtained for various tumor number, tumor size, and separation distances. Compared with the margin volume with isocenter at COG, the margin volume for optimal point can be reduced by up to 27.7%. Conclusion: Optimal treatment isocenter selection of multiple targets with large differences could reduce the total margin volume. ASA algorithm can significantly improve the speed of finding the optimal isocenter. This method can be used for clinical isocenter selection and is useful for the protection of normal tissue nearby.

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“…In our study GTV-to-PTV margin was 1 mm. Using small GTV-to-PTV margins is an essential strategy to reduce the risk of toxicity, since larger margins led to a significant increase of V 12Gy [ 20 , 29 ]. Certainly, the use of 1-mm margins requires robust protocols for quality assurance for all steps of SRS treatment, including the use of contrast-enhanced 3D fast gradient echo T1-weighted sequences with slice thickness of 0.5–1 mm for target delineation, correction of geometric distortion in MR images, and accurate registration of CT and MRI data sets.…”

Section: Discussionmentioning

confidence: 99%

Single-isocenter multiple-target stereotactic radiosurgery for multiple brain metastases: dosimetric evaluation of two automated treatment planning systems

et al. 2022

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Purpose Automated treatment planning systems are available for linear accelerator (linac)-based single-isocenter multi-target (SIMT) stereotactic radiosurgery (SRS) of brain metastases. In this study, we compared plan quality between Brainlab Elements Multiple Brain Metastases (Elements MBM) software which utilizes dynamic conformal arc therapy (DCAT) and Varian HyperArc (HA) software using a volumetric modulated arc therapy (VMAT) technique. Patients and methods Between July 2018 and April 2021, 36 consecutive patients ≥ 18 years old with 367 metastases who received SIMT SRS at UPMC Hillman Cancer San Pietro Hospital, Rome, were retrospectively evaluated. SRS plans were created using the commercial software Elements MBM SRS (Version 1.5 and 2.0). Median cumulative gross tumor volume (GTV) and planning tumor volume (PTV) were 1.33 cm3 and 3.42 cm3, respectively. All patients were replanned using HA automated software. Extracted dosimetric parameters included mean dose (Dmean) to the healthy brain, volumes of the healthy brain receiving more than 5, 8,10, and 12 Gy (V5Gy, V8Gy, V10Gy and V12Gy), and doses to hippocampi. Results Both techniques resulted in high-quality treatment plans, although Element MBM DCAT plans performed significantly better than HA VMAT plans, especially in cases of more than 10 lesions). Median V12Gy was 13.6 (range, 1.87–45.9) cm3 for DCAT plans and 18.5 (2.2–62,3) cm3 for VMAT plans (p < 0.0001), respectively. Similarly, V10Gy, V8Gy, V5Gy (p < 0.0001) and median dose to the normal brain (p = 0.0001) were favorable for DCAT plans. Conclusions Both Elements MBM and HA systems were able to generate high-quality plans in patients with up to 25 brain metastases. DCAT plans performed better in terms of normal brain sparing, especially in patients with more than ten lesions and limited total tumor volume.

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Simultaneous radiosurgery for multiple brain metastases: technical overview of the UCLA experience

Cited by 17 publications

References 19 publications

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Single isocenter HyperArc treatment of multiple intracranial metastases: Targeting accuracy

Optimization of isocenter position for multiple targets with nonuniform‐margin expansion

Single-isocenter multiple-target stereotactic radiosurgery for multiple brain metastases: dosimetric evaluation of two automated treatment planning systems

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