Clinical Evaluation of Shot-Within-Shot Optimization for Gamma Knife Radiosurgery Planning and Delivery

Johnson, Perry B.; Monterroso, M; Yang, Fei; Bossart, Elizabeth; Keyvanloo, Amir; Mellon, Eric A.

doi:10.1016/j.wneu.2018.11.140

Cited by 4 publications

(9 citation statements)

References 12 publications

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“…1,14,15 Indeed, prior studies by Johnson et al and Wright et al have utilized delivery time as a metric for plan optimization. 9,17 As observed with prior studies, delivery times were protracted significantly as plans moved toward smaller collimators due to geometric effect as well as the loss of output factor.…”

Section: D | Delivery Time Efficiencysupporting

confidence: 59%

“…The clinical utility of GK can be limited by the protracted delivery times compared with the dose rates observed with other treatment modalities such as flattening filter‐free linear accelerators and/or CyberKnife 1,14,15 . Indeed, prior studies by Johnson et al and Wright et al have utilized delivery time as a metric for plan optimization 9,17 . As observed with prior studies, delivery times were protracted significantly as plans moved toward smaller collimators due to geometric effect as well as the loss of output factor.…”

Section: Discussionmentioning

confidence: 98%

“…Simultaneously, an appropriate isodose line was selected to scale the absolute dose to the target. Prior studies have shown the efficacy of this method of pairing shot weighting with IDL to generate the same absolute dose to the prescription IDL 9,10 …”

Section: Methodsmentioning

confidence: 99%

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Associating dose–volume characteristics with theoretical radiobiological metrics for rapid Gamma Knife stereotactic radiosurgery plan evaluation

Tien

Bond

Chen

2020

J Applied Clin Med Phys

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Purpose To examine general dose–volume characteristics in Gamma Knife (GK) plans which may be associated with higher tumor control probability (TCP) and equivalent uniform dose (EUD) using characteristic curve sets. Methods Two sets of dose–volume histograms (DVHs) were exported alongside an analytical purpose‐generated DVH: (a) single‐shot large collimator (8 or 16 mm) emulated with multiple shots of 4 mm collimator. (b) shot‐within‐shot (SWS) technique with isodose lines (IDLs) of 40–75%. TCP, average dose, EUD in single‐fraction (EUD T ) and 2 Gy fractionated regimens (EUD R ) were examined for trends with cumulative DVH (cDVH) shape as calculated using a linear‐quadratic cell survival model (α/β = 10.0 Gy, N 0 = 1 × 10 6 ) with both α = 0.20 Gy −1 and α = 0.23 Gy −1 . Results Using α = 0.20 Gy −1 (α = 0.23 Gy −1 ), plans in the analytical set with higher shoulder regions had TCP, EUD T , EUD R increased by 180%, 5.9%, 10.7% (11.2%, 6.3%, 10.0%), respectively. With α = 0.20 Gy −1 (α = 0.23 Gy −1 ), plans with higher heels had TCP, EUD T , EUD R increased by 4.0%, <1%, <1% (0.6%, <1%, <1%), respectively. In emulating a 16 (8) mm collimator, 64 (12) shots of the small collimators were used. Plans based on small collimators had higher shoulder regions and, with α = 0.20 Gy −1 (α = 0.23 Gy −1 ), TCP, EUD T , EUD R was increased up to 351.4%, 5.0%, 8.8% (270.4%, 5.0%, 6.8%) compared with the single‐shot large collimator. Delivery times ranged from 10.2 to 130.3 min. The SWS technique used 16:8 mm collimator weightings ranging from 1:2 to 9.2:1 for 40–75% IDL. With α = 0.20 Gy −1 (α = 0.23 Gy −1 ), the 40% IDL plan had the highest shoulder with increased TCP, EUD T , EUD R by 130.7%, 9.6%, 17.1% (12.9%, 9.1%, 16.4%) over the 75% IDL plan. Delivery times ranged 6.9–13.8 min. Conclusions The magnitude of the shoulder region characteristic to GK cDVHs may be used to rapidly identify superior plan among candidates. Practical issues such as delivery time may require further consideration.

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Section: D | Delivery Time Efficiencysupporting

confidence: 59%

Section: Discussionmentioning

confidence: 98%

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Associating dose–volume characteristics with theoretical radiobiological metrics for rapid Gamma Knife stereotactic radiosurgery plan evaluation

Tien

Bond

Chen

2020

J Applied Clin Med Phys

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“…A full description of the methods used to create the optimization tables included in this work can be found in Johnson et al [2] . The implementation of the technique is described further in Johnson et al [1] . In short, profiles were extracted from Leksell Gamma Plan v.10 for each of the three collimator settings available on the GK Perfexion (4, 8, and 16 mm).…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

“…Clinical evaluation of shot within shot optimization for Gamma Knife radiosurgery planning and delivery. World Neurosurgery (in press) [1] …”

mentioning

confidence: 99%

Data for optimizing Gamma Knife radiosurgery using the shot within shot technique

et al. 2019

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The tables included in this article will allow the user to implement shot within shot optimization for Gamma Knife radiosurgery planning and delivery. The method is intended to reduce treatment time when treating small to medium sized brain metastasis. The tables were previously developed by extracting profiles from Gamma Plan for three collimator settings and modeling their behavior when combined or prescribed at different isodose lines. For a given target size, the tables represent the optimal selection of shot weighting and prescription isodose line to reduce beam on time while maintaining an acceptable dose gradient. The method was recently validated in a large patient cohort and the data is this study is related to the research article titled “Clinical evaluation of shot within shot optimization for Gamma Knife radiosurgery planning and delivery” (Johnson et al., in press).

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Evaluating the impact of prescription isodose line on plan quality using Gamma Knife inverse planning

Kubicek²,

Mulvihill³

et al. 2021

J Applied Clin Med Phys

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The impact of selection of prescription isodose line (IDL) on plan quality has not been well evaluated during inverse planning (IP). In this study, a total of 180 IP plans at five levels of IDL were generated for 30 brain metastases (BMs). For each BM, one round of IP was performed with typical IP settings, followed by a quick fine‐tuning to ensure the same target coverage and comparable conformality index. The impact of the IDL on the quality metrics (selectivity, gradient index [GI], and treatment time) was evaluated. The decrease of selectivity and increase of GI meant inferior target dose conformality and more dose spillage. Additionally, a metric directly correlated to the treatment time was proposed. For all cases, the mean GI decreased monotonically as IDL decreased from 70% to 30%, and the decreasing rate was significantly different based on tumor size. The mean selectivity and number of shots decreased monotonically as IDL decreased for all the tumors. From 70% to 30% IDL, the decreasing rate of the mean selectivity was 2.8% (p = 0.020), 7.7% (p = 0.005), and 15.4% (p = 0.020) and that of the number of shots was 75.4% (p = 0.001), 73.2% (p = 0.001), and 50.7% (p = 0.009), for the large, medium, and small tumors, respectively. For the medium and small tumor groups, the mean treatment time increased monotonically when IDLs decreased (increasing rate was 80.0% [p = 0.002] for medium tumors [p = 0.001] and 130.8% [p = 0.001] for small tumors from 70% to 30%). For the large tumors, the mean treatment time was the shortest at 50% IDL (59.0 min) and higher at 70% (65.9 min) and 30% (71.9 min). Overall, the GammaPlan chose smaller sectors for plans with lower IDLs except for the large size group.

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Clinical Evaluation of Shot-Within-Shot Optimization for Gamma Knife Radiosurgery Planning and Delivery

Cited by 4 publications

References 12 publications

Associating dose–volume characteristics with theoretical radiobiological metrics for rapid Gamma Knife stereotactic radiosurgery plan evaluation

Associating dose–volume characteristics with theoretical radiobiological metrics for rapid Gamma Knife stereotactic radiosurgery plan evaluation

Data for optimizing Gamma Knife radiosurgery using the shot within shot technique

Evaluating the impact of prescription isodose line on plan quality using Gamma Knife inverse planning

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