Optimization of the prescription isodose line for Gamma Knife radiosurgery using the shot within shot technique

Johnson, Perry B.; Monterroso, M; Yang, Fei; Mellon, Eric A.

doi:10.1186/s13014-017-0919-4

Cited by 10 publications

(5 citation statements)

References 13 publications

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“…3 Although multiple phase III trials have evaluated SRS in the treatment of 1 to 4 brain metastases, [4][5][6][7] there are limited data regarding the role of SRS for a larger number of metastases, 8 in part because of the prohibitively long treatment times associated with an increasing number of lesions, each requiring additional shots or separate isocenters for gamma knifeebased radiosurgery or linearaccelerator based radiosurgery, respectively. 9,10 Volumetric modulated arc therapy (VMAT) is a novel, intensity modulated radiation therapyebased plan optimization platform that permits treatment of multiple lesions using a single isocenter through modulation of gantry rotation, collimation, and dose rate. 11 Although several studies have reported the dosimetric feasibility of this technique, [12][13][14] there are little clinical data to support its safety and efficacy.…”

Section: Introductionmentioning

confidence: 99%

Single-Isocenter Multitarget Stereotactic Radiosurgery Is Safe and Effective in the Treatment of Multiple Brain Metastases

Palmer

Sebastian

Chu

et al. 2020

Advances in Radiation Oncology

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Multiple studies have reported favorable outcomes for stereotactic radiosurgery (SRS) in the treatment of limited brain metastases. An obstacle of SRS in the management of numerous metastases is the longer treatment time using traditional radiosurgery. Single-isocenter multitarget (SIMT) SRS is a novel technique that permits rapid therapy delivery to multiple metastases. There is a lack of clinical evidence regarding its efficacy and safety. We report the outcomes of patients treated with this technique. Methods and Materials: We reviewed the records of patients with intact or resected brain metastases treated with SRS in 1 to 5 fractions using SIMT technique at our institution, with at least 1 available follow-up brain magnetic resonance imaging. Survival, disease control, and toxicity were evaluated using Cox regression, logistic regression, and Kaplan-Meier analysis. Results: We identified 173 patients with 1014 brain metastases. Median follow up was 12.7 months. Median beam-on time was 4.1 minutes. The median dose to the brain was 219.4 cGy. Median overall survival and freedom from intracranial progression were 13.2 and 6.3 months, respectively. Overall survival did not differ between patients treated with greater than or less than 4 lesions (hazard ratio, 1.03; 95% confidence interval 0.66-1.61; P Z .91). Actuarial 1-and 2-year local control were 99.0% and 95.1%, respectively. Rates of grade 2 and grade 3 or higher radionecrosis were 1.4% and 0.9%, respectively.

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Section: Introductionmentioning

confidence: 99%

Single-Isocenter Multitarget Stereotactic Radiosurgery Is Safe and Effective in the Treatment of Multiple Brain Metastases

Palmer

Sebastian

Chu

et al. 2020

Advances in Radiation Oncology

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“…There is evidence that this methodoly is acceptable considering that standard GKP radiosurgery are commonly prescribed in 50% IDL [14].…”

Section: Selectivity (S)mentioning

confidence: 99%

Gamma Knife radiosurgery for vestibular schwannomas: Evaluation of planning using the sphericity degree of the target volume

et al. 2020

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Introduction This study explores the possibility of a relationship between the sphericity degree of a target volume with the dose distribution. This relationship is evaluated based on the ratio isodose volume / target volume (IV/TV) and the metrics coverage, i.e., selectivity, gradient index, conformity index and mean dose when planning radiosurgery for vestibular schwannoma. Methods Sphericity degree (φ) was calculated for each target volume (TV) of 64 patients who underwent stereotactic radiosurgery (SRS) for vestibular schwannoma. The calculation of this parameter was developed using the theoretical definition for operational sphericity φ = V P / V CS. The values found are evaluated considering the following metrics:-Coverage (C), selectivity (S), gradient index (GI), Paddick conformity index (CI Paddick) and dose distribution (IV/TV). The planning was also carried out considering a spherical target volume defined in a spherical phantom. The spherical volume is the same as the target used in the treatment plan. The planning of the spherical target was considered as a reference plan to evaluate the dose distribution inside and outside the volume. Results It was possible to observe that the majority of target volumes has (ϕ) around 0,66-0,77, corresponding to 54,7% of the total. Considering the mean values for metrics, the results are: C = 0,98, S = 0,78, GI = 3,11 and CI = 0,81. The dose distribution was equivalent for treatment plans and reference plans. Quantitative analysis for IV/TV shows that these values are higher than 30% for treatment plans where shot density is large.

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“…From Figure 5, we could observe that the gradient of the profile was highly depending on the selected IDL. Johnson et al reported for a single shot setting; the dose gradient in axial plane was the steepest at 56%–63%, 62%–70%, and 77%–84% IDL for 4‐, 8‐, and 16‐mm cones, respectively, based on their shot within shot technique 15 . Unlike other planning systems, shells currently are not allowed in this version of GammaPlan, and only GI (the dose falloff at 50% of the prescription) was incorporated in the optimization, which was distal to the target location.…”

Section: Discussionmentioning

confidence: 99%

“…Johnson et al reported for a single shot setting; the dose gradient in axial plane was the steepest at 56%–63%, 62%–70%, and 77%–84% IDL for 4‐, 8‐, and 16‐mm cones, respectively, based on their shot within shot technique. 15 Unlike other planning systems, shells currently are not allowed in this version of GammaPlan, and only GI (the dose falloff at 50% of the prescription) was incorporated in the optimization, which was distal to the target location. In the future, the effect of the gradient of profile on the plan quality should be investigated when immediate dose falloff was included as the part of optimization, for example, shell constraints.…”

Section: Discussionmentioning

confidence: 99%

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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Optimization of the prescription isodose line for Gamma Knife radiosurgery using the shot within shot technique

Cited by 10 publications

References 13 publications

Single-Isocenter Multitarget Stereotactic Radiosurgery Is Safe and Effective in the Treatment of Multiple Brain Metastases

Single-Isocenter Multitarget Stereotactic Radiosurgery Is Safe and Effective in the Treatment of Multiple Brain Metastases

Gamma Knife radiosurgery for vestibular schwannomas: Evaluation of planning using the sphericity degree of the target volume

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

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