J Korean Neurosurg Soc.  2013 Feb;53(2):102-107. 10.3340/jkns.2013.53.2.102.

Clinical Application of Gamma Knife Dose Verification Method in Multiple Brain Tumors : Modified Variable Ellipsoid Modeling Technique

• Hur BI
• Lee JM
• Cho WH
• Kang DW
• Kim CR
• Choi BK

• KMID: 2190686
• DOI: http://doi.org/10.3340/jkns.2013.53.2.102

Abstract

OBJECTIVE
The Leksell Gamma Knife(R) (LGK) is based on a single-fraction high dose treatment strategy. Therefore, independent verification of the Leksell GammaPlan(R) (LGP) is important for ensuring patient safety and minimizing the risk of treatment errors. Although several verification techniques have been previously developed and reported, no method has ever been tested statistically on multiple LGK target treatments. The purpose of this study was to perform and to evaluate the accuracy of a verification method (modified variable ellipsoid modeling technique, MVEMT) for multiple target treatments.
METHODS
A total of 500 locations in 10 consecutive patients with multiple brain tumor targets were included in this study. We compared the data from an LGP planning system and MVEMT in terms of dose at random points, maximal dose points, and target volumes. All data was analyzed by t-test and the Bland-Altman plot, which are statistical methods used to compare two different measurement techniques.
RESULTS
No statistical difference in dose at the 500 random points was observed between LGP and MVEMT. Differences in maximal dose ranged from -2.4% to 6.1%. An average distance of 1.6 mm between the maximal dose points was observed when comparing the two methods.
CONCLUSION
Statistical analyses demonstrated that MVEMT was in excellent agreement with LGP when planning for radiosurgery involving multiple target treatments. MVEMT is a useful, independent tool for planning multiple target treatment that provides statistically identical data to that produced by LGP. Findings from the present study indicate that MVEMT can be used as a reference dose verification system for multiple tumors.

Keyword

Brain tumor; Gamma Knife; Radiation dose; Radiosurgery

MeSH Terms

Brain
Brain Neoplasms
Humans
Patient Safety
Radiosurgery

Figure

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  Fig. 1 Bland-Altman Plots for each individual case. The middle line represents the mean difference between the LGP and MVEMT. The two extreme lines are the +1.96 and -1.96 standard deviations of the difference between the two methods. MVEMT : modified variable ellipsoid modeling technique, LGP : Leksell GammaPlan.

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  Fig. 2 A : Bland-Altman Plot for all pooled data (n=500). The mean difference between doses calculated by two methods, LGP and MVEMT (95% CI) was -0.057. B : Bland-Altman Plot for data excluding case 6 (n=450). The mean difference between doses calculated by two methods (95% CI) was -0.140. The middle line is the mean difference between LGP and MVEMT. The two extreme lines are the +1.96 and -1.96 standard deviations of the difference between two methods. MVEMT : modified variable ellipsoid modeling technique, LGP : Leksell GammaPlan.

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