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. 2013 Jul;38(3):120-4.
doi: 10.4103/0971-6203.116364.

Comparative analysis between 5 mm and 7.5 mm collimators in CyberKnife radiosurgery for trigeminal neuralgia

H Sudahar  1 , P G G Kurup, V Murali, J Velmurugan
Affiliations

Comparative analysis between 5 mm and 7.5 mm collimators in CyberKnife radiosurgery for trigeminal neuralgia

H Sudahar et al. J Med Phys. 2013 Jul.

Abstract

Trigeminal neuralgia (TN) is treated in CyberKnife (Accuray Inc, Sunnyvale, USA) with the 5 mm collimator whose dosimetric inaccuracy is higher than the other available collimators. The 7.5 mm collimator which is having less dosimetric uncertainty can be an alternative for 5 mm collimator provided the dose distribution with 7.5 mm collimator is acceptable. Aim of this study is to analyze the role of 7.5 mm collimator in CyberKnife treatment plans of TN. The treatment plans with 5 mm collimators were re-optimized with 7.5 mm collimator and a bi-collimator system (5 mm and 7.5 mm). The treatment plans were compared for target coverage, brainstem doses, and the dose to normal tissues. The target and brainstem doses were comparable. However, the conformity indices were 2.31 ± 0.52, 2.40 ± 0.87 and 2.82 ± 0.51 for 5 mm, bi-collimator (5mm and 7.5 mm), 7.5 mm collimator plans respectively. This shows the level of dose spillage in 7.5 mm collimator plans. The 6 Gy dose volumes in 7.5 mm plans were 1.53 and 1.34 times higher than the 5 mm plan and the bi-collimator plans respectively. The treatment time parameters were lesser for 7.5 mm collimators. Since, the normal tissue dose is pretty high in 7.5 mm collimator plans, the use of it in TN plans can be ruled out though the treatment time is lesser for these 7.5 mm collimator plans.

Keywords: Collimators; CyberKnife; stereotactic radiosurgery; trigeminal neuralgia.

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Conflict of interest statement

Conflict of Interest: None declared.

Figures

Figure 1
Figure 1
An axial dose distribution comparison between 5 mm collimator plan (a), 5-7.5 mm bi-collimator plan (b), and 7.5 mm collimator plan (c)
Figure 2
Figure 2
The graph between the volume dose index and the corresponding target doses in all the collimator plans
Figure 3
Figure 3
The graph between the brainstem volume dose index and the corresponding brainstem doses all the three collimator plans
Figure 4
Figure 4
Comparison of the normal tissue doses in terms of dose volume indices
Figure 5
Figure 5
Comparison of the number of nodes and beams between the three collimator plans
Figure 6
Figure 6
The MU spread in all the three collimator plans for all the 11 cases taken in the present study
See this image and copyright information in PMC

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