Prog Med Phys.  2024 Dec;35(4):155-162. 10.14316/pmp.2024.35.4.155.

Dosimetric Comparison of Stereotactic Radiosurgery for Brain Metastases: Volumetric Modulated Arc Therapy vs. Dynamic Conformal Arc

• Kim Y
• Lim S
• Choi JH
• Park KR

• KMID: 2564154
• DOI: http://doi.org/10.14316/pmp.2024.35.4.155

Abstract

Purpose
This study aimed to compare the dose characteristics of the volumetric modulated arc therapy (VMAT) and dynamic conformal arc (DCA) techniques for metastatic brain tumor treatment using various indices to evaluate the quality of the plan and provide insights into the clinical implications of each approach.
Methods
Twelve patients with single metastatic brain tumors treated with VMAT were retrospectively analyzed. For comparison with DCA, identical geometric parameters (excluding multileaf collimators) were applied. Dose coverage, normal tissue sparing, and treatment efficiency were evaluated using indices such as CI_LIM98 , CI_ICRU , CI_RTOG , QC_RTOG , CI_SALT , HTCI_SALT , and CI_PADDIC . These indices were statistically assessed to evaluate the differences between VMAT and DCA.
Results
VMAT was superior to DCA in most indices for both small and large planning target volumes (PTVs). DCA plans for large PTVs showed a higher V_12Gy , exceeding 10 mL and failing to meet the recommended criteria (<10 mL). However, DCA required nearly half the monitor units (MUs) of VMAT, resulting in shorter treatment times. All indices, except for QC_RTOG , demonstrated significant differences between VMAT and DCA.
Conclusions
Careful consideration is necessary for larger PTVs when deciding a plan because DCA can occasionally result in V_12Gy of a brain minus PTV >10 mL. Conversely, DCA provides the advantage of shorter treatment times because of its lower MU. This study highlights the importance of using a combination of indices to comprehensively assess treatment plan quality.

Keyword

Stereotactic radiosurgery; Dynamic conformal arc; Volumetric modulated arc therapy; Conformity index; Treatment planning

Figure

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  Fig. 1 Example of the plan geometry for one of the 12 patients. For the centrally located PTV, both the VMAT and DCA plans utilized five evenly distributed arc fields optimized for uniform dose delivery. PTV, planning target volume; VMAT, volumetric modulated arc therapy; DCA, dynamic conformal arc.

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  Fig. 2 Dose–volume histogram of the brain minus PTV in the absolute volume for patient 1. The black solid line represents VMAT, and the red dotted line represents DCA. V12Gy values of the brain minus PTV are 6.00 cc for VMAT and 7.26 cc for DCA. PTV, planning target volume; VMAT, volumetric modulated arc therapy; DCA, dynamic conformal arc.

Reference

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