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Updated: Jun 27, 2026
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Stereotactic Radiosurgery for Gynecologic Cancer
Published on: April 17, 2012
Impact of Tumor Geometry on Dose Distribution and Delivery Accuracy in Multi-Target Stereotactic Radiosurgery
Hsiao-Mei Fu1,2, Tsung-Yu Yen1,2,3,4,5, Chia-Ting Lee1
1Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Beitou District, Taipei 112, Taiwan.
Brain Sciences
|June 26, 2026
Summary
Tumor geometry significantly impacts dose distribution and quality assurance in HyperArc stereotactic radiosurgery (SRS). While the Automatic Lower Dose Objective (ALDO) function improves conformity, film dosimetry offers greater sensitivity than electronic portal imaging device (EPID) portal dosimetry for small targets.
Area of Science:
- Radiation Oncology
- Medical Physics
- Radiosurgery Techniques
Background:
- Stereotactic radiosurgery (SRS) requires precise dose delivery, especially for multiple intracranial metastases.
- Tumor geometry and planning system functions like Automatic Lower Dose Objective (ALDO) can influence dosimetric outcomes.
- Accurate quality assurance (QA) is crucial for validating SRS plan delivery.
Purpose of the Study:
- To evaluate how tumor geometry affects dose distribution and delivery accuracy in SRS.
- To assess the impact of the ALDO function on dosimetric performance during SRS planning.
- To compare different QA methodologies for assessing delivery accuracy in SRS.
Main Methods:
- Simulated intracranial multiple metastases using a Rando anthropomorphic phantom with varying spherical target sizes (1 cm, 2 cm) and separations.
- Generated automated single-isocenter SRS plans using the HyperArc workflow, with and without the ALDO function.
- Evaluated dosimetric performance using conformity and gradient indices; performed patient-specific QA with electronic portal imaging device (EPID) portal dosimetry and radiochromic film dosimetry, followed by gamma analysis.
Main Results:
- ALDO improved dose conformity and gradient but increased heterogeneity and hot spots.
- EPID portal dosimetry and film measurements showed variable agreement based on target size, gamma criteria, and position.
- Larger discrepancies were noted under stricter gamma criteria and off-axis positions, influenced by target geometry and high-dose gradients.
Conclusions:
- Tumor geometric distribution significantly impacts dosimetric characteristics and QA outcomes in HyperArc SRS.
- Film measurements offer greater sensitivity compared to EPID portal dosimetry alone, particularly for small targets in high-gradient regions.
- Current QA methods may require refinement for comprehensive evaluation of complex SRS delivery scenarios.
