Comparison of Intracranial Stereotactic Radiotherapy (SRS/SRT) Plan Quality Using CyberKnife, Eclipse MLC and Cone Techniques
X Zhang*, S Jang, S Lee, A Hirsch, K Mak, M Dyer, M Truong, Boston Medical Center, Boston, MA
Presentations
PO-GePV-P-33 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: To compare intracranial SRS/SRT plan quality among CyberKnife (CK), Multi-leaf collimator (MLC), and Cone techniques.
Methods: Three groups of patients treated with CK were selected; group one (14 patients) with gross target volume (GTV) of 0.4 – 4.7 cc was re-planned with Eclipse Cone & MLC, group two (12 patients) with GTV of 0.1-1.3 cc was re-planned with Cone, and group three (12 patients) with GTV of 0.9 - 74.4 cc was re-planned with MLC. Plan quality was evaluated with Paddick’s conformity index (CI), Gradient index (GI: the ratio of isodose volume V50%/V100%) to represent the normal tissue dose. One isocenter with the coplanar beam and the same GTV dose coverage were used for plan comparison.
Results: For CK/MLC/Cone comparison in group one, three Cone-plans with GTV (>2.5cc) could not meet the GTV coverage and were eliminated from the comparison. The median CI was 1.16 (1.06-1.39), 1.18 (1.03-1.55) and 1.46 (1.06-2.9), and the median GI was 3.67 (2.68-4.38), 4.68(4.25-5.33) and 2.51(2.26-4.72), respectively. MLC-plans were not attempted for tumor volume of < 0.4 cc due to the MLC limitation. CK and MLC-plans were comparable in CI and were superior to Cone-plans. Cone-plans showed the lowest GI, and MLC-plans had the highest GI among all three techniques. Further comparison on MLC/CK and Cone/CK plans showed a good agreement with the group one results using patients with more different tumor size ranges.
Conclusion: The Cone-plans were highly affected by tumor shape and size, and showed the most inferior CI and superior GI than the other two methods. The MLC-plans had some limitations for small size targets and also received the highest normal tissue doses in low dose areas. The CK-plans did not have any tumor size restriction, and the plan quality was either comparable or in between the other two methods.
ePosters
Keywords
Treatment Techniques, Radiosurgery, Treatment Planning
Taxonomy
TH- External Beam- Photons: intracranial stereotactic/SBRT
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