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SU‐F‐T‐612: Investigation of Acoustic Neuroma Planning for Stereotactic Radiosurgery Utilizing Linac‐Based Cone Collimators
Author(s) -
Yeboah C,
Ruschin M,
Lee Y,
Sarfehnia A,
Chugh B,
Myrehaug S,
Tsao M,
Soliman H,
Sahgal A
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4956797
Subject(s) - radiosurgery , nuclear medicine , acoustic neuroma , medicine , linear particle accelerator , stereotactic radiotherapy , dosimetry , radiation treatment planning , beam (structure) , physics , radiation therapy , radiology , optics , surgery
Purpose: To assess the feasibility of designing clinically‐acceptable stereotactic radiosurgery (SRS) plans utilizing linac‐based cone collimators for patients presenting with acoustic neuroma. Methods: Five acoustic neuroma patients with gross tumour volumes (GTVs) of sizes from 1.3 to 2.7 cc were studied. The cranial‐caudal extent of the GTVs range from 1.1 to 1.7 cm whereas the largest cross‐sectional extent of the lesions varied from 2.0 to 2.4 cm. No PTV margin was added. The relevant organs‐at‐risk (OARs) were the brainstem, brain, lens, eyes and cochlea. The SRS planning system, ERGO (Elekta), was used to design treatment plans with non‐coplanar arcs delivered using various stereotactic cone sizes on an Elekta Synergy unit. The prescription dose was 12 Gy to be delivered in a single fraction. The final dose distribution for each target was achieved with two to five isocenters, each consisting of up to five non‐coplanar arcs. Results: The achieved GTV V12, V11.4, and V11 were 97.6–98.6%, 99.2– 99.8% and 99.6–100%, respectively. The penalty for using multiple isocenters for a single target was a relatively high maximum dose of up to 18 Gy, which equals 150% of the prescription dose. In all cases, the RTOG and Paddick conformity indices fell within the range 1.45–1.70 and 0.57–0.66, respectively. Point maximum dose to the brainstem varied from 12.4 to 14 Gy and its V12 was ≤0.12cc. The point maximum doses to the lens and eyes were ≤80 and ≤110cGy, respectively, and total body V10 was ≤6.2cc. Point maximum dose to ipsilateral cochlea was similar to the prescription dose. Conclusion: Clinically‐acceptable and deliverable dose distributions for acoustic neuroma cases can be achieved with linac‐based stereotactic cones system. Up to five isocenters per target are required for GTVs of sizes ≤3cc. The treatment plans meet RTOG protocol requirement on conformity index.