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Session: Stereotactic Radiosurgery [Return to Session]

Dosimetric Impact of Lesion Size and Number On Mean Brain Dose with Stereotactic Radiosurgery for Brain Metastases

D Wieczorek1,2, R Tolakanahalli1,2, Y Lee1, M Hall1,2, M Tom1,2, M Mehta1,2, M Mcdermott2,3, A Gutierrez1,2*, R Kotecha1,2,(1) Miami Cancer Institute, Miami, FL, (2) Herbert Wertheim College of Medicine, Florida International University, Miami, FL (3) Miami Neuroscience Institute, Miami, FL


MO-C930-IePD-F7-3 (Monday, 7/11/2022) 9:30 AM - 10:00 AM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 7

Purpose: When treating numerous lesions with stereotactic radiosurgery(SRS) in the modern era , the impact of increasing the volume of intracranial disease (via lesion volume and/or number of lesions) on normal brain dose remains understudied. The objective of this study is to evaluate the effect of number and size of lesions treated with SRS using Gamma Knife on mean brain dose.

Methods: Three sets of gross tumor volumes (GTVs), grouped by lesion size (Group1 [<5mm], Group2 [5-10mm], and Group3 [>10-16mm]), were contoured. SRS plans were generated and lesions were all prescribed 20 Gy in 1 fraction. For each group of lesions, plans were generated using the Lightning optimizer in the Gamma Plan treatment planning system. Plans for each group started with a nominal number of lesions which were progressively increased until a threshold mean brain dose was reached. The brain volume receiving 8, 10 and 12 Gy (V8Gy, V10Gy and V12Gy), mean brain dose, total GTV volume, and total number of lesions were recorded for each plan.

Results: Across all simulated plans, the mean brain dose was linearly proportional(correlation coefficient: 0.99) to the number of lesions and the total GTV volume. Maximum number of lesions needed to reach the threshold mean brain dose of 8 Gy were 177, 57 and 29 for Groups 1, 2 and 3, respectively; corresponding total GTV volumes were 3.13cc, 20.45cc, and 31.1cc, respectively. V8Gy, V10Gy, and V12Gy had a quadratic correlation to the number of lesions and the total GTV volume.

Conclusion: Mean brain dose was found to increase linearly with number of lesions and total GTV volume while select metrics such as V8Gy, V10Gy, and V12Gy showed a quadratic correlation to the number of lesions and the total GTV volume.


Brain, Gamma Knife, Radiosurgery


TH- External Beam- Photons: intracranial stereotactic/SBRT

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