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Comprehensive Evaluation of Plan Quality Using a Single Isocenter Approach for Treatment of Multiple Brain Metastases

P Nebah1 , M Maynard1 , J Syh1 , J Dugas1 , P Dang1 , C Wang1 , H Wu1 , (1) Willis-Knighton Cancer Center, Shreveport, LA 71103


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: To evaluate plan quality of a single isocenter treatment planning method in comparison to a more conventional multiple isocenter dynamic conformal arc (MIDCA) approach. Multiple brain metastases were treated using an Elekta Agility beam limiting device (Elekta, Stockholm, Sweden) with a 5mm MLC leaf width at isocenter.

Methods: Five patients previously treated for brain metastasis using MIDCA on our Elekta Versa HD LINAC were replanned using Brainlab’s Elements Brain Mets SRS (EBMS) software (Brainlab, Munich, Germany). Patients were randomly selected with variable number of lesions (n = 2 - 6) and target volumes (0.1 – 7.17 cc). Inverse Paddick conformity (CI), Gradient index (GI), and volumes receiving 12 Gy, 6 Gy and 3 Gy were used as evaluation metrics.

Results: A high degree of conformity was achieved using EBMS (CI = 1.31 ± 0.11) compared to MIDCA (CI = 1.48 ± 0.22). Normal tissue exposure and low dose spread to the brain was higher for MIDCA, (V12 = 5.60 ± 4.58 cc, V6 = 48.12 ± 25.85 cc, and V3 = 183.76 ± 110.40 cc) compared to using EBMS, (V12 = 5.43 ± 4.39 cc, V6 = 44.85 ± 23.91 cc, and V3 = 143.98 ± 83.53 cc). Mean dose fall-off for both approaches was comparable (GI (EBMS) = 4.84 ± 0.95, GI (MIDCA)� = 4.75 ± 1.17). Treatment delivery time was notably shorter for the EBMS plans at 25 min compared to 48 min for MIDCA plans.

Conclusion: The cases studied show slightly higher conformity, improved normal tissue sparing, and more efficient treatment delivery for the automated brain metastases planning algorithm compared to the MIDCA approach.


Not Applicable / None Entered.


TH- External beam- photons: intracranial stereotactic/SBRT

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