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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-24 22:08 |
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Conference: Bucharest University Faculty of Physics 2015 Meeting
Section: Biophysics; Medical Physics
Title:
Dosimetric impact upon optic nerves due to position of the patient eyeballs in cranial 3D conformal radiotherapy
Authors:
Mihai DUMITRACHE (1,2), Alina TANASE (1,2), Mihaela DUMITRU (3), Maria VLASCEANU (1,2)
Affiliation:
1) Emergency Central Military Hospital ”Dr. Carol Davila” Bucharest, Romania
2) University of Bucharest, Faculty of Physics, Romania
3) Emergency Clinical Hospital“Sf. Ap.Andrei”, Galati, Romania
E-mail
mihai149@yahoo.com; alinatanasemail@yahoo.com
Keywords:
radiotherapy, patient contention, intra-fraction movements, optic nerves, dosimetric distribution
Abstract:
Modern radiotherapy in cranial treatments usually requires the use of thermoplastic masks for patient contention. Normally, in these cases the positioning of the patient is accurate and intra-fraction movements of the patient are quite small. However, for treatments with doses which can go over 54 Gy or reirradiation of the pretreated volumes that are localized in the immediate vicinity of the optic nerves (eye orbit) can be risen the question of optimizing the protection of these critical structure (in this case the optic nerves).
Materials and Methods: Over 30 patients entered in this study to evaluate dosimetric distribution and the probability of possible complications of the optic nerves in these cases. A number of three CT studies were performed for each case. The patients were instructed to look to the left, to the right, and in front. Based on 3D reconstruction in treatment planning we have analyzed the dosimetric impact. MV portal imaging device was used for positioning the patient for treatment.
Results: Dosimetric comparison shows that in many cases that we have studied, an important improvement of the optic nerve sparing was achieved with a variance between 15 % and 25 %. For some cases the improvement was even more important due to co-operation with the patient making the planning task more flexible.
Conclusions: The dosimetric comparison of the treatment plans based on the CT study sets for each eye position and treated case, shows that the dosimetric impact on the optic nerves is strongly dependent on the target volume delineation and the position of the eye during treatments. In these cases the study indicates that the protection of optical structure can be improved by maintaining patient gaze to the left or to the right during treatments. This approach is possible only with patient co-operation.
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