Abstract
Evaluation of the dose distribution delivered in a radiosurgery treatment of an acoustic neuroma using an adapted Alderson phantom and radiochromic film to assess absolute dose. A system was developed to perform the dose measurements, using the Alderson Rando phantom´s head carrying a modified slice, where a material reproducing the tumor was inserted. The phantom’s head with the modified slice was irradiated in a medical linear accelerator, using a procedure similar to that adopted in real cases, and radiochromic films were used to assess dose values. The suitability of the dose distribution delivered in the treatment was evaluated by comparing the Dose Volume Histograms, obtained from the Treatment Planning System (TPS) and by radiochromic film measurements. An agreement around 3% between experimental data and TPS´s calculations, showing an acceptable concordance with the planning results. The established approach of transforming 2D arrays of dose in a 3D one is satisfactory, validating it. The developed method shows to be an excellent alternative to quality control in radiosurgery using the radiochromic film to assess absolute dose.
Highlights
Acoustic neuroma or Vestibular schwannoma arises from Schwann cells of the vestibulocochlear nerve
The statistical evaluation of the dose was obtained from the Dose Volume Histogram (DVH) generated by Treatment Planning System (TPS) (Figure 5), allowing to obtain the maximum dose and the percent volume of irradiated planned target volume (PTV), supporting the choice of a proper planning
The DVH shows that 94% of the PTV volume received 94% of the prescribed dose, and the maximum dose of 4.04 Gy was delivered to 1% of total volume
Summary
Acoustic neuroma or Vestibular schwannoma arises from Schwann cells of the vestibulocochlear nerve (cranial nerve VIII). Most vestibular schwannoma have an intracanalicular component, with widening of the porus acousticus, which is present in 90% of cases. As these tumours enlarge, extracanalicular extension occurs. The diagnosis of vestibular schwannoma is made radiographically using contrast enhanced magnetic resonance imaging (MRI). Management options for newly diagnosed vestibular schwannoma include observation, surgery or radiation [1]. Tsao et al (2017) provided a summary on the published literature pertaining to acoustic neuroma management. A total of 405 articles were identified through Medline [1]
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