Evaluation of helical tomotherapy in the treatment of high-grade gliomas near critical structures

Background. Our purpose was to investigate the role of helical tomotherapy using a simultaneous integrated boost technique for the treatment of high-grade gliomas near intracranial critical structures. Methods and materials. Of 27 patients treated with helical tomotherapy, 11 were eligible. Only patients whose tumors were within 0.5 cm of the optic chiasm, the optic nerve or the brainstem were included. The therapeutic approach was a simultaneous integrated boost, prescribing 66 and 60 Gy to the PTV1 and PTV2, respectively, in 30 fractions. All patients received concomitant temozolomide at a dose of 75 mg/m2 daily during radiation therapy. Results. Of the 11 patients considered, 3 patients (27%) died after 4 months from the completion of the combined treatment. Three patients (27%) presented local progression, and the median time to disease progression was 6 months (range, 1-12). Five patients (45%), at the time of this evaluation, did not have signs or symptoms of recurrence or progression of the disease. Acute toxicity, evaluated during radiochemotherapy, was minimal, with all patients experiencing RTOG grade 0 and grade 1 toxicity. Conclusions. Helical tomotherapy proved to be an effective and safe treatment modality, with an improvement of accuracy in delivery of highdose radiotherapy despite the presence of nearby critical structures. © Il Pensiero Scientifico Editore

Monte Carlo Calculation and Experimental Verification of the Photon Energy Response of Tooth Enamel in a Head-Sized Plexiglas Phantom.

The use of electron paramagnetic resonance (EPR) tooth dosimetry for calculation of organ doses requires conversion of the measured absorbed dose in enamel. Before deriving conversion factors from simulation calculations with a realistic anthropomorphic human phantom, in the current study a simplified phantom was chosen to compare EPR measurement and Monte Carlo calculation. The dose response of tooth enamel of molars at various positions inside a cylindrical Plexiglas phantom of head-size was calculated by Monte Carlo modelling in parallel photon beams of X rays of 63 keV equivalent energy and Co-60 gamma rays (1.25 Mev). For X ray exposure, preliminary results of EPR dosimetry with tooth enamel samples prepared front molars irradiated in the phantom were in agreement with calculation. The mean value of the ratio of the measured to the calculated dose was 0.93 +/- 0.08