Dinamic-arc-IMRT with Serial Tomotherapy

Abstract

Intensity-modulated radiotherapy (IMRT) has been introduced into a wide spectrum of clinics worldwide. In tomotherapy, literally “slice therapy”, highly conformal treatments are possible because of an increase in the number of treatment slices into which the target is segmented would lead directly to an improvement in three-dimensional dose conformality.With Peacock System (NOMOS Corporation), the IMRT is doing so using conventional clinical linear accelerators (Linacs) fitted with an integrated multileaf collimator (MLC). This system comprised of the MIMiC, a tertiary “bolt-on” MLC, and a dedicated inverse treatment planning system (Corvus). The introduction of dynamic-arc-IMRT with Serial Tomotherapy started in the mid 1990. The first patient was treated in 1994. Between November 2007 and September 2012, at the Operative Unit of Radiotherapy of V. Fazzi Hospital of Lecce, 180 patients were treated with Serial Tomotherapy. Of those, 52 patients received Cerebral Ipofractionated Stereotactic IMRT with Talon; 66 prostate cancer patients were designed to deliver SIB-IMRT (78,4Gy to the prostate while simultaneously delivering 66,5Gy to seminal vesicles in 35 fractions); 20 patients received SIB-IMRT for Nasopharyngeal cancer (69.9Gy in 2.33Gy fractions to PTV1, 60Gy in 2Gy fractions to PTV2 and 54Gy in 1.8Gy fractions to PTV3), 28 patients received brain IMRT and 14 patients were irradiated on the spine and bone marrow for palliation or other. This slice-wise method of treatment is known to produce extremely conformal dose distributions due to its ability to specifically match the dose distribution on each slice to the shape of the target volume on that same slice. The major criticism of contemporary IMRT is that we cannot be certain of the geometry (relative position and shape) of the tumour or organs at risk (OARs) at each treatment episode. Careful and exacting protocols are employed to attempt to localize these in the treatment plan and during the patient’s set-up.