SourceCheck detector yielded consistent results within 1% when a rotation of 180 o or positional error of up to 0.5cm was introduced in any direction. Using a PTW SourceCheck, calibrated for each plaque type using EBT3 film (or the PTW diamond detector) may offer an efficient and robust method for routinely verifying Ru-106 plaques. Purpose/Objective: Intra Operative Radiation Therapy (IORT) is a treatment modality which delivers a large single radiation dose (about 8-23Gy) during a surgery

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... edure. Accelerators specifically designed for IORT are characterized by outputs rate (about 3-12cGy/pulse) several times higher than conventional accelerators (0.1-0.6cGy/pulse). Because a very high dose values in a single fraction is delivered, a check between the planned dose and the delivered dose is mandatory by using in vivo dosimetry. Thermoluminescent dosimeters (TLDs) are widely used for in vivo dosimetry on patients during conventional radiotherapy treatment. Aim of the present study is to evaluate the potential of TLDs as in vivo dosimeters during an IORT treatment. The characterization of TLDs' response to a 6 MV low dose-perpulse photon beam from a conventional clinic linear accelerator as well as to a 9 MeV high dose-per-pulse electron beams from an IORT device, in the range 0-10Gy, was carried out. Materials and Methods: The TLDs used were LiF:Mg,Ti (TLD-100, Harshaw Chemical Company) chips. TLDs were irradiated with a 6MV photon beam in an equivalent water phantom in reference conditions (100 cm from the source, depth of 5 cm, beam size of 10x10 cm 2 ). The readout of TLDs was performed by a Harshaw model 3500 manual TLD reader, at 300 °C using a heating rate of 10 °C/s. After being processed, TLDs were irradiated with a 9 MeV IORT electron beam at the deep of the maximum dose (13 mm). The distance between the source and the upper surface of the phantom was of 100 cm and the field diameter was 10 cm. With both energies, the TLDs were divided into five groups of eight TLDs and irradiated from 2 to 10 Gy in step of 2 Gy. For all the beams a linear and a quadratic regression was performed between TLD response and doses delivered. The goodness of the fit was evaluated by the R 2 coefficient. The better performance of the two models was assessed by F test. Results: The TLDs' response at a 6MV photon beam and 9MeV electron beam was reported in Figure 1a -1b. The results show very close R 2 values for the linear and the quadratic models ( Table 1 ). The F test approved the linear model as the better model (p=0,169) for the photon beam, while it approved the quadratic model (p<0.0004) for the electron beam.