Heterogeneities existing in the patient during treatment are neglected, as the treated subject is considered homogeneous in most of the commercially‐available treatment planning systems (TPSs) used for high dose rate (HDR) brachytherapy. The choice of a suitable dosimeter for experimental dosimetry near the HDR source is crucial, mainly due to existence of steep dose gradients. The present work aimed to assess the effect of rectal air heterogeneity and applicator attenuation in the HDR Ir‐192 brachytherapy treatment of carcinoma uterine cervix by utilizing GAFCHROMIC EBT2 film dosimetry. The dose to rectal walls under the condition of rectal air heterogeneity was measured experimentally using EBT2 film in a rectal phantom, and the measurements were validated by the Monte Carlo (MC) simulations. The applicator attenuation was measured by EBT2 film for a commonly used stainless steel uterine tube in a homogeneous water equivalent phantom. The measured doses were compared with the TPS calculated values. In case of the air cavity, the measured dose at the closest rectal surface was 12.8% less than the TPS calculated value due to lack of back scattering, whereas at the farthest rectal surface, it was higher by 24.5% due to no attenuation. The magnitude of attenuation due to the metal applicator was measured as high as 2% when compared with the TPS calculation. The dose reduction at the nearest rectal surface due to the effect of rectal air has indicated a clinically favorable dose distribution within the rectum, whereas the shielding effect posed by the metallic applicator was found to be less significant. Mutual agreement of the measured doses with the MC calculated dose values confirmed the suitability of EBT2 film for clinical dosimetry in HDR brachytherapy.PACS numbers: 87.53.Bn, 87.53.Jw, 87.56.bg, 87.55.Qr

No abstract

No abstract

1−x)BaTiO 3 -xPZT(65/35) ceramics were prepared by high temperature solid state reaction technique. Structural properties of the compounds were examined using an X-ray diffraction (XRD) technique to confirm the formation of phase at room temperature. Detailed studies of dielectric properties of (1−x) BaTiO 3 -xPZT(65/35) for all compositions were in temperature range 30-200 o C reveal that the compound have transition temperature well above at the room temperature. While pure BaTiO 3 ceramics exhibited a sharp phase transformation expected for normal ferroelectrics, phase transformation behavior of the (1−x) BaTiO 3 -xPZT(65/35) solid solutions became more diffuse with increasing PZT(65/35) contents.The diffusivity of the dielectric peaks in the compound exhibited the values between 1 and 2 where the higher value indicates the greater disorder in the systems. This was primarily evidenced by an increased broadness in the dielectric peak, with a maximum peak width occurring at x = 0.5. The temperature dependence of ac conductivity indicated that the electrical conductivity decrease above T C on increasing the PZT(65/35) contents. This increase in the conductivity is attributed to the increase in polarizability of the materials around T c, due to oxygen vacancies.

No abstract