Assessment of the accuracy of dose calculation in the build-up region of the tangential field of the breast for a radiotherapy treatment planning system

Aim of the study : Our objective was to quantify the accuracy of dose calculation in the build-up region of the tangential field of the breast for a TiGRT treatment planning system (TPS). Material and methods : Thermoluminescent dosimeter (TLD) chips were arranged in a RANDO phantom for the dose measurement. TiGRT TPS was also used for the dose calculation. Finally, confidence limit values were obtained to quantify the accuracy of the dose calculation of the TPS at the build-up region. Results : In the open field, for gantry angles of 15°, 30°, and 60°, the confidence limit values were 17.68, 19.97, and 34.62 at a depth of 5 mm, and 24.01, 19.07, and 15.74 at a depth of 15 mm, respectively. In the wedge field, for gantry angles of 15°, 30°, and 60°, the confidence limit values were 21.64, 26.80, and 34.87 at a depth of 5 mm, and 27.92, 22.04, and 20.03 at a depth of 15 mm, respectively. Additionally, the findings showed that at a depth of 5 mm, the confidence limit values increased with increasing gantry angle while at a depth of 15 mm, the confidence limit values decreased with increasing gantry angle. Conclusions : Overall, TiGRT TPS overestimated doses compared to TLD measurements, and the confidence limit values were greater for the wedge field than for the open fields. Our findings suggest that the assessment of dose distributions in large-dose gradient regions (i.e. build-up region) should not entirely rely on TPS calculations

Tannic acid-mediated synthesis of flower-like mesoporous MnO2 nanostructures as T1–T2 dual-modal MRI contrast agents and dual-enzyme mimetic agents

Abstract This study introduces a simple method for preparing a new generation of MnO2 nanomaterials (MNMs) using tannic acid as a template. Two shapes of MnO2 NMs, flower-like M1-MnO2 and near-spherical M2-MnO2, were prepared and compared as dual-active nanozymes and contrast agents in magnetic resonance imaging (MRI). Various parameters, including the crystallinity, morphology, magnetic saturation (Ms), surface functionality, surface area, and porosity of the MNMs were investigated. Flower-like M1-MnO2 NMs were biocompatible and exhibited pH-sensitive oxidase and peroxidase mimetic activity, more potent than near-spherical M2-MnO2. Furthermore, the signal intensity and r1 relaxivity strongly depended on the crystallinity, morphology, pore size, and specific surface area of the synthesized MNMs. Our findings suggest that flower-like M1-MnO2 NM with acceptable dual-enzyme mimetic (oxidase-like and peroxidase-like) and T1 MRI contrast activities could be employed as a promising theranostic system for future purposes