Multifunction bismuth-based nanoparticles with the ability to display diagnostic and therapeutic functions have drawn extensive attention as theranostic agents in radiation therapy and imaging due to their high atomic number, low toxicity, and low cost. Herein, we tried to introduce multifunction bismuth gadolinium oxide nanoparticles (BiGdO3) as a new theranostic agent for radiation therapy, computed tomography (CT) and magnetic resonance imaging (MRI). After synthesis of BiGdO3 nanoparticles and surface modifications of them with PEG, biocompatibility of the nanoparticles was evaluated by a CCK-8 assay. We investigated dose amplification properties of the nanoparticles using gel dosimetry and in vitro and in vivo assays. According to clonogenic assay radiation, a sensitizer enhancement ratio (SER) of 1.75 and 1.66 (100 µg ml−1-nanoparticles), for MCF-7 and 4T1 cell lines at low energy x-ray was achieved, respectively. Radiation dose enhancement effect of the nanoparticles was proven for high concentrations (500 µg ml−1) by gel dosimetry. For further investigation, in vivo cancer radiotherapy was carried out using female BALB/c mice with 4T1 breast tumors. In vivo results emphasized the radiosensitizing effect of BiGdO3-PEG nanoparticles. Both bismuth and gadolinium provide CT contrast, while gadolinium can be employed for MRI T1 contrast, so we evaluated contrast enhancement of BiGdO3-PEG nanoparticles as a dual-modal imaging agent in MR and CT imaging. Collectively, our experimental results clearly display properties of BiGdO3-PEG nanoparticles as multimodal imaging and radiosensitizing agents. The results show that the nanoparticles deserve further study as a new theranostic agent.

Recently bismuth-based nanoparticles have drawn extensive attention as radiosensitizer in radiotherapy due to high atomic number, low toxicity, and low cost. This study aims to introduce the applicability of bismuth ferrite nanoparticles (BFO, BiFeO3) as a new multifunctional theranostic agent for radiotherapy, magnetic resonance imaging (MRI), and computed tomography (CT) as well as magnetic hyperthermia mediator. After evaluation of BFO nanoparticles biocompatibility which were synthesized by conventional sol-gel method, we investigated dose enhancement property of BFO nanoparticles with gel dosimetry, clonogenic, and cck8 assay. According to clonogenic assay, sensitizer enhancement ratios (SERs) were obtained as 1.35 and 1.76 for nanoparticle concentrations of 0.05 mg/ml and 0.1 mg/ml, respectively. For high concentration (0.5 mg/ml), dose enhancement effect of BFO nanoparticles was demonstrated by gel dosimetry. To prove the contrast enhancement of BFO nanoparticles in MR and CT imaging, the relaxation time rate (R2) and Hounsfield unit (HU) were measured, respectively. It was found that the R2 and Hu have linear relationship with the nanoparticle concentrations. Moreover, whereas BFO nanoparticles have magnetic properties, we measured inductive heating property of the nanoparticles in external alternative magnetic field to evaluate their applicability as magnetic hyperthermia mediator. A rapid temperature increment was detected under alternative magnetic field (12.2 kAm-1 and 17.2 kAm-1, frequency 480 kHz) owing to the high concentration of BFO nanoparticles. Collectively, our experimental investigation results proved that the multifunctional BFO nanoparticles could be employed as a multimodal imaging and radio-thermotherapeutic agent to enhance theranostic efficacy.

Recently bismuth-based nanoparticles as a promising radiosensitizer have drawn great attention in radiation therapy. To prove physical dose enhancement effect of the nanoparticles, gel dosimeters can be considered as an ideal method. This study aims to prove the applicability of bismuth ferrite nanoparticles as a magnetic localized dose enhancement agent by gel dosimetry method. Bismuth ferrite nanoparticle was synthesized by the conventional sol-gel method. Then we investigated dose enhancement property of the nanoparticles with gel dosimetry. MAGIC Polymer Gel dosimeters with nanoparticles were prepared and irradiated. According to gel dosimetry assay, for 0.5 mg/ml concentration of bismuth ferrite nanoparticles dose enhancement factor were obtained as 2 and 1.6 at 160 keV and average energy of 380 keV, respectively. Moreover, radiosensitiser effect of bismuth ferrite nanoparticles in presence of a low dose rate brachytherapy source (125-I) was investigated by Monte Carlo method. Whereas bismuth ferrite nanoparticles have magnetic property, we made a biodegradable spacer (fiducial) brachytherapy loaded with the nanoparticles for delivering nanoparticles and drug by applying an external magnetic field.

Special collimators used in imaging systems play an important part in obtaining qualified images to improve diagnosis in medicine. Methods: The primary aim of this study was to compare resolution between fan beam and parallel beam collimators using Monte Carlo simulation in the shape of cubic holes. Also, parameters such as geometric efficiency, geometric resolution, scatter, penetration, and full width at half maximum were studied to compare their special characteristics. Results: The simulation results demonstrated that the geometry efficiency of a fan beam collimator increased as the angle of the slant hole increased, and the geometric resolution decreased as the angle of the slant hole increased, at a distinct distance from a monoenergetic source of g-rays. In contrast, at a distinct angle, geometric resolution increased as the distance between the source and the collimator surface increased. For both collimators, scatter and penetration decreased as the distance increased. These results were in agreement with ADAC company data. Finally, fan beam collimators were found to have better resolution than parallel beam collimators with a cubic hole shape in a wire mesh design. Conclusion: Estimation of the fan beam by parallel beam parameters as cubic holes can be suitable in collimator design to improve resolution and efficiency. Col limation of low-energy photons, allowing detection of only those photons propagating in the appropriate direction, plays a key role in obtaining a suitable map in SPECT imaging. Some collimators, such as the parallel beam and fan beam types, are widely used in different applications and for organs centered within the field of view. Therefore, it is important to study collimator geometric properties to improve diagnosis in medicine. Fan beam collimators are a special type of converging collimator with the holes focusing toward a focal line parallel to the axis of rotation of the camera (1).For optimization of collimator design, photon interactions in g-camera collimators have been simulated by the Monte Carlo N-particle code (MCNP5) (2-4). In this code, source geometry, collimators, and detectors need to be defined in the input file-a cumbersome process (5,6). Recently, researchers have clinically compared parallel beam and fan beam collimators and simulated the parallel beam collimator by this code (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). In this study, fan beam parameters were deliberated by this code.To improve resolution and efficiency, it is helpful to model collimators of various hole shapes, edge effects, septal materials, and geometric configurations. The aim of this study was to investigate resolution between fan beam and parallel beam collimators using MCNP5 simulation in the shape of cubic holes. Also, distinctive parameters such as geometric efficiency, scatter, penetration, and full width at half maximum (FWHM) have been compared, with assessment of the fan beam and parallel beam collimator responses. MATERIALS AND METHODS Computation of Cubic Hole A...

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