Synthesis of methotrexate-loaded tantalum pentoxide-poly(acrylic acid) nanoparticles for controlled drug release applications.

Over the past decade, there has been increasing interest in the use of multifunctional nanoparticles (NPs) for cancer treatment. Of importance are systems that can deliver drugs at a sustained rate to target cancer cells, which can result in higher efficiency and reduced systemic toxicity. In this study, we present the route for the synthesis of tantalum pentoxide (Ta2O5) NPs with a particle size of 27 nm that were individually coated with poly(acrylic acid) (PAA) with a different layer thickness of 2-8 nm by in-situ polymerization of the acrylic acid monomer. The capability of Ta2O5-PAA to provide anatomical contrast-enhancing features has been demonstrated via computed tomography. The Ta2O5-PAA conjugate was further loaded with methotrexate, and the drug release was observed for a total of 72 h at a pH of 3.6, 5.4, 7.4, and 9.4. While the different layer thicknesses did not influence the drug release kinetics, a decrease in pH of the release medium resulted in a slower drug release. The developed nanocomposite particles present a great potential as a theranostic system for biomedical applications.

Influence of exposure and geometric parameters on absorbed doses associated with common neuro-interventional procedures.

PURPOSE: The purpose of this study was to investigate the effects of routine exposure parameters on patient's dose during neuro-interventional radiology procedures. METHODS: We scrutinized the routine radiological exposure parameters during 58 clinical neuro-interventional procedures such as, exposure direction, magnification, frame rate, and distance between image receptor to patient's body and evaluate their effects on patient's dose using an anthropomorphic phantom. Radiation dose received by the occipital region, ears and eyes of the phantom were measured using MOSkin detectors. RESULTS: DSA imaging technique is a major contributor to patient's dose (80.9%) even though they are used sparingly (5.3% of total frame number). The occipital region of the brain received high dose largely from the frontal tube constantly placed under couch (73.7% of the total KAP). When rotating the frontal tube away from under the couch, the radiation dose to the occipital reduced by 40%. The use of magnification modes could increase radiation dose by 94%. Changing the image receptor to the phantom surface distance from 10 to 40cm doubled the radiation dose received by the patient's skin at the occipital region. CONCLUSION: Our findings provided important insights into the contribution of selected fluoroscopic exposure parameters and their impact on patient's dose during neuro-interventional radiology procedures. This study showed that the DSA imaging technique contributed to the highest patient's dose and judicial use of exposure parameters might assist interventional radiologists in effective skin and eye lens dose reduction for patients undergoing neuro-interventional procedures.

A comparison of entrance skin dose delivered by clinical angiographic c-arms using the real-time dosimeter: the MOSkin.

Coronary angiography is a procedure used in the diagnosis and intervention of coronary heart disease. The procedure is often considered one of the highest dose diagnostic procedures in clinical use. Despite this, there is minimal use of dosimeters within angiographic catheterisation laboratories due to challenges resulting from their implementation. The aim of this study was to compare entrance dose delivery across locally commissioned c-arms to assess the need for real-time dosimetry solutions during angiographic procedures. The secondary aim of this study was to establish a calibration method for the MOSkin dosimeter that accurately produces entrance dose values from the clinically sampled beam qualities and energies. The MOSkin is a real-time dosimeter used to measure the skin dose delivered by external radiation beams. The suitability of the MOSkin for measurements in the angiographic catheterisation laboratory was assessed. Measurements were performed using a 30 × 30 × 30 cm(3) PMMA phantom positioned at the rotational isocenter of the c-arm gantry. The MOSkin calibration factor was established through comparison of the MOSkin response to EBT2 film response. Irradiation of the dosimeters was performed using several clinical beam qualities ranging in energy from 70 to 105 kVp. A total of four different interventional c-arm machines were surveyed and compared using the MOSkin dosimeter. The phantom was irradiated from a normal angle of incidence using clinically relevant protocols, field sizes and source to image detector distance values. The MOSkin was observed to be radiotranslucent to the c-arm beam in all clinical environments. The MOSkin response was reproducible to within 2 % of the average value across repeated measurements for each beam setting. There were large variations in entrance dose delivery to the phantom between the different c-arm machines with the highest observed cine-acquisition entrance dose rate measuring 326 % higher than the lowest measured cine-acquisition entrance dose rate and with the highest measured fluoroscopic entrance dose rate measuring 346 % higher than the lowest measured fluoroscopic entrance dose rate. This comparison of entrance dose delivery across local clinical c-arms demonstrated the disparity in entrance dose delivery across catheterisation laboratories and outlined a need for real-time dose monitoring systems for patients during angiographic procedures. Through use of our calibration method, an average MOSkin calibration of 7.37 mV/cGy was established. The calibration method allowed entrance dose to be measured across a range of beam energies and beam qualities without the input of the c-arm beam characteristics. This calibration factor was proven to reproduce entrance dose values to within 5 % value of the reference dosimeter's response, suggesting potential for further studies and utilisation of the dosimeter in this field.