Magnetic mesoporous silica nanoparticles as a theranostic approach for breast cancer: Loading and release of the poorly soluble drug exemestane.

Exemestane has a limited aqueous solubility that leads to a very high variability in absorption when administrated orally. It is crucial to develop strategies to increase the solubility and bioavailability of this drug. To overcome these issues, the aim of the present work was the development of magnetic silica mesoporous nanoparticles (IOMSNs) to carry and release exemestane. Furthermore, these nanoparticles could be also used as Magnetic Resonance Imaging (MRI) contrast agents for treatment monitorization and tumor detection. MRI analysis showed that IOMSNs present a concentration dependent contrast effect, revealing their potential for MRI applications. Also, IOMSNs present a very good polydispersity (0.224) and nanometric range size (137.2 nm). It was confirmed that the nucleus is composed by magnetite and the silica coating presents tubes with MCM-41-like hexagonal structure. Both iron oxide nanoparticles and iron oxide mesoporous silica nanoparticles were not toxic in cell culture for 24 h. Exemestane was successful released for 72 h following a typical sustained release pattern, achieving a very high loading capacity (37.7%) and in vitro release of 98.8%. Taking into account the results it is possible to conclude that IOMSNs have a high potential to be used as theranostic for intravenous breast cancer treatment with exemestane.

Characterization of Extrafocal Dose Influence on the Out-of-Field Dose Distribution by Monte Carlo Simulations and Dose Measurements.

Out-of-field scattered and transmitted extrafocal radiation may induce secondary cancer in long-term survivors of external radiotherapy. Pediatric patients have higher life expectancy and tend to receive higher secondary radiation damage due to geometric and biological factors. The goal of this study is to characterize the location and the magnitude of extrafocal dose regions in the case of three-dimensional conformal radiotherapy and volumetric arc therapy, to apply this information to clinical treatment cases, and to provide mitigation strategies. Extrafocal dose has been investigated in a Varian TrueBeam linac equipped with a high-definition 120 multileaf collimator using different physical and virtual phantoms, dose calculation (including Monte Carlo techniques), and dose measurement methods. All Monte Carlo calculations showed excellent agreement with measurements. Treatment planning system calculations failed to provide reliable results out of the treatment field. Both Monte Carlo calculations and dose measurements showed regions with higher dose (extrafocal dose areas) when compared to the background. These areas start to be noticeable beyond 11 cm from the isocenter in the direction perpendicular to the multileaf collimator leaves' travel direction. Out-of-field extrafocal doses up to 160% of the mean dose transmitted through the closed multileaf collimator were registered. Two overlapping components were observed in the extrafocal distribution: the first is an almost elliptical blurred dose distribution, and the second is a well-defined rectangular dose distribution. Extra precautions should be taken into consideration when treating pediatric patients with a high-definition 120 multileaf collimator to avoid directing the extrafocal radiation into a radiosensitive organ during external beam therapy.

Optimization of skin dose using in-vivo MOSFET dose measurements in bolus/non-bolus fraction ratio: A VMAT and a 3DCRT study.

In-phantom and in-vivo three dimensional conformal radiation therapy (3DCRT) and volumetric modulated arc therapy (VMAT) skin doses, measured with and without bolus in a female anthropomorphic phantom RANDO and in patients, were compared against treatment planning system calculated values. A thorough characterization of the metal oxide semiconductor field effect transistor measurement system was performed prior to the measurements in phantoms and patients. Patients with clinical indication for postoperative external radiotherapy were selected. Skin dose showed higher values with 3DCRT technique compared with VMAT. The increase in skin dose due to the use of bolus was quantified. It was observed that, in the case of VMAT, the bolus effect on the skin dose was considerable when compared with 3DCRT. From the point of view of treatment time, bolus cost, and positioning reproducibility, the use of bolus in these situations can be optimized.

The use of needle holders in CTF guided biopsies as a dose reduction tool.

PURPOSE: The purpose of this study was to evaluate the efficacy of needle holders in reducing staff hand exposure during biopsies guided by computed tomography fluoroscopy (CTF), through the analysis of data acquired during a detailed monitoring study, undertaken in parallel with an ongoing optimization process to reduce hand irradiation. METHODS: Hand monitoring was performed with 11 extremity detectors, two per finger (base and tip) and one on the back of the wrist, for the left (dominant) hand, during two series of biopsies with comparable characteristics. The first series (47 biopsies) were performed with only quick-check method (QC) and occasional side-handle (SH) manipulation of the needle. The second series (63 biopsies) were performed after introducing needle holders (NH) in the course of an optimization process. RESULTS: Choice of technique (QC, QC + NH, QC + SH) by the interventional radiologist (IR) was related to biopsy difficulty. Measured hand exposure was low (< 1 mSv) for all QC-only procedures, and for most of the QC + NH procedures. Occasional side-handle manipulation still occurred during challenging biopsies, so that 8% of biopsies in the second series accounted for ~70% of total fingertip dose (~90 mSv). The methodology used allowed a detailed insight into the dose reduction achievable with needle holders during real procedures, without the limitations of phantom measurements. CONCLUSIONS: Needle holders proved effective in reducing mean hand exposure during clinical procedures where real-time manipulation was necessary. Occasional side-handle manipulation was found to contribute disproportionately to hand exposure. This highlights the importance of individual hand monitoring during CTF guided procedures.

Gafchromic XR-QA2 film as a complementary dosimeter for hand-monitoring in CTF-guided biopsies.

Computed tomography fluoroscopy (CTF) is a useful imaging technique to guide biopsies, particularly lung biopsies, but it also has the potential for very high hand exposures, despite use of quick-check method and needle holders whenever feasible. Therefore, reliable monitoring is crucial to ensure the safe use of CTF. This is a challenge, because ring dosimeters monitor exposure only at the base of one finger, while the fingertips may be exposed to the highly collimated CT beam. In this work we have explored the possibility of using Gafchromic XR-QA2 self-developing film as a complementary dosimeter to quantify hand exposure during CTF-guided biopsies. A glove used in a previous study and designed to contain 11 TLDs was adapted to include Gafchromic strips 7 mm wide, covering the fingers. A total of 22 biopsies were successfully performed wearing this GafTLD glove under sterile gloves, and the IR reported no difficulty or reduction of dexterity while wearing it. Comparison of dose distributions obtained from digitization of the Gafchromic film strips and absolute Hp(0.07) readings from TLDs showed good agreement, despite some positional uncertainty due to relative movement. Per procedure, doses at the base of the ring finger can be as low as 3%-8% of hand dose maximum. Accumulated dose at the base of the ring finger was four times lower than the dose maximum.

Characterization of geometric uncertainties of a dose calibrator during measurement of 90Y activity.

UNLABELLED: The performance and measurement of (90)Y with a dose calibrator has always been a key point of several international recommendations, specifically in the case of the radiopharmaceutical (90)Y-ibritumomab tiuxetan, among other applications, used in the treatment of non-Hodgkin lymphoma. The objective of the present work was to examine in detail some important sources of geometric errors that, if neglected, can lead to an increase in uncertainty about the measured activity of this ß(-) emitter radionuclide. METHODS: A CRC-15R dose calibrator was used to measure and quantify some of these sources, although the same methodology can easily be applied to any other similar equipment. The depth response along the main axis of the dose calibrator was carefully characterized, as well as syringe volume effects and source angular dependence. RESULTS: It was found that, if not taken properly into account, these issues can contribute to an increase in the activity uncertainty (e.g., 5.1% in the present example). This finding implies the possibility of easily reaching higher values than the internationally suggested 5% uncertainty in activity measurement for therapeutic purposes. CONCLUSION: These errors can be greatly reduced by previous characterization of the dose calibrator and careful implementation of the methodology for measurement.