Output factor measurement in high dose-per-pulse IORT electron beams.

PURPOSE: To assess the capability of different types of detectors to measure relative output factors (OF) at high dose per pulse by comparison with alanine dosimeters, which are independent of dose rate. METHODS: Measurements were made in 9 MeV and 7 MeV electron beams produced by a Novac7 accelerator for intraoperative radiotherapy. Applicators with diameter of 10-7-6-5 and 4 cm were used. The dose per pulse varied from about 30 mGy, for the 10 cm reference applicator, to about 70 mGy, for the 4 cm applicator. Five types of plane-parallel ionization chambers (PTW Advanced Markus, Markus and Roos, IBA PPC40 and PPC05), two types of silicon diodes (PTW 60017 and IBA EFD3G) and a PTW 60019 microDiamond were considered. For the ionization chambers, correction factors for ion recombination effects were determined for each applicator using a modified two-voltage-analysis method that includes the free-electron component. RESULTS: Reference OF values were determined by alanine dosimeters with a standard combined uncertainty of 0.8%. Deviations from the reference OFs were generally within 1.5% for all the detectors, hence within the 95% confidence interval of alanine measurements. Larger deviations of up to about 2% obtained in a few cases are consistent with a 0.7% long-term reproducibility of OF measurements. CONCLUSIONS: Comparison with alanine measurements demonstrated that all the detectors considered in this work can be used to measure OFs in high dose-per-pulse electron beams with an accuracy better than 2%, provided that appropriate corrections for ion recombination effects are applied when using ionization chambers.

A new method to evaluate the influence of the glenosphere positioning on stability and range of motion of a reverse shoulder prosthesis.

PURPOSE: Shoulder instability and reduced range of motion are two common complications of a total reverse shoulder arthroplasty. In this work, a new approach is proposed to estimate how the glenoid component positioning can influence the stability and the range of motion of a reverse shoulder prosthesis. MATERIALS AND METHODS: A standard reverse shoulder prosthesis has been analysed. To perform virtual simulation of the shoulder-prosthesis assembly, all the components of the prosthesis have been acquired via a 3D laser scanner and the solid models of the shoulder bones have been reconstructed through CT images. Loads on the shoulder joint have been estimated using anatomical models database. A new virtual/numerical procedure has been implemented using a 3D parametric modelling software to find the optimal position of the glenosphere. RESULTS: Several analyses have been performed using different configurations obtained by changing the glenoid component tilt and the lateral position of the glenosphere, modified through the insertion of a cylindrical spacer. For the analysed case study, it was found that the interposition of a spacer (between the baseplate and the glenoid) and 15° inferior tilt of the glenosphere allow improving the range of motion and the stability of the shoulder. CONCLUSIONS: Some common complications of the reverse shoulder arthroplasty could be effectively reduced by a suitable positioning of the prosthesis components. In this work, using a new method based on virtual simulations, the influence of the glenosphere positioning has been investigated. An optimal configuration for the analysed case study has been found. The proposed approach could be used to find, with no in vivo experiments, the optimal position of a reverse shoulder prosthesis depending on the different dimensions and shape of the bones of each patient.

Graphite particles induce ROS formation in cell free systems and human cells.

It is commonly accepted that the toxicity of carbonaceous particulate matter (PM) is due to the production of reactive oxygen species (ROS) which induce biological damage in the exposed cells. It is also known that PM produced during the combustion processes consists of a carbonaceous core "dressed" with other organic and/or inorganic materials. In spite of this knowledge, the role of these materials in the production of ROS has not yet been clear. This work aims at understanding whether "naked" carbonaceous particles are capable of forming ROS either in cell-free or in-cell systems. The problem has been treated based on the data collected from pure graphite samples of different sizes obtained by ball-milling pure graphite for various lengths of time. The experimental approach considered Raman, ESR (spin trapping), cell viability and fluorescence spectroscopy measurements. These techniques allowed us to carry out measurements both in cell and cell-free systems and the results consistently indicate that also pure naked carbonaceous particles can catalyze the electron transfer that produces superoxide ions. The process depends on the particle size and enlightens the role of the edges of the graphitic platelets. Evidence has been collected that even "naked" graphitic nanoparticles are capable of producing ROS and decreasing the cell viability thus representing a potential danger to human health.

Photon correlation spectroscopy applied to tear analysis.

This study aims to deepen the knowledge on tear film properties by the development of a protocol for analyses of Photon Correlation Spectroscopy (PCS) on human tears and by the comparison between PCS results obtained on tears of contact lens wearers and non-wearers. Tears (5µL) were collected by a glass capillary. The analyses provide the hydrodynamic diameter of tear components by analyzing intensity fluctuations in time of scattered light. PCS appears a promising technique for studying tear features and for shedding light on specific eye conditions, such as on the clinical effects of CL wear. In fact, statistical difference (p<0.001) was found between the measured mean hydrodynamic diameter of tear components of wearers and non-wearers, the resulting value significantly higher for CL wearers. The scenario does not substantially change after (25±5)min from the CL removal. The difference is attributed to changes in the interactions between tear constituents due to CL wear. In order to get deeper insights on the influence of CL wear on aggregation and structure of tear components, a preliminary Electron Spin Resonance (ESR) investigation was performed, monitoring Fe3+ species. ESR spectra on tears of both CL wearers and non-wearers showed the presence of intense signals, probably associated to iron (III) centers in proteins such as lactoferrin, and a weaker resonance attributable to Fe3+ species interacting with S-S bridges of lysozyme. Differences in ESR spectra between CL wearers and non-wearers were detected and tentatively ascribed to changes in coordination or in local environment of Fe3+ centers connected to aggregation phenomena induced by CL wear, which promote their interaction with other neighboring iron species.

Quantitative 177Lu SPECT imaging using advanced correction algorithms in non-reference geometry.

Peptide receptor therapy with 177Lu-labelled somatostatin analogues is a promising tool in the management of patients with inoperable or metastasized neuroendocrine tumours. The aim of this work was to perform accurate activity quantification of 177Lu in complex anthropomorphic geometry using advanced correction algorithms. Acquisitions were performed on the higher 177Lu photopeak (208keV) using a Philips IRIX gamma camera provided with medium-energy collimators. System calibration was performed using a 16mL Jaszczak sphere surrounded by non-radioactive water. Attenuation correction was performed using µ-maps derived from CT data, while scatter and septal penetration corrections were performed using the transmission-dependent convolution-subtraction method. SPECT acquisitions were finally corrected for dead time and partial volume effects. Image analysis was performed using the commercial QSPECT software. The quantitative SPECT approach was validated on an anthropomorphic phantom provided with a home-made insert simulating a hepatic lesion. Quantitative accuracy was studied using three tumour-to-background activity concentration ratios (6:1, 9:1, 14:1). For all acquisitions, the recovered total activity was within 12% of the calibrated activity both in the background region and in the tumour. Using a 6:1 tumour-to-background ratio the recovered total activity was within 2% in the tumour and within 5% in the background. Partial volume effects, if not properly accounted for, can lead to significant activity underestimations in clinical conditions. In conclusion, accurate activity quantification of 177Lu can be obtained if activity measurements are performed with equipment traceable to primary standards, advanced correction algorithms are used and acquisitions are performed at the 208keV photopeak using medium-energy collimators.

Gamma camera calibration and validation for quantitative SPECT imaging with (177)Lu.

Over the last years (177)Lu has received considerable attention from the clinical nuclear medicine community thanks to its wide range of applications in molecular radiotherapy, especially in peptide-receptor radionuclide therapy (PRRT). In addition to short-range beta particles, (177)Lu emits low energy gamma radiation of 113keV and 208keV that allows gamma camera quantitative imaging. Despite quantitative cancer imaging in molecular radiotherapy having been proven to be a key instrument for the assessment of therapeutic response, at present no general clinically accepted quantitative imaging protocol exists and absolute quantification studies are usually based on individual initiatives. The aim of this work was to develop and evaluate an approach to gamma camera calibration for absolute quantification in tomographic imaging with (177)Lu. We assessed the gamma camera calibration factors for a Philips IRIX and Philips AXIS gamma camera system using various reference geometries, both in air and in water. Images were corrected for the major effects that contribute to image degradation, i.e. attenuation, scatter and dead- time. We validated our method in non-reference geometry using an anthropomorphic torso phantom provided with the liver cavity uniformly filled with (177)LuCl3. Our results showed that calibration factors depend on the particular reference condition. In general, acquisitions performed with the IRIX gamma camera provided good results at 208keV, with agreement within 5% for all geometries. The use of a Jaszczak 16mL hollow sphere in water provided calibration factors capable of recovering the activity in anthropomorphic geometry within 1% for the 208keV peak, for both gamma cameras. The point source provided the poorest results, most likely because scatter and attenuation correction are not incorporated in the calibration factor. However, for both gamma cameras all geometries provided calibration factors capable of recovering the activity in anthropomorphic geometry within about 10% (range -11.6% to +7.3%) for acquisitions at the 208keV photopeak. As a general rule, scatter and attenuation play a much larger role at 113keV compared to 208keV and are likely to hinder an accurate absolute quantification. Acquisitions of only the (177)Lu main photopeak (208keV) are therefore recommended in clinical practice. Preliminary results suggest that the gamma camera calibration factor can be assessed with a standard uncertainty below (or of the order of) 3% if activity is determined with equipment traceable to primary standards, accurate volume measurements are made, and an appropriate chemical carrier is used to allow a homogeneous and stable solution to be used during the measurements.

A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams.

The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm(-2), and at a dose rate of about 0.15 Gy min(-1), results of calorimetric measurements of absorbed dose to water, D(w), were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D(w) and D(wK) were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D(w) uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D(w), it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams.

Results of closed subtalar dislocations.

BACKGROUND: The subtalar dislocation (SD) of the foot is an uncommon injury characterized by a simultaneous dislocation of talocalcaneal and talonavicular joints without involvement of the tibiotalar and calcaneocuboid joints. PURPOSES: The purpose of this study was to evaluate the clinical and radiological outcome in a consecutive series of close SD. METHODS: We retrospectively evaluated a case series of patients who presented a close SD. Thirteen patients were selected for this study. There were 9 patients with a medial SD, 3 patients with a lateral dislocation and 1 patient with a posterior subtalar dislocation. RESULTS: The most frequent symptoms observed in our study included transient mild pain, swelling and decreased ankle ROM, which did not restrict patients' daily activities. However, lower AOFAS scores were observed on patients with associate peritalar osseous injuries. CONCLUSION: The results of the present study suggest that detecting and treating any associate peritalar fractures are the keys to a successful long-term outcome.

Comments to the paper "do we really need new medical information about the Turin Shroud?".

Following the interesting arguments raised in a recent letter to the editor, about a paper recently published in this journal, the authors are happy to take a cue from them to clarify some facts that have not been sufficiently treated for space. After a description of the methods used, arguments regarding a blunt trauma on the right shoulder with consequent dislocation, the position of the hands on the pubis with brachial plexus injury, and the wrist nailing that caused retracted thumbs are discussed in detail.

The filler-rubber interface in styrene butadiene nanocomposites with anisotropic silica particles: morphology and dynamic properties.

Silica-styrene butadiene rubber (SBR) nanocomposites were prepared by using shape-controlled spherical and rod-like silica nanoparticles (NPs) with different aspect ratios (AR = 1-5), obtained by a sol-gel route assisted by a structure directing agent. The nanocomposites were used as models to study the influence of the particle shape on the formation of nanoscale immobilized rubber at the silica-rubber interface and its effect on the dynamic-mechanical behavior. TEM and AFM tapping mode analyses of nanocomposites demonstrated that the silica particles are surrounded by a rubber layer immobilized at the particle surface. The spherical filler showed small contact zones between neighboring particles in contact with thin rubber layers, while anisotropic particles (AR > 2) formed domains of rods preferentially aligned along the main axis. A detailed analysis of the polymer chain mobility by different time domain nuclear magnetic resonance (TD-NMR) techniques evidenced a population of rigid rubber chains surrounding particles, whose amount increases with the particle anisotropy, even in the absence of significant differences in terms of chemical crosslinking. Dynamic measurements demonstrate that rod-like particles induce stronger reinforcement of rubber, increasing with the AR. This was related to the self-alignment of the anisotropic silica particles in domains able to immobilize rubber.