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Biomedical subjects

G Cantatore

Publications and source records attributed to G Cantatore.

At least 19 recordsLinked to original sources
PubMed2007

The corrosion of nickel-titanium rotary endodontic instruments in sodium hypochlorite.

AIM: To evaluate the corrosion resistance of nickel-titanium (NiTi) endodontic rotary instruments immersed in 5.25% sodium hypochlorite (NaOCl) solution. METHODOLOGY: The corrosion performance of NiTi instruments (S1 25 mm, ProTaper Dentsplay Maillefer, Ballaigues, Switzerland) was evaluated using commercial 5.25% NaOCl solution (pH = 12.3), and the same solution partially neutralized adding H2SO4 to reach pH = 10.1. Electrochemical measurements were carried out using a potentiostat equipped with a five-channel zero resistance ammeter (ZRA) for galvanic current measurements. The instruments were sectioned into three parts (cutting part, noncutting part and shank) and degreased with acetone and rinsing with demineralized water prior to being immersed in NaOCl solution for testing. Each set of the three parts constituted one 'virtual' instrument through the ZRA, giving access to the galvanic currents that circulate between the three parts. Nine instruments were employed to check the reproducibility of the electrochemical measurements. RESULTS: The corrosion potential (E(corr)) of the NiTi alloy reached the passive domain in approximately 20 s of immersion in the solution having a pH 10.1. After this initial period the potential remained steady, indicating that stable passivation was achieved. However, at pH 12.3 no stationary state was achieved even after 6000 s of immersion time. Thus, the alloy was not stable in this medium from a corrosion point of view. CONCLUSIONS: The corrosion resistance of NiTi alloy was enhanced by lowering the pH of NaOCl solution to 10.1, which allows the system to reach the stability domain of the passivating species TiO2 and NiO2.

Corrosion↗
PubMed2006

Experimental observation of optical rotation generated in vacuum by a magnetic field.

We report the experimental observation of a light polarization rotation in vacuum in the presence of a transverse magnetic field. Assuming that data distribution is Gaussian, the average measured rotation is (3.9 +/- 0.5) x 10(-12) rad/pass, at 5 T with 44 000 passes through a 1 m long magnet, with lambda = 1064 nm. The relevance of this result in terms of the existence of a light, neutral, spin-zero particle is discussed.

Journal Article↗
PubMed2001

An innovative digital imaging set-up allowing a low-dose approach to phase contrast applications in the medical field.

Recently, new imaging modalities based on the detection of weak phase perturbations effects, among which are phase contrast and diffraction imaging, have been developed by several researchers. Due to their high sensitivity to weakly absorbing details, these techniques seem to be very promising for applications in the medical field. On the other hand, digital radiology is undergoing a wide diffusion, and its benefits are presently very well understood. Up to now, however, the strong pixel size constraints associated with phase contrast pattern detection limited the possibility of exploiting the advantages of phase contrast in digital radiology applications. In this paper, an innovative setup capable of removing the pixel size constraints, and thus opening the way to low dose digital phase contrast imaging, is described. Furthermore, we introduce an imaging technique based on the detection of radiation scattered at small angles: the information extracted from the sample is increased at no dose expense. We believe that several radiological fields, mammography being the first important example, may benefit from the herein described innovative imaging techniques.

Diagnostic Imaging↗
PubMed2000

Experimental evaluation of a simple algorithm to enhance the spatial resolution in scanned radiographic systems.

In order to ensure an early diagnosis of breast cancer, an imaging system must fulfil extremely stringent requirements in terms of dynamic range, contrast resolution and spatial resolution. Furthermore, in order to reduce the dose delivered to the patient, a high efficiency of the detector device should be provided. In this paper the SYRMEP/FRONTRAD (SYnchrotron Radiation for MEdical Physics/FRONTier RADiology) mammography project, based on synchroton radiation and a novel solid state pixel detector, is briefly described. Particular relevance is given to the fact that the radiographic image is obtained by means of a scanning technique, which allows the possibility of utilizing a scanning step smaller than the pixel size. With this procedure, a convolution between the real image and the detector point spread function (PSF) is actually acquired: by carefully measuring the detector PSF, it is possible to apply a post-processing procedure (filtered deconvolution), which reconstructs images with enhanced spatial resolution. The image acquisition modality and the deconvolution algorithm are herein described, and some test object images, with spatial resolution enhanced by means of the filtered deconvolution procedure, are presented. As discussed in detail in this paper, this procedure allows us to obtain a spatial resolution determined by the scanning step, rather than by the pixel size.

Algorithms↗
PubMed2000

Mammography with synchrotron radiation: phase-detection techniques.

The authors evaluated the effect on mammographic examinations of the use of synchrotron radiation to detect phase-perturbation effects, which are higher than absorption effects for soft tissue in the energy range of 15-25 keV. Detection of phase-perturbation effects was possible because of the high degree of coherence of synchrotron radiation sources. Synchrotron radiation images were obtained of a mammographic phantom and in vitro breast tissue specimens and compared with conventional mammographic studies. On the basis of grades assigned by three reviewers, image quality of the former was considerably higher, and the delivered dose was fully compatible.

Absorption↗
PubMed1998

Low-dose phase contrast x-ray medical imaging.

Phase contrast x-ray imaging is a powerful technique for the detection of low-contrast details in weakly absorbing objects. This method is of possible relevance in the field of diagnostic radiology. In fact, imaging low-contrast details within soft tissue does not give satisfactory results in conventional x-ray absorption radiology, mammography being a typical example. Nevertheless, up to now all applications of the phase contrast technique, carried out on thin samples, have required radiation doses substantially higher than those delivered in conventional radiological examinations. To demonstrate the applicability of the method to mammography we produced phase contrast images of objects a few centimetres thick while delivering radiation doses lower than or comparable to doses needed in standard mammographic examinations (typically approximately 1 mGy mean glandular dose (MGD)). We show images of a custom mammographic phantom and of two specimens of human breast tissue obtained at the SYRMEP bending magnet beamline at Elettra, the Trieste synchrotron radiation facility. The introduction of an intensifier screen enabled us to obtain phase contrast images of these thick samples with radiation doses comparable to those used in mammography. Low absorbing details such as 50 microm thick nylon wires or thin calcium deposits (approximately 50 microm) within breast tissue, invisible with conventional techniques, are detected by means of the proposed method. We also find that the use of a bending magnet radiation source relaxes the previously reported requirements on source size for phase contrast imaging. Finally, the consistency of the results has been checked by theoretical simulations carried out for the purposes of this experiment.

Biopsy↗
PubMed1998

Mammography of a phantom and breast tissue with synchrotron radiation and a linear-array silicon detector.

A linear-array, silicon pixel detector, capable of counting single photons, was applied to mammography by using a synchrotron radiation beam. Images were obtained of both a mammographic phantom and a breast-tissue sample. The phantom image was acquired with a mean glandular dose of 0.32 mGy. This detector combined with a synchrotron radiation beam allows acquisition of high-contrast, low-dose images of soft tissues.

Breast↗
PubMed1997

A linear array silicon pixel detector: images of a mammographic test object and evaluation of delivered doses.

We present images of a mammographic test object obtained using a linear array silicon pixel detector capable of single-photon counting. The detector pixel size was 200 x 300 microns2 and images were acquired by scanning the test object between the laminar detector and the x-ray source with a scanning step of 100 microns. A molybdenum anode tube was used with two different filtrations: 2 mm aluminium and 25 microns molybdenum. Conventional film-screen images were also obtained in order to compare spatial and contrast resolution. In our digital images it is possible to recognize low-contrast details having dimensions smaller than or equal to the dimensions of details visible by means of a clinical mammographic unit. The detection of microcalcifications smaller than 150 microns was possible only when using the Mo filtration. However a copper wire of 50 microns diameter was detectable when embedded in a simulated tissue. We discuss in detail the mean glandular doses (MGDs) delivered during the image acquisition. The MGDs necessary to obtain good-quality images are always smaller than at a conventional mammographic unit. Since MGDs depend on the x-ray spectrum, the dose reduction becomes larger when the applied spectrum is harder than in film-screen acquisition (Al filtration and 35 kVp).

Female↗
PubMed1992

Vascular injury related to lumbar disk surgery.

The authors report a case of left common iliac artery injury, as a complication of diskectomy, in a 57 year-old male patient, with herniated disk at L4-L5. A review shows that L4-L5 disk space is the most common site for this rare complication of lumbar disk surgery.

Hemorrhage↗
PubMed1991

[Canal obturation. Analysis of 4 different techniques].

The Authors evaluate four different techniques for root canal filling by means of a stereo-microscope analysis of extracted teeth sections. The results indicate that: 1) the single-cone technique shows poor apical seal; 2) the Mc Spadden thermomechanical condensation technique produces good apical seal but often causes overfilling; 3) the vertical condensation and 4) the lateral condensation of gutta-percha confirm their efficacy, nevertheless the Authors recommend the second one because it is easier and request shorter time of execution.

Dental Leakage↗
PubMed1990

[Causes and treatment of technical accidents in endodontics].

Endodontic practice is not risk-free; a variety of technical accidents can complicate root canal treatment, influencing the prognosis and prejudicing the chances of the success. Although such events are infrequent, the author presents a review of the various types of accidents, which he examines in the light of correct diagnosis, prognosis and treatment on the basis of material collected in hospitals and private surgeries.

Dental Pulp Cavity↗
PubMed1989

Doppler velocimetry measurements of phototactic response in flagellated algae.

A periodic shading mechanism (about 0.5 s period) is believed to be used by flagellated algae to detect light direction. Time changes in the orientation of a population of Haematococcus pluvialis under positive photoaxis conditions (cell samples were stimulated alternatively by two diametrically opposed beams of actinic light), have been investigated by analysing the Doppler shifts of laser light scattered by the cells by means of heterodyne detection techniques. This technique allows us to measure the mean value of the component of the cells' swimming velocities along the light stimulus axis. Preliminary data indicate that the time taken by a cell population to change orientation is about 1 s.

Cell Movement↗