Biomedical subjects
Publications and source records attributed to G Contento.
The authors describe an afterloading brachytherapy to treat oral cavity carcinomas. Catheters for arterial/venous catheterization are inserted percutaneously in the target volume. The internal needles are then removed and replaced with iridium wires inside tubes to form wire loops. This technique has proven to be simple, quick and safe.
Recently, high-dose rate intracavitary irradiation has been used as a boost therapy or a palliative therapy in the treatment of the esophageal carcinoma. The new intraesophageal device is based on a modified Sengstaken-Blackemore tube. On the surface of the esophageal balloon of the S-B tube Cyponil tubes are fixed as iridium containers. The device is placed at the level of the neoplastic lesion. Treatment tolerance is good.
Flexible 192Ir wire implants are commonly used for the treatment of some types of cancer in the oral cavity. A modified technique of plastic tubes is here presented which aims at correctly positioning the active wires with thin plastic templates. Possible sources of error are examined and their consequences on the dose distribution around the implant are analyzed. In most cases control dosimetry matches the provisions satisfactorily. It may be thus concluded that the use of templates allows good and reproducible results to be obtained in the brachytherapy of the oral cavity.
Surveys have been conducted in Britain, France and Italy, using essentially the same techniques, to establish the level of provision of diagnostic radiology services, the frequency of X-ray examinations and examples of the radiation doses delivered to patients in each country. Different national strategies for conducting some types of X-ray examination and marked differences in the general availability of this aspect of health care indicate that the justification and optimization of medical exposures is not interpreted in the same way in these countries.
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A study has been conducted to asses the impact of radiological practice in 1983 in Friuli-Venezia Giulia, a region of North-east Italy with 1,250,000 inhabitants. The design involved three phases: a region-wide frequency survey; dosimetric measurements on patients in all public X-ray facilities; derivation of organ doses from those measurements. Frequencies by type, age and sex and values of the main technical parameters of radiological examinations are presented. Organ doses, effective dose equivalents and risk estimates are given for 14 selected examinations. The annual per-capita effective dose equivalent and the genetically significant dose are estimated at 0.848 mSv and 0.253 mSv, respectively. From these values, collective risks have been predicted by using the risk factors given in the International Commission on Radiological Protection Publication 26. The results indicate that 14 persons risk induced malignancies and 2.5 persons risk genetic detriment.
The response of a TL dosemeter to beta radiation is heavily influenced by the absorption of the radiation in the dosemeter thickness. As a consequence, the assessment of skin dose depends either on the execution of a calibration with a beta field of the same characteristics as that to be monitored or on the knowledge of depth-dose distribution in the dosemeter. Depth-dose distributions have been experimentally estimated for optically transparent dosemeters in a number of irradiation geometries and with sources of different configuration and energy. General algorithms based on the point-source function of Loevinger have been developed, by which the response of TL dosemeters can be evaluated and skin dose correction factors derived. TLD responses to beta radiation calculated by the present method are in sound agreement with other author's measurements. The dependence of beta ray absorption on the configuration of source and the source-to-detector distance has been picked up. Variations of source-to-detector distance as large as 30% of the maximum beta range account for differences up to 40% in the skin dose correction factors for a 200 mg cm-2 thick dosemeter. The proposed scheme results in a useful tool in skin beta dosimetry using multiple TLDs behind different absorbers. In practical applications thick dosemeters may be used properly only in well-known radiation fields. Conversely, the described method allows an acceptable estimate of the skin dose error.
The linear model of the nerve compound action potential (CAP) depends on the assumed waveform for the single fibre action potential (SFAP). A general method has been developed to investigate the influence of the unknown features of the SFAP on the estimation of nerve fibre conduction velocity (CV) distribution. A SFAP waveform is considered consistent with the model and the experimental data if recorded and reconstructed CAPS fit and the distribution is physically meaningful. Experimental CAPS were monopolarly recorded using surface electrodes over the median nerve at the wrist. To fit the model, SFAP waveforms must satisfy some internal relationship. The most important feature is that the ratio between positive and negative areas of the SFAP is almost one and does not vary in different subjects and recording sites. Many SFAP waveforms fit the model, and the relative conduction velocity distributions may be very different. These must be regarded as conventional distributions. As for inter-subject comparison, the dependence of the method on the recording site has been reduced by choosing the place where stimulus intensity and relative motor response amplitude have given values. In this recording environment CV distributions of normal subjects can be properly compared using the same SFAP and deviations from normality evidenced.
A new non-invasive electrode array has been devised to record electrical signals on the scalp. The electrodes are arranged every 10 mm in a 4 x 8 grid, thus totalling 32. Electrical coupling is assured by a column of conductor gel with a diameter of 2 mm. The electrode array has been used to record multichannel scalp potentials evoked by stimulation of the median nerve at the wrist. It was positioned on the parietal region with the midline corresponding to the external acoustic meatus. The high spatial resolution of this device allows a detailed spatial sampling of the scalp potential field where the electrical activity arising from the parietal and premotor cortex is predominant. Scalp potentials with the system are compared with those with the 10/20 system. The improved spatial resolution allows more precise localization of minimum and maximum of the potential field, though the overall distortion introduced by aliasing in the 10/20 system is not striking. Instead, the amplitudes of the fields are considerably affected by insufficient spatial sampling.
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