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OBJECTIVES: This study aims to illustrate a multiparametric automatic method for monitoring long-term reproducibility of digital mammography systems, and its application on a large scale. METHODS: Twenty-five digital mammography systems employed within a regional screening programme were controlled weekly using the same type of phantom, whose images were analysed by an automatic software tool. To assess system reproducibility levels, 15 image quality indices (IQIs) were extracted and compared with the corresponding indices previously determined by a baseline procedure. The coefficients of variation (COVs) of the IQIs were used to assess the overall variability. RESULTS: A total of 2553 phantom images were collected from the 25 digital mammography systems from March 2013 to December 2014. Most of the systems showed excellent image quality reproducibility over the surveillance interval, with mean variability below 5%. Variability of each IQI was 5%, with the exception of one index associated with the smallest phantom objects (0.25 mm), which was below 10%. CONCLUSIONS: The method applied for reproducibility tests-multi-detail phantoms, cloud automatic software tool to measure multiple image quality indices and statistical process control-was proven to be effective and applicable on a large scale and to any type of digital mammography system. KEY POINTS: • Reproducibility of mammography image quality should be monitored by appropriate quality controls. • Use of automatic software tools allows image quality evaluation by multiple indices. • System reproducibility can be assessed comparing current index value with baseline data. • Overall system reproducibility of modern digital mammography systems is excellent. • The method proposed and applied is cost-effective and easily scalable.

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The performance of an automatic software package was evaluated with phantom images acquired by a full-field digital mammography unit. After the validation, the software was used, together with a Leeds TORMAS test object, to model the image acquisition process. Process modelling results were used to evaluate the sensitivity of the method in detecting changes of exposure parameters from routine image quality measurements in digital mammography, which is the ultimate purpose of long-term reproducibility tests. Image quality indices measured by the software included the mean pixel value and standard deviation of circular details and surrounding background, contrast-to-noise ratio and relative contrast; detail counts were also collected. The validation procedure demonstrated that the software localizes the phantom details correctly and the difference between automatic and manual measurements was within few grey levels. Quantitative analysis showed sufficient sensitivity to relate fluctuations in exposure parameters (kV(p) or mAs) to variations in image quality indices. In comparison, detail counts were found less sensitive in detecting image quality changes, even when limitations due to observer subjectivity were overcome by automatic analysis. In conclusion, long-term reproducibility tests provided by the Leeds TORMAS phantom with quantitative analysis of multiple IQ indices have been demonstrated to be effective in predicting causes of deviation from standard operating conditions and can be used to monitor stability in full-field digital mammography.

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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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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.

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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.

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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.

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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.

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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.

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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.

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