Use of a simple Leeds test object for rapid assessment of image intensifiers

Subjective and objective measures of image quality in digital fluoroscopy

There are numerous methods for assessing image quality in diagnostic X ray. In our study we assessed how imaging quality assurance methods perform in practice. Physics assessments were based on IPEM protocols using Leeds test objects. Clinical assessment was based on a questionnaire. A total of 15 systems in three European locations were assessed, covering a range of image intensifier-TV digital fluoroscopy units. Analysis of 274 clinical questionnaires showed that clinical and physics assessments did not place systems in the same order, based on a given image quality parameter. In almost all the comparisons, low level correlation was measured for statistical comparison of rank order (rs < 0.3). However, broad agreement was observed between physics and clinical assessments for image quality associated with contrast and noise. This study emphasises the importance of maintaining links with clinical assessment, when developing quality assurance metrics, and measuring the mutual performance of clinical and physical assessments of image quality.

A figure of merit for the assessment of image intensifier systems

A dimensionless figure of merit (F), which combines key aspects of the performance of image intensifier systems, is derived. This figure is ideally independent of input air kerma rate and field size and relates to the fundamental characteristics of the image reception chain. In practice it is calculated from measurements of the threshold contrast (noise) and limiting resolution using the Leeds test objects and the input air kerma rate. Several practical examples illustrate its usefulness in simple performance assessment and quality assurance procedures. A comparison is made with the use of detection index diagrams.

Assessment of radiology installations in Macedonia, Greece

Nine, small and large radiology installations in Macedonia, Greece using 40 generators and a total of 47 roentgen tubes were assessed and their work load was calculated. The results of quality control measurements in 39 of these (27 radiographic and 12 fluoroscopic tubes) are presented. The parameters measured were: (a) kvp, (b) radiation output, (c) timer accuracy, (d) field coincidence and (e) total filtering. For fluoroscopic equipment spatial resolution and radiation field alignment were also measured. Equipment exploitation seems to be very low, since more than half of the equipment was less than 8 years old, with a work load under 200 mA.min per week. The total work load was calculated to be about 4612 mA.min per week, corresponding to 123,960 patients. These were examined by 52 radiologists supported by 58 radiographers. Skin exposure was measured for fluoroscopy patients (2.8 +/- 2.7 R/mA per min), as well as for a set of routine radiographic examinations.