[en] Three current digital radiography modalities are briefly described: digital fluorography, storage phosphor radiography and amorphous selenium radiography. For all of these modalities, the dose used to form an image can be varied considerably. Threshold contrast detail techniques were used to investigate the consequence of changing dose per image at the image receptor. At low doses, contrast resolution is limited by X ray quantum noise while system noise limits contrast resolution at high dose per image values. (author)

[en] This paper addresses image quality and dose issues in Digital Fluorography (DF) and Digital Subtraction Angiography (DSA), commencing with a brief review of methods and protocols for image quality assessment in DF and DSA. The relative scarcity of standards and test protocols for unsubtracted DF is highlighted. Pooled results from a large number of quality assurance tests are then used to illustrate trends in the choice of radiation dose per image currently employed in typical DF and DSA work. It is concluded that, although relatively high doses per image may be justified in terms of image quality improvement for DSA, there is little justification for the large range of exposures used in DF for nominally identical examinations. It is argued that the use of high doses per image in DF would not be expected to offer an advantage in terms of image signal-to-noise ratio. (author)

[en] There are two main approaches to the establishment of reference doses for digital fluoroscopy/fluorography equipment. One involves the measurement of dose/image and dose rate when a suitable patient-equivalent phantom is placed in the primary beam. The other is based on the analysis of the results of a series of patient dose measurements for different examinations. Both methods have their advantages and disadvantages. The former can be incorporated into a programme of quality assurance measurements and facilitates comparison between different digital fluoroscopy units. Unfortunately there is no international scientific agreement on measurement protocols or standards, and the measured values are also critically dependent on the settings used by the automatic exposure control. Patient dosimetry measurements can be performed and have the advantage that risk and detriment can be determined for specific individuals. However, the effect of patient variability in terms of size and composition makes comparisons difficult. The results of a regional survey of digital fluoroscopy/fluorography equipment is presented and discussed in relation to the overall context of the meeting objectives (i.e. reference doses and quality assurance). (author)

[en] A fluoroscopy system is a relatively complicated piece of equipment made up of several sub-components. For the operator to achieve good image quality without the overhead of high patient and staff doses, it is essential that all of these components are set up correctly. The automatic exposure rate control (AEC) and image quality are important aspects of a fluoroscopy system. Two principal parameters are used to assess AEC function: air kerma rate at the input phosphor with 1.0 mm copper filtration added and entrance surface dose rate for a 20 cm Perspex phantom. Spatial resolution is measured using the Huettner type 18 spatial frequency grating. The Leeds TO10 contrast-detail test object is used to measure threshold contrast-detail performance. Median limiting spatial resolution was 1.41 lp.mm^-1 for image intensifier fields lying between 18 and 24 cm in diameter. Mean low contrast resolution at 63 kV and 0.40 μGy.s^-1 was 2.5%. (author)

[en] The air kerma-area product and scattered radiation dose in the vicinity of the patient couch, for both overcouch and undercouch X-ray tube geometries, were simultaneously monitored, with particular regard for risks to staff. The scattered radiation distribution at the couchside was deduced at a range of tube potentials for both overcouch and undercouch X-ray tube geometries. The variation of scattered radiation with field size on both geometries was investigated, as well as the variation with focus-table distance on an overcouch tube geometry. It was discovered that the scattered radiation dose at a point correlated with the air kerma-area product and the result may be used for radiation protection purposes. A method of predicting the scattered radiation dose at a given position is described. (author)

[en] Doses to 14 radiosensitive organs were measured as a function of field size for both antero-posterior (AP) and postero-anterior (PA) projections of the abdomen. The organ doses were measured using thermoluminescent dosemeters (TLD) placed within a Rando anthropomorphic phantom. Organ doses were also measured for the conventional 35 x 35 cm film/screen technique, for both AP and PA views. The dose measurements were made at a tube potential of 81 kV, which is commonly used in radiological examinations of the abdomen. TLD were also used to measure the entrance surface dose (with backscatter) for each field size and projection. Organ doses are presented normalized to this entrance surface dose. A brief comparison is made between the data measured in the current study and normalized organ dose data published by other authors. (author)

[en] Diagnostic radiology is the largest man-made contribution to the population dose in the United Kingdom. It is therefore of importance to monitor and reduce radiation dose levels in diagnostic radiology, if the principle of 'as low as reasonably achievable' is to be attained. The work presented here describes the adaptation of an electronic personal organiser or filofax (PSION II LZ64, PSION plc, London), which when used in combination with a Diamentor dose-area product meter will store information on the patient and examination as well as the dosimetry results. The electronic personal organiser can be linked to a thermal printer to provide a permanent record of the patient dosimetry information. The electronic personal organiser can be interrogated via a computer link for scientific analysis on a separate computer. (author)

[en] The difficulties of making the results of threshold contrast-detail diameter tests on X-ray image intensifier systems consistent with published performance standards are discussed. The current approach to contrast-detail testing is described and an alternative method intended to give greater consistency for all image intensifier input field diameters proposed. The current and alternative test conditions are compared on two image intensifier systems. The results obtained show that the contrast-detail curves for image intensifier systems with a wide range of input field diameters can be effectively normalized to be directly comparable to a common reference standard by applying the proposed alternative test conditions. The implications of this result on the interpretation of the contrast-detail test are discussed. (author)

[en] The objective of this experimental investigation was the measurement and analysis of the variations inherent in contrast-detail experiments performed with dynamic images obtained using image intensifier-TV systems. The results presented in this report enable the calculation of the uncertainty associated with a contrast-detail assessment of an image intensifier-TV system made with a given number of observers and a given number of image readings. (author)

[en] The recent recommendations of the International Commission on Radiological Protection (ICRP) introduced a supplementary dose limit for the surface of the abdomen of pregnant staff, to restrict the radiation dose to the foetus. This has wide ranging implications on the monitoring of staff in hospitals, some of which are studied here. The relationship between foetal dose, entrance surface dose to the abdomen and personal monitor reading was determined using an anthropomorphic phantom loaded with thermoluminescence dosemeters to record the dose to the uterus, as well as on the surface of the abdomen. Film badges were attached to the phantom at various anatomical positions. This phantom was irradiated for simulations of fluoroscopic examinations in diagnostic radiology and various brachytherapy treatments. The relationships between monitor reading and foetal dose have been derived, and a number of practical monitoring problems for pregnant staff discussed. (Author)