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QUALITY CRITERIA, TOLERANCES, LIMITING VALUES, DOSIMETRY AND OPTIMIZATION IN A NUMBER OF FLUOROSCOPIC, DIGITAL FLUOROSCOPIC, DSA AND DIGITAL RADIOLOGICAL SYSTEMS

Objective

This contract initiates work on bridging a gap which has opened up between major advances in radiological equipment and techniques, and the lack of developments in quality assurance, patient and staff Dosimetry, comparative dosimetry, and optimization of automatic exposure control and automatic brightness control in a number of systems.
The advantages and disadvantages of digital imaging methods are under evaluation. Imaging capabilities of digital II radiography were compared with conventional film and screen radiography. The parameters of spatial resolution, contrast and entrance dose (abdomen phantom) were measured. Depending on the dose, spatial resolution decreased significantly below a certain level for each image intensifier diameter. To lower the dose as much as possible it was fundamental to know what dose and image quality are necessary for special diagnostic questions.

Indications for digital II radiography can be divided into 3 groups:
highest image quality is necessary (eg examinations of the gastrointestinal tract in double contrast);
lower image quality (and dose) is possible (eg phleborgraphy, hysterosalpinography, examinations of the gastrointestinal tract in monocontrast);
lowest dose is necessary (eg functional examinations of the gastrointestinal tract in paediatrics, pelvimetry).

By measuring physical parameters and comparing images of specimen and patients with different preselected dose values recommendations were given for dose selection for these 3 classes of examinations. For examinations of the class 1 the entrance dose was in the range of 25% to 50%, for examinations of the class 3 the entrance dose was 5% compared to a film and screen combination.

For imaging of the chest digital II radiography and digital storage phosphor radiography were compared with spotfilm techniques, film/screen techniques and slot techniques. As a result digital II radiography cannot be recommended for imaging of the lung, because the spatial resolution for large entrance fields is not sufficient. Storage phosphor radiographs demonstrated a high image quality but gave only limited additional diagnostic information compared to film/screen radiographs. Dose could be lowered to 75% to 50% of film and screen combination. Dose values under 50% were connected to a significant decrease of i mage quality. Best imaging capabilities for chest at the wall stand were demonstrated by the slot technique.

Constancy tests are being developed for digital radiography and after 1 year it will be decided which parameters are necessary to characterize image quality of a digital image intensifier system.
Task 1 :
Characterization, evaluation, comparison and optimization of automatic exposure control and automatic brightness control in a number of systems.

Task 2 :
Identification of important variables, and where possible tolerances and limiting values, in the fluoroscopic/TV/cine/100mm/multiformat cameras and digital imaging systems. The variables are to include those suitable for constancy testing at one level and for acceptance or write-off of equipment at another.

Task 3 :
Dosimetry and optimization studies of conventional and corresponding digital techniques for cardiac, gastrointestinal, chest, peripheral vascular and paediatric studies.

Task 4 :
Patient and staff dosimetry in selected clinical studies.

In addition to the above, the work of the contract is being coordinated with that of Dr. Th. Schmidt BI6-343 so that the work programme in Tasks 3 and 4 will be integrated and the progress and final reports will be grouped.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Federated Dublin Volontary Hospital
Address
Garden Hill House
8 Dublin
Ireland

Participants (2)

Northern Regional Health Authority
United Kingdom
Address
Benfield Road
NE6 4PY Newcastle Upon Tyne
RUPRECHT-KARLS-UNIVERSITAET HEIDELBERG
Germany
Address
Seminarstrasse 2
69117 Heidelberg