[The reduction of the radiation dosage by means of storage phosphor-film radiography compared to a conventional film-screen system with a grid cassette on a skull phantom].
OBJECTIVE
How much can the radiation dose be reduced for skull radiography by using digital luminescence radiography (DLR) compared to a conventional screen film system with a grid cassette?


METHODS
A skull phantom (3M) was x-rayed in anterior-posterior orientation using both a conventional screen film system with grid cassette and DLR (ADC-70, Agfa). The tube current time product (mAs) was diminished gradually while keeping the voltage constant. The surface entrance dose was measured by a sensor of Dosimax (Wellhöfer). Five investigators evaluated the images by characteristic and critical features, spatial resolution and contrast.


RESULTS
The surface entrance dose at 73 kV/22 mAs was 0.432 mGy in conventional screen film system and 0.435 mGy in DLR. The images could be evaluated very well down to an average dose of 71% (0.308 mGy; SD 0.050); sufficient images were obtained down to an average dose of 31% (0.136 mGy; SD 0.065). The resolution of the line pairs were reduced down to 2 levels depending on the investigator. Contrast was assessed as being very good to sufficient. The acceptance of the postprocessed images (MUSICA-software) was individually different and resulted in an improvement of the assessment of bone structures and contrast in higher dose ranges only.


CONCLUSIONS
For the sufficient assessment of a possible fracture/of paranasal sinuses/of measurement of the skull the dose can be reduced to at least 56% (phi 31%; SD 14.9%)/40% (phi 27%; SD 9.3%)/18% (phi 14%; SD 4.4%). Digital radiography allows question-referred exposure parameters with clearly reduced dose, so e.g. for fracture exclusion 73 kV/12.5 mAs and to skull measurement 73 kV/4 mAs.
Heyne
J P
JP
Institut für Diagnostische und Interventionelle Radiologie, Friedrich-Schiller-Universität Jena.
Merbold
H
H
Sehner
J
J
Neumann
R
R
Freesmeyer
M
M
Jonetz-Mentzel
L
L
Kaiser
W A
WA
D005069:Evaluation Studies as Topic; D006801:Humans; D008163:Luminescent Measurements; D015588:Observer Variation; D019047:Phantoms, Imaging / Q000706:statistics & numerical data; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D012886:Skull / Q000000981:diagnostic imaging*; D012887:Skull Fractures / Q000000981:diagnostic imaging; D014963:X-Ray Intensifying Screens / Q000706:statistics & numerical data