[High-contrast resolution of film-screen systems in oral and maxillofacial radiology].
OBJECTIVE
The aim was to determine differences in high-contrast resolution of film-screen systems used in dental panoramic and cephalometric radiography by calculating the modulation transfer function (MTF). The radiographs used to determine the MTF should be taken by the same x-ray units as those used for patient radiographs.


METHODS
The MTF was determined using a lead grid and according to DIN 6867-2 for 11 film-screen systems (speed 250, speed class 200 and 400) used in dental radiographic diagnostics. The optical density was measured using a microdensitometer developed by PTB.


RESULTS
With 10% of the modulation transfer factor, newly developed film-screen systems (speed class 200 and 400) demonstrated a resolution of 4.9 to 6 line pairs per mm (panoramic radiography). In cephalometric radiography a film-screen system (speed class 400 and green-sensitive film) had a resolution of 4.2 line pairs per mm and surpassed two film-screen systems (speed class 400, resolution of 3 line pairs per mm, blue-sensitive films).


CONCLUSIONS
The relevance of this study is underlined by the diagnostic reference doses defined in the German X-ray Ordinance (RöV) which are also intended for dentistry. Film-screen systems (speed 250, speed class 200) previously used in dental panoramic and cephalometric radiography can be replaced by newly developed film-screen systems (speed class 400). In dental radiography dose reductions are possible with film-screen systems (speed class 400) without impairing diagnostic accuracy. The introduction of newly developed film-screen systems (speed class 400) requires lower milliampere-seconds and therefore an adjustment of the x-ray units to lower milliampere settings.
Kaeppler
G
G
Zentraler Röntgenbereich, ZZMK, Universitätsklinikum Tübingen, Tübingen. gabriela.kaeppler@med.uni-tuebingen.de
Reinert
S
S
D005145:Face / Q000000981:diagnostic imaging*; D006801:Humans; D008437:Maxilla / Q000000981:diagnostic imaging*; D009055:Mouth / Q000000981:diagnostic imaging*; D011859:Radiography; D011871:Radiology / Q000379:methods*; D012680:Sensitivity and Specificity; D013679:Technology, Radiologic / Q000379:methods*