[A bimetal anode with tungsten or rhodium? Comparative studies on image quality and dosage requirement in mammography].
OBJECTIVE
The impact of different anode materials (tungsten and rhodium) on spatial resolution, image contrast and radiation exposure was studied.


METHODS
Two mammographic systems providing bimetal x-ray tubes (Mo/W and Mo/Rh) were compared by imaging a breast radiography phantom with additional acrylic plates from 3 to 8 cm thickness. Spatial resolution was evaluated using a line bar pattern. Image contrast was assessed by measuring the ratio of optical densities in a acrylic step-wedge. The entrance dose was measured with a low energy ionisation chamber.


RESULTS
The spatial resolution was about 13 lp/mm regardless of the beam quality. The image contrast depended substantially on the thickness. A similar image contrast was found with Mo/Mo, Mo/Rh and Rh/Rh for simulated breast thicknesses of 4 to 6 cm and with Rh/Rh and W/Rh for 7 cm. In comparison to Mo/Mo the dose reduction was significant for Mo/Rh (35%), Rh/Rh (50%) and W/Rh (60%).


CONCLUSIONS
Bimetal x-ray tubes provide optimal conditions for screen film mammography of both normal and dense breasts, allowing good contrast and dose reduction by using the adequate anode/filter-combination.
Abteilung Röntgendiagnostik I, Georg-August-Universität Göttingen.
M
M
Funke
K P
KP
Hermann
N
N
Breiter
J
J
Moritz
D
D
Müller
E
E
Grabbe
D004566:Electrodes; D004867:Equipment Design / Q000706:statistics & numerical data; D005069:Evaluation Studies as Topic; D005260:Female; D005374:Filtration / Q000295:instrumentation; D006801:Humans; D008327:Mammography / Q000295:instrumentation* / Q000592:standards / Q000706:statistics & numerical data; D008982:Molybdenum; D019047:Phantoms, Imaging / Q000706:statistics & numerical data; D011786:Quality Control; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000592:standards; D012238:Rhodium; D014414:Tungsten; D014963:X-Ray Intensifying Screens / Q000706:statistics & numerical data
D008982:Molybdenum; D012238:Rhodium; D014414:Tungsten
Bimetallanode mit Wolfram oder Rhodium? Vergleichende Untersuchungen zur Bildqualität und zum Dosisbedarf in der Mammographie.