A linear array silicon pixel detector: images of a mammographic test object and evaluation of delivered doses.
We present images of a mammographic test object obtained using a linear array silicon pixel detector capable of single-photon counting. The detector pixel size was 200 x 300 microns2 and images were acquired by scanning the test object between the laminar detector and the x-ray source with a scanning step of 100 microns. A molybdenum anode tube was used with two different filtrations: 2 mm aluminium and 25 microns molybdenum. Conventional film-screen images were also obtained in order to compare spatial and contrast resolution. In our digital images it is possible to recognize low-contrast details having dimensions smaller than or equal to the dimensions of details visible by means of a clinical mammographic unit. The detection of microcalcifications smaller than 150 microns was possible only when using the Mo filtration. However a copper wire of 50 microns diameter was detectable when embedded in a simulated tissue. We discuss in detail the mean glandular doses (MGDs) delivered during the image acquisition. The MGDs necessary to obtain good-quality images are always smaller than at a conventional mammographic unit. Since MGDs depend on the x-ray spectrum, the dose reduction becomes larger when the applied spectrum is harder than in film-screen acquisition (Al filtration and 35 kVp).
Arfelli
F
F
Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Italy.
Bonvicini
V
V
Bravin
A
A
Cantatore
G
G
Castelli
E
E
Palma
L D
LD
Michiel
M D
MD
Longo
R
R
Olivo
A
A
Pani
S
S
Pontoni
D
D
Poropat
P
P
Prest
M
M
Rashevsky
A
A
Tromba
G
G
Vacchi
A
A
D005260:Female; D006801:Humans; D008327:Mammography / Q000295:instrumentation* / Q000379:methods*; D008982:Molybdenum; D019047:Phantoms, Imaging; D017785:Photons; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012680:Sensitivity and Specificity; D012825:Silicon
D008982:Molybdenum; D012825:Silicon