Transcript A Silicon Microstrip Sensor for Use in Dental Digital

A silicon microstrip sensor for
use in dental digital radiography
P.F. van der Stelt
Academic Centre for Dentistry Amsterdam,
Amsterdam, the Netherlands
F.A. Triantis - University of Ioannina, Ioannina, Greece
R.D. Speller - University College London, London, United Kingdom
G. Hall, G.M. Iles - Imperial College, London, United Kingdom
Introduction
• Many medical imaging procedures are
now digital
• Main requirements are:
– size large enough to cover the ROI
– resolution diagnostically adequate
– patient dose clinically acceptable
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Solid state sensor systems
• pixel sensors
– high event rate capability
– high overhead requirement
• strip sensors
– simpler readout structures
– event rate limiting ambiguities
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Aim
To develop and evaluate a new
sensor using
silicon microstrip technology
for 2-D medical and dental
radiographic imaging
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dacq electronics
Technology
data acquisition electronics
metal “strips” embedded in silicon
• perpendicular on both sides of the chip
• photons produce secondary electrons
• electrical charge is depleted by the strips
•
front-end
electronics
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Technology
photon
photon
electrons
silicon
microstrips
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SMS technology
• photon counting characteristics
(different from conventional,
integrating sensors)
• enabling dual energy techniques
• possibility of increased resolution by
weighed read-out of adjacent strips
• using existing chips
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Results of Monte Carlo simulation
• detection efficiency is sufficient for dental
applications when a 300 µm sensor is used;
• pixel counts of <1000 can provide good image
quality;
• even at 200 counts per pixel, high contrast
details of 300 µm are detectable.
Speller et al. Nucl Instr and Meth A 457 (2001) 359
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Prototype silicon microstrip
detector
• 300 µm double-sided silicon sensor
(SINTEF, Oslo, Norway)
• p-side 427 strips on a 50 µm pitch
• n-side 128 strips on an 80µm pitch
• effective area 2.185 x 1.024 cm2
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Prototype (cont’d)
• four APV chips (each 128 channels) with
pitch adaptor to read out the p-side (427
strips)
• one APV chip with pitch adapter to read
out the n-side (128 strips)
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P-side
427 strips, 4 APV’s (2 bonded at this time)
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N-side
128 strips, 1 APV
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Hybrid architecture
VME Crate
Sensor
APV 1
APV 2
APV 3
R
I
O
2
APV 0
APV 4
S
E
Q
S
I
Hybrid
F
E
D
Signal
Conditioning
5x APV output
Clock and Trigger
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Slow Control
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I
2
C
Data procssing
and image correction
• gain variation of individual strips corrected for by
subtraction of factor obtained from flat field
image;
• pixels in dead strips were assigned average of
pixels on either side;
• different aspect ratio of pixels corrected by using
each pixel 2 times along the 80 µm and 3 times
along the 50 µm direction.
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Imaging results
Test images of “real” dental
objects to determine the
physical and diagnostic image
quality
– molar
– incisor
– jaw section
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Image preprocessing
Raw data
Removing non-uniformities
by flat field subtraction
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Image preprocessing
Dead-strip correction
Aspect ratio correction
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First images
Molar
• enamel
• dentine
• root canal
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First images
Incisor
• enamel
• dentine
• root canal
• restoration
• crack in enamel
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First images
Jaw segment
• tooth structures
• tooth ligament
• bone architecture
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Conclusion
2-D silicon microstrip technology is
a promising technology for
building imaging sensors for use
in dental radiography.
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Future work
• Improvement of read-out electronics
• Dose measurements
(in addition to the theoretical
calculations)
• Reduction in sensor size
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Acknowledgement
This project has been funded by the European
Commission under the Biomed-2 scheme,
contract no. BMH4-CT96-1119,
“Biomedical Radiography and Radioscopy
using Silicon Microstrip Sensors”
(BRSMS)
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