Solid State Detector; Power; Interface Connections - Hologic QDR 4500 Technical Manual

Solid State Detector

The Solid State Detector boards convert X-rays into signals that are applied to the
Integrator/Multiplexor board. X-rays striking detector crystals are converted into visible light.
Solid State photo diodes sense this light and convert the light into current which is amplified in a
current to voltage converter. Output from the amplifier is applied to the Integrator through analog
switches. The analog switches all operate in parallel and are turned on during the X-ray pulse.
These switches are turned off during the integrator hold time to prevent integrating noise into the
data. The turning on and off of these switches is controlled by the INTEGRATE signal supplied
from the Integrator/Multiplexor board. Each solid state detector board has a capacity of either 36
low resolution detectors, or 72 high resolution detectors. Depending on the model, detector
boards may be either fully or partially populated by low resolution or high resolution detectors,
and amplifiers.
The detector assembly is available in two resolutions and two lengths. Detectors may be 2mm or
4mm at the detector. This is equal to slightly less than 1mm or 2mm resolution in an AP spine.
Detector arrays may contain 64 4mm detectors, or 128 (or 216) 2mm detectors. Most scans can
be done with the shorter arrays. The longer arrays are only necessary for three pass whole body
scans.

Power

The Solid State Detector board receives +/-15V from the Integrator/Multiplexor board. Voltage
regulators, located on this board, convert this voltage to +/-12V to power the amplifiers and
switches.

Interface Connections

Figure 2-15 shows the interconnections between the Integrator/Multiplexor board and the Solid
State Detector boards. Table 2-21 describes the interface signals and identifies the
interconnection connector and pin assignments.
INTEGRATOR/MULTIPLEXOR
BOARD
Figure 2-15. Integrator/Multiplexor Board/Solid State Detector Boards
Section 2 - Functional Description
CHANNEL0 - CHANNEL215
INTEGA - INTEGF
+15V
15V_RET
-15V
Interconnection Diagram
SILICON
DETECTOR
BOARDS
2-27