large solid angle (f/0.9), 10,042-hole, point-focus
collimators are each coupled to a 54x81 mm crystal
array viewed by six, 19 mm PMTs. Foci of the
collimators uniformly sample one transaxial slice.Both
the 30 and 50 are available in two choices of detectors,
the X and G. The X- are limited to
imaging I-125 tagged compounds while the
G-detectors can image all the commonly used
field-of-view is 50 mm in diameter within a
70 mm diameter opening. Setting the number of slices
and slice spacing determines the volume scanned.
from zero to 5 mm in increments of 100 microns.
A single slice can be acquired at full sensitivity in as
short as 30 seconds. Repeated fast scanning of a
specified slice is available.
800 microns (FWHM) in all directions for objects
with adequate counts and contrast. (The corresponding
volume resolution is 512 nanoliters.)
31,000 cps per
MBq for each detector.
is approximately 100 kg. Gantry is 80 cm high,
60 cm wide and 50 cm deep. The bed extends
forward 60 cm. Power required is <500 W.
Each of the
eight detector heads has six PMTs, six MCAs and a high
voltage supply. A UNIX-based embedded micro-controller is
used for motion control and data acquisition from all 48,
software supports internal multitasking. This allows a
single application to perform "off-line" 3D
reconstructions while acquiring data from the scanner,
performing slice-by-slice (2D) reconstructions on the
incoming data, and simultaneously viewing and analyzing
The scan is
initiated with the click of a button after selection of
setup parameters. Quality control procedures and data
acquisition are built into the application. The last 32
QC results are saved.
There are two
forms of reconstruction. Both use the same maximum
a-posteriori (MAP) algorithm. The first reconstructs one
slice at a time and is intended to provide real-time
images to the operator while a scan is in progress. The
second is an adaptive, fully 3-dimensional reconstruction
providing the highest image quality both in terms of
resolution and quantitation. The 3D reconstruction starts
only after data from all slices are available and takes
approximately 10 to 20 minutes depending on the number of
studies may be viewed concurrently in three orthogonal
views using multiple color scales. The user can interact
with the image volume to create arbitrary sets of slices
along any direction with arbitrary spacing and size.
Files exportable in industry standard formats.
standard configuration hi-end Macintosh is included with
the scanner. Presently, this 18+ Gflops workstation comes
with dual 2.0 GHz PowerPC G5 vector processors, 2 GB
SDRAM, a 120 GB hard drive, 1gb/s Ethernet, 4 USB and 2
FireWire ports and a flat 23 inch (1920x1200 pixel) Apple