Path:Index:Aquisition
Various different acquisitions can be performed with a SPECT
camera.
1. Planar Imaging
The simplest acquisition protocol is the
planar image. With planar imaging, the detector array
is stationary over the patient, and acquires data only from this one angle.
The image created with this type of acquisition is similar to an X-ray
radiograph. Bone scans are done primarily in this fashion.
2. Planar Dynamic Imaging
Since the camera remains at a fixed position
in a planar study, it is possible to observe the motion of a radiotracer
through the body by acquiring a series of planar images of the patient
over time. Each image is a result of summing data over a short time
interval, typically 1-10 seconds. If many projections are taken over
a long time, then an animation of the tracer movement can be viewed and
data analysis can be performed. The most common dynamic planar scan
is to measure glomerular filtration rate in the kidneys.
3. SPECT Imaging
If one rotates the camera around the patient,
the camera will acquire views of the tracer distribution at a variety of
angles. After all these angles have been observed, it is possible to reconstruct
a three dimensional view of the radiotracer distribution within the body.
This is explained in the section of reconstruction.
4. Gated SPECT Imaging
As the heart is a moving object, by performing a regular
SPECT of the heart, the end image obtained will represent the average
position of the heart over the time the scan was taken. It is possible
to view the heart at various stages of its contraction cycle however, by
subdividing each SPECT projection view into a series of sub-views, each
depicting the heart at a different stage of it's cycle. In order
to do this, the SPECT camera must be connected to an ECG machine which
is measuring the heart beat.