in detail in Chapter 10 for conventional gamma cameras and are equally
applicable to multihead SPECT cameras.
Quality Control Tests for SPECT Cameras
Daily Tests
Photopeaking and Uniformity
The daily photopeaking and uniformity tests for SPECT cameras are the
same as for conventional gamma cameras described in Chapter 10 with
more stringent requirements. These tests must be done for each head of the
system. In SPECT systems, nonuniformities are substantially magnified by
the filtered FBP method causing a ring artifact in the image particularly at
the center of rotation. To achieve uniformity on SPECT images, UFOV
nonuniformity should be less than 1%. Ideally this can be achieved by
acquiring at least 30 million counts for 64 ×64 images or 120 million counts
for 128 ×128 images. For practical reasons, however, 5 million counts for
large FOV cameras and 3 million counts for small FOV cameras are appro-
priate. For Siemens e-Cam cameras, acquisition of 5 million counts in a 1024
×1024 matrix is recommended.
Weekly Tests
Spatial Resolution
For single-head or multihead SPECT cameras, spatial resolution for each
head is checked by using bar phantoms in the same manner as conventional
gamma cameras described in Chapter 10. In determining spatial resolution
by the intrinsic method, the two detectors must be kept apart at maximum
radius, and a 99 mTc point source is placed in a source holder on the rear bed
mechanism provided by the manufacturer. The bar phantom is placed on
the detector, and the bed is raised to a maximum height.
Center of Rotation
The COR corrections are performed weekly or bi-weekly using the com-
puter software provided by the manufacturer. To begin COR corrections,
the camera face must be parallel to the axis of rotation. Generally, a point
or line source is placed in the FOV of the camera and then SPECT scans
of the source are obtained for 360°. The software analyzes the scans and
determines if the COR is within acceptable limits.
Nowadays, many manufacturers provide a phantom using 5-point sources
for low-energy high-resolution collimators or 3-point sources for medium-
and high-energy collimators. The phantom with the sources in position is
178 12. Single Photon Emission Computed Tomography