J Nucl Med 2002 Jul;43(7):876-81
Effect of respiratory gating on quantifying PET images of lung cancer.
Nehmeh SA, Erdi YE, Ling CC, Rosenzweig KE, Schoder H, Larson SM, Macapinlac HA,
Squire OD, Humm JL.
We have developed a new technique to gate lung 18F-FDG PET images in
synchronization with the respiratory motion to reduce smearing due to breathing
and improve quantitation of 18F-FDG uptake in lung lesions. METHODS: A
camera-based respiratory gating system, the real-time position management (RPM),
is used to monitor the respiratory cycle. The RPM provides a trigger to the PET
scanner to initiate the gating cycle. Each respiratory cycle is divided into
discrete bins triggered at a defined amplitude or phase within the patient's
breathing motion, into which PET data are acquired. The acquired data within the
time bins correspond to different lesion positions within the breathing cycle.
The study includes 5 patients with lung cancer. RESULTS: Measurements of the
lesions' volumes in the gated mode showed a reduction of up to 34% compared with
that of the nongated measurement. This reduction in the lesion volume has been
accompanied by an increase in the intensity in the 18F-FDG signal per voxel.
This finding has resulted in an improvement in measurement of the maximum
standardized uptake value (SUV(max)), which increased in 1 patient by as much as
159%. The total lesion glycolysis, defined as the product of the SUV(max) and
the lesion volume, was also measured in gated and nongated modes and showed a
consistency between the 2 measurements. CONCLUSION: We have shown that image
smearing can be reduced by gating 18F-FDG PET images in synchronization with the
respiratory motion. This technique allows a more accurate definition of the
lesion volume and improves the quantitation specific activity of the tracer (in
this case, 18F-FDG), which are distorted because of the breathing motion.
