RT Journal Article
SR Electronic
T1 How many gates? The effect of the number of gates on respiratory gated PET data
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1471
OP 1471
VO 50
IS supplement 2
A1 Mohammad Dawood
A1 Florian Buether
A1 Michael Schafers
A1 Otmar Schober
A1 Klaus Schafers
YR 2009
UL http://jnm.snmjournals.org/content/50/supplement_2/1471.abstract
AB 1471 Objectives The aim of this study was to find the optimal number of gates in respiratory gated PET studies. Methods The respiratory signal was acquired with a video camera which tracked a marker placed on the patient body. The position of the marker over time gave the respiratory curve of the patient. Simultaneously, PET data was acquired in listmode. The PET data was then divided into different numbers of gates (2 to 20) by using 2 different methods: time-based and amplitude-based sorting. The data was then reconstructed and analyzed with respect to 2 properties: 1) Precision in capturing the respiratory motion of the heart, 2) Signal to Noise Ratio (SNR).The motion of the heart was calculated by segmenting the myocardium of the LV and calculating its center of mass. The extent of motion is then the maximum difference in this position among all gates. For the calculation of the SNR a homogenous area was selected in the right lung. The standard deviation of the values in this area was taken as a measure of noise. Results The precision in detecting the motion of the heart is dependent upon the number of gates. In all datasets differences up to 280% were seen when the number of gates was increased from 2 to 20 (e.g. 4 mm vs. 11 mm). The difference between amplitude- and time-based sorting was up to 230% (e.g. 26 mm vs. 11 mm). Noise increases linearly with the number of gates in both amplitude and time-based sorting. Conclusions Amplitude-based sorting should be used to avoid large errors in estimating respiratory motion. In routine patients with up to 15 mm respiratory motion, 8 gates are enough. Noise increases linearly with the number of gates.