Quiescent period respiratory gating for PET/CT

Abstract

Purpose: To minimize respiratory motion artifacts, this work proposes quiescent period gating ͑QPG͒ methods that extract PET data from the end-expiration quiescent period and form a single PET frame with reduced motion and improved signal-to-noise properties. Methods: Two QPG methods are proposed and evaluated. Histogram-based quiescent period gating ͑H-QPG͒ extracts a fraction of PET data determined by a window of the respiratory displacement signal histogram. Cycle-based quiescent period gating ͑C-QPG͒ extracts data with a respiratory displacement signal below a specified threshold of the maximum amplitude of each individual respiratory cycle. Performances of both QPG methods were compared to ungated and five-bin phase-gated images across 21 FDG-PET/CT patient data sets containing 31 thorax and abdomen lesions as well as with computer simulations driven by 1295 different patient respiratory traces. Image quality was evaluated in terms of the lesion SUV max and the fraction of counts included in each gate as a surrogate for image noise. Results: For all the gating methods, image noise artifactually increases SUV max when the fraction of counts included in each gate is less than 50%. While simulation data show that H-QPG is superior to C-QPG, the H-QPG and C-QPG methods lead to similar quantification-noise tradeoffs in patient data. Compared to ungated images, both QPG methods yield significantly higher lesion SUV max . Compared to five-bin phase gating, the QPG methods yield significantly larger fraction of counts with similar SUV max improvement. Both QPG methods result in increased lesion SUV max for patients whose lesions have longer quiescent periods. Conclusions: Compared to ungated and phase-gated images, the QPG methods lead to images with less motion blurring and an improved compromise between SUV max and fraction of counts. The QPG methods for respiratory motion compensation could effectively improve tumor quantification with minimal noise increase.

Determining the Minimal Required Radioactivity of 18F-FDG for Reliable Semiquantification in PET/CT Imaging: A Phantom Study

“…Overestimation of SUV max has been reported from noisier imaging using only a small portion of total counts in a respiration-gated study (20). However, overestimation of SUV avg may also be explained by factors other than noise buildup alone.…”

Application of Partial Volume Effect Correction and 4D PET in the Quantification of FDG Avid Lung Lesions

“…4D PET/CT reduces motion artifacts at the cost of decreasing signal-to-noise ratio (SNR), since during PET acquisition, non-gated images use all detected counts, while each of the phase gating bins contains only a fraction of the total counts [7]. To achieve similar image SNR as that of the non-gated image, one can increase the acquisition time, which is not desirable in the current clinical practice [7,34], and this commonly results in increased radiation exposure from CT imaging [35], particularly for gated PET/CT protocols that utilize a phase-correlated 4D CT for attenuation correction. Another option is to use direct 4D reconstruction with an organ motion model …”

“…Various methods such as shallow breathing, breathholding, and respiration synchronized techniques have been employed to reduce respiratory motion artifacts during PET acquisition [5][6][7]. One of the most commonly used techniques is respiratory gating, which consists in dividing a PET dataset into distinct phases of the respiratory cycle [8,9].…”

The effect of breathing irregularities on quantitative accuracy of respiratory gated PET/CT

“…The choice of the number of 4D phase bins can affect the noise level and hence the SUV max . Increasing the number of gates improves motion separation but biases tumor SUV max upward 27 offsetting the drop in SUV arising from decreased motion blurring. This is evidenced by the larger interbin SUV standard deviations between the 4 bin and 8 bin PET results.…”