Impact of respiratory motion correction on lesion visibility and quantification in thoracic PET/MR imaging

Abstract

The impact of a method for MR-based respiratory motion correction of PET data on lesion visibility and quantification in patients with oncologic findings in the lung was evaluated. Twenty patients with one or more lesions in the lung were included. Hybrid imaging was performed on an integrated PET/MR system using 18 F-FDG as radiotracer. The standard thoracic imaging protocol was extended by a free-breathing self-gated acquisition of MR data for motion modelling. PET data was acquired simultaneously in list-mode for 5-10 mins. One experienced radiologist and one experienced nuclear medicine specialist evaluated and compared the post-processed data in consensus regarding lesion visibility (scores 1-4, 4 being best), image noise levels (scores 1-3, 3 being lowest noise), SUVmean and SUVmax. Motion-corrected (MoCo) images were additionally compared with gated images. Nonmotion-corrected free-breathing data served as standard of reference in this study. Motion correction generally improved lesion visibility (3.19 ± 0.63) and noise ratings (2.95 ± 0.22) compared to uncorrected (2.81 ± 0.66 and 2.95 ± 0.22, respectively) or gated PET data (2.47 ± 0.93 and 1.30 ± 0.47, respectively). Furthermore, SUVs (mean and max) were compared for all methods to estimate their respective impact on the quantification. Deviations of SUVmax were smallest between the uncorrected and the MoCo lesion data (average increase of 9.1% of MoCo SUVs), while SUVmean agreed best for gated and MoCo reconstructions (MoCo SUVs increased by 1.2%). The studied method for MR-based respiratory motion correction of PET data combines increased lesion sharpness and improved lesion activity quantification with high signal-to-noise ratio in a clinical setting. In particular, the detection of small lesions in moving organs such as the lung and liver may thus be facilitated. These advantages justify the extension of the PET/MR imaging protocol by 5-10 minutes for motion correction.

Experimental evaluation of four-dimensional Magnetic Resonance Imaging for radiotherapy planning of lung cancer

“…With the introduction of motion correction averaging to further improve the imaging performance of MRI through post processing [23,24], as well as superior soft tissue contrast compared to CT, the radial VIBE sequence should be considered for further investigation in patient studies.…”

Multiparametric Oncologic Hybrid Imaging: Machine Learning Challenges and Opportunities

“…Besides attenuation correction, physiological motion can have a severe impact on the obtained image quality. Motion correction with motion models derived from other imaging modalities or surrogate measures [39][40][41][42][43][44][45][46][47] can be integrated [48] to compensate for motion-induced blurring and aliasing in PET.…”

Synergistic motion compensation strategies for positron emission tomography when acquired simultaneously with magnetic resonance imaging

“…Another study reported that after motion correction, an additional lesion was identified in the liver [ 77 ]. More specifically in a recent investigation concentrated on patients with lung lesions, the readers scored lesions in the motion corrected images with 38% and 56% more confidence compared to the non-corrected images and gated images, respectively ( figure 4 ) [ 78 ].

Figure 3 [ 18 F]FDG PET-MRI study.

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“…Note the enhanced sharpness and signal-to-noise ratio of the hilar lesion in the motion corrected data in comparison to the other two methods, while the bone lesion in the region with less motion varies less between the uncorrected and motion compensated reconstructions (Reproduced from Gratz M, Ruhlmann V, Umutlu L, Fenchel M, Hong I, Quick HH (2020) Impact of respiratory motion correction on lesion visibility and quantification in thoracic PET/MRI imaging. PLoS ONE 15 , e0233209) [ 78 ]. (Online version in colour.)…”