Reconstruction-Incorporated Respiratory Motion Correction in Clinical Simultaneous PET/MR Imaging for Oncology
Hadi Fayad1, Holger Schmidt2, Christian Wuerslin2
1INSERM, UMR1101, LaTIM, CHRU Morvan, Université de Bretagne Occidentale, Brest, France; and fayad@univ-brest.fr.
Unlabelled:
Simultaneous PET and MR imaging is a promising new technique allowing the fusion of functional (PET) and anatomic/functional (MR) information. In the thoracic-abdominal regions, respiratory motion is a major challenge leading to reduced quantitative and qualitative image accuracy. Correction methodologies include the use of gated frames that lead to low signal-to-noise ratio considering the associated low statistics. More advanced correction approaches, previously developed for PET/CT imaging, consist of either registering all the reconstructed gated frames to the reference frame or incorporating motion parameters into the iterative reconstruction process to produce a single motion-compensated PET image. The goal of this work was to compare these two—previously implemented in PET/CT—correction approaches within the context of PET/MR motion correction for oncology applications using clinical 4-dimensional PET/MR acquisitions. Two different correction approaches were evaluated comparing the incorporation of elastic transformations extracted from 4-dimensional MR imaging datasets during PET list-mode image reconstruction to a postreconstruction image-based approach.
Methods:
Eleven patient datasets acquired on a PET/MR system were used. T1-weighted 4D MR images were registered to the end-expiration image using a nonrigid B-spline registration algorithm to derive deformation matrices accounting for respiratory motion. The derived matrices were subsequently incorporated within a PET image reconstruction of the original emission list-mode data (reconstruction space [RS] method). The corrected images were compared with those produced by applying the deformation matrices in the image space (IS method) followed by summing the realigned gated frames, as well as with uncorrected motion-averaged images.
Results:
Both correction techniques led to significant improvement in accounting for respiratory motion artifacts when compared with uncorrected motion-averaged images. These improvements included signal-to-noise ratio (mean increase of 28.0% and 24.2% for the RS and IS methods, respectively), lesion size (reduction of 60.4% and 47.9%, respectively), lesion contrast (increase of 70.1% and 57.2%, respectively), and lesion position (changes of 60.9% and 46.7%, respectively).
Conclusion:
Our results demonstrate significant respiratory motion compensation using both methods, with superior results from a 4D PET RS approach.
Insights
Respiratory motion significantly impacts thoracic-abdominal PET/MR imaging accuracy. A 4D PET reconstruction space (RS) method effectively compensates for motion, outperforming image space (IS) methods for improved oncology imaging.
Area of Science:
- Medical Imaging
- Radiology
- Oncology
Background:
- Simultaneous PET and MR imaging offers fused functional and anatomical information.
- Respiratory motion in thoracic-abdominal PET/MR imaging degrades image quality and quantitative accuracy.
- Existing correction methods like gating have limitations, necessitating advanced approaches.
Purpose of the Study:
- To compare two advanced respiratory motion correction techniques for thoracic-abdominal PET/MR imaging in oncology.
- To evaluate a reconstruction space (RS) method against an image space (IS) method using clinical 4D PET/MR data.
Main Methods:
- Eleven patient PET/MR datasets were analyzed.
- Nonrigid B-spline registration of 4D MR images derived respiratory motion.
- Deformation matrices were incorporated into PET reconstruction (RS method) or applied post-reconstruction (IS method).
- Both methods were compared to uncorrected motion-averaged images.
Main Results:
- Both RS and IS methods significantly improved motion artifact correction compared to uncorrected images.
- RS and IS methods showed mean increases in signal-to-noise ratio of 28.0% and 24.2%, respectively.
- Lesion size, contrast, and position were significantly improved by both methods, with RS showing greater efficacy.
Conclusions:
- Both evaluated methods provide significant respiratory motion compensation in PET/MR imaging.
- The 4D PET reconstruction space (RS) approach demonstrated superior performance for motion compensation.
Related Concept Videos
01:30Radiological Investigation II: MRI and Ventilation Perfusion Scan
Magnetic Resonance Imaging (MRI) and Ventilation Perfusion Scans are two radiological investigations that offer detailed diagnostic images of the body, particularly lung structures.
MRI
MRI uses magnetic fields and radiofrequency signals to distinguish between normal and abnormal tissues. This technology provides a more detailed diagnostic image than CT scans, enabling it to characterize pulmonary nodules, stage bronchogenic carcinoma, and evaluate inflammatory activity in...
01:13Radiological Investigation III: Pulmonary Angiogram and PET Scan
Pulmonary Angiogram
A Pulmonary Angiogram is an invasive procedure involving injecting a contrast medium through a catheter threaded into the pulmonary artery or the right side of the heart to visualize the pulmonary vasculature. Computed Tomography (CT) scans have mainly replaced this...