Conference Paper

Pipeline for motion correction in dual gated PET

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

The aim of this work is to present an advanced motion correction pipeline for dual gating based on motion compensation. The pipeline is robust against noise and uses the whole statistic for the final image. We extend motion compensation by motion compensated reconstructions which allow a much finer dual gating for maximal reduction of motion artifacts. Further, mass-preserving motion estimation based on spline transformations is performed motion estimation.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

Article
Full-text available
Recent studies have suggested that 18F-NaF-PET enables visualization and quantification of plaque micro-calcification in the coronary tree. However, PET imaging of plaque calcification in the coronary arteries is challenging because of the respiratory and cardiac motion as well as partial volume effects. The objective of this work is to implement an image reconstruction framework, which incorporates compensation for respiratory as well as cardiac motion (MoCo) and partial volume correction (PVC), for cardiac 18F-NaF PET imaging in PET/CT. We evaluated the effect of MoCo and PVC on the quantification of vulnerable plaques in the coronary arteries. Realistic simulations (Biograph TPTV, Biograph mCT) and phantom acquisitions (Biograph mCT) were used for these evaluations. Different uptake values in the calcified plaques were evaluated in the simulations, while three "plaque-type" lesions of 36, 31 and 18 mm3 were included in the phantom experiments. After validation, the MoCo and PVC methods were applied in four pilot NaF-PET patient studies. In all cases, the MoCo-based image reconstruction was performed using the STIR software. The PVC was obtained from a local projection (LP) method, previously evaluated in preclinical and clinical PET. The results obtained show a significant increase of the measured lesion-to-background ratios (LBR) in the MoCo+PVC images. These ratios were further enhanced when using directly the tissue-activities from the LP method, making this approach more suitable for the quantitative evaluation of coronary plaques. When using the LP method on the MoCo images, LBR increased between 200% and 1119% in the simulated data, between 212% and 614% in the phantom experiments and between 46% and 373% in the plaques with positive uptake observed in the pilot patients. In conclusion, we have built and validated a STIR framework incorporating MoCo and PVC for 18F-NaF PET imaging of coronary plaques. First results indicate an improved quantification of plaque-type lesions.
Chapter
In the introduction of this book we have seen that PET image acquisition is susceptible to motion artifacts. The first step to overcome this problem is the separation of the measured data into different motion states via gating as described in Sect.?1.3. The next step is the estimation of motion between these gated reconstructions. This step is crucial as its accuracy highly influences the quality of the final motion corrected image.
Chapter
In the previous chapter we have seen tailored methods for the estimation of motion between gates representing different motion states. Based on this knowledge, we eliminate motion induced image artifacts in a subsequent correction step. In this chapter, we give an overview of strategies for motion correction.
Conference Paper
Full-text available
Positron Emission Tomography (PET) is a nuclear imaging technique of increasing importance e.g. in cardiovascular investigations. However, cardiac and respiratory motion of the patient degrade the image quality due to acquisition times in the order of minutes. Reconstructions without motion compensation are prone to spatial blurring and affected attenuation correction. These effects can be reduced by gating, motion correction and finally summation of the transformed images. This paper describes a new and systematic approach for the correction of both cardiac and respiratory motion. Key contribution is the splitting of the motion into respiratory and cardiac components, which are then corrected individually. For the considered gating scheme the number of registration problems is reduced by a factor of 3, which considerably simplifies the motion correction pipeline compared to previous approaches. The subproblems are stabilized by averaging cardiac gates for respiratory motion estimation and vice versa. The potential of the novel pipeline is evaluated in a group study on data of 21 human patients.
Article
Full-text available
Respiratory and cardiac motion leads to image degradation in positron emission tomography (PET) studies of the human heart. In this paper we present a novel approach to motion correction based on dual gating and mass-preserving hyperelastic image registration. Thereby, we account for intensity modulations caused by the highly nonrigid cardiac motion. This leads to accurate and realistic motion estimates which are quantitatively validated on software phantom data and carried over to clinically relevant data using a hardware phantom. For patient data, the proposed method is first evaluated in a high statistic (20 min scans) dual gating study of 21 patients. It is shown that the proposed approach properly corrects PET images for dual-cardiac as well as respiratory-motion. In a second study the list mode data of the same patients is cropped to a scan time reasonable for clinical practice (3 min). This low statistic study not only shows the clinical applicability of our method but also demonstrates its robustness against noise obtained by hyperelastic regularization.
Article
Full-text available
Gating methods acquiring biosignals (such as electrocardiography [ECG] and respiration) during PET enable one to reduce motion effects that potentially lead to image blurring and artifacts. This study evaluated different cardiac and respiratory gating methods: one based on ECG signals for cardiac gating and video signals for respiratory gating; 2 others based on measured inherent list mode events. Twenty-nine patients with coronary artery disease underwent a 20-min ECG-gated single-bed list mode PET scan of the heart. Of these, 17 were monitored by a video camera registering a marker on the patient's abdomen, thus capturing the respiratory motion for PET gating (video method). Additionally, respiratory and cardiac gating information was deduced without auxiliary measurements by dividing the list mode stream in 50-ms frames and then either determining the number of coincidences (sensitivity method) or computing the axial center of mass and SD of the measured counting rates in the same frames (center-of-mass method). The gated datasets (respiratory and cardiac gating) were reconstructed without attenuation correction. Measured wall thicknesses, maximum displacement of the left ventricular wall, and ejection fraction served as measures of the exactness of gating. All methods successfully captured respiratory motion and significantly decreased motion-induced blurring in the gated images. The center-of-mass method resulted in significantly larger left ventricular wall displacements than did the sensitivity method (P < 0.02); other differences were nonsignificant. List mode-based cardiac gating was found to work well for patients with high (18)F-FDG uptake when the center-of-mass method was used, leading to an ejection fraction correlation coefficient of r = 0.95 as compared with ECG-based gating. However, the sensitivity method did not always result in valid cardiac gating information, even in patients with high (18)F-FDG uptake. Our study demonstrated that valid gating signals during PET scans cannot be obtained only by tracking the external motion or applying an ECG but also by simply analyzing the PET list mode stream on a frame-by-frame basis.
Article
Full-text available
Respiratory motion in emission tomography leads to reduced image quality. Developed correction methodology has been concentrating on the use of respiratory synchronized acquisitions leading to gated frames. Such frames, however, are of low signal-to-noise ratio as a result of containing reduced statistics. In this work, we describe the implementation of an elastic transformation within a list-mode-based reconstruction for the correction of respiratory motion over the thorax, allowing the use of all data available throughout a respiratory motion average acquisition. The developed algorithm was evaluated using datasets of the NCAT phantom generated at different points throughout the respiratory cycle. List-mode-data-based PET-simulated frames were subsequently produced by combining the NCAT datasets with Monte Carlo simulation. A non-rigid registration algorithm based on B-spline basis functions was employed to derive transformation parameters accounting for the respiratory motion using the NCAT dynamic CT images. The displacement matrices derived were subsequently applied during the image reconstruction of the original emission list mode data. Two different implementations for the incorporation of the elastic transformations within the one-pass list mode EM (OPL-EM) algorithm were developed and evaluated. The corrected images were compared with those produced using an affine transformation of list mode data prior to reconstruction, as well as with uncorrected respiratory motion average images. Results demonstrate that although both correction techniques considered lead to significant improvements in accounting for respiratory motion artefacts in the lung fields, the elastic-transformation-based correction leads to a more uniform improvement across the lungs for different lesion sizes and locations.
Article
We present a flexible image reconstruction framework for emission tomography data called EMRECON. The software includes multiple expectation maximization based reconstruction algorithms as well as support for several scanner geometries. In order to implement novel reconstruction techniques (e.g. TV-based regularization or combined reconstruction and motion correction) or scanner models, full access to every stage of the reconstruction pipeline is vital. EMrecon is fully open and well-documented, thus permits testing without the need to care about data formats or standard reconstruction and data correction algorithms. Due to the GATE-like syntax new scanner geometries, including an exact definition of each single crystal, can be added easily. The parallel (multi-core) C implementation was successfully tested on several Linux distributions. This makes EMRECON a useful tool for the development of new reconstruction algorithms and also serves as a platform for testing different scanner geometries.
Article
Positron emission tomography (PET) is a molecular imaging technique which provides important functional information about the human body. However, thoracic PET images are often substantially degraded by respiratory motion, which adversely impacts on subsequent diagnosis. In this paper, a motion correction and attenuation correction method is proposed to correct for motion in respiratory gated PET images and to yield an accurate distribution of the radioactivity concentration. Experimental results show that this method can effectively correct for motion and improve PET image quality. The method is able to provide improved diagnostic information without increasing the acquisition time or the radiation burden.