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      Accelerometer-Based Method for Extracting Respiratory and Cardiac Gating Information for Dual Gating during Nuclear Medicine Imaging

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          Abstract

          Both respiratory and cardiac motions reduce the quality and consistency of medical imaging specifically in nuclear medicine imaging. Motion artifacts can be eliminated by gating the image acquisition based on the respiratory phase and cardiac contractions throughout the medical imaging procedure. Electrocardiography (ECG), 3-axis accelerometer, and respiration belt data were processed and analyzed from ten healthy volunteers. Seismocardiography (SCG) is a noninvasive accelerometer-based method that measures accelerations caused by respiration and myocardial movements. This study was conducted to investigate the feasibility of the accelerometer-based method in dual gating technique. The SCG provides accelerometer-derived respiratory (ADR) data and accurate information about quiescent phases within the cardiac cycle. The correct information about the status of ventricles and atria helps us to create an improved estimate for quiescent phases within a cardiac cycle. The correlation of ADR signals with the reference respiration belt was investigated using Pearson correlation. High linear correlation was observed between accelerometer-based measurement and reference measurement methods (ECG and Respiration belt). Above all, due to the simplicity of the proposed method, the technique has high potential to be applied in dual gating in clinical cardiac positron emission tomography (PET) to obtain motion-free images in the future.

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          Most cited references35

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          Magnetic resonance-based motion correction for positron emission tomography imaging.

          Positron emission tomography (PET) image quality is limited by patient motion. Emission data are blurred owing to cardiac and/or respiratory motion. Although spatial resolution is 4 mm for standard clinical whole-body PET scanners, the effective resolution can be as low as 1 cm owing to motion. Additionally, the deformation of attenuation medium causes image artifacts. Previously, gating has been used to "freeze" the motion, but led to significantly increased noise level. Simultaneous PET/magnetic resonance (MR) modality offers a new way to perform PET motion correction. MR can be used to measure 3-dimensional motion fields, which can then be incorporated into the iterative PET reconstruction to obtain motion-corrected PET images. In this report, we present MR imaging techniques to acquire dynamic images, a nonrigid image registration algorithm to extract motion fields from acquired MR images, and a PET reconstruction algorithm with motion correction. We also present results from both phantom and in vivo animal PET/MR studies. We demonstrate that MR-based PET motion correction using simultaneous PET/MR improves image quality and lesion detectability compared with gating and no motion correction. Copyright © 2013 Elsevier Inc. All rights reserved.
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            The CT motion quantitation of lung lesions and its impact on PET-measured SUVs.

            We previously reported that respiratory motion is a major source of error in quantitation of lesion activity using combined PET/CT units. CT acquisition of the lesion occurs in seconds, rather than the 4-6 min required for PET emission scans. Therefore, an incongruent lesion position during CT acquisition will bias activity estimates using PET. In this study, we systematically analyzed the range of activity concentration changes, hence SUV, for lung lesions. Five lung cancer patients were scanned with PET/CT. In CT, data were acquired in correlation with the real-time positioning. CT images were acquired, in cine mode, at 0.45-s intervals for slightly longer (1 s) than a full respiratory cycle at each couch position. Other scanning parameters were a 0.5-s gantry rotation, 140 kVp, 175 mA, 10-mm couch increments, and a 2.5-mm slice thickness. PET data were acquired after intravenous injection of about 444-555 MBq of (18)F-FDG with a 1-h uptake period. The scanning time was 3 min per bed position for PET. Regularity in breathing was assisted by audio coaching. A commercial software program was then used to sort the acquired CT images into 10 phases, with 0% corresponding to end of inspiration (EI) and 50% corresponding to end of expiration (EE). Using the respiration-correlated CT data, images were rebinned to match the PET slice locations and thickness. We analyzed 8 lesions from 5 patients. Reconstructed PET emission data showed up to a 24% variation in the lesion maximum standardized uptake values (SUVs) between EI and EE phases. Examination of all the phases showed an SUV variation of up to 30%. Also, in some cases the lesion showed up to a 9-mm shift in location and up to a 21% reduction in size when measured from PET during the EI phase, compared with during the EE phase. Using respiration-correlated CT for attenuation correction, we were able to quantitate the fluctuations in PET SUVs. Because those changes may lead to estimates of lower SUVs, the respiratory phase during CT transmission scanning needs to be measured or lung motion has to be regulated for imaging lung cancer in routine clinical practice.
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              Wearable seismocardiography.

              Seismocardiogram (SCG) is the recording of body vibrations induced by the heart beat. SCG contains information on cardiac mechanics, in particular heart sounds and cardiac output. In this paper we present a new wearable device for SCG recordings during long term monitorings, and the results of a validation test in 4 subjects. The system is based on the integration of the MagIC smart shirt (i.e., a textile-based wearable system for the assessment of ECG and respiratory movements), and an external triaxial MEMS accelerometer positioned on the left clavicle. SCG was estimated as the average of accelerations occurred in each heart beat. The SCG components due to the valve closure and to recoil forces following the heart contraction (ballistocardiogram) were extracted by high-pass (>18 Hz) and band-pass (0.6-20 Hz) filters respectively. Then the difference between the I and J waves of the ballistocardiogram (|I-J| index, possibly related to the cardiac output) was identified by an ad-hoc procedure and compared with the model flow indirect estimation of cardiac output. Validation on 4 volunteers showed that: 1) our wearable system provides statistically consistent estimates of both heart-sound related vibrations and recoil movements; 2) reliable estimates of the |I-J| index can be obtained by considering about 1 minute of SCG recording in stationary conditions; and 3) changes of the |I-J| index during exercise correlate well with changes of cardiac output estimated by the model flow.
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                Author and article information

                Journal
                Int J Biomed Imaging
                Int J Biomed Imaging
                IJBI
                International Journal of Biomedical Imaging
                Hindawi Publishing Corporation
                1687-4188
                1687-4196
                2014
                10 July 2014
                : 2014
                : 690124
                Affiliations
                1Technology Research Center, Brahea Center, University of Turku, 20520 Turku, Finland
                2Department of Clinical Physiology and Nuclear Medicine, Faculty of Medicine, University of Turku, 20520 Turku, Finland
                Author notes
                *Mojtaba Jafari Tadi: mojjaf@ 123456utu.fi

                Academic Editor: Jyh-Cheng Chen

                Author information
                http://orcid.org/0000-0002-4085-4057
                http://orcid.org/0000-0003-3792-8999
                Article
                10.1155/2014/690124
                4120481
                bdea0f35-5e67-4730-919d-556bf2ab86f1
                Copyright © 2014 Mojtaba Jafari Tadi et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 21 February 2014
                : 18 April 2014
                Categories
                Research Article

                Radiology & Imaging
                Radiology & Imaging

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