Free-breathing Cardiac MR Imaging: Study of Implications of Respiratory Motion—Initial Results

Nehrke, Kay; Börnert, Peter; Manke, Dirk; Böck, J. C.

doi:10.1148/radiol.2203010132

Cited by 133 publications

(137 citation statements)

References 11 publications

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“…The main reason for this, of course, is that the motion of the heart with respiration is complex, and in addition to a simple linear translation it also undergoes twisting and rotation (16,17), with differences observed between inspiratory and expiratory phases (18). In addi- tion to a possible breakdown of the linear model, using slice-following over a wide range of diaphragmatic motion results in ghosting from structures within the image field of view that do not move with the structures being followed.…”

Section: Discussionmentioning

confidence: 99%

Coronary artery motion with the respiratory cycle during breath‐holding and free‐breathing: Implications for slice‐followed coronary artery imaging

Keegan¹,

Gatehouse²,

Yang

et al. 2002

Magnetic Resonance in Med

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The displacement of the right coronary artery (RCA) origin with respiratory position was determined relative to the dome of the right hemidiaphragm in three orthogonal directions in eight healthy subjects. Both multiple breath-hold and free-breathing acquisitions were used, and motion correction factors for slicefollowing applications were determined. The correction factors for all three directions showed considerable intersubject variability. The mean superior-inferior factor was slightly less in free-breathing than in breath-holding (0.26 vs. 0.29, P ‫؍‬ ns), and much less than the fixed value of 0.6 frequently implemented with slice-following. The anterior-posterior correction factors were uniformly low in free-breathing, and significantly less than those obtained from breath-holding (0.04 vs. 0.14, P < .05), while the mean left-right correction factors were approximately 0.1 for both. It is concluded that subject variability in correction factors, together with within-subject differences between breath-holding and free-breathing, is such that slice-following should be performed with subject-specific factors determined from free-breathing acquisitions. Key words: respiratory motion; slice-following; coronary artery; breath-holding; free-breathing Navigator-echo controlled free-breathing coronary artery studies (1) typically use a navigator positioned through the dome of the right hemidiaphragm, and an acceptance window of 5 mm to give a reasonable compromise between scan efficiency and image quality. However, during prolonged studies drifting of the respiratory pattern leads to a corresponding fall in efficiency (2), resulting in registration errors between scans and a frequent need to reposition the acceptance window. Real-time slice-following (3) has the potential to increase the scan efficiency and reduce the sensitivity to respiratory drift by allowing the implementation of a larger navigator acceptance window.The efficacy of real-time slice-following is critically dependent on the accuracy with which the motion of the heart can be predicted from the navigator echo data. In 1995, Wang and colleagues (4) used multiple 2D breathhold acquisitions to show a linear relationship between the superior-inferior (SI) motion of the heart and that of the diaphragm in healthy volunteers. In this subject group, the mean correction factor relating the SI motion of the right coronary artery (RCA) origin to that of the diaphragm was 0.57 (Ϯ0.26), and the anterior-posterior (AP) motion was approximately 20% of that in the SI direction (or 12% of that of the diaphragm). Some implementations of slicefollowing consequently use a fixed SI correction factor of 0.6, with or without a fixed AP factor of 0.12 (5,6). This approach has been shown to improve the quality of images acquired with 5-mm and 7-mm navigator acceptance windows, but has failed to produce good quality images when the acceptance window is increased to cover the entire range of respiratory positions (3). This may be due to a failure of the linear model, or to in...

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Section: Discussionmentioning

confidence: 99%

Coronary artery motion with the respiratory cycle during breath‐holding and free‐breathing: Implications for slice‐followed coronary artery imaging

Keegan¹,

Gatehouse²,

Yang

et al. 2002

Magnetic Resonance in Med

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“…T . Essentially, this introduces information on the slope of the respiratory curve (upslope/down-slope) into the model, which may be used to account for hysteretic effects (11) or delays between the navigator and image data acquisitions (12).…”

Section: Multiple Navigatorsmentioning

confidence: 99%

“…Thus Eq. [11] may be reduced to the linear model represented in Eq. [10] by simply adding the square of the corresponding navigator measurement as an additional element to the navigator vector, which results in an extended navigator vector…”

Section: Multiple Navigatorsmentioning

confidence: 99%

Prospective correction of affine motion for arbitrary MR sequences on a clinical scanner

Nehrke

Börnert

2005

Magnetic Resonance in Med

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The concept of prospective 3D affine motion correction was generalized, based on the Bloch equations, for signal excitation and sampling using arbitrary MR sequences. The technique was implemented on a clinical MRI scanner for Cartesian, radial, and spiral imaging sequences, as well as for 2D spatially selective RF excitation pulses. A patient-specific motion model steered by real-time navigators was employed to account for the additional degrees of freedom provided by the affine motion model. Different navigator concepts (multiple spatial and temporal navigators, quadratic navigators and other motion sensors) were investigated, with the aim of improving the correlation between navigator information and the motion model. Many MR imaging (MRI) and spectroscopy (MRS) applications suffer from motion artifacts caused by, e.g., respiratory and cardiac motion. Currently employed real-time gating techniques, such as EKG triggering and navigatorbased respiratory gating (1), reduce motion artifacts considerably but result in a strong increase in scan time. Hence, motion-correction techniques, which allow the acquisition of MR data in the presence of motion, are highly desirable. Slice-tracking approaches based on respiratory navigators have been shown to improve image quality in coronary MRA (2). However, due to the simplicity of the underlying 1D translatory motion model, only small gating windows (typically 5 mm) can be applied (3). Recently a patient-specific calibration approach was introduced for coronary MRA that allows the prediction of affine transformation parameters, including 3D translation, rotation, scale, and shear motion, from navigator measurements (4). In addition, a prospective correction of affine motion was proposed. However, the technical complexity of such an approach limited the implementation to prospective correction of 3D translation and 1D expansion for Cartesian imaging sequences. Furthermore, additional offline processing was required, which challenged the practical feasibility of the method in a clinical workflow.In the current work, prospective motion correction is discussed in the framework of the Bloch equations, which conceptually overcomes the restriction to Cartesian imaging sequences. Thus, the approach is generalized to signal excitation and sampling for arbitrary MRI sequences, such as multidimensional excitation pulses and non-Cartesian imaging sequences. Following the theoretical treatment, the technique is fully implemented on a clinical scanner in a sequence-independent manner, which enables the employment of a full 3D affine transformation for all available pulse and imaging sequences, including Cartesian, radial, and spiral scanning, as well as 2D excitation pulses. The results of phantom experiments are presented that prove the technical feasibility of the approach, whereas initial in vivo results demonstrate the potential for coronary MRA and abdominal imaging. THEORYThe principles of affine motion correction may be derived directly from the Bloch equations. The Bloch equati...

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“…21 Recently pulmonary hysteresis motion has been studied by nuclear imaging, 19 but this is a relatively recent development, which previously had been investigated mainly by way of cardiac MRI. 22,23 While the intent of the current article is to present a method to account for pulmonary effects on SPECT studies that are used to assess LV asynchrony, 1 a tantalizing prospect is that dual-gating methods now being developed may offer the prospect of investigating disease processes involving both aberrant pulmonary and cardiac function. 24 Echocardiography has been used to investigate cases of pulmonary edema induced by RV pacing, 25 and cardiac MRI has been used to detect inter-ventricular asynchrony resulting from primary arterial hypertension.…”

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confidence: 99%

Advances in dual respiratory and ECG-gated SPECT imaging

Nichols

Tosh

2018

Journal of Nuclear Cardiology

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In the current issue of Journal of Nuclear Cardiology, Kortelainen et al report that a new method of acquiring dual respiratory and ECG-gated SPECT myocardial perfusion data reduces artifacts due to respiratory motion while leaving asynchrony measurements derived from the data unaltered. 1 As the improvements reported were modest and only observed in a subset of subjects, a relevant question to ask is whether the additional equipment needed and patient preparation logistics would significantly improve patient outcomes. Is pulmonary motion actually a significant problem in nuclear cardiology imaging, requiring a solution?There is a long history of exploring data acquisition and processing methods to detect and compensate for the repositioning of organ systems due to breathing in scintigraphic imaging, notably for PET studies to improve the detection of tumors involved in lung cancer. 2 In the realm of cardiac imaging, it was recognized as early as 1989 that changes in breathing patterns over time could degrade Tl-201 SPECT myocardial image quality if data acquisition was initiated too early following treadmill exercise, 3 the remedy for which was to delay the start of imaging. Even with this change in technique, myocardial motion due to normal breathing patterns has been shown to degrade image quality and affect quantified myocardial perfusion. 4 In 2009, several papers appeared documenting the effect of respiratory motion on SPECT perfusion assessment and proposing solutions. [5][6][7] Now, in conjunction with protocols involving imaging the heart while it is in a stressed state, corrections for breathing motion have been shown to improve accuracy not only of relative myocardial perfusion evaluation but also of absolute myocardial blood flow quantitative measurements as derived from Rb-82 PET data. 8 There are advantages to ECG-gating both rest and stress PET data, and newer rest/stress SPECT protocols are being implemented such that the heart is in a genuinely different physiologic state during stress SPECT acquisition, 9 raising the prospect that it may become important to detect and correct for changes in breathing patterns induced by stress.Initially, the main focus of Tl-201 and Tc-99m-sestamibi SPECT imaging was relative myocardial perfusion assessment, but with ECG-gating, additional parameters can be measured as well, including LV ejection fraction, 10 volumes, wall thickening by way of partial volume effects, 11 and regional asynchrony. 12 Multiple different approaches are possible in acquiring SPECT data with ECG-gating, and effects of gating errors and arrhythmias on quantified parameters have been reported. 13 By the same token, several different approaches to handle cardiac displacement to account for breathing motion are possible. With these new approaches to incorporate information regarding pulmonary motion, attention now has broadened to assessing the effects of pulmonary gating errors and breathing motion not only on myocardial perfusion but on the other parameters as well. This account by Kort...

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Free-breathing Cardiac MR Imaging: Study of Implications of Respiratory Motion—Initial Results

Cited by 133 publications

References 11 publications

Coronary artery motion with the respiratory cycle during breath‐holding and free‐breathing: Implications for slice‐followed coronary artery imaging

Coronary artery motion with the respiratory cycle during breath‐holding and free‐breathing: Implications for slice‐followed coronary artery imaging

Prospective correction of affine motion for arbitrary MR sequences on a clinical scanner

Advances in dual respiratory and ECG-gated SPECT imaging

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