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NO-HYPE: a novel hydrodynamic phantom for the evaluation of MRI flow measurements. Med Biol Eng Comput 2021; 59:1889-1899. [PMID: 34365590 PMCID: PMC8382656 DOI: 10.1007/s11517-021-02390-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 06/07/2021] [Indexed: 10/24/2022]
Abstract
Accurate and reproducible measurement of blood flow profile is very important in many clinical investigations for diagnosing cardiovascular disorders. Given that many factors could affect human circulation, and several parameters must be set to properly evaluate blood flows with phase-contrast techniques, we developed an MRI-compatible hydrodynamic phantom to simulate different physiological blood flows. The phantom included a programmable hydraulic pump connected to a series of pipes immersed in a solution mimicking human soft tissues, with a blood-mimicking fluid flowing in the pipes. The pump is able to shape and control the flow by driving a piston through a dedicated software. Periodic waveforms are used as input to the pump to move the fluid into the pipes, with synchronization of the MRI sequences to the flow waveforms. A dedicated software is used to extract and analyze flow data from magnitude and phase images. The match between the nominal and the measured flows was assessed, and the scope of phantom variables useful for a reliable calibration of an MRI system was accordingly defined. Results showed that the NO-HYPE phantom is a valuable tool for the assessment of MRI scanners and sequence design for the MR evaluation of blood flows. Overview of the NOvel HYdrodynamic Phantom for the Evaluation of MRI flow measurements (NO-HYPE). Left: internal of the CompuFlow 1000 MR pump unit. Right: Setting of the NO-HYPE before a MRI acquisition session. Soft tissue mimicking material is hosted in the central part of the phantom (light blue chamber). Glass pipes pass through the chamber carrying the blood mimicking fluid.
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Tayler AB, Holland DJ, Sederman AJ, Gladden LF. Time resolved velocity measurements of unsteady systems using spiral imaging. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 211:1-10. [PMID: 21514194 DOI: 10.1016/j.jmr.2011.03.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 03/10/2011] [Accepted: 03/18/2011] [Indexed: 05/30/2023]
Abstract
Spiral imaging has been assessed as a tool for the measurement of spatially and temporally resolved velocity information for unsteady flow systems. Using experiments and simulated acquisitions, we have quantified the flow artefacts associated with spiral imaging. In particular, we found that despite the adverse effect of in-plane flow on the point spread function, for many physical systems the extent of blurring associated with spiral imaging is marginal because flows represented by high spatial Fourier coefficients, which would be those most affected by the distortion of the point spread function, exist at the physical boundaries of the flow and are therefore associated with much smaller velocities than are characteristic of the bulk flow. The necessity for a flow imaging technique which is robust to the accrual of velocity proportionate phase during imaging was demonstrated in an experimental comparison of spiral imaging and echo-planar imaging (EPI) applied to turbulent flow in a pipe. While the measurements acquired using EPI accrued substantial velocity proportionate phase, those acquired using spiral imaging were not significantly affected. High temporal velocity measurements using spiral imaging were demonstrated on turbulent flow in a pipe (image acquisition time 5.4 ms; 91 frames per second), which enabled the transient behaviour of wall instabilities to be captured. Additionally, the technique was applied to a multiphase flow system, where the wakes behind single rising bubbles were characterised. Spiral imaging thus seems an auspicious basis for the measurement of velocity fields for unsteady flow systems.
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Affiliation(s)
- Alexander B Tayler
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
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Steeden JA, Atkinson D, Taylor AM, Muthurangu V. Split-acquisition real-time CINE phase-contrast MR flow measurements. Magn Reson Med 2011; 64:1664-70. [PMID: 20939086 DOI: 10.1002/mrm.22615] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The temporal and spatial resolution of real-time phase-contrast magnetic resonance (PCMR) is restricted by the need to acquire two interleaved phase images. In this article, we propose a split-acquisition real-time CINE PCMR technique, where the acquisition of flow-encoded and flow-compensated data is divided into separate blocks. By comparing magnitude images, automatic matching of data in cardio-respiratory space allows subtraction of background phase offsets. Thus, the data is acquired in real-time but with phase correction originating from a different heart beat. This effectively doubles the frame rate, allowing either higher temporal or spatial resolution. Two split-acquisition sequences were tested: one with high-temporal resolution and one with high-spatial resolution. Both sequences showed excellent agreement in stroke volumes in 20 adults when validated against cardiac-gated PCMR and interleaved real-time PCMR (cardiac gated: 95.2 ± 20.0 mL, interleaved real-time: 96.2 ± 20.7 mL, high-temporal resolution: 95.6 ± 20.1 mL, high-spatial resolution: 95.5 ± 20.4 mL). In six children, the high-spatial resolution sequence provided more accurate flow measurements than interleaved real-time PCMR, when compared with cardiac-gated PCMR (cardiac gated: 20.6 ± 7.6 mL, interleaved real-time: 24.3 ± 9.2 mL, high-spatial resolution: 20.8 ± 7.8 mL), due to the increased spatial resolution. The matching technique is shown to be accurate (truth: 94.6 ± 21.8, split-acquisition: 95.0 ± 21.9 mL) and quantitative image quality (signal-to-noise ratio, velocity-to-noise ratio and edge sharpness) is acceptable.
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Affiliation(s)
- Jennifer A Steeden
- Centre for Medical Image Computing, UCL Department of Medical Physics and Bioengineering, London, United Kingdom
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Pohmann R, Budde J, Auerbach EJ, Adriany G, Uğurbil K. Theoretical and experimental evaluation of continuous arterial spin labeling techniques. Magn Reson Med 2010; 63:438-46. [PMID: 20024952 DOI: 10.1002/mrm.22243] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Continuous arterial spin labeling is known to be the most sensitive arterial spin labeling technique. To avoid magnetization transfer effects and to overcome hardware limitations, several sequences have been proposed that adiabatically label the inflowing blood. Four of these methods are examined with respect to their sensitivity both theoretically by Bloch equation simulations and experimentally. All sequences were optimized carefully by adjusting their measurement parameters based exclusively on the results of simulations. Perfusion measurements on the human brain obtained at 3 T result in excellent images from all techniques, while differences in sensitivity are similar to those expected from the simulations.
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Affiliation(s)
- Rolf Pohmann
- Max Planck Institute for Biological Cybernetics, Magnetic Resonance Center, Tübingen, Germany.
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Nielsen JF, Nayak KS. Referenceless phase velocity mapping using balanced SSFP. Magn Reson Med 2009; 61:1096-102. [DOI: 10.1002/mrm.21884] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Zuo J, Walsh EG, Twieg DB. Flow SS-PARSE: a new method for rapid imaging and mapping of blood flow velocity. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2006:530-3. [PMID: 17271730 DOI: 10.1109/iembs.2004.1403211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
A new method for flow velocity mapping of blood is presented here. Instead of the conventional approach of employing two images (velocity sensitive and control) to generate velocity information, in the new method the velocity is determined directly by solving an inverse problem. This technique is an application of single shot - parameter assessment by retrieval from signal encoding (SS-PARSE). Simulations have been done to demonstrate the feasibility of the method. The velocity measurement range of the prototype version is from -50cm/s to 50cm/s, roughly appropriate for future applications in blood flow measurement of carotid arteries.
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Affiliation(s)
- J Zuo
- Dept. of Biomedical Eng., Alabama Univ., Birmingham, AL, USA
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Zuo J, Bolding M, Twieg DB. Validation of V-SS-PARSE for single-shot flow measurement. Magn Reson Imaging 2006; 25:335-40. [PMID: 17371722 PMCID: PMC2034512 DOI: 10.1016/j.mri.2006.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Accepted: 09/21/2006] [Indexed: 11/17/2022]
Abstract
As a variant of Single-Shot Parameter Assessment by Retrieval from Signal Encoding, Velocity Single-Shot Parameter Assessment by Retrieval from Signal Encoding, a single-shot imaging method, has been developed to realize fast and straightforward flow quantification by solving inverse problems. A robust signal model, including its local magnetization and its phase evolution during signaling (resulting in a more precise representation of the sampled signal) is described here. Magnitude, velocity, relaxation rate and frequency information can be retrieved without any extra reference image acquisitions, as demonstrated by phantom studies. In the presence of stationary background, retrieved magnitude maps and velocity maps show results comparable to those obtained by phase-contrast methods (r>.99, P=.005), even with brief single-shot 70-ms acquisition.
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Affiliation(s)
- Jin Zuo
- Musculoskeletal and Quantitative Imaging Research (MQIR), Department of Radiology, University of California-San Francisco, San Francisco, CA 94158-2520, USA.
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Zuo J, Walsh EG, Deutsch G, Twieg DB. Rapid mapping of flow velocity using a new PARSE method. Magn Reson Med 2006; 55:147-52. [PMID: 16315204 DOI: 10.1002/mrm.20750] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A new method for flow velocity mapping is presented here. Instead of the conventional approach of employing two images (velocity sensitive and control) to generate velocity information, in the new method one determines the velocity directly from a single-shot acquisition by solving an inverse problem. This technique is a variant of single-shot parameter assessment by retrieval from signal encoding (SS-PARSE). The results of simulation and phantom studies show strong agreement with the actual velocities. The prototype method can measure velocities in the range of -50 to 50 cm/s, which is roughly appropriate for future applications in dynamic blood flow measurement in carotid arteries.
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Affiliation(s)
- Jin Zuo
- Department of Biomedical Engineering, University of Alabama at Birmingham, USA.
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Baltes C, Kozerke S, Hansen MS, Pruessmann KP, Tsao J, Boesiger P. Accelerating cine phase-contrast flow measurements using k-t BLAST and k-t SENSE. Magn Reson Med 2006; 54:1430-8. [PMID: 16276492 DOI: 10.1002/mrm.20730] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Conventional phase-contrast velocity mapping in the ascending aorta was combined with k-t BLAST and k-t SENSE. Up to 5.3-fold net acceleration was achieved, enabling single breath-hold acquisitions. A standard phase-contrast (PC) sequence with interleaved acquisition of the velocity-encoded segments was modified to collect data in 2 stages, a high-resolution under sampled and a low-resolution fully sampled training stage. In addition, a modification of the k-t reconstruction strategy was tested. This strategy, denoted as "plug-in," incorporates data acquired in the training stage into the final reconstruction for improved data consistency, similar to conventional keyhole. "k-t SENSE plug-in" was found to provide best image quality and most accurate flow quantification. For this strategy, at least 10 training profiles are required to yield accurate stroke volumes (relative deviation <5%) and good image quality. In vivo 2D cine velocity mapping was performed in 6 healthy volunteers with 30-32 cardiac phases (spatial resolution 1.3 x 1.3 x 8-10 mm(3), temporal resolution of 18-38 ms), yielding relative stroke volumes of 106 +/- 18% (mean +/- 2*SD) and 112 +/- 15% for 3.8 x and 5.3 x net accelerations, respectively. In summary, k-t BLAST and k-t SENSE are promising approaches that permit significant scan-time reduction in PC velocity mapping, thus making high-resolution breath-held flow quantification possible.
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Affiliation(s)
- Christof Baltes
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
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Lotz J, Meier C, Leppert A, Galanski M. Cardiovascular flow measurement with phase-contrast MR imaging: basic facts and implementation. Radiographics 2002; 22:651-71. [PMID: 12006694 DOI: 10.1148/radiographics.22.3.g02ma11651] [Citation(s) in RCA: 439] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Phase-contrast magnetic resonance (MR) imaging is a well-known but undervalued method of obtaining quantitative information on blood flow. Applications of this technique in cardiovascular MR imaging are expanding. According to the sequences available, phase-contrast measurement can be performed in a breath hold or during normal respiration. Prospective as well as retrospective gating techniques can be used. Common errors in phase-contrast imaging include mismatched encoding velocity, deviation of the imaging plane, inadequate temporal resolution, inadequate spatial resolution, accelerated flow and spatial misregistration, and phase offset errors. Flow measurements are most precise if the imaging plane is perpendicular to the vessel of interest and flow encoding is set to through-plane flow. The sequence should be repeated at least once, with a high encoding velocity used initially. If peak velocity has to be estimated, flow measurement is repeated with an adapted encoding velocity. The overall error of a phase-contrast flow measurement comprises errors during prescription as well as errors that occur during image analysis of the flow data. With phase-contrast imaging, the overall error in flow measurement can be reduced to less than 10%, an acceptable level of error for routine clinical use.
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Affiliation(s)
- Joachim Lotz
- Department of Diagnostic Radiology, Medical School Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany.
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Klein C, Schalla S, Schnackenburg B, Bornstedt A, Fleck E, Nagel E. Magnetic resonance flow measurements in real time: comparison with a standard gradient-echo technique. J Magn Reson Imaging 2001; 14:306-10. [PMID: 11536408 DOI: 10.1002/jmri.1187] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Ultrafast gradient systems and hybrid imaging sequences offer the opportunity to acquire phase contrast flow data in real time. In a 1.5-Tesla magnetic resonance (MR)-tomograph, peak velocity and volume flow were assessed in 36 large vessels (aorta) and 33 medium-sized vessels (carotid and iliac artery) using a real-time (segmented k-space turbo gradient-echo planar imaging sequence) in comparison with a gradient-echo technique. With the real-time technique, the matrix was reduced from 116 to 64, and temporal resolution changed from 30 msec to 124 msec. Measurements of peak velocity correlated in large (r = 0.88) and medium-sized vessels (r = 0.81). Volume flow measurements correlated in large vessels (r = 0.87), however, a poor correlation (r = 0.64) was found in medium-sized vessels. Thus, scan time can be significantly reduced and images acquired without electrocardiogram (ECG)-triggering. Flow volume can only be determined in large vessels with sufficient accuracy, mainly due to reduced spatial resolution in smaller vessels.
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Affiliation(s)
- C Klein
- Department of Internal Medicine/Cardiology, German Heart Institute Berlin, Humboldt University, Augustenburger Platz 1, D-13353 Berlin, Germany
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Robertson MB, Köhler U, Hoskins PR, Marshall I. Quantitative analysis of PC MRI velocity maps: pulsatile flow in cylindrical vessels. Magn Reson Imaging 2001; 19:685-95. [PMID: 11672627 DOI: 10.1016/s0730-725x(01)00376-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The accuracy of MR phase contrast (PC) velocity mapping, and the subsequent derivation of wall shear stress (WSS) values, has been quantitatively assessed. Using a retrospectively gated PC gradient-echo technique, the temporal-spatial velocity fields were measured for pulsatile flow in a rigid cylindrical vessel. The experimental data were compared with values derived from the Womersley solution of the Navier-Stokes equations. For a sinusoidal waveform, the overall root-mean-square (rms) difference between the measured and analytical velocities corresponded to 13% of the peak fluid velocity. The WSS derived from the data displayed a 14% rms difference with the analytical model. As an example of a more complicated flow, a triangular saw-tooth waveform was deconstructed into its Fourier components. Velocity maps and the WSS were calculated by the superposition of the individual solutions, weighted by the Fourier series coefficient, for each harmonic. The velocity and experimentally derived WSS agreed with the analytical results (4% and 12% rms difference, respectively). Evaluation of the analytical models allowed an estimate of the inherent accuracy in the measurement of velocity maps and WSS values.
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Affiliation(s)
- M B Robertson
- Department of Medical Physics and Medical Engineering, University of Edinburgh, Western General Hospital, Crewe Road, EH4 2XU, Edinburgh, United Kingdom.
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