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Abstract
OBJECTIVE MRI is commonly used to evaluate the articular cartilage of the knee and hip joints in clinical practice. This article will discuss the advantages and limitations of currently available MRI techniques for evaluating articular cartilage. CONCLUSION Because of its high spatial resolution, multiplanar capability, and excellent tissue contrast, MRI is the imaging technique of choice for evaluating the articular cartilage of the knee and hip joints.
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52
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MacKenzie JD, Vasanawala SS. State-of-the-art in pediatric body and musculoskeletal magnetic resonance imaging. Semin Ultrasound CT MR 2010; 31:86-99. [PMID: 20304318 DOI: 10.1053/j.sult.2010.01.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Pediatric body and musculoskeletal MRI has seen tremendous advances over the past few years. These advances have enabled high-quality imaging in even the smallest children and expanded the range of clinical problems amenable to MRI. In this review, we highlight some advances: transition to 3 Tesla, parallel imaging, motion compensation, and new contrast agents. Given the increasing saliency of concerns regarding ionizing radiation from computed tomography, these advances could not be more welcome.
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Affiliation(s)
- John D MacKenzie
- Division of Pediatric Radiology, Lucile Packard Children's Hospital, Stanford University, Palo Alto, CA 94304, USA
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53
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Barral JK, Bangerter NK, Hu BS, Nishimura DG. In vivo high-resolution magnetic resonance skin imaging at 1.5 T and 3 T. Magn Reson Med 2010; 63:790-6. [PMID: 20146351 DOI: 10.1002/mrm.22271] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
As a noninvasive modality, MR is attractive for in vivo skin imaging. Its unique soft tissue contrast makes it an ideal imaging modality to study the skin water content and to resolve the different skin layers. In this work, the challenges of in vivo high-resolution skin imaging are addressed. Three 3D Cartesian sequences are customized to achieve high-resolution imaging and their respective performance is evaluated. The balanced steady-state free precession (bSSFP) and gradient echo (GRE) sequences are fast but can be sensitive to off-resonance artifacts. The fast large-angle spin echo (FLASE) sequence provides a sharp depiction of the hypodermis structures but results in more specific absorption rate (SAR). The effect of increasing the field strength is assessed. As compared to 1.5 T, signal-to-noise ratio at 3 T slightly increases in the hypodermis and almost doubles in the dermis. The need for fat/water separation is acknowledged and a solution using an interleaved three-point Dixon method and an iterative reconstruction is shown to be effective. The effects of motion are analyzed and two techniques to prevent motion and correct for it are evaluated. Images with 117 x 117 x 500 microm(3) resolution are obtained in imaging times under 6 min.
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Affiliation(s)
- Joëlle K Barral
- Department of Electrical Engineering, Stanford University, Stanford, California, USA.
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54
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Klaers J, Jashnani Y, Jung Y, Brodsky E, Jacobson J, Kijowski R, Block WF. Dual half-echo phase correction for implementation of 3D radial SSFP at 3.0 T. Magn Reson Med 2010; 63:282-9. [PMID: 20099322 DOI: 10.1002/mrm.22284] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Fat/water separation methods such as fluctuating equilibrium magnetic resonance and linear combination steady-state free precession have not yet been successfully implemented at 3.0 T due to extreme limitations on the time available for spatial encoding with the increase in magnetic field strength. We present a method to utilize a three-dimensional radial sequence combined with linear combination steady-state free precession at 3.0 T to take advantage of the increased signal levels over 1.5 T and demonstrate high spatial resolution compared to Cartesian techniques. We exploit information from the two half-echoes within each pulse repetition time to correct the accumulated phase on a point-by-point basis, thereby fully aligning the phase of both half-echoes. The correction provides reduced sensitivity to static field (B(0)) inhomogeneity and robust fat/water separation. Resultant images in the knee joint demonstrate the necessity of such a correction, as well as the increased isotropic spatial resolution attainable at 3.0 T. Results of a clinical study comparing this sequence to conventional joint imaging sequences are included.
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Affiliation(s)
- Jessica Klaers
- Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.
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55
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Jung KJ. Synthesis methods of multiple phase-cycled SSFP images to reduce the band artifact and noise more reliably. Magn Reson Imaging 2010; 28:103-18. [DOI: 10.1016/j.mri.2009.05.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 05/19/2009] [Accepted: 05/19/2009] [Indexed: 10/20/2022]
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56
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Bley TA, Wieben O, François CJ, Brittain JH, Reeder SB. Fat and water magnetic resonance imaging. J Magn Reson Imaging 2009; 31:4-18. [DOI: 10.1002/jmri.21895] [Citation(s) in RCA: 249] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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57
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Cukur T, Nishimura DG. Multiple repetition time balanced steady-state free precession imaging. Magn Reson Med 2009; 62:193-204. [PMID: 19449384 DOI: 10.1002/mrm.21990] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although balanced steady-state free precession (bSSFP) imaging yields high signal-to-noise ratio (SNR) efficiency, the bright lipid signal is often undesirable. The bSSFP spectrum can be shaped to suppress the fat signal with scan-efficient alternating repetition time (ATR) bSSFP. However, the level of suppression is limited, and the pass-band is narrow due to its nonuniform shape. A multiple repetition time (TR) bSSFP scheme is proposed that creates a broad stop-band with a scan efficiency comparable with ATR-SSFP. Furthermore, the pass-band signal uniformity is improved, resulting in fewer shading/banding artifacts. When data acquisition occurs in more than a single TR within the multiple-TR period, the echoes can be combined to significantly improve the level of suppression. The signal characteristics of the proposed technique were compared with bSSFP and ATR-SSFP. The multiple-TR method generates identical contrast to bSSFP, and achieves up to an order of magnitude higher stop-band suppression than ATR-SSFP. In vivo studies at 1.5 T and 3 T demonstrate the superior fat-suppression performance of multiple-TR bSSFP.
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Affiliation(s)
- Tolga Cukur
- Department of Electrical Engineering, Stanford University, Stanford, CA 94305-9510, USA.
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58
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Gold GE, Chen CA, Koo S, Hargreaves BA, Bangerter NK. Recent advances in MRI of articular cartilage. AJR Am J Roentgenol 2009; 193:628-38. [PMID: 19696274 PMCID: PMC2879429 DOI: 10.2214/ajr.09.3042] [Citation(s) in RCA: 156] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
OBJECTIVE MRI is the most accurate noninvasive method available to diagnose disorders of articular cartilage. Conventional 2D and 3D approaches show changes in cartilage morphology. Faster 3D imaging methods with isotropic resolution can be reformatted into arbitrary planes for improved detection and visualization of pathology. Unique contrast mechanisms allow us to probe cartilage physiology and detect changes in cartilage macromolecules. CONCLUSION MRI has great promise as a noninvasive comprehensive tool for cartilage evaluation.
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Affiliation(s)
- Garry E Gold
- Department of Radiology, Stanford University, 300 Pasteur Dr., Grant Bldg. S0-68B, Stanford, CA 94305-5105, USA.
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59
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Cukur T, Lee JH, Bangerter NK, Hargreaves BA, Nishimura DG. Non-contrast-enhanced flow-independent peripheral MR angiography with balanced SSFP. Magn Reson Med 2009; 61:1533-9. [PMID: 19365850 DOI: 10.1002/mrm.21921] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Flow-independent angiography is a non-contrast-enhanced technique that can generate vessel contrast even with reduced blood flow in the lower extremities. A method is presented for producing these angiograms with magnetization-prepared balanced steady-state free precession (bSSFP). Because bSSFP yields bright fat signal, robust fat suppression is essential for detailed depiction of the vasculature. Therefore, several strategies have been investigated to improve the reliability of fat suppression within short scan times. Phase-sensitive SSFP can efficiently suppress fat; however, partial volume effects due to fat and water occupying the same voxel can lead to the loss of blood signal. In contrast, alternating repetition time (ATR) SSFP minimizes this loss; however, the level of suppression is compromised by field inhomogeneity. Finally, a new double-acquisition ATR-SSFP technique reduces this sensitivity to off-resonance. In vivo results indicate that the two ATR-based techniques provide more reliable contrast when partial volume effects are significant.
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Affiliation(s)
- Tolga Cukur
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.
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60
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Moran CJ, Kelcz F, Jung Y, Brodsky EK, Fain SB, Block WF. Pilot study of improved lesion characterization in breast MRI using a 3D radial balanced SSFP technique with isotropic resolution and efficient fat-water separation. J Magn Reson Imaging 2009; 30:135-44. [PMID: 19557728 DOI: 10.1002/jmri.21807] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
PURPOSE To assess a 3D radial balanced steady-state free precession (SSFP) technique that provides submillimeter isotropic resolution and inherently registered fat and water image volumes in comparison to conventional T2-weighted RARE imaging for lesion characterization in breast magnetic resonance imaging (MRI). MATERIALS AND METHODS 3D projection SSFP (3DPR-SSFP) combines a dual half-echo radial k-space trajectory with a linear combination fat/water separation technique (linear combination SSFP). A pilot study was performed in 20 patients to assess fat suppression and depiction of lesion morphology using 3DPR-SSFP. For all patients fat suppression was measured for the 3DPR-SSFP image volumes and depiction of lesion morphology was compared against corresponding T2-weighted fast spin echo (FSE) datasets for 15 lesions in 11 patients. RESULTS The isotropic 0.63 mm resolution of the 3DPR-SSFP sequence demonstrated improved depiction of lesion morphology in comparison to FSE. The 3DPR-SSFP fat and water datasets were available in a 5-minute scan time while average fat suppression with 3DPR-SSFP was 71% across all 20 patients. CONCLUSION 3DPR-SSFP has the potential to improve the lesion characterization information available in breast MRI, particularly in comparison to conventional FSE. A larger study is warranted to quantify the effect of 3DPR-SSFP on specificity.
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Affiliation(s)
- Catherine J Moran
- Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.
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61
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Kijowski R, Blankenbaker DG, Klaers JL, Shinki K, De Smet AA, Block WF. Vastly Undersampled Isotropic Projection Steady-State Free Precession Imaging of the Knee: Diagnostic Performance Compared with Conventional MR. Radiology 2009; 251:185-94. [DOI: 10.1148/radiol.2511081133] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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62
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Vonken EJPA, Schär M, Stuber M. Positive contrast visualization of nitinol devices using susceptibility gradient mapping. Magn Reson Med 2009; 60:588-94. [PMID: 18727096 DOI: 10.1002/mrm.21688] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
MRI visualization of devices is traditionally based on signal loss due to T(2)* effects originating from local susceptibility differences. To visualize nitinol devices with positive contrast, a recently introduced postprocessing method is adapted to map the induced susceptibility gradients. This method operates on regular gradient-echo MR images and maps the shift in k-space in a (small) neighborhood of every voxel by Fourier analysis followed by a center-of-mass calculation. The quantitative map of the local shifts generates the positive contrast image of the devices, while areas without susceptibility gradients render a background with noise only. The positive signal response of this method depends only on the choice of the voxel neighborhood size. The properties of the method are explained and the visualizations of a nitinol wire and two stents are shown for illustration.
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Affiliation(s)
- Evert-jan P A Vonken
- Russell H Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
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63
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Cukur T, Nishimura DG. Fat-water separation with alternating repetition time balanced SSFP. Magn Reson Med 2008; 60:479-84. [PMID: 18666114 DOI: 10.1002/mrm.21692] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Balanced SSFP achieves high SNR efficiency, but suffers from bright fat signal. In this work, a multiple-acquisition fat-water separation technique using alternating repetition time (ATR) balanced SSFP is proposed. The SSFP profile can be modified using alternating repetition times and appropriate phase cycling to yield two spectra where fat and water are in-phase and out-of-phase, respectively. The signal homogeneity and the broad width of the created in-phase and out-of-phase profiles lead to signal cancellation over a broad stop-band. The stop-band suppression is achieved for a wide range of flip angles and tissue parameters. This property, coupled with the inherent flexibility of ATR SSFP in repetition time selection, makes the method a good candidate for fat-suppressed SSFP imaging. The proposed method can be tailored to achieve a smaller residual stop-band signal or a decreased sensitivity to field inhomogeneity depending on application-specific needs.
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Affiliation(s)
- Tolga Cukur
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.
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64
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Kijowski R, Tuite M, Passov L, Shimakawa A, Yu H, Hu H, Reeder SB. Cartilage imaging at 3.0T with gradient refocused acquisition in the steady-state (GRASS) and IDEAL fat-water separation. J Magn Reson Imaging 2008; 28:167-74. [PMID: 18581337 DOI: 10.1002/jmri.21414] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To demonstrate the feasibility of evaluating the articular cartilage of the knee joint at 3.0T using gradient refocused acquisition in the steady-state (GRASS) and iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) fat-water separation. MATERIALS AND METHODS Bloch equation simulations and a clinical pilot study (n = 10 knees) were performed to determine the influence of flip angle of the IDEAL-GRASS sequence on the signal-to-noise ratio (SNR) of cartilage and synovial fluid and the contrast-to-noise ratio (CNR) between cartilage and synovial fluid at 3.0T. The optimized IDEAL-GRASS sequence was then performed on 30 symptomatic patients as part of the routine 3.0T knee MRI examination at our institution. RESULTS The optimal flip angle was 50 degrees for IDEAL-GRASS cartilage imaging, which maximized contrast between cartilage and synovial fluid. The IDEAL-GRASS sequence consistently produced high-quality fat- and water-separated images of the knee with bright synovial fluid and 0.39 x 0.67 x 1.0 mm resolution in 5 minutes. IDEAL-GRASS images had high cartilage SNR and high contrast between cartilage and adjacent joint structures. The IDEAL-GRASS sequence provided excellent visualization of cartilage lesions in all patients. CONCLUSION The IDEAL-GRASS sequence shows promise for use as a morphologic cartilage imaging sequence at 3.0T.
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Affiliation(s)
- Richard Kijowski
- Department of Radiology, University of Wisconsin, 600 Highland Avenue, Madison, WI 53792, USA.
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65
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Abstract
This article describes the considerable technical achievements that have been made in MR imaging in the evaluation of pediatric patients. The latest techniques in improving signal intensity, resolution, and speed are discussed. The multitude of new options for pediatric MR imaging are illustrated, including higher field strength imaging, multi-channel coil technology coupled with parallel imaging, and new pulse sequence designs. Several future directions in the field of pediatric body and musculoskeletal imaging also are highlighted.
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66
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Miraux S, Massot P, Ribot EJ, Franconi JM, Thiaudiere E. 3D TrueFISP imaging of mouse brain at 4.7T and 9.4T. J Magn Reson Imaging 2008; 28:497-503. [DOI: 10.1002/jmri.21449] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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67
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Ramadan SS, Heyn C, MacKenzie LT, Chambers AF, Rutt BK, Foster PJ. Ex-vivo cellular MRI with b-SSFP: quantitative benefits of 3 T over 1.5 T. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2008; 21:251-9. [DOI: 10.1007/s10334-008-0118-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 05/25/2008] [Accepted: 05/26/2008] [Indexed: 10/21/2022]
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68
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Abstract
This article illustrates changes in the underlying physics concepts related to increasing the main magnetic field from 1.5T to 3T. The effects of these changes on tissue constants and practical hardware limitations is discussed as they affect scan time, quality, and contrast. Changes in susceptibility artifacts, chemical shift artifacts, and dielectric effects as a result of the increased field strength are also illustrated. Based on these fundamental considerations, an overall understanding of the benefits and constraints of signal-to-noise ratio and contrast-to-noise ratio changes between 1.5T and 3T MR systems is developed.
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Affiliation(s)
- Brian J Soher
- Center for Advanced MR Development, Duke University Medical Center, Box 3808, Durham, NC 27710, USA.
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69
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Watanabe Y, Nagayama M, Okumura A, Amoh Y, Katsube T, Suga T, Koyama S, Nakatani K, Dodo Y. MR imaging of acute biliary disorders. Radiographics 2007; 27:477-95. [PMID: 17374864 DOI: 10.1148/rg.272055148] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In patients with acute right-sided epigastric pain, jaundice, and a high fever, it is essential to accurately diagnose the cause of the symptoms, differentiate acute biliary disorders from nonbiliary disorders, and evaluate the severity of the disease. Gray-scale ultrasonography (US) and computed tomography (CT) are useful primary imaging modalities, but their results are not always conclusive. Magnetic resonance (MR) imaging, including MR cholangiopancreatography, can be a valuable complement to US and CT when additional information is needed. MR images have excellent tissue contrast and can provide more specific information, allowing diagnosis of complications that arise from acute cholecystitis, such as empyema, gangrenous cholecystitis, gallbladder perforation, enterocholecystic fistula, emphysematous cholecystitis, and hemorrhagic cholecystitis. In addition, causes of obstructive jaundice, acute suppurative cholangitis, and hemobilia can be clearly demonstrated with multisequence MR imaging. Single-section MR cholangiopancreatography and heavily T2-weighted imaging, in combination with fat-suppressed T1- and T2-weighted imaging, provide comprehensive and detailed information about the biliary system around the obstruction site, biliary calculi, inflammatory processes, purulent material, abscesses, gas, and hemorrhage. Contrast-enhanced MR imaging is useful for evaluation of the gallbladder wall; lack of enhancement and disruption of the wall may be findings specific for gangrenous cholecystitis and gallbladder perforation, respectively.
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Affiliation(s)
- Yuji Watanabe
- Department of Radiology, Kurashiki Central Hospital, 1-1-1 Miwa, Kurashiki 710-8602, Japan.
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70
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Duc SR, Koch P, Schmid MR, Horger W, Hodler J, Pfirrmann CWA. Diagnosis of articular cartilage abnormalities of the knee: prospective clinical evaluation of a 3D water-excitation true FISP sequence. Radiology 2007; 243:475-82. [PMID: 17400759 DOI: 10.1148/radiol.2432060274] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
PURPOSE To prospectively evaluate the accuracy of three-dimensional (3D) water-excitation true fast imaging with steady-state precession (FISP) in the assessment of cartilage abnormalities of the knee, by using surgery as the reference standard. MATERIALS AND METHODS The study was approved by the hospital institutional review board. Written informed consent was obtained from all patients. Twenty-nine patients (30 knees) with a mean age of 56 years (range, 18-86 years) were prospectively evaluated with a sagittal 3D true FISP magnetic resonance (MR) sequence. The mean interval between MR imaging and surgery was 1 day (range, 0-9 days). During surgery, the articular surfaces of the knee were evaluated by using a modified Noyes score. The MR images were evaluated by two blinded readers on two separate occasions. Diagnostic performance was evaluated by setting the cutoff for abnormality between grade 1 (intact cartilage surface) and grade 2 (cartilage defects). Statistical methods used included calculation of sensitivity, specificity, and accuracy, with 95% confidence intervals (Wilson score method) and calculation of kappa values with standard errors. RESULTS Overall sensitivity, specificity, and accuracy for the two readers and the two evaluations ranged from 56% to 66%, 78% to 93%, and 71% to 75%, respectively. Interobserver agreement was substantial for both the first (kappa = 0.73) and the second (kappa = 0.65) evaluation. Intraobserver agreement was almost perfect (kappa = 0.84) for reader 1 and moderate (kappa = 0.60) for reader 2. CONCLUSION The 3D water-excitation true FISP MR sequence allows assessment of the articular cartilage of the knee with moderate-to-high specificity and low-to-moderate sensitivity.
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Affiliation(s)
- Sylvain R Duc
- Department of Radiology, University Hospital, Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland
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71
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Gold GE, Hargreaves BA, Reeder SB, Block WF, Kijowski R, Vasanawala SS, Kornaat PR, Bammer R, Newbould R, Bangerter NK, Beaulieu CF. Balanced SSFP imaging of the musculoskeletal system. J Magn Reson Imaging 2007; 25:270-8. [PMID: 17260387 DOI: 10.1002/jmri.20819] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Magnetic resonance imaging (MRI), with its unique ability to image and characterize soft tissue noninvasively, has emerged as one of the most accurate imaging methods available to diagnose bone and joint pathology. Currently, most evaluation of musculoskeletal pathology is done with two-dimensional acquisition techniques such as fast spin echo (FSE) imaging. The development of three-dimensional fast imaging methods based on balanced steady-state free precession (SSFP) shows great promise to improve MRI of the musculoskeletal system. These methods may allow acquisition of fluid sensitive isotropic data that can be reformatted into arbitrary planes for improved detection and visualization of pathology. Sensitivity to fluid and fat suppression are important issues in these techniques to improve delineation of cartilage contours, for detection of marrow edema and derangement of other joint structures.
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Affiliation(s)
- Garry E Gold
- Department of Radiology, Stanford University, Stanford, California, USA.
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72
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Çukur T, Bangerter NK, Nishimura DG. Enhanced spectral shaping in steady-state free precession imaging. Magn Reson Med 2007; 58:1216-23. [DOI: 10.1002/mrm.21413] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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73
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Amrami KK, Desy NM, Stanley DW, Skinner JA, Felmlee JP, Barger AV, Block WF, Spinner RJ. Evaluation of ganglion cysts using vastly undersampled isotropic projection reconstruction (VIPR). J Magn Reson Imaging 2007; 26:768-72. [PMID: 17685420 DOI: 10.1002/jmri.21032] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
For some atypical para-articular ganglia, the presence of a joint connection is highly controversial. The proper preoperative diagnosis and identification of this joint connection for ganglion cysts is important for patient treatment and outcome. MRI is the imaging modality of choice when evaluating such lesions, but the detection of subtle joint connections remains difficult with conventional MR protocols. We investigated the utility of a steady-state free-precession acquisition with isotropic high resolution using the vastly undersampled isotropic projection reconstruction (VIPR) pulse sequence to determine if joint connections for ganglion cysts could be seen more effectively, using the knee region as a model. We evaluated four patients: two with peroneal intraneural ganglion cysts, one with adventitial cystic disease of the popliteal artery, and one patient with a more typical extraneural (intramuscular) cyst. Both conventional MR and VIPR techniques were used. In our clinical experience, we found VIPR to be superior to conventional MR techniques in detecting and depicting joint connections in typical and atypical ganglion cysts around the knee.
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Affiliation(s)
- Kimberly K Amrami
- Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905, USA.
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74
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Gold GE, Hargreaves BA, Stevens KJ, Beaulieu CF. Advanced magnetic resonance imaging of articular cartilage. Orthop Clin North Am 2006; 37:331-47, vi. [PMID: 16846765 DOI: 10.1016/j.ocl.2006.04.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
MRI is one of the most accurate imaging methods available to diagnose disorders of articular cartilage. Conventional two-dimensional and three-dimensional approaches show changes in cartilage morphology. Newer and substantially faster three-dimensional imaging methods show great promise to improve MRI of cartilage. These methods may allow acquisition of fluid-sensitive isotropic data that can be reformatted into arbitrary planes for improved detection and visualization of pathology. Unique MRI contrast mechanisms also allow clinicians to probe cartilage physiology and detect early changes in cartilage macromolecules.
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Affiliation(s)
- Garry E Gold
- Department of Radiology, Stanford University, 300 Pasteur Drive S0-56, Stanford, CA 94305-9510, USA.
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75
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Gold GE, Reeder SB, Yu H, Kornaat P, Shimakawa AS, Johnson JW, Pelc NJ, Beaulieu CF, Brittain JH. Articular cartilage of the knee: rapid three-dimensional MR imaging at 3.0 T with IDEAL balanced steady-state free precession--initial experience. Radiology 2006; 240:546-51. [PMID: 16801369 DOI: 10.1148/radiol.2402050288] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. In this study, iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) balanced steady-state free precession (bSSFP), fat-suppressed bSSFP, and fat-suppressed spoiled gradient-echo (GRE) sequences for 3.0-T magnetic resonance (MR) imaging of articular knee cartilage were prospectively compared in five healthy volunteers. Cartilage and fluid signal-to-noise ratio (SNR), cartilage-fluid contrast-to-noise ratio (CNR), SNR efficiency, CNR efficiency, image quality, and fat suppression were compared. Fat-suppressed bSSFP and IDEAL bSSFP had higher SNR efficiency of cartilage (P < .01) than did GRE. IDEAL bSSFP had higher cartilage-fluid CNR efficiency than did fat-suppressed bSSFP or GRE (P < .01). Fat-suppressed bSSFP and IDEAL bSSFP had higher image quality than did GRE (P < .01). GRE and IDEAL bSSFP had significantly better fat-water separation or fat saturation than did fat-suppressed bSSFP (P < .05). IDEAL bSSFP is a promising method for imaging articular knee cartilage.
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Affiliation(s)
- Garry E Gold
- Department of Radiology, Stanford University School of Medicine, 300 Pasteur Dr, SO-68B, Stanford, CA 94305-5105, USA.
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76
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Gold GE, Burstein D, Dardzinski B, Lang P, Boada F, Mosher T. MRI of articular cartilage in OA: novel pulse sequences and compositional/functional markers. Osteoarthritis Cartilage 2006; 14 Suppl A:A76-86. [PMID: 16716605 DOI: 10.1016/j.joca.2006.03.010] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Accepted: 03/17/2006] [Indexed: 02/02/2023]
Abstract
Osteoarthritis (OA) is a leading cause of disability worldwide. Magnetic resonance imaging (MRI), with its unique ability to image and characterize soft tissue non-invasively, has proven valuable in assessing cartilage in OA. The development of new, fast imaging methods with high contrast show promise to improve the magnetic resonance (MR) evaluation of this disease. In addition to morphologic MRI methods, MRI contrast mechanisms under development may reveal detailed information about the physiology of cartilage. It is anticipated that these and other MRI techniques will play an increasingly important role in assessing the success or failure of therapies for OA. On December 5 and 6, 2002, OMERACT (Outcome Measures in Rheumatology Clinical Trials) and OARSI (Osteoarthritis Research Society International) held a workshop in Bethesda, MD aiming at providing a state-of-the-art review of imaging outcome measures for OA of the knee to help guide scientists and pharmaceutical companies in the use of MRI in multi-site studies of OA. Applications of MRI were initially reviewed by a multidisciplinary, international panel of expert scientists and physicians from academia, the pharmaceutical industry and regulatory agencies. The findings of the panel were then presented to a wider group of participants for open discussion. The following report summarizes the results of these discussions with respect to novel MRI pulse sequences for evaluating articular cartilage of the knee in OA and notes any additional advances that have been made since.
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77
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Miller KL, Smith SM, Jezzard P, Pauly JM. High-resolution FMRI at 1.5T using balanced SSFP. Magn Reson Med 2006; 55:161-70. [PMID: 16345040 DOI: 10.1002/mrm.20753] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The resolution in conventional BOLD FMRI is considerably lower than can be achieved with other MRI methods, and is insufficient for many important applications. One major difficulty in robustly improving spatial resolution is the poor image quality in BOLD FMRI, which suffers from distortions, blurring, and signal dropout. This work considers the potential for increased resolution with a new FMRI method based on balanced SSFP. This method establishes a blood oxygenation sensitive steady-state (BOSS) signal, in which the frequency sensitivity of balanced SSFP is used to detect the frequency shift of deoxyhemoglobin. BOSS FMRI is highly SNR efficient and does not suffer from image distortions or signal dropout, making this method an excellent candidate for high-resolution FMRI. This study presents the first demonstration of high-resolution BOSS FMRI, using an efficient 3D stack-of-segmented EPI readout and combined acquisition at multiple center frequencies. BOSS FMRI is shown to enable high-resolution FMRI data (1 x 1 x 2 mm(3)) in both visual and motor systems using standard hardware at 1.5 T. Currently, the major limitation of BOSS FMRI is its sensitivity to temporal and spatial field drift.
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Affiliation(s)
- Karla L Miller
- Oxford Centre for Functional MRI of the Brain, FMRIB, Oxford University, UK.
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78
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Bieri O, Maderwald S, Ladd ME, Scheffler K. Balanced alternating steady-state elastography. Magn Reson Med 2006; 55:233-41. [PMID: 16416431 DOI: 10.1002/mrm.20812] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A conventional balanced steady-state free precession (b-SSFP) sequence scheme was modified such that the dynamic equilibrium becomes very sensitive to small cyclic displacements, generating two distinct and alternating steady states. This novel technique is proposed for the visualization of propagating transverse acoustic shear waves, as used in MR elastography (MRE) to determine the mechanical properties of materials or in vivo soft tissue. Experiments with tissue-like agarose gel phantoms and simulations demonstrate that the novel sequence offers an increase in phase sensitivity by about one order in magnitude compared to standard motion-encoding methods. In addition, the new method benefits from the very short acquisition times achieved by b-SSFP protocols.
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Affiliation(s)
- O Bieri
- MR Physics, Department of Medical Radiology, University of Basel, Basel, Switzerland.
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79
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Gold GE, Hargreaves BA, Vasanawala SS, Webb JD, Shimakawa AS, Brittain JH, Beaulieu CF. Articular Cartilage of the Knee: Evaluation with Fluctuating Equilibrium MR Imaging—Initial Experience in Healthy Volunteers. Radiology 2006; 238:712-8. [PMID: 16436826 DOI: 10.1148/radiol.2381042183] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Institutional review board approval and informed consent were obtained for this HIPAA-compliant study, whose purpose was to prospectively compare three magnetic resonance (MR) imaging techniques-fluctuating equilibrium, three-dimensional (3D) spoiled gradient-recalled acquisition in the steady state (SPGR), and two-dimensional (2D) fast spin echo (SE)-for evaluating articular cartilage in the knee. The study cohort consisted of 10 healthy volunteers (four men, six women; age range, 26-42 years). Cartilage signal-to-noise ratio (SNR), SNR efficiency, cartilage-fluid contrast-to-noise ratio (CNR), CNR efficiency, image quality, cartilage visibility, and fat suppression were compared. Cartilage volume was compared for the fluctuating equilibrium and 3D SPGR techniques. Compared with 3D SPGR and 2D fast SE, fluctuating equilibrium yielded the highest cartilage SNR efficiency and cartilage-fluid CNR efficiency (P < .01 for both). Image quality was similar with all sequences. Fluctuating equilibrium imaging yielded higher cartilage visibility than did 2D fast SE imaging (P <. 01) but worse fat suppression than did 3D SPGR and 2D fast SE imaging (P < .04). Cartilage volume measurements with fluctuating equilibrium and 3D SPGR were similar. Fluctuating equilibrium MR imaging is a promising method for evaluating articular cartilage in the knee.
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Affiliation(s)
- Garry E Gold
- Department of Radiology, Stanford University, 300 Pasteur Dr, SO-68B, Stanford, CA 94305-5105, USA.
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80
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Absil J, Denolin V, Metens T. Fat attenuation using a dual steady-state balanced-SSFP sequence with periodically variable flip angles. Magn Reson Med 2006; 55:343-51. [PMID: 16402382 DOI: 10.1002/mrm.20766] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A refocused-SSFP sequence based on balanced-FFE (TrueFisp, Fiesta) that attenuates fat signal is presented. The sequence uses periodically variable flip angles and produces a dual steady state of the signal, which is obtained after a dual transient phase if an appropriate preparation is used. The off-resonance profile of the steady-state signal exhibits large stopbands that can be employed for fat suppression. Numerical simulations were performed to investigate the signal behavior and the off-resonance properties of the sequence. Experimental results obtained with a Philips Gyroscan Intera 1.5T MR scanner demonstrated fat attenuation in phantoms and abdominal images in volunteers.
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Affiliation(s)
- J Absil
- Unité d'IRM-Radiologie, Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium.
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81
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Hargreaves BA, Bangerter NK, Shimakawa A, Vasanawala SS, Brittain JH, Nishimura DG. Dual-acquisition phase-sensitive fat–water separation using balanced steady-state free precession. Magn Reson Imaging 2006; 24:113-22. [PMID: 16455400 DOI: 10.1016/j.mri.2005.10.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Accepted: 10/22/2005] [Indexed: 10/25/2022]
Abstract
Balanced steady-state free precession (SSFP) sequences use fully re-focussed gradient waveforms to achieve a high signal and useful image contrast in short scan times. Despite these strengths, the clinical feasibility of balanced SSFP is still limited both by bright fat signal and by the signal voids that result from off-resonance effects such as field or susceptibility variations. A new method, dual-acquisition phase-sensitive SSFP, combines the signals from two standard balanced SSFP acquisitions to separate fat and water while simultaneously reducing the signal voids. The acquisitions are added in quadrature and then phase corrected using a simple algorithm before fat and water can be identified simply by the sign of the signal. This method is especially useful for applications at high field, where the RF power deposition, spatial resolution requirements and gradient strength limit the minimum repetition times. Finally, dual-acquisition phase-sensitive SSFP can be combined with other magnetization preparation schemes to produce specific image contrast in addition to separating fat and water signals.
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Affiliation(s)
- Brian A Hargreaves
- Department of Radiology, Stanford University, Stanford, CA 94305-5488, USA
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82
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Derbyshire JA, Herzka DA, McVeigh ER. S5FP: spectrally selective suppression with steady state free precession. Magn Reson Med 2006; 54:918-28. [PMID: 16155880 DOI: 10.1002/mrm.20633] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A method is presented that employs the inherent spectral selectivity of the Steady-State Free Precession (SSFP) pulse sequence to provide a spectral band of suppression. At TE = TR/2, SSFP partitions the magnetization into two phase-opposed spectral components. Z-storing one of these components simultaneously further excites the other, which is then suppressed by gradient crushing and RF spoiling. The Spectrally Selective Suppression with SSFP (S(5)FP) method is shown to provide significant attenuation of fat signals, while the water signals are essentially unaffected and provide the normal SSFP contrast. Fat suppression is achieved with relatively little temporal overhead (less than 10% reduction in temporal resolution). S(5)FP was validated using simulations, phantoms, and human studies.
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Affiliation(s)
- J A Derbyshire
- Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, DHHS, Bethesda, MD 20892-1061, USA.
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83
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Lu A, Grist TM, Block WF. Fat/water separation in single acquisition steady-state free precession using multiple echo radial trajectories. Magn Reson Med 2006; 54:1051-7. [PMID: 16217786 DOI: 10.1002/mrm.20715] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Phase detection in fully refocused SSFP imaging has recently allowed fat/water separation without preparing the magnetization or using multiple acquisitions. Instead, it exploits the phase difference between fat and water at an echo time at the midpoint of the TR. To minimize the TR for improved robustness to B0 inhomogeneity, a 3D projection acquisition collecting two half echoes at the beginning and end of each excitation was previously implemented. Since echoes are not formed at the midpoint of the TR, this method still requires two passes of k-space for fat/water separation. A new method is presented to linearly combine the half echoes to separate fat and water in a single acquisition. Separation using phase detection provides superior contrast between fat and water voxels. Results from high resolution angiography and musculoskeletal studies with improved robustness to inhomogeneity and a 50% scan time reduction compared to the two pass method are presented.
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Affiliation(s)
- Aiming Lu
- Department of Biomedical Engineering, University of Wisconsin, Madison, WI 53792-3252, USA
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84
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Paul D, Hennig J, Zaitsev M. Intrinsic fat suppression in TIDE balanced steady-state free precession imaging. Magn Reson Med 2006; 56:1328-35. [PMID: 17089365 DOI: 10.1002/mrm.21084] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A novel fat-suppressed balanced steady-state free precession (b-SSFP) imaging method based on the transition into driven equilibrium (TIDE) sequence with variable flip angles is presented. The new method, called fat-saturated (FS)-TIDE, exploits the special behavior of TIDE signals from off-resonance spins during the flip angle ramp. As shown by simulations and experimental data, the TIDE signal evolution for off-resonant isochromats during the transition from turbo spin-echo (TSE)-like behavior to the true fast imaging with steady precession (TrueFISP) mode undergoes a zero crossing. The resulting signal notch for off-resonant spins is then used for fat suppression. The efficiency of FS-TIDE is demonstrated in phantoms and healthy volunteers on a 1.5T system. The resulting images are compared with standard TrueFISP data with and without fat suppression. It is demonstrated that FS-TIDE provides a fast and stable means for homogenous fat suppression in abdominal imaging while maintaining balanced SSFP-like image contrast and signal-to-noise ratio (SNR). The scan time of FS-TIDE is not increased compared to normal TrueFISP imaging without fat suppression and identical k-space trajectories. Because of the intrinsic fat suppression, no additional preparation is needed. Possible repetition times (TRs) are not firmly limited to special values and are nearly arbitrary.
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Affiliation(s)
- Dominik Paul
- Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany.
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85
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Leupold J, Hennig J, Scheffler K. Alternating repetition time balanced steady state free precession. Magn Reson Med 2006; 55:557-65. [PMID: 16447171 DOI: 10.1002/mrm.20790] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A novel balanced SSFP technique for the separation or suppression of different resonance frequencies (e.g., fat suppression) is presented. The method is based on applying two alternating and different repetition times, TR(1) and TR(2). This RF scheme manipulates the sensitivity of balanced SSFP to off-resonance effects by a modification of the frequency response profile. Starting from a general approach, an optimally broadened stopband within the frequency response function is designed. This is achieved with a TR(2) being one third of TR(1) and an RF-pulse phase increment of 90 degrees . With this approach TR(2) is too short ( approximately 1 ms) to switch imaging gradients and is only used to change the frequency sensitivity. Without a significant change of the spectral position of the stopband, TR(1) can be varied over a range of values ( approximately 2.5-4.5 ms) while TR(2) and phase cycling is kept constant. On-resonance spins show a magnetization behavior similar to balanced SSFP, but with maximal magnetization at flip angles about 10 degrees lower than in balanced SSFP. The total scan time is increased by about 30% compared to conventional balanced SSFP. The new technique was applied on phantoms and volunteers to produce rapid, fat suppressed images.
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Affiliation(s)
- J Leupold
- Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany.
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86
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Bangerter NK, Hargreaves BA, Gold GE, Stucker DT, Nishimura DG. Fluid-attenuated inversion-recovery SSFP imaging. J Magn Reson Imaging 2006; 24:1426-31. [PMID: 17036358 DOI: 10.1002/jmri.20743] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To describe and evaluate a fast, fluid-suppressed 2D multislice steady-state free precession (SSFP) neuroimaging sequence. MATERIALS AND METHODS We developed a fast fluid-attenuated inversion-recovery SSFP sequence for use in neuroimaging. The inversion time (TI) was optimized to yield good cerebrospinal fluid (CSF) suppression while conserving white matter (WM)/lesion contrast across a broad range of flip angles. Multiple SSFP acquisitions were combined using the sum-of-squares (SOS) method to maximize SNR efficiency while minimizing SSFP banding artifacts. We compared our fluid-attenuated inversion-recovery (FLAIR) SSFP sequence with FLAIR fast spin-echo (FSE) in both normal subjects and a volunteer with multiple sclerosis. SNR measurements were performed to ascertain the SNR efficiency of each sequence. RESULTS Our FLAIR SSFP sequence demonstrated excellent CSF suppression and good gray matter (GM)/WM contrast. Coverage of the entire brain (5-mm slices, 24-cm FOV, 256 x 192 matrix) was achieved with FLAIR SSFP in less than half the scan time of a corresponding FLAIR FSE sequence with similar SNR, yielding improvements of more than 50% in SNR efficiency. Axial scans of a volunteer with multiple sclerosis show clearly visible plaques and very good visualization of brain parenchyma. CONCLUSION We have demonstrated the feasibility of a very fast fluid-suppressed neuroimaging technique using SSFP.
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Affiliation(s)
- Neal K Bangerter
- Department of Electrical Engineering, Stanford University, Stanford, California, USA.
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87
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Eberhardt KW, Schär M, Barmet C, Tsao J, Boesiger P, Kozerke S. Linear response equilibrium. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 178:142-54. [PMID: 16226909 DOI: 10.1016/j.jmr.2005.09.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Revised: 08/14/2005] [Accepted: 09/14/2005] [Indexed: 05/04/2023]
Abstract
A new periodic pulse sequence employing weak excitation is presented. This type of sequence drives the system into a steady-state with periodic time evolution from which the data can be reconstructed to a spectrum. It is demonstrated that the frequency response of such a sequence can be analyzed using perturbation methods and linear system analysis. A mathematical framework is proposed allowing the frequency response to be tailored by weighting a periodic flip function. The weak excitation level used implies very low specific absorption rates while generating a highly frequency selective signal in the order of 1/T2 with signal strengths comparable to those obtainable with conventional large flip angle balanced steady-state free precession techniques. The concept is illustrated with phantom experiments and in vivo feasibility of water fat separation is shown on human knee images.
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Affiliation(s)
- Kai W Eberhardt
- Institute for Biomedical Engineering, University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland
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88
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Kijowski R, Lu A, Block W, Grist T. Evaluation of the articular cartilage of the knee joint with vastly undersampled isotropic projection reconstruction steady-state free precession imaging. J Magn Reson Imaging 2006; 24:168-75. [PMID: 16758476 DOI: 10.1002/jmri.20596] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
PURPOSE To determine the feasibility of the vastly undersampled isotropic projection reconstruction steady-state free precession (VIPR-SSFP) sequence for evaluating the articular cartilage of the knee joint. MATERIALS AND METHODS A magnetic resonance (MR) examination of the knee was performed on 33 subjects using a GE 1.5T scanner and a phased-array extremity coil. VIPR-SSFP, proton density-weighted fast spin-echo (PD-FSE), fat-suppressed T2-weighted fast spin-echo (T2-FSE), and three-dimensional fat-suppressed spoiled gradient recall-echo (SPGR) sequences were performed on three asymptomatic volunteers and 10 patients with osteoarthritis of the knee joint. Signal-to-noise efficiency, and contrast-to-noise ratio (CNR) measurements were calculated for all sequences and compared with the use of paired t-tests. The VIPR-SSFP sequence was then performed on 20 consecutive patients who were undergoing a routine MR examination of the knee. RESULTS The cartilage signal-to-noise efficiency of the VIPR-SSFP sequence was not significantly different from that of the PD-FSE and SPGR sequences. The cartilage signal-to-noise efficiency of the VIPR-SSFP sequence was significantly higher (P < 0.05) than that of the T2-FSE sequence. The VIPR-SSFP sequence produced images with significantly higher (P < 0.05) CNR between cartilage and synovial fluid than the PD-FSE and SPGR sequences, and significantly higher (P < 0.05) CNR between cartilage and subchondral bone than the T2-FSE sequence. The VIPR-SSFP sequence allowed excellent visualization of the articular cartilage of the knee joint in all subjects. All articular cartilage defects identified on the PD-FSE, T2-FSE, and SPGR images were well visualized on the VIPR-SSFP images. CONCLUSION VIPR-SSFP images had high cartilage signal-to-noise efficiency and high CNR between cartilage and adjacent synovial fluid and subchondral bone; therefore, the sequence is well suited for evaluating the articular cartilage of the knee joint.
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Affiliation(s)
- Richard Kijowski
- Department of Radiology, University of Wisconsin Hospital, Madison, Wisconsin, USA.
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89
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Abstract
The signal formation and properties of steady-state free precession (SSFP) in combination with alternating RF pulse phases or alternating spin precession is analyzed. Simulations and experiments demonstrate that the amplitudes of SSFP echo paths are significantly influenced by application of alternating phases either via the exciting RF pulse or via some external mechanism producing alternating spin precession. The influence of alternating phases on echo amplitudes is different for different echo paths. The primary SSFP echo paths F(0) (-) and F(0) (+) exhibit a signal reduction whereas higher-order echoes F(-1) (-) and F(1) (+) show a signal increase upon application of oscillating phases. This behavior can be described using a simple perturbation theory applied to the frequency response profile of balanced SSFP combined with a final signal integration over one balanced SSFP band. The high sensitivity of SSFP echo amplitudes to alternating RF pulse phases or precession is exemplarily used to detect and visualize propagating transverse acoustic shear waves. Detection of flow or alternating currents are further possibilities to apply this unique feature of SSFP.
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Affiliation(s)
- Klaus Scheffler
- MR-Physics, Department of Medical Radiology, University Hospital Basel, Switzerland.
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90
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Reeder SB, Markl M, Yu H, Hellinger JC, Herfkens RJ, Pelc NJ. Cardiac CINE imaging with IDEAL water-fat separation and steady-state free precession. J Magn Reson Imaging 2005; 22:44-52. [PMID: 15971192 DOI: 10.1002/jmri.20327] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To decompose multicoil CINE steady-state free precession (SSFP) cardiac images acquired at short echo time (TE) increments into separate water and fat images, using an iterative least-squares "Dixon" (IDEAL) method. MATERIALS AND METHODS Multicoil CINE IDEAL-SSFP cardiac imaging was performed in three volunteers and 15 patients at 1.5 T. RESULTS Measurements of signal-to-noise ratio (SNR) matched theoretical expectations and were used to optimize acquisition parameters. TE increments of 0.9-1.0 msec permitted the use of repetition times (TRs) of 5 msec or less, and provided good SNR performance of the water-fat decomposition, while maintaining good image quality with a minimum of banding artifacts. Images from all studies were evaluated for fat separation and image quality by two experienced radiologists. Uniform fat separation and diagnostic image quality was achieved in all images from all studies. Examples from volunteers and patients are shown. CONCLUSION Multicoil IDEAL-SSFP imaging can produce high quality CINE cardiac images with uniform water-fat separation, insensitive to Bo inhomogeneities. This approach provides a new method for reliable fat-suppression in cardiac imaging.
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Affiliation(s)
- Scott B Reeder
- Department of Radiology, Stanford University Medical Center, Stanford, California, USA.
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91
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Banerjee S, Han ET, Krug R, Newitt DC, Majumdar S. Application of refocused steady-state free-precession methods at 1.5 and 3 T to in vivo high-resolution MRI of trabecular bone: simulations and experiments. J Magn Reson Imaging 2005; 21:818-25. [PMID: 15906346 DOI: 10.1002/jmri.20348] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To evaluate the potential of fully-balanced steady-state free-precession (SSFP) sequences in in vivo high-resolution (HR) MRI of trabecular bone at field strengths of 1.5 and 3 T by simulation and experimental methods. MATERIALS AND METHODS Using simulation studies, refocused SSFP acquisition was optimized for our imaging purposes with a focus on signal-to-noise ratio (SNR) and SNR efficiency. The signal behavior in trabecular bone was estimated using a magnetostatic model of the trabecular bone and marrow. Eight normal volunteers were imaged at the proximal femur, calcaneus, and the distal tibia on a GE Signa scanner at 1.5 and at 3 T with an optimized single-acquisition SSFP sequence (three-dimensional FIESTA) and an optimized multiple-acquisition SSFP sequence (three-dimensional FIESTA-c). Images were also acquired with a fast gradient echo (FGRE) sequence for evaluation of the SNR performance of SSFP methods. RESULTS Refocused SSFP images outperformed FGRE acquisitions in both SNR and SNR efficiency at both field strengths. At 3 T, susceptibility effects were visible in FIESTA and FGRE images and much reduced in FIESTA-c images. The magnitude of SNR boost at 3 T was closely predicted by simulations. CONCLUSION Single-acquisition SSFP (at 1.5 T) and multiple-acquisition SSFP (at 3 T) hold great potential for HR-MRI of trabecular bone.
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Affiliation(s)
- Suchandrima Banerjee
- Department of Radiology, University of California, San Francisco, San Francisco, California 94107, USA
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92
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Vasanawala SS, Hargreaves BA, Pauly JM, Nishimura DG, Beaulieu CF, Gold GE. Rapid Musculoskeletal MRI with Phase-Sensitive Steady-State Free Precession: Comparison with Routine Knee MRI. AJR Am J Roentgenol 2005; 184:1450-5. [PMID: 15855095 DOI: 10.2214/ajr.184.5.01841450] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The aim of this work was to show the potential utility of a novel rapid 3D fat-suppressed MRI method for joint imaging. CONCLUSION Phase-sensitive steady-state free precession provides rapid 3D joint imaging with robust fat suppression and excellent cartilage delineation.
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Affiliation(s)
- Shreyas S Vasanawala
- Department of Radiology, Stanford University School of Medicine, 300 Pasteur Dr., Stanford, CA 94305-5105, USA.
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93
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Lu A, Brodsky E, Grist TM, Block WF. Rapid fat-suppressed isotropic steady-state free precession imaging using true 3D multiple-half-echo projection reconstruction. Magn Reson Med 2005; 53:692-9. [PMID: 15723411 DOI: 10.1002/mrm.20389] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Three-dimensional projection reconstruction (3D PR)-based techniques are advantageous for steady-state free precession (SSFP) imaging for several reasons, including the capability to achieve short repetition times (TRs). In this paper, a multi-half-echo technique is presented that dramatically improves the data-sampling efficiency of 3D PR sequences while it retains this short-TR capability. The k-space trajectory deviations are measured quickly and corrected on a per-sample point basis. A two-pass RF cycling technique is then applied to the dual-half-echo implementation to generate fat/water-separated images. The resultant improvement in the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) was demonstrated in volunteer studies. Volumetric images with excellent spatial resolution, coverage, and contrast were obtained with high speed. The non-contrast-enhanced SSFP studies show that this technique has promising potential for MR angiography (MRA).
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Affiliation(s)
- Aiming Lu
- Department of Biomedical Engineering, University of Wisconsin, E3/311 Clinical Science Center, 600 Highland Avenue, Madison, WI 53792-3252, USA.
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94
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Reeder SB, Herzka DA, McVeigh ER. Signal-to-noise ratio behavior of steady-state free precession. Magn Reson Med 2004; 52:123-30. [PMID: 15236375 PMCID: PMC2396310 DOI: 10.1002/mrm.20126] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Steady-state free precession (SSFP) is a rapid gradient-echo imaging technique that has recently gained popularity and is used in a variety of applications, including cardiac and real-time imaging, because of its high signal and favorable contrast between blood and myocardium. The purpose of this work was to examine the signal-to-noise ratio (SNR) behavior of images acquired with SSFP, and the dependence of SNR on imaging parameters such as TR, bandwidth, and image resolution, and the use of multi-echo sequences. In this work it is shown that the SNR of SSFP sequences is dependent only on pulse sequence efficiency, voxel dimensions, and relaxation parameters (T1 and T2). Notably, SNR is insensitive to bandwidth unless increases in bandwidth significantly decrease efficiency. Finally, we examined the relationship between pulse sequence performance (TR and efficiency) and gradient performance (maximum gradient strength and slew rate) for several imaging scenarios, including multi-echo sequences, to determine the optimum matching of maximum gradient strength and slew rate for gradient hardware designs. For standard modern gradient hardware (40 mT/m and 150 mT/m/ms), we found that the maximum gradient strength is more than adequate for the imaging resolution that is commonly encountered with rapid scouting (3 mm x 4 mm x 10 mm voxel). It is well matched for typical CINE and real-time cardiac imaging applications (1.5 mm x 2 mm x 6 mm voxel), and is inadequate for optimal matching with slew rate for high-resolution applications such as musculoskeletal imaging (0.5 x 0.8 x 3 mm voxel). For the lower-resolution methods, efficiency could be improved with higher slew rates; this provokes interest in designing methods for limiting dB/dt peripherally while achieving high switching rates in the imaging field of view. The use of multi-echo SSFP acquisitions leads to substantial improvements in sequence performance (i.e., increased efficiency and shorter TR).
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Affiliation(s)
- Scott B Reeder
- Department of Radiology, Stanford University Medical Center, Stanford, California 94304, USA.
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McGee KP, Debbins JP, Boskamp EB, Blawat L, Angelos L, King KF. Cardiac magnetic resonance parallel imaging at 3.0 Tesla: technical feasibility and advantages. J Magn Reson Imaging 2004; 19:291-7. [PMID: 14994296 DOI: 10.1002/jmri.20015] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To quantify changes in signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), specific absorption rate (SAR), RF power deposition, and imaging time in cardiac magnetic resonance imaging with and without the application of parallel imaging at 1.5 T and 3.0 T. MATERIALS AND METHODS Phantom and volunteer data were acquired at 1.5 T and 3.0 T with and without parallel imaging. RESULTS Doubling field strength increased phantom SNR by a factor of 1.83. In volunteer data, SNR and CNR values increased by factors of 1.86 and 1.35, respectively. Parallel imaging (reduction factor = 2) decreased phantom SNR by a factor of 1.84 and 2.07 when compared to the full acquisition at 1.5 T and 3.0 T, respectively. In volunteers, SNR and CNR decreased by factors of 2.65 and 2.05 at 1.5 T and 1.99 and 1.75 at 3.0 T, respectively. Doubling the field strength produces a nine-fold increase in SAR (0.0751 to 0.674 W/kg). Parallel imaging reduced the total RF power deposition by a factor of two at both field strengths. CONCLUSIONS Parallel imaging decreases total scan time at the expense of SNR and CNR. These losses are compensated at higher field strengths. Parallel imaging is effective at reducing total power deposition by reducing total scan time.
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Affiliation(s)
- Kiaran P McGee
- Department of Radiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
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96
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Gold GE, Reeder SB, Beaulieu CF. Advanced MR imaging of the shoulder: dedicated cartilage techniques. Magn Reson Imaging Clin N Am 2004; 12:143-59, vii. [PMID: 15066598 DOI: 10.1016/j.mric.2004.01.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Garry E Gold
- Department of Radiology, Stanford University, 300 Pasteur Drive SO-68B, Stanford, CA 94305-5105, USA.
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97
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Markl M, Reeder SB, Chan FP, Alley MT, Herfkens RJ, Pelc NJ. Steady-state free precession MR imaging: improved myocardial tag persistence and signal-to-noise ratio for analysis of myocardial motion. Radiology 2004; 230:852-61. [PMID: 14990847 DOI: 10.1148/radiol.2303030181] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Tagging with balanced steady-state free-precession (SSFP) magnetic resonance (MR) imaging by using a steady-state storage scheme for myocardial motion analysis was evaluated. Signal-to-noise ratio (SNR), blood-tissue contrast, and tag persistence in volunteers and phantoms showed improved performance of SSFP imaging with tagging compared with that of radiofrequency spoiled gradient-echo (SPGR) MR imaging with tagging. Choice of flip angle with SSFP imaging involved a trade-off among SNR, blood-tissue contrast, and tag persistence. Increased SNR and tag persistence can be achieved simultaneously with SSFP imaging compared with SPGR tagging methods. As a result, the proposed technique may be useful for analysis of diastolic ventricular function.
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Affiliation(s)
- Michael Markl
- Department of Radiology, Stanford University, Lucas MRI/S Center, 1201 Welch Rd, Rm P 284, Palo Alto, CA 94304, USA.
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98
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Markl M, Alley MT, Elkins CJ, Pelc NJ. Flow effects in balanced steady state free precession imaging. Magn Reson Med 2004; 50:892-903. [PMID: 14586999 DOI: 10.1002/mrm.10631] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
An analysis of the effect of flow on 2D fully balanced steady state free precession (SSFP) imaging is presented. Transient and steady-state SSFP signal intensities in the presence of steady and pulsatile flow were simulated using a matrix formalism based on the Bloch equations. Various through-plane flow waveforms and rates were modeled numerically considering factors such as the excitation slice profile and both in- and out-flow effects. Phantom measurements in an experimental setup that allowed the assessment of SSFP signal properties as a function of frequency offset and flow rate demonstrated that the computer simulations provided a suitable description of the effects of flow in SSFP imaging. A volunteer scan was performed to provide in vivo validations. For accurate modeling of SSFP signal intensities it is crucial to include effects such as imperfect slice profiles and, more importantly, "out-of-slice" contributions to the signal. Both simulations and experiments show that there can be considerably large-frequency offset dependent-signal contributions from flowing spins that have already left the imaging slice but still add to the SSFP signal. Although spins leaving the slice do not experience additional RF-excitation, gradient activity is not confined to the region of excitations and the balanced nature of the SSFP imaging gradients allows "out-of-slice" transverse magnetization to contribute to the total SSFP signal, effectively by broadening the slice thickness for flowing spins. This results in a frequency dependence of in-flow related signal enhancement and flow artifacts.
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Affiliation(s)
- M Markl
- Department of Radiology, Stanford University, Stanford, California 94304, USA.
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99
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Miller KL, Hargreaves BA, Lee J, Ress D, deCharms RC, Pauly JM. Functional brain imaging using a blood oxygenation sensitive steady state. Magn Reson Med 2004; 50:675-83. [PMID: 14523951 DOI: 10.1002/mrm.10602] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Blood oxygenation level dependent (BOLD) functional MRI (fMRI) is an important method for functional neuroimaging that is sensitive to changes in blood oxygenation related to brain activation. While BOLD imaging has good spatial coverage and resolution relative to other neuroimaging methods (such as positron emission tomography (PET)), it has significant limitations relative to other MRI techniques, including poor spatial resolution, low signal levels, limited contrast, and image artifacts. These limitations derive from the coupling of BOLD functional contrast to sources of image degradation. This work presents an alternative method for fMRI that may over-come these limitations by establishing a blood oxygenation sensitive steady-state (BOSS) that inverts the signal from deoxygenated blood relative to the water signal. BOSS fMRI allows the imaging parameters to be optimized independently of the functional contrast, resulting in fewer image artifacts and higher signal-to-noise ratio (SNR). In addition, BOSS fMRI has greater functional contrast than BOLD. BOSS fMRI requires careful shimming and multiple acquisitions to obtain a precise alignment of the magnetization to the SSFP frequency response.
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Affiliation(s)
- Karla L Miller
- Department of Electrical Engineering, Stanford University, Stanford, California 94305-9510, USA.
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100
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Kornaat PR, Doornbos J, van der Molen AJ, Kloppenburg M, Nelissen RG, Hogendoorn PCW, Bloem JL. Magnetic resonance imaging of knee cartilage using a water selective balanced steady-state free precession sequence. J Magn Reson Imaging 2004; 20:850-6. [PMID: 15503345 DOI: 10.1002/jmri.20194] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To compare an optimized water selective balanced steady-state free precession sequence (WS-bSSFP) with conventional magnetic resonance (MR) sequences in imaging cartilage of osteoarthritic knees. MATERIALS AND METHODS Flip angles of sagittal and axial WS-bSSFP sequences were optimized in three volunteers. Subsequently, the knees of 10 patients with generalized osteoarthritis were imaged using sagittal and axial WS-bSSFP and conventional MR imaging techniques. We calculated contrast-to-noise ratios (CNR) between cartilage and its surrounding tissues to quantitatively analyze the various sequences. Using dedicated software we compared, in two other patients, the accuracy of cartilage volume measurements with anatomic sections of the tibial plateau. RESULTS CNRtotal eff (CNR efficiency between cartilage and its surrounding tissue) using WS-bSSFP was maximal with a 20-25 degrees flip angle. CNRtotal eff was higher in WS-bSSFP than in conventional images: 6.1 times higher compared to T1-weighted gradient echo (GE) images, 5.1 compared to proton-density (PD) fast spin echo (FSE) images, and 4.8 compared to T2-weighted FSE images. The mean difference of cartilage volume measurement on WS-bSSFP and anatomic sections was 0.06 mL compared to 0.24 mL for T1-GE and anatomic sections. CONCLUSION A WS-bSSFP sequence is superior to conventional MR imaging sequences in imaging cartilage of the knee in patients with osteoarthritis.
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Affiliation(s)
- Peter R Kornaat
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
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