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Fathi Kazerooni A, Pozo JM, McCloskey EV, Saligheh Rad H, Frangi AF. Diffusion MRI for Assessment of Bone Quality; A Review of Findings in Healthy Aging and Osteoporosis. J Magn Reson Imaging 2020; 51:975-992. [PMID: 31709670 PMCID: PMC7078977 DOI: 10.1002/jmri.26973] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 09/25/2019] [Accepted: 09/26/2019] [Indexed: 01/13/2023] Open
Abstract
Diffusion MRI (dMRI) is a growing imaging technique with the potential to provide biomarkers of tissue variation, such as cellular density, tissue anisotropy, and microvascular perfusion. However, the role of dMRI in characterizing different aspects of bone quality, especially in aging and osteoporosis, has not yet been fully established, particularly in clinical applications. The reason lies in the complications accompanied with implementation of dMRI in assessment of human bone structure, in terms of acquisition and quantification. Bone is a composite tissue comprising different elements, each contributing to the overall quality and functional competence of bone. As diffusion is a critical biophysical process in biological tissues, early changes of tissue microstructure and function can affect diffusive properties of the tissue. While there are multiple MRI methods to detect variations of individual properties of bone quality due to aging and osteoporosis, dMRI has potential to serve as a superior method for characterizing different aspects of bone quality within the same framework but with higher sensitivity to early alterations. This is mainly because several properties of the tissue including directionality and anisotropy of trabecular bone and cell density can be collected using only dMRI. In this review article, we first describe components of human bone that can be potentially detected by their diffusivity properties and contribute to variations in bone quality during aging and osteoporosis. Then we discuss considerations and challenges of dMRI in bone imaging, current status, and suggestions for development of dMRI in research studies and clinics to segregate different contributing components of bone quality in an integrated acquisition. Level of Evidence: 5 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:975-992.
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Affiliation(s)
- Anahita Fathi Kazerooni
- Department of Radiology, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Jose M. Pozo
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, School of Computing and School of MedicineUniversity of LeedsLeedsUK
| | - Eugene Vincent McCloskey
- Department of Oncology & Metabolism, Mellanby Centre for Bone Research, Centre for Integrated research in Musculoskeletal AgeingUniversity of SheffieldSheffieldUK
| | - Hamidreza Saligheh Rad
- Quantitative MR Imaging and Spectroscopy Group, Research Center for Molecular and Cellular ImagingTehran University of Medical SciencesTehranIran
- Department of Medical Physics and Biomedical EngineeringTehran University of Medical SciencesTehranIran
| | - Alejandro F. Frangi
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, School of Computing and School of MedicineUniversity of LeedsLeedsUK
- LICAMM Leeds Institute of Cardiovascular and Metabolic Medicine, School of MedicineUniversity of LeedsLeedsUK
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Chen H, Cai S, Chen Z. A method for longitudinal relaxation time measurement in inhomogeneous fields. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2017; 281:118-124. [PMID: 28586739 DOI: 10.1016/j.jmr.2017.05.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 05/13/2017] [Accepted: 05/16/2017] [Indexed: 06/07/2023]
Abstract
The spin-lattice relaxation time (T1) plays a crucial role in the study of spin dynamics, signal optimization and data quantification. However, the measurement of chemical shift-specific T1 constants is hampered by the magnetic field inhomogeneity due to poorly shimmed external magnetic fields or intrinsic magnetic susceptibility heterogeneity in samples. In this study, we present a new protocol to determine chemical shift-specific T1 constants in inhomogeneous fields. Based on intermolecular double-quantum coherences, the new method can resolve overlapped peaks in inhomogeneous fields. The measurement results are in consistent with the measurements in homogeneous fields using the conventional method. Since spatial encoding technique is involved, the experimental time for the new method is very close to that for the conventional method. With the aid of T1 knowledge, some concealed information can be exploited by T1 weighting experiments.
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Affiliation(s)
- Hao Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, Fujian 361005, China
| | - Shuhui Cai
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, Fujian 361005, China.
| | - Zhong Chen
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, Fujian 361005, China
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Bao J, Cui X, Huang Y, Zhong J, Chen Z. Resolution enhancement in MR spectroscopy of red bone marrow fat via intermolecular double-quantum coherences. Phys Med Biol 2015; 60:6391-406. [DOI: 10.1088/0031-9155/60/16/6391] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Wong CK. Probing of susceptibility structures through the distant dipolar field effect. Magn Reson Imaging 2013; 31:797-809. [DOI: 10.1016/j.mri.2013.03.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 03/21/2013] [Accepted: 03/21/2013] [Indexed: 11/30/2022]
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Shen G, Cai C, Chen Z, Cai S. Intermolecular double-quantum coherence imaging without coherence selection gradients and its application in in vivo MRI. Magn Reson Imaging 2013; 31:515-23. [DOI: 10.1016/j.mri.2012.10.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 09/20/2012] [Accepted: 10/30/2012] [Indexed: 11/26/2022]
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Stokes AM, Wilson JW, Warren WS. Characterization of restricted diffusion in uni- and multi-lamellar vesicles using short distance iMQCs. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 223:31-40. [PMID: 22975234 PMCID: PMC3594806 DOI: 10.1016/j.jmr.2012.07.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 07/30/2012] [Accepted: 07/31/2012] [Indexed: 06/01/2023]
Abstract
Improved understanding of the entrapment, transport, and release of drugs and small molecules within vesicles is important for drug delivery. Most methods rely on contrast agents or probe molecules; here, we propose a new MRI method to detect signal from water spins with restricted diffusion. This method is based on intermolecular double quantum coherences (iDQCs), which can probe the restricted diffusion characteristics at well-defined and tunable microscopic distance scales. By using an exceedingly short (and previously inaccessible) distance, the iDQC signal arises only from restricted diffusion spins and thereby provides a mechanism to directly image vesicle entrapment, transport, and release. Using uni- and multi-lamellar liposomes and polymersomes, we show how the composition, lamellar structure, vesicle size, and concentration affects the iDQC signal between coupled water spins at very short separation distances. The iDQC signal correlates well with conventional diffusion MRI and a proposed biexponential (multicompartmental) diffusion model. Finally, the iDQC signal was used to monitor dynamic changes in the lamellar structure as temperature-sensitive liposomes released their contents. These short distance iDQCs can probe the amount and diffusion of water entrapped in vesicles, which may be useful to further understand vesicle properties in materials science and drug delivery applications.
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Affiliation(s)
- A M Stokes
- Department of Chemistry and Center for Molecular and Biomolecular Imaging, Duke University, Durham, NC 27708, USA
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Mintzopoulos D, Ackerman JL, Song YQ. MRI of trabecular bone using a decay due to diffusion in the internal field contrast imaging sequence. J Magn Reson Imaging 2012; 34:361-71. [PMID: 21780229 DOI: 10.1002/jmri.22612] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
PURPOSE To characterize the DDIF (Decay due to Diffusion in the Internal Field) method using intact animal trabecular bone specimens of varying trabecular structure and porosity, under ex vivo conditions closely resembling in vivo physiological conditions. The DDIF method provides a diffusion contrast which is related to the surface-to-volume ratio of the porous structure of bones. DDIF has previously been used successfully to study marrow-free trabecular bone, but the DDIF contrast hitherto had not been tested in intact specimens containing marrow and surrounded by soft tissue. MATERIALS AND METHODS DDIF imaging was implemented on a 4.7 Tesla (T) small-bore, horizontal, animal scanner. Ex vivo results on fresh bone specimens containing marrow were obtained at body temperature. Control measurements were carried out in surrounding tissue and saline. RESULTS Significant DDIF effect was observed for trabecular bone samples, while it was considerably smaller for soft tissue outside the bone and for lipids. Additionally, significant differences were observed between specimens of different trabecular structure. CONCLUSION The DDIF contrast is feasible despite the reduction of the diffusion constant and of T(1) in such conditions, increasing our confidence that DDIF imaging in vivo may be clinically viable for bone characterization.
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Affiliation(s)
- Dionyssios Mintzopoulos
- Athinoula A Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
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Wong CK. Theoretical analysis of the sensitivity of dipolar field signal to local field variations by perturbative expansion of the magnetization. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 203:29-43. [PMID: 20022774 DOI: 10.1016/j.jmr.2009.11.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 11/24/2009] [Accepted: 11/24/2009] [Indexed: 05/28/2023]
Abstract
A perturbation method based on the integral form of the Bloch equation is used to calculate the distant dipolar field (DDF) signal formed by the correlation spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED) sequence in the presence of a susceptibility-induced field. The properties of the DDF signal are analyzed through the series expansion of the magnetization, and the first order DDF result is applied to study the use of the DDF effect to probe sub-voxel field distributions. Numerical calculations are carried out with the sub-voxel field distributions modeled by rectangular tubes of uniform frequency shifts (the block model) and cylinders of a finite susceptibility difference (the blood vessel model) using the parameters for brain at 9.4T. The DDF signal is found to exhibit features arising from the sub-voxel structures.
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Mishkovsky M, Eliav U, Navon G, Frydman L. Nearly 10(6)-fold enhancements in intermolecular (1)H double-quantum NMR experiments by nuclear hyperpolarization. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 200:142-146. [PMID: 19574073 DOI: 10.1016/j.jmr.2009.06.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2009] [Revised: 05/28/2009] [Accepted: 06/02/2009] [Indexed: 05/28/2023]
Abstract
Intermolecular Multiple-Quantum Coherences (iMQCs) can yield interesting NMR information of high potential usefulness in spectroscopy and imaging - provided their associated sensitivity limitations can be overcome. A recent study demonstrated that ex situ dynamic nuclear polarization (DNP) could assist in overcoming sensitivity problems for iMQC-based experiments on (13)C nuclei. In the present work we show that a similar approach is possible when targeting the protons of a hyperpolarized solvent. It was found that although the DNP procedure enhances single-quantum (1)H signals by about 600, which is significantly less than in optimized low-gamma liquid-state counterparts, the non-linear dependence of iMQC-derived signals on polarization can yield very large enhancements approaching 10(6). Cleary no practical amount of data averaging can match this kind of sensitivity gains. The fact that DNP endows iMQC-based (1)H NMR spectra with a sensitivity that amply exceeds that of their thermally polarized single-quantum counterpart, is confirmed in a number of simple single-scan 2D imaging experiments.
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Affiliation(s)
- Mor Mishkovsky
- Chemical Physics Department, Weizmann Institute, 76100 Rehovot, Israel
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Sigmund EE, Cho H, Song YQ. High-resolution MRI of internal field diffusion-weighting in trabecular bone. NMR IN BIOMEDICINE 2009; 22:436-448. [PMID: 19023866 DOI: 10.1002/nbm.1354] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Trabecular bone structure is known to play a crucial role in the overall strength, and thus fracture risk, of such areas of the skeleton as the vertebrae, spine, femur, tibiae, or radius. Several MR methods devoted to probing this structure depend upon the susceptibility difference between the solid bone matrix and the intervening fluid/marrow/fat, usually in the context of a linewidth (1/T(2)') measurement or mapping technique. A recently demonstrated new approach to this system involves using internal gradients to encode diffusion weighting, and extracting structural information (e.g., surface-to-volume ratio) from the resulting signal decay. This contrast method has been demonstrated in bulk measurements on cleaned, water-saturated bovine trabecular bone samples. In the present work, microscopic imaging (0.156 mm in-plane resolution) is performed in order to spatially resolve this contrast on the trabecular level, and confirm its interpretation for the bulk measurements. It is found that the local rate of decay due to diffusion in the internal field (DDIF) is maximal close to the trabecular surfaces. The overall decay rate in a lower resolution scan probes the abundance of these surfaces, and provides contrast beyond that found in conventional proton density weighted or T(1)-weighted imaging. Furthermore, a microscopic calculation of internal field distributions shows a qualitative distinction between the structural sensitivities of DDIF and T(2)'. DDIF contrast is highly localized around trabecular walls than is the internal field itself, making it a less sensitive but more specific measure of such important properties as trabecular number.
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Affiliation(s)
- E E Sigmund
- Department of Radiology, New York University, 660 First Avenue, New York, New York 10016, USA.
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11
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Schneider JT, Faber C. BOLD imaging in the mouse brain using a turboCRAZED sequence at high magnetic fields. Magn Reson Med 2009; 60:850-9. [PMID: 18816869 DOI: 10.1002/mrm.21716] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Functional MRI (fMRI) based on the detection of intermolecular double-quantum coherences (iDQC) has previously been shown to provide pronounced activation signal. For fMRI in small animals at very high magnetic fields, the essential fast gradient echo-based readout methods become problematic. Here, rapid intermolecular double-quantum coherence (iDQC) imaging was implemented, combining the iDQC preparation sequence with a Turbo spin echo-like readout. Four-step phase cycling and a novel intensity-ordered k-space encoding scheme with separate acquisition of odd and even echoes were essential to optimize signal to noise ratio efficiency. Compared with a single echo readout of iDQC signal, acceleration of factor 16 was achieved in phantoms using the novel method at 17.6 Tesla. In vivo, echo trains consisting of 32 echoes were possible and images of the mouse brain were obtained in 30 s. The blood oxygen level dependent (BOLD) effect in the mouse brain upon change of breathing gas was observed as average signal change of (6.3 +/- 1.1)% in iDQC images. Signal changes in conventional multi spin echo images were (4.4 +/- 2.3)% and (8.3 +/- 3.8)% with gradient echo methods. Combination of T(2)*-weighting with the fast iDQC sequence may yield higher signal changes than with either method alone, and establish fast iDQC imaging a robust tool for high field fMRI in small animals.
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Ling W, Eliav U, Navon G, Jerschow A. Chemical exchange saturation transfer by intermolecular double-quantum coherence. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 194:29-32. [PMID: 18571444 PMCID: PMC2562429 DOI: 10.1016/j.jmr.2008.05.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Revised: 05/20/2008] [Accepted: 05/22/2008] [Indexed: 05/11/2023]
Abstract
A number of contrast enhancement effects based on the use of intermolecular multiple-quantum coherences, or distant dipolar field effects are known. This phenomenon is characterized by the dependence on the mth power of the initial magnetization (where m is the coherence order used). In this paper, we describe the contrast enhancement based on chemical exchange saturation transfer and NOE, which is achieved by the use of intermolecular double-quantum coherences (iDQC). The method was validated using clinically relevant systems based on glycosaminoglycans and a sample of cartilage tissue, showing that the CEST contrast, as well as, NOE are enhanced by iDQC.
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Affiliation(s)
- Wen Ling
- Chemistry Department, New York University, New York, NY 10003
| | - Uzi Eliav
- School of Chemistry, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Gil Navon
- School of Chemistry, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Alexej Jerschow
- Chemistry Department, New York University, New York, NY 10003
- corresponding author, Alexej Jerschow, Chemistry Department, New York University, New York, NY 10003, Phone: 212 998 8451, Fax: 212 260 7905, E-mail:
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Mertens P, Machann J, Mueller-Bierl B, Steidle G, Bellemann ME, Schick F. Magnetic field distribution in the presence of paramagnetic plates in magnetic resonance imaging: a combined numerical and experimental study. Med Phys 2008; 35:1777-84. [PMID: 18561652 DOI: 10.1118/1.2896079] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The amount and geometric distribution of paramagnetic components in tissue is considered as the basis of T2*-weighted magnetic resonance imaging (MRI). Such techniques are routinely applied for assessment of iron in parenchymal organs such as the liver (hemosiderosis). Furthermore, susceptibility sensitive MRI is discussed as an alternative method to x-ray techniques for quantitative assessment of paramagnetic spongy bone components in patients with osteoporosis. The presented work is dedicated to systematically examining the possible influences of macroscopic arrangements of paramagnetic plates on the magnetic field. In a theoretical approach magnetic field distribution was simulated applying decomposition of the plates in single dipoles. Plate size and distances between parallel plates, as well as plate orientation with respect to the static field, were varied for these numerical simulations. Experiments on corresponding plate arrangements were carried out on a 3 T whole body MR scanner using the field-sensitive MR sequence technique for B0 field mapping. Further examinations were carried out on a bone preparation of the femur, where T2* maps were measured and analyzed on a pixel-by-pixel basis at two orientations with respect to the static field. A series of experiments were performed using isotropic and anisotropic volume elements in three-dimensional gradient echo sequences. Resulting magnetic field distributions in the experimentally recorded B0 field maps were in good agreement with the numerical simulations. Field distortions dominated in areas close to the plates and especially near the edges. Those areas showed strong local field gradients, leading to pronounced signal dephasing effects. The examination of the bone preparations revealed different T2* values for identical regions in the bone when the orientation of the bone or the pixel geometry was changed with respect to the magnetic field. Those effects amounted to nearly 70% (22.9 ms versus 13.6 ms in a region of interest in the femur) for 90 degrees rotation of the femur in the magnetic fields. The orientation of anisotropic picture elements with constant size also showed a strong influence on the derived T2* value (up to 80%, increasing with anisotropy of picture elements).
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Affiliation(s)
- Philipp Mertens
- Section on Experimental Radiology, University of Tuebingen, Hoppe-Seyler-Strasse 3, Tuebingen, 72076 Germany
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Eliav U, Navon G. Enhancement of magnetization transfer effects by inter-molecular multiple quantum filtered NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 190:149-153. [PMID: 17936657 DOI: 10.1016/j.jmr.2007.09.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Accepted: 09/22/2007] [Indexed: 05/25/2023]
Abstract
There are a number of methods that give MRI contrasts based on changes of the water M(z) magnetization as a result of magnetization transfer to macromolecules. In the present work we report that a combination of these methods with inter-molecular multiple quantum coherences (iMQC) gives enhanced effects. For the magnetization transfer contrast (MTC) method an effect of (M(z)/M(0)) becomes (M(z)/M(0))(l) where l is the rank of the tensors constituting the iMQC. A similar trend was found upon combining iMQC with the Goldman-Shen experiment. It is pointed out that the method is general for all magnetization transfer methods, including the nuclear Overhauser effect.
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Affiliation(s)
- Uzi Eliav
- School of Chemistry, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
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15
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Wehrli FW. Structural and functional assessment of trabecular and cortical bone by micro magnetic resonance imaging. J Magn Reson Imaging 2007; 25:390-409. [PMID: 17260403 DOI: 10.1002/jmri.20807] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Osteoporosis is a multifactorial disorder of bone mineral homeostasis affecting the elderly. It is a major public health issue with significant socioeconomic consequences. Recent findings suggest that bone loss-the key manifestation of the disease-is accompanied by architectural deterioration, both affecting the bone's mechanical competence and susceptibility to fracture. This article reviews the potential of quantitative micro MRI (mu-MRI), including a discussion of the technical requirements for image acquisition, processing, and analysis for assessing the architectural implications of osteoporosis and as a means to monitor the response to treatment. With current technology, the resolution achievable in clinically acceptable scan times and necessary signal-to-noise ratio (SNR) is comparable to trabecular thickness. This limited spatial resolution regime demands processing and analysis algorithms designed to operate under such limiting conditions. It is shown that three different classes of structural parameters can be distinguished, characterizing scale, topology, and orientation. There is considerable evidence that osteoporotic bone loss affects all three classes but that topological changes, resulting from conversion of trabecular plates to rods, with the latter's eventual disconnection, are particularly prominent. Clinical applications discussed can be divided into those dealing with assessment of osteoporotic fracture risk as opposed to the study of the effect of disease progression and regression in response to treatment. Current data suggest that noninvasive assessment of cortical and trabecular bone (TB) architecture by mu-MRI may provide new surrogate endpoints to assess the efficacy of intervention in osteoporosis treatment and prevention.
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Affiliation(s)
- Felix W Wehrli
- Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA.
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Sigmund E, Cho H, Chen P, Byrnes S, Song YQ, Guo X, Brown TR. Diffusion-based MR methods for bone structure and evolution. Magn Reson Med 2007; 59:28-39. [DOI: 10.1002/mrm.21281] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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17
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Wehrli FW, Song HK, Saha PK, Wright AC. Quantitative MRI for the assessment of bone structure and function. NMR IN BIOMEDICINE 2006; 19:731-64. [PMID: 17075953 DOI: 10.1002/nbm.1066] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Osteoporosis is the most common degenerative disease in the elderly. It is characterized by low bone mass and structural deterioration of bone tissue, leading to morbidity and increased fracture risk in the hip, spine and wrist-all sites of predominantly trabecular bone. Bone densitometry, currently the standard methodology for diagnosis and treatment monitoring, has significant limitations in that it cannot provide information on the structural manifestations of the disease. Recent advances in imaging, in particular MRI, can now provide detailed insight into the architectural consequences of disease progression and regression in response to treatment. The focus of this review is on the emerging methodology of quantitative MRI for the assessment of structure and function of trabecular bone. During the past 10 years, various approaches have been explored for obtaining image-based quantitative information on trabecular architecture. Indirect methods that do not require resolution on the scale of individual trabeculae and therefore can be practiced at any skeletal location, make use of the induced magnetic fields in the intertrabecular space. These fields, which have their origin in the greater diamagnetism of bone relative to surrounding marrow, can be measured in various ways, most typically in the form of R2', the recoverable component of the total transverse relaxation rate. Alternatively, the trabecular network can be quantified by high-resolution MRI (micro-MRI), which requires resolution adequate to at least partially resolve individual trabeculae. Micro-MRI-based structure analysis is therefore technically demanding in terms of image acquisition and algorithms needed to extract the structural information under conditions of limited signal-to-noise ratio and resolution. Other requirements that must be met include motion correction and image registration, both critical for achieving the reproducibility needed in repeat studies. Key clinical applications targeted involve fracture risk prediction and evaluation of the effect of therapeutic intervention.
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Affiliation(s)
- Felix W Wehrli
- Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA.
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Faber C, Heil C, Zahneisen B, Balla DZ, Bowtell R. Sensitivity to local dipole fields in the CRAZED experiment: an approach to bright spot MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 182:315-24. [PMID: 16714128 DOI: 10.1016/j.jmr.2006.05.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Revised: 04/04/2006] [Accepted: 05/01/2006] [Indexed: 05/09/2023]
Abstract
Local dipole fields such as those created by small iron-oxide particles are used to produce regions of low intensity (dark contrast) in many molecular magnetic resonance imaging applications. We have investigated, with computer simulations and experiments at 17.6 T, how the COSY revamped with asymmetric z-gradient echo detection (CRAZED) experiment that selects intermolecular double-quantum coherences can also be used to visualize such local dipole fields. Application of the coherence-selection gradient pulses parallel to the main magnetic field produced similar, dark contrast as conventional gradient echo imaging. Application of the gradient along the magic angle leads to total loss of signal intensity in homogeneous samples. In the presence of local dipole fields, the contrast was inverted and bright signals from the dipoles were observed over a very low background. Both simulations and experiments showed that the signal strongly decreased when a phase-cycle suppressing single-quantum coherences was employed. Therefore, we conclude that most of the signal comes from directly refocused magnetization or intermolecular single-quantum coherences. Finally, we demonstrate that bright contrast from local dipole fields can also be obtained, when the pair of coherence-selection gradient pulses is deliberately mismatched. Both methods allowed visualization of local dipole fields in phantoms in experimental times of about 3 min.
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Affiliation(s)
- Cornelius Faber
- Department of Experimental Physics 5, University of Würzburg, 97074 Würzburg, Germany.
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Zheng B, Chen Z, Kennedy SD, Zhong J. iDQC MRI weighted by longitudinal relaxation in the rotating frame. Magn Reson Med 2006; 56:327-33. [PMID: 16826606 DOI: 10.1002/mrm.20954] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A long-duration, low-power, off-resonance spin-locking pulse was incorporated into the COSY revamped by asymmetric z gradient-echo detection (CRAZED) pulse sequence in order to evaluate the effects of intermolecular double-quantum longitudinal relaxation in the tilted rotating frame (T1rho,DQ(eff)). This modified CRAZED sequence was followed by a standard fast spin-echo imaging sequence to form images with T1rho,DQ(eff)-weighted contrast. Imaging experiments were performed on an agarose-gel phantom and mouse-tail tissue at 600 MHz. Experimental results demonstrated the feasibility of imaging applications based on T1rho,DQ(eff) as a novel contrast mechanism, and showed that iDQC off-resonance longitudinal relaxation in the rotating frame T1rho,DQ(eff) is sensitive to the tilt angle theta and the effective spin-locking field omegae. Imaging based on T1rho,DQ(eff)) has reduced RF power deposition compared to on-resonance spin-locking, which is advantageous for human applications.
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Affiliation(s)
- Bingwen Zheng
- Department of Physics, State Key Laboratory of Physical Chemistry of Solid Surface, Xiamen University, Xiamen, People's Republic of China
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Bouchard LS, Warren WS. Multiple-quantum vector field imaging by magnetic resonance. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2005; 177:9-21. [PMID: 16087374 DOI: 10.1016/j.jmr.2005.06.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2005] [Revised: 06/25/2005] [Accepted: 06/29/2005] [Indexed: 05/03/2023]
Abstract
We introduce a method for non-invasively mapping fiber orientation in materials and biological tissues using intermolecular multiple-quantum coherences. The nuclear magnetic dipole field of water molecules is configured by a CRAZED sequence to encode spatial distributions of material heterogeneities. At any given point r in space, we obtain the spherical coordinates of fiber orientation (theta,phi) with respect to the external field by comparing three signals ||G(X)||, ||(Y)||, and ||G(Z)|| (modulus), acquired with linear gradients applied along the X, Y, and Z axes, respectively. For homogeneous isotropic materials, a subtraction ||G(Z)|| - ||G(X)|| - ||G(Y)|| gives zero. With anisotropic materials, we find an empirical relationship relating ||G(Z)|| - ||G(X)|| - ||G(Y)||/(||G(X)|| + ||G(Y)|| + ||G(Z)||) to the polar angle theta, while ||G(X|| - ||G(Y)||/(||G(X)|| + ||G(Y)|| + ||G(Z)||) is related to the azimuthal angle phi. Experiments in structured media confirm the structural sensitivity. This technique can probe length scales not accessible by conventional MRI and diffusion tensor imaging.
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