High‐resolution variable flip angle 3D MR imaging of trabecular microstructure <i>in vivo</i>

Jara, Hernán; Wehrli, Félix W.; Chung, Hsiao‐Wen; Ford, John C.

doi:10.1002/mrm.1910290415

Cited by 139 publications

(64 citation statements)

References 27 publications

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“…6(a), the signal attenuation resulting from this effect is caused by the intra-voxel field distribution across the imaging voxel [eqn (2)]. Since the gradients are largest near the TBbone-marrow interface, local phase dispersion generates blurring and artifactually enlarged trabeculae (86,87,90). In FGRE, phase dispersion-induced signal attenuation increases linearly with echo time TE.…”

Section: Image Acquisition Techniquesmentioning

confidence: 99%

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Quantitative MRI for the assessment of bone structure and function

et al. 2006

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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 R 0 2 , the recoverable component of the total transverse relaxation rate. Alternatively, the trabecular network can be quantified by high-resolution MRI (m-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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Section: Image Acquisition Techniquesmentioning

confidence: 99%

“…Rather than selecting a low flip angle (the Ernst angle, a E ) as a means to minimize saturation as in gradient echo imaging, its 1808 complement is chosen (1808 -a E ). This is the fundamental principle of the FLASE (fast large-angle spin echo) by Ma et al (87) and its precursor, RASEE (90,93).…”

Section: Image Acquisition Techniquesmentioning

confidence: 99%

Quantitative MRI for the assessment of bone structure and function

et al. 2006

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“…In vitro studies performed on small cubic specimens have shown that some of the parameters derived from high-resolution MR images contributed to the prediction of biomechanical properties of bone (16). In the last decade, numerous studies have also demonstrated the feasibility of MR micro-imaging of trabecular structure in humans in vivo at a resolution adequate for visualizing trabecular bone (17,18).…”

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confidence: 99%

Magnetic resonance imaging of normal and osteoarthritic trabecular bone structure in the human knee

Beuf¹,

Ghosh²,

Newitt³

et al. 2002

Arthritis & Rheumatism

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Objective. To use high-resolution magnetic resonance imaging (MRI) to evaluate the trabecular bone structure in the distal femur and the proximal tibia and its to correlate the findings with different stages of osteoarthritis (OA) of the human knee.Methods. Axial images of the distal femur and proximal tibia were obtained at 1.5 T in patients without and with mild OA and with severe OA. The spatial resolution was 195 ؋ 195 m 2 with a 1-mm slice thickness. Apparent measures of trabecular bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular separation (Tb.Sp), and trabecular thickness (Tb.Th) were calculated.Results. Significant differences existed in the trabecular bone structure of the femur and tibia. Differences in trabecular bone structure between the tibia and the femur decreased with the degree of OA. The apparent BV/TV, Tb.N, and Tb.Sp in the femoral condyles could be used to differentiate healthy patients or patients with mild OA from patients with severe OA (P < 0.05). Among individuals, the structural variation of the lateral and medial femoral condyle was indicative of the extent of the disease.Conclusion. High-resolution MRI of the knee joint can provide a noninvasive assessment of trabecular bone structure. Trabecular bone structure, determined by high-resolution MRI, shows significant variation in patients with varying degrees of OA. The impact of OA on trabecular bone is different in the tibia than in the femur, and this difference depends on the extent of the disease.Osteoarthritis (OA) is a multifactorial disease characterized by the progressive loss of articular hyaline cartilage and the development of altered joint congruency, subchondral sclerosis, intraosseous cysts, and osteophytes. It affects about 14% of the adult population (1) and is the second most common cause of permanent disability among subjects over the age of 50 years (2). In addition to changes in articular cartilage that occur in OA, it has been suggested that early changes are seen in the adjoining subchondral and trabecular bone (3).In a guinea pig model, Layton et al (4) observed with microscopic computed tomography (CT) that an initial loss of trabecular bone volume fraction and thinning of trabeculae was followed, in the advanced stages of OA, by an increase of trabecular bone volume fraction via eventual thickening of trabeculae. In a canine OA model induced by anterior cruciate ligament (ACL) transection, Dedrick et al (5) demonstrated an increase in subchondral bone thickness, accompanied by a decrease in trabecular thickness. Using magnification radiographs of humans, Lynch et al (6) showed an increase in the horizontal trabecular thickness of the tibia in early OA, followed by an increase in vertical connectivity of trabeculae in advanced disease. More recently, Buckland-Wright and colleagues (7) showed that the structural changes in the trabecular bone microarchitecture in patients with ACL ruptures are detectable by fractal analysis of radiographs, well before joint space narrowing and other radiologic ...

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“…[7] Note that the T 2 decay is less for the main echo since the magnetization generating it spends half as much time in the transverse plane as the magnetization forming the artifactual echo. The magnitude, ⑀, of the latter relative to the main echo is the absolute value of the ratio of expression [6] over [7]:…”

Section: Coherence Pathway Of Artifactual Signalmentioning

confidence: 99%

“…Strong susceptibility-induced gradients as well as the multiple spectral components of triacyl glycerides in fatty bone marrow cause dephasing that diminishes the marrow signal. At the interface with the trabeculae the susceptibility-induced local gradients lead to signal loss that causes the trabeculae to appear artifactually thickened in the reconstructed image (7). In a spin-echo sequence, the signal loss caused by local susceptibilityinduced gradients is fully recovered and the isochromats from the various spectral components of fat are rephased at k-space center.…”

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confidence: 99%

Coherence‐induced artifacts in large‐flip‐angle steady‐state spin‐echo imaging

Vasilic

Song

Wehrli

2004

Magnetic Resonance in Med

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High-resolution imaging of trabecular bone aimed at analyzing the bone's microarchitecture is preferably performed with spinecho-type pulse sequences. Unlike gradient echoes, spin-echoes are immune to artifactual broadening of trabeculae caused by local static field gradients near the bone-bone marrow interface and signal loss from chemical shift dephasing at kspace center. However, the previously practiced 3D fast largeangle spin-echo (FLASE) pulse sequence was found to be prone to a low-frequency modulation artifact in both the readout and slice direction. The artifact is caused by deviations in the effective flip angle of the nonselective 180°pulse, which converts a fraction of the phase-encoded transverse magnetization to longitudinal magnetization. The latter recurs as transverse magnetization in the subsequent pulse sequence cycle forming a spurious stimulated echo. There is growing evidence that the mechanical competence of trabecular bone (the type of bone in which the majority of osteoporotic fractures occur), and thus its resistance to fracture, is significantly determined by the bone's architectural make-up (1-5). In vivo MR microimaging has proven its potential for assessing the bone's 3D structure. Nevertheless, obtaining reproducible structural parameters strongly depends on achieving artifact-free images in a resolution regime on the order of 100 -150 m (6).The magnetic properties of bone and the chemical composition of bone marrow pose stringent requirements on pulse sequences appropriate for MR microimaging of trabecular bone. Strong susceptibility-induced gradients as well as the multiple spectral components of triacyl glycerides in fatty bone marrow cause dephasing that diminishes the marrow signal. At the interface with the trabeculae the susceptibility-induced local gradients lead to signal loss that causes the trabeculae to appear artifactually thickened in the reconstructed image (7). In a spin-echo sequence, the signal loss caused by local susceptibilityinduced gradients is fully recovered and the isochromats from the various spectral components of fat are rephased at k-space center. These two reasons make spin-echo type sequences particularly well suited for imaging trabecular bone. However, patient comfort and the large number of pulse sequence cycles inherent to 3D imaging put limits on the allowable repetition time, TR.Two previous publications from this laboratory introduced 3D FLASE (fast large-angle spin echo), a pulse sequence optimized for the purpose of imaging trabecular bone (8,9). The pulse sequence has been used in prior trabecular bone imaging studies (5,10) and is an integral element of the virtual bone biopsy (6). 3D FLASE is a large-flip-angle, 3D spin-echo sequence, shown in Fig. 1a). The fundamental principle of FLASE is the dual function of the 180°pulse that serves both for phase-reversal and for restoration of the inverted longitudinal magnetization created by the initial excitation pulse. A slice-selective excitation with a flip angle of 140°, used in 3D FLASE give...

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High‐resolution variable flip angle 3D MR imaging of trabecular microstructure in vivo

Cited by 139 publications

References 27 publications

Quantitative MRI for the assessment of bone structure and function

Quantitative MRI for the assessment of bone structure and function

Magnetic resonance imaging of normal and osteoarthritic trabecular bone structure in the human knee

Coherence‐induced artifacts in large‐flip‐angle steady‐state spin‐echo imaging

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