Density of organic matrix of native mineralized bone measured by water‐ and fat‐suppressed proton projection MRI

Wu, Yaotang; Ackerman, Jerome L.; Chesler, David A.; Graham, Lila; Wang, Yan; Glimcher, Melvin J.

doi:10.1002/mrm.10512

Cited by 117 publications

(130 citation statements)

References 38 publications

(51 reference statements)

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“…The k-space was parsed using a 3-dimensional radial trajectory. The missing region at the center of k-space was filled with a second radial acquisition, with a reduced number of spokes and bandwidth, similar to the so-called water-and fat-suppressed proton projection MRI method (24). Before reconstruction, the 2 acquisitions were merged with a linear transition in the overlap region, to prevent the formation of artifacts.…”

Section: Data Acquisitionmentioning

confidence: 99%

Clinical Evaluation of Zero-Echo-Time MR Imaging for the Segmentation of the Skull

Delso¹,

et al. 2015

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MR-based attenuation correction is instrumental for integrated PET/ MR imaging. It is generally achieved by segmenting MR images into a set of tissue classes with known attenuation properties (e.g., air, lung, bone, fat, soft tissue). Bone identification with MR imaging is, however, quite challenging, because of the low proton density and fast decay time of bone tissue. The clinical evaluation of a novel, recently published method for zero-echo-time (ZTE)-based MR bone depiction and segmentation in the head is presented here. Methods: A new paradigm for MR imaging bone segmentation, based on proton density-weighted ZTE imaging, was disclosed earlier in 2014. In this study, we reviewed the bone maps obtained with this method on 15 clinical datasets acquired with a PET/CT/MR trimodality setup. The CT scans acquired for PET attenuation-correction purposes were used as reference for the evaluation. Quantitative measurements based on the Jaccard distance between ZTE and CT bone masks and qualitative scoring of anatomic accuracy by an experienced radiologist and nuclear medicine physician were performed. Results: The average Jaccard distance between ZTE and CT bone masks evaluated over the entire head was 52% ± 6% (range, 38%-63%). When only the cranium was considered, the distance was 39% ± 4% (range, 32%-49%). These results surpass previously reported attempts with dualecho ultrashort echo time, for which the Jaccard distance was in the 47%-79% range (parietal and nasal regions, respectively). Anatomically, the calvaria is consistently well segmented, with frequent but isolated voxel misclassifications. Air cavity walls and bone/fluid interfaces with high anatomic detail, such as the inner ear, remain a challenge. Conclusion: This is the first, to our knowledge, clinical evaluation of skull bone identification based on a ZTE sequence. The results suggest that proton density-weighted ZTE imaging is an efficient means of obtaining high-resolution maps of bone tissue with sufficient anatomic accuracy for, for example, PET attenuation correction.

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Section: Data Acquisitionmentioning

confidence: 99%

Clinical Evaluation of Zero-Echo-Time MR Imaging for the Segmentation of the Skull

Delso¹,

et al. 2015

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“…Typical minimum TE values for clinical scanners, which depend on the RF transmit-receive switching and settling times, are 40-200 ms (12), while the shortest TE reported is 8 ms (13). In order to achieve a better delineation of the morphology within short T 2 tissues, several long T 2 suppression techniques have been developed, including dual echo subtraction techniques (1,5,14), and long T 2 preparation clusters using either long-duration hard pulses (15)(16)(17) or adiabatic pulses (12,18) to saturate or invert long T 2 tissues.…”

mentioning

confidence: 99%

Optimization of RF excitation to maximize signal and T₂ contrast of tissues with rapid transverse relaxation

Carl¹,

Bydder

et al. 2010

Magnetic Resonance in Med

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Ultrashort echo time MRI requires specialized pulse sequences to overcome the short T 2 of the MR signal encountered in tissues such as ligaments, tendon, or cortical bone. Theoretical work is presented, supported by simulations and experimental data on optimizing the radiofrequency excitation to maximize signal-to-noise ratio and contrast-to-noise ratio. The theoretical calculations and simulations are based on the classic Bloch equations and lead to a closed form expression for the optimal radiofrequency pulse parameters to maximize the MR signal in the presence of rapid T 2 decay. In the steady state, the spoiled gradient recalled echo signal amplitude in response to the radiofrequency excitation pulses is not maximized by the classic Ernst angle but by a more general criterion we call ''generalized Ernst angle.'' Finally, it is shown that T 2 contrast is maximized by flipping the magnetization at the Ernst angle with a radiofrequency pulse duration proportional to the targeted T 2 . Experimental studies on short T 2 phantoms confirm these optimization criteria for both signal-to-noise ratio and contrast-to-noise ratio. Clinical MRI is predominantly geared toward long T 2 species (greater than a few milliseconds). However, tissues containing highly ordered structures such as ligaments (T 2 % 4-10 ms), tendons (T 2 % 2 ms), or cortical bone (T 2 % 0.5 ms) appear dark in images acquired using clinical MR sequences (1,2). This is because the minimum echo times (TEs) for spin echo and gradient echo sequences are approximately 8-10 ms and 1-2 ms, respectively (2). Anomalies in such tissues typically only become apparent when pathology leads to increased signal (e.g., edema) set against the dark signal from short T 2 tissues.With the development of ultrashort TE (UTE) sequences, one is able to directly visualize tissues containing highly ordered structures (1-7). Other potential applications of UTE are imaging of the lung parenchyma, brain, or liver (8-11). Imaging short T 2 tissues is achieved in UTE by acquiring the free induction decay of the MR signal as soon after the end of the radiofrequency (RF) pulse as possible. This is typically accomplished by using a radial center-out k-space trajectory and data sampling of only a few hundred microseconds. Magnitude images are then reconstructed from the (regridded) k-space data. For the special case of UTE imaging, the time between the end of the RF pulse and the beginning of the read gradient (k ¼ 0) is typically defined in the literature as the TE (see for example Rahmer et al. (5)). Typical minimum TE values for clinical scanners, which depend on the RF transmit-receive switching and settling times, are 40-200 ms (12), while the shortest TE reported is 8 ms (13). In order to achieve a better delineation of the morphology within short T 2 tissues, several long T 2 suppression techniques have been developed, including dual echo subtraction techniques (1,5,14), and long T 2 preparation clusters using either long-duration hard pulses (15-17) or adiabatic pulses (12,18)...

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“…There are also free induction decay (FID)-based techniques, where a radial line of k-space is acquired from the centre out [31]. This can be coupled with long T 2 water and fat suppression to selectively image short T 2 components as water-and fatsuppressed proton projection imaging (WASPI) [32]. Other trajectories in k-space are possible, including a stack of spirals (SOS) [33] and echo planar imaging (EPI).…”

Section: Tissue Fluid and Materials Propertiesmentioning

confidence: 99%

The Agfa Mayneord lecture: MRI of short and ultrashortT₂andT₂* components of tissues, fluids and materials using clinical systems

Bydder¹

2011

BJR

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ABSTRACT. A variety of techniques are now available to directly or indirectly detect signal from tissues, fluids and materials that have short, ultrashort or supershort T 2 or T 2 * components. There are also methods of developing image contrast between tissues and fluids in the short T 2 or T 2 * range that can provide visualisation of anatomy, which has not been previously seen with MRI. Magnetisation transfer methods can now be applied to previously invisible tissues, providing indirect access to supershort T 2 components. Particular methods have been developed to target susceptibility effects and quantify them after correcting for anatomical distortion. Specific methods have also been developed to image the effects of magnetic iron oxide particles with positive contrast. Major advances have been made in techniques designed to correct for loss of signal and gross image distortion near metal. These methods are likely to substantially increase the range of application for MRI.

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Density of organic matrix of native mineralized bone measured by water‐ and fat‐suppressed proton projection MRI

Cited by 117 publications

References 38 publications

Clinical Evaluation of Zero-Echo-Time MR Imaging for the Segmentation of the Skull

Clinical Evaluation of Zero-Echo-Time MR Imaging for the Segmentation of the Skull

Optimization of RF excitation to maximize signal and T₂ contrast of tissues with rapid transverse relaxation

The Agfa Mayneord lecture: MRI of short and ultrashortT₂andT₂* components of tissues, fluids and materials using clinical systems

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Density of organic matrix of native mineralized bone measured by water‐ and fat‐suppressed proton projection MRI

Cited by 117 publications

References 38 publications

Clinical Evaluation of Zero-Echo-Time MR Imaging for the Segmentation of the Skull

Clinical Evaluation of Zero-Echo-Time MR Imaging for the Segmentation of the Skull

Optimization of RF excitation to maximize signal and T2 contrast of tissues with rapid transverse relaxation

The Agfa Mayneord lecture: MRI of short and ultrashortT2andT2* components of tissues, fluids and materials using clinical systems

Contact Info

Product

Resources

About

Optimization of RF excitation to maximize signal and T₂ contrast of tissues with rapid transverse relaxation

The Agfa Mayneord lecture: MRI of short and ultrashortT₂andT₂* components of tissues, fluids and materials using clinical systems