T1? imaging using magnetization-prepared projection encoding (MaPPE)

Nugent, Allison C.; Johnson, G. Allan

doi:10.1002/(sici)1522-2594(200003)43:3<421::aid-mrm14>3.0.co;2-x

Cited by 13 publications

(14 citation statements)

References 28 publications

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“…First, T 1 is longer than T 2 (e.g., see Refs. 11,12), resulting in slower dephasing and better SNR than traditional T 2 -weighted images (13). Second, when T 1 is long T 1 is also long.…”

Section: Discussionsupporting

confidence: 91%

“…Thus, the very long T 1 of the blood relative to tissue makes T 1 particularly suitable for providing blood/tissue contrast. Third, as the spin-locking field is present during the entire procedure it will, if large enough, effectively overwhelm susceptibility-induced gradients (8,13). Finally, Engelhardt and Johnson (11) have shown in muscle and liver tissue of mice embryos, and in agar samples, that T 1 increases with the strength of the locking field B 1 .…”

Section: Discussionmentioning

confidence: 99%

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MR angiography using spin‐lock flow tagging

Azhari¹,

McKenzie²,

Edelman³

2001

Magn. Reson. Med.

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A method for MR angiography using an RF labeling technique is suggested. The method utilizes a slice-selective spin-lock pulse sequence for tagging the spins of inflowing blood. The pulse sequence begins with a spatially selective 90°x RF pulse, followed by a nonselective composite locking pulse of 135°y ؊ n[360°y]-135°y and by a 90°-x pulse. A spoiler gradient is then applied. A rapid imaging stage, which yields a T 1 -weighted signal from the tagged spins, completes the sequence. Untagged spins are thoroughly dephased and consequently suppressed in the image. Thus, contrast is obtained without an injection of a contrast material or image subtraction. Furthermore, the flow of the tagged bolus can be visualized. The sequence was implemented on phantoms and on human volunteers using a 1.5T scanner. Magnetic resonance angiography (MRA) offers a noninvasive alternative to X-ray angiography. MRA techniques are ordinarily divided into "black blood" and "bright blood" and the latter is further subdivided into techniques which either use or do not use an exogenous contrast material. Magnetization-prepared MRA are noncontrast bright blood techniques. While enhancement by a contrast material usually offers high SNR, there are also several disadvantages, e.g., the inconvenience caused to the patient by the injection procedure, the cost of the contrast agent, and some restrictions on repeated use. Magnetization-prepared techniques, on the other hand, offer a more attractive noninterventional alternative.Several techniques for magnetization-prepared MRA have been suggested. The one most frequently used in the clinic is probably the time of flight (TOF) (1). With this technique, signal contrast is obtained by the inflow of unsaturated spins. Thus, contrast level depends on the flow rate and on the length of the blood vessel within the imaged plane. Consequently, in-plane and retrograde flow may be difficult to visualize with TOF (2) (when saturation bands are used).A flow-independent magnetization-prepared MRA has also been suggested by Brittain et al. (2). With this technique the problem noted above is avoided and slow flow regions, as well as in-plane and retrograde flow, can be depicted. However, temporal information and quantitative information on flow rate and direction are not available.Flow imaging by bolus tagging has the potential to provide information on flow rates and directions as well as on the anatomy of the studied vessels. A selective inversion recovery method was suggested by Nishimura et al. (3) in 1988. With this technique, upstream blood is tagged by an inversion excitation and then allowed to flow into the imaged region. The signal from the selectively tagged blood is obtained by subtraction of this first image from a second image, acquired without the tagging.A technique for flow imaging by bolus tagging, using stimulated echoes, has also been suggested (4) and implemented to image coronary artery flow in mice and rats (5,6). The stimulated echo sequence produces a signal which depends on both T 1 and ...

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“…First, T 1 is longer than T 2 (e.g., see Refs. 11,12), resulting in slower dephasing and better SNR than traditional T 2 -weighted images (13). Second, when T 1 is long T 1 is also long.…”

Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

MR angiography using spin‐lock flow tagging

Azhari¹,

McKenzie²,

Edelman³

2001

Magn. Reson. Med.

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“…The measured T 1 values of Agar phantoms in this study were consistent with the values in previously published studies (32,33). T 1 decreased as Agar concentration increased, but no obvious T 1 dispersion was seen with spin-lock frequencies ranging from 300 Hz to 700 Hz.…”

Section: Discussionmentioning

confidence: 99%

“…The T 1 values obtained with imaging methods were systematically lower than those obtained with spectroscopy methods. This may be due to imperfections in gradients and RF pulses, B 1 inhomogeneity (33), and signal loss due to T 2 relaxation caused by imperfect spin-locking in imaging protocol, or T1-weight due to subtraction error during RF-cycling in the imaging protocol. The approximately parallel trend of T 1 values versus Agar concentration between these two methods, especially for Agar phantoms with concentration from 2% to 4% that have similar T 1 as in vivo knee cartilage, implies that the T 1 quantification using the developed imaging method is a robust measurement for in vivo cartilage relaxation time.…”

Section: Discussionmentioning

confidence: 99%

In vivo 3T spiral imaging based multi‐slice T_1ρ mapping of knee cartilage in osteoarthritis

Han

Benjamin

et al. 2005

Magnetic Resonance in Med

151

162

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T 1 describes the spin-lattice relaxation in the rotating frame and has been proposed for detecting damage to the cartilage collagen-proteoglycan matrix in osteoarthritis. In this study, a multi-slice T 1 imaging method for knee cartilage was developed using spin-lock techniques and a spiral imaging sequence. The adverse effect of T 1 regrowth during the multi-slice acquisition was eliminated by RF cycling. Agarose phantoms with different concentrations, 10 healthy volunteers, and 9 osteoarthritis patients were scanned at 3T. T 1 values decreased as agarose concentration increased. T 1 values obtained with imaging methods were compared with those obtained with spectroscopic methods. T 1 values obtained during multi-slice acquisition were validated with those obtained in a single slice acquisition. Reproducibility was assessed using the average coefficient of variation of median T 1 , which was 0.68% in phantoms and 4.8% in healthy volunteers. There was a significant difference (P ‫؍‬ 0.002) in the average T 1 within patellar and femoral cartilage between controls (45.04 ؎ 2.59 ms) and osteoarthritis patients (53.06 ؎ 4.60 ms). A significant correlation was found between T 1 and T 2 ; however, the difference of T 2 was not significant between controls and osteoarthritis pa- Osteoarthritis (OA) is a prevalent degenerative joint disease, with radiographic evidence seen in at least 70% of the population over age 65 (1). OA is characterized by the progressive loss of hyaline articular cartilage; however, cartilage loss and OA symptoms are preceded significantly by damage to the collagen-proteoglycan (PG) matrix and elevation of cartilage water content (2). Therefore, a sensitive technology for detecting structural and functional changes in the early stages of OA would be valuable for preventing the progression of disease and for therapeutic monitoring. Magnetic resonance imaging (MRI) has an ever-increasing role in the diagnosis and monitoring of OA due to its multiplanar capabilities, high spatial resolution without ionizing radiation, and superior contrast between joint tissues (3,4). In addition to quantifying changes in cartilage morphology, including thickness and volume (5-7), recent studies have shown the potential of MR parameters to reflect changes in biochemical composition of cartilage with early OA. These techniques include T 2 quantification (8,9), T 1 quantification (10,11), diffusionweighted imaging (12), and delayed gadolinium enhanced MRI of cartilage (dGEMRIC) (13,14).The T 1 parameter describes the spin-lattice relaxation in the rotating frame (15). It probes the slow motion interactions between motionally restricted water molecules and their local macromolecular environment, and therefore provides unique biomedical information in the low frequency regime, typically from a few hundred hertz to a few kilohertz. The extracellular matrix (ECM) in articular cartilage restricts the motion of water molecules. Changes to the ECM, such as PG loss, therefore, may be reflected in measurements of T 1 . Since ...

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“…A series of T 1ρ and T 2 -weighted images was acquired with a 3D GRE sequence with T 1ρ or T 2 magnetization preparation, respectively [22][23][24][25]. The imaging parameters were: TR/TE = 80/2.96 ms, flip angle = 20°, field-of-view = 68 × 68 mm 2 , slice thickness = 3 mm, matrix = 96 × 192, nominal voxel size = 0.7 × 0.35 × 3 mm 3 , number of slices = 10, acquisition bandwidth = 260 Hz/pixel, and acquisition time of 2 min.…”

Section: T 1ρ and T 2 Measurementsmentioning

confidence: 99%

Assessment of T1, T1ρ, and T2 values of the ulnocarpal disc in healthy subjects at 3 tesla

Rauscher

Bender

Grözinger

et al. 2014

Magnetic Resonance Imaging

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T1? imaging using magnetization-prepared projection encoding (MaPPE)

Cited by 13 publications

References 28 publications

MR angiography using spin‐lock flow tagging

MR angiography using spin‐lock flow tagging

In vivo 3T spiral imaging based multi‐slice T_1ρ mapping of knee cartilage in osteoarthritis

Assessment of T1, T1ρ, and T2 values of the ulnocarpal disc in healthy subjects at 3 tesla

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T1? imaging using magnetization-prepared projection encoding (MaPPE)

Cited by 13 publications

References 28 publications

MR angiography using spin‐lock flow tagging

MR angiography using spin‐lock flow tagging

In vivo 3T spiral imaging based multi‐slice T1ρ mapping of knee cartilage in osteoarthritis

Assessment of T1, T1ρ, and T2 values of the ulnocarpal disc in healthy subjects at 3 tesla

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In vivo 3T spiral imaging based multi‐slice T_1ρ mapping of knee cartilage in osteoarthritis