Three‐dimensional T<sub>1ρ</sub>‐weighted MRI at 1.5 Tesla

Borthakur, Arijitt; Wheaton, Andrew J.; Charagundla, Sridhar R.; Shapiro, Erik M.; Regatte, Ravinder R.; Akella, Sarma V.S.; Kneeland, J. Bruce; Reddy, Ravinder

doi:10.1002/jmri.10296

Cited by 58 publications

(60 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, there are limits on the duration of the SL pulse based on the maximum RF energy permitted during clinical imaging (16). This energy is reported as the specific absorption rate (SAR), and was calculated a priori according to Collins et al (17) and monitored by the scanner during the experiments as part of a routine protocol (18). Another variation of the SLEPI sequence that is currently under development reduces SAR by eliminating both /2 pulses.…”

Section: Discussionmentioning

confidence: 99%

A pulse sequence for rapid in vivo spin‐locked MRI

Borthakur

Hulvershorn

Gualtieri

et al. 2006

Magnetic Resonance Imaging

Self Cite

View full text Add to dashboard Cite

Purpose: To develop a novel pulse sequence called spinlocked echo planar imaging (EPI), or (SLEPI), to perform rapid T 1 -weighted MRI. Materials and Methods:SLEPI images were used to calculate T 1 maps in two healthy volunteers imaged on a 1.5-T Sonata Siemens MRI scanner. The head and extremity coils were used for imaging the brain and blood in the popliteal artery, respectively.Results: SLEPI-measured T 1 was 83 msec and 103 msec in white (WM) and gray matter (GM), respectively, 584 msec in cerebrospinal fluid (CSF), and was similar to values obtained with the less time-efficient sequence based on a turbo spin-echo readout. T 1 was 183 msec in arterial blood at a spin-lock (SL) amplitude of 500 Hz. Conclusion:We demonstrate the feasibility of the SLEPI pulse sequence to perform rapid T 1 MRI. The sequence produced images of higher quality than a gradient-echo EPI sequence for the same contrast evolution times. We also discuss applications and limitations of the pulse sequence. T 1⌹ OR "SPIN-LOCKED" MRI produces contrast unlike conventional T 1 -or T 2 -weighted images. Spin-locking is achieved by the application of a low power on-resonance radiofrequency (RF) pulse to the magnetization in the transverse plane. The resulting MR signal decays with a time constant T 1 and is dominated by processes that occur with a correlation time, c , that is related to the amplitude of the spin-lock (SL) pulse (␥B 1 /2 ), which typically ranges from zero to a few kilohertz. T 1 is commonly referred to as the longitudinal relaxation time constant in the rotating frame. In biological tissues, T 1 increases with higher B 1 and approaches T 2 , the spin-spin relaxation time constant, as the amplitude of the SL pulse is reduced to zero. The sensitivity of T 1 to low-frequency interactions facilitates the study of biological tissues in a manner that is unattainable by conventional T 1 -and T 2 -based MR methods. Consequently, T 1 MRI has been used to investigate a variety of tissues such as breast, brain, and cartilage (1-3).Recently, T 1 imaging has been employed to measure blood flow and oxygen metabolism and the effect of tracers such as H 2 17 O (4,5). These studies were performed using standard spin-echo, turbo (fast) spinecho, or gradient-echo-based pulse sequences. There is substantial evidence demonstrating that the T 1 relaxation time parameter is sensitive to the early detection of cerebral ischemia (6 -8). Kettunen et al (9) revealed a linear dependence of T 1 as a function of oxygen saturation in experiments performed in vitro. Dynamic studies such as these and others that involve imaging of flowing spins such as that of blood would benefit from a fast T 1 imaging technique that is able to acquire images in the order of tens of milliseconds.A method of rapid image acquisition is the echo planar imaging (EPI) technique (10,11). In its conventional form, the EPI pulse sequence consists of an excitation pulse that is followed by a train of gradientechoes within a single pulse repetition time (TR), and is capable of generat...

show abstract

Section: Discussionmentioning

confidence: 99%

A pulse sequence for rapid in vivo spin‐locked MRI

Borthakur

Hulvershorn

Gualtieri

et al. 2006

Magnetic Resonance Imaging

Self Cite

View full text Add to dashboard Cite

show abstract

“…Previous methods of generating T 1 -weighted contrast with a spin-lock pulse sequence have been limited to 2D singleslice (7,22) or 3D gradient-echo (11,27) acquisitions. The development of a clinical version of the MS-SL sequence allows for volumetric coverage of an entire anatomic object with the high SNR advantages of a spin-echo-based readout.…”

Section: Discussionmentioning

confidence: 99%

In vivo quantification of T_1ρ using a multislice spin‐lock pulse sequence

Wheaton

Borthakur

Kneeland

et al. 2004

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

A multislice spin-lock (MS-SL) pulse sequence is implemented on a clinical scanner to acquire multiple images with spin-lockgenerated contrast of the knee joints of six healthy human subjects. The MS-SL sequence produces images with T 1 contrast with an additional factor of intrinsic T 2 weighting, which hinders direct measurement of T 1 . A method is presented to compensate the MS-SL-generated data with regard to T 2 in an effort to accurately calculate multislice T 1 maps in a feasible experimental time. The T 2 -compensated multislice T 1 maps produced errors in the measurement of T 1 in healthy patellar cartilage of ϳ5% compared to the gold standard measurement of T 1 acquired with single-slice spin-lock pulse sequence. The MS-SL sequence has potential as an important clinical tool for the acquisition of multislice T 1 -weighted images and/or quantitative multislice T 1 maps.

show abstract

“…Three-dimensional T 1r mapping of human knee cartilage was performed at 1.5 T on both healthy and symptomatic osteoarthritic subjects (180,236). Average T 1r values (at spin locking amplitude of 440 Hz) obtained from eight healthy volunteers (all male with age range 22-45 years) with three-dimensional T 1r mapping was 49.7 AE 3.2 ms (mean AE SD) and that obtained from two-dimensional T 1r mapping was 48.5 AE 2.6 ms (mean AE SD).…”

Section: Experimental T 1r Studiesmentioning

confidence: 99%

Sodium and T_1ρ MRI for molecular and diagnostic imaging of articular cartilage

et al. 2006

Self Cite

View full text Add to dashboard Cite

In this article, both sodium magnetic resonance (MR) and T 1r relaxation mapping aimed at measuring molecular changes in cartilage for the diagnostic imaging of osteoarthritis are reviewed. First, an introduction to structure of cartilage, its degeneration in osteoarthritis (OA) and an outline of diagnostic imaging methods in quantifying molecular changes and early diagnostic aspects of cartilage degeneration are described. The sodium MRI section begins with a brief overview of the theory of sodium NMR of biological tissues and is followed by a section on multiple quantum filters that can be used to quantify both bi-exponential relaxation and residual quadrupolar interaction. Specifically, (i) the rationale behind the use of sodium MRI in quantifying proteoglycan (PG) changes, (ii) validation studies using biochemical assays, (iii) studies on human OA specimens, (iv) results on animal models and (v) clinical imaging protocols are reviewed. Results demonstrating the feasibility of quantifying PG in OA patients and comparison with that in healthy subjects are also presented. The section concludes with the discussion of advantages and potential issues with sodium MRI and the impact of new technological advancements (e.g. ultra-high field scanners and parallel imaging methods). In the theory section on T 1r , a brief description of (i) principles of measuring T 1r relaxation, (ii) pulse sequences for computing T 1r relaxation maps, (iii) issues regarding radio frequency power deposition, (iv) mechanisms that contribute to T 1r in biological tissues and (v) effects of exchange and dipolar interaction on T 1r dispersion are discussed. Correlation of T 1r relaxation rate with macromolecular content and biomechanical properties in cartilage specimens subjected to trypsin and cytokineinduced glycosaminoglycan depletion and validation against biochemical assay and histopathology are presented. Experimental T 1r data from osteoarthritic specimens, animal models, healthy human subjects and as well from osteoarthritic patients are provided. The current status of T 1r relaxation mapping of cartilage and future directions is also discussed. Copyright # 2006 John Wiley & Sons, Ltd. KEYWORDS: cartilage; arthritis; spin-lock; T1rho; sodium; MRI OSTEOARTHRITIS Osteoarthritis (OA) affects more than half of the population above the age of 65 (1,2) and has a significant negative impact on the quality of life of elderly individuals (3). The economic costs in the USA from OA have been estimated to be more than 1% of the gross domestic product (4). OA is now increasingly viewed as a metabolically active joint disorder of diverse etiologies. The biochemistry of the disease is characterized by the following changes in cartilage: reduced proteoglycan (PG) concentration, possible changes in the size of collagen fibril and aggregation of PG, increased water content and increased rate of synthesis and degradation of matrix macromolecules. The earliest changes in the cartilage due to OA result in a partial breakdown in the proteoglyc...

show abstract

Three‐dimensional T_1ρ‐weighted MRI at 1.5 Tesla

Cited by 58 publications

References 32 publications

A pulse sequence for rapid in vivo spin‐locked MRI

A pulse sequence for rapid in vivo spin‐locked MRI

In vivo quantification of T_1ρ using a multislice spin‐lock pulse sequence

Sodium and T_1ρ MRI for molecular and diagnostic imaging of articular cartilage

Contact Info

Product

Resources

About

Three‐dimensional T1ρ‐weighted MRI at 1.5 Tesla

Cited by 58 publications

References 32 publications

A pulse sequence for rapid in vivo spin‐locked MRI

A pulse sequence for rapid in vivo spin‐locked MRI

In vivo quantification of T1ρ using a multislice spin‐lock pulse sequence

Sodium and T1ρ MRI for molecular and diagnostic imaging of articular cartilage

Contact Info

Product

Resources

About

Three‐dimensional T_1ρ‐weighted MRI at 1.5 Tesla

In vivo quantification of T_1ρ using a multislice spin‐lock pulse sequence

Sodium and T_1ρ MRI for molecular and diagnostic imaging of articular cartilage