A novel fast T1‐mapping method

Tong, Chong Wen; Prato, Frank S.

doi:10.1002/jmri.1880040513

Cited by 43 publications

(32 citation statements)

References 22 publications

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“…However, when optimized, the Look-Locker sampling scheme appears to be extremely efficient (2,5,23). TAPIR, being based on the Look-Locker technique, inherits the above-mentioned attributes of its predecessors.…”

Section: Discussionmentioning

confidence: 99%

Error reduction and parameter optimization of the TAPIR method for fast T₁ mapping

Zaitsev¹,

Steinhoff²,

Shah³

2003

Magnetic Resonance in Med

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A methodology is presented for the reduction of both systematic and random errors in T 1 determination using TAPIR, a Look-Locker-based fast T 1 mapping technique. The relations between various sequence parameters were carefully investigated in order to develop recipes for choosing optimal sequence parameters. Theoretical predictions for the optimal flip angle were verified experimentally. Inversion pulse imperfections were identified as the main source of systematic errors in T 1 determination with TAPIR. An effective remedy is demonstrated which includes extension of the measurement protocol to include a special sequence for mapping the inversion efficiency itself. Measurement of the spin-lattice relaxation time constant, T 1 , using MRI is becoming increasingly popular in such different applications as quantitative tracer kinetics (1-3), radiation dosimetry (4), and the response of tumors to therapy (5). The recent increasing interest in T 1 mapping in vivo is largely associated with scanner hardware improvements and the development of faster, more accurate imaging methods. Thus, a number of techniques which were previously either too demanding on the hardware or which required unacceptably long acquisition times have now developed into clinically useful methods (6 -11). Recent developments in the field have been reviewed by Kingsley in an annotated bibliography (12).In an effort to circumvent the major limitations of current methodology, we have developed a technique, based on the Look-Locker approach, and have demonstrated its potential (13-15). The method, termed TAPIR (T 1 mapping with partial inversion recovery), uses a magnetization-preparation scheme similar to that employed by Deichmann et al. (6). Additionally, TAPIR utilizes readout gradient reversals to acquire multiple lines of k-space following a single excitation pulse. Subsequently, the acquired data are reordered to fill k-space bands (segments). Interleaving slices and time-points on the recovery curve affords the acquisition of multiple slices with practically no additional time penalty. The TAPIR pulse sequence diagram is presented in Fig. 1 and is described fully in the figure caption. The multislice, multitime-point data acquisition capabilities inherent to TAPIR are in contrast to many of the previous techniques. The principle of interleaving slices and time points is extremely efficient in terms of data collection and enables the recovery curve to be sampled with a higher apparent temporal resolution than the IR-EPI technique, snapshot FLASH method, or the segmented snapshot FLASH technique. The overall speed of the sequence is enhanced not only by the rapid repetition of the sampling RF pulses, but also by minimizing the dead time and by the acquisition of multiple echoes following each excitation pulse. The relatively long recovery time for in vivo applications is used to facilitate multislice acquisition, which confers the advantage that whole-brain coverage can be achieved, as desired for human brain segmentation, for instance.The u...

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Section: Discussionmentioning

confidence: 99%

Error reduction and parameter optimization of the TAPIR method for fast T₁ mapping

Zaitsev¹,

Steinhoff²,

Shah³

2003

Magnetic Resonance in Med

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“…The recent interest in methods for fast T 1 mapping (1)(2)(3)(4)(5), particularly in the human brain, highlights the increased desire for more quantitative in vivo measurements using MRI. For example, in multiple sclerosis the number of "black-holes" on T 1 -weighted scans has shown some correlation with disease severity (6).…”

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confidence: 99%

Rapid T₁ mapping using multislice echo planar imaging

Clare

Jezzard

2001

Magnetic Resonance in Med

119

128

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Determination of neurological pathology in white matter disease can be made in a semiquantitative way from T 1 -or T 2 -weighted images. A higher level of quantification based on measured T 1 or T 2 values has been either limited to specific regions of interest or to low-resolution maps. Higher-resolution T 1 maps have proved difficult to obtain due to the excessively long scan times required using conventional techniques. In this study, clinically acceptable images are obtained by using single-shot echo planar imaging (EPI) with an acquisition scheme that maximizes signal-to-noise while minimizing the scan time. The recent interest in methods for fast T 1 mapping (1-5), particularly in the human brain, highlights the increased desire for more quantitative in vivo measurements using MRI. For example, in multiple sclerosis the number of "black-holes" on T 1 -weighted scans has shown some correlation with disease severity (6). However, hypointensity on a conventional MR scan is not an objective measure, and results can be difficult to compare between research sites, due to variations in the sequence parameters used and the subjective criterion used by the person interpreting the scan. The use of T 1 mapping as a more quantitative approach has many attractions, as the value of T 1 may report more about the underlying pathology than does visual interpretation of T 1 -weighted scans (7).The main reason for T 1 maps not being used more routinely is the lengthy time it can take to obtain such maps using conventional methods. The standard inversion recovery pulse sequence involves considerable delays in the period between inversion and excitation pulses (8). This has limited T 1 maps to a few low-resolution slices, often with acquisition times of greater than 1 hr. To be clinically useful, T 1 maps need to cover a large volume of the brain with good resolution, and be acquired in scan times of minutes rather than hours.A considerable increase in the speed of T 1 mapping can be achieved by implementing the Look-Locker method (9). This method uses many low flip angle acquisitions to inspect a single recovery curve following an inversion pulse, thereby reducing the need for long delays between several inversions. The Look-Locker method (and other variants) greatly reduces the time taken to measure T 1 ; however, there are some penalties, notably in reduced signal-to-noise and in the sensitivity of the T 1 fit to the flip angle used for the excitation pulses. A combination of EPI and the Look-Locker approach (LL-EPI) probably represents the fastest T 1 mapping sequence that can be achieved, with a T 1 recovery curve from a single slice being acquired in 3 sec (10). Clearly, though, this method has the same inherent problems as the conventional LookLocker approach.Here we use an approach that uses EPI together with a more conventional [invert]-TI-[excite] strategy. This enables accurate whole brain, T 1 mapping to be carried out in only 3 min. METHODSAll experiments were carried out on a 3.0 Tesla whole body scanner with a V...

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“…Derivatives of the Look-Locker (LL) method (e.g., TOMROP and T 1 -FARM) also suffer somewhat from errors due to uncertainties in B 1 (32,33). Such errors in the LL methods can be reduced by using small flip angles for the pulses that sample the recovering magnetization, but this directly reduces the signal-to-noise ratio of the data (34). In addition, the LL techniques are complex to implement and have not been widely tested.…”

Section: Discussionmentioning

confidence: 97%

Accurate and rapid quantitative dynamic contrast-enhanced breast MR imaging using spoiled gradient-recalled echoes and bookend T1 measurements

1999

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A novel fast T1‐mapping method

Cited by 43 publications

References 22 publications

Error reduction and parameter optimization of the TAPIR method for fast T₁ mapping

Error reduction and parameter optimization of the TAPIR method for fast T₁ mapping

Rapid T₁ mapping using multislice echo planar imaging

Accurate and rapid quantitative dynamic contrast-enhanced breast MR imaging using spoiled gradient-recalled echoes and bookend T1 measurements

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A novel fast T1‐mapping method

Cited by 43 publications

References 22 publications

Error reduction and parameter optimization of the TAPIR method for fast T1 mapping

Error reduction and parameter optimization of the TAPIR method for fast T1 mapping

Rapid T1 mapping using multislice echo planar imaging

Accurate and rapid quantitative dynamic contrast-enhanced breast MR imaging using spoiled gradient-recalled echoes and bookend T1 measurements

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Product

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Error reduction and parameter optimization of the TAPIR method for fast T₁ mapping

Error reduction and parameter optimization of the TAPIR method for fast T₁ mapping

Rapid T₁ mapping using multislice echo planar imaging