Nuclear magnetic resonance imaging: contrast-to-noise ratio as a function of strength of magnetic field

Hart, H.R.; Bottomley, PA; Edelstein, William A.; Karr, S. G.; Leue, WM; Mueller, O.; Rw, Redington; Schenck, JF; Smith, L.S.; Vatis, Dimitrios

doi:10.2214/ajr.141.6.1195

Cited by 61 publications

(15 citation statements)

References 18 publications

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“…CNR (CNR tissue1,2 = S tissue1 À S tissue2 STDDEV air ) [20]. The CRs, SNRs, and CNRs of both sequences were compared using a paired one-tailed t-test [18].…”

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confidence: 99%

Imaging of the brain using the fast-spin-echo and gradient-spin-echo techniques

et al. 1998

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The aim of our study was to compare gradient-spin-echo (GRASE) to fast-spin-echo (FSE) sequences for fast T2-weighted MR imaging of the brain. Thirty-one patients with high-signal-intensity lesions on T2-weighted images were examined on a 1.5-T MR system. The FSE and GRASE sequences with identical sequence parameters were obtained and compared side by side. Image assessment criteria included lesion conspicuity, contrast between different types of normal tissue, and image artifacts. In addition, signal-to-noise, contrast-to-noise, and contrast ratios and were determined. The FSE technique demonstrated more lesions than GRASE and with generally better conspicuity. Smaller lesions in particular were better demonstrated on FSE because of lower image noise and slightly weaker image artifacts. Gray-white differentiation was better on FSE. Ferritin and hemosiderin depositions appeared darker on GRASE, which resulted in better contrast. Fatty tissue was less bright on GRASE. With current standard hardware equipment, the FSE technique seems preferable to GRASE for fast T2-weighted routine MR imaging of the brain. For the assessment of hemosiderin or ferritin depositions, GRASE might be considered.

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“…CNR (CNR tissue1,2 = S tissue1 À S tissue2 STDDEV air ) [20]. The CRs, SNRs, and CNRs of both sequences were compared using a paired one-tailed t-test [18].…”

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confidence: 99%

Imaging of the brain using the fast-spin-echo and gradient-spin-echo techniques

et al. 1998

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“…On the other hand, the inherent tissue relaxation times shorten when the magnetic field strength decreases (6)(7)(8). Although the absolute values of T1 are smaller, the relative differences in tissue relaxation times are generally larger at lower field strengths (8-10).…”

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confidence: 99%

Paramagnetic contrast enhancement at 0.02 T: An experimental study using Gd‐DOTA in normal and hydronephrotic kidneys

Niemi

Paajanen

Määttänen

et al. 1988

Magnetic Resonance in Med

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Both normal and experimentally hydronephrotic rabbits were imaged at 0.02 T using partial saturation (PS 160/30) and inversion recovery (IR 1000/200/40) sequences. The signal intensity of normal renal medulla and cortex markedly increased after the injection of 0.1 mmol/kg of Gd-DOTA. In the unilateral total hydronephrosis the dilated renal pelvis did not contrast enhance after 15 and 35 min of Gd-DOTA injection. The enhancement pattern was similar in 1- and 3-week-old hydronephrosis. The effect of Gd-DOTA on renal T1 times at 0.02 T was studied using rats. Fifteen minutes after the Gd-DOTA injection (0.1 mmol/kg) the T1 times of excised rat kidneys decreased from 311 to 90 ms. The authors conclude that the enhancement of the MR signal of the kidney by Gd-DOTA at an ultralow magnetic field (0.02 T) is similar to its enhancement at higher fields (greater than 0.15 T).

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“…First, a higher field strength of 3.0T does not only allow for a higher SNR but also introduces complications such as a higher susceptibility to artifacts (4) and altered relaxation times that impact on the contrast. Second, there is no direct relation between the field strength, the SNR, and the visual appreciation of the anatomical object in the image (5). Optimal selection and adjustment of additional hardware such as transmitter and receiver coils (e.g., avoiding crosstalk) may not necessarily be given.…”

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confidence: 99%