MR relaxation times in human brain: measurement at 4 T.

Jezzard, Peter; Duewell, Stefan; Balaban, Robert S.

doi:10.1148/radiology.199.3.8638004

Cited by 115 publications

(83 citation statements)

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“…Chen et al ratio gain at 3.0 T ( 28,29 ). In the present study, we used the same contrast medium (gadodiamide) with the same standard clinical dose and the same injection method compared with the previous 1.5 T studies ( 13,14 ), so the results could be directly compared.…”

Section: Breast Imaging: Assessing Breast Cancer Response To Neoadjuvmentioning

confidence: 97%

Breast Cancer: Evaluation of Response to Neoadjuvant Chemotherapy with 3.0-T MR Imaging

Chen

Bahri²,

Mehta³

et al. 2011

Radiology

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Purpose:To assess how the molecular biomarker status of a breast cancer, including human epidermal growth factor receptor 2 (HER2), hormone receptors, and the proliferation marker Ki-67 status, affects the diagnosis at 3.0-T magnetic resonance (MR) imaging. Materials and Methods:This study was approved by the institutional review board and was HIPAA compliant. Fifty patients (age range, 28-82 years; mean age, 49 years) receiving neoadjuvant chemotherapy were monitored with 3.0-T MR imaging. The longest dimension of the residual cancer was measured at MR imaging and correlated with pathologic fi ndings.Patients were further divided into subgroups on the basis of HER2, hormone receptor, and Ki-67 status. Pathologic complete response (pCR) was defi ned as when there were no residual invasive cancer cells. The Pearson correlation was used to correlate MR imaging-determined and pathologic tumor size, and the unpaired t test was used to compare MR imaging-pathologic size discrepancies. Results:Of the 50 women, 14 achieved pCR. There were seven false-negative diagnoses at MR imaging. The overall sensitivity, specifi city, and accuracy for diagnosing invasive residual disease at MR imaging were 81%, 93%, and 84%, respectively. The mean MR imaging-pathologic size discrepancy was 0.5 cm 6 0.9 (standard deviation) for HER2-positive cancer and 2.3 cm 6 3 .5 for HER2-negative cancer ( P = .009). In the HER2-negative group, the size discrepancy was smaller for hormone receptor-negative than for hormone receptor-positive cancers (1.0 cm 6 1.1 vs 3.0 cm 6 4.0, P = .04). The size discrepancy was smaller in patients with 40% or greater Ki-67 expression (0.8 cm 6 1.1) than in patients with 10% or less Ki-67 expression (3.9 cm 6 5.1, P = .06). Conclusion:The diagnostic accuracy of breast MR imaging is better in more aggressive than in less aggressive cancers. When MR imaging is used for surgical planning, caution should be taken with HER2-negative hormone receptor-positive cancers.q RSNA, 2011Supplemental material : http://radiology.rsna.org/lookup /suppl

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Section: Breast Imaging: Assessing Breast Cancer Response To Neoadjuvmentioning

confidence: 97%

Breast Cancer: Evaluation of Response to Neoadjuvant Chemotherapy with 3.0-T MR Imaging

Chen

Bahri²,

Mehta³

et al. 2011

Radiology

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“…While the T 1 values have gotten longer indeed [15,16], they have not converged. In addition, the signal intensity variations expected due to B 1 inhomogeneities have been suppressed either by insensitivity to B 1 in the acquisition [17,18] or by postprocessing strategies [11].…”

Section: Anatomic Imagingmentioning

confidence: 99%

Ultrahigh field magnetic resonance imaging and spectroscopy

Uğurbil

Adriany

Andersen

et al. 2003

Magnetic Resonance Imaging

225

173

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“…Thus, specific care has to be taken during the design of imaging experiments, as an improper choice of sequence parameter can easily diminish the promised gain in SNR. Notably, the T 1 relaxation time in brain tissue increases with field strength (15,17,18,20) and thus counteracts the gain from in SNR and CNR in GRE sequences with TR Ӷ T 1 at higher fields (see Theory). Beyond that, we employed very similar sampling times at both fields (T s ϭ 40.1 ms and T s ϭ 39.8 ms).…”

Section: Snrmentioning

confidence: 99%

Neuroimaging at 1.5 T and 3.0 T: Comparison of oxygenation‐sensitive magnetic resonance imaging

Krüger

Kastrup

Glover

2001

Magnetic Resonance in Med

312

222

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Noise properties, the signal-to-noise ratio (SNR), contrast-tonoise ratio (CNR), and signal responses were compared during functional activation of the human brain at 1.5 and 3.0 T. At the higher field spiral gradient-echo (GRE) brain images revealed an average gain in SNR of 1.7 in fully relaxed and 2.2 in images with a repetition time (TR) of 1.5 sec. The tempered gain at longer TRs reflects the fact that the physiological noise depends on the signal strength and becomes a larger fraction of the total noise at 3.0 T. Activation of the primary motor and visual cortex resulted in a 36% and 44% increase of "activated pixels" at 3.0 T, which reflects a greater sensitivity for the detection of activated gray matter at the higher field. The gain in the CNR exhibited a dependency on the underlying tissue, i.e., an increase of 1.8؋ in regions of particular high activation-induced signal changes (presumably venous vessels) and of 2.2؋ in the average activated areas. These results demonstrate that 3.0 T provides a clear advantage over MRI modalities are often limited by the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). Both SNR and CNR have been shown to increase with magnetic field strength B 0 (1,2). Consequently, the "optimal field strength" and the field dependency in blood oxygenation level dependent (BOLD) MRI have been the subject of various investigations (1,3-6). For many MRI applications a magnetic field strength of 1.5 Tesla (T) seems to represent a good compromise. Functional MRI (fMRI), however, is particularly dependent on good SNR and CNR properties, since typically observed BOLD signal changes at 1.5 T are on the order of a few percent and often exceed the intrinsic noise only slightly. Several biophysical models of activation-induced changes of the oxygenation-sensitive MRI signals have proposed that the changes in the relaxation rate ⌬R* 2 and subsequently the BOLD effect are proportional to B 0 for large vessels and proportional to B 0 2 for small vessels and capillaries (7,8). Thus, higher fields may provide an important improvement in fMRI. Indeed, recent investigations have demonstrated a superlinear increase in the BOLD CNR with the field strength (1,4,5), suggesting that high field fMRI methods may be able to resolve oxygenation changes in small vessels and capillaries, which are spatially localized near the origin of the neuronal activity.In the present study, various BOLD-relevant properties were compared at 1.5 T and 3.0 T. In order to establish identical BOLD-sensitivities, we investigated the T* 2 relaxation times for gray matter at each field strength and scaled the corresponding echo time (TE), and the excitation angle at 3.0 T. We compared intrinsic noise contributions and the SNR in gradient-echo (GRE) images and examined activation-induced BOLD responses during visual and motor activation at both fields in terms of spatial extent, the mean z-score, and the CNR of "activated voxels." T* 2 -maps from various brain sections were calculated to investigate spatial aspect...

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MR relaxation times in human brain: measurement at 4 T.

Cited by 115 publications

References 0 publications

Breast Cancer: Evaluation of Response to Neoadjuvant Chemotherapy with 3.0-T MR Imaging

Breast Cancer: Evaluation of Response to Neoadjuvant Chemotherapy with 3.0-T MR Imaging

Ultrahigh field magnetic resonance imaging and spectroscopy

Neuroimaging at 1.5 T and 3.0 T: Comparison of oxygenation‐sensitive magnetic resonance imaging

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