Sodium T<sub>2</sub>* relaxation times in human heart muscle

Pabst, Thomas; Sandstede, J.; Beer, Meinrad; Kenn, W.; Neubauer, Stefan; Hahn, Dietbert

doi:10.1002/jmri.10046

Cited by 20 publications

(16 citation statements)

References 42 publications

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“…Sodium MRI has been proposed and well validated in previous literature as a means for in vivo monitoring of changes in cartilage sodium concentration associated with various types of pathology (9-13). However, sodium ion exhibits very fast bi-exponential transverse relaxation decay in biological tissues, necessitating the use of ultra-short TE sequences (17, 20-23). Sodium MR imaging with clinically acceptable SNR and spatial resolution acquired with short TE has been demonstrated in the brain by previous investigators at clinical field strengths (22).…”

Section: Discussionmentioning

confidence: 99%

“…The in vivo 23 Na NMR signal is ∼22,000 times smaller than that of 1 H (including the differences in concentration), therefore the resultant low signal to noise ratio (SNR) can make it technically difficult to achieve clinically tolerable scan times (20-23). A part pf the SNR can be regained by using very short TR times due to the very short T 1 of sodium.…”

Section: Introductionmentioning

confidence: 99%

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Rapid isotropic 3D‐sodium MRI of the knee joint in vivo at 7T

Wang

Chang

et al. 2009

Magnetic Resonance Imaging

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Purpose:To demonstrate the feasibility of acquiring highresolution, isotropic 3D-sodium magnetic resonance (MR) images of the whole knee joint in vivo at ultrahigh field strength (7.0T) via a 3D-radial acquisition with ultrashort echo times and clinically acceptable acquisition times. Materials and Methods:Five healthy controls (four males, one female; mean Ϯ standard deviation [SD] age 28.7 Ϯ 4.8 years) and five patients with osteoarthritis (OA) (three males, two females; mean Ϯ SD age 52.4 Ϯ 5.6 years) underwent 23 Na MRI on a 7T, multinuclei equipped whole-body scanner. A quadrature 23 Na knee coil and a 3D-gradient echo (GRE) imaging sequence with a radial acquisition were utilized. Cartilage sodium concentration was measured and compared between the healthy controls and OA patients. Results:The average signal-to-noise ratio (SNR) for different spatial resolutions (1.2-4 mm) varied from ϳ14 -120, respectively. The mean sodium concentration of healthy subjects ranged from ϳ240 Ϯ 28 mM/L to 280 Ϯ 22 mM/L. However, in OA patients the sodium concentrations were reduced significantly by ϳ30%-60%, depending on the degree of cartilage degeneration. Conclusion:The preliminary results suggest that sodium imaging at 7T may be a feasible potential alternative for physiologic OA imaging and clinical diagnosis.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rapid isotropic 3D‐sodium MRI of the knee joint in vivo at 7T

Wang

Chang

et al. 2009

Magnetic Resonance Imaging

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“…In human heart muscle, only the T 2 * relaxation time has been determined (19). Therefore, the aim of our study was to determine the T 1 relaxation time in normal human heart muscle.…”

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Evaluation of sodium T₁ relaxation times in human heart

Pabst

Sandstede

Beer

et al. 2003

Magnetic Resonance Imaging

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Purpose: To evaluate the sodium longitudinal relaxation (T 1 ) characteristics for myocardium and blood in humans. Materials and Methods:Eleven healthy volunteers were examined by using a 23 Na heart surface coil at a 1.5 T clinical scanner equipped with a broadband spectroscopy option. 23 Na MR measurements were performed by using a three-dimensional spoiled gradient echo sequence (inplane resolution, 3.5 mm ϫ 7 mm; slice thickness, 24 mm; TE, 3.1 msec; bandwidth, 65 Hz/pixel; TR, 21 to 150 msec). Results:Longitudinal T 1 relaxation time components were 31.6Ϯ7.0 msec and 31.1Ϯ7.5 msec for myocardium and blood, respectively. SODIUM CONTENT AND FUNCTION OF THE SODIUM-POTASSIUM PUMP are important factors in human cellular physiology. Dysfunction in cell membrane function, e.g., in acute myocardial ischemia, results in alterations of the sodium-potassium pump function and of the intracellular sodium content. Scar tissue, such as after chronic myocardial infarction, also shows increased Na content due to expansion of extracellular space (1). Therefore, evidence of increased sodium content allows detection of both acute and chronic myocardial infarction. Because of a nuclear spin value of 3/2 of the isotope 23 Na, sodium state changes can be measured noninvasively with MR imaging and spectroscopy. Due to lower MR detection sensitivity and lower in vivo concentration (9.3% and 0.05% relative to 1 H), the major limitation of 23 Na MR is the reduced signal-tonoise ratio (SNR) compared with 1 H MR. 23 Na MR, however, allows noninvasive insight into regional cellular ion homeostasis while 1 H MRI does not. In vivo and in vitro animal and human clinical studies demonstrated the feasibility of detecting location and quantifying myocardial infarction (2-5). ConclusionAnimal studies have demonstrated (4) that not only the concentration of the isotope 23 Na, but also the MR parameter T 1 and T 2 relaxation time, undergo significant changes under pathophysiological conditions. Determination and knowledge of the T 1 and T 2 relaxation time is important due to three reasons: additional pathophysiological information may be obtained; interpretation of sodium MR image contrast will be aided because T 1 , T 2, as well as the concentration, are the dominant factors affecting the image contrast; and the knowledge of the fundamental MR properties of biological tissue is essential for the development of MR imaging sequences and optimization of examination parameters for dedicated anatomical areas.The nuclear spin of the isotope 23 Na is 3/2. Thus, in contrast to the nucleus 1 H with spin 1 ⁄2, quadrupolar interactions with neighboring molecules become possible. This is the reason for a more complex relaxation behavior of 23 Na in comparison to 1 H. In biological tissue, a biexponential transverse relaxation with a slow and a fast component, as well as monoexponential transverse relaxation, were found in animal and in in vivo human studies (6 -14). T 1 relaxation measurements were performed in in vitro animal studies (4,15) and in in vi...

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“…Another approach is to determine the T 2 time representing the 23 Na content. Recently, we showed that it is possible to measure 23 Na T * 2 and T 1 relaxation times in different cardiac regions in humans (22,23). Thus, with shorter TEs, this should allow for an absolute T 2 time determination in the human heart, which may also be a feasible approach for regional quantification of myocardial 23 Na content.…”

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Time course of ²³Na signal intensity after myocardial infarction in humans

Sandstede

Hillenbrand

Beer

et al. 2004

Magnetic Resonance in Med

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Experimental studies demonstrated persistently increased 23 Na content in nonviable myocardium post-myocardial infarction (MI). We hypothesized that nonviable myocardium in humans would show elevated 23 Na content at all stages of infarct development, and therefore could be imaged with 23 Na MRI. Ten patients were examined on days 4, 14, and 90 after infarction, and five of these patients participated in a 12-month follow-up. Physicians frequently require a diagnosis of myocardial viability in patients with large akinetic myocardial regions when they attempt to determine whether such patients should receive revascularization therapy. While nonviable myocardium cannot recover regional function, viable but stunned or hibernating myocardium will eventually resume contractile function following revascularization by percutaneous coronary intervention or bypass grafting (1). Current methods used to diagnose viability, such as positron emission tomography (PET), single photon emission tomography, or stress echocardiography, all have intrinsic limitations related to the use of ionizing radiation, limited access, patient discomfort, or limited acoustic windows. Recently, it was proposed that contrast-enhanced MRI is able to discriminate viable from nonviable myocardium (2).23 Na MRI is another promising approach for the detection of myocardial viability in human cardiac imaging without the need for an intravenous contrast agent (3,4). It has the potential to quantify infarct size, as well as to identify myocardial scars (5-8). In a recent experimental study employing 23 Na MR spectroscopy (MRS) and ion chromatography in the rat post-myocardial infarction (MI) model, we showed that the regional 23 Na concentration is significantly elevated in irreversibly injured myocardium following coronary ligation, both acutely and during the process of chronic scar formation (9). In the same study, we also showed that the Na signal was unchanged in stunned or hibernating myocardium. Thus, 23 Na MRI may allow physicians to diagnose myocardial viability in patients with akinetic areas, using Na content as an intrinsic contrast marker. In human studies, we were able to show that 1) cardiac 23 Na MRI can be applied in humans, 2) the myocardium/blood 23 Na signal intensity (SI) ratio represents the ratio of the 23 Na concentrations in myocardium and blood, and 3) 23 Na SI is elevated in MI (10,11). A comparison of 23 Na MRI with 1 H MRI techniques in patients with subacute or chronic MI, respectively, revealed an area of elevated 23 Na SI that significantly correlated with wall motion abnormalities, as detected by cine MRI, in all patients after subacute MI and 80% of patients with chronic MI (12). Myocardial edema in subacute MI also correlated with the areas of elevated 23 Na SI, but it was extensively larger, whereas a significant correlation of late enhancement with 23 Na MRI was found only in the subacute group. In the present clinical study, we hypothesized that total myocardial Na content would be elevated in patients with nonviabl...

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Sodium T₂* relaxation times in human heart muscle

Cited by 20 publications

References 42 publications

Rapid isotropic 3D‐sodium MRI of the knee joint in vivo at 7T

Rapid isotropic 3D‐sodium MRI of the knee joint in vivo at 7T

Evaluation of sodium T₁ relaxation times in human heart

Time course of ²³Na signal intensity after myocardial infarction in humans

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Sodium T2* relaxation times in human heart muscle

Cited by 20 publications

References 42 publications

Rapid isotropic 3D‐sodium MRI of the knee joint in vivo at 7T

Rapid isotropic 3D‐sodium MRI of the knee joint in vivo at 7T

Evaluation of sodium T1 relaxation times in human heart

Time course of 23Na signal intensity after myocardial infarction in humans

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Sodium T₂* relaxation times in human heart muscle

Evaluation of sodium T₁ relaxation times in human heart

Time course of ²³Na signal intensity after myocardial infarction in humans