Biomedical subjects

Frederick H Epstein

Publications and source records attributed to Frederick H Epstein.

At least 19 recordsLinked to original sources

PubMed2007

Reproducibility and reliability of atherosclerotic plaque volume measurements in peripheral arterial disease with cardiovascular magnetic resonance.

A high resolution, noninvasive approach to quantify atherosclerotic plaque in the peripheral vasculature could have significant clinical and research utility. Seventeen patients with peripheral arterial disease (PAD) were studied in a 1.5T CMR scanner. Atherosclerotic plaque volume in the superficial femoral artery was measured and interobserver, intraobserver, and test-retest variability determined. Nineteen vessels were studied with mean acquisition time of 13.1 minutes per vessel. Mean plaque volume was 7.27 +/- 3.73 cm3. Intra-observer intraclass correlation was R = 0.997, inter-observer was R = 0.987, and test-retest reproducibility was R = 0.996. Thus, high resolution measurement of plaque volume in PAD is reliable and reproducible.

Adult↗

PubMed2006

Delayed calf muscle phosphocreatine recovery after exercise identifies peripheral arterial disease.

OBJECTIVES: In this study we intend to characterize phosphocreatine (PCr) recovery kinetics with phosphorus-31 ((31)P) magnetic resonance spectroscopy in symptomatic peripheral arterial disease (PAD) patients compared with control subjects and determine the diagnostic value and reproducibility of this parameter. BACKGROUND: Due to the inconsistent relationship between flow and function in PAD, novel techniques focused on the end-organ are needed to assess disease severity and measure therapeutic response. METHODS: Fourteen normal subjects (5 men, age 45 +/- 14 years) and 20 patients with mild-to-moderate symptomatic PAD (12 men, age 67 +/- 10 years, mean ankle brachial index 0.62 +/- 0.13) were studied. Subjects exercised one leg to exhaustion while supine in a 1.5-T magnetic resonance scanner using a custom-built plantar flexion device. Surface coil-localized, free induction decay acquisition localized to the mid-calf was used. Each 31P spectrum consisted of 25 signal averages at a repetition time of 550 ms. The PCr recovery time constant was calculated by monoexponential fit of PCr versus time, beginning at exercise completion. RESULTS: Median exercise time was 195.0 s in normal subjects and 162.5 s in PAD patients (p = 0.06). Despite shorter exercise times in patients, the median recovery time constant of PCr was 34.7 s in normal subjects and 91.0 s in PAD patients. Area under the receiver-operating characteristic curve was 0.925 +/- 0.045. Test-retest reliability was excellent. CONCLUSIONS: The PCr recovery time constant is prolonged in patients with symptomatic PAD compared with normal subjects. The method is reproducible and may be useful in the identification of disease. Further study of this parameter's ability to track response to therapy as well as its prognostic capability is warranted.

Adult↗

PubMed2006

Spatial and spectral heterogeneity of time-varying shear stress profiles in the carotid bifurcation by phase-contrast MRI.

PURPOSE: To determine the heterogeneity of the time-varying shear stress profiles in the human carotid bifurcation, a region prone to atherosclerosis. MATERIALS AND METHODS: Lagrangian bicubic interpolation of phase-contrast MRI images was used to determine the shear stress profiles for three adult healthy male volunteers. Frequency spectra for the common and internal carotid artery (CCA and ICA, respectively)-derived shear stresses were examined in order to determine the presence of significant heterogeneity in the intensity distribution. RESULTS: Hemodynamic characteristics (peak, minimum, average shear stress, and oscillatory shear index [OSI]) were highly heterogeneous both along the length of the vessel as well as circumferentially around the CCA and ICA. In the frequency domain, intensities below 4 Hz were significantly higher in the CCA compared to the sinus region of the ICA, indicating that shear stress heterogeneity can be detected in the frequency domain. The harmonic index, a measure of the relative contributions of dynamic and static components of the shear stress signal, colocalizes with OSI, which implies a relationship between specific frequency components and atherosclerosis development. CONCLUSION: These findings indicate that the time and frequency dependent parameters of in vivo shear stress have important implications for regional development of atherosclerosis.

Adult↗

PubMed2006

Selective suppression of artifact-generating echoes in cine DENSE using through-plane dephasing.

In displacement-encoded imaging with stimulated echoes (DENSE), tissue displacement is encoded in the phase of the stimulated echo. However, three echoes generally contribute to the acquired signal (the stimulated echo, the complex conjugate of the stimulated echo, and an echo due to T(1) relaxation). It is usually desirable to suppress all except the stimulated echo, since otherwise the additional echoes will cause displacement measurement errors. Ideally, suppression of the artifact-generating echoes would be independent of time, T(1), and displacement-encoding frequency, and would not require additional acquisitions. In this study through-plane gradients were used to selectively dephase artifact-generating echoes without causing significant signal loss of the stimulated echo. A cine DENSE sequence was modified to include dephasing gradients and perform complementary spatial modulation of magnetization (CSPAMM). For single-acquisition cine DENSE using dephasing alone, artifact suppression was similar to CSPAMM with two acquisitions. The use of dephasing with CSPAMM required two acquisitions, but demonstrated greater artifact suppression than CSPAMM alone or dephasing alone.

Algorithms↗

PubMed2006

Reperfused myocardial infarction in mice: 3D mapping of late gadolinium enhancement and strain.

We developed mathematical modeling tools for mapping 3D infarct geometry from multislice late gadolinium enhancement data, allowing fusion with multislice MR tagging data, in mice with myocardial infarction. Five C57BL/6 mice were imaged at baseline, 1, 7 and 28 days after 60 min occlusion of the left anterior descending coronary artery. The 3D infarct geometry was mapped in material coordinates, and registered with 3D strain, showing permanent dysfunction in infarcted segments, intermediate function in the adjacent zone, and maintained function in the remote zone. 3D mapping of late enhancement and strain allows registration of multiple studies in a consistent framework.

Analysis of Variance↗

PubMed2005

Interaction between AT1 and AT2 receptors during postinfarction left ventricular remodeling.

The relative contribution of the angiotensin II type 1 and 2 receptors (AT1-R and AT2-R) in postmyocardial infarction (MI) remodeling remains incompletely understood. We studied five groups of C57Bl/6 mice after 1 h of left anterior descending artery occlusion-reperfusion: 1) wild type, untreated (n = 12); 2) wild type, treated with the AT1-R blocker losartan (10-20 mg.kg(-1).day(-1) in drinking water) from day 1 to day 28 post-MI (n = 10); 3) cardiac overexpression of the AT2-R [AT2-transgenic (TG); n = 14]; 4) AT2-TG treated with losartan (n = 13); and 5) AT2-TG and null for the AT1a-R [AT2-TG/AT1 knockout (KO); n = 10]. Cardiac magnetic resonance imaging (CMR) measured ejection fraction and left ventricular end-diastolic and end-systolic volume (EDVI and ESVI) and mass indexed to weight on days 0, 1, 7, and 28 post-MI. Infarct size was measured on day 1 by late gadolinium-enhanced CMR. Regional myocyte hypertrophy and collagen content were measured on day 28 post-MI. Infarct size was similar among groups. Systolic blood pressure was lowest in AT2-TG/AT1KO. By day 28 post-MI, when corrected for baseline differences, EDVI and ESVI were higher and ejection fraction was lower in wild type than other groups. Ejection fraction was highest and EDVI and mass index were lowest in AT2-TG/AT1KO at day 28. The AT2-TG/AT1KO demonstrated less fibrosis in adjacent regions. Regional myocyte hypertrophy was similar in all groups. The AT1-R and AT2-R are intricately intertwined in post-MI remodeling. Pharmacological blockade of AT1-R is equivalent to AT2-R overexpression in attenuating post-MI remodeling. Genetic knockout of the AT1a-R is additive to AT2-R overexpression, due, at least in part, to blood pressure lowering.

Animals↗

PubMed2005

Black blood gradient echo cine magnetic resonance imaging of the mouse heart.

A black blood gradient echo sequence for multiphase cardiac MRI of the mouse heart was implemented on a 4.7-T scanner and compared to a conventional bright blood sequence. Black blood was achieved using the double inversion recovery technique. Ten mice were imaged using both the bright and the black blood sequences, and 2 of the mice were additionally imaged using bright and black blood sequences modified to perform myocardial tagging. Manual planimetry of the images was performed by two independent observers to detect the endocardial and epicardial borders and subsequently to compute chamber volumes and myocardial mass. Weight of the excised left ventricle was used as a gold standard for myocardial mass. Bland-Altman analysis demonstrated reduced interobserver variability for the measurement of cardiac volumes using the black blood sequence compared to the bright blood sequence (95% confidence interval was -0.89-0.73 microL for black blood versus -1.86-1.28 microL for bright blood). Also, Bland-Altman analysis showed that the black blood sequence provides improved accuracy for the measurement of myocardial mass compared to the bright blood sequence (average difference between MRI versus weight was 0.9 microg for black blood and -11.2 microg for bright blood, P < 0.01). For myocardial tagging, qualitative assessment demonstrated improved endocardial border definition using the black blood sequence. Black blood cine MRI in mice provides reduced interobserver variability and improved accuracy for the measurement of myocardial volumes and mass compared to the conventional bright blood technique.

Animals↗

PubMed2005

The angiotensin II type 2 receptor and improved adjacent region function post-MI.

Angiotensin II type 2 receptor (AT2-R) overexpression in the mouse heart preserves left ventricular (LV) size and global LV function during post-MI remodeling. We hypothesized that CMR tagging would localize regional improvements in myocardial function during post-MI remodeling in AT2-R cardiac overexpressed transgenic mice (TG), which could explain the preservation of global LV function post-MI. Six male wild-type (WT) C57BL/6 mice and 10 TG mice were studied by CMR at baseline (day 0) and days 1, 7, and 28 post-MI. MI was induced by 1 hour occlusion of the LAD followed by reperfusion. On day 1 post-MI, gadolinium-DTPA was injected to assess infarct size. LV size and function was assessed by cine CMR. Mean % circumferential shortening (%CS) was calculated within infarcted, adjacent, and remote regions at each time point in WT and TG mice. Quantitative interstitial collagen and mean myocyte cross-sectional area was measured postmortem at day 28 post-MI. LV end-systolic volume was lower and ejection fraction higher at baseline in the TG group and these differences were maintained post-MI. Within infarcted and remote zones, although %CS was higher in TG mice at day 0, there was no difference by day 28 between groups. Within adjacent regions, while there was no difference at day 0 or 1 in TG vs. WT, %CS was significantly higher in TG mice by day 7, and these changes persisted out to day 28 post-MI. Regional interstitial collagen and myocyte size were similar between groups. Thus, myocardial tagging can detect regional differences in contractile function post-MI in TG mice, and AT2-R overexpression is associated with improved contractile function in adjacent noninfarcted myocardium.

Angiotensin II↗

PubMed2004

Measurement of myocardial mechanics in mice before and after infarction using multislice displacement-encoded MRI with 3D motion encoding.

Cardiac MRI is an accurate, noninvasive modality for assessing the structure and function of the murine heart. In addition to conventional imaging, MRI tissue tracking methods can quantify numerous aspects of myocardial mechanics, including intramyocardial displacement, strain, twist, and torsion. In the present study, we developed and applied a novel pulse sequence based on displacement-encoded imaging using stimulated echoes (DENSE) that achieves multislice coverage, high spatial resolution, and three-dimensional (3D) displacement encoding. With the use of this technique, myocardial mechanics of C57Bl/6 mice were measured at baseline and 1 day after experimental myocardial infarction. At baseline, the mean systolic transmural circumferential strain was -0.14 +/- 0.02 and the mean systolic radial strain was 0.30 +/- 0.05. Changes in circumferential and radial strains from the subepicardium to the subendocardium were detected at baseline (P < 0.05). One day after infarction, significantly reduced 3D displacements and strain were detected in infarcted and noninfarcted myocardium. Infarction also reduced normalized systolic torsion from its baseline value of 1.35 +/- 0.27 degrees /mm (R = 0.99) to 0.07 +/- 0.54 degrees /mm (R = 0.96, P < 0.05). DENSE MRI can assess the 3D myocardial mechanics of the murine heart in <1 h of scan time at 4.7 T and may be applied to studies of myocardial mechanics in genetically engineered mice.

Animals↗

PubMed2004

Magnetic resonance imaging identifies the fibrous cap in atherosclerotic abdominal aortic aneurysm.

BACKGROUND: MRI can distinguish components of atherosclerotic plaque. We hypothesized that contrast enhancement with gadolinium-DTPA (Gd-DTPA) could aid in the differentiation of plaque components in abdominal aortic aneurysm (AAA). METHODS AND RESULTS: Twenty-three patients (19 males, age 70+/-8 years) with AAA underwent MRI on a 1.5-T clinical scanner 3+/-3 days before surgical grafting. T1- and T2-weighted (W) black blood spin echo imaging was performed in 1 axial slice, and the T1-W imaging was repeated after a Gd-DTPA-enhanced 3D magnetic resonance angiogram. A section of the aorta at the site of imaging was resected at surgery for histopathologic examination of tissue components and inflammatory cells. Signal-to-noise and contrast-to-noise ratios (CNR) were measured in visualized plaque components from multispectral MRI, and percent enhancement after contrast on T1-W imaging was calculated. The kappa value for agreement between pathology and MRI for the number of tissue components was 0.785. T2-W imaging identified thrombus as regions of high signal and lipid core as low signal, with a CNR of 6.43+/-3.41. Nine patients had a fibrous cap pathologically, which was visualized as a discrete area of uniform increased signal on T2-W imaging with a CNR of 4.52+/-1.93 compared with lipid core. Within the cap, the percent enhancement after Gd-DTPA on T1-W imaging was 91+/-63%. CONCLUSIONS: Higher signal on T2-W MRI identifies the fibrous cap and thrombus within AAA. Contrast enhancement improves delineation of the fibrous cap. The addition of contrast to MRI plaque imaging may enhance identification of vulnerable plaque.

Aged↗

PubMed2004

Myocardial tissue tracking with two-dimensional cine displacement-encoded MR imaging: development and initial evaluation.

A breath-hold two-dimensional cine magnetic resonance (MR) pulse sequence based on displacement encoding with stimulated echoes (DENSE) for quantitative myocardial motion tracking was developed and evaluated. In the sequence, complementary spatial modulation of magnetization was used for time-independent artifact suppression, and echo-planar imaging was used for rapid data sampling. Twelve healthy volunteers underwent cine DENSE MR imaging, and six of them also underwent conventional MR imaging myocardial tagging. The circumferential shortening component of strain (E(cc)) was measured on cine DENSE MR images and conventional tagged MR images. With complementary spatial modulation of magnetization, 10% or less of the total cine DENSE MR image energy was attributed to an artifact-generating echo during systolic imaging. Two-dimensional intramyocardial displacement and strain were measured at cine DENSE MR imaging with spatial resolution and temporal resolution of 2.7 x 2.7 mm and 60 msec, respectively. E(cc) measured at cine DENSE MR imaging correlated well with that measured at conventional MR imaging tagging (slope = 0.88, intercept = 0.00, R = 0.87).

Adult↗

PubMed2004

Nitric oxide mediates benefits of angiotensin II type 2 receptor overexpression during post-infarct remodeling.

We hypothesized that nitric oxide (NO) mediates the benefits of cardiac angiotensin II type 2 (AT(2)-R) overexpression during postmyocardial infarction (post-MI) remodeling. Eleven wild-type (WT) C57BL/6 mice and 28 transgenic (TG) mice with AT(2)-R overexpression were studied by cardiac magnetic resonance imaging (CMR) at baseline and days 1 and 28 post-MI induced by left anterior descending artery occlusion and reperfusion. Sixteen TG mice were treated from day 1 through 28 post-MI with the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester in drinking water at 1 mg/mL (TG-Rx). Left ventricular mass index (LVMI), end-diastolic volume index (EDVI) and end-systolic volume index (ESVI), wall thickness, percent thickening, and ejection fraction (EF) were measured. Infarct size on day 1 was assessed by post-contrast CMR. Interstitial collagen was quantified in noninfarcted regions. At baseline, heart rate (HR), blood pressure (BP), LVMI, EDVI, and ESVI were similar between groups, as were infarct size and weekly post-MI HR and systolic BP. By day 28 post-MI, EDVI and ESVI were similar in WT and TG-Rx, but significantly lower in TG (ESVI: 1.41+/-0.18 microL/g versus 2.53+/-0.14 microL/g in WT; 2.17+/-0.14 microL/g in TG-Rx; P<0.008 for both). At day 28, EF was higher in TG (46.3%+/-2.9%) compared with WT and TG-Rx (32.7+/-2.3% and 33.7+/-2.3, respectively; P<0.003 for both). Wall thickening at day 28 post-MI was greater in the base and mid-LV in TG than WT and TG-Rx. Noninfarcted region interstitial collagen was similar between groups. Thus, the NO pathway may mediate much of the benefits of cardiac AT(2)-R overexpression during post-MI remodeling.

Animals↗

PubMed2004

Complementary displacement-encoded MRI for contrast-enhanced infarct detection and quantification of myocardial function in mice.

MRI is emerging as an important modality for assessing myocardial function in transgenic and knockout mouse models of cardiovascular disease, including myocardial infarction (MI). Displacement encoding with stimulated echoes (DENSE) measures myocardial motion at high spatial resolution using phase-reconstructed images. The current DENSE technique uses inversion recovery (IR) to suppress T(1)-relaxation artifacts; however, IR is ill-suited for contrast-enhanced infarct imaging in the heart, where multiple T(1) values are observed. We have developed a modified DENSE method employing complementary acquisitions for T(1)-independent artifact suppression. With this technique, displacement and strain are measured in phase-reconstructed images, and contrast-enhanced regions of infarction are depicted in perfectly coregistered magnitude-reconstructed images. The displacement measurements and T(1)-weighted image contrast were validated with the use of a rotating phantom. Modified DENSE was performed in mice (N = 9) before and after MI. Circumferential (E(cc)) and radial (E(rr)) strain were measured, and contrast-enhanced infarcted myocardium was detected by DENSE. At baseline, E(cc) was -0.16 +/- 0.01 and E(rr) was 0.39 +/- 0.07. After MI, E(cc) was 0.04 +/- 0.02 and E(rr) was 0.03 +/- 0.04 in infarcted regions, whereas E(cc) was -0.12 +/- 0.02 and E(rr) was 0.38 +/- 0.09 in noninfarcted regions. In vivo E(cc) as determined by DENSE correlated well with E(cc) obtained by conventional tag analysis (R = 0.90).

Animals↗

PubMed2004

Increasing the signal-to-noise ratio in DENSE MRI by combining displacement-encoded echoes.

A new technique was developed to increase the signal-to-noise ratio (SNR) in displacement encoding with stimulated echoes (DENSE) MRI. This signal-averaged DENSE (sav-DENSE) technique is based on the SNR advantage of extracting a pair of DENSE images with uncorrelated noise from the complex complementary spatial modulation of the magnetization image, and combining them during image reconstruction. Eleven healthy volunteers were imaged at three short-axis locations with the use of sav-DENSE, cine DENSE, and myocardial tagging pulse sequences. In this study, sav-DENSE increased the SNR by 15-34% as compared to cine DENSE. Circumferential strain values measured by sav-DENSE and myocardial tagging were strongly correlated (slope = 0.95, intercept = -0.02, R = 0.92) and within the 95% limits of agreement. The breath-hold sav-DENSE technique yielded relatively accurate and precise quantification of 2D intramyocardial function, with a 40.2-ms temporal resolution and a 3.5 x 3.5 mm2 spatial resolution.

Adult↗

PubMed2004

Displacement-encoded cardiac MRI using cosine and sine modulation to eliminate (CANSEL) artifact-generating echoes.

Displacement-encoded imaging with stimulated echoes (DENSE) and harmonic phase imaging (HARP) employ 1-1 spatial modulation of magnetization to cosine modulate the longitudinal magnetization as a function of position at end diastole. Later in the cardiac cycle they sample the cosine-modulated signal and compute myocardial strain from the signal phase. The sampled signal generally includes three distinct echoes: 1) a displacement-encoded stimulated echo, 2) the complex conjugate of the displacement-encoded echo, and 3) an echo arising from T1 relaxation. If the T1-relaxation and complex conjugate echoes are suppressed, then a phase image representing just the displacement-encoded echo can be reconstructed. In the present study, the use of cosine and sine modulation to eliminate (CANSEL) the T1-relaxation and complex conjugate echoes was investigated. With the use of CANSEL, it was demonstrated that DENSE accurately measures through-plane as well as in-plane components of tissue motion. Also, DENSE with CANSEL artifact suppression can provide increased signal-to-noise ratio (SNR) secondary to reduced intravoxel dephasing by using relatively low displacement-encoding frequencies. For applications that employ DENSE imaging with multiple acquisitions, the CANSEL technique can suppress artifact-generating echoes without placing constraints on the displacement-encoding frequency and direction.

Animals↗

PubMed2004

Infarct involution and improved function during healing of acute myocardial infarction: the role of microvascular obstruction.

Delayed contrast-enhanced cardiac magnetic resonance imaging (ceCMR) delineates infarct size. The presence of hypoenhancement consistent with microvascular obstruction (MO) signifies larger infarcts with a worse prognosis. We hypothesized that the size of the contrast defect (CD) on ceCMR in acutely infarcted myocardium may change during infarct healing and depend upon the presence of MO. Twenty-five patients underwent CMR on weeks 1 and 8 after reperfused myocardial infarction. After short-axis cine CMR was performed, gadolinium was infused and ceCMR images and matched tagged cine MR images were obtained in the three most dysfunctional short-axis slices on cine CMR. The area and transmural extent of hyperenhancement (HE) with or without MO representing total CD size were planimetered. Between week 1 and week 8, the CD area fell from 1729+/-970 mm2 at week 1 to 1270+/-706 mm2 (p<0.001), as did the transmural extent of infarction (71+/-22% to 63+/-24%, p<0.001). The decline in CD trended to be higher in patients with MO (840+/-807 mm2) than in HE (312+/-485 mm2, p<0.07). In the patient group as a whole, ejection fraction (EF) improved (56+/-9% to 60+/-10%, p=0.002) between weeks 1 and 8, but patients with MO showed no increase in EF. Segments with some HE demonstrated partial functional improvement whereas no improvement was seen in HE+MO segments. In patients 8 weeks after reperfused myocardial infarction (MI), the size of infarction by ceCMR decreases compared to week 1 post-MI, especially in those with microvascular obstruction in whom there is little improvement in regional or global function.

Adult↗

PubMed2003

Assessment of regional systolic and diastolic dysfunction in familial hypertrophic cardiomyopathy using MR tagging.

Diastolic and systolic left ventricular (LV) dysfunction often significantly contribute to disabling symptoms in familial hypertrophic cardiomyopathy (FHC). This study compares regional LV function (midwall circumferential strain) during systole and diastole in eight FHC patients and six normal volunteers (NVs) using MR tagging. A prospectively-gated fast gradient-echo sequence with an echo-train readout was modified to support complementary spatial modulation of magnetization (CSPAMM) tagging and full cardiac cycle data acquisition using the cardiac phase to order reconstruction (CAPTOR), thus providing tag persistence and data acquisition during the entire cardiac cycle. Total systolic strains in FHC patients were significantly reduced in septal and inferior regions (both P < 0.01). Early-diastolic strain rates were reduced in all regions of the FHC group (all P < 0.03). The combination of CSPAMM and CAPTOR allows regional indices of myocardial function to be quantified throughout the cardiac cycle. This technique reveals regional differences in systolic and diastolic impairment in FHC patients.

Cardiomyopathy, Hypertrophic↗

PubMed2003

Importance of k-space trajectory in echo-planar myocardial tagging at rest and during dobutamine stress.

Hybrid fast gradient echo/echo-planar imaging (FGRE-EPI) can be used to increase temporal resolution, enhance tag contrast, and/or decrease scan time for breathhold myocardial tagging. However, off-resonance effects and motion can lead to local phase discontinuities in FGRE-EPI raw data when a conventional interleaved bottom-up k-space trajectory is used. These discontinuities can be particularly problematic for myocardial tagging, where the image energy is not only concentrated near the k-space origin, but is also concentrated in multiple spectral peaks centered throughout k-space. In this study, tag distortion artifacts in FGRE-EPI tagging due to off-resonance and velocity-induced phase discontinuities were characterized at rest and dobutamine stress, and the flyback and gradient moment smoothing (GMS) methods were shown to reduce these artifacts. For the specific parameters used in this study, flyback and GMS resulted in improved image quality at rest and stress, increased myocardium-tag contrast-to-noise ratio (11.4 +/- 2.1 vs. 10.0 +/- 2.9, P < 0.01 at rest; 11.1 +/- 1.8 vs. 8.1 +/- 2.4, P < 0.01 at stress), and reduced full width at half maximum of the tag profile (3.6 vs. 3.8 pixels at rest; 4.0 vs. 5.1 pixels at stress) compared to the conventional trajectory. A limitation of the improved trajectory is a parameter-dependent decrease in data acquisition efficiency. For the specific imaging protocol used, the repetition time of the improved trajectory increased by 36% compared to the conventional trajectory.

Artifacts↗