William Schapiro

Effects of respiratory cycle and body position on quantitative pulmonary perfusion by MRI.

To evaluate the performance of lung perfusion imaging using two‐dimensional (2D) first pass perfusion MRI and a quantitation program based on model‐independent deconvolution algorithm.

On the cause of spatial displacement of long T1 species in segmented inversion recovery prepared imaging

Using inversion recovery steady‐state free precession segmented k‐space imaging for the detection of myocardial infarction, we noticed that some structures appeared in the wrong locations of the image. In this work, the spatial displacement is demonstrated and explained from both theoretical and experimental points of view. The effect is due to a change in phase from segment to segment of the detected magnetization from species with long T1s such as cysts, fluid collections, and cerebrospinal fluid. Depending on the number of k‐space segments and view ordering, structures can be replicated throughout the image or displaced by half of the phase‐encoding field of view. Magn Reson Med 54:481–485, 2005.

1076 Effects of age and gender on right ventricular structure and function: a turning point at age fifty

Methods We studied 218 (99 male, 119 female) normotensive, non-obese (BMI < 28), non-diabetic volunteers aged 20– 90 (mean 54 ± 15) with normal 2-D echocardiograms on a 1.5 T Siemens Sonata scanner. TrueFISP cine imaging was used to obtain contiguous 8 mm short axis slices of the entire RV at end-expiration. Volumetric analysis was performed using Medis MASS. RV volume at end-diastole and end-systole and RV mass were determined and indexed to body surface area (EDVi, ESVi, RVMi) including papillary muscles in the cavity volume.

Association of reduced right ventricular global and regional wall motion with abnormal right heart hemodynamics

Background The relationship of right ventricular (RV) regional and global systolic function to right heart hemodynamics is not well understood. In this study we used MRI feature tracking to assess regional RV wall motion, cine MR to evaluate global RV function and examined the relationship of regional wall motion and global RV function to right heart hemodynamics. Methods Fifty patients undergoing clinically indicated right heart catheterization were prospectively recruited to a research CMR within 5 hours of catheterization. Majority of the heart failure cases were due to left heart failure. SSFP cine images were acquired to evaluate RV regional and global function. RV longitudinal and long axis radial strains were derived from the 4-chamber cine, and mid wall septal circumferential and radial strains from the short-axis plane in mid ventricle using CIM feature tracking software (Auckland, NZ). Right heart hemodynamics was assessed during catheterization. Results Mean age was 64±13 years, mean RV ejection fraction (EF) 51±13%. Reduced longitudinal and radial displacement in 4 chamber view was significantly associated with reduced RVEF, r=-0.621 (p<0.001) and r=0.346 (p=0.014), respectively. Similarly, in short axis plane reduced septal circumferential and radial strain were also significantly correlated with RVEF, r=-0.488 (p=0.001) and r=0.527 (p<0.001) respectively. In regression analysis reduced RVEF had strongest association with increased pulmonary wedge pressure (r=-0.622, p<0.001) in univariate analysis and in multivariate analysis (p<0.001) after adjusting for all the right heart hemodynamic parameters. Pulmonary wedge pressure contributed to 41% of RVEF variation in this cohort with predominant left heart failure. While also significantly correlated with pulmonary wedge pressure, regional wall motion including longitudinal strain, septal circumferential and radial strain had strongest association with mean pulmonary arterial pressure, r=0.577 (p<0.001), r=0.440 (p=0.002) and r=-0.451 (p=0.001), respectively. Conclusions It is feasible to use MR feature tracking to characterize RV regional wall motion. Reduced global and regional RV systolic functions are associated with right heart hemodynamic abnormalities. In patients with predominant left heart failure, pulmonary wedge pressure contributes importantly to RVEF variation. Funding None.

Image based magnetic field background correction for aortic and pulmonary artery flow measurement using phase contrast

A large gel phantom was used to assess phase offset in through-plane phase contrast images in x (left to right), y (anterior to posterior) and z directions at the isocenter and in positions ±40 mm and ±80 mm away from the isocenter. Repeated measures were averaged and fit to linear regressions. Phase correction was validated in human study for the assessment of aorta and pulmonary artery (PA) flow which was followed immediately by a phantom scan using the same settings. The aorta and PA flow corrected by the regression calculated background phase was compared to that corrected by the measured background phase in the phantom study. Results The gel phantom experiments showed a linear phase descent in z direction through the isocenter with an average slope of -0.019±0.001 cm/s/mm (R2=0.998), demonstrating a velocity descent per millimeter away from the isocenter. The change in z direction was consistent in anterior, posterior, left and right sides of the phantom. There was also a linear phase descent (slope 0.009±0.0005 cm/s/mm, R2 =0.999) in the y direction but phase shift was limited in the x direction (slope 0.0005±0.0008 cm/s/mm, R2 =0.241). In human studies (N=30), average background phase velocity measured by phantom was 0.85± 0.56 cm/s in aortic position and 1.0 ±0.74 cm/s in PA, resulting in 8.9% and 7.5% flow errors in aorta and PA, respectively. The calculated aortic background phase velocity using linear regression was 0.81±0.47 cm/s which was not significantly different from phantom measured phase (p=NS). Calculated phase in the aortic position was applied to correct background phase in both aorta and PA flow given their proximity. Compared to phantom corrected measurements, the flow corrected using calculated phase yielded a very small residual error, mean 0.9±4.0 ml/beat in aorta and 0.9±5.1 ml/beat in PA. Conclusions Phantom experiments demonstrated linear phase variations in the y and z directions but to a less extent in the x direction. Findings in human studies indicate that the linear phase shift is a significant source of phase error and can be removed using linear regression calculated phase from the image itself. Image based background phase correction is a promising alternative to phantom calibration in clinical practice. Funding None.

Left ventricular concentric remodeling in normal aging is associated with decline of diastolic function assessed by multi-modality imaging

In this carefully screened normal cohort, age dependent concentric remodeling was associated with significant decline in diastolic global function and mechanics, increased systolic torsion with preserved LVEF and a mild trend toward reduced systolic strain. Age related changes in diastolic function were more pronounced in women than in men.

The aging effect: The relationship of twist to structural and mechanical remodeling of the left ventricle in a normal population using HARP CMRI

Methods Forty-one normal volunteers were prospectively recruited. Subjects were nonobese, nondiabetic, normotensive and free of cardiovascular history or significant valvular or myocardial disease by screening echocardiography. After volumetric short axis retrospectively gated SSFP cine imaging (1.5 T Siemens Avanto), breath-hold retrospectively gated short axis tagged gradient echo cines were acquired in LV base, midventricular, and apical slices with a nominal FOV 21 × 28 cm, matrix 108 × 144, 6 mm slice thickness, grid tag distance of 8 mm, TE 3.8 ms, TR 58 ms, temporal resolution 35 ms. Tagged images were analyzed using HARP software (Diagnosoft). Results Of 41 individuals, 23 were females. The group was divided by age into tertiles. Twist increased with age>60 years while LV end systolic volume (LVESV) decreased, with associated increases in ejection fraction (LVEF), systolic blood pressure (SBP) and pulse pressure (PP). End diastolic volume (LVEDV), LV mass, systolic circumferential strain and strain rate did not change with age so that LV Mass/ESV ratio increased (Table 1).

The impact of coronary calcium score and cardiac risk factors on coronary endothelial function

Methods Following navigator coronary MRA scout images, the LAD lumen was imaged in short axis before and during the cold pressor test (CPT) in normal controls and subjects with one or more atherosclerotic risk factors using either supine breath-hold double inversion T2 weighted spin echo imaging (38 subjects, 1.5 T Siemens Sonata) or prone breath-hold SSFP retrospectively gated cine imaging with a 4 element phased array carotid coil (39 subjects, 1.5 T Siemens Avanto). The % change in LAD lumen area with CPT was calculated. CT calcium scores were available or obtained by protocol in each subject and those undergoing prone imaging also had coronary CT angiography to exclude coronary stenoses. Linear associations between continuous variables were measured by Pearson and Spearman (non-parametric) correlation coefficients. ROC analysis was also performed. A p-value < 0.05 was deemed statistically significant.

The effects of respiratory cycle and body position on quantitative pulmonary perfusion by Magnetic Resonance Imaging

Methods Eight healthy volunteers (ages 30 to 69 years, 6 males) were prospectively enrolled. Using a saturation recovery SSFP technique, first pass perfusion images were acquired on a 1.5 T scanner. A voxel size of 4 × 2.6 × 15 mm3 was achieved in 3 parallel coronal slices in anterior, mid and posterior lung fields. After injection of gadopentetate (0.01 mmol/kg) dynamic images were acquired with a breath hold during inspiration and expiration in supine and prone positions. The contours of left and right lung parenchyma were drawn manually. The dynamic signal intensity in the pulmonary artery and in the lung parenchyma was measured over time and transferred to a proprietary model-independent deconvolution program. Absolute perfusion was then calculated using pulmonary artery dynamic contrast signal as input and that in the lung parenchyma as the distribution of tracer residence. Pulmonary perfusion was the average of the left and right lung perfusion in anterior, mid and posterior lung fields.

1094 Normal left ventricular structure and function: inflection point in age effects

Results Women had higher EF and lower EDVi, ESVi and LVMi compared to men. With increasing age, systolic blood pressure increased, EDVi and ESVi decreased, EF increased, LVMi did not show a clear trend and LVMi/ EDVi increased. However, there was an inflection point at age 50, with EDVi, ESVi and systolic blood pressure for each decade >50 differing significantly from all decades <50 but no differences among decades <50 or >50 years. (Table 1.) Conclusion Age and blood pressure related concentric remodeling results in reduced chamber volumes and increased EF in presence of constant LV mass in both men and women. There is an inflection point at age 50 when chamber volumes fall and blood pressure increases in both genders. Further studies are needed to determine the physiologic basis of changes occurring in LV structure and function at age 50. from 11th Annual SCMR Scientific Sessions Los Angeles, CA, USA. 1–3 February 2008