The relationship between myocardial microstructure and strain in chronic infarction using cardiovascular magnetic resonance diffusion tensor imaging and feature tracking.

BACKGROUND: Cardiac diffusion tensor imaging (cDTI) using cardiovascular magnetic resonance (CMR) is a novel technique for the non-invasive assessment of myocardial microstructure. Previous studies have shown myocardial infarction to result in loss of sheetlet angularity, derived by reduced secondary eigenvector (E2A) and reduction in subendocardial cardiomyocytes, evidenced by loss of myocytes with right-handed orientation (RHM) on helix angle (HA) maps. Myocardial strain assessed using feature tracking-CMR (FT-CMR) is a sensitive marker of sub-clinical myocardial dysfunction. We sought to explore the relationship between these two techniques (strain and cDTI) in patients at 3 months following ST-elevation MI (STEMI). METHODS: 32 patients (F = 28, 60 ± 10 years) underwent 3T CMR three months after STEMI (mean interval 105 ± 17 days) with second order motion compensated (M2), free-breathing spin echo cDTI, cine gradient echo and late gadolinium enhancement (LGE) imaging. HA maps divided into left-handed HA (LHM, - 90 < HA < - 30), circumferential HA (CM, - 30° < HA < 30°), and right-handed HA (RHM, 30° < HA < 90°) were reported as relative proportions. Global and segmental analysis was undertaken. RESULTS: Mean left ventricular ejection fraction (LVEF) was 44 ± 10% with a mean infarct size of 18 ± 12 g and a mean infarct segment LGE enhancement of 66 ± 21%. Mean global radial strain was 19 ± 6, mean global circumferential strain was - 13 ± - 3 and mean global longitudinal strain was - 10 ± - 3. Global and segmental radial strain correlated significantly with E2A in infarcted segments (p = 0.002, p = 0.011). Both global and segmental longitudinal strain correlated with RHM of infarcted segments on HA maps (p < 0.001, p = 0.003). Mean Diffusivity (MD) correlated significantly with the global infarct size (p < 0.008). When patients were categorised according to LVEF (reduced, mid-range and preserved), all cDTI parameters differed significantly between the three groups. CONCLUSION: Change in sheetlet orientation assessed using E2A from cDTI correlates with impaired radial strain. Segments with fewer subendocardial cardiomyocytes, evidenced by a lower proportion of myocytes with right-handed orientation on HA maps, show impaired longitudinal strain. Infarct segment enhancement correlates significantly with E2A and RHM. Our data has demonstrated a link between myocardial microstructure and contractility following myocardial infarction, suggesting a potential role for CMR cDTI to clinically relevant functional impact.

Effects of hyperaemia on left ventricular longitudinal strain in patients with suspected coronary artery disease : A first-pass stress perfusion cardiovascular magnetic resonance imaging study.

AIMS: Myocardial perfusion imaging during hyperaemic stress is commonly used to detect coronary artery disease. The aim of this study was to investigate the relationship between left ventricular global longitudinal strain (GLS), strain rate (GLSR), myocardial early (E') and late diastolic velocities (A') with adenosine stress first-pass perfusion cardiovascular magnetic resonance (CMR) imaging. METHODS AND RESULTS: 44 patients met the inclusion criteria and underwent CMR imaging. The CMR imaging protocol included: rest/stress horizontal long-axis (HLA) cine, rest/stress first-pass adenosine perfusion and late gadolinium enhancement imaging. Rest and stress HLA cine CMR images were analysed using feature-tracking software for the assessment of myocardial deformation. The presence of perfusion defects was scored on a binomial scale. In patients with hyperaemia-induced perfusion defects, rest global longitudinal strain GLS (-16.9 ± 3.7 vs. -19.6 ± 3.4; p-value = 0.02), E' (-86 ± 22 vs. -109 ± 38; p-value = 0.02), GLSR (69 ± 31 vs. 93 ± 38; p-value = 0.01) and stress GLS (-16.5 ± 4 vs. -21 ± 3.1; p < 0.001) were significantly reduced when compared with patients with no perfusion defects. Stress GLS was the strongest independent predictor of perfusion defects (odds ratio 1.43 95% confidence interval 1.14-1.78, p-value <0.001). A threshold of -19.8% for stress GLS demonstrated 78% sensitivity and 73% specificity for the presence of hyperaemia-induced perfusion defects. CONCLUSIONS: At peak myocardial hyperaemic stress, GLS is reduced in the presence of a perfusion defect in patients with suspected coronary artery disease. This reduction is most likely caused by reduced endocardial blood flow at maximal hyperaemia because of transmural redistribution of blood flow in the presence of significant coronary stenosis.

High-resolution free-breathing automated quantitative myocardial perfusion by cardiovascular magnetic resonance for the detection of functionally significant coronary artery disease.

AIMS: Current assessment of myocardial ischaemia from stress perfusion cardiovascular magnetic resonance (SP-CMR) largely relies on visual interpretation. This study investigated the use of high-resolution free-breathing SP-CMR with automated quantitative mapping in the diagnosis of coronary artery disease (CAD). Diagnostic performance was evaluated against invasive coronary angiography (ICA) with fractional flow reserve (FFR) measurement. METHODS AND RESULTS: Seven hundred and three patients were recruited for SP-CMR using the research sequence at 3 Tesla. Of those receiving ICA within 6 months, 80 patients had either FFR measurement or identification of a chronic total occlusion (CTO) with inducible perfusion defects seen on SP-CMR. Myocardial blood flow (MBF) maps were automatically generated in-line on the scanner following image acquisition at hyperaemic stress and rest, allowing myocardial perfusion reserve (MPR) calculation. Seventy-five coronary vessels assessed by FFR and 28 vessels with CTO were evaluated at both segmental and coronary territory level. Coronary territory stress MBF and MPR were reduced in FFR-positive (≤0.80) regions [median stress MBF: 1.74 (0.90-2.17) mL/min/g; MPR: 1.67 (1.10-1.89)] compared with FFR-negative regions [stress MBF: 2.50 (2.15-2.95) mL/min/g; MPR 2.35 (2.06-2.54) P < 0.001 for both]. Stress MBF ≤ 1.94 mL/min/g and MPR ≤ 1.97 accurately detected FFR-positive CAD on a per-vessel basis (area under the curve: 0.85 and 0.96, respectively; P < 0.001 for both). CONCLUSION: A novel scanner-integrated high-resolution free-breathing SP-CMR sequence with automated in-line perfusion mapping is presented which accurately detects functionally significant CAD.

Quantitative analysis of transmural gradients in myocardial perfusion magnetic resonance images.

Conventional quantitative assessments of myocardial perfusion analyze the temporal relation between the arterial input function and the myocardial signal intensity curves, thereby neglecting the important spatial relation between the myocardial signal intensity curves. The new method presented in this article enables characterization of sub-endocardial to sub-epicardial gradients in myocardial perfusion based on a two dimensional, "gradientogram" representation, which displays the evolution of the transmural gradient in myocardial contrast uptake over time in all circumferential positions of the acquired images. Moreover, based on segmentation in these gradientograms, several new measurements that characterize transmural myocardial perfusion distribution over time are defined. In application to clinical image data, the new two-dimensional representations, as well as the newly defined measurements revealed a clear distinction between normal perfusion and inducible ischaemia. Thus, the new measurements may serve as diagnostic markers for the detection and characterization of epicardial coronary and microvascular disease.

Assessment of tissue edema in patients with acute myocardial infarction by computer-assisted quantification of triple inversion recovery prepared MRI of the myocardium.

The aim of this study was to design a computer algorithm to assess the extent of cardiac edema from triple inversion recovery MR images of the human left ventricular myocardium. Twenty-one patients presenting with acute myocardial infarction were scanned within 48 h of the onset of symptoms. Eight patients were scanned a second time, 4 weeks after the initial event. Myocardial edema was detected in 27 of 29 studies using visual contour-based manual segmentation. A reference standard, created from the segmentations of three raters by voxel-wise majority voting, was compared to the edema mass estimates obtained using a newly developed computer algorithm. At baseline (n=20), the reference standard yielded an edema mass of 16.4±15.0 g (mean±SD) and the computer algorithm edema mass was 16.4±12.6 g. At follow-up (n=7), the reference standard edema mass was 7.1±4.4 g compared to 16.3±7.7 g at baseline. Computer algorithm estimates showed the same pattern of change with 5.7±5.7 g at follow-up compared to 20.8±13.8 g at baseline. Although there was a significant degree of discrepancy between reference standard and computer algorithm estimates of edema mass in individual patients, their overall agreement was good, with intraclass correlation coefficient ICC(3, 1)=0.753.

ESC 2019 guidelines on chronic coronary syndromes: could calcium scoring improve detection of coronary artery disease in patients with low risk score. Findings from a retrospective cohort of patients in a district general hospital.

BACKGROUND: The European Society of Cardiology (ESC) published an updated stable chest pain guideline in 2019, recommending the use of an updated pre-test probability (PTP) risk score (RS) to assess the likelihood of coronary artery disease (CAD). We sought to compare the 2019 and 2013 PTPRS in a contemporary cohort of patients. METHODS: 612 patients who were investigated with computed tomography coronary angiography (CTCA) for stable chest pain were included in a retrospective analysis. RESULTS: There were 255 patients with 2019 PTPRS 15-50% with a 9% yield of severe CAD on CTCA, compared with 402 patients and a 4% yield using the 2013 PTPRS (p = 0.01). 355 patients had a 2019 PTPRS of <15%, with 3% found to have severe CAD, compared with 67 patients and none with severe CAD using the 2013 PTPRS (p = 0.14). 336 of patients with 2019 PTPRS of <15% had a calcium score as part of the CTCA. 223 of these had a zero calcium score and only one had severe CAD. In comparison, 113 patients had a positive calcium score, and 10 (9%) had severe CAD (p < 0.001). DISCUSSION: The ESC 2019 PTPRS classifies more patients as at lower risk of CAD and hence reduces the risk overestimation associated with the 2013 PTPRS. However, in patients with a 2019 PTPRS of <15%, who would not be investigated, the use of the calcium score detected the majority of patients with significant CAD, who may benefit from secondary prevention and an associated mortality benefit as per the SCOT-Heart trial.

Cardiovascular MRI evidence of reduced systolic function and reduced LV mass in rheumatoid arthritis: impact of disease phenotype.

The accelerated risk of cardiovascular disease (CVD) in Rheumatoid Arthritis (RA) requires further study of the underlying pathophysiology and determination of the at-risk RA phenotype. Our objectives were to describe the cardiac structure and function and arterial stiffness, and association with disease phenotype in patients with established) RA, in comparison to healthy controls, as measured by cardiovascular magnetic resonance imaging (CMR). 76 patients with established RA and no history of CVD/diabetes mellitus were assessed for RA and cardiovascular profile and underwent a non-contrast 3T-CMR, and compared to 26 healthy controls. A univariable analysis and multivariable linear regression model determined associations between baseline variables and CMR-measures. Ten-year cardiovascular risk scores were increased in RA compared with controls. Adjusting for age, sex and traditional cardiovascular risk factors, patients with RA had reduced left ventricular ejection fraction (mean difference - 2.86% (- 5.17, - 0.55) p = 0.016), reduced absolute values of mid systolic strain rate (p < 0.001) and lower late/active diastolic strain rate (p < 0.001) compared to controls. There was evidence of reduced LV mass index (LVMI) (- 4.56 g/m2 (- 8.92, - 0.20), p = 0.041). CMR-measures predominantly associated with traditional cardiovascular risk factors; male sex and systolic blood pressure independently with increasing LVMI. Patients with established RA and no history of CVD have evidence of reduced LV systolic function and LVMI after adjustment for traditional cardiovascular risk factors; the latter suggesting cardiac pathology other than atherosclerosis in RA. Traditional cardiovascular risk factors, rather than RA disease phenotype, appear to be key determinants of subclinical CVD in RA potentially warranting more effective cardiovascular risk reduction programs.

Comparison of 99mTc tetrofosmin gated SPECT measurements of left ventricular volumes and ejection fraction with MRI over a wide range of values.

The calculation of ejection fraction using gated single photon emission computed tomography (SPECT) has been widely validated against a range of other techniques. There have been fewer studies validating left ventricular volumes. We compared quantitative gated SPECT (QGS) with magnetic resonance imaging (MRI) measurements of left ventricular ejection fraction and end diastolic volume in 50 patients with a large range of ventricular dimensions. MRI data were obtained using a turbo gradient echo pulse sequence (TGE) in 17 patients and a steady state free precession pulse sequence (SSFP) in 33 patients. There was good correlation between ejection fraction and end diastolic volume measurements from SPECT and MRI (r=0.82, r=0.90, respectively) but the mean SPECT values were significantly lower (ejection fraction, 6.6+/-6.4% points; end diastolic volume, 18.4+/-25.4 ml) than those obtained from MRI. Bland-Altman analysis showed some large differences in individual patients but no trends in the data either in ejection fraction over a range from 15% to 70% or in end diastolic volume, range 75-400 ml. SSFP gave a larger difference for end diastolic volume measurement compared to SPECT than did TGE, although this difference did not reach significance. Both SSFP and TGE gave similar values for the difference between MRI and SPECT for the measurement of ejection fraction. We suggest that the difference in EF may be a result of 8 frames being used for gating in QGS but 12-18 for MR. Differences in volumes may be related to the different spatial resolution and the exclusion or inclusion of trabeculation and papillary muscles between SPECT and MRI. Differences between SSFP and TGE may be caused by differing delineation of the endocardial border, dependent on the particular acquisition sequence. In conclusion, QGS values correlated well with MRI, but a correction factor may be needed if direct comparison is made.

Developments in cardiac ultrasound.

This article gives an overview of recent developments in cardiac ultrasound for the general hospital physician. It discusses contrast echocardiography, harmonic imaging, three-dimensional echocardiography, Doppler tissue imaging and perfusion imaging and give an outlook on future perspectives.

Serum 25 hydroxy-vitamin D does not exhibit an acute phase reaction after acute myocardial infarction.

BACKGROUND: There is growing epidemiological evidence linking serum 25 hydroxy-vitamin D (25(OH)D) concentrations to outcome in cardiovascular and other diseases. We have studied patients with acute myocardial infarction (AMI) to determine if they exhibit an acute phase reaction affecting 25(OH)D. METHODS: Patients (n=32) with first AMI who had been treated with primary percutaneous coronary intervention within 12 h of symptom onset had venous blood samples taken two days, one week, one month and three months after presentation. Samples were analysed for troponin I, C-reactive protein (CRP) and 25(OH)D. RESULTS: All patients had significant rises in troponin confirming the myocardial damage and CRP, both of which resolved by 28 days. In contrast, 25(OH)D remained unchanged throughout the 90-day observation period with a median concentration of 46 nmol/L. CONCLUSION: Serum 25(OH)D does not change after AMI and is likely to be a reliable marker of vitamin D status in patients with cardiovascular disease.

Evaluation of the effect of myocardial segmentation errors on myocardial blood flow estimates from DCE-MRI.

Quantitative analysis of cardiac dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) perfusion datasets is dependent on the drawing (manually or automatically) of myocardial contours. The required accuracy of these contours for myocardial blood flow (MBF) estimation is not well understood. This study investigates the relationship between myocardial contour errors and MBF errors. Myocardial contours were manually drawn on DCE-MRI perfusion datasets of healthy volunteers imaged in systole. Systematic and random contour errors were simulated using spline curves and the resulting errors in MBF were calculated. The degree of contour error was also evaluated by two recognized segmentation metrics. We derived contour error tolerances in terms of the maximum deviation (MD) a contour could deviate radially from the 'true' contour expressed as a fraction of each volunteer's mean myocardial width (MW). Significant MBF errors were avoided by setting tolerances of MD ≤ 0.4 MW, when considering the whole myocardium, MD ≤ 0.3 MW, when considering six radial segments, and MD ≤ 0.2 MW for further subdivision into endo- and epicardial regions, with the exception of the anteroseptal region, which required greater accuracy. None of the considered segmentation metrics correlated with MBF error; thus, both segmentation metrics and MBF errors should be used to evaluate contouring algorithms.

Safety and diagnostic accuracy of stress cardiac magnetic resonance imaging vs exercise tolerance testing early after acute ST elevation myocardial infarction.

OBJECTIVE: To determine the safety and diagnostic accuracy of adenosine-stress cardiac magnetic resonance (CMR) perfusion imaging early after acute ST elevation myocardial infarction (STEMI) compared with standard exercise tolerance testing (ETT). DESIGN AND SETTING: Cross sectional observational study in a university teaching hospital. PATIENTS: 35 patients admitted with first acute STEMI. INTERVENTIONS: All patients underwent a CMR imaging protocol which included rest and adenosine-stress perfusion, viability, and cardiac functional assessment. All patients also had an ETT (modified Bruce protocol) and x ray coronary angiography. MAIN OUTCOME MEASURES: Safety and diagnostic accuracy of adenosine-stress perfusion CMR vs ETT early after STEMI in identifying patients with significant coronary stenosis (>or=70%) and the need for coronary revascularisation. Also, to determine if CMR can distinguish between ischaemia in the peri-infarct zone and ischaemia in remote myocardium. RESULTS: CMR imaging was well tolerated (all patients completed the protocol) and no complications occurred. CMR was more sensitive (86% vs 48%, p = 0.0074) and more specific than ETT (100% vs 50%, p<0.0001) for detecting significant coronary stenosis, and more sensitive for predicting revascularisation (94% vs 56%, p = 0.039). Inducible ischaemia in the infarct related artery territory was seen in 21 of 35 patients and was associated with smaller infarct size and less transmurality of infarction. CONCLUSIONS: Adenosine-stress CMR imaging is safe early after acute STEMI and identifies patients with significant coronary stenosis more accurately than ETT.

[Treatment of withdrawal symptoms using clonidine during pregnancy]. / Entzugsbehandlung mit Clonidin während der Schwangerschaft.

In order to prevent symptoms of drug withdrawal during pregnancy, we treated a woman with clonidine, an alpha-2 adrenergic agonist with central and peripheral actions. We saw a good response of the withdrawal symptoms without any period of severe hypotension or bradycardia. Two healthy babies were subsequently delivered by cesarean section.

[Slowing down of the EEG during hypoventilation in emergence from anesthesia]. / EEG-Verlangsamung bei Hypoventilation in der Narkoseausleitung.

Electroencephalographic (EEG) recordings were made using a "Narkograph", which performs an automatic on-line interpretation of electroencephalographic data obtained during anesthesia. The EEG was classified into one of 13 stages from A (awake) to F (very deep narcosis). In 20 of roughly 600 patients EEG changes were observed that could not be explained by the effects of anesthetics. Slowing of the EEG occurred during the transition from controlled to spontaneous ventilation and disappeared after minute ventilation increased. The alterations seen during hypoventilation were similar to the effects of hypoxia described in the literature. During the slowing in the rough EEG, waves appeared that were very regularly formed and corresponded to sharp peaks in the power spectrum. These features are rather atypical of the effects of anesthetics such as thiopental, propofol, halothane, isoflurane, and enflurane and were not observed when patients went back to sleep after extubation. If depth of anesthesia is monitored by EEG recording, clinical circumstances should be taken into account because conditions such as hypoxia may cause alterations of the EEG that bear a resemblance to the effects of anesthetics.

[Significance of coupling intervals of spontaneous ventricular arrhythmias in long-term ECG in patients with coronary heart disease]. / Die Bedeutung der Kopplungsintervalle von spontanen Kammerarrhythmien im Langzeit-EKG bei Patienten mit koronarer Herzkrankheit.

Coupling intervals of premature ventricular beats and complex arrhythmias were studied by 24-h ambulatory electrocardiographic recordings in 76 patients (35 sudden death patients and 41 survivors) with coronary artery disease. A first Holter (HM 1) was recorded at the time of left ventricular angiography and a second Holter (HM 2) after a mean interval of 34.4 +/- 11.2 months (range 2-61 months). All patients were only treated medically. The mean heart rate was significantly faster in patients who died suddenly than in survivors in both HM 1 and HM 2 (p less than 0.01). In HM 1, there were no significant differences in mean coupling intervals between patients who died suddenly and survivors, whereas in HM 2, coupling intervals of premature ventricular beats and couplets were significantly shorter in patients who died suddenly than in survivors (p less than 0.05). Patients with coupling intervals for couplets less than 500 ms died significantly earlier than those patients with coupling intervals greater than 500 ms (p less than 0.05). Our data show that there is a relationship between heart rate, coupling intervals and sudden death. Patients with fast heart rates and coupling intervals for couplets less than 500 ms represent a group at high risk of sudden death.

Postmortem evaluation of four randomly selected automated biopsy devices for transthoracic lung biopsy.

PURPOSE: To evaluate four automated devices to achieve transthoracic lung biopsy. METHODS: Transthoracic lung biopsy specimens were obtained randomly from 21 human cadavers with unsuspicious lungs using Biopty (18- and 20-gauge), BIP (18 and 20-gauge), ASAP (18 gauge), and Autovac (18- and 20-gauge) devices. A total of 63 biopsies were carried out with each device and each needle diameter. The same devices and needles were then used randomly for biopsy of peripheral lung metastases. Specimens obtained during both parts of the study were analyzed for the area of tissue on the histologic section, adequacy of tissue for diagnosis, tissue preservation, and crush artifact. The examining pathologist was kept unaware of which procedure was used to obtain the specimens and the cadavers' clinical history. RESULTS: The Biopty 18-gauge device performed statistically better than any other of the evaluated systems for biopsy of normal lung parenchyma (p < 0.05). For biopsy of lung metastases, the differences between the devices and needle diameters were less, although the Biopty 18-gauge device performed better than the Autovac 18-gauge, BIP 18-gauge, and all 20-gauge devices for the area of tissue on the histologic section (p < 0.05). The results of the full-cut Autovac biopsy system were remarkable because of the large number of biopsies during which no tissue was obtained. CONCLUSION: Automated biopsy devices can obtain high quality lung specimens sufficient for definite histopathologic diagnosis. However, additional clinical studies on the use of automated biopsy devices for lung biopsy are mandatory.

Steady-state free precession magnetic resonance imaging of the heart: comparison with segmented k-space gradient-echo imaging.

Steady-state free precession imaging is a promising technique for cardiac magnetic resonance imaging (MRI), as it provides improved blood/myocardial contrast in shorter acquisition times compared with conventional gradient-echo acquisition. The better contrast could improve observer agreement and automatic detection of cardiac contours for volumetric assessment of the ventricles, but measurements might differ from those obtained using conventional methods. We compared volumetric measurements, observer variabilities, and automatic contour detection between a steady-state free precession imaging sequence (BFFE = balanced fast field echo) and segmented k-space gradient-echo acquisition (TFE = turbo field echo) in 41 subjects. With BFFE, significantly higher end-diastolic and end-systolic volumes and lower wall thickness, ventricular mass, ejection fraction, and wall motion were observed (P < 0.0001), while interobserver variabilities were lower and automatic contour detection of endocardial contours was more successful. We conclude that the improved image quality of BFFE reduces the observer-dependence of volumetric measurements of the left ventricle (LV) but results in significantly different values in comparison to TFE measurements.

Qualitative and quantitative analysis of regional left ventricular wall dynamics using real-time magnetic resonance imaging: comparison with conventional breath-hold gradient echo acquisition in volunteers and patients.

A real-time magnetic resonance imaging (MRI) acquisition sequence was evaluated for the assessment of left ventricular wall motion (WM) and wall thickening (WT). Ten normal volunteers and 21 patients were studied. Short-axis cine images of the left ventricle (LV) were acquired with a fast gradient echo and an ultrafast segmented echo-planar imaging (EPI) sequence. Qualitative and quantitative analysis of WM and WT was performed on a segmental basis. Qualitative scores agreed between the two methods in 691 of 724 segments (95.4%) with good reproducibility. Quantitative measurements of WM and WT were significantly lower (P < 0.001) with the real-time method (WM: mean bias, 0.49 mm; WT: mean bias, 0.61 mm). The largest differences were observed in the anterior and lateral segments and in patients with dilated ventricles. The lower resolution of the real-time sequence and artifacts was probably responsible for these differences. In conclusion, real-time cardiac MRI can be used for qualitative assessment of wall dynamics but is presently insufficient for quantitative analysis.

Cine MRI using steady state free precession in the radial long axis orientation is a fast accurate method for obtaining volumetric data of the left ventricle.

In this study we assessed the use of a steady state free precession (SSFP) cine sequence in a series of radially orientated long axis slices for the measurement of left ventricular volumes and mass. We validated the radial long axis approach in phantoms and ex vivo porcine hearts and applied it to normal volunteers and patients using the SSFP and turbo gradient-echo (TGE) sequences. High quality images were obtained for analysis, and the measured volumes with radial long axis SSFP sequence correlated well with short axis TGE and SSFP volumes (r > 0.98). The best interobserver agreement for left ventricular volumes was obtained using SSFP in the long axis radial orientation (variability < 2.3%). We conclude that this combination of sequence and scan orientation has intrinsic advantages for image analysis due to the improved contrast and the avoidance of errors associated with the basal slice in the short axis orientation.