Synchronization and Registration of Cine Magnetic Resonance and Dynamic Computed Tomography Images of the Heart.

The synchronization and registration of dynamic computed tomography (CT) and magnetic resonance images (MRI) of the heart is required to perform a combined analysis of their complementary information. We propose a novel method that synchronizes and registers intrapatient dynamic CT and cine-MRI short axis view (SAX). For the synchronization step, a normalized cross-correlation curve is computed from each image sequence to describe the global cardiac dynamics. The time axes of these curves are then warped using an adapted dynamic time warping (DTW) procedure. The adaptation constrains the time deformation to obtain a coherent warping function. The registration step then computes the rigid transformation that maximizes the multiimage normalized mutual information of DTW-synchronized images. The DTW synchronization and the multiimage registration were evaluated using dynamic CT and cine-SAX acquisitions from nine patients undergoing cardiac resynchronization therapy. The distance between the end-systolic phases after DTW was used to evaluate the synchronization. Mean errors, expressed as a percentage of the RR-intervals, were 3.9% and 3.7% after adapted DTW synchronization against 10.8% and 11.3% after linear synchronization, for dynamic CT and cine-SAX, respectively. This suggests that the adapted DTW synchronization leads to a coherent warping of cardiac dynamics. The multiimage registration was evaluated using fiducial points. Compared to a monoimage and a two-image registration, the multiimage registration of DTW-synchronized images obtained the lowest mean fiducial error showing that the use of dynamic voxel intensity information improves the registration.

Diagnostic contributions of cardiac magnetic resonance imaging in patients presenting with elevated troponin, acute chest pain syndrome and unobstructed coronary arteries.

AIMS: Myocardial infarction with unobstructed coronary artery disease represents a serious diagnostic challenge. The role of cardiac magnetic resonance in the management of cardiomyopathies is increasing. We examined the diagnostic contributions of cardiac magnetic resonance in patients presenting with acute chest pain syndrome, elevated serum cardiac troponin concentrations and no significant coronary artery stenoses. METHODS: Over a 3-year period, 107 consecutive patients (mean age 43.5 years; 62% men) presented to our institution with acute onset of chest pain, elevated serum troponin concentration and unobstructed coronary arteries, and underwent 3-tesla cardiac magnetic resonance at a mean delay of 6.9 days. A diagnosis was made based on: wall motion abnormalities and pericardial effusion on cine mode; myocardial oedema on T2-weighted imaging; abnormalities on first-pass perfusion imaging; and late gadolinium enhancement on T1-weighted imaging. RESULTS: Cardiac magnetic resonance was normal in 10.3% of patients and contributed a diagnosis in 89.7%, including myocarditis in 59.9%, stress cardiomyopathy (takotsubo syndrome) in 14% and myocardial infarction in 15.8%. Patients with normal cardiac magnetic resonance had a significantly lower mean peak troponin concentration (2.6ng/mL) than patients with diagnostic cardiac magnetic resonance (9.7ng/mL; P=0.01). CONCLUSION: Cardiac magnetic resonance contributed a diagnosis in nearly 90% of patients presenting with acute chest pain, elevated serum troponin and unobstructed coronary arteries.

Cardiac MRI studies of transient left ventricular apical ballooning syndrome (takotsubo cardiomyopathy): a systematic review.

BACKGROUND: Since its first description in 1991, many cases of transient left ventricular apical ballooning syndrome (TLVABS) have been described, but the use of cardiac MRI in this condition is much more recent. METHODS AND RESULTS: We performed a systematic review of the present literature in the MEDLINE and EMBASE databases for relevant case series of TLVABS (>or=5 reported original cases, MRI analysis in the acute phase) and summarized the main results in a narrative synthesis. Only 8 studies met the eligible criteria, counting 176 patients (women: 95%; age: 68, stress trigger: 80%). MRI assessed an improvement of mean left ventricular ejection fraction from 39 (in the acute phase) to 64% (in the recovery phase). A right ventricular dysfunction was reported in 38%, a myocardial oedema in 81% and an apical thrombus in 5%. CONCLUSIONS: Although cardiac MRI is a very useful and inescapable tool in the management of TLVABS, there is no large published study concerning this topic. A systematic and multicentric register of TLVABS studied by cardiac MRI is necessary.

Peripheral vascular changes after home-based passive leg cycle exercise training in people with paraplegia: a pilot study.

OBJECTIVE: To determine the hemodynamic adaptations after home-based passive leg cycle exercise training in person with paraplegia. DESIGN: A randomized controlled trial (small cohort). SETTING: University department of physical medicine and rehabilitation. PARTICIPANTS: A volunteer sample of people with paraplegia (N=17). INTERVENTION: Subjects within the experimental group performed 36 passive cycling sessions at home. MAIN OUTCOME MEASURES: Before and after training, we measured heart rate and maximal and minimal femoral artery blood flow velocity at rest and immediately after a 10-minute session of passive cycling by using a quantitative duplex Doppler ultrasound. For each condition, we calculated the mean blood flow velocity and velocity index (VI), used as an indicator of peripheral resistance. RESULTS: At rest, after training, mean blood flow velocity (P=.08) and VI did not differ significantly in the experimental group compared with the pretraining values (nonparametric analysis). However, in this group, the postexercise mean blood flow velocity and VI are respectively increased and decreased after training (P<.05) compared with the pretraining values. No changes were noted in the control group. CONCLUSIONS: Six weeks of home-based passive cycling training have no significant effect on the rest hemodynamic values but increase the hemodynamic response to acute passive cycling exercise.

Mitochondriopathy: a rare aetiology of restrictive cardiomyopathy.

When diagnosing a restrictive hypertrophied cardiomyopathy, most echocardiographists consider cardiac amyloidosis as a possible cause, especially after the appearance of 'granular' sparkling echoes on a transthoracic echocardiography. However, other infiltrative diseases (i.e. metabolic myopathies, Gaucher, Hunter's, and Hurler's diseases) or storage cardiomyopathies (haemochromatosis, Fabry's disease, glycogen storage, and Niemann-Pick disease) should be considered. In this paper, we report on another unusual cause of restrictive cardiomyopathy of which all cardiologists should be aware.

Acute peripheral blood flow response induced by passive leg cycle exercise in people with spinal cord injury.

OBJECTIVE: To determine the acute femoral artery hemodynamic response in paraplegic subjects during a passive leg cycle exercise. DESIGN: Case series. SETTING: Department of physical medicine and rehabilitation in a university in France. PARTICIPANTS: A volunteer sample of 15 people with traumatic spinal cord injury. INTERVENTION: Subjects performed a 10-minute session of passive leg cycle exercise in the sitting position. MAIN OUTCOME MEASURES: We measured heart rate, maximal (Vmax), and minimal femoral artery blood flow velocity at rest and immediately after the passive leg cycle exercise, using quantitative duplex Doppler ultrasound. We calculated mean blood flow velocity (Vmean) and velocity index, representing the peripheral resistance, for each condition. RESULTS: Vmax and Vmean increased (from .80+/-.18 m/s to .96+/-.24 m/s, P<.01; and from .058+/-.02 m/s to .076+/-.03 m/s, P<.01; respectively) after 10 minutes of passive leg cycle exercise. Heart rate did not change. The velocity index decreased from 1.23+/-0.15 to 1.16+/-0.21 (P=.038). CONCLUSIONS: The results of this study suggest that acute passive leg cycle exercise increases vascular blood flow velocity in paralyzed legs of people with paraplegia. This exercise could have clinical implications for immobilized persons.

Concordance rate differences of 3 noninvasive imaging techniques to measure carotid stenosis in clinical routine practice: results of the CARMEDAS multicenter study.

BACKGROUND AND PURPOSE: To replace digital subtraction angiography (DSA) in carotid stenosis evaluation, noninvasive imaging techniques have to reach a high concordance rate. Our purpose is to compare the concordance rates of contrast-enhanced MR angiography (CEMRA) and CT angiography (CTA) with Doppler ultrasound (DUS) in clinical routine practice. METHODS: We evaluated prospectively with DUS, CEMRA, and CTA 150 patients suspected of carotid stenosis. The overall concordance rates of the 3 techniques were calculated for symptomatic stenosis > or =50% and > or =70%, for asymptomatic stenosis > or =60%, and for occlusion. For the carotid arteries treated by surgery (n=97), the results of each method and combined techniques were recorded, and misclassification rates were evaluated from surgical reports. RESULTS: The overall concordance rates of DUS-CEMRA, DUS-CTA, and CEMRA-CTA were not statistically different. However, the concordance rate of DUS-CEMRA (92.53%) was significantly higher than that for DUS-CTA (79.10%) in the surgical asymptomatic stenosis group (P=0.0258). CTA considered alone would misclassify the stenosis in a significant number of cases (11 of 64) in the surgical asymptomatic group compared with CEMRA (3 of 67) and DUS (1 of 66) (P=0.0186 versus MRA, P=0.0020 versus DUS). CONCLUSIONS: With the techniques as utilized in our study, the overall concordance rates of combined noninvasive methods are similar for measuring carotid stenosis in clinical routine practice, but in asymptomatic carotid stenosis, the decision making for surgery is significantly altered if DUS and CTA are considered in place of DUS and CEMRA.