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Acute thoracolumbar fractures are commonly diagnosed by clinical symptoms and X-ray plain films. Computed tomography (CT) is used to assess vertebral body damage, posterior wall canal intrusion, and posterior column injury. Both of these imaging tools have helped to develop classifications systems that aid the clinician in differentiating stable versus unstable spinal injuries. Multidetector CT has become the standard of care in polytrauma patients. It provides superior evaluation of bony anatomy and has been reported to be more cost effective than X-ray plain films, particularly in the cervicothoracic junction and in thoracolumbar unstable burst fractures. One disadvantage might be the increase in radiation exposure. Another important limitation remains the inability to provide adequate assessment for ligamentous injury and spinal cord lesions. Disc and ligaments play an important role in fracture stability because the failure of the posterior tension band may lead to progressive kyphosis. The integrity of the posterior ligamentous complex has been included in recent fracture classification systems and treatment algorithms. MR imaging becomes essential for soft tissue injury assessment, especially when including T2-weighted sequences with fat suppression. MRI can now be considered key to accurate fracture classification, detection of occult and distant injuries, and as the basis for therapeutic decision making. It is therefore strongly recommended in the early assessment of spine trauma patients., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Introduction: The role of magnetic resonance imaging (MRI) has recently been enhanced in the diagnosis of thoracolumbar fractures due to its ability to examine soft tissue injury., Material and Methods: We conducted a prospective study to analyze the usefulness of MRI in fracture diagnosis and its influence on treatment decision making. Thirty-three patients were enrolled after suffering an acute traumatic thoracolumbar fracture. Osteoporotic or pathologic fractures were excluded. Fractures were initially classified using X-ray and CT scan following the AO classification. Afterward, a selective MRI protocol was performed with T1 and T2-weighted FS/STIR sequences. Subsequently, fractures were classified according to the TLICS system and reclassified following the AO system. Analysis was performed before and after MRI, focusing on: diagnostic changes, occult fractures and differences in treatment decision making., Results: Thirty patients (15 males, 15 females) with an average age of 39.9 years were studied. Forty-one fractures were initially diagnosed using plain X-rays and CT scans, while MRI diagnosed 50 fractures and 9 vertebral contusions. MRI modified our diagnosis in 40% of our patients (discovering 18 occult injuries), the classification of fracture pattern in 24% of the fractures (mostly upgrading type A to type B patterns) and the therapeutic management in 16% of our patients., Conclusions: MRI seems to be a useful tool in the evaluation of thoracolumbar acute fractures, as it allows a better visualization of the posterior complex integrity and of the levels involved, offering additional information compared to traditional diagnostic tools.

Objectives: The purpose of this study was to determine interobserver agreement for interpretation of magnetic resonance imaging (MRI) examinations of arrhythmogenic right ventricular dysplasia (ARVD) and to determine sensitivity and specificity of fat detection versus functional parameters measured by MRI., Background: The interobserver variability of MRI and the relative importance of different MRI parameters (fat detection, regional and global right ventricular [RV] function) for ARVD diagnosis is unknown., Methods: Two experienced observers blinded to the clinical history independently analyzed MRI datasets obtained from 40 patients evaluated for ARVD. Twenty normal subjects underwent MRI and served as control subjects. The MRI scans were performed according to a standard protocol on a 1.5-T scanner. The observers reported on fat infiltration, global and regional RV function, myocardial thinning, and chamber dilatation qualitatively. The RV volumes were measured on the cine sequences., Results: Interobserver kappa scores for fat infiltration, global and regional RV function, wall thinning, and RV outflow dilatation were 0.74, 0.94, 0.89, 0.93, and 0.93, respectively. Correlation coefficients between observers for RV end-diastolic volume, end-systolic volume, and ejection fraction were 0.93, 0.94, and 0.95, respectively (p < 0.001). Fifteen patients were diagnosed with ARVD using Task Force criteria. Sensitivity of fat infiltration, RV enlargement, and regional RV dysfunction for diagnosing ARVD was 84%, 68%, and 78%, and specificity was 79%, 96%, and 94%, respectively., Conclusions: Qualitative assessment of RV structure and function is highly reproducible for experienced observers. Among the qualitative parameters, fat infiltration is less reproducible and lacks specificity compared with RV kinetic abnormalities.

Purpose: To assess the reproducibility of Harmonic Phase (HARP) analysis of myocardial MR tagged images acquired in the Multi-Center Study of Atherosclerosis (MESA)., Methods: Using the HARP method, three independent observers performed two separate quantitative strain analyses of myocardial cine MR-tagging images blindly in 24 participants. The images were obtained in four different centers and analyzed at a single core lab. Each study comprised 3 short-axis slices subdivided in 12 segments (24 x 3 x 12 = 864 segments), each with three layers. Normal strains (circumferential [Ecc] and radial [Err]), principal strains (Lambda1, Lambda2), and the angle alpha (between Ecc-Lambda2) were calculated. Intraclass correlation coefficient (R) for peak systolic strains, and all pooled systolic and diastolic strain data were used to determine inter- and intraobserver agreement. Two observers also visually graded study quality. R values were related to the image quality in different myocardial regions and layers., Results: Overall, HARP yielded an excellent inter- and intraobserver agreement for peak systolic strain data (for Ecc, R = 0.84 and 0.89, respectively) and all systolic pooled data (for Ecc, interobserver R = 0.82, intraobserver R = 0.69-0.76). Both inter and intraobserver agreement were lower for diastolic pooled data (R = 0.69 and 0.58-0.62, respectively). There was a direct relationship between image quality and performance of the HARP analysis, with increasing inter- and intraobserver R values in studies with longer tag persistence. Both inter- and intraobserver agreement were better in the anterior and septal myocardial regions, and in the midwall layer. The intraobserver agreement was similar among the three observers., Conclusion: Employing the HARP method for quantitative strain analysis of myocardial MR tagged images provides a high inter- and intraobserver agreement. These good results are obtained in case of good to excellent MR image quality.

Left ventricular (LV) relaxation entails myocardial deformation that induces LV filling. Yet, the precise mechanisms of the earliest changes in tissue properties that characterize myocardial relaxation remain incompletely understood. Ten healthy volunteers (seven males), 25-43 yr, underwent tagged and cine MRI with high temporal resolution (25-35 ms). Normal strains including radial (E(rr)), circumferential (E(cc)), and longitudinal (E(ll)) strains, shear strains including E(cl) (circumferential-longitudinal), E(cr) (circumferential-radial), and E(rl) (radial-longitudinal), and principal strains (E(1), E(2), and E(3)) were calculated using a displacement field-fitting method. Temporal changes in angular strains indicative of shear and torsion release and normal strains were studied during late systole and early relaxation. The onset of individual relaxation strains was heterogeneous relative to LV filling. Shear strains (E(cr), E(rl), and E(cl)) and radial thinning were first to develop. Times of onset of E(cr), E(rl), E(cl), and E(rr) occurred 108, 93, 67, and 73 ms before aortic valve closure, respectively. E(ll), E(cc), and LV volume change commenced significantly later after the onset of diastolic shear strains and radial thinning. The onset of E(cc), E(ll), and LV volume change was noted 38 ms before aortic valve closure (P < or = 0.05 relative to the onset of shear strains and E(rr)). Myocardial relaxation is characterized by a three-dimensional unfolding deformation that includes release of torsion, shear, and radial thinning beginning before aortic valve closure. This unfolding pattern precedes longitudinal and circumferential elongation and may facilitate early diastolic filling.

Purpose: To assess electrocardiographically gated spin-echo (SE) and double inversion-recovery fast SE magnetic resonance (MR) imaging in the depiction of intramyocardial fat in cadaveric heart specimens and patients with arrhythmogenic right ventricular dysplasia (ARVD)., Materials and Methods: A phantom was used to determine the effective in-plane spatial resolution of SE and fast SE MR imaging protocols. Two cadavers with proved ARVD were imaged with identical sequences with spectrally selected fat suppression. Contrast-to-noise ratios (CNRs) of intramyocardial fat in the right ventricle (RV) were compared by using analysis of variance and Student t test with Bonferroni correction. Eleven patients with ARVD and 10 control subjects underwent fast SE MR imaging. Two blinded readers semiquantitatively evaluated images for fat conspicuity and image quality., Results: Fast SE MR imaging achieved better spatial resolution but lower CNR than that of gated SE imaging. CNRs in cadaveric specimens were higher for double R-R than for single R-R fast SE sequences for all section thicknesses (P <.0001). Absolute CNR values were higher for fat-suppressed fast SE sequences than for those without fat suppression. Cadaveric specimens demonstrated fatty infiltration from epicardium toward endocardium of the RV free wall. Intramyocardial fat was detected in eight of 11 (73%) patients with ARVD and in no control subjects (P <.001)., Conclusion: Intramyocardial fat detection in ARVD was better with fast SE MR imaging alone and combined with fat suppression than was gated SE MR imaging. When fast SE imaging is applied in vivo, however, breath-holding constraints limit the spatial resolution for RV fat detection., (Copyright RSNA, 2004)

Objectives: Intra-aortic balloon counterpulsation (IABC) can improve post-myocardial infarction (MI) outcomes, but the mechanisms of such effect remain unclear. We hypothesized that IABC augmentation reduces the extent of microvascular obstruction after acute infarction., Background: Microvascular obstruction or "no-reflow" (MO) has been shown to negatively influence left ventricular (LV) remodeling after myocardial infarction (MI)., Methods: Seventeen dogs underwent 90 min of coronary artery occlusion followed by reperfusion. Animals were then randomized to either IABC (n = 9) or control (n = 8); IABC augmentation was performed for 24 h after MI. Microvascular obstruction and infarct size by first-pass and delayed contrast-enhanced magnetic resonance imaging (MRI) were measured at 1 and 24 h after reperfusion and compared with postmortem infarct size and MO by microspheres., Results: Microvascular obstruction by MRI, expressed as percent LV mass, decreased significantly in IABC (4.9 +/- 2.2% to 3.6 +/- 1.5%) and increased in controls (3.4 +/- 0.5% to 4.9 +/- 1.1% from 1 to 24 h, respectively; p < 0.001). Similar results were found for MO defined by microspheres. In the control group, MO increased significantly, during 24 h of study (from 8.8 +/- 1.7% to 43.2 +/- 11.1% of infarcted myocardium; p < 0.05), whereas not important change was observed in the IABC group (from 21.3 +/- 7.1% to 25.8 +/- 14.7%; p < 0.05 vs. control at 24 h). Infarct size, measured by MRI, increased in both groups (13.2 +/- 1.8 to 15.5 +/- 2.1 from 1 to 24 h, respectively; p < 0.05)., Conclusions: Intra-aortic balloon counterpulsation augmentation performed after reperfusion improves myocardial perfusion at the tissue level, and reduces the extent of no-reflow caused by microvascular obstruction.

A method for visualizing myocardial infarction with a three-dimensional (3D) breath-hold gated acquisition was examined. By using variable sampling in time, whole heart coverage with a single volume acquisition was achieved in 24 heart beats. In a study of 35 patients, in whom 3D volume acquisition was compared with a two-dimensional (2D) acquisition, all regions of myocardial infarction were correctly identified at 3D examination. The mean imaging time for 12 section locations was 8.0 minutes +/- 3.0 with a 2D approach compared with 22 seconds +/- 4 with a 3D approach (P <.001). Advantages were also noted for infarct contrast-to-noise ratio: 60 +/- 37 for 3D versus 33 +/- 20 for 2D imaging (P <.001). No significant differences (P >.05) were noted at qualitative assessment of myocardial suppression, endocardial border visualization, respiratory and cardiac motion artifacts, or confidence of transmurality of the infarct., (Copyright RSNA, 2004)

Introduction: Magnet resonance imaging (MRI) findings in patients meeting Task Force criteria for the diagnosis of arrhythmogenic right ventricular dysplasia (ARVD) have not been systematically described. We report qualitative and quantitative MRI findings in ARVD using state-of-the-art MRI., Methods and Results: MRI was performed on 12 patients with ARVD who were prospectively diagnosed using the Task Force criteria. The imaging protocol included breath-hold double inversion recovery spin-echo and gradient-echo images. Ventricular volumes and dimensions were compared to 10 age- and sex-matched normal volunteers. High intramyocardial T1 signal similar to fat signal was observed in 9 (75%) of the 12 patients and in none of the controls. Right ventricular (RV) hypertrophy was seen in 5 (42%) patients, trabecular disarray in 7 (59%), and wall thinning in 3 (25%). Both the RV end-diastolic diameter and the outflow tract area were significantly higher in ARVD patients compared to controls (51.2 vs 43.2 mm, P < 0.01; and 14.5 vs 9.3 cm2, P < 0.01, respectively). ARVD patients had a higher RV end-diastolic volume index and lower RV ejection fraction compared with controls (127.4 vs 87.5, P < 0.01; and 41.6% vs 57%, P < 0.01, respectively)., Conclusion: High intramyocardial T1 signal indicative of fat is seen in a high percentage (75%) of patients who meet the Task Force criteria for ARVD. Trabecular disarray is seen more frequently than wall thinning and aneurysms. RV dimensions and volumes differ significantly in ARVD compared to controls, indicating a role for quantitative evaluation in the diagnosis of ARVD.

Background: Because ECG alterations caused by ischemia cannot be reliably detected in the high-field MRI environment, detection of wall motion abnormalities is often used to ensure patient safety during stress testing. However, an experienced observer is needed to detect these abnormalities. In this study, we investigate the use of fast harmonic phase (FastHARP) MRI for the quantitative, operator-independent detection of the onset of ischemia during acute coronary occlusion., Methods and Results: Eight mongrel dogs underwent an acute 2-minute closed-chest coronary artery occlusion while continuous FastHARP images were acquired. Full regional wall strain was determined every other heartbeat in a single short-axis imaging slice. After 5 minutes of reperfusion, a second 2-minute ischemic episode was induced during the acquisition of conventional cine wall-motion images. The time at which ECG alterations were observed during the first ischemic period was recorded. The time from occlusion to the detection of ischemia, based on a consensus of 2 blinded observers, was determined for MRI. No significant ischemia was present in 2 animals. In the remaining animals, the onset of ischemia was detected significantly earlier by FastHARP than by cine MRI (9.5+/-5 versus 33+/-14 seconds, P<0.01). HARP ischemia detection preceded ECG changes, on average, by 54 seconds., Conclusions: The rapid acquisition and detection of induced ischemia with FastHARP MRI shows promise as a nonsubjective method to diagnose significant coronary lesions during MR stress testing.

There has been tremendous progress for MR imaging depiction of cardiac morphology and function. Further advances toward achieving faster acquisition with real-time imaging, higher resolution for plaque imaging, and quantitative analysis are taking place at a rapid pace.

Cardiac MRI continues to develop and advance. MRI accurately depicts cardiac structure, function, perfusion, and myocardial viability with an overall capacity unmatched by any other single imaging modality. MRI is an accepted and widely utilized tool for cardiovascular research. Its clinical use has been limited, but is increasing because of its proven clinical efficacy, the proliferation of cardiac-capable MRI systems, and the development of improved pulse sequences. The following article reviews the landmark developments in this field, with an emphasis on recent progress in the evaluation of ischemic or acquired heart disease.