SSFP Sequence Research Articles

Steady‐State Free Precession MRI Imaging as a Screening Evaluation for Vestibular Schwannoma

Objectives: (1) Compare noncontrast steady-state free precession (SSFP, also called FIESTA, CISS, and bFFE) magnetic-resonance imaging (MRI) to contrast-enhanced full sequence MRI for initial evaluation of retrocochlear pathology. (2) Assess the sensitivity and specificity of SSFP alone versus complete contrast-enhanced MRI as the gold standard. Methods: Retrospective review of a tertiary care center radiology imaging database from 2006 to present was performed. Based on statistical power analysis, 50 studies with identified vestibular schwannomas and 53 studies with normal internal auditory canal (IAC) findings were included. Four expert reviewers performed blinded, randomized evaluation of non-contrast SSFP sequence and contrast-enhanced MRI studies to evaluate for retrocochlear pathology. MRI reports from the original studies were used as the gold standard. Using XLSTAT™ statistical software, data were analyzed using a 2-sided z-test of one proportion for each reviewer’s sensitivity and specificity against a 95% standard. Inter-reader reliability was determined using kappa analysis. Results: Four reviewers, including 2 neuroradiologists, one neurotologist, and one neurosurgeon had 100% specificity. Average sensitivity was 96% (range, 94-100%). There was no statistically significant difference when each sensitivity and specificity was compared against a 95% standard or in results between reviewers. Tumors eccentric in the IAC or with significant artifact were more likely to not be identified. Conclusions: Noncontrast SSFP sequence MRI may be an effective initial study to perform for evaluation of vestibular schwannomas. Given its shorter duration (5 minutes versus 25 minutes) as well as the noncontrast method, clear advantages exist for this method.

SU‐E‐J‐131: Automatic Detection of Gold Fiducial Markers On MR Images Using the RASOR Technique

Purpose:The detection of gold fiducial markers on MR images is important for CT‐MR registration and will be key to upcoming MRI‐only treatment planning. Visualization of gold fiducials with MRI is, however, challenging as seeds lead to small signal voids that are difficult to detect on regular MR scans. Here, we demonstrate that by using a balanced radial SSFP sequence in combination with an off‐resonance reconstruction, gold fiducials can be given a positive contrast facilitating automatic detection.Methods:Three gold fiducials (HA2 Medizintechnik, Germany, 1x 5 mm²) were placed in three orthogonal orientations in an agarose gel phantom. We used a 3D stack of stars transient balanced gradient echo (tbGE) sequence with SPAIR fat suppression (TR/TE = 3.3/1.63ms, 1×1×2 mm³ acquired voxels, BW=1085Hz/vox). To create positive contrast at the seed locations the RASOR technique employs an additional off‐resonance reconstruction at 3000 Hz. Background‐suppression was obtained by subtracting the on‐resonance image twice from the off‐resonance image.Results:The short echo time of the sequence combined with a “balanced” gradient scheme resulted in well localized and sharp signal voids at fiducial locations. By employing RASOR reconstruction the gold fiducials were depicted hyperintense and allowed determination of the locatation and orientation of the fiducials. The radial readout ensures accurate localization as any susceptibility induced geometrical shift for a radial readout line, is balanced by an opposite radial readout. Thus the centre‐of‐gravity of the hyperintensity reflects the true position of the fiducials.Conclusion:A radial balanced sequence in combination with short TR and TR and high spatial resolution, results in accurate depiction of gold fiducials while being standardly available on MR systems. The RASOR reconstruction results in a positive contrast facilitating automatic detection. This enables automatic registration between CT and MRI based on fiducial markers, and in the may warrant an MRI‐only planning approach.

Cardiac magnetic resonance strain imaging in systemic light chain amyloidosis

Background Systemic light chain amyloidosis (AL) is associated with a high cardiovascular morbidity and mortality. Cardiovascular involvement and determination of prognosis is underestimated by standard imaging parameters. Recently, cardiac deformation analysis of global circumferential and longitudinal strain has been shown to have great clinical impact on the assessment of prognosis and survival in this rare disease. For further analysis we applied the novel non-invasive post-processing feature tracking imaging (FTI) algorithm on pre-acquired regular CMR SSFP images in healthy volunteers and in patients with AL and sought to investigate different strain patterns. Methods 87 patients (mean age 60 ± 11 years) with biopsy proven systemic AL were scanned on a clinical 1.5 T CMR scanner (Philips Achieva). Short axis slices covering entirely both ventricles as well as 2-, 3- and 4-chamber views were acquired using standard SSFP-sequences before initiation of any specific pharmaceutical AL therapies. The control group consisted of 47 healthy subjects (mean age 59 ± 5 years). Besides the standard CMR parameters for volumes, ejection fraction, myocardial mass and wall thickness we measured the circumferential and the longitudinal strain on cine SSFP images by the application of the post-processing FTI algorithm. Results In patients with AL mean longitudinal strain from the four chamber view (-15.9 ± 5.6% vs -21.3 ± 4%, p < 0.05) as well as midventricular mean circumferential strain (-22.8 ± 6.7% vs -25.1 ± 4.5%, p < 0.05) were significantly reduced compared to healthy subjects. Global circumferential strain and global longitudinal strain correlated with left ventricular ejection fraction (r = -0.61, p < 0.05; r = -0.62, p < 0.05). In the subgroup analysis of AL patients with a mean wall thickness less than 12 mm global longitudinal strain showed significantly reduced values in comparison to healthy control subjects (-18.3 ± 5.3% vs -21.3 ± 4%, p < 0.05), whereas global circumferential strain did not show a significant difference. Patients with an ejection fraction ≥55% already had reduced global longitudinal strains (-18 ± 4.7% vs -21.3 ± 4%, p < 0.05), again global circumferential strain did not show a significant difference. Conclusions FTI strain analysis derived from regular cine SSFP sequences offers the possibility for a fast quantitative assessment of myocardial strain imaging patterns without additional and time-consuming strain imaging sequences. FTI strain analysis provides important insight into the disturbed contraction in AL. Further investigations are necessary to analyze the impact of this new method on the prediction of clinical outcome in AL patients. Funding None.

Assessment of myocardial strain in patients with myocarditis by cardiac magnetic resonance imaging

Background Myocarditis is associated with a considerable morbidity and mortality in the acute phase as well as in the long term. It is found in up to 12% of young adults with sudden cardiac death and is regarded as a cause of dilated cardiomyopathy which is currently the most frequent reason for heart transplantation. Therefore, techniques for the diagnosis and the assessment of prognosis are of great interest. In this study we evaluate the novel post-procession feature tracking imaging (FTI) algorithm for strain analysis on patients with myocarditis. Methods We retrospectively included 36 patients (31 male, 5 female) who were admitted with acute myocarditis. A control group (31 male, 5 female) was drawn from a reference population of proven healthy volunteers and was matched with regard to age and gender. CMR imaging was performed on a 1.5 T whole-body MRI (Achieva, Philips Healthcare). Short axis views covering both ventricles as well as 2-, 3- and 4-chamber views were obtained using a SSFP sequence. Enddiastolic and endsystolic volumes as well as ejection fraction (EF) were derived from short axis segmentation. In addition we measured the circumferential und longitudinal strain applying a post-procession FTI algorithm (TomTec Imaging Systems). Results The study population and the control group showed similar characteristics regarding age and gender (40.3 ± 13.7 yrs. vs. 40.3 ± 15.7 yrs., p > 0.99). In patients with myocarditis the EF was significantly reduced compared to healthy controls (54.3 ± 8.4% vs. 67.8 ± 5.3%, p < 0.001). Furthermore the patients showed significantly lower values for the global circumferential strain (-24.4 ± 4.2% vs. -28.8 ± 3.8%, p < 0.001) as well as for the global longitudinal strain (-17.7 ± 4.5% vs. -23.6 ± 3.0%, p < 0.001). Global circumferential strain (r = -0.77, p < 0.001) and global longitudinal strain (r = -0.65, p < 0.001) correlated well with EF. In the subgroup of myocarditis patients with preserved ejection fraction (EF≥55%, 16 pts.) the global longitudinal strain (-20.4 ± 4.5% vs. -23.7 ± 2.6%, p < 0.05) was significantly reduced compared to the age- and gender matched control subgroup whereas the global circumferential strain did not show a significant difference (-27.3 ± 2.7% vs. -28.9 ± 3.8%, p = n.s.). Conclusions FTI strain analysis offers a fast quantitative assessment of myocardial strain patterns without the need for additional dedicated strain imaging sequences. Myocarditis patients with preserved EF show reduced longitudinal strain whereas the circumferential strain is not significantly

An efficient, free-breathing protocol for MR right heart catheterization

Methods The baseline MR examination begins with cardiac localizers. At this stage it is important to verify isocenter because if the patient is too deep in the bore then femoral vascular access sheaths are inaccessible to the operator. Through-plane phase contrast (PC) scans in the ascending aorta and main pulmonary artery follow for quantification of Qp and Qs. To avoid the need to repeat long PC scans (3 averages), we first perform brief PC ‘localizer’ scans with a single average to confirm the selected velocityencoding factor is correct. For cardiac volumetric analysis, long and short axis views are obtained using a real-time SSFP sequence that sacrifices some spatial resolution for increased temporal resolution. Data is collected over one and a half heartbeats to ensure the entire cardiac cycle is captured. Because of the delay in image reconstruction, the short axis stack is acquired last while the operator prepares for catheterization. A dedicated user interface (Interactive Front End, Siemens; Erlangen, Germany) is used for real-time imaging during catheterization. This interface permits interactive manipulation of imaging planes, slice thickness, saturation pre-pulse, and cine loop recordings. To minimize catheterization time, reference images

Interactive black blood preparation for interventional cardiovascular MRI

Background Recent work demonstrated the feasibility of using realtime MRI to guide right heart cardiac catheterization. In order to make balloon catheters used in the procedure more conspicuous, the balloons were filled with dilute Gd-DTPA, and non-selective saturation pulses were applied along with acquisition of thick slices. The saturation pulses increased the contrast between blood and the Gd-DTPA filled balloons, but suppressed the signal from the background tissue, effectively removing the anatomical context for image-guidance. The goal of this work was to develop an interactive black blood technique, which would preserve the high contrast of the Gd-DTPA balloon and preserve background tissue signal. Methods A flow-sensitive preparation consisting of 90°-180°-90° RF pulses with symmetric gradients around the 180° pulse was implemented in a real-time pulse sequence, so that it could be interactively switched on and off during the scan. The flow-sensitization direction may be placed relative to either physical or slice axes, and was chosen to saturate flowing blood and preserve background signal. During navigation through the vena cava and the right heart chambers, this direction was selected to be in the head-foot direction, and during navigation in the pulmonary vessels it was selected to be in the anteriorposterior and right-left directions. Images were acquired using a real-time single shot SSFP sequence (flip = 45°; TR/TE = 2.8/1.4 ms). Imaging was performed in swine on a 1.5T Siemens Aera scanner. Institutional approval was obtained for all animal experiments. Results A comparison of the non-selective saturation and black blood preparations are shown below, with the balloon in the inferior vena cava (arrow). The corresponding CNR of the balloon (vs blood) and SNR of the anterior myocardium are listed in Table 1. The contrast of the GdDTPA filled balloon is high with both preparations. The myocardial signal is completely nulled with the nonselective saturation pulse, while it is easily visible with the black blood preparation.

Unsupervised free-breathing 3-dimensional imaging of morphology, function and flow in congenital heart disease under 30 minutes: pilot study

Methods Five patients with CHD were included in this pilot study (table 2 in Figure 2). The FB MR studies were performed on a Philips Acheiva 1.5T magnet using a 5-channel phased array coil (see Table 1 in Figure 1) 1. Respiratory synchronized [1], time-resolved MRA 2. Equilibrium phase MRA 3. 3D cine SSFP 4.4D phase contrast (PC) flow imaging 5.3D whole-heart single phase SSFP (coronary) Comparative data was obtained using conventional 2D cine RT SSFP sequences [2] in the VLA, 4 chamber and short axis planes, and 2D PC imaging. Data Analysis: Image quality assessment and quantitative volumetric and flow analysis were performed by three blinded, experienced users. MRA images were graded using a semi-quantitative scale from 1-5 for relevant imaging targets in CHD [1], with 1: excellent, no limitations, and 5: non-diagnostic. The clinical scoring system for 2D and 3D cine SSFP was based on bloodmyocardial contrast, endocardial edge definition and inter-slice alignment [2]. Paired t-test analysis was performed on LV and RV volumes obtained by an experienced observer using the same software

The relationship of myocardial oxygenation to coronary flow and oxygen saturation during CO2 manipulations

Background Oxygenation-sensitive (OS) imaging relies on alterations of deoxyhemoglobin (dHb) in the blood. Thus signal intensity (SI) is dependent on the factors that shift the dHb fraction; oxygen saturation, tissue oxygen extraction and blood supply. We aimed to physically measure and compare these parameters while manipulating myocardial oxygenation with systemic CO2 changes. These changes cause hypercapnic vasodilation and hypocapnic vasoconstriction, which affect the myocardial blood supply and subsequently myocardial oxygenation. Methods In 8 anaesthetized swine, we acquired OS images in 3 short axis slices (mid, mid-apical and apical) using an ECG triggered balanced SSFP sequence with standard cine imaging for function acquired in a short-axis stack in a clinical 3T magnet during normoxia (paO2 =1 00 mmHg). Arterial pCO2 levels of 30, 40 and 50 mmHg were targeted through ventilation settings. Coronary flow was measured using a surgically implanted perivascular MRI-compatible ultrasound flow probe around the left anterior descending (LAD) coronary artery. Blood gases were analyzed from blood drawn through a catheter in the femoral artery and in the coronary sinus, which were obtained simultaneously with LAD flow measurements and OS images. The images were analyzed in systole and assessed for the global myocardial %-change SI in comparison to the baseline values at paCO2 = 40 mmHg.

Assessment of left and right ventricular trabeculation and non-compacted myocardium in a large selected healthy reference population

Background The differentiation of left ventricular non-compaction (LVNC) from physiological trabeculation is still challenging as it may be overdiagnosed by current criteria. Therefore, we sought to investigate the effect of age and gender on both the LV and RV trabeculation in a large group of proven healthy subjects to provide adjusted reference values. Furthermore, we examined the correlation between the amount of non-compacted myocardium and the global ventricular function. Methods We studied a selected reference population of 117 healthy volunteers (58 male, 59 female) stratified into age tertiles (group 1 = 20-34 years, group 2 = 35-50 years, group 3 > 50 years) and by gender. Cardiac diseases were meticulously ruled out by taken medical history, physical examination, electrocardiography, oral glucose tolerance test and lab tests. Cardiovascular magnetic resonance images were acquired in a 1.5T whole-body MRI (Achieva, Philips Heathcare) using a standard SSFP sequence. Enddiastolic (EDV), end-systolic (ESV), stroke and trabeculated volumes as well as ejection fraction (EF) were quantified in short-axis views from base to apex. Volumes were indexed to body surface area (BSA). The noncompacted-to-compacted (NC/C)-ratio was measured in 4-chamber view. Results The left and right ventricular (LV/RV) trabeculated volumes were significantly larger in men than in women and decreased with age (LV: s = -0.1262, R 2 = 0.04450, p 2.3 in 28 of 117 subjects (23.9%) and > 2.5 in 26 of 117 subjects (22.2%), which is regarded as pathologic in current literature. The fraction of subjects with a NC/C ratio > 2.3 differed significantly between age but not between gender groups (p < 0.05, p = n.s). Likewise the mean NC/C ratio showed no significant differences between gender groups (1.9 ± 0.7 vs. 2.1 ± 0.8, p = n.s.) whereas subjects of the first tertile showed significant higher values than the volunteers of the second tertile (2.2 ± 0.8 vs. 1.8 ± 0.6, p < 0.05). An increasing NC/C

Unsupervised free-breathing 3D imaging of morphology, function and flow in congenital heart disease

Methods Five patients with CHD were included in this pilot study. The MR studies were performed on a Philips Acheiva 1.5T magnet using a multielement phased array coil with the following sequences in this order: 1. Free-breathing, respiratory synchronized [1], time-resolved MRA following injection of 0.03 mmol/kg of Gadofosveset, and injection rate 2-4cc/second using a power injector. Duration: < 1 minute 2. Free breathing equilibrium phase MRA, acquired voxel size 0.8 × 0.8 × 1.6 mm, 2 NEX. Duration: 2.5-4 minutes 3. Free breathing 3D cine SSFP with respiratory triggering (TR/TE/flip angle: 3/1.5/60; acquired voxel size: 1.5-1.9 × 1.5-2.1 × 7-8 mm3; SENSE acceleration factor: 1.5-2 × 1.5-2; temporal resolution: 30-45 ms). Duration: 4.5-7 minutes 4. Free breathing sagittal 4D phase contrast (PC) imaging with respiratory navigator (18-26 phases/cardiac cycle, Venc 150 cm/sec, spatial resolution 1.6-2.8 mm3.) Duration: 6-12 minutes 5. Free breathing 3D SSFP with respiratory navigator. (acquired voxel size 1 × 1 × 2 mm3) Duration: 5-7 minutes Comparative data was obtained using conventional 2D cine respiratory triggered SSFP sequences (2) in the VLA, 4 chamber and short axis planes, and 2D PC imaging. Data Analysis: Image quality assessment and quantitative volumetric and flow analysis was performed by a single blinded user. MRA images were graded using a semi-quantitative scale from 1-5 for relevant imaging targets in CHD [1], with 1: excellent, no limitations, and 5: non-diagnostic. The clinical scoring system for 2D and 3D cine SSFP was based on blood-myocardial contrast, endocardial edge definition and inter-slice alignment[2]. Paired t-test analysis was performed on LV and RV volumes.

Inter-observer variability of LV mass and volumes with compressed sensing

Background Recently developed compressed sensing (CS) SSFP sequences significantly reduce data acquisition time thereby reducing patient breath-hold and scan time relative to standard techniques. The variability of ventricular functional (VF) analysis of CS data is not known so this study investigated the inter-observer variation of left ventricular (LV) mass and volume measurements compared to standard SSFP acquisitions.

Fetal Eye Movements on Magnetic Resonance Imaging

ObjectivesEye movements are the physical expression of upper fetal brainstem function. Our aim was to identify and differentiate specific types of fetal eye movement patterns using dynamic MRI sequences. Their occurrence as well as the presence of conjugated eyeball motion and consistently parallel eyeball position was systematically analyzed.MethodsDynamic SSFP sequences were acquired in 72 singleton fetuses (17–40 GW, three age groups [17–23 GW, 24–32 GW, 33–40 GW]). Fetal eye movements were evaluated according to a modified classification originally published by Birnholz (1981): Type 0: no eye movements; Type I: single transient deviations; Type Ia: fast deviation, slower reposition; Type Ib: fast deviation, fast reposition; Type II: single prolonged eye movements; Type III: complex sequences; and Type IV: nystagmoid.ResultsIn 95.8% of fetuses, the evaluation of eye movements was possible using MRI, with a mean acquisition time of 70 seconds. Due to head motion, 4.2% of the fetuses and 20.1% of all dynamic SSFP sequences were excluded.Eye movements were observed in 45 fetuses (65.2%). Significant differences between the age groups were found for Type I (p = 0.03), Type Ia (p = 0.031), and Type IV eye movements (p = 0.033). Consistently parallel bulbs were found in 27.3–45%.ConclusionsIn human fetuses, different eye movement patterns can be identified and described by MRI in utero. In addition to the originally classified eye movement patterns, a novel subtype has been observed, which apparently characterizes an important step in fetal brainstem development. We evaluated, for the first time, eyeball position in fetuses. Ultimately, the assessment of fetal eye movements by MRI yields the potential to identify early signs of brainstem dysfunction, as encountered in brain malformations such as Chiari II or molar tooth malformations.

Whole-Heart Cine MRI in a Single Breath-Hold – A Compressed Sensing Accelerated 3D Acquisition Technique for Assessment of Cardiac Function

The aim of this study was to perform functional MR imaging of the whole heart in a single breath-hold using an undersampled 3 D trajectory for data acquisition in combination with compressed sensing for image reconstruction. Measurements were performed using an SSFP sequence on a 3 T whole-body system equipped with a 32-channel body array coil. A 3 D radial stack-of-stars sampling scheme was utilized enabling efficient undersampling of the k-space and thereby accelerating data acquisition. Compressed sensing was applied for the reconstruction of the missing data. A validation study was performed based on a fully sampled dataset acquired by standard Cartesian cine imaging of 2 D slices on a healthy volunteer. The results were investigated with regard to systematic errors and resolution losses possibly introduced by the developed reconstruction. Subsequently, the proposed technique was applied for in-vivo functional cardiac imaging of the whole heart in a single breath-hold of 27 s. The developed technique was tested on three healthy volunteers to examine its reproducibility. By means of the results of the simulation (temporal resolution: 47 ms, spatial resolution: 1.4 × 1.4 × 8 mm, 3 D image matrix: 208 × 208 × 10), an overall acceleration factor of 10 has been found where the compressed sensing reconstructed image series shows only very low systematic errors and a slight in-plane resolution loss of 15 %. The results of the in-vivo study (temporal resolution: 40.5 ms, spatial resolution: 2.1 × 2.1 × 8 mm, 3 D image matrix: 224 × 224 × 12) performed with an acceleration factor of 10.7 confirm the overall good image quality of the presented technique for undersampled acquisitions. The combination of 3 D radial data acquisition and model-based compressed sensing reconstruction allows high acceleration factors enabling cardiac functional imaging of the whole heart within only one breath-hold. The image quality in the simulated dataset and the in-vivo measurement highlights the great potential of the presented technique for an efficient assessment of cardiac functional parameters.

Detection of Cardiovascular Disease in Elite Athletes Using Cardiac Magnetic Resonance Imaging

Sudden cardiac death [SCD] in competitive athletes is caused by a diverse set of cardiovascular diseases such as hypertrophic and dilated cardiomyopathy [HCM/DCM], myocarditis, coronary anomalies or even coronary artery disease. In order to identify potential risk factors responsible for SCD, elite athletes underwent cardiac magnetic resonance [CMR] imaging. 73 male [M] and 22 female [F] athletes (mean age 35.2 ± 11.4 years) underwent CMR imaging. ECG-gated breath-hold cine SSFP sequences were used for the evaluation of wall motion abnormalities and myocardial hypertrophy as well as for quantitative analysis (left and right ventricular [LV, RV] end-diastolic and end-systolic volume [EDV, ESV], stroke volume [SV], ejection fraction [EF] and myocardial mass [MM]). Furthermore, left and right atrial sizes were assessed by planimetry and delayed enhancement imaging was performed 10 minutes after the application of contrast agent. Coronary arteries were depicted using free-breathing Flash-3 D MR angiography. The quantitative analyses showed eccentric hypertrophy of the left ventricle (remodeling index [MM/LV-EDV]: M 0.75, F 0.665), enlargement of the RV volumes (RV-EDV: M 122.6 ± 19.0 ml/m², F 99.9 ± 7.2 ml/m²) and an increased SV (LV-SV: M 64.7 ± 10.0 ml/m², F 56.5 ± 5.7 ml/m²; RV-SV; M 66.7 ± 10.4 ml/m², F 54.2 ± 7.1 ml/m²). Abnormal findings were detected in 6 athletes (6.3 %) including one benign variant of coronary anomaly and abnormal late gadolinium enhancement in 2 cases. None of the athletes showed wall motion abnormalities or signs of myocardial ischemia. CMR imaging of endurance athletes revealed abnormal findings in more than 5 % of the athletes. However, the prognostic significance remains unclear. Thus, cardiac MRI cannot be recommended as a routine examination in the care of athletes.

Cardiac MRI: Diagnostic Gain of an Additional Axial SSFP Chest Sequence for the Detection of Potentially Significant Extracardiac Findings in the Cardiac MRI Examination Setting

Cardiac MRI (CMRI) is an effective method for imaging of the heart. The aim of our study was to assess whether an axial chest sequence in addition to the standard CMR examination setting has advantages in the detection of potentially significant extracardiac findings (PSEF). 400 consecutive patients were imaged at 1.5 T for clinical reasons. In addition to the standard long and short-axis views, an axial SSFP sequence was obtained covering the thorax from the lung apex to the diaphragm. All sequences were separately evaluated for PSEF. A total of 25 PSEF were diagnosed in 400 patients, including 16 pleural effusions, a pulmonary fibrosis, a spondylodiscitis, ascites, lymphadenopathies, relapse of a mamma carcinoma, growth of adrenal glands metastases and diaphragmatic elevation. All 25 PSEF were detected by reading survey sequences. 24 of the 25 PSEF were detected by the additional SSFP chest sequence as well as the CINE sequences. In our study the additional axial SSFP chest sequence didn't show a benefit in the detection of PSEF. With the survey sequences we were able to detect all PSEF. We conclude that survey images should be assessed for additional findings.

Three-dimensional Magnetic Resonance Imaging Using Single Breath-hold k-t BLAST for Assessment of Global Left Ventricular Functional Parameters

To determine the accuracy of three-dimensional k-t broad-use linear acquisition speed-up technique (k-t BLAST) accelerated magnetic resonance imaging (MRI) for the assessment of left ventricular (LV) parameters compared to segmented multiple breath-hold cine imaging. A multislice cine (steady state free precession [SSFP]) sequence was performed with complete ventricular coverage during multiple breath-holds (temporal resolution 47 ms, voxel size 1.25 × 1.25 × 8 mm(3)). In addition, two k-t BLAST sequences with complete coverage were acquired, KT1 (temporal resolution 57 ms, voxel size 1.25 × 1.25 × 4 mm(3)) and k-t2 (temporal resolution 57 ms, voxel size 1.25 × 1.25 × 8 mm(3)), during a single breath-hold. For comparison of SSFP and k-t BLAST, LV parameters were determined: ejection fraction (EF), end-diastolic volume, end-systolic volume, and LV mass. EF was underestimated by KT1 (47%) and KT2 (48%) compared to the SSFP sequence (53%). All parameters showed high correlation with the k-t BLAST sequences and the SSFP sequence (r = 0.88-0.98, P < .001). The mean relative difference for KT1/KT2 compared to the SSFP sequence was -0.11/-0.09 for the EF, -0.073/-0.086 for the EDV, 0.044/0.051 for the ESV, and 0.085/0.12 for the LV mass. The use of three-dimensional k-t BLAST enabled a determination of the LV parameters with high correlation compared to the SSFP sequence. EF was slightly underestimated, and LV mass was slightly overestimated.

From anatomy to image: the cranial nerves at MRI

In this article, we review the expected course of each of the 12 cranial nerves. Traditional magnetic resonance imaging depicts only the larger cranial nerves but SSFP sequences of magnetic resonance imaging are capable of depicting the cisternal segments of 12 cranial nerves and also provide submillimetric spatial resolution.

1039Time after contrast injection is crucial to determine infarct transmurality and myocardial functional recovery after an acute myocardial infarction

Background: In acute myocardial infarction (MI), contrast hyperenhancement include infarcted myocardium (late enhancement), and area at risk (early enhancement). There is no information about the optimal timing to differentiate these 2 time periods in order to better determine infarct size. Aims: To determine whether the time after contrast injection influences the size of hyperenhancement in acute and chronic MI, and the time that better predicts infarct size and functional recovery.9 Table Table Methods: Subjects were evaluated using CMR the first week (n= 60) and 3 months (n = 47) after an STEMI percutaneously revascularized. Short-axis cine views (SSFP sequences) were performed to quantify volumes, ejection fraction and determine the wall motion score index (WMSI). Inversion-recovery single-shot true fast imaging with steady-state precession (ss-IR) and segmented inversion-recovery gradient-echo (seg-IR) sequences were used. SS-IR was acquired 1, 3, 5, 7, 10, 15, 20, and 25 min after administration of 0.2 mmol/kg Gd-DTPA to analyze dynamic changes. Seg-IR was acquired starting at 10 min after contrast and were used for comparison to ss-IR. Inversion time was properly adjusted to null normal myocardium. All images were blinded, randomized, and measured for hyperenhancement volumes. Results: In acute MI, there was a significant decrease in infarct mass over time (p = 0.005). Hyperenhancement volume was maximum 3 min after contrast injection and stable after 20 min. Nevertheless, infarct mass remained constant over time in chronic MI (p = 0.886). Mean infarct size in acute and chronic MI by seg-IR was 24 ± 16 g and 12 ± 8 g respectively with excellent correlation to ss-IR (r = 0.96 and r = 0.98 p < 0.001). Depending on the imaging time for LGE, the transmurality index also changed, and thus, the number of patient with a transmural infarction (>75%) decreased over time (Table). A transmural infarction (>75%) at 25th min better predicted the absence of improvement in the WMSI, a lower number of segments that recovers function, a higher increase in left ventricular volumes and a lower ejection fraction compared to the transmurality assessed 10th minutes after. (Table). Conclusions: There is a change in infarct mass over time in acute but not in chronic MI, with a maximum volume 3 min after contrast injection. Infarct transmurality 25th min after contrast injection better predicts infarct size and functional recovery at follow-up.

103: Surface-Length Index (SLI): a novel index to predict right ventricle dysfunction by cardiac MRI

Short axis CineMRI has become the gold standard to measure Right Ventricular Ejection Fraction (RVEF). However, it requires a time-consuming manual contouring of the endocardium. Therefore, many examinations do not include complete RV study. We hypothesized that a simple index could be used to detect patients with abnormal RVEF requiring a precise RV study. Two classical RV function indices were tested: 1/ RV fractional area change (FAC) measured in a mid-ventricular short-axis slice and 2/ RV shortening fraction (SF) corresponding to the longitudinal contraction measured in the horizontal long-axis view. They were then combined to obtain the Surface-Length Index: SLI=1- (1-FAC) (1-αSF). This formula was derived from the application of a basal-to-apex gradient in the RV longitudinal contraction into the crescentic shell model published in 1989 by Aebischer. 400 patients underwent a conventional cardiac MRI with a horizontal long-axis view and a stack of contiguous 8 mm short-axis slices at 1.5T with SSFP sequences and were divided in 2 groups: 60 patients retrospectively included to determine α by optimization of the area under ROC curves (Group A) and 340 patients prospectively included to test SLI, FAC and SF capacity to predict a RVEF alteration (<0.5) ( Group B). In group A, the optimal value for α was 1.3. In group B, SLI, FAC and SF area under the ROC curves were respectively 0.94, 0.87 and 0.81. SLI allowed a better detection of RV dysfunction (p<0.001). With a threshold of 0.50, SLI yielded sensitivity and specificity of 85 and 89%. With a threshold of 0.58, SLI yielded sensitivity of 100% and specificity of 51%. Using SLI with a threshold of 0.58 would have saved 38% of the operator's time without inducing any diagnostic error. SLI/EF correlation was good (r 2 =0.64) (cf figure). SLI combines two simple RV measures in end-diastole and end-systole (around 1 minute), and allows significant improvement in post-processing efficiency by pre-selecting RV requiring a complete study. The gain in the operator processing time is close to 1/3. Figure Abstract 103 – Correlation between SLI (vertical) and EF (horiz.)

Feature tracking in cardiac magnetic resonance imaging to evaluate normal myocardial function

Background Assessment of left ventricular function (LV) is one of the most important tasks of clinical cardiac magnetic resonance imaging (CMR). Regional and global LV function has been recognized to differentiate various myocardial disorders. The aim of the study was to provide normal values for myocardial deformation parameters derived from the feature tracking imaging (FTI) algorithm applied to standard CMR cine SSFP sequences in a large group of healthy subjects. The feature tracking algorithm (2D CPA MR©, TomTec Imaging Systems GmbH), is a two dimensional deformation analysis of the myocardium that was originally designed for echocardiographic image analysis, which has now been transferred to CMR SSFP sequences without the need for additional scans. This novel approach may have potential advantages over existing methods, such as broad availability, vendor independency and lack of timeconsuming post processing.