Classification of solutions for guided waves in fluid-loaded viscoelastic composites with large numbers of layers.

Guided ultrasonic waves are used for the inspection of multilayered composite aerospace structures. Calculating the corresponding dispersion diagrams is challenging for thick-walled composites with more than 100 layers, such as in modern rocket booster pressure vessels. The Dispersion Calculator (DC) is an open source software for calculating such dispersion diagrams and mode shapes of guided waves. Attenuation caused by viscoelasticity and fluid-loading makes the dispersion curve tracing much more difficult than in the nonattenuated case because the modal solutions are sought in the complex wavenumber plane. The tracing problem is mastered by a reliable algorithm. Whereas leaky Lamb and Scholte waves in coupled and decoupled cases are modeled using the stiffness matrix method, shear horizontal (SH) waves are traced using the transfer matrix method without facing the numerical instability. Through implementation of mode family specific dispersion equations in both matrix techniques for nonattenuated and attenuated cases, symmetric, antisymmetric, and nonsymmetric leaky Lamb, Scholte, and SH waves can be traced separately with better efficiency and robustness. The capabilities of DC are demonstrated by calculating dispersion diagrams and mode shapes for a viscoelastic composite with 400 layers immersed in water. Results are compared against DISPERSE (Imperial College London, London, UK) for selected cases.

Classification of solutions for guided waves in anisotropic composites with large numbers of layers.

Guided waves are used for the non-destructive evaluation in automotive and aerospace industries. There is a trend leaning away from isotropic materials to the manufacturing based on composites. However, the elastic wave dynamics in such materials is considerably more complicated. Much effort has been committed to the calculation of guided waves' dispersion curves in composites. Lots of methods and tools are available, but it becomes difficult when there are more than one hundred layers. In this paper the calculation of dispersion diagrams and mode shapes using the stiffness matrix method is demonstrated. Boundary conditions are implemented into the stiffness matrix method that allow for the separate tracing of the various mode families. Shear horizontal modes are modeled with the transfer matrix method without facing any numerical instability. It is elucidated just how the occurrence of the mode families depends on the system's symmetry and wave propagation direction. As a result, the robustness and reliability of guided wave modeling by using the stiffness method is improved, and more information about the modes is yielded. This is demonstrated on exemplary layups of the fiber reinforced polymer T800/913, with up to 400 layers. Referencing is made against results from DISPERSE® (Imperial College London, London, UK) for selected cases.

Cardiac MOLLI T1 mapping at 3.0 T: comparison of patient-adaptive dual-source RF and conventional RF transmission.

To prospectively compare image quality and myocardial T1 relaxation times of modified Look-Locker inversion recovery (MOLLI) imaging at 3.0 T (T) acquired with patient-adaptive dual-source (DS) and conventional single-source (SS) radiofrequency (RF) transmission. Pre- and post-contrast MOLLI T1 mapping using SS and DS was acquired in 27 patients. Patient wise and segment wise analysis of T1 times was performed. The correlation of DS MOLLI measurements with a reference spin echo sequence was analysed in phantom experiments. DS MOLLI imaging reduced T1 standard deviation in 14 out of 16 myocardial segments (87.5%). Significant reduction of T1 variance could be obtained in 7 segments (43.8%). DS significantly reduced myocardial T1 variance in 16 out of 25 patients (64.0%). With conventional RF transmission, dielectric shading artefacts occurred in six patients causing diagnostic uncertainty. No according artefacts were found on DS images. DS image findings were in accordance with conventional T1 mapping and late gadolinium enhancement (LGE) imaging. Phantom experiments demonstrated good correlation of myocardial T1 time between DS MOLLI and spin echo imaging. Dual-source RF transmission enhances myocardial T1 homogeneity in MOLLI imaging at 3.0 T. The reduction of signal inhomogeneities and artefacts due to dielectric shading is likely to enhance diagnostic confidence.

3D non-contrast-enhanced ECG-gated MR angiography of the lower extremities with dual-source radiofrequency transmission at 3.0 T: Intraindividual comparison with contrast-enhanced MR angiography in PAOD patients.

OBJECTIVE: To compare prospectively image quality and diagnostic confidence of flow-sensitive 3D turbo spin echo (TSE)-based non-contrast-enhanced MR angiography (NE-MRA) at 3.0 T using dual-source radiofrequency (RF) transmission with contrast-enhanced MRA (CE-MRA) in patients with peripheral arterial occlusive disease (PAOD). METHODS: After consent was obtained, 35 patients (mean age 69.1 ± 10.6 years) with PAOD stage II-IV underwent NE-MRA followed by CE-MRA. Signal-to-noise ratio and contrast-to-noise ratio were calculated. Subjective image quality was independently assessed by two radiologists and stenosis scoring was performed in 875 arterial segments. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for stenosis classification were calculated using CE-MRA as a reference method. Diagnostic agreement with CE-MRA was evaluated with Cohen's kappa statistics. RESULTS: NE-MRA provided high objective and subjective image quality at all levels of the arterial tree. Sensitivity and specificity for the detection of relevant stenosis was 91 % and 89 %, respectively; the NPV was 96 % and the PPV 78 %. There was good concordance between CE-MRA and NE-MRA in stenosis scoring. CONCLUSIONS: 3D electrocardiography (ECG)-gated TSE NE-MRA with patient-adaptive dual-source RF transmission at 3.0 T is a promising alternative for PAOD patients with contraindications for gadolinium-based contrast agents. It offers high sensitivity and NPV values in the detection of clinically relevant arterial stenosis. KEY POINTS: • Flow-sensitive TSE NE-MRA is a promising technique for PAOD evaluation. • Diagnostic accuracy is comparable to contrast-enhanced MRA. • NE-MRA eliminates the risk of NSF in patients with renal insufficiency. • Costs arising from the use of contrast agents can be avoided.

Single-dose gadobutrol in comparison with single-dose gadobenate dimeglumine for magnetic resonance imaging of chronic myocardial infarction at 3 T.

OBJECTIVES: The aim of this study was to compare the contrast-to-noise ratio (CNR) values of infarct and remote myocardium as well as infarct and blood after application of 0.1 mmol/kg gadobutrol and 0.1 mmol/kg gadobenate dimeglumine on late gadolinium enhancement magnetic resonance (MR) images. MATERIAL AND METHODS: The study was a prospective randomized controlled clinical study. After informed consent was obtained, 20 patients (12 men, 8 women; mean age, 67 ± 11 years) with known chronic myocardial infarction were included for an intraindividual comparison of a single-dose gadobutrol and a single-dose gadobenate dimeglumine. Two MR imaging examinations were performed within a period of 28 days in a crossover design. Late gadolinium enhancement imaging was performed 10 minutes after gadolinium administration using a 2-dimensional phase-sensitive inversion recovery gradient echo sequence at 3 T. Infarct size, signal intensities (SIs), signal-to-noise ratio, and CNR were determined on phase-sensitive MR images. Values for CNR were calculated as CNRinfarct/myocardium = (SIinfarct - SImyocardium)/SDnoise and CNRinfarct/blood = (SIinfarct - SIblood)/SDnoise. In addition, the areas of myocardial infarction were determined on single slices. The entire infarct volumes were calculated by adding the areas with hyperenhancement multiplied by the slice thickness. RESULTS: Late gadolinium enhancement was present in all patients. Median values of the infarct area, infarct volume, and transmurality for gadobutrol and gadobenate dimeglumine showed good to excellent concordance (rc = 0.85, rc = 0.95, and rc = 0.71, respectively). The mean signal-to-noise ratio values for infarct, remote myocardium, and ventricular blood were 18.6 ± 6.5, 4.1 ± 3.7, and 14.6 ± 7.5, respectively, for gadobutrol and 18.8 ± 8.9, 4.9 ± 4.5, and 17.8 ± 10.1, respectively, for gadobenate dimeglumine (P = 0.93, P = 0.48, and P = 0.149, respectively). The mean values of CNRinfarct/myocardium and CNRinfarct/blood were 14.5 ± 5.9 and 4.0 ± 4.6, respectively, for gadobutrol and 13.9 ± 6.1 and 0.9 ± 4.5, respectively, for gadobenate dimeglumine (P = 0.69 and P = 0.02, respectively). CONCLUSION: Both gadobutrol and gadobenate dimeglumine allow for successful late gadolinium enhancement imaging of chronic myocardial infarction after a single-dose application (0.1 mmol/kg) at 3 T. Gadobutrol provides a higher CNR between infarct and blood. The CNRs between infarct and normal myocardium, infarct size, and transmural extent were similar for both contrast agents.

Assessment of myocardial infarction and postinfarction scar remodeling with an elastin-specific magnetic resonance agent.

BACKGROUND: To prospectively evaluate an elastin-specific MR contrast agent (ESMA) for in vivo targeting of elastic fibers in myocardial infarction (MI) and postinfarction scar remodeling. METHODS AND RESULTS: MI was induced in C57BL/6J mice (n=40) by permanent ligation of the left anterior descending coronary artery. MRI was performed at 7 and 21 days after MI. The merits of gadolinium-based ESMA (Gd-ESMA) were compared with gadopentetic acid (Gd-DTPA) for infarct size determination, contrast-to-noise ratio (CNR), and enhancement kinetics. Specific binding in vivo was evaluated by blocking the molecular target using nonparamagnetic lanthanum-ESMA. In vivo imaging results were confirmed by postmortem triphenyltetrazolium chloride staining, elastica van Gieson staining, and Western blotting. Delayed enhancement MRI revealed prolonged enhancement of Gd-ESMA in the postischemic scar compared with Gd-DTPA. Infarct size measurements showed good agreement between Gd-ESMA and Gd-DTPA and were confirmed by ex vivo triphenyltetrazolium chloride staining. Preinjection of the blocking lanthanum-ESMA resulted in significantly lower CNR of Gd-ESMA at the infarct site (P=0.0019). Although no significant differences in CNR were observed between delayed enhancement imaging and Gd-DTPA between days 7 and 21 (1.8± versus 3.8; P=ns), Gd-ESMA showed markedly higher CNR on day 21 after MI (14.1 versus 4.9; P=0.0032), which correlated with increased synthesis of tropoelastin detected by Western blot analysis and histology. Higher CNR values for Gd-ESMA further correlated with improved ejection fraction of the mice on day 21 after MI. CONCLUSIONS: Gd-ESMA enables targeting of elastin within the infarct scar in a mouse model of MI. The imaging properties of Gd-ESMA allow quantification of intrascar elastin content in vivo and thereby provide potential for noninvasive characterization of postinfarction scar remodeling.

Myocardium: dynamic versus single-shot CT perfusion imaging.

PURPOSE: To determine the diagnostic accuracy of dynamic computed tomographic (CT) perfusion imaging of the myocardium for the detection of hemodynamically relevant coronary artery stenosis compared with the accuracy of coronary angiography and fractional flow reserve (FFR) measurement. MATERIALS AND METHODS: This study was approved by the institutional review board and the Federal Radiation Safety Council (Bundesamt für Strahlenschutz). All patients provided written informed consent. Thirty-two consecutive patients in adenosine stress conditions underwent dynamic CT perfusion imaging (14 consecutive data sets) performed by using a 256-section scanner with an 8-cm detector and without table movement. Time to peak, area under the curve, upslope, and peak enhancement were determined after calculation of time-attenuation curves. In addition, myocardial blood flow (MBF) was determined quantitatively. Results were compared with those of coronary angiography and FFR measurement by using a receiver operating characteristic (ROC) analysis. In addition, threshold values based on the Youden index and sensitivity and specificity were calculated. RESULTS: Area under the ROC curve, sensitivity, and specificity, respectively, were 0.67, 41.4% (95% confidence interval [CI]: 23.5%, 61.1%), and 86.6% (95% CI: 76.0%, 93.7%) for time to peak; 0.74, 58.6% (95% CI: 38.9%, 76.5%), and 83.6% (95% CI: 72.5%, 91.5%) for area under the curve; 0.87, 82.8% (95% CI: 64.2%, 94.1%), and 88.1% (95% CI: 77.8%, 94.7%) for upslope; 0.83, 82.8% (95% CI: 64.2%, 94.1%), and 89.6% (95% CI: 79.6%, 95.7%) for peak enhancement; and 0.86, 75.9% (95% CI: 56.5%, 89.7%), and 100% (95% CI: 94.6%, 100%) for MBF. The thresholds determined by using the Youden index were 148.5 HU · sec for area under the curve, 12 seconds for time to peak, 2.5 HU/sec for upslope, 34 HU for peak enhancement, and 1.64 mL/g/min for MBF. CONCLUSION: The semiquantitative parameters upslope and peak enhancement and the quantitative parameter MBF showed similar high diagnostic accuracy. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13121441/-/DC1.

Evaluation of phase-sensitive versus magnitude reconstructed inversion recovery imaging for the assessment of myocardial infarction in mice with a clinical magnetic resonance scanner.

PURPOSE: To evaluate phase-sensitive inversion-recovery (PSIR) imaging at 1.5 T in a mouse model of permanent coronary artery ligation as a potentially rapid and robust alternative for the accurate assessment of myocardial infarction (MI) by cardiac magnetic resonance imaging (MRI). MATERIALS AND METHODS: PSIR late gadolinium enhancement (LGE) imaging was compared to conventional 2D segmented inversion-recovery imaging for the assessment of murine MI. RESULTS: PSIR images provided comparable contrast and kinetics of intravenously injected gadopentetate dimeglumine (Gd-DTPA). At the mid-ventricular level there was good agreement between conventional IR and PSIR for infarct size assessment. After intravenous injection a limited time window of ∼6 minutes is available for delayed enhancement imaging in mice. Whole-heart infarct imaging with 1 mm thick slices was only possible in this restricted time frame when the PSIR method is applied, avoiding the need for repetitively adapting the correct inversion time. Infarct size determined by PSIR MRI demonstrated good agreement with postmortem histology. Infarct size determined by PSIR LGE MRI inversely correlates with left-ventricular function on day 7 after MI. CONCLUSION: The PSIR technique provides stable and consistent contrast between hyperenhanced and remote myocardium independent of the selected inversion time (TI) and proved to be a robust, fast, and accurate tool for the assessment of MI in mice.

Preclinical evaluation of a new self-expanding device for closure of muscular ventricular septal defects in a pig model.

OBJECTIVES: Aim of our study was the preclinical evaluation of a new self expanding device for interventional closure of muscular ventricular septal defects (mVSDs) in an acute pig model. BACKGROUND: Devices currently in use for closure of mVSDs still have their limitations. The deployment of the disks is dependent from the expansion of the stent, which can be associated with problems for sufficient closure of the mVSDs. This was the reason for developing a modified device with only one disk MATERIALS AND METHODS: The device was constructed in a single wire technique with a unique configured retention disk. mVSDs were created in six pigs with a specially designed punch instrument, and subsequently closed with our new device during the same session using a jugular or femoral vein approach. Potential residual shunting volumes were estimated by echocardiography and hemodynamic measurements. After closure, animals were sacrificed, and hearts were harvested for macropathologic evaluation. In two animals, MRI was performed for additional noninvasive evaluation. RESULTS: Devices were successfully implanted in all animals with good alignment of the disk to the left ventricular septum, even if the stent was oversized. Echocardiography, hemodynamics, angiography and macropathology revealed complete closure of all mVSDs. MRI and echocardiography showed a good visibility of the device. CONCLUSIONS: Our preclinical study shows successful closure of iatrogenic created mVSDs without residual shunting. The device is characterized by a more controlled deployment, an independent deployment of disk and waist, and a good alignment of the left ventricular disk to the muscular septum.

Off-pump extraanatomic bypass from the ascending to the descending aorta for re-operation of interrupted aortic arch in an adolescent.

The appearance of re-stenosis after repair of an interrupted aortic arch may be a surgical challenge due to adhesions. Here, we describe an approach using off-pump coronary artery bypass grafting techniques to reach the descending aorta through a median sternotomy in a patient with aortic arch stenosis after conduit repair. The 17-year-old patient with diagnoses of interrupted aortic arch and ventricular septal defect presented after two previous operations (one left lateral thoracotomy and one median sternotomy) with a stenosed vascular graft between ascending and descending aorta. Surgery was done via re-sternotomy without cardio-pulmonary bypass. An extraanatomic graft was used to connect ascending and descending aorta. When performing the distal anastomosis, the heart was exposed using a standard suction device. This case demonstrates that the use of modern techniques may facilitate surgical approaches dramatically. In our opinion the above-described technique is the first choice for all patients requiring arch repair following multiple previous operations, performed via sternotomy and thoracotomy.

Assessment of Myocardial Viability with 3D MRI at 3 T.

OBJECTIVE: The aim of our study was to show that spatial resolution can be improved without loss of diagnostic accuracy if a 3D inversion recovery gradient-recalled echo (GRE) sequence is used instead of a segmented inversion recovery GRE at 3 T for the assessment of myocardial infarction. SUBJECTS AND METHODS: Fifteen patients with myocardial infarction were examined on a 3-T MR system. A segmented breath-hold 3D inversion recovery GRE technique with a voxel size of 6.3 mm(3) was compared with a breath-hold standard 2D inversion recovery GRE technique with a voxel size of 21.3 mm(3) for the detection of delayed enhancement. Contrast-to-noise ratios (CNRs) were calculated and infarct volumes were measured. Detection and transmural extent of infarctions were evaluated using kappa statistics. Total acquisition times were measured for both sequences. RESULTS: The CNR in the 3D technique did not show any significant difference compared with the 2D technique. The correlation coefficients of the infarct volumes determined with the 3D and 2D inversion recovery GRE studies at 3 T were r = 0.99 (p < 0.001). The assessment of the presence of hyperenhanced myocardium in all segments and the evaluation of transmurality resulted in very good agreement (kappa = 0.98 and kappa = 0.90). Total acquisition time was significantly shorter with the 3D technique (2.4 +/- 0.9 minutes) than with the 2D technique (4.9 +/- 1.5 minutes) (p < 0.001). CONCLUSION: The use of a 3D inversion recovery GRE sequence at 3 T allows accurate assessment of myocardial infarction without loss of CNR compared with the standard 2D technique. Furthermore, data acquisition time can be significantly reduced.

Low dose gadobenate dimeglumine for imaging of chronic myocardial infarction in comparison with standard dose gadopentetate dimeglumine.

OBJECTIVES: Gadobenate dimeglumine has a 2-fold higher T1 relaxivity compared with gadopentetate dimeglumine and can be used for imaging delayed enhancement in the assessment of myocardial infarction. The purpose of this study was to compare 0.1 mmoL/kg gadobenate dimeglumine (Gd-BOPTA, MultiHance, Bracco Imaging SpA, Milan, Italy) with 0.2 mmoL/kg gadopentetate dimeglumine (Gd-DTPA, Magnevist, Bayer-Schering Pharma AG, Berlin, Germany) in cardiac magnetic resonance imaging. MATERIALS AND METHODS: The study was performed in accordance with the institutional review board. Two groups of 20 patients underwent magnetic resonance examinations for evaluation of chronic myocardial infarction. Although group 1 received gadobenate dimeglumine at a dose of 0.1 mmoL/kg, group 2 received gadopentetate dimeglumine at a dose of 0.2 mmoL/kg. Single shot inversion recovery (IR) steady-state free precession (SSFP), and IR gradient echo sequence (GRE) sequences were used for imaging delayed enhancement. The sizes of myocardial infarctions were measured for both contrast agents in both imaging techniques by 2 readers. Bland-Altman analyses were performed for each sequence and gadolinium chelate. Furthermore, the transmural extent of myocardial infarction was assessed by 2 readers according to the 17-segment model for both contrast media and both sequences and kappa values were calculated. Signal-to-noise ratios for infarcted myocardium, normal myocardium, and the left ventricular cavity were measured, and the contrast-to-noise ratios of infarcted compared with normal myocardium (CNRinf-myo) and infarcted myocardium in relation to the left ventricular cavities (CNRinf-LVC) were calculated. RESULTS: The Bland-Altman plots in the assessment of infarction size did not reveal a systematic bias between the 2 readers. The mean difference between reader 1 and 2 was less than 0.9 cm3 of mean infarction volume. Assessment of interobserver agreement regarding the transmural extent of myocardial infarction resulted in kappa values of kappa = 0.845 (IR SSFP) and kappa = 0.874 (IR GRE) in gadobenate-enhanced images and kappa = 0.841 (IR SSFP) and kappa = 0.833 (IR GRE) after administration of gadopentetate. CNRinf-normal was significantly higher on the images of group 1 (gadobenate) compared with group 2 (gadopentetate) in both sequences (single shot IR SSFP: 18.1 +/- 10.1 vs. 12.1 +/- 6.7; P = 0.032 and IR GRE: 27.2 +/- 5.8 vs. 19.7 +/- 5.9; P = 0.005). The mean value of CNRinf-LVC for the group examined with Gd-BOPTA was lower, though not significantly, compared with the group examined with Gd-DTPA in IR GRE technique, whereas CNRinf-LVC for IR SSFP resulted in equal values (single shot IR SSFP: 1.2 +/- 5.2 vs. 1.1 +/- 6.8; P = n.s. and IR GRE 2.4 +/- 5.8 vs. 5.8 +/- 7.9; P = n.s.). CONCLUSIONS: Low dose Gd-BOPTA resulted in significantly higher CNRinf-myo compared with standard dose Gd-DTPA in imaging of myocardial infarction with IR SSFP and IR GRE sequences. Demarcation of infarcted myocardium from the left ventricular cavity assessed by CNR showed no significant difference after application of either contrast media in both imaging techniques.

Accuracy of accelerated cine MR imaging at 3 Tesla in longitudinal follow-up of cardiac function.

The ability of fast, parallel-imaging-based cine magnetic resonance (MR) to monitor global cardiac function in longitudinal exams at 3 Tesla was evaluated. Seventeen patients with chronic cardiac disease underwent serial cine MR imaging exams (n=3) at 3 Tesla. Data were acquired in short-axis orientation using cine steady-state free precession (SSFP) with a spatial resolution of 2.5 x 1.9 mm(2) at 45 ms temporal resolution. Multislice imaging (three slices/breath-hold) was performed using TSENSE acceleration (R=3) and standard single-slice cine (non-TSENSE) was performed at identical locations in consecutive breath-holds. End-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF) and myocardial mass (MM) of both cine approaches were compared for individual time-points as well as for longitudinal comparison. TSENSE-cine did not show significant differences for EDV (2.6 ml; P=0.79), ESV (2.2 ml; P=0.81), EF (-0.3%; P=0.95) and MM (2.4 g; P=0.72) in comparison with non-TSENSE. Longitudinal ANOVA analysis did not reveal significant differences for any parameter, neither for non-TSENSE data (all P>0.7) nor for TSENSE data (all P>0.9). Multifactorial ANOVA showed non-significant differences (all P>0.7) at comparable data variances. Data acquisition was significantly shortened using TSENSE. Threefold accelerated multislice cine at 3 Tesla allows accurate assessment of volumetric LV data and accurate longitudinal monitoring of global LV function at a substantially shorter overall examination time.

Phase-sensitive inversion-recovery MR imaging in the detection of myocardial infarction.

PURPOSE: To prospectively determine if phase-sensitive inversion-recovery (IR) magnetic resonance (MR) imaging eliminates the need to find the precise inversion time (TI) to null the signal of normal myocardium to achieve high contrast between infarcted and normal myocardium. MATERIALS AND METHODS: Informed consent was obtained from each patient for this prospective MR imaging research study, which was approved by the institutional review board. Twenty patients (16 men; four women; mean age, 56 years +/- 12.3) who experienced Q-wave myocardial infarction 2 weeks earlier were examined with a 1.5-T MR system 10 minutes after administration of 0.1 mmol per kilogram of body weight gadobenate dimeglumine. To determine the optimal TI, a TI scout sequence was used. A segmented two-dimensional IR turbo fast low-angle shot (FLASH) sequence and a segmented two-dimensional IR true fast imaging with steady-state precession (FISP) sequence that produces both phase-sensitive and magnitude-reconstructed images were used at TI values of 200-600 msec (TI values were varied in 100-msec steps) and at optimal TI (mean value, 330 msec). Contrast-to-noise ratios (CNRs) of normal and infarcted myocardium and the area of infarcted myocardium were determined. Magnitude-reconstructed IR turbo FLASH images were compared with magnitude-reconstructed and phase-sensitive IR true FISP images. Two-tailed unpaired sample Student t test was used to compare CNRs, and two-tailed paired-sample Student t test was used to compare area of infarction. RESULTS: Mean CNR of images acquired with IR turbo FLASH and IR true FISP (phase-sensitive and magnitude-reconstructed images) at optimal TI (mean value, 330 msec) were 6.6, 6.2, and 6.1, respectively. For a TI of 200 msec, CNR values were -4.3, -4.0, and 7.2, respectively; for TI of 600 msec, CNR values were 3.1, 3.3, and 4.3, respectively. Area of infarcted myocardium was underestimated on magnitude-reconstruction images (P = .002-.03) for short TI values (ie, 200 msec) for both sequences and for a TI of 300 msec for IR true FISP but not on phase-sensitive reconstructed IR true FISP images when compared with IR turbo FLASH images obtained at optimal TI. CONCLUSION: Phase-sensitive image reconstruction results in reduced need for precise choice of TI and more consistent image quality.