Inversion Recovery Spoiled Gradient Echo Research Articles

Left-Right Intensity Asymmetries Vary Depending on Scanner Model for FLAIR and T1 Weighted MRI Images.

BackgroundLocalized regions of left–right image intensity asymmetry (LRIA) were incidentally observed on T2‐weighted (T2‐w) and T1‐weighted (T1‐w) diagnostic magnetic resonance imaging (MRI) images. Suspicion of herpes encephalitis resulted in unnecessary follow‐up imaging. A nonbiological imaging artifact that can lead to diagnostic uncertainty was identified.PurposeTo investigate whether systematic LRIA exist for a range of scanner models and to determine if LRIA can introduce diagnostic uncertainty.Study TypeA retrospective study using the Alzheimer's Disease Neuroimaging Initiative (ADNI) data base.SubjectsOne thousand seven hundred fifty‐three (median age: 72, males/females: 878/875) unique participants with longitudinal data were included.Field Strength3T.SequencesT1‐w three‐dimensional inversion‐recovery spoiled gradient‐echo (IR‐SPGR) or magnetization‐prepared rapid gradient‐echo (MP‐RAGE) and T2‐w fluid‐attenuated inversion recovery (FLAIR) long tau fast spin echo inversion recovery (LT‐FSE‐IR). Only General Electric, Philips, and Siemens' product sequences were used.AssessmentLRIA was calculated as the left–right percent difference with respect to the mean intensity from automated anatomical atlas segmented regions. Three neuroradiologists with 37 (**), 32 (**), and 3 (**) years of experience rated the clinical impact of 30 T2‐w three‐dimensional FLAIR exams with LRIA to determine the diagnostic uncertainty. Statistical comparisons between retrospective intensity normalized T1m and original T1‐w images were made.Statistical TestsFor each image type, a linear mixed effects model was fit using LRIA scores from all scanners, regions, and participants as the outcome and age and sex as predictors. Statistical significance was defined as having a P‐value <0.05.ResultsLRIA scores were significantly different from zero on most scanners. All clinicians were uncertain or recommended definite diagnostic follow‐up in 62.5% of cases with LRIA >10%. Individuals with acute brain pathology or focal neurologic deficits are not enrolled in ADNI; therefore, focal signal abnormalities were considered false positives.Data ConclusionLRIA is system specific, systematic, creates diagnostic uncertainty, and impacts IR‐SPGR, MP‐RAGE, and LT‐FSE‐IR product sequences.Level of Evidence: 2Technical Efficacy Stage: 3

Thalamic Nuclei Volumes and Their Relationships to Neuroperformance in Multiple Sclerosis: A Cross-Sectional Structural MRI Study.

Although reduced thalamic volume is associated with multiple sclerosis (MS)-related clinical impairment, the role of individual thalamic nuclei remains poorly understood. To test whether individual thalamic nuclei volumes are more strongly associated with clinical disability than the whole thalamic volume. Retrospective analysis of a prospective dataset. A total of 108 MS patients and 48 age- and sex-matched healthy controls (HCs) FIELD STRENGTH: 3T. 3D T1 -weighted inversion recovery spoiled gradient echo; 2D T2 -weighted fluid-attenuated inversion recovery spin echo; 2D dual-echo proton density-weighted/T2 -weighted spin echo. Clinical assessments included the Expanded Disability Status Scale (EDSS), Nine-Hole Peg Test (9HPT), Timed 25-Foot Walk (T25FW), Symbol Digit Modalities Test (SDMT), Brief Visuospatial Memory Test-Revised (BVMTR), and the California Verbal Learning Test (CVLT2). FreeSurfer provided anterior, intralaminar, lateral, medial, ventral, posterior, and total volumes. False discovery rate-corrected partial correlations (controlling for age, sex, and education) to assess the relationships between volumes and neuroperformance. Compared to HCs, MS patients presented with lower thalamic nuclei volumes (P < 0.05) except for the intralaminar nucleus (P = 0.279) and scored worse on all neuroperformance scales (P ≤ 0.05) except for CVLT2 (P = 0.151). All nuclei except intralaminar were associated with EDSS (correlation coefficient range: -0.233 to -0.395), SDMT (range: 0.247-0.423), and 9HPT (range: -0.232 to -0.303) (all P < 0.05). BVMTR was associated with anterior (r = 0.319), lateral (r = 0.31), and medial (r = 0.304) volumes (all P < 0.05). T25FW correlated with ventral (r = -0.392) and total (r = -0.309) volumes (both P < 0.05), with the latter being significantly greater (P < 0.05). Assessing individual nuclei volume can aid in unraveling the relationship between thalamic pathology and disparate aspects of MS-related disability. 2 TECHNICAL EFFICACY STAGE: 2.

Myocardial T1 mapping at 3.0 tesla using an inversion recovery spoiled gradient echo readout and bloch equation simulation with slice profile correction (BLESSPC) T1 estimation algorithm.

To develop an accurate and precise myocardial T1 mapping technique using an inversion recovery spoiled gradient echo readout at 3.0 Tesla (T). The modified Look-Locker inversion-recovery (MOLLI) sequence was modified to use fast low angle shot (FLASH) readout, incorporating a BLESSPC (Bloch Equation Simulation with Slice Profile Correction) T1 estimation algorithm, for accurate myocardial T1 mapping. The FLASH-MOLLI with BLESSPC fitting was compared with different approaches and sequences with regards to T1 estimation accuracy, precision and image artifact based on simulation, phantom studies, and in vivo studies of 10 healthy volunteers and three patients at 3.0 Tesla. The FLASH-MOLLI with BLESSPC fitting yields accurate T1 estimation (average error = -5.4 ± 15.1 ms, percentage error = -0.5% ± 1.2%) for T1 from 236-1852 ms and heart rate from 40-100 bpm in phantom studies. The FLASH-MOLLI sequence prevented off-resonance artifacts in all 10 healthy volunteers at 3.0T. In vivo, there was no significant difference between FLASH-MOLLI-derived myocardial T1 values and "ShMOLLI+IE" derived values (1458.9 ± 20.9 ms versus 1464.1 ± 6.8 ms, P = 0.50); However, the average precision by FLASH-MOLLI was significantly better than that generated by "ShMOLLI+IE" (1.84 ± 0.36% variance versus 3.57 ± 0.94%, P < 0.001). The FLASH-MOLLI with BLESSPC fitting yields accurate and precise T1 estimation, and eliminates banding artifacts associated with bSSFP at 3.0T.

1027T1-mapping measurement with a multi-breathhold delayed enhancement sequence and a single-breathhold cine inversion-recovery spoiled gradient echo sequence: comparison between two techniques

1027T1-mapping measurement with a multi-breathhold delayed enhancement sequence and a single-breathhold cine inversion-recovery spoiled gradient echo sequence: comparison between two techniques

Isolated Noncompaction of Ventricular Myocardium: a Magnetic Resonance Imaging Study of 11 Patients

ObjectiveTo retrospectively summarize the cardiac magnetic resonance imaging (CMRI) findings of isolated noncompaction of ventricular myocardium (INVM).Materials and MethodsEleven patients (M:F = 9:2; mean age, 35 years) were evaluated. Steady-state free precession (SSFP), fast spin echo (SE) sequence, SSFP cine imaging, and delayed enhanced inversion recovery spoiled gradient echo (IR-SPGR) sequence were used for showing abnormal myocardium, measuring ratio of noncompacted/compacted myocardium layers (NC/C ratio), and detecting myocardial viability. The left ventricle was divided into nine segments and a NC/C ratio > 2.3 in diastole was used as cutoff value in diagnosing left INVM. The right ventricle was assessed qualitatively.ResultsCardiac MRI indicated left INVM in seven patients, right INVM in one patient and biventricle INVM in three patients. Characteristic CMRI changes included prominent trabeculations, deep intertrabecular recesses and an increase in the NC/C ratio. The most frequently involved segments was left ventricular apex. Three patients had abnormal high signals within the trabecular structures on SE T2 weighted image. One ventricular aneurysm and one apical thrombus were also observed. Delayed enhancement was seen in six of nine patients with subendocardial and transmural patterns.ConclusionThere are CMRI features that might be characteristic for INVM.

In vivo validation of Cramer-Rao lower bounds for evaluating the reproducibility of Tofts kinetic modeling of DCE-MRI data

Abstract Introduction: Pharmacokinetic modeling (PKM) of dynamic contrast enhanced MRI-data (DCE-MRI) is increasingly used for in vivo monitoring of drug response or in the evaluation of novel antiangiogenic therapies. Several studies have shown a strong correlation between the Tofts kinetic parameter Ktrans and histological tumor grade or a significant reduction in Ktrans after successful therapy. The prognostic value of pre- and posttreatment Ktrans-change, is however strongly dependent on its reproducibility. Up to now, therapy induced microvascular changes are considered to be statistical significant when procentual Ktrans-change exceeds an experimental threshold, determined from paired DCE-MRI examinations. This threshold depends on study design, patient population and tumor type, but is independent of the values of the kinetic parameters, Ktrans and νe, themselves. In previous work we have developed a statistical framework, based on Cramer-Rao lower bounds (CRLB), to determine the standard deviation of Ktrans for a given DCE-MRI protocol. In this study, it is aimed to perform an in vivo validation of the CRLB and to investigate the current method of statistical significance testing. Methods: Three groups of 2 test animals (mice with induced ht29-tumor) were scanned in paired examinations (48 hours in between) with a inversion recovery spoiled gradient echo sequence (Ti = 422-560-680 ms, flip angle = 10-12-15°, Te = 4.12 ms, Tr = Δt = 1-3-5 s) after injection of Gd-DTPA (Dose = 0.1 mM kg−1), for a total of 500 images. Arterial input function was taken as the average concentration curve over both examinations in the femoral artery. Tissue concentration curves in tumor tissue and muscle were fit pixelwise to the Tofts kinetic model without vascular term. In muscle, experimental procentual standard deviation σexp was calculated from spatial variation in Ktrans over the region of interest (ROI) for both examinations. In tumor the coefficient of within patient variation (CWV) between examinations was calculated in both tumor rim and tumor core. For the three protocols, the theoretical standard deviation σth was calculated with the CRLB, evaluated in the mean Ktrans and νe-values of the corresponding ROI. Results: Simulations show that Ktrans-reproducibility is higher in tissue with increasing extravascular extracellullar space (increasing νe). In muscle, the correlation coefficient between σexp and σth is 87%, showing experimental validity of CRLB for a given protocol. In tumor the correlation coefficient between σth and CWV is 76% and 79% in tumor core and tumor rim respectively, indicating that CRLB can explain the major part of the Ktrans-variation between paired scans. Other errors, as improper scan-rescan positioning or natural microvascular changes, can account for the remaining part. Conclusion: When using a fixed threshold for treatment evaluation by means of Ktrans-change, statistical significance will be concluded more often in tissues with small EES-volumes. CRLB have been validated in vivo and can be used in combination with standard statistical test to evaluate statistical significance of Ktrans-change for in vivo monitoring of drug response.

PROMO: Real‐time prospective motion correction in MRI using image‐based tracking

Artifacts caused by patient motion during scanning remain a serious problem in most MRI applications. The prospective motion correction technique attempts to address this problem at its source by keeping the measurement coordinate system fixed with respect to the patient throughout the entire scan process. In this study, a new image-based approach for prospective motion correction is described, which utilizes three orthogonal two-dimensional spiral navigator acquisitions, along with a flexible image-based tracking method based on the extended Kalman filter algorithm for online motion measurement. The spiral navigator/extended Kalman filter framework offers the advantages of image-domain tracking within patient-specific regions-of-interest and reduced sensitivity to off-resonance-induced corruption of rigid-body motion estimates. The performance of the method was tested using offline computer simulations and online in vivo head motion experiments. In vivo validation results covering a broad range of staged head motions indicate a steady-state error of less than 10% of the motion magnitude, even for large compound motions that included rotations over 15 deg. A preliminary in vivo application in three-dimensional inversion recovery spoiled gradient echo (IR-SPGR) and three-dimensional fast spin echo (FSE) sequences demonstrates the effectiveness of the spiral navigator/extended Kalman filter framework for correcting three-dimensional rigid-body head motion artifacts prospectively in high-resolution three-dimensional MRI scans.

Magnetic resonance coronary angiography: Comparison between a Gd-BOPTA- and a Gd-DTPA-enhanced spoiled gradient-echo sequence and a non-contrast-enhanced steady-state free-precession sequence

Several studies have demonstrated that the administration of contrast agents is advantageous in magnetic resonance coronary angiography (MRCA). To compare a non-contrast-enhanced steady-state free-precession (SSFP) with a contrast-enhanced inversion recovery spoiled gradient-echo (IR-GE) sequence using two different contrast agents for MRCA. Eight healthy volunteers were examined on a 1.5T MR scanner. For non-contrast-enhanced MRCA, a breath-hold three-dimensional (3D) SSFP sequence (repetition/echo time [TR/TE] 3.9/1.7 ms, flip angle [FA] 65 degrees) was used. Contrast-enhanced MRCA was performed repetitively in two imaging sessions over 30 min after injection of 0.2 mmol/kg body weight gadobenate dimeglumine (Gd-BOPTA) or gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) using a breath-hold 3D IR-GE sequence (TR/TE 4.1/1.7 ms, FA 15 degrees). The signal-to-noise ratios (SNR) of the coronary arteries, as well as the contrast-to-noise ratios (CNR) between coronary arteries and perivascular tissue, were calculated for all images. Blood T (1) values were repetitively estimated over 30 min using an SSFP sequence with incrementally increasing inversion times (TR/TE 2.4/1.0 ms, FA 50 degrees). Gd-BOPTA-enhanced images showed significantly (P<0.05) higher SNR and CNR compared to Gd-DTPA-enhanced images for all times after contrast injection (SNR: 1 min post injection [PI] 26.4+/-4.2 vs. 16.2+/-3.1; CNR: 1 min PI 21.4+/-3.7 vs. 13.2+/-2.6). Compared to the SSFP images, the Gd-BOPTA-enhanced images showed higher CNR values for all times after injection (1 min PI 21.4+/-3.7 vs. 13.8+/-5.5; P<0.05), whereas the Gd-DTPA-enhanced images did not (1 min PI 13.2+/-2.6 vs. 13.8+/-5.5; P>0.05). Blood T (1) estimates were not significantly different for either agent 1 min after administration (P>0.05), but they were significantly lower for Gd-BOPTA (P<0.05) from 7 to 25 min after injection. Compared to non-contrast-enhanced SSFP images, only Gd-BOPTA-enhanced images show a significantly improved contrast between the coronary arteries and the surrounding tissue.

Detection of Myocardial Fibrosis in Systemic Sclerosis by Contrast-Enhanced Magnetic Resonance Imaging

Our study aimed to assess the prevalence and pattern of late gadolinium enhancement (LGE) as an in vivo correlate of myocardial fibrosis in cardiac asymptomatic patients with systemic sclerosis (SSc). Cardiac magnetic resonance imaging was successfully performed in 34 patients (30 female, 4 male, mean age of 54 +/- 14 years) with proven SSc and in controls with matching age, sex and cardiovascular risk factors. All examinations were performed on a 1.5 T MR system (Avanto, Siemens, Germany). 2D inversion recovery spoiled gradient echo images (TR 8.0 msec, TE 4.0 msec, TI 180 - 240 msec, FA 20 degrees, slice thickness 8 mm, in-plane resolution 1.2 x 1.2 mm (2)) were acquired 10 to 15 min after injection of 0.2 mmol Gd-DTPA per kg body weight to detect myocardial LGE. Poorly defined, patchy as well as well-defined focal areas of LGE were detected predominantly in the mid-myocardial layer of the basal left ventricular segments in 5 of 34 (15 %) SSc patients. A focal area of LGE was observed within the apical septum in one control (3 %, p > 0.05). LGE was observed in a total of 15 segments of the SSc patients and in 1 segment of the controls (p < 0.005). Our results revealed a significantly higher number of LGE positive segments in patients with SSc compared to matched controls, and demonstrate the ability of contrast-enhanced MRI to detect myocardial fibrosis, the hallmark of scleroderma heart disease, in-vivo.

1002 Women with severe ischemic cardiomyopathy have worse survival than men despite similar degree of myocardial scar: a delayed hyper-enhancement MRI study

Methods 349 patients (24% women) with severe ICM >/= 70% stenosis in >/= 1 epicardial vessel on angiography and mean LV ejection fraction (EF) 23%], that underwent DHE-MRI (Siemens 1.5 T scanner, Erlangen, Germany) from 2003– 6 were studied. DHE-MR images were obtained in standard long and short axis orientations (covering the entire LV), after injection of Gadolinium dimenglumine using an inversion recovery spoiled gradient echo sequence: TE 4 msec, TR 8 msec, flip angle 300, bandwidth 140 Hz/ pixel, 23 k-space lines acquired every other RR-interval, field of view (varied from 228–330 in the x-direction and 260–330 in the y-direction) and matrix size (varied from 140–180 in the x-direction and 256 in the y-direction). For DHE-MRI analysis, a custom analysis package (VPT software, Siemens, Erlangen, Germany) was used to manually delineate endocardial and epicardial myocardial edges. Scar was defined (as % of myocardium in a 17-segment model on custom software, Siemens Research) on DHE-MR images, as intensity > 2 standard deviation above viable myocardium. Transmurality score was recorded in all segments as follows: 0 = no scar, 1 = 1– 25% scar, 2 = 26–50%, 3 = 51–75% and 4 = > 75%. Global LV scar burden was calculated as transmurality score for all segments/17. LV volumes, EF, demographic/clinical data, history of cardiac transplantation and all-cause mortality were recorded.

1031 Renal dysfunction, in association with myocardial fibrosis leads to worse survival in patients with severe left ventricular dysfunction: a delayed hyperenhancement MRI study

Methods We studied 176 consecutive patients (61 ± 13 years, 73% men) with severe LV systolic dysfunction (mean ejection fraction (24 ± 8%) who underwent DHE-MRI on 1.5 T MR scanners (Siemens, Erlangen, Germany) from 2005–6. DHE-MR images were obtained in standard long and short axis orientations (covering the entire LV), after injection of Gadolinium dimenglumine using an inversion recovery spoiled gradient echo sequence: TE 4 msec, TR 8 msec, flip angle 30°, bandwidth 140 Hz/pixel, 23 k-space lines acquired every other RR-interval, field of view (varied from 228–330 in the x-direction and 260–330 in the y-direction) and matrix size (varied from 140–180 in the x-direction and 256 in the y-direction). For DHE-MRI analysis, a custom analysis package (VPT software, Siemens, Erlangen, Germany) was used to manually delineate endocardial and epicardial myocardial edges. Scar was defined as having intensity >2 SD above viable myocardium (identified by a user-specified region of interest). Glomerular filtration rate (GFR, ml/min/1.73 m2) was calculated using the following formula: 186 × (serum creatinine-1.154) × (age-0.203) × 1.212 (if black) × 0.742 (if female). We divided patients into 4 groups: 1) GFR > 60, no scar (n = 28) 2) GFR > 60 with scar (n = 85) 3) GFR ≤ 60, no scar (n = 9) and 4) GFR ≤ 60 with scar (n = 53).

1001 Greater degree of left ventricular scar is associated with increased mortality in patients with severe ischemic cardiomyopathy

Methods 349 patients with severe ICM >/= 70% coronary artery disease in >/= 1 epicardial vessel on angiography, mean LV ejection fraction (EF) of 24%] that underwent DHE-MRI (Siemens 1.5 T scanner, Erlangen, Germany) from 2003– 6 were studied. (Siemens, Erlangen, Germany) from 2005–6. DHE-MR images were obtained in standard long and short axis orientations (covering the entire LV), after injection of Gadolinium dimenglumine using an inversion recovery spoiled gradient echo sequence: TE 4 msec, TR 8 msec, flip angle 300, bandwidth 140 Hz/pixel, 23 kspace lines acquired every other RR-interval, field of view (varied from 228–330 in the x-direction and 260–330 in the y-direction) and matrix size (varied from 140–180 in the x-direction and 256 in the y-direction). For DHE-MRI analysis, a custom analysis package (VPT software, Siemens, Erlangen, Germany) was used to manually delineate endocardial and epicardial myocardial edges. Scar was defined (as % of myocardium in a 17-segment model on custom software, Siemens Research) on DHE-MR images, as intensity > 2 standard deviation above viable myocardium. Transmurality score was recorded in all segments as follows: 0 = no scar, 1 = 1–25% scar, 2 = 26–50%, 3 = 51– 75% and 4 = > 75%. Total scar score was calculated as transmurality score for all segments/17. LV volumes, EF, demographics, risk factors, need for cardiac transplantation (CTx) and all-cause mortality were recorded. Figure 1.