T1-weighted Gradient-echo Sequence Research Articles

T2-weighted spoiled gradient echo sequence (MERGE): A different perspective on the forensic age estimation

Introduction Age estimation methods using MRI are dependent on staging systems used in T1, T2 and fast spin-echo proton density-weighted sequences. The staging system created by Dedouit [1] from images obtained by fast spin-echo proton density-weighted MRI sequences depends on the assessment of horizontal cartilage hyperintensity. Images obtained by this method, detecting 1.5 mm hyperintensity thickness, and in some cases, detecting continuity of hyperintensity could be challenging. The purpose of this preliminary study was to investigate the utility of T2-weighted spoiled gradient echo sequence in determining the degree of ossification of epiphyses. Material and methods In this study, fast spin-echo proton density-weighted and MERGE T2-weighted spoiled gradient echo sequences of the knee of 25 patients (10–30 years, 10 female and 15 male) were evaluated using Dedouit et al.’s [1] five-stage method. Results The horizontal cartilages assessed with MERGE exhibited hyperintensity and clearly visible borders ( Fig. 1 ). Stage 2 and 3 were easily distinguishable and the epiphyseal scar line observed in stage 5 (complete fusion) was easily observed in contrast to the fast spin-echo proton density-weighted sequence. The hyperintense line that was assessed in fast spin-echo proton density-weighted sequence in stage 3 cases was seen as continuous and intermittent hypointense line in MERGE sequence. It was suggested that substages may be necessary for the distinction of stage 3 and 4. Discussion At present, due to the ethical concerns, non-ionized methods (ultrasound and MRI) are more frequently used in living individuals’ age estimations. MRI assessments in spoiled T2-weighted spoiled gradient echo sequence for age determination may be advantageous in the examination of epiphyseal lines and may produce different options in staging.

Temporary Hearing Threshold Shift in Healthy Volunteers with Hearing Protection Caused by Acoustic Noise Exposure during 3-T Multisequence MR Neuroimaging.

Purpose To determine whether a single 51-minute exposure to acoustic noise during 3-T multisequence magnetic resonance (MR) neuroimaging could affect the hearing threshold of healthy adults with earplugs and sponge mats as hearing protection. Materials and Methods With earplugs and motion-refraining sponge mats as hearing protection, 26 healthy young adults underwent 3-T MR neuroimaging imaging that included T1-weighted three-dimensional gradient-echo sequence, T2-weighted fast spin-echo sequence, diffusion-tensor imaging, diffusion-kurtosis imaging, T2*-weighted three-dimensional multiecho gradient-echo sequence, and blood oxygen level-dependent imaging. Automated auditory brainstem response (ABR) was used to measure the hearing thresholds within 24 hours before, within 20 minutes after, and 25 days after the MR examination. One-way repeated-measure analysis of variance with Bonferroni adjustment was used to compare automated ABR results among the three tests and partial η2 (ηp2) was reported as a measure of effect size. Results Automated ABR results showed significantly increased mean threshold shift of 5.0 dB ± 8.1 (standard deviation) (left ear: 4.8 dB ± 9.2 [95% confidence interval: 1.09, 8.53], ηp2 = 0.221, P = .013; right ear: 5.2 dB ± 6.9 [95% confidence interval: 2.36, 8.02], ηp2 = 0.364, P = .001) immediately after the MR examination compared with the baseline study. This shift is below the temporary threshold shift of 40-50 dB that is associated with cochlea nerve changes. Automated ABR obtained at day 25 after MR imaging showed no significant differences from baseline (left ear: -2.3 dB ± 8.6 [95% confidence interval: -5.79, 1.78], ηp2 = 0.069, P = .185; right ear: 0.4 dB ± 7.3 [95% confidence interval: -3.35, 2.58], ηp2 = 0.003, P = .791). Conclusion A 3-T MR neuroimaging examination with the acoustic noise at equivalent sound pressure level of 103.5-111.3 dBA lasting 51 minutes can cause temporary hearing threshold shift in healthy volunteers with hearing protection. © RSNA, 2017.

Reduced Pineal Volume in Alzheimer Disease: A Retrospective Cross-sectional MR Imaging Study.

Purpose To evaluate pineal volume in patients with Alzheimer disease (AD), patients with mild cognitive impairment (MCI), and healthy control subjects and to correlate the findings with results of cognitive testing and brain parenchymal volumes. Materials and Methods The ethics committee approved this retrospective study. The participants included 63 patients with AD, 33 patients with MCI, and 24 healthy control subjects. There were 36 men and 84 women, with a mean age (±standard deviation) of 76.7 years ± 7.6. The pineal gland volume and pineal parenchymal volume were measured by using three-dimensional volumetric magnetic resonance imaging (T1-weighted magnetization-prepared rapid gradient-echo sequence; spatial resolution, 0.9 × 0.98 × 0.98 mm). With age and total intracranial volume as covariates, analysis of covariance with the Bonferroni post hoc test was performed to compare the pineal volume among the AD, MCI, and control groups. Multiple regression analyses were used to identify predictor variables associated with pineal volume. Results The mean pineal gland volume in patients with AD (72.3 mm3 ± 5.4; 95% confidence interval [CI]: 61.5 mm3, 83.1 mm3) was significantly smaller than that in control subjects (102.1 mm3 ± 9.0; 95% CI: 84.4 mm3, 119.9 mm3) (P = .019). The mean pineal parenchymal volume in patients with AD (63.8 mm3 ± 4.2; 95% CI: 55.4 mm3, 72.1 mm3) was significantly smaller than that in patients with MCI (81.7 mm3 ± 5.8; 95% CI: 70.3 mm3, 93.1 mm3; P = .044) and control subjects (89.1 mm3 ± 6.9; 95% CI: 75.4 mm3, 102.9 mm3; P = .009). Multiple regression analyses demonstrated that the Mini-Mental State Examination score and total intracranial volume were significant independent predictors of both pineal gland volume and pineal parenchymal volume (P < .001). Conclusion Pineal volume reduction showed correlation with cognitive decline and thus might be useful to predict cognitive decline in patients with AD. © RSNA, 2017.

Differentiation of vestibular schwannomas from meningiomas of the internal auditory canal using perilymphatic signal evaluation on T2-weighted gradient-echo fast imaging employing steady state acquisition at 3T

BackgroundOur aim was to confirm the usefulness of the perilymphatic signal changes on T2-weighted (T2W) gradient-echo sequence to differentiate vestibular schwannomas from internal auditory canal (IAC) meningiomas, through a compartmental analysis of inner ear fluids signal intensity.MethodsA total of 203 patients with all criteria for typical vestibular schwannoma on T1-weighted contrast-enhanced sequences were retrospectively enrolled (190 schwannomas and 13 meningiomas). All patients underwent a T2W gradient-echo steady state free precession (SSFP) acquisition at 3T. Two radiologists analysed the signal intensity of the perilymph (cistern and cochlea) and endolymph (saccule and utricle) using a region of interest-based method for obtaining ratios between the analysed structures and the cerebrospinal fluid (CSF).ResultsObstructive vestibular schwannomas showed a markedly decreased perilymphatic signal in both cistern and cochlea; the cistern/CSF ratio (Ci/CSF) was 0.62. The decrease was more moderate in IAC meningiomas (Ci/CSF = 0.81). For Ci/CSF > 0.70, the tumour was more likely a meningioma, with a 92% sensitivity and 83% specificity. No endolymphatic signal changes were observed.ConclusionThe pronounced decrease in perilymphatic signal on a T2W SSFP sequence in obstructive vestibular schwannoma provides a new tool to differentiate schwannomas from IAC meningiomas, which may be useful to overcome the insufficiencies of morphological analysis.

47. Effect of Antipsychotic Medication on Hippocampal Function and Neurochemistry: A Longitudinal Study in Patients With Schizophrenia

Background: Our prior studies with PET and 15O have shown associations between hippocampal function and treatment response to antipsychotic drugs (APDs). In addition, we found elevated hippocampal glutamate in unmedicated patients with schizophrenia (SZ) but not in medicated. Here, we use a longitudinal design to evaluate the relationship between glutamate and function of the hippocampus in SZ in relation to treatment response to APDs. Methods: 34 SZ were scanned while unmedicated and after 6 weeks of APD. 23 matched healthy controls were also scanned twice six weeks apart. Imaging was done on a 3T head-only scanner equipped with a circularly polarized transmit/receive head coil. A high-resolution structural scan was acquired using the 3D T1-weighted magnetization-prepared rapid acquisition gradient-echo sequence ([TR/TE/ TI] = 2300/3.93/1100ms; flip angle = 12°; 256 × 256 matrix; and 1mm isotropic voxels). Eyes open resting-state fMRI (rsfMRI) was acquired using the gradient recalled echo-planar-imaging sequence (TR/TE = 2000/30ms, flip angle = 70°, field of view = 192mm3, 6mm slice thickness, 1mm gap, 30 axial slices, 225 acquisitions). rsfMRI data were preprocessed and analyzed using CONN toolbox and SPM12. Resting-state magnetic resonance spectroscopy was collected with a voxel prescribed in the left hippocampus (2.7 × 1.5 × 1cm) using the PRESS sequence optimized for glutamate (TR/TE = 2000/80ms, spectral bandwidth = 1024 points, 640 averages) and analyzed in jMRUI. A median split was used to separate SZ into treatment responders and non-responders (calculated as percent change in BPRS positive symptoms). Results: Before treatment, those who subsequently responded to treatment were characterized by significantly elevated glutamate levels compared to both healthy controls and nonresponders. Treatment responders but not non-responders or healthy controls glutamate levels significantly decreased over the 6-week course of treatment. Additionally, treatment responders demonstrated reduced hippocampal blood oxygen-level-dependent (BOLD) fMRI signal compared to healthy controls and nonresponders. Conclusion: Before treatment, both hippocampal glutamate levels and hippocampal BOLD signal appear to differentiate good treatment responders from poor treatment responders.

Clinical utility of optimized three-dimensional T1-, T2-, and T2*-weighted sequences in spinal magnetic resonance imaging.

This article reviews the clinical utility of 3D magnetic resonance imaging (MRI) sequences optimized for the evaluation of various intraspinal lesions. First, intraspinal tumors with hypervascular components and arteriovenous malformations (AVM) are clearly shown on contrast-enhanced (CE)-3D T1-weighted gradient-echo (GE) sequences with high spatial resolution. Second, dynamic CE-3D time-resolved magnetic resonance angiography (MRA) shows delineated feeding arteries of intraspinal AVM or arteriovenous fistula (AVF), greatly aiding subsequent digital subtraction angiography (DSA). Third, 3D multiecho T2*-weighted GE sequences are used to visualize intraspinal structures and spinal cord lesions and are sensitive to the magnetic susceptibility of intraspinal hemorrhages. Three-dimensional balanced steady-state free precession (SSFP) and multishot 3D balanced non-SSFP sequences produce contiguous thin images with high signal-to-noise ratio (SNR) in short scanning times. Intraspinal cystic lesions and small nerve-root tumors in subarachnoid space can be viewed using 3D balanced SSFP. Spinal cord myelomalacia and cord compression can be evaluated on fat-suppressed multishot 3D balanced non-SSFP. Finally, a 3D T2-weighted fast spin-echo (FSE) sequence with variable flip angle (FA) refocusing pulse improves through-plane spatial resolution over conventional 2D T2-weighted FSE sequences while matching image contrast.

3D printed renal cancer models derived from MRI data: application in pre-surgical planning.

To determine whether patient-specific 3D printed renal tumor models change pre-operative planning decisions made by urological surgeons in preparation for complex renal mass surgical procedures. From our ongoing IRB approved study on renal neoplasms, ten renal mass cases were retrospectively selected based on Nephrometry Score greater than 5 (range 6-10). A 3D post-contrast fat-suppressed gradient-echo T1-weighted sequence was used to generate 3D printed models. The cases were evaluated by three experienced urologic oncology surgeons in a randomized fashion using (1) imaging data on PACS alone and (2) 3D printed model in addition to the imaging data. A questionnaire regarding surgical approach and planning was administered. The presumed pre-operative approaches with and without the model were compared. Any change between the presumed approaches and the actual surgical intervention was recorded. There was a change in planned approach with the 3D printed model for all ten cases with the largest impact seen regarding decisions on transperitoneal or retroperitoneal approach and clamping, with changes seen in 30%-50% of cases. Mean parenchymal volume loss for the operated kidney was 21.4%. Volume losses>20% were associated with increased ischemia times and surgeons tended to report a different approach with the use of the 3D model compared to that with imaging alone in these cases. The 3D printed models helped increase confidence regarding the chosen operative procedure in all cases. Pre-operative physical 3D models created from MRI data may influence surgical planning for complex kidney cancer.

Surface-Based Morphometry of Human Brain: Intra-Individual Comparison Between 3T and 7T High Resolution Structural MR Imaging△

ObjectiveHigh resolution structural MR imaging can reveal structural characteristics of cerebral cortex and provide an insight into normal brain development and neuropsychological diseases. The aim of this study was to compare cortical structural characteristics of normal human brain between 3T and 7T MRI systems using surface-based morphometry based on high resolution structural MR imaging. Methods Twelve healthy volunteers were scanned by both 3T with 3D T1-weighted fast spoiled gradient recalled echo (3D T1-FSPGR) sequence and 7T with 3D T1-weighted magnetization-prepared rapid gradient echo (3D T1-MPRAGE) sequence. MRI data were processed with FreeSurfer. The cortical thickness, white and gray matter surface area, convexity, and curvature from data of 3T and 7T were measured and compared by paired t-test. Results Measurements of mean cortical thickness, total white matter surface area and gray matter surface area of 3T were larger than those of 7T (left hemisphere: P=0.000, 0.006, 0.020 respectively; right hemisphere: P=0.000, 0.000, 0.000 respectively). Surface-based morphometry over the whole brain demonstrated both reduced and increased measurements of cortical thickness, white and gray surface area, convexity, and curvature at 7T compared to 3T. Conclusions Inconsistency of brain structural attribute between 3T and 7T was confirmed, and researchers should be cautious about data when using ultrahigh field MR system to investigate brain structural changes.

Chapter 24 - Radiology and imaging for cavernous malformations

Cavernous malformations are low-flow vascular malformations that are histologically characterized by the lack of mural elements of mature vascular structures and intervening parenchymal neural tissue. They are often clinically quiescent, and may grow, bleed, and regress, but can also manifest clinically as neurologic deficits or seizures in the setting of an acute hemorrhage. The low-flow nature of cavernous malformations renders them inherently occult on cerebral angiography. Magnetic resonance imaging has become the mainstay imaging modality in evaluating cavernous malformations, producing characteristic imaging features that usually provide a straightforward diagnosis. Features on magnetic resonance imaging include a reticulated pattern of mixed hyper- and hypointensity on T1- and T2-weighted imaging, with a characteristic hypointense rim best appreciated on T2-weighted imaging or gradient-echo sequences. Contrast enhancement is useful for revealing coexisting developmental venous anomalies that are frequently associated with sporadic cavernous malformations, and may further support the diagnosis. Susceptibility-weighted imaging is highly sensitive for cavernous malformations and accompanying developmental venous anomalies, and is superior to gradient-echo sequences in screening for multifocal, familial cavernous malformations.

Free-Breathing Hepatobiliary Phase Gd-EOB-DTPA-Enhanced MR Imaging with Radial VIBE Sequence: Comparison with Conventional Cartesian VIBE Sequence

Purpose: To assess the feasibility of three-dimensional fat-suppressed T1-weighted gradient-echo sequence with radial volumetric interpolated breath-hold examination (rVIBE) compared with that of conventional Cartesian VIBE (cVIBE) sequence for free-breathing hepatobiliary phase of gadolinium-ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced MR imaging and to investigate the optimal number of radial views for rVIBE. Methods: Thirty patients who underwent hepatobiliary phase Gd-EOB-DTPA-enhanced MR imaging with freebreathing cVIBE and rVIBE sequences using radial views of 256 (rVIBE256), 512 (rVIBE512), and 1024 (rVIBE1024) for the evaluation of suspected liver tumors were enrolled in our study. Signal-to-noise ratios (SNRs) of the liver and image quality were compared between cVIBE and rVIBE sequences using the Steel-Dwass test of post hoc nonparametric multiple comparisons. Results: SNR of the liver was significantly higher for rVIBE with all three radial views than for cVIBE (all, P<0.001). The rVIBE256 showed a significantly lower SNR than rVIBE512 (P=0.004) and rVIBE1024 (P<0.001), but no significant difference was obtained between rVIBE512 and rVIBE1024 (P=0.122). The overall image quality was significantly higher for all rVIBE radial views than for cVIBE (all, P<0.001). The mean score of overall image quality was significantly lower for rVIBE256 than for rVIBE512 and rVIBE1024 (both, P<0.001), and there was no significant difference between rVIBE512 and rVIBE1024 (P=0.902). Conclusions: Our study suggests that rVIBE512 is more feasible in patients with diminished respiratory capacity in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MR imaging.

Visualization of Inflammation at Early Stage of Lung Cancer in Xenografted Temporally Immunosuppression Rats by Ferrioxamine Magnetic Resonance Imaging.

Physiological responses such as chronic inflammation and angiogenesis could be used as biomarkers for early detection of cancer with noninvasive imaging modalities. The present study reports the application of magnetic resonance imaging instrument to image the binding of ferrioxamine with hemin that allows visualizing the chronic inflammation foci of lung tissue of immunocompromised rats xenografted using small cell lung carcinoma. A low concentration of ferrioxamine (0.05 ± 0.02 μM·kg−1 of rat weight) deposited on tissue outside the vasculature was found to diffuse across the capillary walls to the interstitial space and inflammation foci, which provided a clear enhancement of T1-weighted gradient-echo sequence images. Ferrioxamine imaging allowed the determination of inflammatory sites and their localization in 3D fat-suppressed maximum intensity projections. The smallest dimension of foci that can be clearly determined is about 0.1 mm3. In concomitant to the in vivo imaging, analysis of histological tissue section showed the development of inflammatory sites. This study provides evidence that medical imaging instrument such as MRI scanner allows researchers to correlate images taken with MRI with those using high-resolution microscopy. Moreover, ferrioxamine is a useful molecular probe for determining chronic inflammation particularly at the very early stages of cancer.

The Role of Whole-Body Magnetic Resonance Imaging (WB-MRI) in Patients with Paroxysmal Nocturnal Hemoglobinuria (PNH)

▪INTRODUCTION: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal blood disorder of the hematopoietic stem cells characterized by chronic, uncontrolled complement-mediated intravascular hemolysis resulting in thrombophilia with thromboembolic events (TEs) and cytopenia due to bone marrow failure. PNH is the most vicious acquired thrombophilic state and TEs represent the leading cause of morbidity and mortality in PNH. PNH clone size correlates with the possibility to acquire a thrombosis but thromboses are also present in patients (pts) with small clones. Early detection of TEs is critically to improve the outcome in PNH with the availability of the terminal complement inhibitor eculizumab.METHODS: Between Dec 2013 and Jan 2016 whole-body magnetic resonance imaging (WB-MRI) scans at 1.5 Tesla (T) (Siemens MAGNETOM® Avanto) were performed in 37 pts (51% (19/37) females; median age 44 years (range 24-73 years), median D-dimer 0.23 mg/l (range 0.2-5.1 mg/l) with either PNH (n=23) or AA/PNH-syndrome (n=14). The protocol included a cranial time-of-flight magnetic resonance angiography (TOF-MRA), an arterial and venous contrast-enhanced MRA (CE-MRA), and a T1-weighted contrast-enhanced fat-suppressed gradient-echo sequence (radial volumetric interpolated breath-hold examination (VIBE)). Median clone size of GPI-deficient granulocytes (FLAER) was 88% (range 2.6-100%) and all pts were treated according to the German PNH guidelines, including the use of the terminal complement inhibitor eculizumab (70% (26/37)), with eculizumab being initiated in 23 pts prior to MRI. In the remaining pts eculizumab was initiated post MRI for reasons other than TEs. In 64% (24/37) of the pts no TEs were documented prior to the MRI scans. Two pts had a possible clinical history of TEs, including pulmonary embolism (PE) or deep venous thrombosis (DVT). The remaining pts (29% (11/37)) had a history of venous thromboses (e.g. DVT (5/11), portal venous thromboses (4/11), or vena caval thromboses (2/11)). One pt even had a myocardial infarction and two had a cerebral venous sinus thrombosis or a thalamic infarction. Six pts (16%) had more than just one documented TE in their medical history.RESULTS: In pts with the history of TEs we did not observe a progression of the existing TEs. There was no evidence of PE throughout observation time. In pts under chronic eculizumab therapy and prior TEs, additional bone infarcts involving the lower extremities were seen in one pt. In a second pt the diagnosis of a bilateral renal infarction was made. In two pts with no history of TEs bone infarcts of the lower extremities were seen (clone size >50%). In another pt a previously undiagnosed left renal infarction was observed. Moreover, a clinical non-critical occlusion of the right posterior tibial artery was identified in one pt.CONCLUSIONS: In contrast to previous studies there was no evidence for silent major TEs (e.g. PE) at the time of analysis. We were able to identify previously undiagnosed renal and bone infarctions (overall unknown prevalence) in our cohort of PNH pts. This is the first description of bone infarctions as possible thromboembolic complications in PNH. WB-MRI scans seem to be a novel and feasible method for the assessment of the whole vascular status of a PNH pt and allow the detection of previously unidentified vascular complications. This might directly affect treatment as eculizumab is indicated in PNH pts with TEs. Furthermore, in pts with existing TEs WB-MRI scans might be implicated to document their impact prior to treatment, especially in pts with major TEs or in pts with high disease acitivity and suspicion for TEs (e.g. recurrent abdominal pain or persisting dyspnea). DisclosuresDührsen:Amgen: Honoraria, Research Funding; Roche: Honoraria, Research Funding; Alexion Pharmaceuticals: Honoraria, Research Funding. Röth:Alexion Pharmaceuticals: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Novartis: Honoraria.

Free-breathing dynamic liver examination using a radial 3D T1-weighted gradient echo sequence with moderate undersampling for patients with limited breath-holding capacity

PurposeTo compare free-breathing radial VIBE with moderate undersampling (us-radial-VIBE) with a standard breathhold T1-weighted volumetric interpolated sequence (3D GRE VIBE) in patients unable to suspend respiration during dynamic liver examination. Material and methods23 consecutive patients underwent dynamic liver MR examination using the free-breathing us-radial-VIBE sequence as part of their oncologic follow-up. All patients were eligible for the free-breathing protocol due to severe respiratory artifacts at the planning or precontrast sequences. The us-radial-VIBE acquisitions were compared to the patientś last staging liver MRI including a standard breathhold 3D GRE VIBE.For an objective image evaluation, signal intensity (SI), image noise (IN), signal-to-noise ratio (SNR) and contrast-enhancement ratio (CER) were compared. Representative image quality parameters, including typical artifacts were independently, retrospectively and blindly scored by four readers. ResultsUs-radial-VIBE had significant lower SNR (p<0.0001) and higher IN (p<0.0001), whereas SI did not differ (p=0.62). Temporal resolution assessed with CER in the arterial phase showed higher values for us-radial-VIBE (p=0.028). Subjective image quality parameters received generally slightly higher scores for 3D GRE VIBE. In a smaller subgroup comprising patients with severe respiratory artifacts also at reference breathhold 3D GRE VIBE examination, us-radial-VIBE showed significantly higher image quality scores. Furthermore, there were generally more severe respiratory artifacts in 3D GRE VIBE, whereas streaking was characteristic in almost all us-radial-VIBE acquisitions but did not affect diagnostic validity. ConclusionFree-breathing dynamic liver imaging using us-radial-VIBE delivers accurate temporal resolution, low motion artifact susceptibility and good image quality and represents a promising alternative in patients unable to suspend respiration.

Model-Based Characterization of the Transpulmonary Circulation by Dynamic Contrast-Enhanced Magnetic Resonance Imaging in Heart Failure and Healthy Volunteers

Novel quantitative measures of transpulmonary circulation status may allow the improvement of heart failure (HF) patient management. In this work, we propose a method for the assessment of the transpulmonary circulation using measurements from indicator time intensity curves, derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) series. The derived indicator dilution parameters in healthy volunteers (HVs) and HF patients were compared, and repeatability was assessed. Furthermore, we compared the parameters derived using the proposed method with standard measures of cardiovascular function, such as left ventricular (LV) volumes and ejection fraction. In total, 19 HVs and 33 HF patients underwent a DCE-MRI scan on a 1.5 T MRI scanner using a T1-weighted spoiled gradient echo sequence. Image loops with 1 heartbeat temporal resolution were acquired in 4-chamber view during ventricular late diastole, after the injection of a 0.1-mmol gadoteriol bolus. In a subset of subjects (8 HFs, 2 HVs), a second injection of a 0.3-mmol gadoteriol bolus was performed with the same imaging settings. The study was approved by the local institutional review board.Indicator dilution curves were derived, averaging the MR signal within regions of interest in the right and left ventricle; parametric deconvolution was performed between the right and LV indicator dilution curves to identify the impulse response of the transpulmonary dilution system. The local density random walk model was used to parametrize the impulse response; pulmonary transit time (PTT) was defined as the mean transit time of the indicator. λ, related to the Péclet number (ratio between convection and diffusion) for the dilution process, was also estimated. Pulmonary transit time was significantly prolonged in HF patients (8.70 ± 1.87 seconds vs 6.68 ± 1.89 seconds in HV, P < 0.005) and even stronger when normalized to subject heart rate (normalized PTT, 9.90 ± 2.16 vs 7.11 ± 2.17 in HV, dimensionless, P < 0.001). λ was significantly smaller in HF patients (8.59 ± 4.24 in HF vs 12.50 ± 17.09 in HV, dimensionless, P < 0.005), indicating a longer tail for the impulse response. Pulmonary transit time correlated well with established cardiovascular parameters (LV end-diastolic volume index, r = 0.61, P < 0.0001; LV ejection fraction, r = -0.64, P < 0.0001). The measurement of indicator dilution parameters was repeatable (correlation between estimates based on the 2 repetitions for PTT: r = 0.94, P < 0.001, difference between 2 repetitions 0.01 ± 0.60 second, for λ: r = 0.74, P < 0.01, difference 0.69 ± 4.39). Characterization of the transpulmonary circulation by DCE-MRI is feasible in HF patients and HVs. Significant differences are observed between indicator dilution parameters measured in HVs and HF patients; preliminary results suggest good repeatability for the proposed parameters.

Clinical evaluation of three‐dimensional late enhancement MRI

To assess the diagnostic value of three-dimensional late enhancement (3D-LGE) for the detection of myocardial necrosis in a routine clinical setting. 3D-LGE has been proposed as a novel magnetic resonance (MR) technique for the accurate detection of myocardial scar in both the ventricles and atria. Its performance in clinical practice has been poorly examined. Fifty-seven patients referred for cardiac MR examination including scar imaging were prospectively enrolled. Gadolinium enhanced single breathhold 3D T1-weighted gradient-echo inversion recovery sequence and a conventional 2D-LGE sequence were performed using a 1.5 Tesla clinical MR imaging system. The presence, pattern and transmurality of LGE, diagnostic accuracy and level of diagnostic confidence as well as image quality (median quality, mean LGE signal intensity, sharpness, virtual scan time) were graded on a 4-point scale. Interpretable images were obtained in 52/57 2D-LGE and in 47/57 3D high-resolution exams. LGE was detected in 10 patients with ischemic pattern, 9 with nonischemic pattern, while it was absent in 28, resulting in a total of 47 complete datasets. The detection of global and segmental LGE as well as its transmural extent were similar for both techniques (P = 0.65, P = 0.305, and P = 0.15, respectively). Image quality (median quality, LGE/ myocardial and LGE/ blood pool sharpness) was similar for both techniques (P = 0.740, P = 0.34, and P = 1.00, respectively), but LGE signal intensity was higher with 2D (P = 0.020). 3D-LGE diagnostic and quality scores were comparable to 2D-LGE in a routine clinical setting. Further technical refinement is required for 3D LGE to offer a reliable alternative for high quality scar imaging. 2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;45:1675-1683.

Liver MR Imaging in Children: Current Concepts and Technique.

Magnetic resonance (MR) imaging is increasingly being used for comprehensive evaluation of liver diseases in children because of the lack of radiation and better lesion detection and characterization. Liver examination involves routine sequences such as T2-weighted, balanced steady-state free precession, and in-phase and out-of-phase sequences. Dynamic imaging is an essential component of liver examination to characterize focal lesions and involves capturing snapshots of the passage of contrast material in the arterial, portal venous, equilibrium, and sometimes hepatobiliary phases, generally by using T1-weighted three-dimensional gradient-echo sequences. Optimal arterial phase imaging is important for detection and characterization of hypervascular lesions. In the equilibrium phase, the concentration of contrast material is similar in the microvasculature and the extracellular interstitial space. Some superficial, spreading, inflammatory lesions are better seen on equilibrium phase images. Meticulous attention to intravenous access and use of an appropriate timing method are critical for successful dynamic imaging. Commonly used contrast media for liver imaging include gadolinium-based extracellular contrast agents and hepatobiliary contrast agents. A portion of hepatobiliary contrast agents such as gadoxetate and gadobenate is taken up by hepatocytes and excreted through bile. Hepatobiliary phase images acquired after hepatobiliary contrast agent administration are increasingly used to characterize liver lesions in children, such as focal nodular hyperplasia. Interpretation of liver MR images involves synthesis of information acquired from evaluation of background hepatic parenchyma, detection of lesions, and evaluation of signal intensity characteristics on images obtained with various sequences to arrive at a diagnosis or reasonable differential diagnoses. Understanding the appropriate technique, sequences, and contrast media when performing pediatric liver MR imaging is important for high diagnostic yield. (©)RSNA, 2016.

Comparison of Maximum Signal Intensity of Magnevist Contrast Agent in Modified T1 Weighted Spin Echo, T1 Weighted Fast Spin Echo and T1 Weighted Gradient Echo Sequences

Background: Nowadays MRI examinations have been widely used in clinical applications for many diagnoses. The use of contrast agent in MRI improves lesion detection and characterization and causes more accurate diagnosis. Objectives: The aim of this study was comparing to optimal dose of Magnevist contrast agent in modified T1W SE (Spin Echo), T1W FSE (Fast Spin Echo) and T1W GRE (GRadient Echo) and effect of scan parameters of these sequences on the maximum SI of Magnevist contrast agent. Material and Method: This study was done on a phantom that was containing test tubes. These test tubes were filled with 30ml saline mixed with different doses of Magnevist contrast agent. In this study, some scan parameters of T1W pulse sequences were changed to achieve optimal parameters for maximum SI of contrast agent. In this study maximum signal intensity of each image was measured by ImageJ software. Results: The results of this study show that there are differences in maximum SI in different T1W pulse sequences with changing scan parameters. This study shows that 0.625 mmol/L of Magnevist has maximum SI in all of sequences. The maximum SI can be seen at GRE, SE and FSE sequences, respectively. Conclusion: Using routine and changed scan parameters, each pulse sequence reaches different maximum SI in specific concentration , which is highest in 2D SPGR (SPoiled GRadient) with flip angle = 75˚ and least in T1W SE with TE (Time of Echo) = 40ms.

Usefulness of breath-hold inversion recovery-prepared T1-weighted two-dimensional gradient echo sequence for detection of hepatocellular carcinoma in Gd-EOB-DTPA-enhanced MR imaging

The aim is to evaluate the diagnostic performance and the added value of breath-hold inversion recovery-prepared T1-weighted two-dimensional gradient echo (IR-2D-GRE) sequence for detection of hepatocellular carcinoma (HCC) in patients with insufficient liver parenchymal enhancement during the hepatobiliary phase (HBP) of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI). Seventeen patients with a quantitative liver-to-spleen contrast ratio of ≤1.5 on HBP images and 36 HCCs were included. Liver-to-lesion contrast ratios on HBP images obtained with IR-2D-GRE sequence were significantly higher than those with three-dimensional gradient echo sequence. The addition of IR-2D-GRE sequence during HBP of Gd-EOB-DTPA-enhanced MRI yielded higher diagnostic accuracy and improved sensitivity.

How we do it: MR enterography.

Magnetic resonance enterography (MRE) now plays a central role in diagnosing pediatric inflammatory bowel disease (IBD), and its role in other intestinal pathologies such as scleroderma is gradually expanding. MRE helps distinguish between Crohn disease and ulcerative colitis, defining extent and severity. Standard MRE protocols can be optimized in children and adolescents to be diagnostic and well tolerated, both of which are important with increasing use of serial MRE in pediatric IBD for monitoring treatment response and evaluating complications. MRI is especially suited to this role given its lack of ionizing radiation. MRE compliance can be improved through patient education. Differing from adult MRE, pediatric MRE protocols use weight-based formulas to calculate oral and intravenous contrast media and antispasmodic agent doses, using either hyoscine-N-butylbromide or glucagon. Nausea is more commonly experienced with glucagon; however vomiting occurs in <10% of children with either agent. Standard and advanced sequences applied in adults are also used in children and adolescents. These include static and cinematic balanced steady-state free precession sequences, single-shot T2-weighted sequences, diffusion-weighted imaging and pre- and post-contrast 3-D T1-weighted gradient echo sequences. Magnetization transfer imaging and quantitative assessment of bowel to distinguish inflammation and fibrosis are not yet standard in pediatric MRE, but show promise.

Nodal staging in rectal cancer: why is restaging after chemoradiation more accurate than primary nodal staging?

PurposeThis study aims to explore the influence of chemoradiation treatment (CRT) on rectal cancer nodes and to generate hypotheses why nodal restaging post-CRT is more accurate than at primary staging.MethodsThirty-nine patients with locally advanced rectal cancer underwent MRI pre- and post-CRT. All visible mesorectal nodes were measured on a 3D T1-weighted gradient echo (3D T1W GRE) sequence with 1-mm3 voxels and matched between pre- and post-CRT-MRI and with histology by lesion-by-lesion matching. Change in number and size of nodes was compared between pre- and post-CRT-MRI. ROC curves were constructed to assess diagnostic performance of size.ResultsEight hundred ninety-five nodes were found pre-CRT: 44 % disappeared and 40 % became smaller post-CRT. Disappearing nodes were initially significantly smaller than nodes that remained visible post-CRT: 2.9 mm vs. 3.8 mm. cN+ stage was predicted in 97 % pre-CRT and 36 % of patients had ypN+ post-CRT. ypN+ patients had significantly larger nodes than ypN0 patients both pre- and post-CRT. Optimal size cutoff for post-CRT ypN stage prediction was 2.5 mm (area under the curve (AUC) of 0.78) at MRI.ConclusionsAfter CRT, most lymph nodes become smaller, and many disappear. Size predicts disappearance and node positivity. Together with a low prevalence of ypN+, this can explain the higher accuracy of nodal staging after CRT than in a primary staging setting, possibly of use when considering organ-preserving strategies after CRT.