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BACKGROUND AND PURPOSE: Rapid brain MR imaging is often substituted for head CT in multiply imaged patients with shunted hydrocephalus. Fast TSE-T2 sequences are commonly used in these protocols. One limitation of TSE-T2 sequences is the decreased catheter delineation compared with CT. The aim of this study was to compare fast TSE-T2 with rapid SS-GRE sequences in the evaluation of intracranial shunt catheter delineation as part of a rapid nonsedated pediatric brain MR imaging protocol. MATERIALS AND METHODS: We evaluated the findings from 179 consecutive patients who underwent routine clinical imaging according to the rapid nonsedated pediatric brain MR imaging protocol. Comparison of the quality of intracranial shunt catheter localization on SS-GRE versus TSE-T2 was performed. RESULTS: Of the total of 179 rapid nonsedated pediatric brain MR images that were reviewed, 62 (35%) had an intracranial shunt catheter. The shunt catheter tip was better localized on the SS-GRE than on the TSE-T2 images in 49/62 (79%) of these patients. Of the remaining 13/62 (21%), the TSE-T2 was either better or equivalent in localizing the shunt catheter tip. CONCLUSIONS: Our study shows that rapid SS-GRE sequences can provide better delineation of standard intracranial shunt catheters than standard rapid MR imaging protocols containing only fast TSE-T2 sequences.

Intensity inhomogeneities in magnetic resonance images (MRI) are a frequently occurring artefact, and result in the same tissue class to have vastly different intensities within an image. These inhomogeneities can be modelled by a slowly varying field, which is also called the bias field. Previous phantom-, image- or sequence based approaches suffer from long scan times, post-processing times or do not sufficiently remove the intensity variations. These intensity variations cause problems for quantitative image analysis algorithms (segmentation, registration) as well as clinicians (e.g. by complicating the visual assessment). This paper presents a novel technique (COIN, correction of intensity inhomogeneities) that uses two calibration images (fast spoiled gradient echo) to map a parameter containing the bias field, which is specific to the patient during a particular exam. This parametric map can then be used to correct any other images acquired during the same exam, regardless of the sequence employed. By using a short repetition time (less than 5 ms) for the calibration scans, the additional scan time is reduced to 60 s (max). The subsequent post-processing time is approximately 60 s per 20 slices. We successfully validate our approach on simulated brain MRI as well as real liver and spinal images. These images were acquired with a number of different coils, sequences and weightings. A comparison of our method with an existing, commercially available algorithm by radiologists shows that COIN is superior.

The purpose of this study was to assess the repeatability of a dual gradient-recalled echo (GRE) muscle functional MRI technique. On 2 days, subjects (n = 8) performed 10 s isometric dorsiflexion contractions under conditions of: (1) maximal voluntary contraction (MVC), (2) 50% MVC (50% MVC), or (3) 50% MVC with concurrent proximal arterial cuff occlusion (50% MVC(cuff)). Functional MRI data were acquired using single-slice dual GRE (TR/TE = 1000/6, 46 ms)-echo planar imaging for 20 s before, during, and for 180 s after each contraction. The mean signal intensity (SI) time courses at each TE (SI(6) and SI(46), reflecting variations in blood volume and %HbO(2), respectively) from the tibialis anterior (TA) and extensor digitorum longus (EDL) muscles were characterized with the post-contraction change in SI and the time-to-peak SI (DeltaSI and TTP, respectively). DeltaSI(6) following an MVC was 36% higher than that obtained after a 50% MVC (p = 0.048). For DeltaSI(6), the highest intraclass correlation coefficients (ICCs) were observed for the TA muscle in the 50% MVC and MVC conditions, with values of 0.83 (p = 0.01) and 0.88 (p = 0.005), respectively. Bland-Altman plots revealed repeatability coefficients (RCs) for the 50% MVC and MVC conditions in the TA muscle of 1.9 and 1.4, respectively. The most repeatable measures for DeltaSI(46) were obtained for the 50% MVC and MVC conditions in the EDL muscle (p = 0.01 and p = 0.04, respectively). Bland-Altman plots revealed RC's for 50% MVC and MVC conditions in the EDL muscle of 3.9 and 5.7, respectively. DeltaSI(6) and DeltaSI(46) increased as a function of the contraction intensity. The repeatability of the method depends on the muscle and contraction condition being evaluated, and in general, is higher following an MVC.

To assess the accuracy of four fat quantification methods at low-flip-angle multiecho gradient-recalled-echo (GRE) magnetic resonance (MR) imaging in nonalcoholic fatty liver disease (NAFLD) by using MR spectroscopy as the reference standard.In this institutional review board-approved, HIPAA-compliant prospective study, 110 subjects (29 with biopsy-confirmed NAFLD, 50 overweight and at risk for NAFLD, and 31 healthy volunteers) (mean age, 32.6 years +/- 15.6 [standard deviation]; range, 8-66 years) gave informed consent and underwent MR spectroscopy and GRE MR imaging of the liver. Spectroscopy involved a long repetition time (to suppress T1 effects) and multiple echo times (to estimate T2 effects); the reference fat fraction (FF) was calculated from T2-corrected fat and water spectral peak areas. Imaging involved a low flip angle (to suppress T1 effects) and multiple echo times (to estimate T2* effects); imaging FF was calculated by using four analysis methods of progressive complexity: dual echo, triple echo, multiecho, and multiinterference. All methods except dual echo corrected for T2* effects. The multiinterference method corrected for multiple spectral interference effects of fat. For each method, the accuracy for diagnosis of fatty liver, as defined with a spectroscopic threshold, was assessed by estimating sensitivity and specificity; fat-grading accuracy was assessed by comparing imaging and spectroscopic FF values by using linear regression.Dual-echo, triple-echo, multiecho, and multiinterference methods had a sensitivity of 0.817, 0.967, 0.950, and 0.983 and a specificity of 1.000, 0.880, 1.000, and 0.880, respectively. On the basis of regression slope and intercept, the multiinterference (slope, 0.98; intercept, 0.91%) method had high fat-grading accuracy without statistically significant error (P.05). Dual-echo (slope, 0.98; intercept, -2.90%), triple-echo (slope, 0.94; intercept, 1.42%), and multiecho (slope, 0.85; intercept, -0.15%) methods had statistically significant error (P.05).Relaxation- and interference-corrected fat quantification at low-flip-angle multiecho GRE MR imaging provides high diagnostic and fat-grading accuracy in NAFLD.

A radiofrequency (RF) excitation scheme is presented in which flip angle is encoded in the phase of the resulting excitation. This excitation is implemented with nonselective hard pulses, and is used to give flip angle maps over three-dimensional volumes. This phase-sensitive B1 mapping excitation can be combined with various acquisition methods such as gradient recalled echo (GRE) and echo-planar (EP) readouts. Imaging time depends primarily on the readout method, and is roughly equivalent to the imaging time of conventional double-angle techniques for three-dimensional acquisition. The phase-sensitive method allows imaging over a much wider range of flip angles than double-angle methods. Phantom and in vivo results are presented comparing the phase-sensitive method with the conventional double-angle method, demonstrating the ability of the phase-sensitive method to measure a wider range of flip angles than double-angle methods.

With improved B-0 homogeneity along with satisfactory gradient performance at high magnetic fields, snapshot gradient-recalled echo-planar imaging (GRE-EPI) would perform at long echo times (TEs) oil the order of T-2*, which intrinsically allows obtaining strongly T-2*-weighted images with embedded substantial anatomical details in ultrashort time. The aim of this study was to investigate the feasibility and quality of long TE snapshot GRE-EPI images of rat brain at 9.4 T. When compensating for B-0 inhomogeneities, especially second-order shim terms, a 200x200 mu m(2) in-plane resolution image was reproducibly obtained at long TE (> 25 ms). The resulting coronal images at 30 ms had diminished geometric distortions and, thus, embedded Substantial anatomical details. Concurrently with the very consistent stability, such GRE-EPI images should permit to resolve functional data not only with high specificity but also with substantial anatomical details, therefore allowing coregistration of the acquired functional data oil the same image data set. (C) 2008 Elsevier Inc. All rights reserved.

To implement parallel imaging algorithms in fast gradient recalled echo sequences for myocardial perfusion imaging and evaluate image quality, signal-to-noise ratio (SNR), contrast-enhancement ratio (CER), and semiquantitative perfusion parameters.In 20 volunteers, myocardial perfusion imaging with gadobutrol was performed at rest using an accelerated TurboFLASH sequence (TR 2.3 milliseconds, TE 0.93 milliseconds, flip angle [FA] 15 degrees) with GRAPPA, R=2. A nonaccelerated TurboFLASH sequence with similar scan parameters served as standard of reference. Artifacts were assessed qualitatively. SNR, CER, and CNR were calculated and semiquantitative perfusion parameters were determined from fitted SI-time curves.Phantom measurements yielded significant higher SNR for nonaccelerated images (P0.001). CER was equal; differences in CNR were statistically nonsignificant. The evaluation of semiquantitative perfusion parameters yielded significantly higher peak signal intensities in nonaccelerated images (P0.001). Differences in maximum upslope were statistically nonsignificant. A qualitative examination of all images for artifacts by 2 board-certified radiologists yielded a significant reduction in dark rim artifacts with GRAPPA, R=2 (P0.001).The application of GRAPPA with an acceleration factor of R=2 leads to a significant reduction of dark rim artifacts in fast gradient recalled echo sequences.

Blood oxygenation level dependent (BOLD) MRI is sensitive to changes in regional oxygen supply versus demand and is therefore potentially useful in evaluating susceptibility to ischemic injury. Recently, we have demonstrated the use of BOLD MRI to evaluate intrarenal oxygenation using single shot echo-planar imaging (EPI). Here, we present an alternate implementation of BOLD MRI sequence, using multiple gradient echoes, that does not require any specialized hardware.

Neurocysticercosis (NCC) is caused when the cysticercus larvae of Taenia solium infect the central nervous system. The larvae usually land in the parenchymal tissue, but quite rarely can lodge in the ventricles and cisterns of the brain. Unlike parenchymal NCC, it is not easy to demonstrate the cysticercus cysts within the cerebrospinal fluid spaces. Computed tomography and even conventional MR sequences can fail to detect such cysts. However, obtaining three-dimensional spoiled gradient recalled echo imaging sequences can help in improving the detection of intraventricular NCC, as is borne out by a case described in the present report. The use of such special MR sequences is therefore strongly advocated in suspected cases of intraventricular NCC.

The purpose of our study was to compare the detectability of malignant hepatic tumors on ferumoxides-enhanced MRI using five gradient-recalled echo sequences at different TEs.Ferumoxides-enhanced MRIs obtained in 31 patients with 50 malignant hepatic tumors (33 hepatocellular carcinomas, 17 metastases) were reviewed retrospectively by three independent offsite radiologists. T1-weighted gradient-recalled echo images with TEs of 1.4 and 4.2 msec; T2*-weighted gradient-recalled echo images with TEs of 6, 8, and 10 msec; and T2-weighted fast spin-echo images of livers were randomly reviewed on a segment-by-segment basis. Observer performance was tested using the McNemar test and receiver operating characteristic analysis for the clustered data. Lesion-to-liver contrast-to-noise ratio was also assessed.Mean lesion-to-liver contrast-to-noise ratios were negative and lower with gradient-recalled echo at 1.4 msec than with the other sequences. Sensitivity was higher (p0.05) with gradient-recalled echo at 6, 8, and 10 msec and fast spin-echo sequences (75-83%) than with gradient-recalled echo sequences at 1.4 and 4.2 msec (46-48%), and was higher (p0.05) with gradient-recalled echo sequence at 8 msec (83%) than with gradient-recalled echo at 6 msec and fast spin-echo sequences (75-78%). Specificity was comparably high with all sequences (95-98%). The area under the receiver operating characteristic curve (A(z)) was greater (p0.05) with gradient-recalled echo at 6, 8, and 10 msec and fast spin-echo sequences (A(z) = 0.91-0.93) than with gradient-recalled echo sequences at 1.4 and 4.2 msec (A(z) = 0.82-0.85).In the detection of malignant hepatic tumors, gradient-recalled echo sequences at 8 msec showed the highest sensitivity and had an A(z) value and lesion-to-liver contrast-to-noise ratio comparable with values from gradient-recalled echo sequences at 6 and 10 msec and fast spin-echo sequences.

Sixty-two patients underwent magnetic resonance (MR) imaging of the liver with the automated contrast material bolus-detection technique. Arterial phase MR images were assessed quantitatively and qualitatively. In 23 patients, a test bolus of contrast material was injected intravenously before dynamic MR imaging. There was good correlation and agreement between delay times estimated with both timing methods. Eighty-three percent of arterial phase images obtained with automated contrast material bolus detection were optimal. There was good correlation and agreement between delay times estimated with both timing methods. Optimal hepatic arterial phase MR images can be obtained routinely with automated detection of a contrast material bolus.

Purpose To evaluate the different signal characteristics of focal hepatic lesions on ferumoxides-enhanced MR imaging, including T1-weighted spoiled gradient recalled echo (GRE) images using different echo times (TE) and T2- and T2*-weighted images. Materials and Methods Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients who were referred for evaluation of known or suspected hepatic malignancies. One hundred and seven lesions (42 hepatocellular carcinomas [HCC], 40 metastases, 13 cysts, eight hemangiomas, three focal nodular hyperplasias [FNHs], and one cholangiocarcinoma) were evaluated. Postcontrast MR imaging included 1) T2-weighted FSE; 2) T2*-weighted GRE; 3) T1-weighted spoiled GRE using moderate (TE = 4.2–4.4 msec) TE; and 4) minimum (TE = 1.8–2.1 msec) TE. Signal intensities of the focal lesions were rated by two radiologists in conference as follows: hypointense, isointense or invisible, hyperintense, and markedly hyperintense. Lesion-to-liver contrast-to-noise ratio (C/N) was measured by one radiologist for a quantitative assessment. Results On ferumoxides-enhanced FSE images, 92% of cysts were “markedly hyperintense” and most of the other lesions were “hyperintense”, and the mean C/N of cysts was significantly higher than that of other focal lesions. T2*-weighted GRE images showed most lesions with similar hyperintensities and the mean C/N was not significantly different between any two types of lesion. T1-weighted GRE images using moderate TE showed all FNHsand hemangiomas, 29 (69%) HCCs and eight (20%) metastases as “hyperintense”. On T1-weighted GRE images using minimum TE, however, all HCCs and metastasis except one were iso- or hypointense, while all of the FNHs and hemangiomas were hyperintense. Ring enhancement was highly suggestive of malignant lesions, and was more commonly seen on the minimum TE images than on the moderate TE images. Conclusion Addition of T1-weighted GRE images using minimum and moderate TE is helpful for characterizing focal lesions in ferumoxides-enhanced MR imaging. J. Magn. Reson. Imaging 2002;15:573–583. © 2002 Wiley-Liss, Inc.

The purpose of this study was to determine the accuracy of a multiphasic gadolinium-enhanced three-dimensional (3D) fast spoiled gradient-recalled echo sequence alone in the detection and characterization of focal liver lesions compared with a comprehensive liver evaluation using multiphasic gadolinium-enhanced 3D fast spoiled gradient-recalled echo, T1-weighted, and fat-suppressed fast spin-echo T2-weighted sequences.A retrospective review of abdominal MR imaging examinations in 61 patients was performed. All MR examinations included unenhanced spin-echo T1-weighted, unenhanced fat-suppressed fast spin-echo T2-weighted, and multiphasic gadolinium-enhanced 3D fast spoiled gradient-recalled echo sequences obtained during successive breath-holds. The liver was evaluated for focal lesions first with the 3D spoiled gradient-recalled echo sequences and then, during a separate sitting, with the T1- and T2-weighted sequences. The usefulness of each sequence in the detection and characterization of lesions was recorded. The gold standard for lesion detection and characterization was all three imaging sequences reviewed together.A total of 114 focal liver lesions were identified, 54 of which were simple cysts. The 3D spoiled gradient-recalled echo sequence alone detected 92 (81%) of the 114 lesions, and the T1- and T2-weighted sequences detected 95 (83%) of the 114 lesions. Of the 60 lesions that were not simple cysts, the 3D spoiled gradient-recalled echo sequence alone detected 58 (97%), and T1- and T2-weighted sequences detected 51 (85%). In 24% of the patients with lesions, the T1- and T2-weighted sequences were found to be helpful for the characterization of lesions.A multiphasic contrast-enhanced 3D fast spoiled gradient-recalled echo sequence alone detects most of the clinically relevant focal liver lesions. Additional liver examination using both unenhanced T1- and T2-weighted sequences is helpful for lesion characterization but increases the detection rate only minimally.

This unit presents a basic protocol of conventional and fast spin echo acquisition for detecting spondolysis deformans. The margins of the osteophytosis associated with spondylosis deformans are generally well defined utilizing fast spin echo acquisitions. An alternate protocol is presented for gradient recalled echo acquisitions that may be used in the sagittal and/or transverse planes to clearly distinguish between discs and soft tissue, and to clarify the spinal neural foramen in the cervical region.

Gadolinium-enhanced dynamic magnetic resonance (MR) images in 90 patients were reviewed to assess the artifacts mimicking portal venous thrombosis. The incidence of definite signal-intensity decrease mimicking pathologic condition was higher (P < 0.01) in the right (8%) and left (9%) portal vein branches and portal trunk (6%) than in the splenic (0%) or superior mesenteric (1%) vein with equilibrium-phase images. Radiologists should remember that dynamic MR images occasionally show signal-intensity decrease mimicking portal venous thrombosis due to flow artifact.

The purpose of this study was to compare the performance of in-phase and out-of-phase gradient recalled echo (GRE) pulse sequences on paramagnetic contrast-enhanced magnetic resonance (MR) imaging of malignant liver lesions.Fifty patients (27 women, 23 men; mean age = 50 +/- 27 years) with known or suspected focal liver lesions, nine of whom had a fatty liver, were examined at 1.5 T before and 60 min after injection of gadobenate dimeglumine at a dose of 0.05 or 0.1 mmol/kg using two GRE techniques: echo time of 2.3 ms (out-of-phase) or 4.6 ms (in-phase). Liver signal-to-noise ratio (SNR) and lesion-liver contrast-to-noise ratio (CNR) were calculated.In patients with a nonfatty liver, liver SNR increased from 26 +/- 9 to 41 +/- 17 on in-phase images and from 28 +/- 8 to 45 +/- 14 on out-of-phase images. In patients with a fatty liver, in-phase images provided significantly higher (p0.01) liver SNR than did out-of-phase images predose (34 +/- 8 on in-phase vs. 21 +/- 8 on out-of-phase) and postdose (44 +/- 13 on in-phase vs. 33 +/- 14 on out-of-phase). In patients with a nonfatty liver, lesion-liver CNR was similar on in-phase and out-of-phase images, predose and postdose. In patients with fatty liver, lesion-liver CNR was significantly (p0.01) lower on out-of-phase images on predose and postdose images.In-phase GRE imaging is recommended for imaging focal liver lesions on paramagnetic contrast-enhanced MR imaging in patients with fatty infiltration of the liver.

We have examined whether automated image registration can be used to combine metabolic information from SPECT knee scans with anatomical information from MRI. Ten patients, at risk of developing OA due to meniscal surgery, were examined. 99mTc methyldiphosphonate SPECT, T2-weighted fast spin echo (FSE) MRI, and T1-weighted, 3D fat-suppressed gradient recalled echo (SPGR) MRI images were obtained. Registration was performed using normalized mutual information. For each patient, FSE data was registered to SPGR data, providing a composite MRI image with each voxel represented by two intensities (ISPGR, IFSE). Modifications to the registration algorithm were made to allow registration of SPECT data (one intensity per voxel) to composite MRI data (2 intensities per voxel). Registration sources was assessed by visual inspection of uptake localization over expected anatomical locations, and the absence of uptake over unlikely sites. Three patients were discarded from SPECT-MRI registration tests since they had metallic artifacts that prevented co-registration of MR data. Registration of SPECT to SPGR or FSE data alone proved unreliable, with less than 50% of attempts succeeding. The modified algorithm, treating co-registered SPGR and FSE data as a two-value-per-voxel image, proved most reliable, allowing registration of all patients with no metallic artifacts on MRI.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Gradient recalled echo (GRE) T2 weighted imaging is more widely used as a standard magnetic resonance (MR) pulse sequence because of its exquisite sensitivity for detection of cerebral hemorrhages. Signal loss on GRE sequence is due to increased sensitivity of this sequence to magnetic susceptibility induced by static field inhomogeneities arising from paramagnetic blood breakdown products. T2 FNx01 signal intensity loss seen in GRE sequence is greater with longer TE, smaller flip angle, and larger magnetic field strength. The purpose of this review is to discuss the role of GRE imaging in cerebral disorders with bleed. Because of the sensitivity of this sequence to microbleeds, we describe its edge over baseline imaging sequences to provide insight in the etiology of certain diseases.

Objective. To compare fat-suppressed fast spin-echo (FSE) T2-weighted images with gradient-recalled echo (GRE) T2*-weighted images in the evaluation of anteroinferior labral tears. Design. MR images were retrospectively reviewed by two radiologists masked to the history and arthroscopic findings. They separately interpreted the anteroinferior labrum as torn or intact, first on one pulse sequence and then, 4 weeks later, on the other sequence. The MR interpretations were correlated with the arthroscopic findings. Patients. Nine patients with anteroinferior labral tears, and nine similarly-aged patients with normal, labra were studied. Results and conclusions. Observer 1 had a sensitivity of 0.56 on the GRE images and 0.67 on the FSE images (P>0.5), with a specificity of 1.0 for both sequences. Observer 2 had a sensitivity of 0.78 and a specificity of 0.89 for both sequences. In this small study there is no significant difference between GRE and fat-suppressed FSE images in their ability to diagnose anteroinferior labral tears. When evaluating the labrum with conventional MRI, axial fat-suppressed FSE T2-weighted images can be used in place of GRE images without a loss of accuracy.

We compared dynamic contrast-enhanced three-dimensional time of flight (3DTOF) magnetic resonance angiography (MRA) with two-dimensional time of flight (2DTOF) MRA with cardiac compensated fast gradient recalled echo (C-MON) and conventional angiography (CA) when it was available. C-MON re-orders the normal data acquisition to minimize ghosting artifacts generated by pulsatile flow. The initial phase of the study involved optimization of parameters and comparison C-MON with no C = MON in eight patients and volunteers. The final phase of the study involved 53 patients who were imaged with contrast-enhanced 3DTOF MRA and 2DTOF MRA with C-MON. Thirty of these patients also had CA. In the initial phase, 2DTOF MRA with C-MON was found to be equal (n = 3) or superior (n = 5) to 2DTOF without C-MON. In the final phase, the agreement among all imaging modalities varied from substantial to almost perfect (Cohen's kappa = .6-.83). The lowest agreement was using 2DTOF to evaluate the external iliac segments. The among suggested treatments varied from substantial to almost perfect for all imaging modalities (Cohen's kappa = .73-93). The diagnostic efficacies of 2DTOF with C-MON and contrast-enhanced 3DTOF were high overall, with the lowest value being a specificity of 63% for one reader in the evaluation of an external iliac segment using 2DTOF. In summary, 2DTOF with C-MON helped to eliminate artifacts due to pulsatility in the iliac arterial segments. In our experience, both dynamic contrast-enhanced 3DTOF MRA and 2DTOF MRA with C-MON performed well in the evaluation of the iliac arteries. Both studies have high interobeserver agreement and high diagnostic efficacy. Contrast-enhanced 3DTOF MRA should be reserved for situations in which the iliac vessels are extremely tortuous or occluded or the external iliac segments are poorly seen.

To compare liver enhancement and lesion-liver contrast on T1-weighted (T1W) gradient recalled echo (GRE), spin-echo (SE) and fat-suppressed SE (FS-SE) pulse sequences at Manganese-DPDP (Mn-DPDP) enhanced magnetic resonance (MR) imaging of the liver. PATIENTS AND METHODS. Twenty-one patients with known liver lesions were administered 5 mumol/kg of Mn-DPDP. TIW GRE (78/2.3/80 degrees), SE and F-SE (300/12) images were obtained before and 15 min after Mn-DPDP. Signal/noise ratio (SNR) and lesion-liver contrast/noise ratio (CNR) were calculated for each pulse sequence.Liver SNR (n = 21) and lesion-liver CNR (n = 10) increased significantly after Mn-DPDP on all three pulse sequences (P0.0001). Liver SNR was highest on the FS-SE and GRE pulse sequences (FS-SE = 43.8, GRE = 38.4, SE = 29.2). Lesion-liver CNR was highest on the FS-SE pulse sequence (FS-SE = -29.3, SE = -23.2, GRE = -19.8), which was significantly higher than the GRE pulse sequence (P0.05).The T1-weighted fat-suppressed SE (FS-SE) pulse sequence provides highest liver enhancement and lesion-liver contrast and is recommended for Mn-DPDP enhanced MR imaging.

Myocardial tagging with magnetic resonance (MR) imaging offers unique possibilities for noninvasive left ventricular (LV) strain analysis. True three-dimensional strain analysis can be achieved with tags implemented in cardiac short axis and long axis images. Spin-echo (SE) techniques have been used for these studies. However, this approach is time-consuming: images at different phases of the cardiac cycle have to be obtained in successive measurements and hence the total number of measurements equals the number of time frames. Moreover, the images are often degraded by flow and motion artifacts. The purpose of this study was to optimize a faster and more robust MR tagging sequence for use on a clinical whole-body 1 T MR system with optimal persistence of the tags during the entire cardiac cycle. The tagging pulses were implemented in gradient-recalled-echo (GRE) sequences and compared to SE-based acquisitions. The effects of the use of flow-compensating gradients, the excitation angles, and the angles of the saturation pulses have been studied with MR signal simulations and in comparative measurements in volunteers. GRE acquisitions with flow-compensating gradients are robust techniques for myocardial tagging acquisitions. Use of optimized flip angles and saturation pulses can significantly improve delineation of the tag and can be used up to at least 700 ms after the R-wave. Therefore, LV tagging with GRE acquisitions using optimized MR parameters is a robust and promising technique.

PURPOSE: To characterize the magnetic resonance (MR) imaging appearance of two anterosuperior labral variants, the sublabral foramen (SLF) and the Buford complex. MATERIALS AND METHODS: The axial gradient-recalled-echo (GRE) MR images and the fat-suppressed, T2-weighted, fast spin-echo (SE) images were reviewed in 19 patients with arthroscopically proved SLF and 11 patients with a Buford complex. The anterosuperior labrum was graded as normal, detached, or absent on the images. RESULTS: For the patients with an SLF, the anterosuperior labrum was graded as detached in all patients who underwent fast SE imaging but in only 43% of patients who underwent GRE imaging. For the patients with a Buford complex, the anterosuperior labrum was graded as absent in only 30% of patients who underwent GRE imaging and in none of the patients who underwent fast SE imaging. CONCLUSION: Isolated MR abnormalities of the anterosuperior labrum may represent either of the two asymptomatic labral variants.

Because several studies have shown that conventional MR imaging can fail to diagnose a significant percentage of labral tears, some authors have proposed obtaining T2*-weighted gradient-recalled echo images with the humerus in external rotation. The purpose of our study was to determine whether the diagnostic accuracy of detecting anteroinferior labral tears by MR imaging would be improved by adding a T2*-weighted gradient-recalled echo sequence with the humerus in external rotation.The study included 24 patients for whom axial MR images of the shoulder were obtained with the humerus in both the neutral position and external rotation. Two observers interpreted the images made in the neutral position and then noted any change in their interpretations after viewing findings on the external-rotation images. MR results were correlated with surgical findings. At surgery, 14 anteroinferior labra were found to be torn and 10 were found to be intact.Both observers identified one patient for whom a surgically proved labral tear was seen only on the external-rotation images. The sensitivity increased from 0.43 to 0.50 (p = .35) for observer 1 and from 0.36 to 0.43 (p = .35) for observer 2. The specificity of 0.90 for both observers remained unchanged. The accuracy improved from 0.62 to 0.67 for observer 1 and from 0.55 to 0.62 for observer 2.The addition of external-rotation T2*-weighted gradient-recalled echo images to the MR examination for tears of the anteroinferior labrum leads to a small but statistically insignificant increase in diagnostic sensitivity. We conclude that the small increase in sensitivity does not justify the routine use of this sequence.

Gradient recalled echo planar imaging was used to monitor changes in myocardial and left ventricular chamber blood intensity during apnea in rats. Significant signal loss in both blood (to 62 +/- 5% and 51 +/- 6% of baseline) and myocardium (to 79 +/- 2% and 76 +/- 3% of baseline) was observed at 45 and 90 s apnea while O2 saturation decreased from 98 +/- 1% to 62 +/- 7% and 36 +/- 9%, respectively. These results show that myocardial intensity is modulated by alterations in blood oxygenation.

A method that improves contrast in gradient-recalled-echo magnetic resonance images is described. The increase in contrast is produced by applying low-power radio-frequency irradiation 5-10 kHz from the main water proton resonance frequency to excite macromolecular hydrogen-1 nuclei as part of a conventional gradient-recalled-echo sequence. The contrast so obtained is theoretically different from T1 or T2 contrast and has been termed magnetization transfer contrast. Cat head images were acquired in vivo with this method at 4.7 and 1.5 T. Compared with conventional gradient-recalled-echo images, the magnetization transfer images demonstrate increased contrast between many tissue pairs, such as between white matter and blood and between gray matter and cerebrospinal fluid. The dependence of the magnetization transfer effect on repetition time and preirradiation power were also studied.

Microbleeds (MBs) are thought to be clusters of hemosiderin-containing macrophages and are more commonly observed in hypertensive microangiopathy (lacunar infarct or intracerebral hemorrhage), cerebral amyloid angiopathy, or cerebral autosomal dominant arteriopathy with subcortical infarcts and

Background Periaqueductal gray (PAG) is a substantial descending pain modulatory center, and previous voxel-based morphometry study confirmed the clusters with increased volume in PAG region in medication-overuse headache (MOH). The aim of this study is to investigate altered PAG volume in MOH using an automated PAG segment method to measure the true PAG volume. Methods High resolution three-dimensional T1-weighted fast spoiled gradient recalled echo MR images were obtained from 22 patients with MOH and 22 normal controls (NC). PAG template was created based on ICBM 152 gray template, and the individual PAG was generated by applying the deformation field from structural image segment to the PAG template, and individual PAG volume was calculated. Results There was a significant increased volume of PAG in MOH (0.366 ± 0.005 ml) than that in NC (0.341 ± 0.005 ml)(P 0.05). The area of receiver operating characteristic (ROC) curve was 0.845, and the cut-off of PAG volume was 0.341 ml with sensitivity 95.5% and specificity 63.6%. Conclusion The present study demonstrated that the PAG volume gain was confirmed in MOH patients, and the automated individual PAG volume measure may be considered as a simple and effective imaging biomarker in MOH diagnosis.