Gradient-recalled Acquisition In The Steady State Research Articles

T175. A 10-YEAR LONGITUDINAL STUDY OF GREY MATTER VOLUME IN FIRST EPISODE OF NON-AFFECTIVE PSYCHOSIS

BackgroundStructural abnormalities in First Episode of Non- Affective Psychosis (FEP) are shown to be present at the time of onset of the illness. Although there are multiple cross-sectional studies in chronic patients there is no clear evidence how these alterations progress years after the appearance of the first episode.MethodsData for the present investigation were obtained from an ongoing epidemiological and longitudinal intervention programme of first-episode psychosis (PAFIP) conducted at the Marqués de Valdecilla University Hospital (HUMV), Spain. Images for 62 FEP patients and 47 healthy controls were acquired at baseline and 10 year follow-up on the same 1.5-T whole-body scanner (SIGNA, GE, Milwaukee, WS, USA). Three-dimensional T1-weighted images, using a spoiled gradient-recalled acquisition in the steady state (GRASS) (SPGR) sequence, were acquired in the coronal plane with the following parameters: TE=5 msec, TR =24 msec, NEX=2, rotation angle =45°, FOV= 26 x 19.5 cm, slice thickness =1.5 mm and a matrix of 256 x 192.Structural imaging data for each subject was analyzed using serial longitudinal Statistical Parametric Mapping software (SPM12). After segmenting the mid-point average and multiply the result by the jacobian maps, DARTEL was applied to spatially normalise de diferences. T-test between both groups was performed, allowing voxel-wise comparison of progressive structural change. All results were p<0.05 FWE corrected.ResultsFEP patients exhibited progressive bilateral atrophy of the anterior cingulate bilaterally, the right inferior orbital, middle and superior frontal giri, left precentral and postcentral giri and cerebellum. We found no areas were grey matter was greater in controls than in patients.DiscussionIn this study we analyze a well characterized sample of patients with a first episode of non-affective psychosis in the first weeks after onset and 10 years later. Our results confirm that, apart from the grey matter volume reduction presented at baseline, patients show a progressive grey matter loss in anterior cingulate, frontal and parietal lobes as well as cerebellum.

Muscle Fat Fraction in Neuromuscular Disorders: Dual-Echo Dual-Flip-Angle Spoiled Gradient-Recalled MR Imaging Technique for Quantification—A Feasibility Study

To prospectively evaluate the muscle fat fraction (MFF) measured with dual-echo dual-flip-angle spoiled gradient-recalled acquisition in the steady state (SPGR) magnetic resonance (MR) imaging technique by using muscle biopsy as the reference standard. After ethics approval, written informed consent from all patients was obtained. Twenty-seven consecutive patients, evaluated at the Neuromuscular Disorders Center with a possible diagnosis of neuromuscular disorder, were prospectively studied with MR imaging of the lower extremities to quantify muscle fatty infiltration by means of MFF calculation. Spin-density- and T1-weighted fast SPGR in-phase and opposed-phase dual-echo sequences were performed, respectively, with 20° and 80° flip angles. Round regions of interest were drawn by consensus on selected MR sections corresponding to anticipated biopsy sites. These were marked on the patient's skin with a pen by using the infrared spider light of the system, and subsequent muscle biopsy was performed. MR images with regions of interest were stored on a secondary console where the MFF calculation was performed by another radiologist blinded to the biopsy results. MFFs calculated with dual-echo dual-flip-angle SPGR MR imaging and biopsy were compared by using a paired t test, Pearson correlation coefficient, and Bland-Altman plots. P value of < .05 was considered to indicate a statistically significant difference. The mean MFFs obtained with dual-echo dual-flip-angle SPGR MR imaging and biopsy were 20.3% (range, 1.7%-45.1%) and 20.6% (range, 3%-46.1%), respectively. The mean difference, standard deviation of the difference, and t value were -0.3, 1.3, and -1.3 (P > .2), respectively. The Pearson correlation coefficient was 0.995; with the Bland-Altman method, all data points were within the ± 2 SDs limits of agreement. The results show that dual-echo dual-flip-angle SPGR MR imaging technique provides reliable calculation of MFF, consistent with biopsy measurements.

Delayed Gadolinium-enhanced MR Imaging of Articular Cartilage: Three-dimensional T1 Mapping with Variable Flip Angles and B1Correction

To develop and verify the accuracy of a rapid imaging protocol for delayed gadolinium-enhanced magnetic resonance (MR) imaging of cartilage that was based on three-dimensional (3D) spoiled gradient-recalled acquisition in the steady state (SPGR) sequences with variable flip angles (FAs) (VFAs) and where a correction method for B(1) field inhomogeneities was applied. The institutional research ethics board approved this study. Written informed consent was obtained from all subjects. A B(1) field inhomogeneity correction method was applied to a 3D SPGR pulse sequence with VFAs (repetition time msec/echo time msec, 7.1/3.3; FAs, 2 degrees , 5 degrees , 10 degrees , and 20 degrees ) and was used to perform delayed gadolinium-enhanced MR imaging of cartilage 3D T1 measurements at 1.5 T. The 3D T1 measurements were validated with the reference standard (the results of T1 mapping by using a single-section two-dimensional [2D] inversion-recovery [IR] fast spin-echo [SE] pulse sequence in vitro and in vivo) in six healthy volunteers. T1 values calculated from 3D T1 maps were not significantly different from reference T1 values in vitro (P = .195) and in vivo (P = .52) when a B(1) field inhomogeneity correction method was applied. In vivo T1 mapping of the articular surface of the whole femoropatellar joint, including data acquisition, was performed in approximately 8 minutes of acquisition time at a spatial resolution of 0.55 x 0.55 x 3.00 mm. Rapid T1 mapping by using 3D SPGR acquisitions with a VFA approach and a correction for B(1) field inhomogeneities can be used for delayed gadolinium-enhanced MR imaging of cartilage. T1 measurements performed in vitro and in vivo by using this approach are highly accurate when compared with those performed by using standard 2D IR fast SE T1 mapping as a reference.

Ankle MRI for Anterolateral Soft Tissue Impingement: Increased Accuracy with the Use of Contrast-Enhanced Fat-Suppressed 3D-FSPGR MRI

ObjectiveTo validate the use of contrast-enhanced (CE) fat-suppressed three-dimensional (3D) fast gradient-recalled acquisition in the steady state with radiofrequency spoiling (FSPGR) magnetic resonance imaging (MRI) for the diagnosis of anterolateral soft tissue impingement of the ankle, as compared to the use of routine ankle MRI.Materials and MethodsContrast-enhanced fat-suppressed 3D-FSPGR MRI and routine MRI scans were retrospectively reviewed for 45 patients with arthroscopically proven anterolateral impingement. In addition, scans were reviewed in 45 control subjects with diagnoses other than impingement. Two radiologists independently reviewed the two sets of images in random order. Using areas (Az) under the receiver operating characteristic curve (ROC), we compared the depiction of anterolateral soft tissue impingement in the two sets of images.ResultsThe overall accuracy for lesion characterization was significantly higher (p < 0.05) using the CE fat-suppressed 3D-FSPGR MR images (Az = 0.892 and 0.881 for reader 1 and 2, respectively) than using the routine MR images (Az = 0.763 and 0.745). The use of CE fat-suppressed 3D-FSPGR MRI enhanced impingement depiction in most cases. However, in cases with a thickened non-enhancing scar or joint effusion, the routine images better depicted a soft tissue mass that intruded into anterolateral gutter than the CE images.ConclusionThe use of CE fat-suppressed 3D-FSPGR MRI of the ankle allows a more accurate assessment of anterolateral soft tissue impingement of the ankle, as compared to the use of routine MRI.

Venous Anatomy of the Sphenoparietal Sinus: Evaluation by MR Imaging

The termination of the superficial middle cerebral vein (SMCV) has been described as entering or being partially equivalent to the venous sinus coursing under the lesser sphenoid wing, which has classically been called the sphenoparietal sinus. However, the recent literature reports that the SMCV is not connected to the sphenoparietal sinus. In this study, the venous anatomy was evaluated to clarify the anatomy of the sphenoparietal sinus and the termination of the SMCV. Magnetic resonance imaging (MRI) was performed on 1.5-T superconductive units using a three-dimensional fast spoiled gradientrecalled acquisition in the steady state (3-D fast SPGR) sequence with fat suppression in a total of 48 sides of 24 patients. Coronal source images and reconstructed axial images were displayed on the Advantage Window Console, and connections to the cavernous sinus were then evaluated for the venous sinus coursing under the lesser sphenoid wing (hereafter called the sinus of the lesser sphenoid wing), the middle meningeal vein, and the SMCV. The following findings were observed bilaterally in all patients. The sinus of the lesser sphenoid wing was connected medially with the cavernous sinus and laterally with the anterior branch of the middle meningeal vein near the pterion. The anterior branch of the middle meningeal vein entered the bony canal laterally above the junction with the sinus of the lesser sphenoid wing and coursed along the inner table of the skull or emerged into the diploic vein, indicating its parietal portion. Although the termination of the SMCV had several patterns, the SMCV was not connected with the sinus of the lesser sphenoid wing in any of the patients. The sphenoparietal sinus is considered to consist of the sinus of the lesser sphenoid wing and the parietal portion of the anterior branch of the middle meningeal vein; these were identified as venous structures distinct to the SMCV.

Chronic Tibiofibular Syndesmosis Injury of Ankle: Evaluation with Contrast-enhanced Fat-suppressed 3D Fast Spoiled Gradient-recalled Acquisition in the Steady State MR Imaging

To retrospectively determine the accuracy of coronal contrast material-enhanced fat-suppressed three-dimensional (3D) fast spoiled gradient-recalled acquisition in the steady state (SPGR) magnetic resonance (MR) imaging, as compared with that of routine transverse MR imaging, in the assessment of distal tibiofibular syndesmosis injury, with arthroscopy as the reference standard. The review board of the College of Medicine in Yonsei University approved this study; informed consent was waived. The study group comprised 45 patients (26 men, 19 women; mean age, 32.1 years; range, 18-58 years) with a chronic ankle injury who had undergone MR imaging and arthroscopic surgery. Three independent readers retrospectively reviewed the two sets of MR images (one set of gadolinium-enhanced 3D fast SPGR images and one set of routine T1-, T2-, and intermediate-weighted images). Scores from 1 to 5 in increasing order of the probability of injury were assigned to both sets. Arthroscopy was the reference standard. Syndesmotic recess height was measured on contrast-enhanced images. The two sets of images were compared for diagnostic performance with receiver operating characteristic (ROC) analysis. Dissection and histologic examination of six cadaveric ankles was performed to assess the syndesmotic area and ascertain the enhancing structure at MR imaging. At arthroscopy, syndesmotic injury was found in 24 ankles but not in 21 ankles. Areas under the ROC curve were significantly higher for the contrast-enhanced images (P<.05). The contrast-enhanced set showed higher accuracy, sensitivity, and specificity compared with the routine set for the assessment of syndesmosis injury. Mean syndesmotic recess height was significantly greater (P<.05) in patients with syndesmotic injury. Dissection and histologic examination revealed a highly vascular synovial fold in the syndesmotic area that is expected to enhance at MR imaging. In the assessment of chronic syndesmosis injury, coronal gadolinium-enhanced fat-suppressed 3D fast SPGR MR images were more sensitive, specific, and accurate than routine MR images.

Volumetric Cartilage Measurements of Porcine Knee at 1.5-T and 3.0-T MR Imaging: Evaluation of Precision and Accuracy

To compare the precision and accuracy of 3.0-T and 1.5-T magnetic resonance (MR) imaging in the quantification of cartilage volume by using direct volumetric measurements as a reference standard. The local animal experimentation committee did not require its approval for this study. Porcine knees were obtained from an abattoir. These specimens were used to optimize imaging parameters regarding effective signal-to-noise ratio (SNRE) and contrast-to-noise ratio (CNRE) for a fat-saturated spoiled gradient-recalled acquisition in the steady state (SPGR) sequence, a water excitation SPGR sequence, and a fast spin-echo sequence at 3.0 T and a fat-saturated SPGR sequence at 1.5 T. By using the optimized sequences, 18 specimens were imaged in less than 6 minutes per sequence. A fivefold repetition of measurements of four specimens was performed for precision analysis. Cartilage was segmented by using semiautomatic software to calculate the volume. After imaging, the cartilage was scraped off and the volume was measured directly by using a saline-displacement method to calculate accuracy. Precision and accuracy errors were calculated as the root-mean-squares of the single errors per specimen. SNRE and CNRE values, respectively, were highest for the water excitation sequence at 3.0 T (1.81 sec(-1/2) and 1.27 sec(-1/2)), followed by the fat-saturated SPGR sequence (1.52 sec(-1/2) and 1.07 sec(-1/2)). The fast spin-echo sequence and the fat-saturated SPGR sequence at 1.5 T had lower SNR(E) (1.27 sec(-1/2) and 0.59 sec(-1/2), respectively). Accuracy error for MR-based volume calculation at the femur was 5.0%, 3.0%, 21%, and 16% for the water excitation, fat-saturated SPGR, and fast spin-echo sequences at 3.0 T and the fat-saturated SPGR sequence at 1.5 T, respectively. MR imaging at 3.0 T was shown in our study to better quantify cartilage volume. SNRE and CNRE were substantially improved, resulting in significantly higher accuracy in determining cartilage volume.

Detection of hepatic VX2 carcinomas with ferucarbotran-enhanced magnetic resonance imaging in rabbits: Comparison of nine pulse sequences

Objective To compare the diagnostic performance of a variety of magnetic resonance imaging (MRI) sequences, in order to identify the most effective ferucarbotran-enhanced sequence for the detection of multiple small hepatic VX2 carcinomas in rabbits. Methods Fifteen rabbits with experimentally induced 135 VX2 carcinomas in the liver underwent ferucarbotran-enhanced MRI using the following nine pulse sequences: a fat-suppressed fast spin-echo (FSE) sequence with two echo times (TE) (proton density- and T2-weighted images), four different T2 *-weighted fast multiplanar GRASS (gradient-recalled acquisition in the steady state) (FMPGR) with the combination of three TEs (9, 12, 15 ms, respectively) and two flip angles (20°, 80°, respectively), T2 *-weighted fast multiplanar spoiled GRASS (FMPSPGR), T1-weighted FMPSPGR, and dynamic T1-weighted FMPSPGR. All images were reviewed by three radiologists with quantitative and qualitative analysis. Results Tumor-to-liver contrast-to-noise ratio of the proton density-weighted FSE sequence was significantly higher than those of the others ( p < 0.05). The lesion conspicuities of proton density- and T2-weighted FSE and T2 *-weighted FMPGR (TE/flip angle, 9/20° and 12/20°) images were better and the image artifacts of T2 *-weighted FMPGR (TE/flip angle, 15/20° and 12/80°) and T2 *-weighted FMPSPGR images were more prominent than those of the others ( p < 0.05). The lesion detection in T2- and proton density-weighted FSE and T2 *-weighted FMPGR (TE/flip angle, 12/20°) images were superior to those of the others and for the detection of very small hepatic tumors of less than 5 mm, the sensitivities of these sequences were less than 30%. Conclusion Ferucarbotran-enhanced T2- and proton density-weighted FSE and T2 *-weighed FMPGR (TE/flip angle, 12/20°) images were found to be the most effective pulse sequences for the detection of multiple small hepatic VX2 carcinomas but these sequences were limited in the detection of very small hepatic tumors of less than 5 mm in size.

Articular Cartilage of the Knee: Evaluation with Fluctuating Equilibrium MR Imaging—Initial Experience in Healthy Volunteers

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study, whose purpose was to prospectively compare three magnetic resonance (MR) imaging techniques-fluctuating equilibrium, three-dimensional (3D) spoiled gradient-recalled acquisition in the steady state (SPGR), and two-dimensional (2D) fast spin echo (SE)-for evaluating articular cartilage in the knee. The study cohort consisted of 10 healthy volunteers (four men, six women; age range, 26-42 years). Cartilage signal-to-noise ratio (SNR), SNR efficiency, cartilage-fluid contrast-to-noise ratio (CNR), CNR efficiency, image quality, cartilage visibility, and fat suppression were compared. Cartilage volume was compared for the fluctuating equilibrium and 3D SPGR techniques. Compared with 3D SPGR and 2D fast SE, fluctuating equilibrium yielded the highest cartilage SNR efficiency and cartilage-fluid CNR efficiency (P < .01 for both). Image quality was similar with all sequences. Fluctuating equilibrium imaging yielded higher cartilage visibility than did 2D fast SE imaging (P <. 01) but worse fat suppression than did 3D SPGR and 2D fast SE imaging (P < .04). Cartilage volume measurements with fluctuating equilibrium and 3D SPGR were similar. Fluctuating equilibrium MR imaging is a promising method for evaluating articular cartilage in the knee.

Percutaneous MR Imaging–guided Transvascular Access of Mesenteric Venous System: Study in Swine Model

To determine if, with use of magnetic resonance (MR) imaging guidance alone, transcaval puncture of the superior mesenteric vein (SMV) and/or portal vein is feasible with a percutaneous femoral vein approach. The Institutional Animal Care and Use Committee approved the animal studies. Ten inferior vena cava (IVC)-SMV punctures were performed in six pigs. An active MR intravascular needle system was used for all transvascular punctures, and all procedures were performed with a 1.5-T MR unit. The needle was introduced via a 12-F femoral vein sheath and advanced into the IVC by using a real-time gradient-recalled-echo sequence (3.4/1.2 [repetition time msec/echo time msec], 45 degrees flip angle, and six to eight frames per second). Fast transverse spoiled gradient-recalled acquisition in the steady state (SPGR) (6.0/1.5, 60 degrees flip angle, one frame per second) was performed to confirm needle trajectory. The needle system was advanced under real-time MR imaging to puncture the SMV. The location of the needle tip was confirmed with a fast spin-echo sequence (1904/4.5, 36-cm field of view). A direct MR portogram was obtained after the administration of gadopentetate dimeglumine at a concentration of 25% with fast SPGR (6/1.3, 90 degrees flip angle, no section selection, three frames per second). Success was defined as entry into the mesenteric venous system without traversal of any retroperitoneal organs or adjacent vasculature. Successful MR imaging-guided IVC-SMV punctures were performed in all 10 procedures (100%). The needle was fully visualized as it traversed the retroperitoneum and entered the SMV. MR portograms were successfully obtained following all punctures through the needle. Conventional transverse MR imaging helped confirm that the needle did not traverse any retroperitoneal organs or vessels. With use of only MR imaging guidance and an active MR imaging intravascular needle system, the authors were able to successfully puncture the SMV from the IVC with direct visualization of the needle and all retroperitoneal structures.

Visualization of Spinal Cord Motion Associated With the Cardiac Pulse by Tagged Magnetic Resonance Imaging With Particle Image Velocimetry Software

The purpose of this study was to evaluate whether or not tagged magnetic resonance (MR) imaging with particle image velocimetry (PIV) software could reveal spinal cord motion clearly. Six volunteers were enrolled in this study. Tagged MR imaging using fast spoiled gradient-recalled acquisition in the steady state with spatial modulation of the magnetization technique was performed using a 1.5-T MR system. Sagittal vector maps analyzed by PIV software revealed entire spinal cord motion sequentially during the cardiac cycle. The cervical spinal cord initially moved in a caudal direction and then continually oscillated from a cephalic-to-caudal direction. Each volunteer had a different cycle. In the thoracic spinal area, similar findings were observed, although they were slightly less clear than in the cervical area. Tagged MR imaging combined with PIV software, referred to as tagged MR image velocimetry, revealed spinal cord motion associated with the cardiac pulse, especially in the cervical spine.

Usefulness of Preoperative Detection of Artery of Adamkiewicz with Dynamic Contrast-enhanced MR Angiography

To prospectively evaluate the detection of the artery of Adamkiewicz at magnetic resonance (MR) angiography and the effect such detection has on outcome after surgical graft placement in a series of patients with thoracoabdominal aortic disease. This study had ethics committee approval, and written informed consent was obtained from all patients. Fifty patients (38 men, 12 women; age range, 47-83 years; mean age, 67.2 years) who were scheduled to undergo thoracoabdominal aortic surgery for treatment of thoracoabdominal aortic aneurysm (n = 42) or thoracoabdominal aortic dissection (n = 8) were enrolled in the study. MR angiography was performed with a 1.5-T system by using dynamic three-dimensional fast spoiled gradient-recalled acquisition in the steady state with a bolus of contrast material and saline injection (4 mL/sec). Differences in the cross-clamping time, bypass time, total surgery time, and spinal complication rate between patients in whom the artery of Adamkiewicz was identified (group A) and those in whom the artery was not identified (group B) were evaluated with chi(2) or Mann-Whitney U testing. In 42 of the 50 patients (84% [group A]), at least one artery of Adamkiewicz was seen to arise from an intercostal artery. Two arteries of Adamkiewicz were identified in four of the patients (8%). The artery of Adamkiewicz could not be detected with MR angiography in eight patients (group B). The ranges of cross-clamping, bypass, and total surgery times, respectively, were 30-199 minutes (mean, 78.4 minutes +/- 39.1 [standard deviation]), 30-298 minutes (mean, 96.9 minutes +/- 60.0), and 135-665 minutes (mean, 354.9 minutes +/- 133.9) in group A and 53-124 minutes (mean, 72.8 minutes +/- 29.8), 10-124 minutes (mean, 66.0 minutes +/- 41.0), and 220-405 minutes (mean, 315.6 minutes +/- 68.8) in group B. Spinal complications occurred in two patients in group B but in none of the patients in group A (P < .001). The artery of Adamkiewicz was detected in a large percentage of patients in whom there were no spinal complications, unlike the spinal complications that occurred in the patients in whom the artery was not detected.

Craniocervical junction venous anatomy around the suboccipital cavernous sinus: evaluation by MR imaging

The present study evaluated the venous anatomy of the craniocervical junction, focusing on the suboccipital cavernous sinus (SCS), a vertebral venous plexus surrounding the horizontal portion of the vertebral artery at the skull base. MR imaging was reviewed to clarify the venous anatomy of the SCS in 33 patients. Multiplanar reconstruction MR images were obtained using contrast-enhanced three-dimensional fast spoiled gradient-recalled acquisition in the steady state (3-D fast SPGR) with fat suppression. Connections with the SCS were evaluated for the following venous structures: anterior condylar vein (ACV); posterior condylar vein (PCV); lateral condylar vein (LCV); vertebral artery venous plexus (VAVP); and anterior internal vertebral venous plexus (AVVP). The SCS connected with the ACV superomedially, with the VAVP inferolaterally, and with the AVVP medially. The LCV connected with the external orifice of the ACV and superoanterior aspect of the SCS. The PCV connected with the posteromedial aspect of the jugular bulb and superoposterior aspect of the SCS. The findings of craniocervical junction venography performed in eight patients corresponded with those on MR imaging, other than with regard to the PCV. Contrast-enhanced 3-D fast SPGR allows visualization of the detailed anatomy of these venous structures, and this technique facilitates interventions and description of pathologies occurring in this area.

High-resolution magnetic resonance of the extracranial facial nerve and parotid duct: demonstration of the branches of the intraparotid facial nerve and its relation to parotid tumours by MRI with a surface coil

To investigate the usefulness of high-resolution MR imaging in the evaluation of the extracranial facial nerve, compared with surgical findings. Thirteen patients with benign parotid tumours were studied on a 1.5-T MR system with a 3 in circular surface coil. High-resolution T1-weighted spin-echo, T2-weighted fast spin-echo, and three-dimensional gradient-recalled acquisition in the steady state (GRASS) images were obtained in the axial planes. Oblique reformatted images were generated. Tumours, parotid ducts and facial nerves were identified on these images. The relationship of the tumours to the facial nerves was confirmed at surgery. Facial nerves appeared as linear structures of low intensity on all pulse sequences. The main trunks and cervicofacial and temporofacial divisions of the facial nerves were identified in 100%, 84.1% and 53.8% of GRASS images, respectively. Parotid ducts appeared as structures of low intensity on T1-weighted (66.6%) and GRASS images (81.8%), and as structures of very high intensity on T2-weighted images (91.7%). The relationships of the tumours to the facial nerves were correctly diagnosed in 11 (91.7%) of 12 cases. High-resolution MR imaging depicts the extracranial facial nerve and the parotid duct, and is useful for preoperative evaluation of parotid gland tumours.

Transvenous Embolization of Dural Arteriovenous Fistula of the Cavernous Sinus

We reviewed magnetic resonance (MR) images and digital subtraction angiograms (DSA) from eight patients with dural arteriovenous fistula of the cavernous sinus (DAVFCS) to clarify the fistulous points and to evaluate the venous access routes into the cavernous sinus for transvenous embolization (TVE). Multiplanar reconstruction of the MR images was achieved using three-dimensional fast spoiled gradient-recalled acquisition in the steady state (3-D fast SPGR) after the intravenous administration of gadopentetate dimeglumine (Gd-DTPA). TVE was performed using microcoils via the inferior petrosal sinus (IPS) using the transfemoral approach in five patients, via the facial vein and superior ophthalmic vein (SOV) using the transfemoral approach in 1 patient, and by SOV puncture in two patients. Most fistulas were detected in the posterior portion of the cavernous sinus or in the posterior intercavernous sinus in all of the patients. Fistulas identified as hyperintense dots or lines on contrast-enhanced 3-D fast SPGR images and were replaced with the microcoils. Target embolization of the fistulas was feasible in three patients treated via the SOV and in one patient treated via the IPS. Contrast- enhanced 3-D fast SPGR can help to identify the fistulous points of DAVFCS. Precise identification of fistulous points and selection of the adequate access route are mandatory for efficient TVE of DAVFCS.

Synovitis and soft tissue impingement of the ankle: assessment with enhanced three-dimensional FSPGR MR imaging.

To assess soft tissue impingement as well as synovitis of the ankle associated with trauma by using contrast-enhanced (CE), fat-suppressed, three-dimensional, fast gradient-recalled acquisition in the steady state with radiofrequency spoiling (FSPGR) magnetic resonance (MR) imaging. A total of 36 patients who had had chronic ankle pain associated with a traumatic injury undertook fat-suppressed CE three-dimensional FSPGR MR imaging and then arthroscopy of the ankle. The ankle joint was divided into four compartments by anatomic details: the anterolateral gutter, anteromedial gutter, anterior recess, and posterior recess. Synovial enhancement was graded as follows: grade I, no enhancement; grade II, linear enhancement; grade III, focal nodular enhancement; and grade IV, irregular nodular enhancement. MR grading of the synovial enhancement (synovitis, grade III or IV; soft tissue impingement, grade III or IV with its intrusion from the capsular reflection) was compared with arthroscopic findings. A control study of twenty asymptomatic ankles was done for determining enhancement. Arthroscopy confirmed synovitis in 47 compartments of 27 patients. Of the 27 patients, 15 revealed soft tissue impingement in 17 compartments. For the assessment of synovitis, fat-suppressed CE three-dimensional FSPGR MR imaging had an accuracy of 72.9%, sensitivity of 91.5%, and specificity of 63.9%; whereas for that of soft tissue impingement it had an accuracy of 94.4%, sensitivity of 76.5%, and specificity of 96.9%. All of the asymptomatic subjects showed grade I (81%) or II (19%) synovial enhancement. Fat-suppressed CE three-dimensional FSPGR MR imaging was sensitive for the evaluation of synovitis of the ankle associated with trauma, whereas it was specific for soft tissue impingement evaluation.

Evaluation of software for registration of contrast-enhanced brain MR images in patients with glioblastoma multiforme.

We evaluated commercially available software that rapidly and automatically registers brain MR images on a clinical workstation, and we studied the accuracy of these registrations. Ten patients with a diagnosis of glioblastoma multiforme underwent contrast-enhanced inversion recovery prepared three-dimensional (3D) volumetric spoiled gradient-recalled acquisition in the steady state (SPGR) MR imaging (contiguous 1.5-mm slice thickness, 96-104 slices). After this imaging sequence, each patient was brought out of the head coil into a sitting position and then repositioned in the coil. The inversion recovery prepared 3D SPGR sequence was then repeated. A commercially available software program operating on a clinical workstation was used to automatically register the second inversion recovery prepared SPGR series to the first. The speed of registration was recorded. The accuracy of each registration was estimated by recording the coordinates of eight anatomic landmarks on the registered and reference series and by calculating the mean error among matching landmarks. In nine of 10 patients, the registration software produced a visually satisfactory registration. In one patient, a second registration was necessary to produce a satisfactory registration. The processing time for each iteration was 48.3 +/- 3.8 sec (mean +/- SD). The mean error in aligning matching anatomic landmarks ranged from 0.67 to 1.41 mm, with an overall mean of 1.18 mm. The largest error among matching landmarks was 2.3 mm. Commercially available registration software can automatically register 3D imaging volumes in less than 1 min. The mean error in registration was approximately equivalent to the dimensions of a single voxel.

Optimal pulse sequence for ferumoxides-enhanced MR imaging used in the detection of hepatocellular carcinoma: a comparative study using seven pulse sequences.

ObjectiveTo identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs).Materials and MethodsSixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 µmol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333 8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TR∞/TE39 and 98), T2*-weighted gradient-recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis.ResultsQuantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others.ConclusionT2*-weighted FMPGR, T2*-weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxides-enhanced MR imaging in the detection of HCCs.

Electrophysiological modeling of cardiac ventricular function: from cell to organ.

Three topics of importance to modeling the integrative function of the heart are reviewed. The first is modeling of the ventricular myocyte. Emphasis is placed on excitation-contraction coupling and intracellular Ca2+ handling, and the interpretation of experimental data regarding interval-force relationships. Second, data on use of diffusion tensor magnetic resonance (DTMR) imaging for measuring the anatomical structure of the cardiac ventricles are presented. A method for the semi-automated reconstruction of the ventricles using a combination of gradient recalled acquisition in the steady state (GRASS) and DTMR images is described. Third, we describe how these anatomically and biophysically based models of the cardiac ventricles can be implemented on parallel computers.

A three-dimensional gadolinium-enhanced MR venography technique for imaging central veins.

We evaluated the use of a three-dimensional gadolinium-enhanced MR venography technique in selected patients with suspected central venous abnormalities. Thirty-seven patients with suspected thrombosis, stenosis, occlusion, or compression of the axillary vein, subclavian vein, brachiocephalic vein, or superior or inferior vena cava or with suspected malfunction of central venous catheters were imaged. For all patients, we obtained a three-dimensional dynamic gadolinium-enhanced (bolus injection, 30 40 ml) breath-hold spoiled gradient-recalled acquisition in the steady state as well as conventional venous images from either Doppler sonography, CT, or digital subtraction venography. Breathhold fast multiplanar spoiled gradient-recalled acquisitions in the steady state were obtained using the following parameters: TR/TE, 10.3/1.9; flip angle, 45 degrees; matrix size, 256 x 128; number of excitations, one; field of view, 36-48 cm; number of partitions, 28; and slice thickness, 2.54 mm. MR venograms and conventional images were interpreted by two observers in consensus who were unaware of clinical information and the diagnosis. MR venograms were of diagnostic quality for all 37 patients. Thirteen patients had normal venous systems seen on both conventional and MR images. MR venography showed all nine venous stenoses, the one pericatheter fibrin sheath, and the one jugular vein thrombosis. Axillary or subclavian vein thrombosis was correctly diagnosed with MR venography in all four patients with this condition. Mediastinal venous compression was accurately depicted by MR venography in the five patients who had such compression. Finally, MR venography revealed the correct diagnosis in the three patients with inferior vena cava thrombus and tumor and the one patient with inferior vena cava compression. Thus, MR venography was 100% sensitive, specific, and accurate in the diagnosis of abnormalities affecting large central veins. Compared with conventional imaging, gadolinium-enhanced breathhold MR venography is easy to perform, well tolerated, and highly accurate in depicting central venous abnormalities.