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In the first decade of the twenty-first century, whole-body magnetic resonance scanners with high field strengths (and thus potentially better signal-to-noise ratios) were developed. At the same time, parallel imaging and “echo-sharing” techniques were refined to allow for increasingly high spatial and temporal resolution in dynamic magnetic resonance angiography (“time-resolved” = TR-MRA). This technological progress facilitated tracking the passage of intra-venously administered contrast agent boluses as well as the acquisition of volume data sets at high image refresh rates (“4D-MRA”). This opened doors for many new applications in non-invasive vascular imaging, including simultaneous anatomic and functional analysis of many vascular pathologies including arterio-venous malformations. Different methods were established to acquire 4D-MRA using various strategies to acquire k-space trajectories over time in order to optimize imaging according to clinical needs. These include “keyhole”-based techniques (e. g. 4D-TRAK), TRICKS – both with and without projection – and HYPR-reconstruction, TREAT, and TWIST. Some of these techniques were first introduced in the 1980 s and 1990 s, were later enhanced and modified, and finally implemented in the products of major vendors. In the last decade, a large number of studies on the clinical applications of TR-MRA was published. This manuscript provides an overview of the development of TR-MRA methods and the 4D-MRA techniques as they are currently used in the diagnosis, treatment and follow-up of vascular diseases in various parts of the body. Key statements • 4D-MRA, which differs according to manufacturer, generates high temporal and spatial resolution MRA volume data sets. Key differences in 4D-MRA techniques concern the sequence of the acquisition of k-space portions. • Central k-space portions define image contrast and are thus repetitively scanned with 4D-MRA. • Numerous clinical applications of 4D-MRA are already documented in the literature. Citation Format: • Hadizadeh DR., Marx C, Gieseke J et al. High temporal and high spatial resolution MR angiography (4D-MRA). Fortschr Rontgenstr 2014; 186: 847 – 859

PURPOSE Development of an MR-based imaging technique for the spine allowing reduction of frequency of conventional Nadiographs in the monitoring of juvenile scoliosis. PATIENTS AND METHODS 25 patients between the ages of 6 to 36 years were examined in supine position. Two examinations of the cervical and upper thoracic spine and of the lower thoracic and lumbar spine were performed with a 1.5 T Gyroscan ACS-NT Powertrak 6000 system with body coil employing 3D EPI-sequence (TR 17 ms, TE 9 ms, flip angle 20 degrees, field of view 450 mm) or 3D FFE sequences (TR 9 ms, TE 4.5 ms, flip angle 20 degrees, field of view 450 mm) and pulse-oximetry gating. 64 coronal slices were acquired with reconstructed slice thickness of 2 mm. Image processing was performed with an algorithm merging acquisition results into two single images in the coronal and sagittal orientations allowing measurement of the Cobb angle. RESULTS Mean examination time was 14 minutes per patient. Mean data processing time was seven minutes. Interobserver variance of determination of the Cobb angle was 1.8 degrees. CONCLUSIONS It is to be hoped that MR whole spine projection will allow a reduction of the frequency of conventional projection in the monitoring of juvenile scoliosis.

PURPOSE Analysis of temporal changes of ADC values at different stages after stroke. MATERIALS AND METHODS The original images of all scans were evaluated and a region of interest analysis was performed on ADC (apparent diffusion coefficient) maps. 92 patients with symptoms of ischemic stroke were examined at 1.5 Tesla (ACS-NT, Philips Medical Systems). The study protocol included a navigated multishot SE-EPI DWI (b = 0, 189, 750 s/mm-2, TE = 120/140 ms, delta/delta = 49/60 ms), a GraSE (TR/TE = 3500/90 ms) and a FLAIR-TSE (TR/TE/TI = 6000/150/2000 ms) sequence. 8 patients had regular follow-ups. All patients had an additional CT scan. RESULTS In hyperacute stroke ( 3 weeks, n = 20). The combined use of DWI and conventional MRI improved the diagnostic information in 16% of all MR examination beyond the hyperacute assessment. CONCLUSION By means of the ADC-values the age of stroke can be determined. Infarcts at different stages can be readily diagnosed with the combined use of DWI, FLAIR-TSE and GraSE. Pitfalls of DWI and conventional imaging can be avoided.

BACKGROUND AND PURPOSE: Anterior choroidal artery (AchoA) stroke often evolves into undulating hemipareses, which sometimes progress to high-grade hemiparesis or hemiplegia but may also completely regress. Spatial relationships of AchoA infarcts to corticospinal tracts (CSTs) and CST integrity were investigated with diffusion tensor imaging (DTI) to identify prognostic parameters related to diffusion anisotropy changes in AchoA stroke. MATERIALS AND METHODS: Twenty-five AchoA stroke patients were prospectively examined with 3T DTI and diffusion tensor tractography (DTT) within a 3-day mean interval after onset. Analysis included the following: 1) stroke size on diffusion-weighted imaging; 2) fractional anisotropy (FA) and apparent diffusion coefficients at the largest stroke extents versus contralateral homologous structures; 3) lesion location related to CST (“involvement”); 4) amount of fiber trajectories of affected versus nonaffected CST (“fiber ratio”); and 5) presence of ipsilateral fiber disruption. Imaging findings were related to clinical status 3 months after symptom onset with respect to favorable, moderate, or unfavorable motor outcome. RESULTS: FA differences (due to FA reduction in the affected versus nonaffected hemisphere) were significantly higher for patients with unfavorable outcome (P=.03). Patients with favorable outcome had nearly symmetrical FA. CSTs were involved in ischemic lesions in all but 2 patients (complete involvement, n=3; partial, n=20). Two CSTs were completely disrupted, and both patients were hemiplegic (no disruption, n=14; partial disruption, n=9). Fiber disruption and CST involvement correlated negatively with motor score after AchoA stroke (P < .01), whereas infarct size did not. CONCLUSION: DTT may explain resulting motor dysfunction in patients with AchoA infarcts with more notably decreased FA being an indicator for unfavorable outcome.

Background and Purpose— Concomitant disease of the supra-aortic arteries can influence the outcome of surgical treatment of carotid artery stenosis. However, sensitivity and specificity data of noninvasive contrast-enhanced 3-dimensional (3D) magnetic resonance angiography (CE MRA) for the detection of steno-occlusive disease of the entire supra-aortic arteries including the circle of Willis remain unclear. We aimed to intra-individually compare high-spatial-resolution CE 3D MRA and digital subtraction angiography (DSA) for the assessment of steno-occlusive vascular disease of the supra-aortic arteries. Methods— CE MRA and DSA of the supra-aortic arteries were prospectively performed in 50 consecutive patients. Intra-individual comparison of CE MRA and DSA was available in 833 arteries. High-spatial-resolution CE MRA comprised a measured voxel size of 0.81 mm × 0.81 mm × 1 mm (0.66 mm 3 ). Steno-occlusive vascular disease of the 833 arteries was assessed independently by 2 radiologists according to the NASCET criteria. Results— CE MRA had a sensitivity of 100% (73/73), a specificity of 99.3% (760/765), a positive predictive value of 93.6% (73/78), and a negative predictive value of 100% (760/760) by using a 70% to 99% threshold of arterial diameter stenosis. For detection of occlusion, sensitivity, specificity, PPV, and NPV value of CE MRA were 100%, respectively. Conclusions— Noninvasive high-spatial-resolution CE MRA is suited to replace diagnostic DSA for the detection of steno-occlusive disease of the supra-aortic arteries.

The purpose of this study was to evaluate the feasibility of high-field magnetic resonance imaging (MRI) of the lung using a T2-weighted fast-spin echo (TSE) sequence. Comparison was made with helical computed tomography CT findings in patients with diffuse pulmonary diseases. Prospective segment-wise analysis of high-field MR imaging findings in 15 patients with diffuse pulmonary diseases was made using helical CT and HRCT as the standard of reference. The MR studies were performed on a 3.0-T whole body system (Intera 3T, Philips Medical Systems) using a T2w TSE sequence with respiratory and cardiac gating (TE 80 ms TR 1,500-2,500 ms; turbo factor 17; 22 slices with 7/2-mm slice thickness and gap; 256x192 matrix). MR artifacts were graded on a three-point scale (low, moderate, high). Lung MR studies were prospectively analyzed segment-by-segment and diagnosed as healthy or pathological; results were compared with helical CT findings. In all 15 patients, MR imaging of the lung was successful. All 15 MR studies were compromised by artifacts; however, the severity of these artifacts was classified as low or moderate in 8/15, respectively, 7/15 cases. A total of 143/285 lung segments showed diffuse lung disease in helical CT. With MRI, 133 of these 143 segments (93%) were judged to be diseased. The ten segments that received false negative MR diagnoses displayed non-acute pulmonary lesions with inherently low proton density (scars, granulomas). MRI at 3.0 T can detect diffuse pulmonary disease with a high sensitivity. Based on this experience, further pulmonary studies with high-field systems appear justified and promising.

PURPOSE To evaluate a T2-weighted URSE sequence for the assessment of pulmonary infiltrations in comparison to CT. METHODS 28 MRT scans of 22 patients with confirmed pneumonia were recorded on a 1.5 Tesla apparatus with an expiratory and diastolic triggered, T2-weighted ultrafast-spin-echo sequence in axial slice mode with the following parameters: TReff/TE/Turbo-factor 2000-4000/90 ms/21-23; slice thickness/separation 6/0.6 mm; FOV 360 mm; 24 slices. 24 spiral CTs (since thickness/table advance: 1-2 mm/10mm) were available for comparison. The separate evaluation of MRTs and CTs was performed by three radiologists in a consensus procedure with regard to pulmonary lesions (e.g., infiltration, round foci, net patterns) and image quality of the MRTs (4-step scale). RESULTS In 71% of the cases the CTs and MRTs agreed with the diagnosis and representation of the lesions, in 25% MRT was superior. MRT was better for the detection of pulmonary abscesses. In 93% the image quality of the MRT was very good to good. CONCLUSIONS MRT in the technique presented here is in most cases equal to CT for the detection of pneumonia. Diagnosis of pulmonary abscesses seems to be better with MRT.

PURPOSE Evaluation of 3D-TSE MR-cholangiography with respiratory triggering in the work up of hepatopathies in infants and young children. PATIENTS AND METHOD 16 infants (4-16 years) with increased transaminases, two with recurrent pancreatitis, were examined at 1.5 T (ACS-NT II, Philips Medical Systems) using a 3D-TSE MRCP with respiratory triggering in addition to a regular MRI of the liver. The MRCP was compared to ERCP. Two radiologists and one gastroenterologist evaluated the technical quality, visualization of the pancreaticobiliary system, and the diagnostic value of the examinations. RESULTS Technically feasible were 14/16 MRCPs and 13/16 ERCPs. Two MRCP were not of diagnostic value due to motion artifacts and in three ERCP cannulation of the papilla was not possible. 14/16 ERCP required general anaesthesia, while MRCP needed i.v. sedation in two patients only. Extrahepatic ducts/cystic duct/pancreatic duct were visualized in 14/12/8 patients using MRCP, and in 13/10/3 patients using ERCP, both without adverse effects or complications. Intrahepatic ducts were better delineated with MRCP. In 10 patients with histologically proven periportal fibrosis (n = 7) and liver fibrosis (n = 1) or antineutrophil cytoplasmatic antibodies and associated inflammatory bowel disease, MRCP and ERCP revealed pathological results. CONCLUSION MRCP using a 3D-TSE sequence with respiratory triggering is a good non-invasive technique for delineation of the biliary tract in infants and young children for the work up to hepatopathies.

PURPOSE To compare spiral CT and MRT for the detection of focal pulmonary lesions. PATIENTS AND METHODS 50 patients with focal pulmonary lesions confirmed by spiral CT were examined using a T2-weighted UTSE sequence (TE: 90 ms, TR: 1500-3000 ms, echo interval 9 ms, 8 mm slice thickness, diastolic triggering, expiratory breath gating). Image quality was compared using a 4-stage scale. Lesions with a minimum size of 2 mm were counted and measured in the CT image. The results were compared with the MRT images. RESULTS The image quality in CT examinations with an average value of 1.22 better than that in MRT (1.78). In total 163 pulmonary lesions with a size of 2-115 mm were found by CT. MRT found 151/163 lesions (92.6%). Of the 12 lesions not detected, 9 were smaller than 4 mm, 1 corresponded to a 12 mm large, completely calcified granuloma. In 2 cases there was a 4 or 5 mm large unspecific scar. Thus, 160/163 (98.1%) of all lesions larger than 3 mm were detected. CONCLUSIONS MRT with use of a suitable UTSE sequence is an alternative to CT for the detection of focal pulmonary lesions with a size larger than 3 mm.

Purpose Development of a fast and reliable protocol for the detection and exclusion of abdominal venous thrombosis with an optimised T2-TSE- and 2D-TOF sequence. Material and method Evaluation of the flow-void phenomenon with a flow phantom on a 1.5 and 0.5 Tesla system using different echo times. Examination of 22 patients with suspected abdominal shunt- or abdominal vein-thrombosis with a optimum T2-TSE- and 2D-TOF sequence with a 1.5 or 0.5 Tesla system. Confirmation of thrombosis with contrast-enhanced computed tomography or digital subtraction angiography. Results The most effective combination of strong flow-void phenomena, signal/noise ratio and scan time was found with the following parameters: TE 120 ms, TR 2000 ms, 5 mm slice gap. In the patient group two complete and two partial thromboses were diagnosed with both sequences. One wrong positive thrombosis occurred in a stenotic anastomosis with the 2D-inflow sequence. Conclusion With optimum parameters the T2-TSE sequence produces a strong "flow-void" phenomenon suitable for "black-blood"-MRA. The use of this sequence alone or in combination with 2D-inflow MRA, if "bright-blood" MRA is recommended, allows a reliable evaluation of thrombosis in abdominal veins without high-tech MRA equipment and contrast media.

PURPOSE: Evaluation of a navigated multi-shot SE EPI sequence for routine clinical use in MR diffusion imaging. METHODS: We compared a multi-shot SE EPI sequence with the conventional SE sequence as well as with a single-shot SE EPI sequence on a standard 1.5 Tesla MR-scanner (ACS-NT, Philips Medical Systems) with a conventional gradient system (10 mT/m). Image quality and the reproducibility of the apparent diffusion coefficient were analysed with phantoms and with healthy volunteers. The diffusion coefficients of different brain areas were determined in a group of twenty volunteers. RESULTS: The multi-shot SE EPI sequence showed considerably shorter measurement times and smaller motion artifacts than the SE sequence and was less sensitive to susceptibility artifacts than the single-shot version. The reproducibility of the diffusion coefficients was better than 10%. CONCLUSION: The navigated multi-shot SE technique is more practicable and meaningful than the SE and the single-shot SE EPI techniques on a standard 1.5 Tesla MR-scanner with a conventional gradient system. In our opinion it is now the best method for diffusion imaging and should be preferred in clinical use. The determination of diffusion coefficients yields reliable results and characteristic values for different tissue can be obtained.

PURPOSE To evaluate the feasibility and the diagnostic efficacy of multislice diffusion-weighted and perfusion imaging in addition to FLAIR-TSE, T2w-GraSE and MR-angiography in the diagnosis of acute stroke. METHODS 18 patients with acute stroke were examined at 1.5 Tesla (Gyroscan ACS-NT, Philips Medical Systems) within 6 (n = 9) and 6-48 (n = 9) hours, respectively, and followed at regular intervals. For diffusion imaging we used a multislice multishot EPI-SE sequence with navigator echo correction and cardiac gating. Perfusion imaging was done by means of a FFE-EPI sequence after bolus injection of Gd-DTPA. RESULTS The diagnostic value of diffusion-weighted and perfusion imaging was significantly higher compared with FLAIR-TSE (p = 0.0023) and GraSE (p = 0.0012) during the first 6 hours. With FLAIR-TSE and GraSE first pathologic changes were seen after 4 hours. We detected perfusion deficit (rCBV < 10%) and a corresponding drop of the ADC in all infarcts larger than 1 cm in diameter. Within the area of low rCBV the combined analysis of diffusion and perfusion imaging allows to identify an infarct region with characteristics of a penumbra and one with characteristics of the infarct core. TTP was increased in the surrounding tissue. However, parts of this area were rarely included in the infarct. The final extension of the untreated infarct, as revealed by computed tomography, corresponded well to the perfusion deficit. CONCLUSIONS Early ischaemic cerebral infarcts can be diagnosed with diffusion and perfusion imaging before pathological changes are visualized with other imaging modalities. The combined use may allow to distinguish the infarct core from surrounding, potentially salvageable tissue.

The authors evaluate the value of two fast spin-echo sequences (FSE) with different T2-weighting (repetition time [TR]/echo time [TE] = 2000/90 mseconds and TR/TE = 2000/40 mseconds) and combined gradient-and-spin-echo sequences (TR/TE = 2000/90 mseconds) for contrast-enhanced liver imaging with superparamagnetic iron oxide (AMI-25).Forty-seven patients with focal liver lesions underwent magnetic resonance imaging at 1.0 tesla. AMI-25 was administered intravenously at a dose of 15 micromol iron/kg.Administration of AMI-25 resulted in a significant increase of lesion/liver contrast-to-noise ratio (C/N) for all T2-weighted sequences (P0.001). On the precontrast images, the FSE sequence with a TE of 90 mseconds had the highest C/N (16.0 +/- 4.5) whereas the best postcontrast C/N (27.9 +/- 7.6) was obtained with the mild T2-weighted FSE sequence with a TE of 40 mseconds.Fast spin-echo sequences are valuable sequences for imaging of the liver at 1.0 tesla. For AMI-25-enhanced magnetic resonance imaging, a mild T2-weighted FSE sequence is recommended.

Ziel: MRT-Untersuchungen galten bisher bei Patienten mit implantierten Herzschrittmachern als absolut kontraindiziert. In dieser prospektiven Studie wurde erstmals die Durchfuhrbarkeit einer MRT-Untersuchung bei modernen Schrittmachern in vitro und in vivo evaluiert. Methode: 14 Schrittmachermodelle in vitro sowie 18 Patienten mit implantierten Schrittmachern wurden an einem 0,5 Tesla MRT-System unter kontinuierlichem EKG-Monitoring mit in der Routinediagnostik ublichen Spin-, Turbo-Spin- und Gradienten-Echo (FFE)-Sequenzen untersucht. Vor und nach der MRT-Untersuchung erfolgte eine Schrittmacherkontrolle. Ergebnisse: Im statischen Magnetfeld kam es erwartungsgemas zu einer Aktivierung des Reed-Kontaktes mit festfrequenter Stimulation im asynchronen Modus. Drei in vitro untersuchte Schrittmachermodelle schalteten im statischen Magnetfeld wieder zuruck in den Demand-Modus und zeigten unter dem Einflus der gepulsten Magnetfelder intermittierende Inhibitionen und Triggerungen. Beeinflussung des Schrittmacherprogramms, Beschadigungen von Schrittmacherkomponenten, Dislokation des Schrittmacheraggregats sowie Induktion von Schrittmachertachykardien wurden weder in vitro noch in vivo beobachtet. Die atrialen und ventrikularen Reizschwellen blieben nach der MRT-Untersuchung unverandert. Schlusfolgerungen: Moderne Herzschrittmacher sind fur die Durchfuhrung einer MRT-Untersuchung bei 0,5 Tesla nicht mehr langer als eine grundsatzliche absolute Kontraindikation anzusehen. Kenntnisse uber das Verhalten des jeweiligen Schrittmachermodells in statischen und gepulsten Magnetfeldern und davon abhangig gegebenenfalls Umprogrammierung des Schrittmachers, kontinuierliches EKG-Monitoring sowie kardiologisches Stand-By sind notwendig. Purpose: MRI is currently regarded as absolutely contraindicated in patients with implanted cardiac pacemakers. In this prospective study safety and feasibility of MRI in patients with new generation pacemakers (PM) was evaluated in vitro and in vivo. Methods: 14 PM models in vitro and 18 patients with implanted new generation PM underwent a MRI exam at 0.5 Tesla with standard spin, turbo spin, and gradient echo (FFE) sequences under continuous ECG-monitoring. PM inquiry was performed before and after the MRI exam, including assessment of stimulation thresholds. R- In the static magnetic field all PM switched to the asynchronous mode due to activation of the Reed switch, resulting in continuous pacing at a fixed rate. In three PM models in vitro, however, after activation of the Reed switch, there was a software-induced switch back to the demand mode. In these PM inhibition and triggering were observed after starting the MRI scan due to influence of the pulsed magnetic fields. PM program changes, damage of PM components, dislocation/torque of the PM and rapid pacing of the PM were observed neither in vitro nor in vivo. Atrial and ventricular stimulation thresholds remained unchanged. Conclusion: MRI at 0.5 Tesla should not be regarded as absolutely contraindicated in patients with implanted new generation PM. However, knowledge of the behaviour of the specific PM model in static and pulsed magnetic fields is required, if necessary also changes of the PM program prior to the MRI exam, continuous ECG monitoring and cardiological stand-by.

PURPOSE To define the diagnostic efficacy of MR imaging, "time of flight" (TOF) and phase contrast (PC) MR angiography in craniocervical arterial dissections. MATERIAL AND METHODS The MR examinations of 16 patients with proven arterial dissections (n = 20) were retrospectively analysed by three independent readers. The MR protocol included T1w spin echo sequences with and without fat saturation (SPIR), T2w-turbo-spin echo, 2D- and 3D-TOF- and 3D-PC-MRA. The study was undertaken to assess the diagnostic sensitivity of each technique in detecting typical pathological features. RESULTS The overall sensitivity was best in 3D-PC-MRA; reaching 88% of all possible points. Intramural haematoma could be easily detected with T1W spin echo with fat saturation (100%). Intimal flap and lumen narrowing was best defined with 3D-TOF-MRA in 86% resp. 96% and 3D-PC-MRA in 69% resp. 97%. 3D-PC-MRA was superior to all other sequences in 5 cases of aneurysmal dissection (100%). CONCLUSIONS An accurate evaluation of craniocervical arterial dissections should rely on a combined protocol including T1w spin echo with fat saturation and an axial 3D-MR angiography (if possible 3D-phase contrast MRA).

Ziel: Experimentelle Untersuchung zur Lokalisierbarkeit MR-tauglicher Punktionsnadeln bei 1,0 T anhand von Signalausloschungen und -anhebungen. Methode: Fur MR-geeignete Punktionsnadeln in unterschiedlichen Orientierungen wurden in einem Phantom die Differenzen zwischen tatsachlicher und abgebildeter Lage bei Spin-Echo-(SE-) und Turbo-Spin-Echo-(TSE-) Sequenzen ermittelt. Ergebnisse: Grose und Form der Artefakte hangen ab von der Lage der Nadel zu B0, Frequenzkodierung (Gf) und Schichtorientierung. Die Artefakte sind bei Punktionen von rechts, links, kranial oder kaudal unterschiedlich. Fur eine 18 G-Nadel (Cook) parallel zu Gf z.B. reicht die Signalausloschung bei einer punktionstauglichen TSE-Sequenz abhangig vom Winkel zu B0 0,3-4,6 mm weiter als die Nadelspitze. Die Ausloschung um den Nadelschaft ist unterschiedlich breit, die Nadel liegt in der Mitte. Liegt Gf senkrecht zur Nadel, betragt die Fehlregistrierung an der Spitze 2,7-3,3 mm, die Nadel liegt bis zu 3,3 mm neben der Mitte der Ausloschung. Die nominale Echozeit beeinflust die Grose des Artefaktes bei TSE-Sequenzen nicht, er nimmt aber zu mit kleinerer Matrix und weniger steilen frequenzkodierenden Gradienten. Auch Material und Masse der Nadel bestimmen die Artefaktgrose. Schlusfolgerung: Bei MR-gesteuerten Punktionen kann die Prazision der Nadellokalisation durch geeignete Wahl der Richtung von Gf optimiert werden, je nachdem, ob Schaft oder Spitze der Nadel lokalisiert werden sollen. Purpose: To evaluate accuracy of needle localisation using signal void and signal enhancement on a LOT MR imager for various needles for MR-guided biopsy. Methods: The differences between actual and virtual needle position of needles with different orientations were evaluated in a phantom for spin-echo including turbo-spin-echo sequences. Results: Artifacts depended on the orientation of the needle relative to the field B0, frequency-encoding gradients (Gf) and slice orientation. This resulted in different artifact shapes and sizes for left or right and cranial or caudal biopsy access routes. Applying turbo spin echo sequences feasible for biopsy, the signal void of a 18 G needle (Cook) parallel to Gf reached between 0.3 and 4.6 mm further into the medium than the real needle tip, depending on needle orientation relative to B0. The diameter of the signal void around the needle varied, the needle shaft was right in the centre of the signal void. With Gf orthogonal to the needle the offset of signal void to needle tip ranged from 2.7 to 3.3 mm, while the actual position of the needle shaft was up to 3.3 mm lateral of the signal void center. While nominal echo times did not influence the size of the artifact in turbo-spin-cho sequences, the artifacts increased with smaller matrix and larger water-fat shift. Material and mass of the needle determined the size of the artifacts as well. Conclusion: Localisation accuracy of the needle can be optimised by choosing optimal gradient directions depending on whether needle tip or shaft position should be displayed.

PURPOSE Our goal was to investigate the value of T2-weighted fast SE (FSE) sequences, FSE sequences with shortened echo spacing (UFSE), combined gradient and spin echo sequences (GRASE), and segmented T1-weighted echo planar imaging (EPI) in comparison with conventional SE sequences in the detection of focal liver lesions. METHOD Thirty-five patients with malignant focal liver lesions underwent MRI at 1.0 T. RESULTS All fast T2-weighted imaging techniques (FSE, UFSE, GRASE) showed fewer artifacts and overall better image quality than the conventional SE sequence. Quantitative analysis demonstrated that UFSE imaging had the highest tumor/liver contrast/noise ratio (C/N) (13.9 +/- 5.5) followed by FSE (12.7 +/- 4.5), T2 SE (10.9 +/- 4.2), and GRASE (10.0 +/- 4.8) sequences. The differences in C/N between the UFSE and T2 SE sequences was statistically significant (p < 0.05). C/N was significantly higher (p < 0.01) for the T1 SE (-7.4 +/- 3.8) than for the EPI sequence (-0.5 +/- 5.6). CONCLUSION FSE sequences with shortened echo spacing are valuable for liver imaging at 1.0 T. In comparison with the T2 SE sequence, they yielded better image quality and comparable tumor/liver C/N.

Zusammenfassung Ziel: Die MRT ist integraler Bestandteil der prächirurgischen Diagnostik von Patienten mit fokalem Anfallsleiden. Diese weisen häufig eine um’schriebene morphologische Läsion mit potentiell epileptogenem Cha’rakter auf, deren Resektion in bis zu 90% der Patienten zu einer deutli’chen oder kompletten Reduktion der Anfälle führt. Neben relativ einfach nachweisbaren Schädigungen, wie z. B. kortikalen Defekten (z. B. Trauma, Infarkt), kommt eine Vielzahl oft winziger Läsionen unterschiedlicher Ätiologie als auslösende Ursache in Frage. Dies stellt eine suffiziente Bildgebung mit der MRT insofern vor Probleme, als auf Grund der untersuchungstechnischen Belastung der Patienten nur eine limitierte Anzahl von Sequenzen durchgeführt werden kann. Methode: Es wurden insgesamt 484 Patienten mit fokalem Anfallslei’den frontalen oder temporalen Ursprunges hinsichtlich der MR-tomo-graphisch erhobenen Befunde untersucht. Dabei wurde keine Einteilung hinsichtlich einer möglichen Epileptogenität solcher Läsionen vorge’nommen, da diese ohnehin rein morphologisch nicht eindeutig zu be’stimmen ist. Ergebnisse: In diesem Patientengut konnte gezeigt werden, daß hoch’frequent nachgewiesene Läsionen bei Temporallappenepilepsie in Schä’digungen des Hippokampus (Atrophie, Sklerose) (15%) und darüber hin’aus im Gesamtkollektiv mit absteigender Häufigkeit verschiedene Tu’moren (ca. 14%), Schädel-Hirn-Traumata (ca. 5%), kortikale Anla’gestörungen (ca. 4%) und eine Vielzahl ähnlich häufiger anderer Läsio’nen ursächlich in Frage kommen. Diese Läsionen werden mit jeweils unterschiedlichen Sequenzen sensitiv erfaßt, so daß insgesamt bei fokalen Epilepsien standardisiert 3 Ebenen unter Einschluß einer T1-ge-wichteten-SE-, und von möglichst je 2 (koronal und axial) Doppel-Echo-SE- und T1-gewichteten IR-Sequenzen untersucht werden sollten. Da’gegen ist eine standardisiert durchgeführte Kontrastmittelapplikation nicht erforderlich. Schlußfolgerung: Die Sensitivität moderner MR-Tomographen liegt bei rein qualitativer Befundung und unter Einschluß sämtlicher umschriebe’ner Pathologien derzeit insgesamt im Bereich von 75% aller Fälle, bzw. bei 79% für temporale und etwa 67% für frontale fokale Epilepsien. Quantitative Volumenbestimmungen und eine T2-Relaxometrie der Hip-pokampi sollen insbesondere bei Temporallappenepilepsie die Sensiti’vität der Methode zu steigern.

PURPOSE: To evaluate the value of rapid T2-weighted turbo-spin sequences (TSE), turbo-spin-echo sequences with shortened echo spacing (UTSE), gradient-and-spin-echo sequences (GraSE) and T1-weighted echo-planar imaging (EPI) in comparison with conventional spin-echo sequences (SE) in the diagnosis of focal liver lesions. METHODS: 20 patients with malignant focal liver lesions underwent magnetic resonance imaging at 1.0 tesla. RESULTS: The use of fast T2-sequences (TSE, UTSE, GraSE) reduced the examination time to about 35-50%. Artifacts were reduced compared with the conventional T2-SE sequence. Quantitative analysis demonstrated that UTSE imaging had the highest tumor/liver contrast-to-noise ratio (CNR) followed by TSE, T2-SE and GraSE sequences. CNR with EPI was lower than with the T1-SE sequence (p < 0.05). CONCLUSION: Turbo-spin-echo sequences with shortened echo spacing yield a shorter imaging time and improved image quality without loss of signal intensity in tumor/liver-CNR, compared with conventional T2-pulse sequences in liver imaging at 1.OT.

PURPOSE: Development of an improved MR sequence for examining the lung. METHOD: T2 weighted ultra-short turbo spin echo sequences were used in five individuals with variations in echo times, delayed triggering and echo intervals. To reduce movement artifacts all examinations were carried out with ECG and respiratory triggering. The sequences giving optimal image quality were then employed in 19 patients having various pulmonary abnormalities. Image resolutions, artifacts, image contrasts and diagnostic value were then judged by two observers and compared with CT. RESULTS: In the first study, a diastole-triggered UTSE sequence with the shortest echo proved optimal (TE = 90 ms, TR = 2-4 s, echo = 9 ms, turbo factor = 19). In the patient series studied, MRT was inferior to CT with regard to resolution and number of artifacts, but better in respect of contrast and diagnostic value. CONCLUSION: Using UTSE of the lung, MRT can produce images of good quality. Compared with CT, contrast is better with MRT, offering diagnostic advantages for MRT.

PURPOSE To compare five pulse sequences in 60 patients with pancreatic disease by means of MRI at 0.5 T. METHODS T1 weighted Spin-Echo sequences (T1W SE) before and after i.v. contrast medium administration, fat-suppressed T1W SE sequences after i.v. contrast medium administration, T2 weighted Turbo-Spin-Echo sequences (T2W TSE), and fat-suppressed T2W TSE were evaluated within an ROC study. RESULTS The standard sequences (T1W SE before and after i.v. contrast medium administration, T2W TSE) were superior to the fat-suppressed T1W and T2W (T)SE sequences in delineating the anatomy and for correct diagnosis. The T1W sequence with and without i.v. contrast media detected all anatomic structures best. In most instances the correct diagnosis and coexistent findings in the diseased pancreas were obtained with the T2W sequence. CONCLUSION Fat-suppressed sequences are less useful in the diagnosis of pancreatic disease by MRI at medium field strength compared to the standard sequences.

Purpose Aim of the study was to evaluate FLAIR combined with Turbo-Spin-Echo (Turbo-FLAIR) at 0.5 tesla in comparison to conventional T1- and T2-weighted spin-echo images (SE) in MRI of the brain. Material and methods A Turbo-FLAIR sequence was optimised for 0.5 Tesla (Philips Gyroscan T5-II) that provided seventeen 5 mm sections in 4:21 minutes (TR = 6075 ms, T1 = 1600 ms, TE = 120 ms and a turbofactor = 17). Images were compared with T1- (TR = 500 ms, TE = 15 ms) proton density and T2-weighted spin-echo (TR = 2500 ms, TE = 20/90 ms) studies in 10 healthy volunteers and 30 patients with various brain pathologies. Results Turbo-FLAIR could effectively eliminate the CSF signal in all studies except ventricular areas with CSF inflow. Contrast-to-noise ratios (C/N) for the contrast between lesions and CSF was superior in Turbo-FLAIR. C/N between lesions and grey matter was significantly higher in Turbo-FLAIR than in proton density (PD)-weighted SE. C/N between lesions and white matter was equal to PD-weighted SE but significantly smaller than on T2-weighted SE. Visual analysis showed greater lesions conspicuity with Turbo-FLAIR and a higher frequency of detection of cortical and subcortical lesions. Conclusions Turbo-FLAIR is a reliable and practical technique on 0.5 Tesla, that is more sensitive than SE sequences especially for the detection of cortical, subcortical lesions and lesions surrounded by CSF.

AIM The value of turbo-spin-echo (TSE) sequences was compared with conventional spin-echo (SE) and inversion-recovery (IR) sequences for cerebral MRT in 70 children at 0.5 T and 1.5 T. In addition we evaluated whether proton weighted sequences (PD) were diagnostically important and in what proportion of cases. METHOD Conventional T1 and T2 weighted SE and T2 weighted TSE sequences were used in all children. An IR sequence was performed in 39 patients. The various sequences were analysed semiquantitatively with regard to image quality, artifacts and the demonstration of normal and anatomical structures and pathological findings. RESULTS By any criteria, TSE sequences were superior to conventional T2 weighted SE sequences at 0.5T and 1.5 T, requiring a shorter examination time (35-53%). In 8.6% the pathological finding was best seen on PD-SE sequences (5 glial scars, 1 tumor). CONCLUSION Although TSE sequences are better than T2 SE sequences with regard to image quality and the demonstration of abnormalities, conventional double-echo SE sequences (with PD and T2 weighted images) cannot be entirely replaced by T2 weighted TSE sequences in children.

The aim of this study was the evaluation of spiral computed tomography (Spiral-CT), multiplane transesophageal echocardiography (multiplane TEE) and magnetic resonance imaging (MRI) in the diagnosis of thoracic aortic dissection. 41 patients were examined: 30 with clinically suspected acute aortic dissection (14 Stanford A, 7 Stanford B), 11 with aortic repair (7/11 with persisting distal dissection). In 14 patients there was involvement of the supraaortic vessels. Sensitivity of Spiral-CT, multiplane TEE and MRI in the detection of aortic dissection was 100%, specificity was 100, 92, and 91%. In the assessment of involvement of aortic arch vessels sensitivity was 100, 67, and 60%, specificity was 100, 95, and 90%. The new imaging modalities Spiral-CT and multiplane TEE are equal to MRI in the detection of aortic dissection. In the assessment of the supraaortic branches Spiral-CT is superior to multiplane TEE and MRI and might become the method of choice.

BACKGROUND AND PURPOSE: 4D-MRA is a promising technique in the diagnosis and follow-up of cAVMs. The purpose of this study was to compare 4D-MRA in the pre- and postoperative evaluation of cAVMs with DSA or intraoperative findings as the standards of reference regarding qualitative and quantitative parameters. MATERIALS AND METHODS: Fifty-six consecutive patients with cAVMs (30 women) underwent both 4D-MRA and DSA. Preoperative 4D-MRA was excluded from analysis in 1 patient (movement artifacts). Twenty-five patients underwent surgery on cAVMs and underwent both imaging modalities pre- and postoperatively. 4D-MRA was performed with either 0.5-mol/L gadolinium-diethylene-triamine pentaacetic acid (group 1: voxel size, 1.1 × 1.1 × 1.4 mm(3); 608 ms/dynamic frame; 19 patients) or 1.0-mol/L gadobutrol (group 2: voxel size, 1.1 × 1.1 × 1.1 mm(3); 572 ms/dynamic frame; additional alternating view sharing; 37 patients). Two readers independently reviewed 4D-MRA and DSA regarding the Spetzler-Martin classification, arterial feeders, and postoperative residual filling. Vessel sharpness, vessel diameter, and VBC of 4D-MRA were quantified. RESULTS: Preoperative Spetzler-Martin classification 4D-MRA and DSA ratings matched in 55/55 patients (Spetzler-Martin grades: I, 12; II, 22; III, 15; IV, 5; V, 1), and 93/100 arterial feeders were correctly identified by preoperative 4D-MRA (7 additional arterial feeders identified by DSA only: group 1, 3/19; group 2, 4/36). Postoperative 4D-MRA and DSA matched in 25/25 patients (residual filling, 1/25). Vessel sharpness and diameters did not differ substantially between the 2 groups. VBC was significantly higher in group 2 (P < .005). CONCLUSIONS: 4D-MRA is a reliable tool that allows predicting Spetzler-Martin classification and postoperative residual filling; it hence allows substituting DSA in the pre- and postoperative evaluation of patients with cerebral AVMs.

Cognitive decline is a well recognized complication after on-pump coronary artery bypass graft (CABG) surgery. We investigated whether the design of extracorporeal circulation (ECC) and the extent of perioperative heparinization have an impact on neurological dysfunction.Sixty-three CABG surgery patients were randomly perfused with an uncoated ECC-set (group A) or with two different heparin-coated ECC-sets (groups B and C). In groups A and B, systemic heparin was given in doses of 400 IU/kg body weight, whereas group C received 150 IU/kg body weight. ECC sets in group C included a diagonal pump and low priming as opposed to roller pumps in groups A and B. Furthermore, in group C blood contact to surfaces other than endothelium and heparin coated material was eliminated. Brain lesions were detected by diffusion-weighted magnetic resonance imaging (DWI). Neurological complications were assessed clinically until discharge (manifest motoric, sensitive or cognitive disturbance). Biochemical coagulation and inflammation parameters were measured pre-, peri-, and postoperatively.No major neurological events were observed in either group until discharge. DWIs showed 61 new lesions in 19 of 45 patients who terminated all MRI study procedures. Number and volume of the lesions did not differ between groups (P0.05). Biochemical and inflammatory parameters showed the expected time courses and variations between groups.Ischemic brain lesions are frequently observed in CABG surgery patients but are neither associated with clinically relevant neurological complications nor with ECC set-up and intraoperative heparin dosage. DWI may help in the development of new surgical strategies to reduce postoperative brain damage.

To evaluate the cardiovascular system with magnetic resonance (MR) imaging performed with the turbo spin-echo (TSE) method and electrocardiogram (ECG) gating.ECG-gated T2-weighted TSE images were obtained in 52 patients with 68 pathologic conditions (intracardiac [n = 18], myocardial [n = 23], pericardial [n = 6], paracardial [n = 10], or aortic [n = 11] disease) and 10 healthy subjects. In healthy subjects, TSE parameters were tested and optimized, and signal-to-noise ratios (S/Ns) and contrast-to-noise ratios (C/Ns) were determined. Delineation of the endo-, epi-, and pericardial borders and signal intensity characteristics of myocardium, fat, pericardium, blood flow, tumors, and clots were assessed.The TSE method provided good-quality T2-weighted images with sharp edge definition in a short imaging time. Increasing the turbo factor reduced motion artifacts and preserved the S/N and C/N. TSE images also helped in diagnosis of tumors, pleural effusions, inflammatory changes, and intravascular clots.TSE MR imaging is a feasible alternative to time-consuming conventional SE MR imaging, reduces motion artifact, and may help in evaluation of the cardiovascular system.

A method of calibrating and extracting velocities from arbitrary geometry triple hot-wire probes has been developed and tested. The three-step procedure involves experimental determination of an accurate cooling law for each wire in the array, use of these models to develop a set of tables relating anemometer output to flow velocity input, and a table look-up procedure to extract the velocities. The functional form for the cooling law can be arbitrarily chosen and these equations are never directly inverted. Solutions are tabulated making use of special variable transformations that separate the dependence on flow angle and velocity magnitude. Errors in the table look-up procedure are commensurate with those in exact inversion techniques. Most of the error arises from accurate determination of the cooling laws. An application to turbulent boundary layer measurements is presented as an example of the use of the method.

Purpose: The use of high-field MRI scanners has introduced new challenges for cardiac imaging, associated with B1- and B0-field inhomogeneities. A dual – source RF transmission system may help reduce dielectric effects, thus improving image contrast and reducing local SAR peaks of cardiac TSE and SSFP sequences, thereby allowing a shorter minimum TR and TE of SSFP sequences. Thus, the aim of our study was to evaluate the impact of dual – source parallel RF transmission with patient adaptive RF-shimming on image quality and diagnostic confidence for routine clinical CMR using a 3.0 T dual – channel transmit whole – body MRI system. Materials and Methods: A clinical 3.0 T MRI system (Achieva 3.0T-TX, Philips Healthcare, Best, Netherlands), equipped with a dual-source RF transmission system was used. The effect of parallel RF transmission with patient adaptive B1 shimming (multi transmit=MTx) vs. conventional (single transmit=STx) RF transmission on SSFP sequences and TSE Black-Blood (TSE BB) sequences was evaluated. Images were analyzed independently by two experienced readers for homogeneity and diagnostic confidence on a 4-point grading-scale. Also, the presence of off-resonance artefacts in the SSFP images was rated on a 4-point grading scale. CNR between interventricular septum and blood pool was determined. Results: A total of 21 patients were included into the study. For both, TSE BB and SSFP -images, the use of MTx resulted in a significant improvement of image homogeneity and diagnostic confidence in the left and right ventricle. As a side effect, off-resonance artefacts were significantly reduced in the acquired SSFP images. Interrater agreement for all ratings was very good. The quantitative measurements revealed a significant increase of CNR in the RF shimmed images using MTx compared to the images acquired with STx.((BR))Conclusions: Patient adaptive local RF-shimming using parallel dual source RF-transmission significantly improves image homogeneity, diagnostic confidence and contrast of cardiac SSFP and TSE BB sequences.