[Impact of anamnestic information and neurological deficits on the detection rate of secondary headaches]. / Einfluss von Anamnese und neurologischer Untersuchung auf die Detektionsrate sekundärer Kopfschmerzursachen.

PURPOSE: Headaches are a very common symptom and imaging is important to rule out symptomatic causes. For clinical differentiation between primary and secondary headaches an exact anamnesis and neurological examination are important. The aim of this study is therefore to identify anamnestic and neurological information that is associated with secondary headaches. Moreover, this study gives an overview of the causes and differential diagnoses of secondary headaches. METHODS: We performed a retrospective analysis of 239 patients ≥18 years with headaches who had undergone computed tomography or magnetic resonance imaging. The impact of basic characteristics such as age and gender as well as anamnestic (pain intensity, thromboembolic risk profile) and clinical information (neurological deficit, papilledema, reduced vigilance) was tested by χ2 test at the significance level p < 0.05. RESULTS: In all, 27 of the included patients (11.3%) showed intracranial pathologies that required treatment. The most frequent pathologies were intracranial hypertension (9 patients), cerebral mass lesions (7 patients) and thrombosis of the cranial sinus/veins (3 patients). There was a significant association of a pathologic imaging finding and neurological deficits (p = 0.001) and a papilledema (p < 0.001). Reduced vigilance, pain intensity and thromboembolic risk factors as well as age and gender showed no significant association. CONCLUSIONS: A neurological deficit and especially papilledema are hints towards secondary headaches and should result in computed tomography or magnetic resonance imaging. Other factors such as reduced vigilance, pain intensity, age and gender have no relevant impact on the occurrence of intracranial pathologies.

Sensitivity of T2-weighted FSE sequences towards physiological iron depositions in normal brains at 1.5 and 3.0 T.

To evaluate the sensitivity of T2-weighted fast spin-echo (FSE) sequences to physiological iron depositions in normal brains at MR imaging field strengths of 1.5 and 3.0 T. T2-weighted FSE sequences acquired at 1.5 and 3.0 T clinical imaging systems (Gyroscan Intera, Philips Medical Systems, Best, The Netherlands) were compared by means of MRI in phantoms ( n=6) and healthy volunteers ( n=10). Contrast-to-noise ratios (CNRs) of tubes doped with iron oxides at different concentrations and of brain areas with physiological iron depositions (nucleus ruber, substantia nigra, globus pallidus) were calculated for either field strength. Apparent susceptibility effects of iron-containing brain structures were qualitatively analyzed by comparing the degree of visible hypointensity by a score system at either field strength. The mean CNR of iron oxide tubes and iron-containing brain areas was significantly decreased at 3.0 T. Qualitative analysis confirmed these measurements. Detection and diagnosis of brain disorders with altered iron content such as neurodegenerative parkinsonian disorders (NPD) or intracerebral hemorrhage should benefit from the increased sensitivity of T2-weighted FSE sequences to susceptibility effects at 3.0 T.

Magnetic resonance imaging protocols for examination of the neurocranium at 3 T.

The increasing availability of high-field (3 T) MR scanners requires adapting and optimizing clinical imaging protocols to exploit the theoretically higher signal-to-noise ratio (SNR) of the higher field strength. Our aim was to establish reliable and stable protocols meeting the clinical demands for imaging the neurocranium at 3 T. Two hundred patients with a broad range of indications received an examination of the neurocranium with an appropriate assortment of imaging techniques at 3 T. Several imaging parameters were optimized. Keeping scan times comparable to those at 1.5 T we increased spatial resolution. Contrast-enhanced and non-enhanced T1-weighted imaging was best applying gradient-echo and inversion recovery (rather than spin-echo) techniques, respectively. For fluid-attenuated inversion recovery (FLAIR) imaging a TE of 120 ms yielded optimum contrast-to-noise ratio (CNR). High-resolution isotropic 3D data sets were acquired within reasonable scan times. Some artifacts were pronounced, but generally imaging profited from the higher SNR. We present a set of optimized examination protocols for neuroimaging at 3 T, which proved to be reliable in a clinical routine setting.

Multislice CT angiography of the iliac arteries in the presence of various stents: in vitro evaluation of artifacts and lumen visibility.

RATIONALE AND OBJECTIVES: To evaluate the imaging characteristics of various iliac artery stents and stent-grafts in a multislice, computed tomography angiography (MSCTA) phantom study. METHODS: Twelve types of stents and three stent-grafts made of different materials (steel, nitinol, tantalum, cobalt-based alloy) were implanted in plastic tubes with an 8-mm inner diameter filled with iodinated contrast medium diluted to 200 HU. To evaluate the influence of scan parameters on artifacts, the Palmaz stent (as one example) was scanned with a four-slice scanner (Siemens VolumeZoom) with different detector collimations and pitches. All other stents were examined with a collimation of 4 x 1 mm and a table feed of 4 mm/rotation. Axial images and multiplanar reformations were evaluated regarding artifact size, lumen visibility, and intraluminal attenuation values. RESULTS: Higher pitch values caused more pronounced artifacts. Image quality and delineation of the stent struts improved with thinner detector collimation. The size of the stent-related artifacts and the visibility of the stent lumen depended on the underlying stent material and design. Pronounced artifacts, resulting in an insufficient delineation of the stent lumen, were caused by the Strecker tantalum stent and the Zenith stent. Moderate artifacts were caused by the Wallgraft, Passager, Palmaz P 395 and P 424, Bridge, Perflex, and ZA stents. Some artificial lumen narrowing but good lumen delineation was seen with the Strecker nitinol, Symphony, Memotherm, SMART, Corinthian, and Wallstent stents. CONCLUSIONS: Scanning parameters, stent material, and stent design influence lumen assessability and image quality in MSCTA. Detailed lumen assessment is impossible in the Strecker tantalum and Zenith stents and limited in the Wallgraft, Passager, Palmaz P 395 and PS 424, Bridge, Perflex, and ZA-stent stent-grafts but feasible in all other examined products.

[Gd-BOPTA enhanced excretory MR urography without administration of diuretics]. / Gd-BOPTA-gestützte MR-Ausscheidungsurographie ohne Diuretikagabe.

PURPOSE: To evaluate the feasibility and clinical utility of Gd-BOPTA enhanced excretory magnetic resonance urography without additional administration of diuretics in correlation with conventional urography. METHOD: 15 preoperative patients with pelvic tumors were examined at 1.5 T using a breath-hold high-resolution 3D-FLASH sequence during first-pass as well as 5, 10, 15 minutes after i.v. injection of 0.05 mmol/kg BW Gd-BOPTA (MultiHance) without administration of diuretics. Post-processed coronal and multiplanar MIP reconstructions were compared to conventional excretory urography with regard to morphologic accuracy, anatomic variability, filling defects, cause and level of obstruction or compression, tumor visibility, and time-effectiveness by two independent radiologists. RESULTS: Visualization of the urinary tract by MRU was comparable to conventional excretory urography in 14 of 15 cases. Caliceal fornices were better delineated on conventional urographies, whereas MRU was considered superior in the assessment of the inferior ureter sections, the urinary bladder and obstructive tumors, whose extents could be clearly marked out. Examination times of both techniques were comparable. CONCLUSION: These first results show that non-diuretic Gd-BOPTA enhanced MRU is comparable to conventional excretory urography for the preoperative diagnosis of pelvic tumors. Further improvements of this technique seem possible by optimization of examination intervals and injection doses.

Does a higher concentration of gadolinium chelates improve first-pass cardiac signal changes?

The purpose of this study was to evaluate first-pass cardiac signal changes with a higher concentrated gadolinium-chelate (gadobutrol) and its influence on bolus geometry. Phantom studies and in vivo first-pass cardiac studies were performed in rabbits (n = 8 experiments) under general anesthesia at 1.0 T using an ultrafast T1-weighted Turbo-fast low-angle shot (FLASH) sequence (TR/TE 4.7/1. 6 msec, alpha = 90 degrees ) with a time resolution of 870 msec. Gadobutrol was injected as an intravenous bolus at two concentrations (0.5 and 1.0 mol Gd/L) and five doses (0.3, 0.15, 0.1, 0.055, and 0.03 mmol Gd/kg bw). The blood-pool gadolinium compound gadopentetate dimeglumine-polylysine (0.15, 0.075, 0.05, and 0.015 mmol Gd/kg bw, 0.5 mol Gd/L) and the standard extracellular gadopentetate dimeglumine (0.1 and 0.05 mmol Gd/kg bw, 0.5 mol Gd/L) served as reference agents. Cardiac signal changes were calculated from serial signal intensity measurements. Maximum signal intensity changes and best peak profiles during first pass of the right and left ventricle were observed with a dose of 0.03 mmol Gd/kg bw gadobutrol using T1-weighted Turbo-FLASH. At the low application volumes used, the higher concentration of 1.0 mol Gd/L gadobutrol did not increase the degree of signal intensity changes or sharpen the bolus profile. First-pass cardiac signal changes using T1-weighted Turbo-FLASH with the new extracellular contrast agent gadobutrol are best observed at a dose of 0.03 mmol Gd/kg bw. There is no advantage to the concentrated formulation (1 mol Gd/L gadobutrol) when using small injection volumes. J. Magn. Reson. Imaging 1999;10:806-812.

RES-specific imaging of the liver and spleen with iron oxide particles designed for blood pool MR-angiography.

The purpose of this study was to determine the dependency of liver- and spleen-enhancement on particle size and dose of bolus-injectable iron oxides designed for blood-pool MR-angiography (MRA). The superparamagnetic iron oxide SHU 555 A [particle size 65 nm (group 1)] and three derivatives designed for blood-pool MRA (groups 2-4) with smaller hydrodynamic diameters (46/33/21 nm) were i.v. injected in New Zealand White rabbits at doses of 10, 20, or 40 micromol Fe/kg bw. MRI was performed before, 2, and 24 hours after contrast application using T1-weighted SE and T2-weighted TSE sequences. In addition splenic tissue was harvested post mortem and scanned ex vivo. All iron oxides significantly decreased the SI of liver and spleen in T1- and T2-weighted images at 2 and 24 hours after application of contrast media (P < 0.01). The signal intensity was inversely related to the dose applied. Decreasing particle size resulted in a lower signal enhancement in liver and spleen. However, ultra-small superparamagnetic iron oxides suited for blood-pool MRA (USPIOs, group 4) still revealed a significant signal enhancement in the liver and spleen even 24 hours after contrast application (< - 60%, 40 micromol Fe/kg bw). They might thus be used for comprehensive abdominal studies including contrast enhanced MR-angiography and RES-specific imaging.

Contrast-enhanced 3D-MRA of the upper abdomen with a bolus-injectable SPIO (SH U 555 A).

The purpose of this study was to study temporal changes in signal intensity of liver, spleen, abdominal vessels, and focal liver lesions following iv bolus injection of a superparamagnetic iron oxide (SPIO) using a breath-held three-dimensional magnetic resonance angiography (3D-MRA) sequence. Dynamic SH U 555 A-enhanced 3D-MRA studies were performed in 20 patients with focal liver lesions. Sequential coronal 3D-MRA-FISP scans were acquired (TR 5.0 msec, TE 2.0 msec, flip angle 25 degrees, 140 x 256 matrix, and 80 mm slab) within 15 seconds. Scanning was started immediately after bolus injection of 10 micromol Fe/kg bodyweight and was repeated at multiple time points (baseline and 30, 60, 90, 120, 180, 240, 300, 360, and 420 seconds). Signal intensity values of liver, focal liver lesions, spleen, the portal venous system, the abdominal aorta, and the inferior vena cava were obtained to calculate relative enhancement (ENH = [SI post - SI pre]/SI pre x 100). Visibility of vessels was assessed by consensus of two readers. Signal enhancement within abdominal vessels peaked during the first pass; however, significant signal enhancement was still present 420 seconds following injection. The liver and the spleen also demonstrated a biphasic enhancement pattern with prolonged parenchymal enhancement. Dynamic MRA with bolus injectable SH U 555 A is clinically feasible, and significant vessel enhancement can be achieved even at the dose of 10 micromol Fe/kg bodyweight. However, further refinements are required to improve contrast effects.

Breath-hold gadolinium-enhanced MR angiography of the major vessels at 1.0 T: dose-response findings and angiographic correlation.

PURPOSE: To find the appropriate contrast agent dose for gadolinium-enhanced magnetic resonance (MR) angiography by using individual measurement of contrast agent transit times in a randomized study. MATERIALS AND METHODS: A total of 34 patients with disease of the aorta or its major branches or both were randomly assigned to receive a dose of 0.1, 0.2, or 0.3 mmol of gadopentetate dimeglumine per kilogram of body weight. Initially, contrast agent transit times were measured with use of a turbo fast-low-angle-shot sequence. Subsequently, a three-dimensional fast imaging with steady-state precession sequence (7.3-msec repetition time, 2.8-msec echo time) was used for breath-hold MR angiography. Gadopentetate dimeglumine was injected with an MR-compatible power injector. Efficacy was evaluated by measurement of vessel enhancement and by clinical correlation of MR angiograms with x-ray angiograms. RESULTS: Evaluation of contrast agent transit time was possible in all patients with the test doses, which provided contrast-enhanced MR angiograms of constant quality. Neither vessel enhancement nor diagnostic information was significantly different across the these study groups. CONCLUSION: The clinical gadolinium dose of 0.1 mmol/kg is sufficient for diagnostic assessment of the aorta and its major branches at contrast-enhanced MR angiography. High-dose studies appear not to be required for these large vessels.

Study of susceptibility-induced artefacts in GRASE with different echo train length.

The aim of this study was to evaluate the sensitivity of gradient-and-spin-echo (GRASE) sequences to susceptibility effects. GRASE sequences with 21 and 33 echoes per echo train were compared with a T2-weighted FSE sequence with an echo train length of 5 by means of MRI in phantoms, volunteers (n = 10), and patients (n = 19) with old hemorrhagic brain lesions. All experiments were performed on a 1.0-T clinical MR system (Impact Expert, Siemens AG, Erlangen, Germany) with constant imaging parameters. Contrast-to-noise ratios (CNRs) of tubes doped with iron oxides at different concentrations, of brain areas with physiological iron deposition (red nucleus, substantia nigra), and of areas of old brain hemorrhage were calculated for FSE and GRASE pulse sequences. Areas of old brain hemorrhage were also qualitatively analyzed for the degree of visible susceptibility effects by blinded reading. The CNR of iron oxide tubes and iron-containing brain areas decreased with increasing echo trains of GRASE sequences. The CNR of GRASE sequences decreased when compared with CNR of their FSE counterparts (GRASE 21 echo trains 23.8 +/- 0.8, FSE 5 echo trains 26.7 +/- 0.9; p

[T1-weighted dynamic MRI with new superparamagnetic iron oxide particles (Resovist): results of a phantom study as well as 25 patients]. / T1-gewichtete dynamische MRT mit neuen superparamagnetischen Eisenoxidpartikeln (Resovist): Ergebnisse einer Studie am Phantom sowie an 25 Patienten.

PURPOSE: Evaluation of the diagnostic usefulness of the T1-effect of Resovist (SPIO) for dynamic MRI of the liver. METHOD: In-vitro measurements of a dilution series with T1-weighted FLASH and SE sequences and investigation of 25 patients with known focal liver lesions with a T2-weighted TSE sequence and a dynamic T1-FLASH sequence. RESULTS: T1-weighted MRI with Resovist in vitro showed a positive enhancement at low concentrations and a negative enhancement at higher concentrations. In-vivo T1-weighted dynamic MRI liver parenchyma demonstrated a positive enhancement 30 s post contrast, followed by a continuous slope of signal intensity and a negative enhancement (> or = 60 s). Spleen, portal venous vessels and haemangiomas showed an early increase in signal intensity followed by a decreasing positive enhancement, but without negative enhancement. During the perfusion phase metastases showed a small but not significant increase in signal intensity. In 80% a positive ring enhancement could be observed around metastases. CONCLUSION: Resovist exhibits a diagnostically useful T1-effect. An evaluation of the perfusion of focal liver lesions during the distribution phase is possible with dynamic T1-weighted MRI. This approach may further improve characterisation of focal liver lesions.

[Combined use of ECK-triggered 2D-phase contrast MR angiography and 2D-time-of-flight MR angiography for planning and follow up before and after vascular intervention of pelvic and leg arteries]. / Kombinierter Einsatz der EKG-getriggerten 2D-Phasenkontrast-MR-Angiographie und der 2D-Time-of-Flight-MR-Angiographie zur Planung und Verlaufskontrolle vor und nach Gefässinterventionen der Becken- und Beinarterien.

PURPOSE: To develop a strategy for the complete work-up of vessel lumen and vessel wall for planning and follow-up of radiological interventions of lower extremity arteries. METHODS: A total of 36 patients (21 pre-, 8 post- and 7 pre- and postinterventional) were studied. MRA studies were performed using an ECG-triggered phase contrast technique for the demonstration of intraluminal flow and an axial high resolution time-of-flight technique to assess the vascular wall. All MRA studies were analysed by intraindividual DSA comparison for the assessment of flow and wall structures. RESULTS: Combined MRA techniques provided a good correlation with DSA for the assessment of vascular flow. The kappa test revealed a value of greater than 0.61 for most on the vessel segments proving a good correlation of both methods. Orthogonal high-resolution TOF-MRA provided additional information for the assessment postinterventional wall haematomas and hard plaques. CONCLUSION: Combination of PCA to study flow and axial TOF to study wall pathology improves the usefulness of peripheral MRA.

MR-monitored LITT as a palliative concept in patients with high grade gliomas: preliminary clinical experience.

The purpose of this study was to evaluate the clinical utility of laser-induced thermotherapy (LITT) as a palliative treatment for patients with high-grade gliomas. Four consenting patients with recurrent high grade III/IV gliomas near the primary language or motor areas were palliatively treated with LITT (2-5 W, 3-13 minutes; Neodym YAG Laser, Dornier, Friedrichshafen, Germany). Temperature monitoring was performed by T1-weighted turbo-fast low-angle shot (FLASH) imaging at 1.5 T (Siemens Magnetom SP 4000, Siemens, Erlangen, Germany). MRI studies before LITT included contrast-enhanced conventional scans and functional activation studies to localize the primary motor cortex or language areas using an echo-planar imaging (EPI) spin-echo (SE) sequence. Follow-up studies consisted of contrast-enhanced conventional scans as well as diffusion studies (contrast-enhanced Fourier-acquired steady-state technique and EPI-SE) and perfusion studies (EPI-SE with .2 mmol of gadolinium (Gd)/kg body weight) to differentiate post-therapeutic effects from residual or recurrent tumor growth. Local tumor control was achieved in areas with laser energy deposition with clinically stable conditions > or = 6 months. Conventional contrast-enhanced scans demonstrated strong enhancement surrounding ablated tumor components, which showed a reduction in CBV/CBF. Perfusion studies were useful to discriminate granulomatous tissue enhancement from residual or recurrent tumor growth. Careful application of LITT may evolve as an alternative palliative concept for patients with end-stage high-grade cerebral gliomas reducing clinical symptoms from circumscribed areas of pathology.

Preliminary clinical experience with laser-induced interstitial thermotherapy in patients with hepatocellular carcinoma.

The purpose of this preliminary study was to evaluate whether laser-induced interstitial thermotherapy (LITT) may be used for palliative treatment of localized hepatocellular carcinomas (HCC). We applied LITT to two patients suffering from unresectable localized hepatocellular carcinomas of different sizes (2.5 and 4 cm). LITT was performed with an Nd:YAG laser (1,064 nm) at 5 W laser power (15-20 minutes). Thermometry during LITT was performed by MRI using a temperature-sensitive T1-weighted fast low-angle shot (FLASH) sequence. Follow-up for local tumor control was performed by MRI and ultrasound. LITT was well tolerated and no adverse events occurred during or after LITT; no secondary liver lesions were seen in the follow-up (11 or 12 months, respectively). Only minimal tumor growth was observed in the larger HCC (from 4 to 5 cm), whereas the smaller HCC remained unchanged in size during 11 months of follow-up. We conclude that LITT might be an effective minimally invasive palliative treatment option for patients with small unresectable HCC.

[Can noninvasive gadolinium 3D MR subtraction angiography of visceral arteries replace conventional intra-arterial catheter angiography?]. / Kann die nichtinvasive Gadolinium 3D-MR-Subtraktionsangiographie der Viszeralarterien die konventionelle intraarterielle Katheterangiographie ersetzen?

Classic catheter angiography is compared with 3D gadolinium MR angiography for evaluation of the vascular anatomy of the celiac trunk, liver supplying arteries, and the portal venous system. Based on 10 patients, this study shows the value of this new non-invasive method of angiography for the diagnosis of visceral vascular anatomy. For this diagnosis MR angiography is expected to replace conventional angiography in the near future.

[Phase-contrast MR angiography of the lower extremity. Comparison of methods and clinical application]. / Phasenkontrast-MR-Angiographie der unteren Extremität. Methodenvergleich und klinische Anwendung.

PURPOSE: To investigate whether phase-contrast MRA is a clinically suited approach to examine arteries of the pelvis and lower extremities. METHODS: The study was divided into two parts, a volunteer study and patient study. Three MRA techniques-2D TOF with venous saturation, 3D magnitude contrast and 2D phase contrast with ECG triggering-were intraindividually compared in 15 volunteers and evaluated by three blinded readers. Subsequently, a total of 230 vessel segments of 45 MRA studies using ECG-triggered phase contrast were compared with intraarterial DSA. All vessel segments were scored by three blinded readers using a five-point scale with DSA serving as the gold standard. RESULTS: ECG-triggered phase contrast provided better image quality than the other MRA techniques as assessed by the Friedman test. Clinical studies demonstrated a significant correlation of DSA and MRA as assessed by the Spearman correlation and kappa statistics for individual readers. CONCLUSION: MRA of the pelvis and lower extremities may be performed with 2D ECG-triggered phase-contrast MRA within a reasonable time frame (< 30 min). MRA slabs provide orientation similar to that with DSA projections and good to very good correlation of vessel pathology as shown by kappa statistics.

Assessment of reperfusion injury by means of MR contrast agents in rat liver.

The purpose of this study was to investigate whether extracellular MR contrast agents or intracellular liver-specific MR contrast agents may enable the assessment of liver reperfusion injury. Ischemia-related reperfusion was induced in 32 rats using Pringle's maneuver. Pringle's maneuver consisted of cross-clamping of the complete hepatoduodenal ligament for 45 minutes followed by 90 minutes of reperfusion. Two extracellular (gadopentetate dimeglumine and gadobutrol) and two intracellular gadoxetic acid and SH U 555 A) MR contrast agents were evaluated as model agents. Control animals and animals with liver ischemia were used to calculate changes in liver signal enhancement after Pringle's maneuver. Significant changes in liver signal after reperfusion injury were observed only with reticuloendothelial system (RES)-specific SH U 555 A. Liver signal enhancement after Pringle's maneuver with RES-specific SH U 555 A was decreased by 25.4% as compared with the control group. RES-specific contrast agents such as SH U 555 A seem to be more sensitive to ischemia-related dysfunction of the liver than hepatobiliary contrast agents such as gadoxetic acid or extracellular gadolinium chelates at different concentrations because Kupffer cells are more sensitive to liver ischemia than hepatocytes.

Artificially produced cartilage lesions in small joints: detection with optimized MRI-sequences.

The purpose of this study was to evaluate different magnetic resonance imaging (MRI) pulse sequences in the detection of artificial cartilage lesions in small joints using an animal model. A total of 32 artificial cartilage lesions were created in the knee joints of 20 rabbits. Twenty lesions were produced 4 weeks and 12 lesions 1 h before the MRI examination, performed in an extremity coil at 1.0 T. All joints were examined with five imaging sequences: (1) a conventional T1-weighted spin-echo (SE)-sequence (repetition time [TR] 600 ms, echo time [TE] 15 ms), (2) a T2-weighted turbo-SE-sequence (TR 2000 ms, TE 85 ms), (3) a two-dimensional (2D) gradient echo (GE)-sequence (TR 440 ms, TE 10 ms, flip angle 60 degrees) and (4,5) two three-dimensional (3D) GE-sequences (TR 40 ms, TE 7 ms, flip angle 40 degrees, with fat suppression (FS) and TR 30 ms, TE 9 ms, flip angle 40 degrees). Two examinations had to be excluded because of insufficient image quality and the remaining examinations were analyzed by two experienced radiologists. The MRI images were correlated with the pathologic findings and anatomical structures were scored according to a 5-level scale. Direct comparison of the pathological and MRI findings showed that 19 of the 30 artificially induced cartilage lesions were detected with the FS 3D GE-sequence, 13 with the 2D GE-sequence, 11 with the 3D GE-sequence, 3 with the T1-weighted SE-sequence, and 2 with the T1-weighted SE-sequence. The highest percentage of artificial cartilage lesions was demonstrated using a fat-suppressed 3D GE-sequence. However, the analysis of cartilage defects in small joints with optimized sequences as well as clinical routine hardware and software had limitations. Therefore a pilot study was performed analyzing newly developed high resolution FS 3D GE images obtained from 5 rabbit knees with 10 cartilage lesions at 1.5 T. Two sequences were used with 1.0 and 0.5 mm slice thickness, a matrix of 256 x 256 and 512 x 256 and a field of view of 12 x 6 and 8 x 6 cm. In this small subset detection rates were substantially higher than in the 30 rabbit knees examined before.

Brain imaging: reduced sensitivity of RARE-derived techniques to susceptibility effects.

OBJECTIVE: Our goal was to evaluate the decreased sensitivity of RARE-derived pulse sequences to susceptibility effects. MATERIALS AND METHODS: A variety of RARE-derived T2-weighted fast SE echo (FSE) sequences with echo trains from 6 to 16 were compared with conventional SE (CSE) sequences by means of MRI in phantoms (iron oxides), volunteers (n = 10), and patients (n = 13) with old hemorrhagic brain lesions. All experiments were performed on a 1.5 T clinical MR system (Magnetom SP 4000; Siemens AG, Erlangen, Germany) with constant imaging parameters. Contrast-to-noise ratios (CNRs) of tubes doped with iron oxides at different concentrations and brain areas with physiological iron deposition (red nucleus, substantia nigra) were calculated for CSE and FSE pulse sequences. Areas of old brain hemorrhage were analyzed for lesion conspicuity by blinded analysis with CSE as an internal standard. RESULTS: CNR of iron oxide tubes (TE 90 ms, CSE 45.0 +/- 3.5, FSE 16 echo trains 28.5 +/- 3.1; p < or = 0.01) and iron-containing brain areas decreased with increasing echo trains of FSE sequences. A significantly lower number of old hemorrhagic brain lesions was visible in patients scanned with FSE sequences (6 echo trains: n = 28; 16 echo trains; n = 26) than CSE (n = 40). CONCLUSION: Our results demonstrate that the sensitivity of RARE-derived techniques to susceptibility effects is significantly decreased compared with CSE. CSE sequences or GE sequences should still be preferred in patients with a history of seizures or intracranial hemorrhage.

[Fast and ultra-fast MRI of the brain]. / Schnelle und ultraschnelle MRT des Gehirns.

Fast spin-echo sequences, which are based on the RARE sequence, accelerate MRI significantly. The basic principle of fast- or turbo-spin-echo sequences (FSE, TSE), as well as of the gradient-and-spin-echo sequences (GRASE, TGSE), is the sampling of multiple independently phase-encoded echos after each excitation. The basic principles of these sequences and the potentials and limitations of their clinical application are discussed. Their main advantage is a significant reduction of the time for data acquisition, which allows either a reduction of imaging time or high-resolution images even with T2-weighting. The fast sequences provide all possibilities of contrast variation and of preparation pulses such as fat saturation or water suppression. Despite some restrictions, of which reduced susceptibility is clinically relevant, they can replace conventional spin-echo sequences in brain imaging.