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  • 1
    Electronic Resource
    Electronic Resource
    Hepatic MR imaging: comparison of RARE derived sequences with conventional sequences for detection and characterization of focal liver lesions (1996)
    Springer
    Abdominal imaging 21 (1996), S. 427-432 
    Details
    ISSN: 1432-0509
    Keywords: Key words: MRI—Hepatic imaging—RARE—Detection—Characterization.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Background: We compared two T2-weighted turbo spin echo (TSE) sequences with a T2-weighted conventional SE (CSE) sequence to determine whether sequences derived from rapid acquisition with relaxation enhancement such as TSE could replace CSE for the detection and subsequent characterization of focal liver lesions. Methods: A total of 55 consecutive patients with 107 liver lesions underwent magnetic resonance imaging examinations at 1.5 Tesla, with a constant imaging protocol. TSE pulse sequences were acquired with eight echo trains (repetition time [TR], 4718 ms; echo time [TE], 90 ms; acquisition time [TA], 4.03 min; and a symmetric k-space ordering scheme) and 11 echo trains (TR, 4200 ms; TE, 140 ms; TA, 4.40 min; and an asymmetric k-space ordering scheme) and compared with CSE (TR, 2300 ms; TE, 45/90 ms; TA, 9.53 min). Images were analyzed qualitatively by scoring image quality and artifacts and counting focal liver lesions by independent reading with consensus obtained for discrepancies. Quantitative analysis was performed by measuring signal-to-noise (S/N), contrast-to-noise (C/N), and tumor–liver signal intensity (T/L) ratios. Results: T2-weighted TSE sequences provided better subjective image quality and reduced artifacts as compared with the T2-weighted CSE sequence. CSE and TSE sequences exhibited no statistically significant differences in liver S/N, lesion–liver C/N (CSE TE, 90 ms: 18.6 ± 14.0; TSE TE, 90 ms: 16.5 ± 12.9) and the detectability of focal liver lesions. Heavily T2-weighted TSE with a TE of 140 ms allowed correct characterization of focal liver lesions based on a T/L ratio of 3.0 in 84% of patients. Conclusions: T2-weighted TSE sequences are as suited as CSE for the detection (TE, 90 ms), and appear to be superior for the characterization (TE, 140 ms), of focal hepatic lesions. Whether a single sequence, such as a double-echo TSE or a single-echo TSE sequence with a TE between 110 and 120 ms, might perform both functions as well or better than CSE is unknown. However, because of time savings, TSE eventually may be preferred over CSE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002619900097
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  • 2
    Electronic Resource
    Electronic Resource
    Book reviews (1996)
    Springer
    European radiology 6 (1996), S. 357-357 
    Details
    ISSN: 1432-1084
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00180610
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Study of susceptibility-induced artefacts in GRASE with different echo train length (1998)
    Springer
    European radiology 8 (1998), S. 834-838 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Magnetic resonance imaging ; Brain hemorrhage ; FSE ; GRASE ; Susceptibility artefact
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. 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≤ 0.01). Qualitative analysis confirmed these measurements. FSE with an ETL of 5 demonstrated significantly stronger susceptibility effects than their GRASE counterpart with an ETL of 21. The results demonstrate that GRASE sequences do not necessarily compensate for the reduced sensitivity of FSE to susceptibility effects. The complex signal behavior of GRASE makes conventional SE, gradient echo, or FSE sequences containing shorter echo trains preferable when patients with intracranial hemorrhage are clinically evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050481
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  • 4
    Electronic Resource
    Electronic Resource
    Non-invasive vascular imaging of peripheral vessels (1998)
    Springer
    European radiology 8 (1998), S. 858-872 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Arteries ; Veins ; Non-invasive imaging ; Ultrasound ; Doppler studies ; Computed tomography angiography ; Magnetic resonance angiography ; Contrast agents ; Vascular studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of this review is to describe recent advances in non-invasive vascular imaging techniques and to discuss their current clinical applications for imaging of peripheral vessels. Principles for applying ultrasound, CT angiography (CTA), and magnetic resonance angiography (MRA) for non-invasive imaging of peripheral arteries and veins are presented. Clinical applications are reviewed for different vascular diseases, therapy planning, and follow-up studies. Conventional Doppler and color duplex sonography are the most cost-effective procedures to detect or rule out peripheral arterial occlusive disease (PAOD) and to provide specific recommendations for therapy. In the near future, contrast-enhanced MRA (CE MRA) with additional axial two-dimensional time-of-flight studies to search for non-anatomic runoff will replace diagnostic intra-arterial digital subtraction angiography (DSA) for planning of reconstructive surgery with acquisition slabs displaying projections similar to intra-arterial DSA. Color duplex sonography should also be the first non-invasive technique applied for the detection of peripheral aneurysms. Preoperative or preinterventional therapy planning of aneurysms may be performed by CTA or CE MRA. Compression ultrasound is the imaging procedure of choice in deep venous thrombosis (DVT). In the preoperative assessment of venous incompetence, color duplex sonography is the imaging technique which is sufficient in most cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050483
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  • 5
    Electronic Resource
    Electronic Resource
    Phase-contrast MR angiography of peripheral arteries: technique and clinical application (1999)
    Springer
    European radiology 9 (1999), S. 122-127 
    Details
    ISSN: 1432-1084
    Keywords: Key words: MR-Angiography (MRA) ; Phase-Contrast-MRA (PC-MRA) ; Peripheral Arterial Occlusive Disease (PAOD) ; Stenoses ; Occlusions ; Aneurysms ; Postsurgical follow-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. This articles describes Phase-Contrast-MRA (PC-MRA) techniques and their current clinical applications for peripheral arteries based on more than 250 clinical MRA studies performed at two institutions. PC-MRA depends on phase shifts caused by blood flow and thus this technique permits the use of coronal or sagittal slice orientations with large FOV's along the direction of the vessel of interest. Clinical applications focus on patients with peripheral arterial occlusive disease (PAOD) describing the role and limitations of PC-MRA for the work-up of stenoses, occlusions, aneurysms, and postsurgical follow-up. Recommendations for clinical routine are provided. A combined MR angiographic approach with various MRA techniques depending on the vessel segment to be imaged, PC-flow velocity measurements, and high-resolution scans of the vessel wall may turn out to be diagnostically effective and provide a comprehensive test for PAOD within the near future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050642
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  • 6
    Electronic Resource
    Electronic Resource
    Clinical applications of functional MRI at 1.0 T: motor and language studies in healthy subjects and patients (1999)
    Springer
    European radiology 9 (1999), S. 211-220 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Functional MRI ; 1.0 Tesla ; Motor studies ; Language studies ; Presurgical mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. In this article we describe clinical applications of functional MRI (fMRI) at 1.0 T. All experiments were performed on a commercially available 1.0-T system (Magnetom Impact Expert, Siemens AG, Erlangen, Germany) using a blood oxygen level-dependent (BOLD)-sensitive multi-slice EPI technique (TE 66 ms, 4 mm slice thickness, 210 mm field of view, 64 × 64 acquisition matrix). Different paradigms for localization of the motor cortex and for language lateralization were tested in healthy subjects and patients. Methodological considerations concerning the development of the paradigms are also described. In all healthy subjects, motor activation elicited BOLD signal changes in the sensorimotor cortex, permitting identification of primary motor and sensory cortical areas. Furthermore, focal activation of different cortical areas by a language task was possible in 6 of 10 subjects. Nineteen motor studies were performed in 18 patients with supratentorial lesions, in most cases prior to neurosurgical procedures. In 14 studies, fMRI results demonstrated the localization of the motor hand areas relative to the lesion. The results proved valuable for preoperative planning and contributed to therapeutical decisions. We conclude that functional MRI for clinically relevant applications, such as localization of motor and language function, is feasible even at a field strength of 1.0 T without dedicated equipment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050658
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  • 7
    Electronic Resource
    Electronic Resource
    Book reviews (1996)
    Springer
    European radiology 6 (1996), S. 155-155 
    Details
    ISSN: 1432-1084
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00181134
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Application of a stable cell culture assay for the functional assessment of novel MR contrast agents (1997)
    Springer
    European radiology 7 (1997), S. 527-531 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Cell culture ; Hepatocytes ; MR receptor agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of this study was to apply a new cell culture assay that preserves hepatocyte orientation and differentiation for screening of MR contrast agents with hepatocyte specificity. Cultured hepatocytes were sandwiched between two layers of collagen, preserving both hepatocyte function and morphology over a prolonged period of time. Plain and rhodaminated monocrystalline iron-oxide particles (MION and MION-rh) and asialoglycoprotein receptor-specific rhodaminated asialofetuin coupled to MION (MION-ASF-rh) were prepared. Dose-dependent competition experiments of these agents were performed with D( + )-galactose to determine the specificity of galactose-mediated cell uptake. To assess the impact of cell integrity on cell uptake dose-dependent functional experiments with two hepatotoxins (ethanol and CCl4) were performed. Normal cell cultures showed significantly higher fluorescent-light emission after incubation with hepatocyte-directed ASF-MION-rh than after incubation with MION-rh. Competition experiments of ASF-MION with galactose showed a dose-dependent decrease in calibrated fluorescent-light emission. Cell cultures treated with hepatotoxins demonstrated a dose-dependent reduction in calibrated fluorescent-light emission following incubation with ASF-MION-rh. The validated assay system allows assessment not only of hepatocyte specificity, but also of hepatocyte damage. Because the assay can be applied to cells from any species (rat, pig, human), it may represent an ideal test system prior to clinical trials of new hepatocyte-directed MR contrast agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050197
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  • 9
    Electronic Resource
    Electronic Resource
    Hepatic MRI with SPIO: detection and characterization of focal liver lesions (1998)
    Springer
    European radiology 8 (1998), S. 1198-1204 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Iron oxides ; Liver ; SPIO ; USPIO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. A variety of parenterally administered iron oxides have been developed for contrast-enhanced MRI of the liver. Two different classes of iron oxides are currently clinically approved or in phase 3 trials: superparamagnetic iron oxides (SPIO) with a high R2/R1 relaxivity ratio and short blood half-life (AMI-25 and SH U 555 A), and ultrasmall paramagnetic iron oxides (USPIO) with a lower R2/R1 relaxivity ratio and longer blood half-life (AMI-227). All iron oxides significantly increase tumor-to-liver contrast and allow detection of more lesions than unenhanced MRI on T2-weighted images at a field strength of 0.2–1.5 T. Malignant lesions without phagocytic cells exhibit constant signal on T2-weighted accumulation phase images with all three iron oxides. All iron oxides cause a signal decrease of benign lesions with either phagocytic cells or a significant blood pool on T2-weighted accumulation phase images. The signal decrease of benign lesions is proportional to the Kupffer cell activity or tumor vascularity and is useful for lesion characterization. Another enhancement feature for the differentiation of benign from malignant lesions is ring enhancement of malignant lesions (metastases) on T1-weighted enhanced images either during the perfusion phase with SH U 555 A or during the accumulation phase with AMI-227, which is attributed to the blood pool effects of the compounds. Differentiation of lesions and vessels is easier on enhanced images with angiographic effects than on unenhanced images. Iron oxides improve the quality of two-dimensional MR angiography techniques of the portal venous system by decreasing background signal (liver tissue with all iron oxides) and increasing intravascular signal (AMI-227). The use of iron oxides for hepatic MRI provides an alternative to the existing multistep diagnosis with CT, CT portography, MRI and biopsy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050535
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of potential gastrointestinal contrast agents for echoplanar MR imaging (1993)
    Springer
    European radiology 3 (1993), S. 487-492 
    Details
    ISSN: 1432-1084
    Keywords: MR imaging ; Echoplanar imaging ; Gastrointestinal contrast agents ; Bowel lumen signal ; Susceptibility artifacts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Although the diagnostic application of echoplanar imaging (EPI) has until now been limited, recent technical advances provide anatomic resolution and signal-to-noise ratios comparable to that of conventional MR imaging. The purpose of this study was to investigate approved aqueous gastrointestinal contrast agents for use in abdominal EPI. Conventional and echoplanar MR imaging experiments were performed with 1.0 Tesla whole body systems. Phantom measurements of Gastrografin, barium sulfate suspension, oral gadopentetate dimeglumine, water, and saline were performed. Signal intensity (SI) of aqueous oral barium sulfate and iodine based CT contrast agents was lower on conventional spin-echo (SE), Flash, and Turbo-Flash images than on EP images. The contrast agents exhibited higher SI on T2-weighted SE PE images and TI-time dependence on inversion recovery EP-images. The barium sulfate suspension was administered in volunteers to obtain information about bowel lumen enhancement and susceptibility artifacts. Oral administration of the aqueous barium sulfate suspension increased bowel lumen signal and reduced susceptibility artifacts. Approved aqueous gastrointestinal contrast media or flavored saline with long relaxation times may serve as safe, simple, and effective gastrointestinal contrast agents in abdominal EPI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169595
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