Ulrike I Attenberger

Publications of Ulrike I Attenberger

• Magnetic Resonance Evaluation of Renal Artery Stenosis in a Swine Model: Performance of Low-Dose Gadobutrol Versus Gadoterate Meglumine in Comparison With Digital Subtraction Intra-Arterial Catheter Angiography.

  Authors: John N Morelli, Val M Runge, Fei Ai, Wei Zhang, Xiaoming Li, Peter Schmitt, Gary McNeal, Matthew Miller, Mark Lennox, Oliver Wusten, Stefan O Schoenberg, Ulrike I Attenberger

  Investigative radiology. 04/2012;

  PURPOSE: The aim of this study was to compare low-dose imaging with gadobutrol and gadoterate meglumine (Gd-DOTA) for evaluation of renal artery stenosis with 3-T magnetic resonance angiography (MRA)PURPOSE: The aim of this study was to compare low-dose imaging with gadobutrol and gadoterate meglumine (Gd-DOTA) for evaluation of renal artery stenosis with 3-T magnetic resonance angiography (MRA) in a swine model. METHOD AND MATERIALS: A total of 12 experimental animals were evaluated using equivalently dosed gadobutrol and Gd-DOTA for time-resolved and static imaging. For time-resolved imaging, the time-resolved imaging with stochastic trajectories (TWIST) technique (temporal footprint, 4.4 seconds) was used; a dose of 1 mL of gadobutrol was injected at 2 mL/s and a dose of 2 mL of Gd-DOTA was injected at both 2 and 4 mL/s. For a separate static acquisition, doses were doubled. The static scans were used for stenosis gradation and the time-resolved scans for comparison of enhancement dynamics, signal-to-noise ratio (SNR), and qualitative assessments. RESULTS: The average magnitude of difference in the stenosis measurements with static gadobutrol scans relative to digital subtraction intra-arterial catheter angiography (mean [SD], 7.4% [5.6%]) was less than with both the 2 mL/s (10.6% [6.2%]) and 4 mL/s (11.5% [7.8%]) Gd-DOTA MRA protocols. On time-resolved scans, peak signal-to-noise ratio was greatest with the gadobutrol protocol (P < 0.05), and the gadobutrol TWIST scan was preferred to the TWIST Gd-DOTA scan in terms of image quality and stenosis visualization in every case for every reader. CONCLUSION: Low-dose gadobutrol (∼0.05 mmoL/kg) contrast-enhanced MRA results in improved accuracy of renal artery stenosis assessments relative to equivalently dosed Gd-DOTA at 3 T.

• Renal BOLD-MRI does not reflect renal function in chronic kidney disease.

  Authors: Henrik J Michaely, Linda Metzger, Stefan Haneder, Jan Hansmann, Stefan O Schoenberg, Ulrike I Attenberger

  Kidney international. 01/2012;

  Renal blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) is a noninvasive fast technique to characterize renal function. Here we evaluated the impact of renal function on theRenal blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) is a noninvasive fast technique to characterize renal function. Here we evaluated the impact of renal function on the relaxation rate (R2(*)) in the cortex and medulla to provide baseline data for further use of renal BOLD-MRI. This parameter was evaluated in 400 patients scheduled for abdominal imaging who underwent transversal blood oxygen level-dependent measurements with a multi-echo gradient-echo sequence with 12 echo times. The loss of phase coherence (T2(*)) maps were generated in which kidney regions of interest were selected to differentiate the medulla and cortex, and R2(*) was equated to 1/T2(*). Individual R2(*) values were, in turn, correlated to the eGFR (MDRD formula of 280 patients with available serum creatinine measurements), age, and gender each for 1.5 and 3.0 T field-strength scans of 342 patients. At both the field strengths, no significant differences in R2(*) of the cortex and medulla were found between patient gender, age, eGFR, or between different stages of chronic kidney disease determined using the KDOQI system. Thus, BOLD-MRI of a non-specific patient population failed to discriminate between the patients with various stages of chronic kidney disease.Kidney International advance online publication, 11 January 2012; doi:10.1038/ki.2011.455.

• Combined large field-of-view MRA and time-resolved MRA of the lower extremities: Impact of acquisition order on image quality.

  Authors: Philipp Riffel, Stefan Haneder, Ulrike I Attenberger, Joachim Brade, Stefan O Schoenberg, Henrik J Michaely

  European journal of radiology. 12/2011;

  PURPOSE: Different approaches exist for hybrid MRA of the calf station. So far, the order of the acquisition of the focused calf MRA and the large field-of-view MRA has not been scientificallyPURPOSE: Different approaches exist for hybrid MRA of the calf station. So far, the order of the acquisition of the focused calf MRA and the large field-of-view MRA has not been scientifically evaluated. Therefore the aim of this study was to evaluate if the quality of the combined large field-of-view MRA (CTM MR angiography) and time-resolved MRA with stochastic interleaved trajectories (TWIST MRA) depends on the order of acquisition of the two contrast-enhanced studies. METHODS: In this retrospective study, 40 consecutive patients (mean age 68.1±8.7 years, 29 male/11 female) who had undergone an MR angiographic protocol that consisted of CTM-MRA (TR/TE, 2.4/1.0ms; 21° flip angle; isotropic resolution 1.2mm; gadolinium dose, 0.07mmol/kg) and TWIST-MRA (TR/TE 2.8/1.1; 20° flip angle; isotropic resolution 1.1mm; temporal resolution 5.5s, gadolinium dose, 0.03mmol/kg), were included. In the first group (group 1) TWIST-MRA of the calf station was performed 1-2min after CTM-MRA. In the second group (group 2) CTM-MRA was performed 1-2min after TWIST-MRA of the calf station. The image quality of CTM-MRA and TWIST-MRA were evaluated by 2 two independent radiologists in consensus according to a 4-point Likert-like rating scale assessing overall image quality on a segmental basis. Venous overlay was assessed per examination. RESULTS: In the CTM-MRA, 1360 segments were included in the assessment of image quality. CTM-MRA was diagnostic in 95% (1289/1360) of segments. There was a significant difference (p<0.0001) between both groups with regard to the number of segments rated as excellent and moderate. The image quality was rated as excellent in group 1 in 80% (514/640 segments) and in group 2 in 67% (432/649), respectively (p<0.0001). In contrast, the image quality was rated as moderate in the first group in 5% (33/640) and in the second group in 19% (121/649) respectively (p<0.0001). The venous overlay was disturbing in 10% in group 1 and 20% in group 2 (p=n.s.). CONCLUSION: If a combined hybrid MRA approach with large field-of-view and time-resolved MRA is acquired the large field-of-view MRA should be acquired first in order for optimal image quality.

• DCE-MRI of the human kidney using BLADE: A feasibility study in healthy volunteers.

  Authors: Florian Lietzmann, Frank G Zöllner, Ulrike I Attenberger, Stefan Haneder, Henrik J Michaely, Lothar R Schad

  Journal of magnetic resonance imaging : JMRI. 11/2011;

  PURPOSE: To evaluate the degree of motion compensation in the kidney using two different sampling methods, each in their optimized settings: A BLADE k-space acquisition technique and a routinely usedPURPOSE: To evaluate the degree of motion compensation in the kidney using two different sampling methods, each in their optimized settings: A BLADE k-space acquisition technique and a routinely used kidney perfusion acquisition scheme (TurboFLASH). MATERIALS AND METHODS: Dynamic contrast enhanced magnetic resonance examinations were performed in 16 healthy volunteers on a 3 Tesla MR-system with two parameterizations of the BLADE sequence and the standard reference acquisition scheme. Signal intensity enhanced time curves were analyzed with a mathematical model and a widely published separable compartment model on cortex regions to assess robustness versus motion artifacts. RESULTS: BLADE-measurements with a strip-width of 32 lines constituted the smallest mean values for the sum of squared errors (6065 ± 4996) compared with the measurement with a strip-width of 64 lines (13849 ± 14079) or the standard TurboFLASH (11884 ± 8076). Calculations concerning goodness of the fit of the applied compartment model yielded an overall average of the Akaike Fit Error of 732 ± 141 for BLADE (646 ± 149 for a strip-width of 32 lines, 816 ± 53 for 64 lines) and 1626 ± 303 for the TurboFLASH (TFL) sequence. CONCLUSION: We demonstrated that renal dynamic contrast enhanced magnetic resonance imaging using BLADE k-space sampling with a strip-width of 32 is significantly less sensitive to motion than a widely published Turbo-Flash sequence with nearly similar parameters. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

• Assessment of the kidneys: magnetic resonance angiography, perfusion and diffusion.

  Authors: Ulrike I Attenberger, John N Morelli, Stefan O Schoenberg, Henrik J Michaely

  Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance. 11/2011; 13:70.

  Renal magnetic resonance (MR) imaging has undergone major improvements in the past several years. This review focuses on the technical basics and clinical applications of MR angiography (MRA) withRenal magnetic resonance (MR) imaging has undergone major improvements in the past several years. This review focuses on the technical basics and clinical applications of MR angiography (MRA) with the goal of enabling readers to acquire high-resolution, high quality renal artery MRA. The current role of contrast agents and their safe use in patients with renal impairment is discussed. In addition, an overview of promising techniques on the horizon for renal MR is provided. The clinical value and specific applications of renal MR are critically discussed.

• Special issue "vascular imaging".

  Authors: Henrik J Michaely, Ulrike I Attenberger, Stefan O Schoenberg

  European journal of radiology. 10/2011; 80(1):1.

• Gadofosveset: parameter optimization for steady-state imaging of the thoracic and abdominal vasculature.

  Authors: Stefan Haneder, Ulrike I Attenberger, Andreas Biffar, Olaf Dietrich, Christian Fink, Stefan O Schoenberg, Henrik J Michaely

  Investigative radiology. 06/2011; 46(11):678-85.

  Comparison of 3 optimized pulse sequences for thoracoabdominal contrast-enhanced magnetic-resonance angiography by signal-to-noise measurements and time-dependent T1 mapping in the steady state afterComparison of 3 optimized pulse sequences for thoracoabdominal contrast-enhanced magnetic-resonance angiography by signal-to-noise measurements and time-dependent T1 mapping in the steady state after injection of 0.03 mmol/kg BW gadofosveset. After institutional review board approval, 15 healthy volunteers (19-46 years, mean age: 31.5 years) were included in this prospective, intraindividual comparison study. All examinations were performed at 1.5 T. Three pulse sequences: volume interpolated breath-hold examination (VIBE) sequences as VIBESEMI (echo time [TE]: 1.64 milliseconds, repetition time [TR]: 3.77 milliseconds, FA: 15 degrees, voxel size: 1.2 × 1.2 × 1.2 mm) with short TR, VIBEOPT (TE: 2.2 milliseconds, TR: 5.2, FA: 15 degree, voxel size: 1.2 × 1.2 × 1.2 mm) with long TR, and a typical 3-dimensional fast low angle shot (FLASH) sequence (TE: 1.39 milliseconds, TR: 3.77 milliseconds, FA: 25 degree, voxel size: 1.0 × 0.8 × 1.0 mm) were repeated 10, 20, 30, and 40 minutes after the injection of 0.03 mmol/kg BW gadofosveset (mean dose: 9.7 mL). Mean signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were computed for the aorta and the inferior vena cava (IVC). Three-dimensional gradient echo sequences with variable flip angles were performed for T1 mapping 0 to 50 minutes postinjection (p.i.). Additional phantom measurements were performed to compare the sequences. Significantly higher SNR values of the FLASH were found at every point compared with VIBEOPT (P = 0.002-P = 0.004), but only 10, respectively, 20 minutes p.i. to VIBESEMI. No significant differences of SNR were obtained between VIBESEMI and VIBEOPT. In the aorta, the maximal percentage gain of SNR was 29.2% for 3D-FLASH compared with VIBESEMI. Similar, but mostly not significant, results were obtained regarding the SNR in the IVC with the 3D-FLASH sequence yielding higher SNR versus both comparators (P = 0.007-P = 0.466). Except 10 minutes p.i., CNR analysis yielded higher values for the VIBESEMI versus both comparators in the aorta as well as in the IVC. No statistical significant difference was found for the VIBESEMI versus the 3D-FLASH sequence in all comparisons. Regarding the phantom measurements, statistically significant higher SNR was found for the VIBESEMI versus the 3D-FLASH. The T1 time in the aorta decreased p.i. from 1227 ± 383 milliseconds to 141 ± 27 milliseconds and showed over the time a slow reincrease to 175 ± 29 milliseconds at 50 minutes p.i. Ten to 30 minutes after injection of gadofosveset, a relatively constant longitudinal relaxation is given. In this steady state, no additional improvements were obtained by theoretically optimized sequence parameters in the VIBEOPT with a longer TR.

• Peripheral MRA with continuous table movement: imaging speed and robustness compared to a conventional stepping table technique.

  Authors: Katrin Koziel, Ulrike I Attenberger, Kai Lederle, Stefan Haneder, Stefan O Schoenberg, Henrik J Michaely

  European journal of radiology. 02/2011; 80(2):537-42.

  To investigate the potential of continuous table movement (CTM)-MRA for reduction of acquisition time and to evaluate the image quality in comparison to conventional stepping table (CST) MRA. TheTo investigate the potential of continuous table movement (CTM)-MRA for reduction of acquisition time and to evaluate the image quality in comparison to conventional stepping table (CST) MRA. The data of 82 patients were included in this retrospective, IRB-approved study. All patients underwent peripheral MRA at our institution. 41 consecutive patients were examined with a CST-MRA at a 1.5 T MR system. 41 different consecutive patients were examined with a CTM-MRA at 3.0 T MR system. Image quality was assessed by two independent radiologists in consensus on a 4-point Likert-type scale. Descriptive statistics and t-tests were used to compare image acquisition time of CST-MRA to that of CTM-MRA with and without additional time-resolved imaging of the feet using the TWIST technique. Additionally, acquisition time was compared in a subgroup of the fastest 50%. The mean imaging time for the CTM-MRA was 34% less than with the CST-MRA (18.2 min vs. 27.5 min; p<0.0001). Even with inclusion of the TWIST sequence the combined CTM-/TWIST-MRA protocol was 26% faster (20.3 min vs. 27.5 min; p<0.0001). The image quality was slightly better with CTM-MRA (CTM-MRA mean score 3.3±0.5, mean score CST-MRA 2.9±0.6). Venous overlay was significantly lower using the CTM-MRA approach (CTM-MRA mean score 2.8±0.4; CST-MRA mean score 2.2±0.7; p<0.0001). CTM-MRA is on average 30% faster than a comparable CST-MRA protocol with equal image quality. Even when adding an additional time-resolved-MRA of the calf station the CTM-MRA protocol is still 26% faster. In conclusion, this study proves that CTM-MRA further improves MRA by reducing user interference and image acquisition times and hence allowing to increase the clinical throughput.

• Imaging of non-atherosclerotic aneurysmal disease.

  Authors: Ulrike I Attenberger, Henrik J Michaely, Stefan O Schoenberg, Johannes Rieger

  European journal of radiology. 02/2011; 80(1):41-9.

  Atherosclerotic aneurysms account for about 95% of all aneurysms. This overview concentrates on the 5% leftover, which however represents a heterogenic group of aneurysms with a wide range ofAtherosclerotic aneurysms account for about 95% of all aneurysms. This overview concentrates on the 5% leftover, which however represents a heterogenic group of aneurysms with a wide range of different pathogenesis. Thus, therapy is not exclusively restricted to the exclusion of the aneurysm. In non-atherosclerotic aneurysmal disease various additional therapeutic strategies are included such as chemotherapy, anti-inflammatory therapy and embolisation procedures. Diagnosis, therapeutic decision making and even therapy itself to a growing extent depends on adequate (pretherapeutic) imaging and therefore radiologic expertise. This review describes the most common forms of non-atherosclerotic aneurysms and focuses on their pathogenesis, potential diagnostic approaches and therapy options.

• Magnetic resonance angiography (MRA) of the calf station at 3.0 T: intraindividual comparison of non-enhanced ECG-gated flow-dependent MRA, continuous table movement MRA and time-resolved MRA.

  Authors: Stefan Haneder, Ulrike I Attenberger, Philipp Riffel, Thomas Henzler, Stefan O Schoenberg, Henrik J Michaely

  European radiology. 01/2011; 21(7):1452-61.

  To compare 3D non-enhanced ECG-gated inflow-dependent MRA (NE-MRA) vs. continuous table movement (CTM) MR-angiography and time-resolved TWIST-MRA in the calf station at 3.0 T in a clinical patientTo compare 3D non-enhanced ECG-gated inflow-dependent MRA (NE-MRA) vs. continuous table movement (CTM) MR-angiography and time-resolved TWIST-MRA in the calf station at 3.0 T in a clinical patient collective. 36 patients (27 male/9 female, 66.1 ± 14.4 years) with PAOD (stage II-IV) underwent during a single MRI: NE-MRA, contrast-enhanced CTM-MRA and TWIST-MRA with a single dose of a gadolinium-based contrast agent. The image quality (IQ) and the degree of stenoses were rated on a four-point scale. Positive (PPV) and negative predictive values (NPV), sensitivity (SS) and specificity (SP) for stenoses detection were calculated for NE-MRA vs. CTM-MRA and vs. TWIST-MRA. Values were obtained for overall graduation of wall changes and for severe stenoses (>70%). With NE-MRA 122/288 segments were not assessable. Compared with CTM-MRA and TWIST-MRA the IQ was significantly inferior (p < 0.0001 to p = 0.0426). CTM-MRA/TWIST-MRA detected stenoses in 44.9%/46.1% of the segments, NE-MRA in 53.5%. SS/NPV of the NE-MRA ranged from 97.8 to 100%. The SP and PPV ranged from 72.7 to 85.5% and 66.7 to 78.2%. Contrast-enhanced MRA techniques are superior to NE-MRA regarding IQ and correct identification of stenoses. If technically successful, NE-MRA is characterised by high NPV and overestimation of the degree of stenoses.

• Retrospective respiratory triggering renal perfusion MRI.

  Authors: Ulrike I Attenberger, Steven P Sourbron, Henrik J Michaely, Maximilian F Reiser, Stefan O Schoenberg

  Acta radiologica (Stockholm, Sweden : 1987). 12/2010; 51(10):1163-71.

  artifacts of respiratory motion are one of the well-known limitations of dynamic contrast-enhanced MRI (DCE-MRI) of the kidney. to propose and evaluate a retrospective triggering approach to minimizeartifacts of respiratory motion are one of the well-known limitations of dynamic contrast-enhanced MRI (DCE-MRI) of the kidney. to propose and evaluate a retrospective triggering approach to minimize the effect of respiratory motion in DCE-MRI of the kidney. nine consecutive patients underwent renal perfusion measurements. Data were acquired with a 2D saturation-recovery TurboFLASH sequence. In order to test the dependence of the results on size and location of the manually drawn triggering regions of interest (ROIs), three widely differing triggering regions were defined by one observer. Mean value, standard deviation, and variability of the renal function parameters plasma flow (F(P)), plasma volume (V(P)), plasma transit time (T(P)), tubular flow (F(T)), tubular volume (V(T)), and tubular transit time (T(T)) were calculated on a per-patient basis. the results show that triggered data have adequate temporal resolution to measure blood flow. The overall average values of the function parameters were: 152.77 (F(P)), 15.18 (V(P)), 6,73 (T(P)), 18.50 (F(T)), 35.36 (V(T)), and 117.67 (T(T)). The variability (calculated in % SD from the mean value) for three different respiratory triggering regions defined on a per-patient basis was between 0.81% and 9.87% for F(P), 1.45% and 8.19% for V(P), 0% and 9.63% for T(P), 2.15% and 12.23% for T(F), 0.8% and 17.28% for V(T), and 1.97% and 12.87% for T(T). triggering reduces the oscillations in the signal curves and produces sharper parametric maps. In contrast to numerically challenging approaches like registration and segmentation it can be applied in clinical routine, but a (semi)-automatic approach to select the triggering ROI is desirable to reduce user dependence.

• Evaluation of gadodiamide versus gadobutrol for contrast-enhanced MR imaging in a rat brain glioma model at 1.5 and 3 T.

  Authors: John N Morelli, Val M Runge, Lan Vu, Alan T Loynachan, Ulrike I Attenberger

  Investigative radiology. 12/2010; 45(12):810-8.

  To compare equivalently-dosed (0.1 mmol/kg) gadobutrol (Gadovist) and gadodiamide (Omniscan) in a rat brain glioma model with respect to lesion signal-to-noise (SNR), contrast-to-noise (CNR), andTo compare equivalently-dosed (0.1 mmol/kg) gadobutrol (Gadovist) and gadodiamide (Omniscan) in a rat brain glioma model with respect to lesion signal-to-noise (SNR), contrast-to-noise (CNR), and contrast enhancement (CE) at 1.5 and 3 T. Lesion enhancement with standard-dose gadobutrol in scans performed at 1.5 T was also compared with that of half-dose gadobutrol in scans performed at 3 T. Fifty-four rats were injected with glioma cells via a plastic brain cannula and divided into 3 groups. In the first group, each animal was studied using gadodiamide and gadobutrol, with 24 hours separating injections. The 2 agents were administered in random order at a dose of 0.1 mmol/kg. Each animal was scanned using a 3 T MR system. The procedure for the second group was similar, but scanning was performed at 1.5 T. For the third group, rats were given standard or half-dose gadobutrol and scanned at 1.5 and 3 T, respectively. For all MR examinations, T1-weighted images were obtained precontrast and at 1, 3, 5, 7, and 9 minutes postcontrast administration. At 3 T improvements in SNR, CNR, and CE with gadobutrol ranged from 11.8% to 16.0%, 30.5% to 35.4%, and 27.1% to 31.5%, respectively, and at 1.5 T from 7.0% to 11.1%, 27.1% to 35.8%, and 23.8% to 29.5%, respectively. Differences between these parameters with gadobutrol and gadodiamide were statistically significant (P < 0.0001-0.05) at all time points following contrast administration. In group 3, no significant differences in CNR or CE were found between full dose gadobutrol at 1.5 T and half-dose at 3 T, although SNR was significantly greater (28.5%-35.1%; P < 0.0008) at 3 T. Gadobutrol (Gadovist) demonstrates superior lesion enhancement to equivalently-dosed gadodiamide (Omniscan) in the rat brain glioma model. These results are complemented by the improved observed and theoretical safety profile of the first agent, in particular with regard to nephrogenic systemic fibrosis. The ability to image with half-dose gadobutrol at 3 T without a statistically significant decrease in lesion enhancement, compared with 1.5 T, offers an additional theoretical safety margin and potential cost-savings.

• Peripheral arterial occlusive disease: evaluation of a high spatial and temporal resolution 3-T MR protocol with a low total dose of gadolinium versus conventional angiography.

  Authors: Ulrike I Attenberger, Stefan Haneder, John N Morelli, Steffen J Diehl, Stefan O Schoenberg, Henrik J Michaely

  Radiology. 10/2010; 257(3):879-87.

  To evaluate a peripheral magnetic resonance (MR) angiographic protocol combining continuous table movement (CTM) MR angiography of the entire runoff vasculature with time-resolved (TWIST) 3-T MRTo evaluate a peripheral magnetic resonance (MR) angiographic protocol combining continuous table movement (CTM) MR angiography of the entire runoff vasculature with time-resolved (TWIST) 3-T MR angiography of the calves with a total gadolinium dose of 0.1 mmol per kilogram of body weight. In this retrospective institutional review board-approved study, 31 consecutive patients (22 men, nine women; mean age, 65 years ± 14 [standard deviation]) with peripheral arterial occlusive disease who had undergone a low-dose MR angiographic protocol that consisted of CTM MR angiography (repetition time msec/echo time msec, 2.4/1.0; 21° flip angle; voxel size, 1.2 mm(3); gadolinium dose, 0.07 mmol per kilogram of body weight) and TWIST MR angiography (2.8/1.1; 20° flip angle; voxel size, 1.1 mm(3); temporal resolution, 4.8-5.5 sec, gadolinium dose, 0.03 mmol/kg), as well as digital subtraction angiography (DSA), were included. Two radiologists rated image quality and stenosis degree on four-point scales. The accuracy of stenosis gradation and, specifically, the detection of high-grade stenoses (stenosis of 70%-99%) with CTM MR angiography alone and with the combined protocol were compared with accuracy of stenosis gradation and detection of high-grade stenoses with DSA. Means and standard deviations were calculated for all data. Interobserver agreement was determined with κ statistics. Positive and negative predictive values, sensitivity, specificity, and overall diagnostic accuracy were calculated for CTM MR angiography alone and for the combined protocol. For CTM MR angiography, image quality was good or excellent in 95.9% of vessel segments; for TWIST MR angiography, image quality was good or excellent in 94.3% and 97.8% of vessel segments for readers 1 and 2, respectively. The combined protocol resulted in high overall diagnostic accuracy of more than 80% for detection of stenosis and diagnostic accuracy of 93.5% for detection of high-grade vessel stenosis. Inclusion of TWIST MR angiography increased diagnostic value over that achieved with CTM MR angiography alone. A combined MR angiographic approach in which a low total gadolinium dose (0.1 mmol/kg) is used yields excellent image quality and is accurate in the diagnosis of peripheral arterial stenosis.

• Evaluation of gadobutrol, a macrocyclic, nonionic gadolinium chelate in a brain glioma model: comparison with gadoterate meglumine and gadopentetate dimeglumine at 1.5 T, combined with an assessment of field strength dependence, specifically 1.5 versus 3 T.

  Authors: Ulrike I Attenberger, Val M Runge, John N Morelli, Jonathan Williams, Carney B Jackson, Henrik J Michaely

  Journal of magnetic resonance imaging : JMRI. 02/2010; 31(3):549-55.

  To evaluate in a rat brain glioma model intraindividual tumor enhancement at 1.5 T using gadobutrol (Gadovist), a nonionic, macrocyclic chelate currently in clinical trials in the United States, inTo evaluate in a rat brain glioma model intraindividual tumor enhancement at 1.5 T using gadobutrol (Gadovist), a nonionic, macrocyclic chelate currently in clinical trials in the United States, in comparison with both an ionic macrocyclic chelate, gadoterate meglumine (Dotarem), and an ionic linear chelate, gadopentetate dimeglumine (Magnevist), and to compare the degree of tumor enhancement with gadobutrol at 1.5 and 3 T. A total of 24 rats, divided into three groups with n = 8 animals per group, were evaluated. Animals in group 1 received injections of gadobutrol and gadopentetate dimeglumine, whereas those in group 2 received gadobutrol and gadoterate meglumine. Injections were performed in random order and separated by 24 hours. Magnetic resonance imaging (MRI) examinations were performed immediately following each contrast injection with a 1.5 T MR system. Animals in group 3 received gadobutrol injections using the same protocol but with scans performed at 1.5 and 3 T. In all examinations, T1-weighted images were acquired precontrast, 1 minute postcontrast, and at 4 consecutive 2-minute intervals thereafter. A contrast dose of 0.1 mmol/kg was used in all instances. In groups 1 and 2, tumor signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were higher for gadobutrol compared to both other agents at each timepoint postcontrast injection. The improvement in tumor CNR with gadobutrol, depending on time, was between 12% and 40% versus gadopentetate dimeglumine, with the difference achieving statistical significance at 7 minutes. The improvement in tumor CNR with gadobutrol, depending on time, was between 15% and 27% versus gadoterate meglumine, with the difference statistically significant at 5 and 9 minutes. In group 3 the improvement in tumor SNR and CNR seen with the increase in field strength from 1.5 to 3 T for gadobutrol was statistically significant at all acquired timepoints (P < 0.002). CNR mean values ranged from 10.4 +/- 2.9 to 24.6 +/- 5.0 at 1.5 T and from 20.5 +/- 5.9 to 47.8 +/- 15.7 at 3 T depending on the timepoint postcontrast. Consistently greater tumor enhancement was noted at all measured timepoints following contrast injection with gadobutrol compared to both gadopentetate dimeglumine and gadoterate meglumine at 1.5 T. A substantial further improvement in tumor enhancement was noted using gadobutrol at 3 T.

• Analysis of signal dynamics in oxygen-enhanced magnetic resonance imaging.

  Authors: Olaf Dietrich, Ulrike I Attenberger, Michael Ingrisch, Daniel Maxien, Michael Peller, Konstantin Nikolaou, Maximilian F Reiser

  Investigative radiology. 02/2010; 45(4):165-73.

  Oxygen-enhanced MRI (O2-MRI) is frequently based on a block paradigm consisting of a series of consecutive T1-weighted scans acquired during alternating blocks with inhalation of room air and of pureOxygen-enhanced MRI (O2-MRI) is frequently based on a block paradigm consisting of a series of consecutive T1-weighted scans acquired during alternating blocks with inhalation of room air and of pure oxygen. This design results in a complex signal-time course for each pixel, which displays the oxygen wash-in and wash-out processes and provides spatially resolved information about the lung function. The purpose of the present study was to optimize the signal-time-course analysis to extract (pixelwise) the maximum amount of information from the acquired data, and to introduce an appropriate cross-correlation approach for data sets containing the oxygen wash-in and wash-out periods. O2-MRI data of 11 healthy volunteers were acquired with a multislice inversion-recovery single-shot turbo-spin-echo sequence at 1.5 Tesla; lung and spleen were manually segmented on all 44 acquired slices. Six different model functions were pixelwise fitted to the data and compared using the Akaike information criterion. Four different reference functions were compared for cross-correlation analysis. The optimal model function is a piecewise exponential function (median enhancement in lung/spleen: 16.3%/14.8%) with different time constants for wash-in (29.4 seconds/72.7 seconds) and wash-out (25.1 seconds/29.6 seconds). As a new parameter, it contains the delay between switching the gas supply and the onset of the signal change (4.8 seconds/24.5 seconds). Optimal cross-correlation results were obtained with a piecewise exponential reference function, which was temporally shifted to maximize the correlation, yielding median correlation coefficients of 0.694 and 0.878, median time delays of 7.5 seconds and 38.6 seconds, and median fractions of oxygen-activated pixels of 83.6% and 92.2% in the lung and the spleen, respectively. It was demonstrated that the pixelwise assessment of O2-MRI data are optimally performed with piecewise exponential functions. Cross-correlation analysis with a piecewise exponential reference function results in significantly higher fractions of oxygen-activated pixels than with rectangular functions.

• Measuring perfusion and permeability in renal cell carcinoma with dynamic contrast-enhanced MRI: a pilot study.

  Authors: Mike Notohamiprodjo, Steven Sourbron, Michael Staehler, Henrik J Michaely, Ulrike I Attenberger, Gerwin P Schmidt, Holger Boehm, Annie Horng, Christian Glaser, Christian Stief, Maximilian F Reiser, Karin A Herrmann

  Journal of magnetic resonance imaging : JMRI. 02/2010; 31(2):490-501.

  To retrospectively assess an improved quantitative methodology with separate assessment of perfusion and permeability for characterization of primary renal cell carcinoma (RCC) and monitoringTo retrospectively assess an improved quantitative methodology with separate assessment of perfusion and permeability for characterization of primary renal cell carcinoma (RCC) and monitoring antiangiogenic treatment. Fifteen RCC patients before surgery, 6 RCC patients before and after neoadjuvant antiangiogenic therapy, and 15 patients without renal disease underwent dynamic contrast-enhanced (DCE)-MRI of the kidney with integrated retrospective respiratory triggering and an individual arterial input function. Tracer kinetic analysis was performed with a two-compartment-filtration-model for the kidney data and a two-compartment-exchange-model for the tumor data, providing four independent parameters: the perfusion-parameters plasma flow (F(P)) and plasma volume (V(P)), and the permeability-parameters extraction flow (F(E)) and extravascular-extracellular volume (V(E)). In tumors F(P) and F(E) were significantly lower than in normal kidneys. Tracer kinetic analysis displayed hemodynamic alteration caused by vessel infiltration or necrosis. Papillary RCC could be differentiated from clear-cell variants by a distinct perfusion pattern. In antiangiogenically treated RCC V(E) was not significantly decreased, while the perfusion parameters V(P) and F(P) were significantly diminished. DCE-MRI with integrated motion compensation enables evaluation of primary RCC and detects distinct perfusion patterns. Quantification with a two-compartment-exchange-model produces a separate perfusion- and permeability characterization and may become a diagnostic tool to monitor antiangiogenic treatment.

• Comprehensive MR evaluation of renal disease: Added clinical value of quantified renal perfusion values over single MR angiography.

  Authors: Ulrike I Attenberger, Steven P Sourbron, Stefan O Schoenberg, John Morelli, Tim Leiner, Gita M Schoeppler, Walter Samtleben, Krista L Birkemeier, Christian Glaser, Maximilian F Reiser, Henrik J Michaely

  Journal of magnetic resonance imaging : JMRI. 12/2009; 31(1):125-133.

  PURPOSE:: To evaluate the diagnostic accuracy of quantified renal perfusion parameters in identifying and differentiating renovascular from renal parenchymal disease. MATERIALS AND METHODS:: In all,PURPOSE:: To evaluate the diagnostic accuracy of quantified renal perfusion parameters in identifying and differentiating renovascular from renal parenchymal disease. MATERIALS AND METHODS:: In all, 27 patients underwent renal perfusion measurements on a 3.0 T magnetic resonance imaging (MRI) system. Imaging was performed with a saturation recovery TurboFLASH sequence (TR/TE 177/0.93 msec, flip angle 12 degrees , 5 slices/sec). All patients also underwent high-resolution MR angiography (MRA) (TR/TE 3.1/1.09, flip angle 23 degrees , spatial resolution 0.9 x 0.8 x 0.9 mm(3)). MR perfusion measurements were analyzed with a two-compartment model, quantifying the plasma flow (F(P))-a characteristic renal first-pass perfusion parameter. A receiver-operator characteristic analysis was used to determine the optimal threshold value for distinguishing normal and abnormal plasma flow values. Utilizing this cutoff, sensitivity and specificity of solitary MR perfusion measurements, MRA, and a diagnostic strategy combining the two were evaluated. RESULTS:: Quantified MR perfusion values yielded a sensitivity of 100% and a specificity of 85% utilizing the optimal plasma flow threshold value of 150 mL/100 mL/min, whereas single MRA achieved a sensitivity of 51.9% and a specificity of 90%. Combining both methods enabled improved detection of renovascular and renoparenchymal disease with a sensitivity of 96.3% and specificity of 90%. CONCLUSION:: In distinction to MRA, quantified MR perfusion measurements allow for the detection of pure renal parenchymal disorders. The combination of MRA with these perfusion measurements suggests an algorithm by which parenchymal and renovascular diseases may be reliably distinguished and the hemodynamic significance of the latter reliably determined. J. Magn. Reson. Imaging 2010;31:125-133. (c) 2009 Wiley-Liss, Inc.

• Feasibility of gadofosveset-enhanced steady-state magnetic resonance angiography of the peripheral vessels at 3 Tesla with Dixon fat saturation.

  Authors: Henrik J Michaely, Ulrike I Attenberger, Olaf Dietrich, Peter Schmitt, Kambiz Nael, Harald Kramer, Maximilian F Reiser, Stefan O Schoenberg, Michael Walz

  Investigative radiology. 09/2008; 43(9):635-41.

  INTRODUCTION: To investigate the feasibility and image quality of gadofosveset-enhanced steady-state peripheral MR-angiography using Dixon fat saturation in comparison to spectral fat saturation.INTRODUCTION: To investigate the feasibility and image quality of gadofosveset-enhanced steady-state peripheral MR-angiography using Dixon fat saturation in comparison to spectral fat saturation. MATERIALS AND METHODS: After Institutional Review Board (IRB) approval, 10 healthy volunteers underwent peripheral MR-angiography at 3.0 T during the steady state 50 minutes after gadofosveset injection. A steady-state-adapted volume interpolated breathhold examination sequence with an isotropic spatial resolution of 1 mm was acquired with 2-point Dixon fat saturation (DixFS, acquisition time 52 seconds) and with conventional, spectral fat saturation (SFS, acquisition time 58 seconds). The quality of the images was rated on an ordinal 4-point scale (4, very good) by 2 radiologists in consensus. The signal-to-noise ratios (SNRs) of the vessels, the fat, and the muscles as well as the contrast-to-noise-ratio (CNR) between vessels, fat, and muscle were determined. Paired P tests were performed for statistical analysis with a significance level of P < 0.05. RESULTS: Diagnostic image quality was achieved in all examinations. The image quality of the DixFS images was rated superior (median 4) over the SFS images (median 3; P = 0.03). The SNR of muscles and vessels was 40% higher with DixFS (P < 0.008), whereas the SNR of fat was decreased by 40.3% from 40.7 with SFS to 22.4 with DixFS (P < 0.0001). The CNR (fat/muscle) of the DixFS images of 84.1/71.7 was significantly higher than the CNR of the SFS images of 47.7/47.4 (P < 0.001). DISCUSSION: Two-point Dixon fat suppression for MR-angiography during the steady state after the administration of gadofosveset is feasible with superior image quality and more than 50% increase in CNR (fat/muscle) compared with spectral fat saturation without an additional time penalty.

• Three-dimensional contrast-enhanced magnetic-resonance angiography of the renal arteries: interindividual comparison of 0.2 mmol/kg gadobutrol at 1.5 T and 0.1 mmol/kg gadobenate dimeglumine at 3.0 T.

  Authors: Ulrike I Attenberger, Henrik J Michaely, Bernd J Wintersperger, Steven P Sourbron, Klaus-Peter Lodemann, Maximilian F Reiser, Stefan O Schoenberg

  European radiology. 06/2008; 18(6):1260-8.

  The purpose was to evaluate the image quality of high-spatial resolution MRA of the renal arteries at 1.5 T after contrast-agent injection of 0.2 mmol/kg body weight (BW) in an interindividualThe purpose was to evaluate the image quality of high-spatial resolution MRA of the renal arteries at 1.5 T after contrast-agent injection of 0.2 mmol/kg body weight (BW) in an interindividual comparison to 3.0 T after contrast-agent injection of 0.1 mmol/kg BW contrast agent (CA). After IRB approval and informed consent, 40 consecutive patients (25 men, 15 women; mean age 53.9 years) underwent MRA of the renal arteries either at a 1.5-T MR system with 0.2 mmol/kg BW gadobutrol or at a 3.0-T MR scanner with 0.1 mmol/kg BW gadobenate dimeglumine used as CA in a randomized order. A constant volume of 15 ml of these contrast agents was applied. The spatial resolution of the MRA sequences was 1.0 x 0.8 x 1.0 mm(3) at 1.5 T and 0.9 x 0.8 x 0.9 mm(3) at 3.0 T, which was achieved by using parallel imaging acceleration factors of 2 at 1.5 T and 3 at 3.0 T, respectively. Two radiologists blinded to the administered CA and the field strength assessed the image quality and the venous overlay for the aorta, the proximal and distal renal arteries independently on a four-point Likert-type scale. Phantom measurements were performed for a standardized comparison of SNR at 1.5 T and 3.0 T. There was no significant difference (p > 0.05) between the image quality at 3.0 T with 0.1 mmol/kg BW gadobenate dimeglumine compared to the exams at 1.5 T with 0.2 mmol/kg BW gadobutrol. The median scores were between 3 and 4 (good to excellent vessel visualization) for the aorta (3 at 1.5 T/4 at 3.0 T for reader 1 and 2). For the proximal renal arteries, median scores were 3 for the left and right renal artery at 1.5 T for both readers. At 3.0 T, median scores were 3 (left proximal renal artery) and 4 (right proximal renal artery) for reader 1 and 3 (left/right) for reader 2 at 3.0 T. For the distal renal arteries, median scores were between 2 and 3 at both field strengths (moderate and good) for both readers. The kappa values for both field strengths were comparable and ranged between 0.571 (moderate) for the distal renal arteries and 0.905 (almost perfect) for the proximal renal arteries. In the phantom measurements, a 40% higher SNR was found for the measurements at 3 T with gadobenate dimeglumine. High-spatial resolution renal MRA at 3.0 T with 0.1 mmol/kg BW gadobenate dimeglumine yields at least equal image quality compared with renal MRA at 1.5 T with 0.2 mmol/kg BW gadobutrol.

• Abdominal and pelvic MR angiography.

  Authors: Henrik J Michaely, Ulrike I Attenberger, Harald Kramer, Kambiz Nael, Maximilian F Reiser, Stefan O Schoenberg

  Magnetic resonance imaging clinics of North America. 09/2007; 15(3):301-14, v-vi.

  Currently, 3T MR scanners hold 10% of the market with rising market share. Angiographic exams in particular benefit directly from the higher field strength. The theoretically doubled signal-to-noiseCurrently, 3T MR scanners hold 10% of the market with rising market share. Angiographic exams in particular benefit directly from the higher field strength. The theoretically doubled signal-to-noise ratio at 3T allows for abdominal magnetic-resonance angiography (MRA) exams with submillimeter spatial resolution with acquisition times of less than 20 seconds. Because of altered longitudinal relaxation times, MRA exams can be performed with a significantly reduced amount of contrast agents. This review describes the current technical concepts and outlines typical sequence parameters for abdominal and pelvic MRA. The choice of contrast agents for abdominal MRA is discussed in detail. This article also provides an outlook to new technical concepts that are already at the horizon of MRA.