Biomedical subjects

Ulrike Attenberger

Publications and source records attributed to Ulrike Attenberger.

4 recordsLinked to original sources

PubMed2006

Functional renal MR imaging: an overview.

Due to its complementary information to standard morphological imaging, functional renal magnetic resonance imaging is a rapid growing field of radiology. This pictorial essay provides a comprehensive overview of state-of-the-art functional renal imaging techniques including renal magnetic resonance angiography, first pass renal perfusion, assessment of renal function, blood-oxygen level dependent imaging of the kidneys and diffusion-weighted imaging of the kidneys including diffusion-tensor imaging of the kidneys. Basic technical concepts for all sequences are laid out. As renal perfusion imaging becomes a clinical routine examination, particular attention is given to renal perfusion measurements and the potential postprocessing approaches. Advantages and drawbacks of the published methods are illustrated. Future applications of functional renal imaging are presented.

Contrast Media↗

PubMed2005

Pulmonary arterial hypertension: diagnosis with fast perfusion MR imaging and high-spatial-resolution MR angiography--preliminary experience.

PURPOSE: To determine prospectively the accuracy of a magnetic resonance (MR) perfusion imaging and MR angiography protocol for differentiation of chronic thromboembolic pulmonary arterial hypertension (CTEPH) and primary pulmonary hypertension (PPH) by using parallel acquisition techniques. MATERIALS AND METHODS: The study was approved by the institution's internal review board, and all patients gave written consent prior to participation. A total of 29 patients (16 women; mean age, 54 years +/- 17 [+/- standard deviation]; 13 men; mean age, 57 years +/- 15) with known pulmonary hypertension were examined with a 1.5-T MR imager. MR perfusion imaging (temporal resolution, 1.1 seconds per phase) and MR angiography (matrix, 512; voxel size, 1.0 x 0.7 x 1.6 mm) were performed with parallel acquisition techniques. Dynamic perfusion images and reformatted three-dimensional MR angiograms were analyzed for occlusive and nonocclusive changes of the pulmonary arteries, including perfusion defects, caliber irregularities, and intravascular thrombi. MR perfusion imaging results were compared with those of radionuclide perfusion scintigraphy, and MR angiography results were compared with those of digital subtraction angiography (DSA) and/or contrast material-enhanced multi-detector row computed tomography (CT). Sensitivity, specificity, and diagnostic accuracy of MR perfusion imaging and MR angiography were calculated. Receiver operator characteristic analyses were performed to compare the diagnostic value of MR angiography, MR perfusion imaging, and both modalities combined. For MR angiography and MR perfusion imaging, kappa values were used to assess interobserver agreement. RESULTS: A correct diagnosis was made in 26 (90%) of 29 patients by using this comprehensive MR imaging protocol. Results of MR perfusion imaging demonstrated 79% agreement (ie, identical diagnosis on a per-patient basis) with those of perfusion scintigraphy, and results of MR angiography demonstrated 86% agreement with those of DSA and/or CT angiography. Interobserver agreement was good for both MR perfusion imaging and MR angiography (kappa = 0.63 and 0.70, respectively). CONCLUSION: The combination of fast MR perfusion imaging and high-spatial-resolution MR angiography with parallel acquisition techniques enables the differentiation of PPH from CTEPH with high accuracy.

Diagnosis, Differential↗

PubMed2005

Fast oxygen-enhanced multislice imaging of the lung using parallel acquisition techniques.

The purpose of this study was to evaluate an optimized multislice acquisition technique for oxygen-enhanced MRI of the lung using slice-selective inversion and refocusing pulses in combination with parallel imaging. An inversion recovery HASTE sequence was implemented with respiratory triggering to perform imaging in end-expiration and with ECG triggering to avoid image acquisition during the systolic phase. Inversion pulses and the readout of echo trains could be interleaved to decrease acquisition time. The sequence was evaluated in 15 healthy volunteers, comparing three acquisition schemes: (1) acquisition of four slices without parallel imaging; (2) acquisition of four slices with parallel imaging; (3) acquisition of six slices with parallel imaging. These multislice acquisitions were repeated 80 times with alternating inhalation of room air and oxygen. The oxygen-induced signal increase showed no significant difference with and without parallel imaging. However, only with parallel imaging did the interleaved acquisition of six or more slices become possible, thus enabling a more complete anatomic coverage of the lung. The average required end-expiration time per repetition to acquire six slices could be significantly reduced from 4112 ms without to 2727 ms with parallel imaging. Total acquisition time varied between 8 and 13 min depending on the respiratory frequency.

Adult↗

PubMed2004

Quantification of pulmonary blood flow and volume in healthy volunteers by dynamic contrast-enhanced magnetic resonance imaging using a parallel imaging technique.

RATIONALE AND OBJECTIVES: We sought to optimize the dosage of a paramagnetic contrast medium (CM) for the quantification of pulmonary blood flow and volume by contrast-enhanced dynamic magnetic resonance imaging (MRI) using a parallel imaging technique and to prove the feasibility of the approach in healthy volunteers. METHODS: In a phantom study, the dependency of signal increase on different concentrations of the CM gadodiamide was evaluated by means of an ultra-fast MRI sequence with a generalized autocalibrating partially parallel acquisition technique (acceleration factor = 2). Using the same sequence, measurements were performed in a healthy volunteer after administration of different CM dosages for contrast dosage optimization in vivo. Finally, perfusion measurements were performed in 16 healthy volunteers after the administration of the optimal CM dose. Signal-time curves were evaluated from the pulmonary artery and from predefined regions of the lung. Pulmonary regional blood volume (RBV) and flow (RBF) were estimated using an open 1-compartment model. RESULTS: Phantom studies yielded a linear signal increase up to a concentration of 5.0 mmol/L gadodiamide. Results of contrast dosage optimization in vivo showed that the maximum CM dose providing a linear relationship between signal increase and CM concentration in the pulmonary artery of a healthy volunteer was approximately 0.05 mmol/kg-bw. Quantification of pulmonary blood volume and flow was reproducible in healthy volunteers, yielding mean values for the upper lung zones of 7.1 +/- 2.3 mL/100 mL for RBV and 197 +/- 97 mL/min/100 mL for RBF and for lower lung zones, 12.5 +/- 3.9 mL/100 mL for RBV and 382 +/- 111 mL/min/100 mL for RBF. CONCLUSIONS: If an adequate amount of gadodiamide and fast MR sequences are used, quantification of pulmonary blood flow and volume is feasible.

Adult↗