Biomedical subjects

Sascha Köhler

Publications and source records attributed to Sascha Köhler.

5 recordsLinked to original sources

PubMed2005

[Magnetic resonance tomography: potentials of molecular imaging].

Molecular imaging is "the in-vivo characterization and measurement of biological processes at the cellular and molecular level" and allows the imaging of molecular abnormalities associated with diseases long before morphological changes can be detected. At present, the use of magnetic resonance imaging (MRI) for molecular and cellular imaging is rapidly increasing. MRI is a very attractive candidate, since current MRI protocols already provide anatomic, functional, and biochemical information of excellent image quality and with high spatial resolution. Combining this high spatial resolution/high contrast imaging modality with specific MRI contrast imaging agents for molecular imaging is currently the focus of research in many laboratories worldwide. This paper summarizes the rationale for molecular MRI imaging and describes the basic features of modern molecular imaging strategies with MRI. Finally, a special focus is given to the growing field of applications, e.g., stem cell imaging, imaging of apoptosis, plaques, and other biological targets of interest.

Apoptosis↗

PubMed2003

Visualization of myocardial microstructure using high-resolution T*2 imaging at high magnetic field.

The analysis of myocardial microstructure in vivo is important for the determination of myocardial contractility and function. The purpose of the present study was to demonstrate that high-resolution T*2 imaging has the potential to visualize the microstructure of beating, isolated rat hearts. To perform T*2 imaging, a multiple gradient-echo sequence was implemented on an 11.75 Tesla microscopy system. An in-plane resolution of 78 microm and a slice thickness of 250 microm were achieved in 24 min. In comparison to histological sections, the T*2 maps showed an excellent spatial correspondence to the myocardial fiber structure. To demonstrate the utility of this technique, morphologic alterations in myocardial microstructure were investigated in hearts with chronic myocardial infarction. Scar tissue and the extent of the infarcted region were clearly visualized and quantified using high-resolution T*2 imaging.

Animals↗

PubMed2003

Time-resolved flow measurement in the isolated rat heart: characterization of left coronary artery stenosis.

The investigation of flow behavior in coronary arteries is of great importance for an understanding of heart failure and heart regulation mechanisms. The purpose of the present study was to demonstrate that flow velocity can be quantified in the coronary arteries of the isolated rat heart with high-resolution phase contrast MRI. A phase contrast cine-FLASH imaging sequence was used for flow quantification with an in-plane resolution of 70 microm and a slice thickness of 500 microm. With time-resolved measurements, coronary flow over the heart cycle was analyzed. Furthermore, the flow behavior in coronary stenosis was investigated and the degree of stenosis was quantified with MR phase contrast imaging. To achieve the required spatial resolution and a satisfactory signal-to-noise ratio, the experiments were performed at 11.75 T.

Animals↗

PubMed2003

Investigation of the microstructure of the isolated rat heart: a comparison between T*2- and diffusion-weighted MRI.

Myocardial fiber structure can be determined with diffusion-weighted (DW) MRI as well as with high-resolution T*(2) imaging. The purpose of the present study was twofold: to provide a more quantitative description of T*(2)-based myocardial fiber contrast, and to compare the T*(2)-based fiber structure with high-resolution (78 microm in-plane, 1-mm slice thickness) DW images of the isolated rat heart at 11.75 T. This study demonstrates that the static dephasing regime is responsible for visualization of myocardial microstructure, and that the dynamic dephasing regime can be neglected. In comparison with DW experiments, T*(2) mapping and DW images yield almost equivalent information on myocardial fiber structure.

Animals↗

PubMed2003

NMR-microscopy with TrueFISP at 11.75T.

The purpose of this paper is to demonstrate that a fully balanced gradient echo technique (TrueFISP) can be used for microscopic experiments at high static magnetic field strengths. TrueFISP experiments were successfully performed on homogeneous and inhomogeneous objects at 11.75T. High-resolution TrueFISP images were obtained from phantoms, plants, formalin-fixed samples, and from an isolated beating rat heart with an in-plane resolution of 78 micro m and a slice thickness of 500 micro m. The signal-to-noise ratio (SNR) gain of TrueFISP compared to conventional gradient echo or spin echo sequences will allow faster acquisition times or an improvement in spatial resolution for microscopic experiments.

Animals↗