4.5. LIFE SCIENCES
CORONARY ANGIOGRAPHY WITH SYNCHROTRON RADIATION
Pekka Suortti, ESRF Medical Beamline Team, and CHU Grenoble Team
Coronary angiography where intravenous injection of the contrast agent and digital subtraction of images acquired at energies bracketing the K-absorption edge of the contrast agent are used was introduced in 1980's at SSRL, Stanford, USA. Later that program moved to the NSLS, Brookhaven, USA, and a similar program was started at Hasylab, Hamburg. The conventional clinical angiography entails serious risks due to catheterization and injection of the contrast agent bolus into the aorta, which prevents its use in follow-up studies and research. In the K-edge subtraction (KES) imaging two narrow energy bands are used, the contrast agent is injected in a vein, and in the subtraction image only the distribution on the contrast agent in circulation is seen. There are no risks and inconveniences arising from catheterization, and the radiation dose is low. The method is now in use at the ESRF, and first large animals (pigs) were imaged in 1998. The images are of clinical quality, and they allow diagnosis of stenosis in the heart arteries. The first imaging of human patients took place in January 2000.
H. Elleaume et al. Synchrotron Radiation News 12, No. 1 (1999) 34-36
QUANTITATIVE LUNG IMAGING WITH SYNCHROTRON RADIATION
G. LeDuc*, S. Bayat**, Liisa Porra, Pekka Suortti, A.R.A. Sovijärvi+, C.-G. Standertskjöld-Nordenstam+, and ESRF Medical Beamline Team
Quantitative lung imaging is derived from coronary angiography with synchrotron radiation. The images are acquired in the same way, but in lung imaging the contrast agent is stable Xe gas mixed with oxygen. The subtraction image shows details of the bronchial tree on the 1 mm level, which is impossible to reach by any other imaging method. Filling of alveoli overshadows the bronchi, but sections of lungs can be imaged by tomographic reconstruction. The most important feature of the KES imaging using Xe gas is that the absolute concentrations can be calculated, which provides new possibilities for functional imaging of lungs. First animal experiments were carried out at the Medical Beamline of the ESRF in October 1999, and the results are being analyzed.
* ESRF, Grenoble, France
** University of Grenoble, Grenoble, France
+ Helsinki University Central Hospital
DIFFRACTION ENHANCED IMAGING
Pekka Suortti, M. Fernández, Jani Keyriläinen, M.-L. Karjalainen-Lindsberg*, A. Bravin**, S. Fiedler** and W. Thomlinson**
Diffraction Enhanced Imaging (DEI) is one of several techniques where the change of the wave front phase or propagation direction at a boundary in the sample is used for contrast formation. In DEI the beam transmitted through the sample is analyzed by a perfect crystal, which acts as a very narrow angular slit, and where the small changes due to refraction are observed as intensity modulation. The condition for imaging is that the incident beam is parallel and monochromatic, and this is achievable at a synchrotron radiation source only. Experimental program has started at the ESRF, and some of the instrumentation is being developed at the X-Ray Laboratory. The other possibility for DEI is to observe a particular scattered signal. Small angle X-ray scattering (SAXS) from different tissue samples was measured at Hasylab in September. The samples were obtained from the Cancer Clinic+, and they included excised normal, adipose, mastopathic, connective tissue, and adenocarcinoma. Characteristic differences in the SAXS pattern were observed, and their use for imaging is being evaluated.
* Helsinki University Central Hospital
** ESRF, France
+ Department of Oncology, Helsinki University Central Hospital
STUDIES OF INTERDOMAIN ORIENTATIONS BY SMALL-ANGLE X-RAY SCATTERING AND NMR
A. Annila*, H. Autio*, M.-L. Mattinen*, Mika Torkkeli and R. Serimaa
Many biological functions involve reorientation of protein domains. SAXS gives information on the shape and aggregation the particles in solution. Here it is used to study orientation of protein domains. The idea is to combine the distance distribution function determined by SAXS and the long-range orientational information of NMR and to model domain orientations based on the experimental data. The first experiments with Troponin C and Calmodulin were performed and modelling is in progress.
* Chemical Technology, VTT
NANOSTRUCTURES OF COMPLEXES OF CATIONIC STARCH AND ANIONIC SURFACTANTS
Teemu Ikonen, Mika Torkkeli, Ritva Serimaa, J. Merta*, E. Kontturi* and P. Stenius*
Combining surfactants with oppositely charged polyelectrolytes is one way for producing ordered materials. Such materials have biological significance, since polynucleic acids and proteins are polyelectrolytes and lipids are surfactants. According to the SAXS experiments the structures formed in aqueous solutions of cationic starch and alkanoates and sodium dodecyl sulfate depended from the length of the hydrocarbon chain of the surfactant. Cylindrical, lamellar, and spherical micelles were obtained, which formed well ordered larger scale crystalline structures.
* Department of Forest Products Technology, Helsinki University of Technology
X-RAY DIFFRACTION STUDY ON COPRECIPITATES OFb -SITOSTEROL AND CHOLESTEROL
Nadja Lönnroth, Milja Karjalainen, Ritva Serimaa, L. Christiansen*, J. Yliruusi* and Timo Paakkari
Both beta-sitosterol and beta-sitostanol have observed to lower serum cholesterol levels in human trials by restricting intestinal absorption of cholesterol. One of the possible mechanisms for the inhibition of cholesterol absorption is the formation of mixed crystals of cholesterol andb-sitosterol. Coprecipitates of b-sitosterol and cholesterol were studied by X-ray diffraction (WAXS, SAXS) as a function of temperature. Results indicated that a new mixed crystal structure, a solid solution of cholesterol and b-sitosterol, was formed. This structure dominated at b -sitosterol concentrations of 20-60%.
* Pharmaceutical Technology Division, Deparment of Pharmacy, University of Helsinki
4.5. APPLIED X-RAY PHYSICS
SOLID STATE DETECTORS FOR X-RAY ASTROPHYSICS
Jarkko Laukkanen, Keijo Hämäläinen, J. Huovelin* and L. Alha*
The project on development and characterization of solid-state detectors for X-ray astrophysics has continued and expanded. The performance of the SIXA detector (the final qualification model) was studied. Further, a pair of solid-state detectors monitoring the solar X-ray activity was approved for the ESA SMART-1 mission, due to launch in December 2002. The XSM (X-ray Solar Monitor) units will be designed, constructed and characterized in collaboration with Metorex Oy.
* Observatory, Department of Astronomy, University of Helsinki