| 1. |
- Valiullin, R., et al.
(författare)
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NMR magnetization transfer as a tool for characterization of nanoporous materials
- 2003
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Ingår i: Magnetic Resonance Imaging. - 0730-725X .- 1873-5894. ; 21:04-mar, s. 299-303
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Tidskriftsartikel (refereegranskat)abstract
- The application of nuclear magnetic resonance magnetization transfer experiments to probe the surface-to-volume ratio and pore morphology of porous materials with characteristic pore sizes of 1-100 nm is described. The method is based on the phenomenon of incomplete freezing of liquids in small pores where a few monolayers adjacent to the pore walls remain liquid. Sufficient difference between the transverse relaxation times in the solid frozen core and liquid surface layer allows the initial preparation and subsequent re-equilibration of a solid-liquid magnetization grating. The method is demonstrated using model nanoporous materials with known characteristics. The ensuing problems of the mechanism of the magnetization transfer through the interface and within the frozen core are discussed and elucidated by pulsed-field-gradient NMR experiments.
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| 2. |
- Hol, P K, et al.
(författare)
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MRI-guided celiac plexus block
- 2000
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Ingår i: Magnetic Resonance Imaging. - 0730-725X .- 1873-5894. ; 12, s. 562-564
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Tidskriftsartikel (refereegranskat)
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| 3. |
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| 7. |
- Weis, J, et al.
(författare)
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High-resolution spectroscopic imaging of the human skin.
- 2001
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Ingår i: Magnetic Resonance Imaging. - 0730-725X .- 1873-5894. ; 19:2, s. 275-8
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution water, fat and chemical shift artefact-free images of different areas of the skin were obtained on a whole-body MR unit (1.5 T) with commercial receiver surface coil with a diameter of 25 mm and high-power gradients (23 mT/m). Sufficient signal-to-noise ratio was achieved by lowering receiver bandwidth to +/-10 kHz or lower and shortening the echo time to 11 (13) ms. Spectroscopic image data sets were acquired with resolution 0.102 x 0.133 mm in plane and slice thickness 0.5 mm. The results demonstrate that it is possible to produce high-quality water and fat micro-images of the skin layers using only a few chemical shift encoding steps in a clinically reasonable time (approximately 2 minutes per slice).
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| 8. |
- Weis, J, et al.
(författare)
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Spectroscopy of large volumes : spectroscopic imaging of total body fat
- 2001
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Ingår i: Magnetic Resonance Imaging. - 0730-725X .- 1873-5894. ; 19:9, s. 1239-1243
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Tidskriftsartikel (refereegranskat)abstract
- An extremely large volume of interest (VOI) approximately 60 dm(3) was used for the measurement of the proton ((1)H) spectrum of the human body. The measurements were performed at 1.5 T with a high-speed spectroscopic imaging technique that uses read gradient during acquisition. The spectrum was computed from coronal 30 mm thick slices of a normal male and female volunteer. The fat/water ratio of the body was used to quantify the fat depots. The results were corrected for relaxation effects and were in good agreement with published values of subjects with comparable body mass index (BMI).
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| 9. |
- Svensson, Jonas, et al.
(författare)
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Separation of arteries and veins using flow-induced phase effects in contrast-enhanced MRA of the lower extremities
- 2002
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Ingår i: Magnetic Resonance Imaging. - 0730-725X. ; 20:1, s. 49-57
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Tidskriftsartikel (refereegranskat)abstract
- In 3-D contrast-enhanced magnetic resonance (MR) angiography of the lower extremities the goal is most often to enhance arterial structures while keeping veins and surrounding tissue unenhanced. Imaging during steady-state concentration of a blood pool agent or during poor timing of an extra-cellular contrast medium may result in simultaneous venous enhancement, making interpretation of the angiogram difficult. The aim of this study was to develop a post-processing method to separate the arteries from the veins in standard contrast-enhanced MR angiograms. The method was based on the different accumulation of flow-induced phase in the arteries and veins of the lower extremities. The method was tested in both phantom experiments and volunteers undergoing 3-D contrast-enhanced MR angiography using both an extra-cellular contrast medium and a blood pool agent. In the phantom studies, opposite directional flow was successfully separated at mean flow velocities as low as 9 cm/s. In the volunteer studies, the larger veins were successfully extinguished while the larger arteries were left unaffected. In smaller vessels with low flow velocities the separation was less successful. This was most apparent in vessels not oriented superior-inferior. The method developed here is promising for separating arteries from veins in contrast-enhanced MR angiography although the results could be further improved by either a different pulse sequence design or combining this method with other segmentation methods.
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