A new method for fast magnetic resonance imaging is presented. It provides a more rapid data acquisition than two-dimensional Fourier imaging (2DFI) by a factor which may be chosen depending on the required signal-to-noise ratio of the image. In addition to the readout gradient of 2DFI, the present method employs an oscillating modulation gradient. In this way, a curved alternating trajectory in k space is sampled after each spin excitation. For a p-times accelerated data acquisition, the trajectory consists of p periods, where p is of the order of 2 to 8 for low-frequency gradient modulation but can be chosen higher if certain hardware requirements are met. Adequate sampling density in k space is obtained by scanning shifted trajectories after subsequent spin excitations. The method can be combined with volume imaging (3DFI) and multiple slice 2DFI. It was implemented on a standard Philips Gyroscan system without any hardware modifications. Results obtained for an acceleration factor p = 4 are shown.

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We h a v e developed large high-resolution tracking detectors based on glass capillaries lled with organic liquid scintillator of high refractive index. These liquid-core scintillating optical bres act simultaneously as detectors of charged particles and as image guides. Track images projected onto the readout end of a capillary bundle are visualized by an optoelectronic chain consisting of a set of image-intensi er tubes followed by a photosensitive CCD or by an EBCCD camera. Two prototype detectors, each composed of 10 6 capillaries with 20 25 m diameter and 0.9 1.8 m length, have been tested, and a spatial resolution of the order of 20 40 m has been attained. A high scintillation e ciency and a large light-attenuation length, in excess of 3 m, was achieved through special puri cation of the liquid scintillator. Along the tracks of minimum-ionizing particles, the hit densities obtained were 8 hits/mm at the readout window, and 3 hits/mm at 1 m a w a y . The level of radiation resistance of the prototype detectors is at least an order of magnitude higher than that of other tracking devices of comparable performance.

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