Fast-Neutron imaging with PCII V. Dangendorf A new imaging method that combines high-efficiency fast-neutron detection with sub-ns time resolution is presented. This is achieved by exploiting the high neutron detection efficiency of a thick scintillator and the fast timing capability and flexibility of light-pulse detection with a dedicated image intensifier. The neutron converter is a plastic scintillator slab or, alternatively, a scintillating fibre screen. The scintillator is optically coupled to a pulse counting image intensifier which measures the 2-dimensional position coordinates and the Time-Of-Flight (TOF) of each detected neutron with an intrinsic time resolution of less than 1 ns. Large-area imaging devices with high count rate capability can be obtained by lateral segmentation of the optical readout channels.
The enhancing effect of gadolinium diethylenetriaminepentaacetic acid (DTPA) polylysine (a macromolecular paramagnetic contrast agent) in time-of-flight magnetic resonance (MR) angiography of isolated perfused sheep lungs was studied. Unilateral lung damage was induced with hydrochloric acid in eight sheep. The heart and lungs were removed from the thoracic cavity, and after cannulation of the trachea and both ventricles, pulsatile perfusion and ventilation were initiated. The heart-lung preparations were placed in the head coil of a 1.5-T imager. Time-of-flight pulmonary MR angiography was performed during respiratory arrest, before and after administration of 0.02 mmol/kg Gd-DTPA-polylysine. On the postcontrast angiograms, the signal intensity increased by 120% in pulmonary arteries (P < .01). The contrast-to-noise ratio between pulmonary arteries and parenchyma increased significantly (P < .01). The number of visualized generations of pulmonary artery branches increased from four to six in normal lungs and from three to five in edematous lungs. Low-dose Gd-DTPA-polylysine significantly improves the conspicuity of the pulmonary vascular tree in time-of-flight pulmonary MR angiography.
A transversal mapping of the Gd concentration was measured in UO 2 -Gd 2 O 3 nuclear fuel pellets by electron paramagnetic resonance spectroscopy (EPR). The quantification was made from the comparison with a Gd 2 O 3 reference sample. The nominal concentration in the pellets is UO 2 : 7.5 % Gd 2 O 3 . A concentration gradient was found, which indicates that the Gd 2 O 3 amount diminishes towards the edges of the pellets. The concentration varies from (9.3±0.5)% in the center to (5.8±0.3)% in one of the edges.The method was found to be particularly suitable for the precise mapping of the distribution of Gd 3+ ions in the UO 2 matrix.
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