Gadolinium diethylenetriaminepentaacetic acid (DTPA) covalently linked to the lipophilic ethoxybenzyl moiety (Gd-EOB-DTPA) was designed for use as a contrast agent in hepatobiliary magnetic resonance imaging. With T1 relaxivity values of 8.7 L/mmol.second in plasma and 16.6 L/mmol.second in rat liver tissue and a median lethal dose of 10 mmol/kg when administered intravenously in mice and rats, Gd-EOB-DTPA has a fairly high margin of safety. In rats and monkeys, biodistribution studies performed 7 days after administration of 0.25 mmol/kg revealed very little retention of gadolinium (less than 1%) in the tissues, indicating complete elimination via renal and biliary excretion. Biliary excretion was inhibited by coadministration of sulfobromophthalein, indicating the involvement of a carrier-mediated transport system based on the enzyme glutathione-S-transferase. In rats, the biliary transport maximum was 5 mumol gadolinium/min.kg. High T1 relaxivity of Gd-EOB-DTPA in rat liver in vivo can be explained by transient interaction with intracellular components and by increased microviscosity inside the hepatocyte.

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The instrumental and physical data outlined predestine Zr as contrasting element with a high potential for energy subtraction imaging in digital mammography in the energy range conventionally applied.

The animal models used in the current series of studies seem to be valid for predicting the effect of contrast agents on the blood clotting system in humans.

Metal complexes of the EOB-DTPA type, especially those of Gd and Yb seem to be useful as iodine-free liver-specific contrast agents for CT.

X-ray spectra are composed of a broad bremsspectrum and anode-characteristic emission lines. In mammography typically molybdenum (Mo), rhodium (Rh) or tungsten (W) anodes are used in combination with Mo, Rh or aluminium filters. Only the photons with energies between 17 and 22 keV of the resulting spectrum are suitable for the soft tissue imaging needed for mammography. The aim of this article is to present first results obtained with a monochromator module mounted at the exit of the X-ray tube of a conventional clinical mammography unit. The experimental setup consists of a Siemens Mammomat 300, an X-ray monochromator module and a linear array detector for image acquisition. The technique is similar to the slot-scan technique known from digital mammography. The experimental machine allows to obtain images both with polychromatic and monochromatic X-rays. Initial evaluation of the system was performed by examination of a contrast-detail phantom (CD-MAM-phantom, Nijmegen, The Netherlands). Images done with the new monochromatic technique were compared to images of the phantom done with polychromatic spectra, with film-screen mammography as well as with digital mammography. The new technique with monochromatic slot-scan mammography resulted in correct identification of 93% of the phantom. Digital slot-scan mammography with polychromatic beam resulted in correct identification of 87%, digital full-field mammography in 83% and conventional film-screen mammography in 70% of the phantom. The results suggest that monochromatization has a potential for improving image quality or decreasing dose in X-ray mammography.

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