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Evaluation of the potential of various MR techniques to differentiate bladder wall layers verified by histological findings.6 bladder specimens of pigs were examined in vitro using T1-weighted spin-echo-sequences, T2-weighted Turbo-SE, fat suppressed T2-weighted SE, and inversion recovery sequences. The MR images were obtained before and after fixating the specimens in formalin. Measurements of the thickness of bladder wall layers were performed on both sets of MR images as well as on histological sections,T2-weighted SE images showed three layers of different signal intensities: one innermost band of very high signal, one inner band of low and one outer band of intermediate signal corresponding histologically tunica propria and two different muscle layers. Inversion recovery technique provided similar findings but were able to avoid chemical-shift artifacts. After 24 hours in formalin, the signal intensity relation of the two muscle layers was inverted. The thickness of total bladder wall was not reduced significantly. Concerning the thickness of urinary bladder wall, histological measurements and evaluation of MR images correlated well.MR imaging enables the differentiation of three bladder wall layers. Inversion recovery technique achieved the best image quality by avoiding chemical shift artifact.

We have carried out an experimental study using a new laser catheter on 28 cadaver femoral arteries in 14 subjects and on six aortas. This ring catheter system consists of 12 circular quartz fibres with a central lumen and allows the application of energies up to 20 mJ through a 7F flexible catheter in vivo. The laser emits ultraviolet light of a wave-length of 308 nm, in pulses of 60 ns and a frequency of 2-40 Hz. The energy within a single fibre is 5 J/cm2 and exceeds the intensity required to ablate calcifications. Histologically it has been shown that, depending on the type of tissue, 1 to 2.4 microns of tissue per pulse is removed. Experimentally, rate of progress in a calcified occlusive lesion in the femoral artery, using 20 Hz and energy transmission of 20 mJ, was 3 to 5 mm per minute. Perforation of vessel wall if the catheter tip was at right angles to it depended on the degree of atherosclerosis and was between nine and 116 seconds. Marginally, there was only minimal thermal damage.