A multiple detector array helical x-ray microtomography system for specimen imaging.

An x-ray computed microtomography system for specimen and small animal imaging was built and tested. The system used seventeen 48-microm-wide detector arrays (a charge coupled device camera) and helical acquisition techniques. Images were acquired using 540 rays/view and 400 views/2pi. The modulation transfer function (MTF) of the computed tomography images demonstrated 50 microm limiting resolution, with MTF > 10% for objects larger than 60 microm (approximately 8.3 cycles/mm). While soft tissue discrimination was compromised by a low signal-to-noise ratio, equine medullary bone core samples and the murine skeleton were well visualized. The incorporation of multiple detector arrays provided a 17-fold improvement in x-ray efficiency, which is a very important step toward improving the potential of microtomography as a scientific tool.

Angiographic film subtraction using a laser digitizer and computer processing.

Digital subtraction angiography has been accepted as an invaluable clinical tool over the past decade; however, film-screen-based angiography is still performed routinely when high-resolution or large field-of-view angiograms are needed. A technique is presented whereby two films from an angiographic sequence are digitized using a high-resolution laser digitizer, and the digitized images are aligned, subtracted, and displayed using the computer. To accommodate for some types of patient motion, an image warping algorithm is presented and discussed in detail. The warping algorithm is piecewise linear, using triangular regions for warping, resulting in a global nonlinear transform across triangle elements. An algorithm describing optimal triangle selection also is discussed. The results show that subtraction images of excellent quality can be produced by the proposed technique, and suggest that, in some settings, digitized subtraction films may be preferred over conventional film subtraction.