Bednarek D R, Rudinger G, Rudin S
Department of Radiology, School of Medicine, State University of New York, Buffalo 14215.
Med Phys. 1988 Jan-Feb;15(1):29-35. doi: 10.1118/1.596157.
The rotating-aperture wheel (RAW) scanning-beam device is uniquely applicable for scatter elimination in short-time, rapid-sequence, and real-time radiographic imaging because of the continuous rotary motion of its slit pattern. This rotary motion places special restrictions on the slit pattern design. Although simple sector-shaped slits provide uniform primary transmission, they entail an unacceptable degree of slit widening on small-diameter wheels. The use of multiple slit zones with slits of different angular width has reduced the extent of this widening on a prototype RAW; however, interzone boundary artifacts caused by differential primary x-ray cutoff are apparent on some clinical images. This problem is eliminated with a unique spiral-shaped aperture pattern which consists of slits of constant width and constant spacing. Each slit is radially continuous and provides uniform primary transmission without interzone artifacts. This spiral pattern satisfies all requirements and appears to be the pattern of choice for rotating-aperture scanning-beam radiography.
旋转孔径轮（RAW）扫描束装置因其狭缝图案的连续旋转运动，在短时间、快速序列和实时射线成像中特别适用于消除散射。这种旋转运动对狭缝图案设计提出了特殊限制。虽然简单的扇形狭缝可提供均匀的一次射线传输，但在小直径轮上会导致不可接受程度的狭缝变宽。在原型RAW上使用具有不同角宽度狭缝的多个狭缝区，已减少了这种变宽的程度；然而，在一些临床图像上，由不同的一次X射线截止引起的区际边界伪影很明显。一种独特的螺旋形孔径图案消除了这个问题，该图案由宽度和间距恒定的狭缝组成。每个狭缝在径向是连续的，可提供均匀的一次射线传输且无区际伪影。这种螺旋图案满足所有要求，似乎是旋转孔径扫描束射线照相术的首选图案。
