Law J
Edinburgh University Department of Medical Physics and Medical Engineering, Western General Hospital, UK.
Br J Radiol. 1993 Jan;66(781):44-50. doi: 10.1259/0007-1285-66-781-44.
Three different measurement techniques for estimating the size of focal spots in X-ray tubes are described. These are the pin-hole, the slit and the star pattern or resolution pattern, and all are well known. Results are reported for a number of modern mammography X-ray tubes employed in a screening programme, using all three techniques. The results are compared with each other and with makers' specifications, IEC tolerances and UK Department of Health guidelines. Agreement between slit and star pattern results is generally within a few per cent, while pin-hole results are usually appreciably smaller. Although the slit technique is the most reliable for estimating focal spot size, both the others have a useful role, especially in revealing focal spot condition. Compliance with makers' specifications is usually demonstrated, but compliance with Department of Health guidelines is only found on the width of broad foci.
介绍了三种用于估计X射线管中焦点尺寸的不同测量技术。这些技术分别是针孔法、狭缝法以及星型图案或分辨率图案法，它们都是广为人知的。报告了在一项筛查计划中使用的多种现代乳腺摄影X射线管采用这三种技术的测量结果。将这些结果相互比较，并与制造商的规格、国际电工委员会（IEC）公差以及英国卫生部指南进行比较。狭缝法和星型图案法的测量结果之间的一致性通常在百分之几以内，而针孔法的结果通常明显更小。尽管狭缝法在估计焦点尺寸方面是最可靠的，但其他两种方法也有其有用之处，特别是在揭示焦点状况方面。通常能够证明符合制造商的规格，但仅在宽焦点的宽度方面符合卫生部指南。
