Ikuo Kawashita Masahito Aoyama Tomoaki Kajiyama Naoki Asada Collimation Detection in Digital Radiographs Using Plane Detection Hough Transform. 394-401 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2774&spage=394 2003 conf/kes/2003-2 KES db/conf/kes/kes2003-2.html#KawashitaAKA03