臨床上我們定義輸尿管結石的影像密度(ID)為：KUB片子中結石的X光不透性減去其週遭0.5公分範圍內的X光不透性的平均值。自77年11月至78年2月間有51例單純輸尿管結石接受ESWL為初次治療。有10例在治療前先被推回腎孟，其中90％一次ESWL可以完全震碎。有41例結石在其原位上接受治療。輸尿管結石的影像密度和其長或寬並無關聯存在。結石接受原位ESWL，ID≦3.0者有34例，其中68％可以一次ESWL完全震碎；ID＞3.0者有7例，無一例可以一次ESWL完全震碎。後排出的碎片有15例接受偏光鏡檢查，ID≦2.0者有6例，其成份以雙水草酸鈣和磷酸鹽為主；3.0＞ID＞2.0者有7例，其主成份為雙水草酸鈣和單水草鈣；有2例ID＞3.0，其主成份為單水草酸鈣。尿路結石的影像密度為一種新的要素，必須和結石的大小、位置等一齊列入選擇治療方式的考慮因素之一。

Clinically, we definded the image density (ID) of a urinary calculus as "the dif-ference of the radiopacity of the stone and the average radiopacity of the background surrounding it on a KUB film. "From Nov. 1, 1988 to Feb. 28, 1989, there were 51 solitary ureteral stones initally treated by ESWL at the Department of Urology of NTUH. Of them, 35 were upper ureteral stones, 11 middle ureteral stones and 5 lower ureteral stones. Ten upper ureteral stones were manually repositioned back to renal pelvis and 90% of them were completely crushed by one session of ESWl (Dornier HM-3, maxium 2400 pulses, 18-22KV), the rest of them were treated in situ. 23 (68%) out of 34 ureteral stones treated in situ, with and ID≦3.0, were completely disinter-grated by one session of ESWL. There were 7 stones bearing an ID>3.0 treated in situ, one received only one session of ESWL and resulted in residual fragments. Image density of calculi is a new clinical distinction to be included with stone size and posi-tion to make ESWL a more informed treatment. (J Urol R.O.C., 1:289-295, 1990)