Image magnification in renal and superior mesenteric angiography: CT calculation and assessment of variables

To estimate the magnification that occurs in conventional renal and mesenteric angiography and to assess the influence of anatomic and technical variables.

Anticipated image magnification was derived solely from computed tomographic (CT) measurements obtained of 152 consecutive adult patients who underwent abdominal CT. Scans showed the distance from the origin and distal portions of both renal arteries to the anterior and posterior body surfaces, as well as the distance from the origin of the superior mesenteric artery to the lateral body surfaces. Assuming a 101.6-cm (40-inch) source-to-image receptor distance, the degree of magnification was calculated for posteroanterior, anteroposterior, and lateral radiographic imaging techniques.

Calculated mean magnification for the proximal renal artery was 14.5% (range, 7.2%-25.8%) with posteroanterior imaging and 26.7% (range, 22.3%-36.7%) with anteroposterior imaging and a 10-cm-thick table. Mean magnification for the distal renal artery was 16.1% (range, 8.8%-25.3%) with posteroanterior imaging and 24.6% (range, 19.5%-36.4%) with anteroposterior imaging and a 10-cm-thick table. Magnification of the superior mesenteric artery was 17.8% (range, 12.5%-33.9%) with left lateral imaging. Regression analysis documented a linear relationship between percentage magnification and body diameter.

Arterial location, imaging technique, and especially body habitus affect the degree of magnification in a predictable fashion.