MDCT of Patients with Acute Abdominal Pain

Erik K. Paulson ; Tracy A. Jaffe ; John Thomas ; John P. Harris ; Rendon C. Nelson

Numerous studies indicate that CT, when combined with careful physical examination and evaluation of laboratory results, provides useful diagnostic information in patients with an acute abdomen [1–4]. As a result, CT is increasingly used in the emergency department setting. MDCT is a technologic advance that allows simultaneous acquisition of multiple images during a single rotation of the X-ray tube [5]. With the recently developed 16-MDCT scanner, it is now possible to scan the entire abdomen and pelvis within a breath-hold at a resolution of less than 1 mm (0.5–0.75 mm) in the x, y, and z axes. These data sets result in voxels that are both submillimeter in dimension and isotropic, suggesting that reformations in any desired plane will have a spatial resolution similar to that of the axial plane. With 4- or 8-MDCT scanners, it was not possible to cover the entire abdomen and pelvis within a single breathhold at submillimeter z-axis resolution.

Heretofore, the usefulness of multiplanar reformations was limited by the speed with which images could be reconstructed and the necessity of performing several time-consuming steps. First, the source images were reconstructed from the raw data with at least a 50% overlap. The reconstructed images were transferred to an independent workstation that, depending on the number of images and processing speed of the computer, might require significant computational time. Then to view the images, an operator had to prescribe the parameters on the workstation. The total time required for this process ranged from 10 to 30 min, far exceeding the time required to review the axial images alone. Recently, console systems have become available that have streamlined and shortened the time required to perform reconstructions.

Radiologists are skilled in interpreting CT scans in the axial plane, but the development of MDCT coupled with faster reconstruction hardware and software has piqued interest in viewing the abdomen in planes other than the axial plane [6]. In some patients with acute abdominal pain, the coronal plane images may serve as a useful adjunct to the axial plane images. Images in the coronal plane are particularly appealing to surgeons because the orientation of structures is analogous to that encountered during an exploratory laparotomy. We illustrate our preliminary use of coronal reformations using 16-MDCT scanner as an adjunct to the axial plane in the evaluation of patients with acute abdominal pain.