So Yeon Kim MD, Presenter: Nothing to Disclose

Kyoung Ho Lee MD, Abstract Co-Author: Nothing to Disclose

Young Hoon Kim MD, Abstract Co-Author: Nothing to Disclose

Heung Sik Kang MD, Abstract Co-Author: Nothing to Disclose

Kyuseok Kim, Abstract Co-Author: Nothing to Disclose

Taeyun Kim, Abstract Co-Author: Nothing to Disclose

Hye Seung Lee MD, Abstract Co-Author: Nothing to Disclose

Seung-Sik Hwang, Abstract Co-Author: Nothing to Disclose

Joong Eui Rhee, Abstract Co-Author: Nothing to Disclose

The purpose of our study was to compare low and standard radiation doses in intravenous contrast-enhanced CT for the diagnosis of acute appendicitis.

Two hundred fifty seven patients (age range, 15-40 years) who were suspected of having acute appendicitis underwent CT with mean effective does of 2.1mSv (low-dose CT, n=125) or with 9.3mSv (standard-dose CT, n=132). One of two radiologists interpreted CT images prospectively using a structured report. Readers recorded the likelihood of appendicitis and visualization of the appendix using 5- and 3-point scores, respectively and proposed alternative diagnosis. Likelihood of appendicitis ≥ 3 was considered as a positive diagnosis. Negative appendectomy rate (NAR) and perforation rate were assessed. Definite diagnosis was confirmed at surgery or clinical follow up. Receiver operating characteristics (ROC) analysis, Fisher’s exact test, and Mann-Whitney U test were used.

Ninety-five patients (37.0%) had appendicitis. The low-dose and standard-dose CT did not differ significantly in the area under the ROC curves (0.976 vs. 0.996, for low- and standard-dose, respectively, P=.27), sensitivity (97.6 [41/42] % vs. 98.1 [52/53] %, P >.99), and specificity (92.8 [77/83] % vs. 91.1 [72/79] %, P =.78) in the diagnosis of appendicitis. No difference was observed in the frequency of the indeterminate interpretation (grade 3) between low-dose and standard-dose CT (6.4 [8/125] % vs. 7.6 [10/132] %, P =.81). Visualization scores for a normal appendix at low-dose CT were comparable to standard-dose CT (1.70 vs. 1.89, P =.12). The sensitivity for alternative diagnoses was not significantly influenced by the dose (76.7 [23/30] % vs. 80.6 [29/36] %, P =.77). NAR at low-dose CT (4.5%) and standard-dose CT (1.9%) did not reach statistical significance (P=.59). Perforation rate was significantly higher in low-dose group (38.1 [16/42] % vs. 13.2 [7/53] %, P =.01).

IV contrast-enhanced low-dose CT (mean, 2.1 mSv) by reducing the tube currents had comparable diagnostic performance to IV contrast-enhanced standard-dose CT (9.3 mSv) for the diagnosis of acute appendicitis.

Low-dose CT with IV contrast has the potential to be the first-line imaging modality in the patients suspected of having acute appendicitis.

Kim, S, Lee, K, Kim, Y, Kang, H, Kim, K, Kim, T, Lee, H, Hwang, S, Rhee, J, Low versus Standard-dose Radiation in Intravenous Contrast-enhanced CT for the Diagnosis of Acute Appendicitis.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9003188.html