Best Protocol for Combined Contrast-Enhanced Thoracic and Abdominal CT for Lung Cancer: A Single-Institution Randomized Crossover Clinical Trial

Abstract

Objective: The purpose of this study was to evaluate the superiority of either of two protocols for combined contrast-enhanced thoracic and abdominal CT of patients with lung cancer by comparing contrast enhancement, contrast-related artifacts, image quality, and radiation dose.

Subjects and methods: In this randomized controlled crossover clinical trial, 77 patients who underwent 203 CT examinations were enrolled. All patients underwent at least two examinations performed with both protocols. Protocol A consisted of two acquisitions: one 35-second delayed CT acquisition for the chest followed by a 70-second delayed abdominal acquisition. Protocol B was a single 60-second delayed acquisition covering the chest and the abdomen. Attenuation and noise of the aorta, pulmonary artery, and liver were measured. Contrast-related artifacts, mediastinal lymph node visualization, liver enhancement, and noise were visually scored. Dose-length product was recorded. Statistical analysis was performed by t and chi-square tests and kappa statistics.

Results: Contrast-related artifacts were more severe at all evaluated levels, and visualization of lymph node regions was statistically significantly worse with protocol A. There were no differences in enhancement or noise score of the liver. Tumor delineation and pleural findings were better evaluated with delayed phase images. Dose-length product was significantly higher with protocol A (645.0 vs 521.5 mGy · cm; p < 0.0001).

Conclusion: A single 60-second delayed acquisition for thoracic and abdominal contrast-enhanced CT is associated with less contrast artifact and affords better visualization of lymph nodes at a lower radiation dose while acceptable vascular and hepatic contrast enhancement is maintained.