Issam Al-Najami1, Regina G H Beets-Tan, Gunvor Madsen, Gunnar Baatrup. 1. 1 Department of Surgery A, Odense University Hospital, Odense, Denmark 2 Institute of Clinical Research, University of Southern Denmark, Odense, Denmark 3 Department of Radiology, Netherlands Cancer Institute, Amsterdam, the Netherlands 4 Department of Clinical Pathology, Odense University Hospital, Odense, Denmark.
Abstract
BACKGROUND: An accurate method to assess malignant lymph nodes in the mesorectum is needed. Dual-energy CT scans simultaneously with 2 levels of energy and thereby provides information about tissue composition based on the known effective Z value of different tissues. Each point investigated is represented by a certain effective Z value, which allows for information on its composition. OBJECTIVE: We wanted to standardize a method for dual-energy scanning of rectal specimens to evaluate the sensitivity and specificity of benign versus malignant lymph node differentiation. Histopathological evaluation of the nodes was our reference. DESIGN: This was a descriptive and prospective study. SETTINGS: Seventeen rectal specimens were examined in 2 series. The first series was conducted with 3 specimens from patients who were not given perioperative contrast; 3 had iodine-based contrast and 3 had gadolinium-based contrast. We concluded that iodine was the contrast agent of choice and therefore included 8 more patients in a second series, given iodine-based contrast, for further analysis. PATIENTS: Quantitative imaging data were collected from 197 individual lymph nodes from 17 specimens, from patients with rectal cancer. MAIN OUTCOME MEASURES: We measured accuracy of differentiating benign from malignant lymph nodes by investigating the following: 1) gadolinium, iodine, and water concentrations in lymph nodes; 2) dual-energy ratio; 3) dual-energy index; and 4) effective Z value. RESULTS: Optimal discriminations between benign and malignant lymph nodes were obtained using the following cutoff values: 1) effective Z at 7.58 (sensitivity, 100%; specificity, 90%; and accuracy, 93%), 2) dual-energy ratio at 1.0 × 10 (sensitivity, 96%; specificity, 87%; and accuracy, 90%), 3) dual-energy index at 0.03 (sensitivity, 97%; specificity, 88%; and accuracy, 91%), and 4) iodine concentration at 2.58 μg/mL (sensitivity, 86%; specificity, 92%; and accuracy, 89%). LIMITATIONS: The investigation is conducted on isolated surgical specimens from rectal cancer operations. CONCLUSIONS: Dual-energy CT can be performed on rectal specimens. The discrimination between benign and malignant nodes seems promising when using iodine as contrast.
BACKGROUND: An accurate method to assess malignant lymph nodes in the mesorectum is needed. Dual-energy CT scans simultaneously with 2 levels of energy and thereby provides information about tissue composition based on the known effective Z value of different tissues. Each point investigated is represented by a certain effective Z value, which allows for information on its composition. OBJECTIVE: We wanted to standardize a method for dual-energy scanning of rectal specimens to evaluate the sensitivity and specificity of benign versus malignant lymph node differentiation. Histopathological evaluation of the nodes was our reference. DESIGN: This was a descriptive and prospective study. SETTINGS: Seventeen rectal specimens were examined in 2 series. The first series was conducted with 3 specimens from patients who were not given perioperative contrast; 3 had iodine-based contrast and 3 had gadolinium-based contrast. We concluded that iodine was the contrast agent of choice and therefore included 8 more patients in a second series, given iodine-based contrast, for further analysis. PATIENTS: Quantitative imaging data were collected from 197 individual lymph nodes from 17 specimens, from patients with rectal cancer. MAIN OUTCOME MEASURES: We measured accuracy of differentiating benign from malignant lymph nodes by investigating the following: 1) gadolinium, iodine, and water concentrations in lymph nodes; 2) dual-energy ratio; 3) dual-energy index; and 4) effective Z value. RESULTS: Optimal discriminations between benign and malignant lymph nodes were obtained using the following cutoff values: 1) effective Z at 7.58 (sensitivity, 100%; specificity, 90%; and accuracy, 93%), 2) dual-energy ratio at 1.0 × 10 (sensitivity, 96%; specificity, 87%; and accuracy, 90%), 3) dual-energy index at 0.03 (sensitivity, 97%; specificity, 88%; and accuracy, 91%), and 4) iodine concentration at 2.58 μg/mL (sensitivity, 86%; specificity, 92%; and accuracy, 89%). LIMITATIONS: The investigation is conducted on isolated surgical specimens from rectal cancer operations. CONCLUSIONS: Dual-energy CT can be performed on rectal specimens. The discrimination between benign and malignant nodes seems promising when using iodine as contrast.