First Pass Dual Input Volume CT-perfusion of Lung Lesions: The Influence of the CT- Value Range Settings on the Perfusion Values of Benign and Malignant Entities

Objective: To assess the influence of the lower threshold for segmentation of the volume of interest on the perfusion values in first-pass dual input volume CT-perfusion of lung lesions.

Materials And Methods: Dual input maximum slope volume CT-perfusion was performed in 48 patients (mean age±standard deviation [SD], 68±10years; range, 46-87 years) who underwent subsequent CT-guided biopsy to evaluate a lung lesion. Using commercial perfusion software, a lower and upper threshold was set for determination of the CT-value range, which again determined the volume of interest for perfusion calculation. The pulmonary arterial flow (PAF), bronchial arterial flow (BAF), and perfusion index (PI; PAF/(PAF+BAF)) were calculated at following pre contrast CT value range settings: -80 to 150HU (setting 1), -200 to 150HU (setting 2), -300 to 150HU (setting 3), and -500 to 150HU (setting 4). Perfusion parameters were compared between benign (n, 15) and malignant (n, 33) lesions for each setting. Intraobserver- and interobserver reliability were calculated for setting 4.

Results: Median PAF was significantly higher in malignant lesions than in benign lesions for all settings (53-96 versus 29-62mL/min/100mL, P<0.05). There was no significant difference in BAF between malignant and benign lesions. Median PAF of all lesions was significantly influenced by the CT value range setting (P<0.05), whereas the values increased from setting 1 to 4. Intraobserver analysis as well as interobserver analysis of PAF at setting 4 showed excellent reliability (Cronbach's alpha 0.98 and 0.95, respectively, P<0.01).

Conclusion: PAF derived from first-pass dual-input maximum slope volume CT perfusion is statistically significantly higher in malignant than in benign lesion, whereas the measurements are influenced by the lower threshold of the CT value range setting. This has to be considered when using cutoff values provided in the literature for differentiation between benign and malignant lung lesions.