CT Perfusion in Evaluation of Cervical Lymph Node Metastasis in Head and Neck Malignancies: A Cross-sectional Study

Abstract

Introduction: Though, many cross-sectional modalities are available for evaluation of cervical lymph node metastasis but their results are highly variable. There is paucity of the literature in India, regarding lymph nodal assessment using Computed Tomography (CT) perfusion in head and neck malignancies even though, there is high incidence of oral cancer in India. Aim: To assess the role of Computed Tomography Perfusion (CTP) in evaluation of cervical lymph nodes in head and neck malignancies, by using CT perfusion parameters as compared to histopathology. Materials and Methods: This cross-sectional study was conducted in the Department of Radiodiagnosis in collaboration with the Department of Surgery and Pathology at Vardhman Mahavir Medical College and Safdarjung Hospital, Delhi, India, from October 2017 to April 2019. The study included 30 newly diagnosed head and neck cancer patients, with 46 nodes planned for surgical neck dissection. Computed tomography scan of neck was acquired using Siemens Somatom Definition Flash 256CT scanner. Reconstruction and post processing was performed on workstation and perfusion parameters were obtained to generate the CT perfusion maps. Differentiation between benign and malignant lymph nodes was done, on the basis of CT perfusion parameters such as Blood Flow (BF), Blood Volume (BV), Mean Transit Time (MTT) and Permeability Surface (PS), which were compared with histopathological findings of resected lymph nodes. McNemar’s test was applied for comparison and statistical analysis. Receiver Operating Characteristic (ROC) curve of quantitative parameters were obtained, for the detection of sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPP) and diagnostic accuracy. Results: Out of 46 nodes, 23 were metastatic and 23 were non metastatic. The average value of BF in metastatic nodes was 174.61±71.76 mL/100g/min, BV was 16.32±11.9 mL/100g, MTT was 4.83±2.54 seconds and PS was 49.3±28.59 mL/100g/min. The average values for non metastatic nodes were: BF 88.06±34.4 mL/100g/min, BV: 9.89±7.63 mL/100g, MTT: 13.11±18.58 seconds and PS: 37.07±29.26 mL/100g/ min. The differences between the parameters like blood flow (p-value <0.0001), blood volume (p-value=0.005) and MTT (p-value=0.002) in malignant and benign nodes were significant. In case of blood flow, sensitivity was 82.61% and diagnostic accuracy was 84.78%. In case of blood volume, sensitivity was 91.30% and diagnostic accuracy was 73.91%. In case of mean transit time, sensitivity was 56.52% and diagnostic accuracy was 73.91%. In case of permeability surface, sensitivity was 91.30% and diagnostic accuracy was 67.39%. Conclusion: Blood flow and blood volume values were significantly increased in metastatic cervical lymph nodes as compared to non metastatic nodes, whereas MTT was significantly low. Permeability surface showed equivocal results.