Hounsfield units upon PET/CT are useful in evaluating metastatic regional lymph nodes in patients with oesophageal squamous cell carcinoma

Abstract

Objectives: This study evaluated the usefulness of measurements of X-ray attenuation (in Hounsfield units) obtained from unenhanced CT images for attenuation correction of the positron emission tomography (PET) data from PET/CT in the assessment of regional lymph node metastasis in oesophageal squamous cell carcinoma. Methods: 17 patients with oesophageal squamous cell carcinoma underwent surgery after evaluation with PET/CT. After the excised lymph nodes were reviewed, we compared the histopathology and PET/CT findings, and analysed the lymph node metastasis. When 18-F fludeoxyglucose (FDG) uptake in the lymph nodes was focally prominent in comparison with background mediastinal activity (regardless of lymph node size), the lymph nodes were considered to be positive for malignancy by PET/CT. The mean Hounsfield units of mediastinal lymph nodes showing abnormally increased FDG uptake in PET/CT was retrospectively evaluated using images from the unenhanced CT component of PET/CT. Receiver operating characteristic (ROC) curve analysis was applied to determine the optimal cut-off value of mean Hounsfield units for detecting individual lymph node metastases. Results: For depiction of malignant nodal groups in each lymph node group, the sensitivity, specificity and accuracy of PET/CT based on increased FDG uptake were 58.8%, 74.5% and 70.8%, respectively. For patients with nodal groups that were positive for uptake by PET/CT, the mean attenuation in lymph nodes as measured by CT was 48¡13 HU for malignant nodes and 75¡18 HU for benign nodes. This difference was statistically significant (p,0.001). Using ROC curve analysis, we determined the cut-off as 71 HU. When we excluded lymph nodes with attenuation higher than 71 HU from the nodes determined as malignant by PET/CT, the specificity and accuracy for detecting metastatic lymph nodes improved to 90.9% and 83.3%, respectively. Conclusions: When interpreting lymph node metastasis in oesophageal squamous cell carcinoma using PET/CT, the assumption that any lymph node with mean HU.71 is benign can improve diagnostic accuracy.

Distinguishing Lymphomatous and Cancerous Lymph Nodes in 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography by Radiomics Analysis

“…Fifth, we used a wide range (between −1000 and 3000 HU) for intensity discretization of CT images, based on our previous study findings [33]. is is outside the general HU range of lymph nodes [62] and may have an impact on TA in CT. However, given the relatively good results of both the previous and current studies, we believe that these effects are likely to be minor.…”

Potential Pitfall in the Assessment of Lung Cancer with FDG-PET/CT: Talc Pleurodesis Causes Intrathoracic Nodal FDG Avidity

“…It is unclear why only 11 of 44 (25%) patients showed high-attenuation nodes, even when all demonstrated high-attenuation pleural thickening. The threshold of 100 HU we established for presuming talc deposition reflected the intrinsic high-attenuation of talc ( Figure 3 ) and published data suggesting that benign nodes are typically higher (on average 75 HU) attenuation than metastatic nodes [ 8 ]. It is likely that if the attenuation threshold was lower, we could have detected a higher rate of involvement, although the specificity for talc involvement and confidence for excluding metastases would similarly be lower.…”

Hounsfield units from unenhanced 18F-FDG-PET/CT are useful in evaluating supradiaphragmatic lymph nodes in children and adolescents with classical Hodgkin’s lymphoma

“…In the study by Kim et al, it was shown that the XRA for metastatic nodes was significantly lower than for unaffected nodes. 28 In our study, we evaluated the unenhanced component of 18F-FDG-PET/CT. One undoubted advantage is the low dosage of X-rays used, which is important due to the young age of patients and the need for periodic examinations in the monitoring of the disease.…”