Visibility of the hilar lymph nodes using advanced virtual monoenergetic low-keV images for preoperative evaluation of lung cancer

Abstract

Objective: The purpose of our study was to evaluate the visibility of the hilar lymph nodes (LNs) using advanced virtual monoenergetic low-keV images compared with early-phase contrast-enhanced CT. Methods: Dual energy contrast-enhanced CT was performed for pre-operative evaluation of lung cancer at 20 and 60 s after administration of contrast media in 50 patients (32 males and 18 females; mean age, 69 years). Five kinds of images (A: 20 s/120 kV; B: 60 s/40 keV; C: 60 s/50 keV; D: 60 s/120 kV; E: 60 s/100 kV) were reconstructed. We measured the CT number of the bilateral main pulmonary arteries (PAs), pulmonary veins (PVs) and hilar LNs, and evaluated the differences in CT number (Hounsfield units, HUs) between the PA/PV and LNs (PA–LN and PV–LN contrast). Artifacts from the superior vena cava (SVC) were also evaluated. Results: The mean PA–LN contrast (HU) was 415 in image group A, 299 in B, 180 in C, 80 in D, and 100 in E. The mean PV–LN contrasts in each group were 306, 287, 177, 78, and 99, respectively. Image group B showed the second highest PA–LN contrast following image group A. There was no significant difference in the PV–LN contrast between image groups A and B. The PA–LN and PV–LN contrasts of image groups B and C were significantly higher than those of E. SVC artifacts were lower in the delayed-phase images (Group B–E) than in Group A. Conclusion: To evaluate the hilar LNs with a single image series, advanced virtual monoenergetic 40-keV imaging at the delayed 60-s phase seems to be the most valuable. Advances in knowledge: Advanced virtual monoenergetic image is useful for evaluation of both hilar LNs and tumors in the delayed phase without artifact derived from the streak artifact from dense contrast media in the SVC.

Improvement of image quality of laryngeal squamous cell carcinoma using noise‐optimized virtual monoenergetic image and nonlinear blending image algorithms in dual‐energy computed tomography

“…Besides, the iodine contrast increase obtains at low keV levels, resulting from a shift of the energy spectrum towards the physical absorption maximum of iodine, and the 40 keV is more closely approximate the k‐edge of iodine (33 keV) 22,23 . Therefore, VMI+ algorithm at 40 keV showed the highest CNR and best tumor delineation in laryngeal SCC in our study, which was similar to previous studies regarding liver lesions, peritoneal metastatic deposits, and lung cancer 24–27 . In the aspect of overall image quality of laryngeal SCC, NBI algorithm showed the best performance.…”

“…22,23 Therefore, VMI+ algorithm at 40 keV showed the highest CNR and best tumor delineation in laryngeal SCC in our study, which was similar to previous studies regarding liver lesions, peritoneal metastatic deposits, and lung cancer. [24][25][26][27] In the aspect of overall image quality of laryngeal SCC, NBI algorithm showed the best performance. As the NBI algorithm optimizes the contrast and image noise in a pixel-by-pixel manner, the image contrast can be further enhanced on high-attenuation pixels, while image noise can be reduced on low-attenuation pixels.…”

Application of Dual-Energy Spectral Computed Tomography to Thoracic Oncology Imaging

“…2) (11,12). A recent study proved that VMI at 40 keV performed at a delayed phase (60 seconds after contrast media administration) was useful for the evaluation of hilar LNs, showing the greatest contrast differences between the pulmonary vessels and LNs (13).…”

Dual-Energy Computed Tomography for the Diagnosis of Mediastinal Lymph Node Metastasis in Lung Cancer Patients: A Preliminary Study

“…Previous studies have demonstrated that the tumor signals reached a peak at 40 keV in VMIs 19 . Sekiguchi et al 9 also found that the VMI at 40 keV was the most valuable for evaluating hilar LNs. Therefore, we speculated that tumors and their adjacent tissues showed a higher attenuation difference in VMIs at the lower energy levels than at the higher energy levels, which is helpful for tumor detection 20 …”

“…In this study, we selected the venous phase images for all analyses because previous studies showed that they were the most valuable 9,10 . The image analysis was performed on a specific software (syngo.via, version VA30A; Siemens).…”