SIR 2024
Imaging
Leening P. Liu, B.S.
graduate student
University of Pennsylvania
Disclosure information not submitted.
Alexey Gurevich, MD, MS
Resident
Division of Interventional Radiology, Department of Radiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA
Financial relationships: Full list of relationships is listed on the CME information page.
Peter B. Noël, Ph.D.
associate professor
University of Pennsylvania
Disclosure information not submitted.
Maxim Itkin, MD, FSIR (he/him/his)
Professor of Radiology
Perelman School of Medicine at the University of Pennsylvania, Hospital of the University of Pennsylvania
Financial relationships: Full list of relationships is listed on the CME information page.
CT lymphangiography is a novel imaging method and crucial for diagnosis of the lymphatic diseases. Spectral CT can provide superior imaging of central lymphatic structures by separating and quantifying iodinated contrast agents compared to MR lymphangiography. We evaluate the feasibility of in vivo lymphatic system imaging using spectral CT.
Materials and methods:
Bilateral superficial inguinal lymph nodes of a Yorkshire pig were injected at 0.1 mL/s with 20 mL of iodinated contrast agent (Isovue-300, Bracco Diagnostics). The pig was simultaneously scanned with a second-generation dual-layer spectral CT (Spectral CT 7500, Philips Healthcare) at a tube voltage of 140 kVp and an exposure of 300 mAs approximately every 45 s for 12 minutes. Both conventional images and iodine density maps were reconstructed at a slice thickness of 0.67 mm and a field of view of 350 mm, and respective contrast to noise ratio (CNR) was measured with a background region of interest of muscle. To visualize the complete path from the superficial inguinal lymph nodes to the lymphovenous junction, maximum intensity projections (MPR) of the iodine density maps were generated. Additionally, mean and standard deviation of iodine density distal to the lymphovenous junction were measured at each time point to characterize washout.
Results:
Compared to conventional images, iodine density maps demonstrated a 20-fold increase in CNR from 43 to 895. These maps 3.5 minutes after the contrast injection illustrated the full pathway from the superficial inguinal lymph nodes through the cisterna chyli and thoracic duct before finally draining into the venous system at the lymphovenous junction. Washout of contrast on iodine density maps was present at later time points and was most notable distal to the junction. Iodinated contrast was first detected at 38 mg/mL, the maximum reliable iodine density, and decreased to 4.70 ± 0.06 mg/mL at 11.5 minutes post injection.
Conclusion: Spectral CT generated iodine density maps that not only visualized the lymphatic system but also quantified the decrease in iodinated contrast as it drained into the venous system. This high contrast imaging capability of spectral CT enables further investigation of the anatomical structures and kinetics of the lymphatic system, particularly at the lymphovenous junction.