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Fig.1 Distributions of the SUVmax (A), short axis diameter (B), LPR (C), and median HU value (D) of the mediastinal LNs according to the histopathology​

Fig.2 Evaluation of mediastinal LN metastasis by FDG uptake and a volumetric CT histogram. (B) An LN at station 7 shows mild FDG uptake with SUVmax of 2.3 and median density of 39.0 HU, and was confirmed as a metastatic lesion. (C) An LN at the 4R station shows increased 18F-FDG uptake with SUVmax of 5.9 and median density of 78.9 HU, and was confirmed as a benign LN.​

Fig.3 Scatter plots for SUVmax and the median HU value in LNs with an SUVmax ≤ 4.0 (A) and in LNs with an SUVmax > 4.0 (B)​

Abstract

OBJECTIVES:

To evaluate the clinical implications of lymph node (LN) density on 18F-FDG PET/CT for mediastinal LN characterization in non-small cell lung cancer (NSCLC).

METHODS:

One hundred and fifty-two patients with 271 mediastinal LNs who underwent PET/CT and endobronchial ultrasound-guided transbronchial needle aspiration for staging were enrolled. Maximum standardized uptake value (SUVmax), short axis diameter, LN-to-primary cancer ratio of SUVmax, and median Hounsfield unit (HU) based on CT histogram were correlated to histopathology.​ 

RESULTS:

Of 271 nodes, 162 (59.8 %) were malignant. SUVmax, short axis diameter, and LPR of malignant LNs were higher than those of benign nodes. Among malignant LNs, 71.0 % had median HU between 25 and 45, while 78.9 % of benign LNs had values <25 HU or >45 HU. Using a cutoff value of 4.0, SUVmax showed the highest diagnostic ability for detecting malignant LNs with a specificity of 94.5 %, but showing a sensitivity of 70.4 %. Using additional density criteria (median HU 25-45) in LNs with 2.0< SUVmax ≤4.0, the sensitivity increased to 88.3 % with the specificity of 82.6 %.

CONCLUSIONS:

LN density is useful for the characterization of LNs with mild 18F-FDG uptake. The risk of mediastinal LN metastasis in NSCLC patients could be further stratified using both 18F-FDG uptake and LN density.

KEY POINTS:

• SUVmax showed the highest diagnostic ability for detecting malignant LNs. • LN density was useful in characterization of LNs with mild FDG uptake. • SUVmax and LN density together could stratify the risk of LN metastasis.​ 

Author information​

Lee JW1, Kim EY2, Kim DJ3, Lee JH4,5, Kang WJ6, Lee JD7, Yun M6.

1Department of Nuclear Medicine, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, Korea.

2Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea.

3Department of Thoracic and Cardiovascular Surgery, Yonsei University College of Medicine, Seoul, Korea.

4Department of Nuclear Medicine, Yonsei University College of Medicine, Seoul, Korea. docnuke@yuhs.ac.

5Department of Nuclear Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, 211 Eonju-Ro, Gangnam-Gu, Seoul, 06273, Korea. docnuke@yuhs.ac.

6Department of Nuclear Medicine, Yonsei University College of Medicine, Seoul, Korea.

7Department of Radiology, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, Korea.