Detection of small inflammatory and metastatic lymph nodes in rabbits by sonography: evaluation with the resistive index ratio.
OBJECTIVE
The aim of this prospective study was to determine whether the resistive index (RI) ratio based on high-resolution spectral Doppler sonography would be useful in the differential diagnosis of small inflammatory and metastatic lymph nodes in rabbit models.


METHODS
The infected and metastatic lymph node models we used were created by subcutaneously inoculating methicillin-susceptible Staphylococcus aureus and VX2 tumor cells respectively into the left hind limbs of 10 New Zealand White rabbits. High-resolution sonography was performed to investigate the popliteal fossa lymph nodes 2 weeks after the inoculation. The sizes, long-/short-axis ratios, and RI ratios (defined as the value of the peripheral RI relative to the central RI) of the nodes were evaluated with sonography and then compared with the histopathologic findings.


RESULTS
No statistical differences were found between the volumes (mean +/- SD, 104 +/- 41 versus 87 +/- 24 mm(3); P > .05) and the long-/short-axis ratios (1.97 +/- 0.28 versus 2.03 +/- 0.26; P > .05) of 15 inflammatory and 14 metastatic lymph nodes. On spectral Doppler sonography, the RI ratio was higher in the metastatic lymph nodes than in the inflammatory lymph nodes. With an RI ratio higher than 1.2 as a diagnostic criterion for a metastatic lymph node, the sensitivity, specificity, and positive and negative predictive values of sonography were 71% (10/14), 80% (12/15), 76% (10/13), and 75% (12/16), respectively, with an area under the receiver operating characteristic curve value of 0.824.


CONCLUSIONS
This experimental study confirms that RI ratio changes based on high-resolution spectral Doppler sonography are associated with histopathologic changes of metastatic and inflammatory lymph nodes during the initial stage in rabbits.
Huang
Ying
Y
Department of Ultrasound in Medicine, Shanghai Jiaotong University Affiliated Sixth People's Hospital, Shanghai, China.
Hu
Steven Bing
SB
Wu
Rong
R
Xu
Fan-Hua
FH
D000818:Animals; D007091:Image Processing, Computer-Assisted; D007249:Inflammation / Q000382:microbiology; D008198:Lymph Nodes / Q000000981:diagnostic imaging* / Q000382:microbiology; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D012372:ROC Curve; D011817:Rabbits; D011897:Random Allocation; D012680:Sensitivity and Specificity; D018608:Ultrasonography, Doppler