This poster is published under an
open license. Please read the
disclaimer for further details.
Keywords:
Thyroid / Parathyroids, Elastography, Outcomes analysis, Metastases
Authors:
W. S. Jung1, J.-A. Kim2, E. J. Son2, J. H. Youk2, C. S. Park1; 1 Seoul/KR, 2Seoul/KR
DOI:
10.1594/ecr2014/C-0489
Methods and materials
Patient
-75 patients with PTC with 93 enlarged cervical lymph nodes underwent conventional neck ultrasonography and SWE for preoperative or postoperative evaluation of cervical lymph nodes between May 2011 and December 2012.
-Lymph nodes were considered suspicious when one of the suspicious ultrasound findings (loss of fatty hilum,
calcifications,
cystic change,
hyperechogenicity,
and round shape) was present.
-SWE was performed at lymph nodes showing suspicious US features before US-FNAB (n=22),
preoperative lymph node marking (n=46) or staging US (n=25) for surgery.
-Of 93 lymph nodes,
9 lymph nodes were excluded because there was no subsequent surgical excision of the lymph nodes with cytologic reports suggestive of malignancy on FNAB.
-Finally,
84 lymph nodes in 66 patients (M:F=16:50,
mean age M:F=52.5:43.7) were included in this analysis.
SWE imaging
-Patients initially underwent conventional neck US using a linear 15–4 MHz transducer and US category of probably benign or suspicious was assigned to the lymph nodes.
-SWE was performed for the suspicious lymph nodes on conventional US.
-SWE was performed in dual mode,
i.e.,
elastograms displayed alongside gray-scale US in real-time and using default elasticity settings of acoustic impulse intensity,
smoothing,
persistence and kPa display scale (0 to 180 kPa; measurements were independent of the selected display maximum).
-In this regard,
blue and red areas on elastograms corresponded to comparatively low kPa (soft) and high kPa (stiff) regions,
respectively.
-For each selected static image,
the stiffest region in the node was selected by visual inspection,
onto which a circular electronic region of interest or Q-box (trademark by Supersonic,
Imagine,
Inc) 1 or 2mm in diameter was placed.
-The software generated several indices for each Q-box,
of which mean (Emean),
minimum (Emin) and maximum (Emax) elasticity value (kPa) were recorded.
-We also measured the elasticity index (EI) of the surrounding muscles to obtain an EI ratio (Emean-m) of the Emean of lymph nodes and surrounding muscles.
Histopathologic diagnosis
-Pathologic reports were divided into benign and metastatic lymph nodes by FNA only cytologic (n=9) or surgical reports (n=75).
-When metastasis was suggested by FNAB,
surgical dissection of the lymph nodes was performed.
-Surgical dissection included lymph node sampling,
internal jugular neck node dissection and modified radical neck node dissection.
-Histopathologic findings of the metastatic lymph nodes including number,
largest size,
the ratio of the No.
of metastatic LNs divided by the number of dissected lymph nodes and the extranodal extension were reviewed by surgical specimen.
Statistical analysis
-SWE EI of Emean,
Emin,
Emax and Emean-m of lymph nodes were correlated with the pathologic results and the histopathologic findings of the metastatic lymph nodes.
-The Student’s t-test and Mann-Whitney U test were used to determine the differences of SWE EI between metastatic and benign lymph nodes.
-Correlations between SWE indices and the histopathologic findings of metastatic lymph nodes were analyzed using Spearman’s correlation coefficients and Mann-Whitney U test.
-Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance by SWE score and B-mode US category (BUS) for predicting metastasis.
-We compared the diagnostic performance between US category and SWE EI or combined SWE EI+US using area under the curve (AUC) values with 95% confidence interval (CI) by logistic regression analysis with GEE (Generalized Estimating Equation).