2012 Proceedings - International Tissue Elasticity Conference

002 ANALYSIS OF THYROID NODULES VISCOELASTICITY WITH TIME STRAIN CURVES MAY
SURPASS CLASSICAL QUALITATIVE AND SEMI–QUANTITATIVE EVALUATION.
Rafal Z Slapa 1 , Bartosz Migda 1 , Wiesław S Jakubowski 1 , Jacek Bierca 2 ,
Jadwiga Slowinska–Srzednicka 3 .
1 Diagnostic Imaging Department, Medical University of Warsaw, Faculty of Medicine II with
English and Physiotherapy Divisions, Warsaw, POLAND; 2 Surgery Department, Solec Hospital,
Warsaw; POLAND; 3 Endocrinology Department, Center for Postgraduate Medical Education,
Warsaw, POLAND.
Background: It is assumed that elasticity is linear with deformation in the range of 1%. However,
observation of time–strain curves of thyroid nodules subjected to free–hand strain elastography indicates
both linear and non–linear portions of relaxation.
Aims: The purpose of the study was to evaluate a new linear/non–linear approach for strain elastography
of thyroid nodules based on the analysis of time strain curves and compare it with classical elasticity
score and thyroid strain ratio methods.
Methods: During 2009–2011, 67 patients scheduled for thyroidectomy (62 with multinodular goiter and
5 with a single thyroid nodule) were evaluated with B–mode and power Doppler ultrasound of the whole
thyroid and neck lymph nodes. During the ultrasound examination, 96 dominant nodules were examined
with strain elastosonography with Aplio XG (Toshiba, Japan) with a linear 5–17MHz transducer. The
stiffness of each thyroid nodule was evaluated on the pair of images with classical features of strain
elastosonography qualitatively (with elasticity scores) and semi–quantitatively with thyroid tissue
strain/nodule strain ratios with application of elasto Q (Toshiba, Japan). Moreover, a novel, original
approach to elasticity data based on evaluation of time strain curves (elasto Q) was applied.
Results: The incidence of thyroid cancer that was not known before our ultrasound examination
(5 nodules) in our study shows that cancer is present in 9% of the 54 patients. Final diagnosis
established 7 papillary carcinomas (6 in multinodular goiter), 4 follicular adenomas and 85 benign
nodular goiter nodules. Classical elastographic analysis with elasticity score and elasticity ratio on
statistical analysis did not show a significant difference between cancer and benign nodules
(p–value=0,431 and 0,156, respectively). On linear/non–linear analysis of time strain curves, excellent
differentiation (p=5.6x10–9) was possible with new parameter: the Relative Length of Non–Linear
Relaxation (with threshold 0.5, sensitivity 100% and specificity 85.4%, area under ROC=0.975).
Conclusions: (1) The incidence of thyroid cancer that was not known before our ultrasound examination
in our study is comparable to the incidence of cancer in the general population of multinodular
goiter patients even though the number of cancers in the study is small. (2) The analysis of linear
and non–linear elastography data may greatly improve differential diagnosis of thyroid nodules. (3)
Different timing for conversion from linear to non–linear relaxation between papillary thyroid cancer and
benign thyroid nodules may indicate that viscosity may be the differential factor. (4) Further multicenter
large scale studies evaluating the usefulness of linear/non–linear elastography phenomena in differential
diagnostics of thyroid cancer are warranted. Studies involving evaluation of vioscoelasticity (e. g., shear
wave spectroscopy) could be applied to investigate the model of thyroid nodules differentiation.
Acknowledgements: I would like to thank Dr. Jeffrey Bamber and other lecturers at 10th ITEC 2011 in Arlington for
inspiration. Supported by the Ministry of Science and Higher Education of Poland grant Nr N N402 476437, 2009–12.
Figure 1: Papillary carcinoma of the thyroid in patient with
nodular goiter. Elasticity score=1 and thyroid
tissue/nodule strain ratio=0.3 both indicate benign
lesion. Relative Length of Non–Linear Relaxation=0.8
truly indicates malignant lesion.
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Figure 2: Benign thyroid nodule in patient with nodular goiter.
Elasticity score=3 and thyroid tissue/nodule strain
ratio=2.8 both indicate malignant lesion. Relative
Length of Non–Linear Relaxation=0.3 truly indicates
benign lesion.
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