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Elastography Imaging - Thyroid

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amy harrigan

on 26 November 2015

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Transcript of Elastography Imaging - Thyroid

Figure 1. This is an image demonstrating "eggshell" calcification surrounding a thyroid nodule (blue and white arrows). Adapted from "Figure 1", by Chen,, et al., 2010, Primary Squamous Cell Carcinoma of the Thyroid Gland With Eggshell Calcification, p. 1167.
THYROID NODULES
Nodules seen in up to
50-70%
of general population (Sebag et al., 2010)
5%
of the nodules are MALIGNANT

Patient Flow
Nodules felt on palpation/incidental finding
Ultrasound to decide if further assessment is needed
Suspicious nodules are indicated for a Fine Needle Aspiration
FNA Limitations
1) Cost
1500$ per exam (Luo et al, 2011)
300,000 thyroid exams per year (Luo et al. 2011)
=
450,000,000$
2) Invasive
Contraindicated for: needle phobias, bleeding disorders, anti-coagulant therapies, etc
3) Time Consuming
4) Most are NOT needed!
60-70% are benign - 5% malignant - 5-15% inconclusive - 15-25% suspicious (Hong et al., 2009)
The Problem
We are over-prescribing FNA's due to ambiguous findings with Grey Scale/Doppler Ultrasound
The Solution
How effective is
Shear Wave Elastography
as an adjunct to conventional ultrasound to rule out benign thyroid nodules?
GOAL:
Decrease the number of FNAs indicated which would have been benign anyways
What type of nodule is it?
Nodules
Grey Scale/Doppler US
SWE
FNA
What is Elastography?
How Does It Work?
Based on: Young's Modulus (E)
Young's Modulus = Stiffness
E = Stress/Strain
Units: Pascals
What Stress?
1) Mechanical Force
Manual compression
Carotid pulse
Axial Strain Elastography
2) Acoustic Radiation Force
Shear wave elastography
"Pushing beams"
Generate
shear waves/transverse
waves that are perpendicular to the push beam
Ultra-fast imaging system that acquires the speed of these waves, requiring up to 20,000 FPS (Sebag et al.,2010)
E = 3P
C
2
Faster speeds occur in stiffer materials and therefore increase shear wave speed = increase E
Conventional 2D Ultrasound
In general:

What do we look for?
Is Conventional US adequate?
Any single echo pattern cannot be considered
SPECIFIC
for malignancy (Ateria et al., 2008)
Interpreting the Results
Why Elastography?
Benign
Malignant
Table 1. Conventional US and elastography pattern with their associated specificity and sensitivity values.

Adapted from “TABLE 1” by Sebag et al., 2010, Shear wave elastography: a new ultrasound imaging mode for the differential diagnosis of benign and malignant thyroid nodules, p. 5285.
1) Qualitatively
2) Quantitatively
Chromatic scale
assigns color based on stiffness
Echogenecity
Calcifications
Nodular vascularity
"Halo sign"
Margins
The tissue of interest is color-coded according to its degree of strain
Features:


Anechoic/Hyperechoic
Uniform/thin halo
Regular margins
Egg shell calcifications

The colors that represent soft and hard may be altered by the sonographer
Figure 2. Ultrasound demonstrating a uniform thin halo surround a thyroid nodule. Adapted from "Figure 1" by Rago et al., 2008, Role of thyroid ultrasound in the diagnostic
evaluation of thyroid nodules, p. 915.
Features:
Figure 1. Qualitative & Quantitative Analysis
Adapted from “FIG. 2. B” by Sebag et al., 2010, Shear wave elastography: a new ultrasound imaging mode for the differential diagnosis of benign and malignant thyroid nodules, p. 5285.

Conclusion
E values (kPA) are calculated based on the measured speed of the shear waves
Figure 1. Qualitative & Quantitative Analysis
Adapted from “Fig. 1. D” by Veyrieres et al., 2012, A threshold value in Shear Wave elastography to rule out malignant thyroid nodules: a reality?. 81, p. 3967

A qualitative and quantifiable method of measuring
tissue stiffness



Qualitative
because it gives
as a color map of stiffness
distribution



Quantitative
because
it gives as definite
numbers
Stiff tissue


-58% malignant nodules= microcalcifcations
-16% benign nodules=microcalcifcations

RESULTS ARE NOT ALWAYS CONSISTENT
risk of malignancy
For example:

Asteria et al. (2008) studied 86 thyroid nodules and found the presence of microcalcifications is one of the
BEST SOLE PREDICTORS
for malignancy
Elastography Vs. Conventional Ultrasound
Problem:
Conventional ultrasound indicated too many FNA procedures to query malignancy in thyroid nodules
So what?
: FNAs are expensive, time-consuming, have contraindications, and most are not needed!
Solution:
Use SWE as a method to differentiate benign from malignant nodules in order to indicate less FNAs
References
1) Sebag et al. (2010)
Conventional Ultrasound:
Sensitivity 51.9%
Specificity 97%
Ultrasound + SWE:
Sensitivity 81.5%
Specificity 97%
2) Veyrieres et al. (2012)
Threshold at < 65 kPA benign
PRO:
QUANTITATIVE THRESHOLD
Threshold at < 66 kPA benign
Ultrasound + SWE
Sensitivity 97%

Figure 4. Qualitative assessment. Adapted from "Fig. 1. B", by Veyrieres et al., 2012, A threshold value in Shear Wave elastography to rule out malignant thyroid nodules: a reality?. 81, p. 3967
(1)
hypoechoic
absent halo sign
irregular margins
microcalcifications
intranodal blood flow
solid
shape

Figure 3. Microcalcifications. Adapted from "Figure 3 A", by Soto et al., 2010, Update in thyroid imaging. The expanding world of thyroid imaging and its translation to clinical practice, p. 287-298.
Figure 4. Intranodular blood flow. Adapted from "Figure 4 C", by Soto et al., 2010, Update in thyroid imaging. The expanding world of thyroid imaging and its translation to clinical practice, p. 287-298.
Thyroid Elastography: Relieving the
STRESS
on the Health Care System

Amy Harrigan & Michael Uy
Elastography WITH
Conventional Ultrasound
Conventional US:
Dimensions, echotexture, calcfications, location
Doppler US:
Vascular presence, velocity, RI, PI
+
Shear Wave Elastography:
Stiffness
=
More diagnostic criteria and confidence to rule out benign nodules!
= LESS FNAs!
to rule out benign nodules
=
More time, more convenience, more money!
= Quantifiable number
Why is that
important?
Asteria, C., Giovanardi, A., Pizzocaro, A., Cozzaglio, L., Morabito, A., Somalvico, F., & Zoppo, A. (2008). US-elastography in the differential diagnosis of benign and malignant thyroid nodules.
Thyroid, 18(5)
, 523-531. doi: 10.1089=thy.2007.0323

Bhatia, K. S., Tong, C. S., Cho, C. C., Yuen, E. H., Lee, Y. Y., & Ahuja, A. T. (2012). Shear wave elastography of thyroid nodules in routine clinical practice: preliminary observations and utility for detecting malignancy. European radiology, 22(11), 2397-2406. doi: 10.1007/s00330-012-2495-1

Darrin, C. (2015). Mod 1 Unit 8.Elastography.postable [PDF]. Retrieved from https://avenue.cllmcmaster.ca/d2l/le/content/144949/viewContent/1175601/View

Hegedüs, L. (2001). Thyroid ultrasound.
Endocrinology and metabolism clinics of North America, 30(2)
, 339-360.

Hong, Y., Liu, X., Li, Z., Zhang, X., Chen, M., & Luo, Z. (2009). Real-time ultrasound elastography in the differential diagnosis of benign and malignant thyroid nodules.
Journal of Ultrasound in Medicine, 28(7),
861-867.

Luo, S., Kim, E. H., Dighe, M., & Kim, Y. (2011). Thyroid nodule classification using ultrasound elastography via linear discriminant analysis.
Ultrasonics, 51(4)
, 425-431. doi:10.1016/j.ultras.2010.11.008

Pickerell, M., D. (2010). Elastography: The imaging of tomorrow.
Journal of Diagnostic Medical Sonography. 26(3)
, 109-113. DOI: 10.1177/8756479310370482

Rago, T., Santini, F., Scutari, M., Pinchera, A., & Vitti, P. (2007). Elastography: new developments in ultrasound for predicting malignancy in thyroid nodules.
The Journal of Clinical Endocrinology & Metabolism, 92(8)
, 2917-2922. doi: 10.1210/jc.2007-0641

Rago, T., & Vitti, P. (2008). Role of thyroid ultrasound in the diagnostic evaluation of thyroid nodules.
Best Practice & Research Clinical Endocrinology & Metabolism, 22(6)
, 913-928. doi:10.1016/j.beem.2008.09.016

Sebag, F., Vaillant-Lombard, J., Berbis, J., Griset, V., Henry, J. F., Petit, P., & Oliver, C. (2010). Shear wave elastography: a new ultrasound imaging mode for the differential diagnosis of benign and malignant thyroid nodules.
The Journal of Clinical Endocrinology & Metabolism, 95(12)
, 5281-5288. DOI: http://dx.doi.org/10.1210/jc.2010-0766

Veyrieres, J. B., Albarel, F., Lombard, J. V., Berbis, J., Sebag, F., Oliver, C., & Petit, P. (2012). A threshold value in Shear Wave elastography to rule out malignant thyroid nodules: a reality?. European journal of radiology, 81(12), 3965-3972. doi: 10.1016/j.ejrad.2012.09.002



Stiff =
STRESS
Strain
Soft =
STRESS
Strain
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