Shear Wave Elastography (SWE) of 724 cases of BREAST TUMORS

Dr THU DUY NGUYEN Dr HUNG THIEN NGUYEN Dr HAI THANH PHAN

MEDIC MEDICAL CENTER, HCMC,VIETNAM

MEDIC

OBJECTIVES:

To evaluate shear wave elastography of breast tumors in comparison to conventional ultrasound and BIRADS classification.

MATERIAL and METHODS

A descriptive, cross-sectional, prospective study.

In comparison the SWE  to conventional ultrasonography, mammography and biopsy (FNA and core biopsy) from November 2009 to November 2010 at Medic Medical Center.

Conventional ultrasound MEDISON with linear probe 10MHz, and Supersonic Imagine system, linear probe 15MHz.

724 breast tumors with 568 benign tumors and 156 malignant tumors .

Fig.1: A breast tumor with regular contour ( BIRADS III) on conventional US. On SWE system this tumor becomes BIRADS IV on B-Mode and the stiffness (hard).

Shear Wave Elastography technique

Shear Wave Elastography technique : interactions between acoustic waves and shear waves.

- SW # 10m/sec are generated in tissue and are caught by ultrafast imaging.- Process less than 20 sec.- Tissue elasticity (stiffness) presented as elastogram with quantitative values in kilopascals (kPa) units.Tissue stiffness in color range from red (very hard), orange, yellow, green and blue (soft).

- Elastic ratio (ER) = proportion of stiffness of lesion and surrounding (fatty tissue).

Fig.3: Mecanism of shear wave elastography (SWE).

kPa Benign tumors Malignant tumors

< 20 527

20 <30 27 4

30 <40 9 10

40 <50 5 32

50 <60 19

60 <70 12

> 70 79

With 724 cases:568 benign tumors (fibrocystic changes, fibroadenona, phyllodes tumors) # 78 % (4 to 45 kPa), with elastic ratio ER from 0.7 to 4.6.156 malignant tumors # 22 % (from 22 to 300 kPa), with ER from 3.3 to 26.4.

Nota: *kPa :stiffness with kiloPascal units*ER (elastic ratio): proportion of stiffness of tumor and surrounding tissue.

Results:Table 1: Distribution of elastic values of benign and malignant breast tumors.

Discussions:Diagnostic criteria= elastogram, dimension, homogeneity, elastic value, and elastic ratio.

1/156 cases of malignant tumor: most of cases with elastic value from 40kPa to 70kPa or more. 14 cases with elastic value less than 40kPa, but ER higher than 4 times.2/ Benign tumors with elastic value of 20kPa. 41 cases (#7%) more than 20kPa but lower than 45kPa: fibroadenoma with great dimension, huge phyllodes tumors (inhomogenous elastogram with blue color dominant).

3. Proposal management:

Breast tumors with BIRADS II-III, low stiffness, low ER : follow up.Breast tumors with BIRADS III and high stiffness: reclassified to BIRADS IV and biopsy.

Breast tumors with BIRADS IV and low stiffness:reclassified to BIRADS III and follow up. With a benign of biopsy result their results are not false negative.Elastogram analysis: very high kPa value, no need to check In case of low kPa, must refer elastic ratio (ER). The higher ER the higher possibility of malignancy.

4. Elastogram analysis :

Benign tumor = between blue and yellow code (from soft to hard) and homogenous.Malignant tumor: elastogram changes from yellow to red (hard) and homogenous. Because of central necrosis the center of tumor is always softer than (blue).So need to evaluate altogether elastic value (stiffness), elastic ratio and elastogram to gain an exact diagnosis.

Elastogram may help choosing the area of biopsy.

Fig.4: Fibroadenoma (BIRADS III) on B-mode and Elastogram (blue)

Fig.5: B-mode (BIRADS III)but so hard with elastogram, a ductal carcinoma (biopsy).

Fig.6: Microcalcification of ductal carcinoma on high resolution B-mode and Elastogram (hard) .

CONCLUSIONS:

Malignant tumor has elastic value of 40-70kPa and more.Benign tumor, under 20kPa.

SWE improves sensibility and speficity of ultrasound in diagnosing breast tumor and decreases the rate of breast biopsy.

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