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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5791_Библиотеки_им_академика_М_И_Перельмана.pdf
Fig. 4.10 Compression of
the area of interest with an
US probe. ( a ) Image. ( b )
Graphic
914.7 Ultrasound Elastography
a
b
3. Sonoelastography based on outer vibration
(vibroelastography).
4. Elastometry, where the velocity of shear-wave
propagation through the tissue is being analyzed to calculate elastic modulus.
The mode of elastography depends on a scanner and can be conducted in real time or by means
of data postprocessing. Breast tissue is exposed
to external compression with an US probe
(Fig.
4.10 ).
92
4 Ultrasound Diagnosis of Breast Cancer
Fig. 4.11 Scheme of elastography imaging
US probe is positioned perpendicularly to the
skin over the lesion. Compression time varies
from 2 to 5 s. Periodic compression is performed
to obtain several images with minor artifacts. The
analyzed area should necessarily contain some
normal breast tissue for correct comparison with
the stiffness of the lesion. Time expense to the
examination is usually 1–5 min. The overall time
for breast US with elastography does not exceed
routine 10–20 min.
Tissues under the US probe are deformed with
compression (strain). Abnormal tissues exhibit
unique features – malignant tumors are “hard” as
compared with surrounding normal tissues
4.11 ).
(Fig.
Elastogram is an image, which results from
overlaying of the “compressive” image onto the
grayscale image. Tissue elasticity image is coded
with shades of gray or color palettes. Hard structures are usually colored with dark or blue. Soft
areas are usually marked with light or red.
Intermediate colors are applied, respectively.
Scanners usually offer several color maps, such
as “blue-green-red,” shades of gray, or customized maps with shades of red or other colors
(Fig. 4.12 ).
Uniform compression of the whole breast is
impossible due to comparatively small size of
US probe. Normal breast parenchyma with
moderate compression exhibits relatively regular,
homogeneous, and symmetric fi ne-grained pattern (Fig.
4.13 ). Compression of individual
breast segments or lesions is performed more
effectively.
Quantitative and qualitative diagnostic criteria for the assessment of sonoelastography are
developed. Qualitative criterion is the analysis of
distribution of breast tissue elasticity, and quantitative – strain ratio – is the rate of deformation of
breast lesion in comparison with normal surrounding tissues (Rozhkova et al. 2011 ; Sencha
et al. 2011 ) .
Lesions are usually classi fi ed with elastography into groups according to the following features (Sencha et al. 2009 ) :
1. Presence or absence of color pattern within
the lesion and its intensity
2. Character of staining (hard, mixed, another)
3. Regularity of staining (homogeneous, hetero-
geneous)
4. Dimensions of the stained area in comparison
with the dimensions of the same lesion in
grayscale US
5. Degree of differentiation of the staining with
surrounding tissues
Ei Ueno (1996) suggested the classi fi cation
that aims to differentiate benign and malignant
lesions and is based on color pattern with elastography (Table 4.1 ).
Zubarev ( 2009 ) reports fi ve types of stiffness
of lesions depending on color pattern with US
elastography. Dark blue (stiff) staining that corresponds to the fi fth type of color pattern is characteristic for breast carcinoma. The data obtained
with sonoelastography facilitate differential diagnosis of breast lesions of tumoral nature in complex and doubtful cases.
Rozhkova et al. ( 2011 ) add two more types of
pattern: three leveled, which is characteristic for
fl uid-containing lesions, and mosaic. Malignant
breast lesions, according to the authors, are
characterized by the fourth and fi fth types
according to Ueno classi fi cation in 78.6 %. The
fourth type was identi fi ed in 62.5 % of breast
carcinoma and was characterized by homogeneous blue staining of the tumor with normal
elasticity of surrounding tissues. The fi fth type
of sonoelastogram, which is characteristic only
934.7 Ultrasound Elastography
a
Fig. 4.12 US elastography. Coloration examples. ( a ) Blue-green-red scale. ( b ) Yellow-red scale. ( c ) Shades of gray
94
4 Ultrasound Diagnosis of Breast Cancer
b
c
Fig. 4.12 (continued)
for cancer, re fl ected typical features of dense
lesions with in fi ltrating growth. Benign breast
lesions, according to the authors, are characterized
by the fi rst, second, sixth, and seventh types of
elastogram depending on the contents in 85.2 %
of cases.
954.7 Ultrasound Elastography
Fig. 4.13 Elastography. Normal breast
96
4 Ultrasound Diagnosis of Breast Cancer
Table 4.1 Classi fi cation after Ueno ( 1996 )
Benign
Score 1 Entire area is
evenly shaded
green, as is
surrounding tissue
Score 2 Lesion area shows
a mosaic pattern
of green, blue,
and red
Intermediate
Score 3 Central part of the
area is blue (stiff),
and peripheral
part is green (soft)
Malignant
Score 4 Entire area is blue
(stiff)
Score 5 Entire area and its
surrounding area
are blue (stiff)
Our own research demonstrated that breast
carcinoma is more often (in 76.1 %) characterized by intense, well-circumscribed hard (stiff)
staining (Fig. 4.14 ). Mixed (blue-green-red) pat-
tern was observed in 12.5 % (Fig. 4.15 ).
Additionally, 81.8 % of breast lesions exhibited
irregular color pattern (Fig. 4.16 ).
Figures 4.17 and 4.18 illustrate color patterns,
intensity, and homogeneity of breast neoplasms
with elastography, obtained in our research.
Ef fi cacy of elastography in thyroid malignancy is demonstrated in Table 4.2 . It demon-
strates that combined use of elastography and
B-mode signi fi cantly increases the accuracy in
the diagnosis of breast cancer.
Differences in size of 0.5–10 mm between grayscale and elastographic images of the lesion were
observed in 22.7 % of cases. Among them, the lesion
in 85 % was larger with elastography as compared
with grayscale image, while in 15 % of cases, they
appeared slightly smaller (Figs. 4.19 and 4.20 ).
According to our data, elastography fails to
differentiate breast lesions in 11.4 % of patients.
It is a consequence of absence of color pattern
within the lesion, no difference between color
patterns of the tumor and surrounding structures,
or expressed artifacts (Fig. 4.21 ).
US elastography in 15.9 % of cases of breast
carcinoma supplied additional diagnostic information to other US modalities. The increase in
diagnostic value was a consequence of the following factors:
Speci fi cation of the size of the lesion (dye to •
precise differentiation of invasion margins
and the expression of perifocal induration).
The difference of the dimensions of color-
ation is explained by merging of malignant
tumors into surrounding tissues. This per-
mits differentiation from benign lesions, the
latter usually having a capsule. The region
of malignant invasion exhibits abnormal
strain characteristics as compared with intact
tissue that is observed on the monitor of US
scanner and corresponds to Score 5 by Ueno
classi fi cation. The dimensions of malignant
lesions with sonoelastography can be 60 %
larger than the cor responding dimensions in
B-mode.
Analysis of the uniformity of inner structure •
of the lesion (variation of elasticity).
Speci fi cation of interrelation of the lesion •
with surrounding tissues (speci fi cation of
invasion).
Determination mass origin. •
US elastography, which bases on color pattern, is quite subjective and operator dependent.
The sensitivity and speci fi city of elastography is
limited by the number of factors, as follows
(Sencha et al. 2010a, b ) :
1. Objective
No general consent about elastographic •
appearance of normal breast and different
types of focal and diffuse pathology
Unstandardized elastographic option in dif-•
ferent manufacturers of ultrasound equipment
2. Subjective
Imperfect technique (absence of standard-•
ization of the compression force, some disputable principles of data estimation)
974.7 Ultrasound Elastography
Fig. 4.14 Breast carcinoma. Intense staining of the lesion. Grayscale US and elastography
98
4 Ultrasound Diagnosis of Breast Cancer
Fig. 4.14 (continued)
994.7 Ultrasound Elastography
Fig. 4.14 (continued)
100
4 Ultrasound Diagnosis of Breast Cancer
Fig. 4.14 (continued)