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3D Breast Ultrasound

Even though 3D Ultrasonography is not new in fields like cardiology or obstetrics, it is comparatively new in the field of breast imaging. The ordinary 2D Breast ultrasonography is thought to be troublesome on the grounds that it is hard to to tell apart between normal or benign fibrocystic lesions from early pathologic lesions. Currently with the improvement and accessibility of 3d Ultrasonography , identification of lesions from benign changes has become easier. Some studies have demonstrated that 3D ultrasonography is a better device for screening young patients and patients with dense breasts. 3D breast ultrasound can be additionally utilized as an adjunct to plain film/ computerized mammography or digital breast tomosysnthesis (DBT).

 ABUS Patient


In spite of mammography's demonstrated adequacy, there is an increasing enthusiasm for using more up to date advances in breast lesion diagnosis, particularly in women with dense breast tissue and those at high danger of breast disease. One impediment of mammography is obscuring of non calcified tumors by other ordinary thick breast tissue. It can be overcome by utilizing breast ultrasound. Breast ultrasound is currently acknowledged as a standard analytic system for women with clinically or radiologically suspicious breast lesions and has turned into a noteworthy supplement to mammography in patients with thick breasts. It's currently a significant mode of imaging for clinically diagnosing breast malignancy. Breast Ultrasound is employed for distinguishing palpable breast lesions and suspicious discoveries on mammography. The significant strength of breast ultrasound is the differentiation between cystic and solid lesions with an exactness of almost 100% and hence is routinely utilized for this purpose.

Together with mammography, ultrasound is frequently employed to portray solid masses as benign or malignant. Simplicity of use and constant real time imaging ability make breast ultrasound a technique of choice for directing breast biopsies and different interventional systems.

Regular advances in transducer design, hardware, PCs, and signal processing have enhanced the standard of ultrasound pictures. Breast ultrasound is employed in several forms. B-mode is the most common style of imaging for the breast, albeit compound imaging and harmonic imaging are being progressively utilised to better picturise breast lesions and to cut back image artifacts. The availability of definite vocabulary/definitions of solid mass features, has enhanced the analytic performance of breast ultrasound.

Even though 3D Ultrasonography is not new in fields like cardiology or obstetrics, it is comparatively new in the field of breast imaging. The ordinary 2D Breast ultrasonography is thought to be troublesome on the grounds that it is hard to to tell apart between normal or benign fibrocystic lesions from early pathologic lesions. Currently with the improvement and accessibility of 3d Ultrasonography , identification of lesions from benign changes has become easier. Some studies have demonstrated that 3D ultrasonography is a better device for screening young patients and patients with dense breasts .3D breast ultrasound can be additionally utilized as an adjunct to plain film/ computerized mammography or digital breast tomosysnthesis (DBT).

3D breast ultrasound is performed with one craniocaudal sweep from the supraclavicular region to the inframammary fold with a 15cm transducer device.3D breast ultrasound doesn't give an entire breast examination in light of the fact that the axillary tail and lower axilla are not pictured completely. When it is utilized as an adjunct to mammography each one of those regions are covered.

Advantages of 3D breast ultrasonography over 2d ultrasonography

Screening utilizing a conventional hand held transducer is operator dependent and therefore it is conceivable that a few zones of the breast may be missed during examination. In traditional two-dimensional (2D) ultrasound, a breast lesion must be quickly analysed amid the ultrasound examination. A shortcoming of this imaging strategy is the non plausibility of a second assessment on hard-duplicate printouts because of the absence of standardisation of sonographic criteria.

Three-dimensional (3D) ultrasound offers new points of interest in the field of breast ultrasound. Its significant utility is the generation of numerous sectional planes of a lesion and in addition the computation of volume amid a 3D ultrasound examination. Because of its advanced features, every sectional plane of the examined volume can be pictured, in this manner it prevents the operator dependent limitations and non-standardised documentation. Likewise, the created coronal plane parallel to the skin, which can't be produced by ordinary ultrasound, offers new diagnostic data and conceivably enhanced portrayal of breast lesions. Meyberg – Solomayer and etal researched on 65 patients with breast lesions whether 3d ultrasonography has significant points of interest more than 2d ultrasonography in dignosis of breast lesions. They found that 3d sonograpraphy when utilized as an adjunct to 2D ultrasonography gives a more exact picture of the infiltative zone. It was found that coronal plane is beneficial when the infiltrative zone is indistinct. Moreover the surface mode was found to be useful for imaging complex structures like multinodular fibroadenoma.

Ultrasound characteristics on 3D ultrasound vary very much from those on 2D ultrasound. On the other hand, the analytic exactness of both strategies is practically very similar. 3D ultrasound when utilized as an adjunct to other breast imaging methods gives more confidence in diagnosing of breast lesions in light of the fact that it gives better breast mass characterisation

Planes obtained in Breast ultrasonography

3D Ultrasound scan produces images in the sagittal, transverse and coronal planes. 2D Ultrasound produces images in only sagittal and transverse planes. The sagittal and transverse planar sections of the 3D scan are similar to the sagittal and transverse planes achievable by conventional 2D ultrasound. The sectional images in the transverse, saggital and coronal planes in 3d breast ultrasonography can be rotated in any direction and they can be visualised simultaneously on the screen for better analysis of breast lesions.

Criteria used to analize lesions in Breast Ultrasound
A standardised set of uniform criteria is used for analysing breast lesions through ultrasonography. Some definitions of the terms used for analysis of breast ultrasound are given in the table below. If any of the following features differ in different planes it is taken as malignancy. (For example if irregular in the transverse plane and uniform in the sagittal plane it is considered as malignancy).

Parameter
Definition
Shape
 Irregular (#)
Not oval or round
 Oval (*)
Oval in shape, maximum. three smooth lobulations
 Round (*)
Round, Spherical
Orientation
 Vertical (#)
Axis is vertical to skin, more tall than wide.
 Indifferent (#)
In spherical lesions, when the posterior margin is not discernable because of strong shadowing
 Parallel (*)
Axis is parallel to skin; more wide than tall, horizontal
Echogenicity
 
 hypoechogenic (#)
remarkably lower echogenicity compared to fatty tissue
 Isoechogenic (*)
Equal or slightly lower echogenicity compared to fatty tissue
Hyperechogenic (*)
Higher echogenicity compared to fatty tissue, for e.g. fibroglandular tissue
 
Echo pattern
 Complex (#)
Zones with noticeably different echogenicity within the mass
 Homogeneous (*)
Almost similar echogenicity throughout the mass
 
Hyperechogenic spots
 
 Present (#)
Punctuated widely with hyperechogenic foci inside a hypoechogenic halo
 Absent (*)
Not punctuated widely with hyperechogenic foci
 
 
 
Margin contour
 Irregular/spiculated (#)
Uneven margins(e.g. angular margins, spiculate, microlobulation, , branch patterns)
 Smooth/lobulated (*)
Even margin without irregularities or not more than five undulations
 
Margin
 Indistinct (#)
Blurry , Not circumscribed, exact location of the margin is difficult to demarcate
 Circumscribed (*)
Clear demarcation between surrounding tissue and tumor
 
Lesion boundary
 Hyperechogenic halo (#)
Irregular,blurred, hyperechogenic rim surrounding the lesion
 None (*)
No echogenic halo or thin capsule
 Thin capsule (*)
clear thin hyperechogenic rim at the margin of the lesion
 
Posterior acoustic features
 Shadowing (#)
posterior echoes reduced , also combined features ( enhancement and shadowing or indifferent posterior echoes and shadowing )
 Enhancement (*)
enhanced posterior echoes
 Indifferent (*)
No enhancement or shadowing
Surrounding tissue
 Architectural distortion (#)
Disturbance of the anatomical structures, stoppage of glandular tissue and cooper ligaments.
 Compression (*)
anatomical structures are maintained , cooper ligaments are displaced
 Indistinct (*)
Difficult to separate if there is a structural compression or a distortion
 
 
Definitions of 3D ultrasound features studied in the "coronal" plane of the 3D ultrasound
 
Retraction
 Present (#)
Fibrous Hyperechogenic ligaments of the breast running concentrically to the growth
Absent (*)
Encompassing tissue not disturbed in its orientation or compressed and relocated
Indistinct (*)
uncertain whether the encompassing tissue is retracted or not altered by the lesion
Margin contour
Definition identical to the criteria utilized as a part of conventional ultrasound imaging
Margin
Definition identical to the criteria utilized as a part of conventional ultrasound imaging

Basic methodology of the ultrasound analysis of breast lesions

Malignant tumours appear on breast ultrasound as solid masses which have irregular margins. The internal echoes from them are weak and show non uniform distribution and also there will be more acoustic attenuation. .Malignant tumours also cause thickening or retraction of coopers ligaments and hence change the overall breast architechture. Benign growths appear as solid masses with smooth margins and well defined edges. The internal echoes from benign tumours are weak, uniformly distributed with very less or moderate accoustic attenuation. Also the normal architechture of breast is not altered in benign breast tumours because, coopers ligaments are not affected. Breast ultrasound gives information about whether a tumour is likely to be benign or malignant based on character of the breast masses. If confirmation is needed biopsy can be done.

Main use of ultrasound is for diffrentiation between cystic masses and solid masses. Breast tumours are classified as cystic, benign, malignant etc based on shape and margins of masses, features of internl echoes, and the changes in the sound returning to the transducer after passing through the tumours. General features for differentiation are as follows. The features of benign and malignant tumours can overlap and some benign features can be found in some malignant tumours and some malignant features can be found in some benign tumours . Cysts do not show internal echoes even if the gain is high. If debris is present in the cysts it produces reflections , reducing the confirmation of diagnosis .To confirm an aspiration is indicated. Cysts are anechoic and increase the transmission of sound through the tumour. Fibrosis if present around the cysts may dissipate and attenuate the sound. Then an aspiration is required to confirm the diagnosis. Solid masses that have a uniform composition can also cause acoustic enhancement posteriorly if sound passes through them with less dissipation and attenuation than the surrounding tissues. If the lesions are oval or round, both solid masses and cysts can produce shadows at the edges due to refraction .Generally, Masses which have ovoid shape, uniform internal echoes and masses which increase the sound transmission are benign. However some malignant tumours can also have these features. Malignant masses produce attenuation of the sound as it passes through the tumours . However some benign lesions like fibrosis fibroadenomas can produce attenuation of the sound passing through them. If shadowing is complete or heterogenious, it is a lesion of concern.

Limitations of 3D breast ultrasound

Breast ultrasound is the best method for guiding breast biopsies and other procedures , because it is easy to use and it produces continuous real time imaging. Even though 3D breast ultrasound gives more accuracy in detection of breast cancer than conventional ultrasound it has some limitations over conventional ultrasound. The limitations of 3d breast ultrasonography are, First, the machine setup is larger than a conventional ultrasonography equipment. Second , more data input is needed from operator and third, unlike the conventional ultrasonography where images appear instantaneously, different algorithms take different duration of time for the images to appear on screen. With some algorithms , the images appear instantaneously while other algorithms take more time . Finally it is very difficult for an inexperienced operator to decide on the algorithm or the perspective from which the image should be analyzed.

Future of breast ultrasonography

Continuous research is being done to get simultaneously other details like tumour blood flow, produce images of vascularity of tumours using doppler ultrasound and to develop a variety of contrast agents required for other breast imaging modalities that can be added to breast ultrasound.Other areas in which research is being done are developing better software and hardware . Research and Development of these techniques can help produce breast ultrasound equipment which can extract more physiological and mechanical data than conventional ultraound machines for thorough analysis of breast lesions. This can improve, in future the role of breast ultrasound in differentiation between benign and malignant breast lesions and detection of breast cancer. Improving the predictive power of breast ultrasound in differentiating benign tumours from malignant tumours is also one the focus themes of continuous breast ultrasound research. Also, currently there are many problems with registration and co registration of breast ultrasound images with other imaging modalities like digital breast tomosynthesis (DBT) . Hence it is also one of the important areas of current breast ultrasound research.

Read more about this and other subjects in our 15 Category A Credit X-Ray CE Course "Mammography Review"

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