**5. Practical information for the use of mammary elastography**

### **5.1 Colour map code**

The Hitachi company, a pioneer of strain elastography (SE) have expressed the modifications in the elasticity of mammary tissues through a colorimetric chart known as the 'Tsukuba score'. Reds and yellows correspond to very supple tissues, green has a slightly higher elasticity score and blue a much increased gradient in elasticity; last of all, a deep blue zone surrounded with a pale blue halo is the sign of a lesion which is very likely to be malignant [4].

**Figure 10.** *SWE multi plane benign cyst = 20 kPa.*

Another pioneer in Shear Wave Elastography (SWE), the Supersonic image group have chosen the opposite colour coding, red for a hard, probably malignant lesion, blue for low score, supple elasticity which is therefore benign. This latter, more 'European' colorimetric representation (red = danger) can very easily be reversed electronically through a simple modification in the software, and this applies to both SE and SWE techniques. This colour inversion is not a major difficulty for the user who, most of the time, does not use the two techniques simultaneously; he must simply make sure he follows some basic, standard rules (e.g. no hyper-pressure with the probe which must be strictly perpendicular to the skin, etc.) which he will have had fully described in the course of his training.

The use of a dual mode (mode B image joined to the elastography image in colour) enables a perfect synchronisation in the analysis of the lesion, either in SE or in SWE. The colour mode indicates very rapidly the suspicious (or non suspicious) character of an anomaly detected through echography [11].

As the appreciation of colours may vary from one user to another, the builders of these machines have turned towards more precise and measurable quantitative data.

The 'fat to lesion ratio' makes it possible to measure the variations in elasticity between the hardest tissues and the supplest fatty tissue with great precision.

The use of ROI (region of interest) or of the Q Box has to be well handled: one ROI/Q Box is positioned on the suspicious coloured lesion, the other is placed on the supplest possible tissue, generally the subcutaneous fatty tissue.

**Figure 11.** *Ultrafast doppler + SWE of a carcinoma =160 kPa.*

**Figure 12.** *Srain elastography of a non-evident 2D lesion with a F/L ratio = 15.21.*

In SE, the ratio is graded from 1 to 10 (or more) with a 'cut off point' between 3 and 4 (lesion likely to be benign, or likely to be suspicious). In SWE the mean and standard deviations are provided in kPa (KiloPascal), ratio and averages derive from the quantitative measurements.

Evans has determined the threshold of 50 kPa for Birads 3 or below lesions which are benign as a rule. According to him, scores over 50/60 kPa correspond to Birads 4/5 lesions which are to be biopsied, scores higher than 100 kPa or more are a certainty of malignancy.

The most interesting case is that of the lesions graded Birads 3, when one keeps in mind that 2% in this category correspond to malignant lesions and that, furthermore, there exist 'soft' cancers (mucoid, colloid, in situ or no mass cancers). Mucinous cancers considered as 'soft' tumours reach high scores in SWE (from 95 to over 200 kPa). Quite obviously, one must take into account complementary factors such as the age of the patient, the size of the breast, the distance between the skin and the lesion, the fibrous or involuted character of the breast, all of which take their share in the Birads 3/4 scoring.

#### **5.2 Regrading of these 3/4 Birads lesions = upgrade/downgrade:**

Elastography allows to reduce the number of unnecessary biopsies through a better specificity and PPV (Positive Predictive Value). It guides the decision not to biopsy a Birads 4a lesion with a negative reassuring elastography and to suggest instead an echography follow-up 6 months later, or on the contrary, to biopsy a Birads 3 lesion with a suspicious elastography response. Such a way of dealing was presented by the Korean Society of Ultrasound (KSUM) in 2014 [12].

In the case of a negative Birads 3 lesion, the follow-up will be the same as for a Birads 2 lesion.

a.Negative Birads 4a = Birads 3

b.Positive Birads3 = Biopsy

c.Negative Birads 4a = Birads 2

#### **5.3 Follow-up of treatment efficiency in a proven cancer**

If mode B echography alone underestimates the size of the cancer, with the contribution of elastography, it produces a perfect assessment of the histological size of the lesion.

The prediction of the response to the neoadjuvant chemotherapy treatment has been studied by different groups who confirm that there is a relationship between the score of pre-operative elasticity and the response to the treatment.

The maximum score in elasticity of the tumour is related to its histological severity:

Invasive cancer elasticity score = between 140 and 180 kPa.

Ductal cancer in situ = between 70 and 180 kPa.

Benign lesion medium elasticity score = 45 kPa.

Lipoma = 15 kPa.

The 180 kPa is predictive of nodular metastasis. If information on the size of the tumour, the lymph node and vascular invasion and the histological grade of the cancer is added, capital information is obtained on the prognosis of the evolution of the cancer.

Modification of stiffness (up or down) seems to be a very relevant parameter to access treatment efficacy.

#### **5.4 Assessment of echo graphically revealed micro-calcifications**

Two conditions are to be faced: either micro-calcifications with an obvious focal lesion, or micro-calcifications without echo graphically visible lesions. A very small number only of these micro-calcifications can be detected through mode B echography. They are the indirect signs of an intra-ductal or intra-lobular disruption. In comparison to mammography, echography offers the added bonus to visualise directly the epithelial structure of the epithelial proliferation or hyperplasia type. Their development may correspond to a physiological character, an inflammation or a tumoral process. And it is only the bringing together of mode B echography, ultra fast Doppler, elastography and possibly 3D analysis, that allows to distinguish a probably benign lesion from a well-defined or a diffuse lesion, but it remains difficult, if not impossible, to distinguish between the successive stages in epithelial modifications: physiologic proliferation, florid hyperplasia, border line or cancer in situ in its earliest stages. The role of echography is to allow a selection of the patients at risks (with a thickening of epithelial structures) for whom follow-ups or further investigations must be considered.

#### **5.5 Role of elastography in mammary pathology**

The diagnosis of breast lesions and the way in which they are dealt with has progressed dramatically thanks to the use of new technologies in breast imaging. Among these techniques, ultrasound elastography has become an essential, unavoidable tool. It combines rapidity of execution, diagnostic reliability and remarkable reproducibility. It allows to put forward dubious cases and patients at risk who have to have regular check-ups. And it also allows a reduction in the high number of ultrasound false positives, a regular follow-up of probably benign lesions and a monitoring of the efficiency of neoadjuvant treatments [13].

At this stage, however, the study of lymph nodes invasion remains difficult and the understanding of the relationship between the maximum elasticity score of a tumour and its immuno-histological phenotype is not conclusive. Let us hope that future progress in echography will soon enable us to fill in these gaps.

#### **6. Conclusion**

The coupling of 3D Breast Echography + Angio-plus-Ultra-fast Colour Doppler with elastography has allowed significant improvements in evidencing the location of the breast lesions, their qualification and the management of pre-operative neoadjuvant chemotherapy. A better collaboration with the team who is in charge of the patient (surgeon, oncologist, doctor, radiotherapist, nurse etc.…) can thus be achieved to the patient's greatest benefit.

In qualifying the grade of the tumour, the presence of metastases in the lymph nodes and in offering a prognosis linked to the aggressiveness of the tumour, the radiologist allows a significant saving of time for the therapeutic approach of the patient and a better targeted, more personalised therapy.

#### *Breast Elastography DOI: http://dx.doi.org/10.5772/intechopen.102445*

The evaluation of therapeutic care strategies is better adapted than a standard protocol. There are close relations between the modification of elasticity, the size of the tumour, the metastatic invasion of the lymph nodes, the more or less aggressive nature of the cancer and the choice of the suitable neoadjuvant chemotherapy.

The decrease in recall rate as well as in unnecessary punctures (40–50%) amounts to serious cost effectiveness.

Inter or intra-operator perfect reproducibility, fair possibility to repeat the examinations in over 85% of the cases and lastly outstanding sensitivity and specificity explain why the echography-elastography coupling has achieved a significant beneficial impact on breast imaging. Future developments are still to improve the diagnosis and follow up of breast cancer [10, 14–62].
