Elastography: An Additional Tool for Characterisation of Breast Lesions

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Elastography: An additional tool for characterisation ofbreast lesions

Poster No.: C-0427

Congress: ECR 2010

Type: Educational Exhibit

Topic: Breast

Authors: A. M. Makudamudi, A. Kanakarajan, B. Raghavan, J. Govindaraj;Chennai/IN

Keywords: elastography, BI-RADS, spatial resolution

DOI: 10.1594/ecr2010/C-0427

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Learning objectives

Elastography New imaging method which provides very high contrast between massesand host tissue, by estimating the measure of visco-elastic properties of tissues.Types: Ultrasound Elastography MR Elastography

Slide 3

•Elasticity Imaging looks at mechanical properties -Show relative tissue stiffness orhardness -Different information than B-mode which shows backscatter information-Provides further insight into potential pathology •Helps to differentiate hard fromsoft lesions. •Differentiates cystic from solid lesions. Advantages of ultrasound inElastography: real-time imaging capabilities, very high resolution in motion estimation(~1mm), simplicity, non-invasiveness, and relative low cost.

Background

PRINCIPLE Slide 5 Palpation creates & senses strain. Elasticity is the physicalproperty of a material when it deforms under stress (e.g. external forces), but returnsto its original shape when the stress is removed. Stress is the force causing thedeformation. Strain is the amount of deformation produced by the stress. Young'smodulus (E) describes tensile elasticity as the tendency of an object to deform alongthe axis of compression It is a measure of the stiffness of an elastic material. Thereforeeasily deformable substances will have low value of E and substances which aredifficult to deform will have high values Ultrasound Elastography Slide 6 •Thestrain is estimated from minute differences between two B-mode images, duringcompression either by the transmitted pulsation in cardiac cycle or by minimal activeprobe compression. •The differences are in the order of 0.1 to 0.2 mm •Strain valuesare then displayed as an image. •Image is displayed using either different shades ofgray or using different colours to represent the varying magnitude of strain values.•Elastogram is superimposed on B-mode image. •Stiffer lesions appear darker & larger.Technique of Image Acquisition •Probe and lesion perpendicular to gravity •Motionis provided by the patient's breathing and heart beat •If insufficient, slow minimalcompression with the probe is applied Fig 5 Methods of computation oftissue elasticity [1] 1.Spatial correlation method 2.Phase-shift tracking method3.Combined autocorrelation method Spatial correlation method [1] •Uses anordinary two-dimensional pattern matching algorithm •Searches for the position thatmaximizes the cross correlation between ROI's selected from two images obtainedbefore and after deformation. •This method can be used to demonstrate displacementin two dimensions - longitudinal and lateral. Disadvantage : Processing time is

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lengthy for real-time assessment. COLOR MAPPING -ELASTICITY SCORE (Spatialcorrelation method) Fig 1Elasticity Score Fig 2Slide 12 Fig 3 CYST - variable appearances(Spatial correlation method) [2]

• 3-layered pattern with both bright and dark regions• darker (stiffer) area with a brighter (softer) center, "bull's eye"• a uniformly dark area• Ill-defined margins• Smaller or same size

Fig 4 Phase-shift tracking method [1] Based on autocorrelation method- principleof color Doppler US. This method can be used to rapidly and precisely determinelongitudinal tissue motion because of phase-domain processing. Disadvantage:•Errors related to aliasing - fails when used to measure large displacements. •Poorlycompensates for movement in the lateral direction - disadvantage for freehandcompression. Slide 15 •Slightly different technique is used in acquisition & computation•B-mode image is obtained & ROI is placed within it •Lesion is actively compressed &released for 3-5 times and frozen. •Elastography is computed by pressing ElastographyQ button. •Elasticity value obtained from the strain graph Fig 6 Slide 16 Fig 7 Slide 17Fig 8

Images for this section:

Fig. 1: Color mapping- Elasticity score (Spatial correlation method)

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Fig. 2: Elasticity score

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Fig. 3: Elasticity score

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Fig. 4: Cyst-variable appearances (Spatial correlation method)

Fig. 5: Technique of Image acquisition

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Fig. 6: Phase shift tracking method

Fig. 7: Elastographic computation in Phase tracking method

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Fig. 8: Phase tracking method- graphical display

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Imaging findings OR Procedure details

Cystic lesions Fig 1 Cystic & complex cystic lesions Fig 2 Cystic & complexcystic lesions Fig 3 Discordant Elastogram in benign lesions Fig 4 Solid roundedlesions Fig 5 Solid rounded lesions Fig 6 Irregular small lesions Fig 7 Slide 25 Fig8 Slide 26 Fig 9

Images for this section:

Fig. 1: Cystic lesions

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Fig. 2: Cystic & complex cystic lesions

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Fig. 3: Cystic & complex cystic lesions

Fig. 4: Discordant Elastogram in benign lesions

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Fig. 5: Solid rounded lesions

Fig. 6: Solid rounded lesions

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Fig. 7: Irregular small lesions

Fig. 8: Bilateral & Multifocal malignancy

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Fig. 9: Elastography in microcalcifications

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Conclusion

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Statistics Slide 27Total no. of lesions studied- 100 (Spatial correlation method) Kappa agreement showselastography correlates better with pathology when compared to USG. Specificityof elastography is better than ultrasound and correlates with literature. [3] Fig 1,Fig 2, Fig 3 •Elastography provides additional information not otherwise available.•Complementary to B-mode USG/ mammography. •Can reduce the indications forunnecessary biopsies & interventions in benign lesions like complex cysts & in someinstances MRI. •Can help in guiding the appropriate area for biopsy (hard area)•Quantitative analysis can be performed. •Increases confidence level. •Cost effective.

Images for this section:

Fig. 1: Statistics

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Fig. 2: Statistics- Kappa agreement

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Fig. 3: Statistics- Sensitivity & Specificity

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Personal Information

Presenters:

Dr.Anugayathri Makudamudi

Resident in Radiology

Dr.Bagyam Raghavan

Senior Consultant

docbagyam@gmail.com

Department of Radiology & Imaging Sciences,

Apollo Speciality Hospital,

Chennai, India.

Acknowledgements:

Dr.S.Suresh,

Mediscan Systems,

Chennai, India.

References

References < 1.Ako Itoh, Ei Ueno, Eriko Tohno, Hiroshi Kamma, et al. Breast Disease:Clinical Application of US Elastography for Diagnosis. Radiology: May 2006; 239:341-350. 2.Tardivon A, et al. Elastosonography ofthe breast: prospective study of122 lesions. J Radiol 2007;88:657-662. 3.Thomas A, Fischer T, Frey H, Ohlinger,et al. Real-time elastography- an advanced method of ultrasound: first results in108 patients with breast lesions. Ultrasound Obstet Gynecol 2006; 28: 335-340.4.Garra BS, Cespedes EI, Ophir J, et al. Elastography of breast lesions: initial clinicalresults. Radiology 1997;202:79-86. 5.Shiina T, Nitta N, Ueno E, Bamber JC. Realtime tissue elasticity imaging using the combined autocorrelation method. J Med

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Ultrason 2002;29:119-128. 6.ZhiH, et al. Comparison of ultrasound Elastography,mammography, and sonography in the diagnosis of solid breast lesions. J UìtrasoundMed 2007; 26:807-815.

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