A new Ultrasound modality: US Elastography Joel Chabriais

Why Elastography? In old Egypt, 5 000 years ago, physicians examined the different parts of the body to evaluate elasticity, they knew that a hard mass in an organ is pathologic. In Greek ancient age, for Hippocratic medicine, palpating was an essential time of physical examination. In 21st century, imaging take preeminent place in medicine and Elastography could be considered as an « imaging palpation »…

What is Elastography? Elastography is an imaging technique to measure the stiffness of tissues. Images are acquired before and after soft compression of tissues and the deformation is evaluated. Initially elastography used manual compression and was only qualitative, now some methods appears to apply a non operator dependant compression.

Elastography and US Elastography was developed first in the US field. Three step approach: Organs mechanically stressed by either external or internal forces. Measurement of tissues movement induced. Qualitative or quantitative evaluation of tissue elastic properties from the measured displacement of tissues.

Several Approaches Manual compression by operator using the transducer (static elastography). Organ compression by heartbeat or vascular pulsations. Push pulse waves compression. Supersonic shear waves.

Axial and lateral deformations after an axial constraint Static Elastography s e Axial and lateral deformations after an axial constraint EN HAUT HITACHI EN BAS SIEMENS Courtesy of Dr Anne Tardivon - Institut Curie - Paris

Ueno Staging 1 = Lesion distortion similar than in surrounding tissues 2 = Heterogeneous distortion versus surrounding tissues 3 = Lesion center distort less than surrounding tissues 4 = Whole the lesion distort less than surrounding tissues 5 = Whole the lesion and adjacent tissues distort less than surrounding tissues

Fibroadenoma DCIS SCORE 3 SCORE 4 HITACHI Fibroadenoma DCIS Courtesy of Dr Anne Tardivon - Institut Curie - Paris

IDC Fibroadenoma 14x8 mm 9x6 mm 6 x 5 mm 5 x 3 mm IMAGES SIEMENS (provenance IGR, corinne Balleyguier) 6 x 5 mm 5 x 3 mm Courtesy of Dr Anne Tardivon - Institut Curie - Paris 9

IDC Courtesy of Dr Anne Tardivon - Institut Curie - Paris SIEMENS NORI/ BLANC CODAGE COULEUR inverse d’HITACHI dur = rouge Courtesy of Dr Anne Tardivon - Institut Curie - Paris

Static Elastography Development: Quantitative Analysis 1 1.5 2.3 3.7 This measurement quantify elasticity correlation between two regions. The FLR is independent of the compression movement. The 1st region define the lesion and the 2d is the reference (fat). a b c d Mean Elasto Fat FLR= Mean Elasto Lesion Courtesy of Dr Anne Tardivon - Institut Curie - Paris

FLR=1.2 FLR=8.9 Tsukuba University Hospital, JAPAN Courtesy of Dr Anne Tardivon - Institut Curie - Paris

155 lesions (108 Benign and 47 Malign) / 140 Patients 20 25 30 35 40 15 10 4.3 cut-off = 4.3 Specificity = 88.8% Sensitivity = 89.4% Exactitude = 89.0% Area under curve = 0.906 FLR BENIGN MALIGN (Mean: 2.95) (Mean: 11.61) Courtesy of Dr Anne Tardivon - Institut Curie - Paris

Elastography: improvements Compression/Decompression Movements Displacement speed measurement Integral -> Elasticity Elasto Q Mode Information at decompression Automatic selection of the best cycle ROI on fat and lesion Quantification Courtesy of Dr Anne Tardivon - Institut Curie - Paris

Courtesy of Dr Anne Tardivon - Institut Curie - Paris

SuperSonic Elastography Acquisition time < 30 ms !! 4% -1% Agar-Gelatin Elastic phantom ~ 100 µs Step 1: Volumetric force creation using ultrasound beam focus 1D Cross-correlation Step 3: Image acquisition and processing Ultrasound beam US images Uz(x,t) Step 2: Ultra fast imaging of the displacement generated by ultrasounds Texp=20 ms ~ 0.3 ms Courtesy of Dr Anne Tardivon - Institut Curie - Paris

Supersonic Elastography Significant difference benign versus malign: Cancers: E = 170.1 ± 41.6 kPa Benign lesions: E = 53.5 ± 19.8 kPa n= 36 Courtesy of Dr Anne Tardivon - Institut Curie - Paris

IDC GRADE III Fibrous Mastopathy µ (kPa) µ (kPa) Courtesy of Dr Anne Tardivon - Institut Curie - Paris

Fields of Application in Medicine Breast Thyroid Liver Prostate …

Elastography in DICOM: Why? Now, several vendors are coming on the market: Until 2008: 1 vendor had products for sale. 2008: 3 vendors. 2009: several announcements  6 vendors or more. … probably every US vendor at short term. At this time, only secondary capture or US objects. All specific information to elastography are lost.

Elastography in DICOM: Why? More and more clinical applications. New BI-RADS edition, planned for 2010, will take into account US elastography for breast imaging. Users would like to be able to store elastography information in their PACS: Additional attributes in US objects? New objects? Some pathology needs elastography follow-up:  Probably DICOM SR templates needed

Elastography in DICOM: Who is Concerned? Elastography is US  WG 12 Elastography for Breast imaging  WG 15 Elastography needs DICOM SR templates  WG 8 Other?

Elastography in DICOM: How To Go Further? A motion to ask the concerned WG to investigate the domain to determine if further works needed? Report to DICOM Standards Committee? …

US Elastography And after?

Clinical device with mechanical impulsion compression MRI Elasticity module (kPa)

But it is another story… ;-) …MRE* is coming!!! WG 16 wake-up… But it is another story… ;-) *Magnetic Resonance Elastography