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A new Ultrasound modality Elastography

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A new Ultrasound modality Elastography Powered By Docstoc
					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.
         Static Elastography
     s
         e



Axial and lateral
 deformations
 after an axial
  constraint
                    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
SCORE 3
                                    SCORE 4




     DCIS                      Fibroadenoma


            Courtesy of Dr Anne Tardivon - Institut Curie - Paris
  IDC

           9x6 mm                       14x8 mm




Fibroadenoma



               6 x 5 mm                     5 x 3 mm
                      Courtesy of Dr Anne Tardivon - Institut Curie - Paris
IDC




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



                       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
  FLR

  40

  35
                                             cut-off = 4.3
  30                                         Specificity = 88.8%
                                             Sensitivity = 89.4%
  25                                         Exactitude = 89.0%
                                             Area under curve = 0.906
  20
  15
  10
                                          4.3
   5

               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 !!
Step 1: Volumetric force       Step 2: Ultra fast imaging Step 3: Image
creation using                 of the displacement        acquisition and
ultrasound beam focus          generated by ultrasounds processing
                                                                            Ultrasound beam


                                                                     US
                                                                   images



                       4% -1% Agar-
                       Gelatin Elastic
                         phantom
                                                                     1D Cross-correlation




           ~ 100 µs
                                           ~ 0.3 ms   Texp=20 ms                Uz(x,t)
                                         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
               µ (kPa)




                      IDC GRADE III

                µ (kPa)




              Fibrous Mastopathy
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   MRI   Elasticity module (kPa)
    impulsion compression
…MRE* is coming!!!
       WG 16 wake-up…

   But it is another story… ;-)

          *Magnetic Resonance Elastography

				
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posted:3/21/2012
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