医学影像系统原理7-超声课件.ppt

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,1,OUTLINES,1,.What is ultrasound?,2.History of the development of ultrasound imaging technique,3.2D ultrasound imaging,4.3D ultrasound imaging,5.3D ultrasound imaging applications,2What is SOUND?,Sound is a mechanical wave that we can hear,A mechanical wave can be described by:,Amplitude:,a,Wavelength:,Frequency:,f,Sound speed:,C,a,3,Sound Propagation Speed,Sound can be transmitted through any medium-gas,liquid,or solid.,Sound speed through the medium depends on the compressibility of the medium.The speeds of some materials are shown in the table below.,Sound speed in different materials(m/s),Aluminium,Bone,Liver,Kidney,Blood,Fat,Water,Lung,Air,6400,3500,1570,1560,1570,1460,1493,650,332,6,Principle of Ultrasound Imaging,7,Principle of Ultrasound Imaging,A pulse is propagated and its reflection is received,both by the transducer.,Key assumption:,-Sound waves have a nearly constant velocity of 1500 m/s in H,2,O.,-Sound wave velocity in H,2,O is similar to that in soft tissue.,Thus,echo time maps to depth.,8,Ultrasound Principle,9,Ultrasound Image(Embryo),10,Ultrasound:Resolution and Transmission Frequency,Tradeoff between resolution and attenuation-,higher frequency,shorter wavelength,higher attenuation,Power loss:,Typical Ultrasound Frequencies:,Deep Body 1.5 to 3.0 MHz,Superficial Structures 5.0 to 10.0 MHz,e.g.15 cm depth,2 MHz,60 dB round trip,Why not use a very strong pulse?,Ultrasound at high energy can be used to ablate(kill)tissue.,Cavitation(bubble formation),Temperature increase is limited to 1 C for safety.,11,Frequency Used in US Imaging,To have enough resolution for the observation of human organs,a frequency higher than 0.15 MHz,a wavelength less than 1.0cm,has to be used.,Also the frequency will determine the depth of imaging,the lower the frequency,the big the depth will be.,For abdominal imaging,a frequency between 1.0-3.0MHz has to be used.,For eye examination,a frequency as high as 20 MHz is used.,For IVUS imaging,40 MHz is used.12,History of the Development of Ultrasound(I),Karl Theodore Dussik,a neurologist/psychiatrist from The University of Vienna,Austria was regarded as the first physician to have employed ultrasound in medical diagnosis:locate brain tumor and the cerebral ventricles by measuring the transmission of ultrasound beam through the skull in 1942.,The earliest use of ultrasound is in therapy instead of diagnosis:,Destroy the basal ganglia in patients with Parkinsonism(William Fry,Russell Meyers),Treatment of patients with rheumatic arthritis(Jerome Gersten,1953),13,History of the Development of Ultrasound(II),Systematic investigations into using ultrasound as a diagnostic tool was made by George Ludwig,a physician at the Naval Research Institute in Bethseda,Maryland in the experiments on animal tissues using pulse-echo ultrasound.,“SONICS-techniques for the use of sound and ultrasound in engineering and science”(Theodore Hueter,Richard Bolt)book published in 1954.,14,History of the Development of Ultrasound(III),After the Korean war,John Julian Wild and John Reid built a linear hand-held B-mode instrument and become the first publication on intensity-modulated cross-section ultrasound imaging.,They also invented A-mode trans-vaginal and trans-rectal scanning transducers in 1955.,15,History of the Development of Ultrasound(IV),The“Pan scanner”,developed in 1957,by Douglass Howry,at the University of,Colorado,USA.,Problem:,Immerse totally or,partially in water,16,History of the Development of Ultrasound(V),In 1962,the first commercially available,hand-held articulated arm compound contact scanner was produced by engineers William Wright and Edward Meyerdink in USA.,The work of Howry and his team is the most important pioneering work in B-mode ultrasound imaging and contact scanning that we have today.,17,Pulse-echo Ranging,Applications:,Bats,Sonar system,Detects submarines,SONAR-Sound Navigation And Ranging.,18,2D Ultrasound Imaging,A-mode ultrasound,Horizontal axis is used to represent time while the vertical axis of the signal is to represent the amplitude of the signal.,19,2D Ultrasound Imaging,B-model ultrasound,To use the brightness of the screen to display the amplitude of the signal.The greater the amplitude,the greater the brightness of the spot.,20,2D Ultrasound Imaging,B-model ultrasound scan:,Sector scan,Linear scan,PPI(plan position indicator),Sector,Linear,PPI,21,2D Ultrasound Imaging,M-mode ultrasound,Also called Motion ultrasound,22,2D Ultrasound Imaging,Doppler ultrasound,23,Ultrasound Doppler Transducer,24,Ultrasound Doppler Principle,25,Ultrasound Doppler Image,26,2D Ultrasound Machine,27,Ultrasound Imaging,Why use ultrasound?,Low cost and portable system,Safest imaging modality,Fast,real-time imaging,Suitability for viewing the soft tissues and organs such as prostate,liver,heart,lung,28,Limitations of 2D Ultrasound Imaging,2D technique,must build the 3D image mentally,leads to inaccuracy&variability,leads to long procedures,Spatially flexible technique,difficulties in reproducing same view,difficulties in patient follow-up,difficulties in interventional procedures,29,3D Ultrasound:Side-fire scan,3D Reconstruction,3D Motorized,Scan(uniform),30,Rotational Mover(Side-Fire),31,Parallel Scanning,32,3D Carotid US:Freehand scan,33,Scanning mode in 3D ultrasound,Mechanical scanning,Parallel scanning,Rotational scanning,Fan scanning,Random scanning,free hand scanning,Real time 3D volume probe:,2D array transducer,volume probe,34,Parallel scanning,35,Side-fire Scanning,36,Random scanning with a localization system,37,Intravascular Ultrasound Imaging,38,IVUS Catheter Configuration,39,The Analysis of IVUS Image,40,Angiography VS IVUS,41,Disease can only be identified by IVUS,42,The IVUS Catheter Usage in USA and World,43,IVUS Applications,44,Measurement of Plaque,45,4D IVUS,46,3D US application:,fetus defect detection,Born infant,3D fetus image,47,48,3D Prostate Ultrasound Image by using transrectal transducer,49,Prostate Brachytherpy:Segmented prostate,50,Continuity Based 3D Prostate Segmentation in US Image,51,Needle Detection in 3D,52,Plaque segmentation:Carotid 3D US image,53,Volume of plaque,:964 mm,3,Plaque segmented from the 3D US Carotid image,54,x,n,z,p,x,p,z,n,y,n,3D US Guided Breast Biopsy Apparatus,55,Interface used in our RF Ablation system,56,3D Rotational Scanning Probe,57,3D US Imaging System based on Rotational Scanning,58,Reconstruction comparison of pork liver,：,Sideview,Traditional method,Our method59,Reconstruction comparison of pork liver,：,Topview,Traditional method,Our method,60,Water image acquired at three different times,61,Pin inserted into water at three different times,62,Pin segmented result,Before insertion,Detected pin,After insertion,63,3D Ultrasound Application:Prostate Brachytherapy,Prostate cancer is the second leading cause death of northern American men,The American Cancer Institute estimates 230,110 new case,29,900 dead in 2004.,Canadian Cancer Society estimates 20,100 new cases,4,200 dead in 2004.,Prostate cancer is curable at early stage.,64,Standard Treatments of Prostate Cancer,Watchful waiting:,Most patients request or need treatment.,Radical prostatecotomy:,Gold standard but with significant morbidity,such as incontinence and impotence.,External beam radiation,such as IMRT:,Long treatment time,kill the normal tissue.,Prostate brachytherapy:Short stay,safe for normal tissue,65,Brachytherapy Operation,66,Side-fire Scanned Transrectal Probe,67,Needle Tracking and Guidance Under 3D Ultrasound Imaging,Need to know where the needle is and where it will go.,Determine the tip position of the needle.,The processing has to be performed in real-time.,68,Oblique Needle Insertion,69,Why is,Needle Segmentation in US Images Difficult?,Ultrasound image speckle&shadows,Large 3D image,357,326,352,1 byte=40 MB,High accuracy required,Real-time processing (30 fps,or 33 ms per image),70,Motivation for Our 3D Needle Segmentation,Needle is,conspicuous,in a projected image.,Line object can be reconstructed from,two orthogonal projections,Approximate,needle insertion point and direction is known,71,Flowchart for our 3D Needle Segmentation,Steps 1&2,Step 3,Step 4,72,Step 1:Volume Rendering(Ray Casting),Cast rays through 3D image to image plane,Voxels,I,n-1,I,0,73,Step 1:Volume Rendering,Front-to-back ray tracing equations:,Gray level distribution of needle voxels:,Gaussian transfer functions:,Luminance,c,(,I,),Opacity,(,I,),74,Example of Volume Rendering,With rendering,Without rendering,Agar phantom,75,Step 2:Volume Cropping,Complex background,large volume,Estimate needle position/orientation from,a priori,knowledge:,Manual insertion,Motorized mechanical device,Localizing system(,e.g.,magnetic tracking),Simplifies background,reduces volume,Insertion point,Actual needle,Original volume,Cropped volume,Needle tip,Approximate needle,The cropped volume dimensions are,determined from,a priori,knowledge,of the approximate insertion point,the,approximate needle direction,P,and,the maximum inserted needle length,77,(c)Cropped volume of(a),(b)Rendered result of(a),(d)Rendered result of(c),Effect of Volume Cropping&Rendering,(a)Original turkey breast image,78,Step 3:2D Needle Segmentation,We used:,Global thresholding+flood-filling algorithm for objects with simple echogenicity,Real-Time Hough Transform(RTHT)for objects with complex echogenicity,79,Step 4:3D Needle Reconstruction,3D needle reconstruction is based on two orthogonal projections,Both projection directions are chosen to be orthogonal to the approximate needle direction,Each projection is orthographic,i.e.,the cast rays are parallel,80,3D NEEDLE RECONSTRUCTION,Actual needle,Approximate needle,Y,X,Z,R,Q,P,Two coordinate systems:,(X,Y,Z):3D image,(P,Q,R):projection,P,P,81,3D Needle Reconstruction,P,Q,R,2D needle direction,P,82,3D Needle Reconstruction Demo,83,Patient Prostate Needle Segmentation,84,3D Needle Tracking in Agar,85,Prostate Segmentation in 3D Ultrasound Images,Motivation:,The prostate boundary and volume are needed to assign the patient to the appropriate therapy.,The volume of the prostate is required to determine the dosimetry distribution and radioactive seed locations.,86,Our Approach:Sliced Based3D Prostate Segmentation,Step 1,Step 3,Step 4,yes,no,Step 2,87,Step 1:3D Image Re-slicing,Parallel re-slicing:,Problem:At the ends,only a small portion of the prostate is visible.,Rotational re-slicing:,The prostate shapes and sizes in the re-sliced images are similar.,88,3D Image Re-slicing,(a)Parallel re-slicing,(b)Rotational re-slicing,89,Step 2:Cardinal-Spline Initialization Model,Cardinal-spline:,Why we chose the Cardinal-spline?,No,control points are needed,Easy to determine the spline coefficients,Passing through the initial points exactly,and,The number of initial points can be varied.,90,Step 3:Contour Deformation,Refine the boundary in the initial 2D slice using DDC method(,Lobregt,et al,A Discrete Dynamic Contour Model,IEEE Trans.MI,14,12-24,1995,),Extend 2D segmentation to 3D:,Propagate the prostate contour in initial slice to an adjacent slice in both directions.,Refine the contours and repeat contour propagation until all slices are segmented.,91,Step 4:3D Prostate Reconstruction,Sliced based reconstruction:,All 2D contours are represented by vertices,3D reconstruction using triangular mesh,Prostate volume calculation:,where the prostate is composed of,m,faces,F,j,;,F,j,has area vector ,at a representative vertex,.,92,3D Prostate Segmentation Demo,93,Seed Segmentation in 3D Ultrasound Images,Motivation:,Calculate the dose distribution during or after the seed implantation,Challenges:,tiny dimension:4.5mm,long cylinder with a diameter of 0.8mm.,Low contrast,Large number:70-1,40,94,3D Prostate Ultrasound Image with Seeds,95,Thresholding Based on Tri-bar Projection Model,Pre-known information:,Shape of seed,Approximate orientation of the seeds,Tri-bar projection model,:,Project along the bar,Calculate the average,and the standard deviation,in the projected image,X axis Z axis Y,axis,Y,Z,X,96,3D Agar-seed Ultrasound Image,3D image after rendering,Tri-bar segmentation,97,Seed Segmentation Demo,98,Patient Seed US Image Thresholding,Original projection,After thresholding,99,3D Ultrasound Application:Breast Biopsy,Agar phantom,Patient breast biopsy,100,Thank you!,