Medical Imaging Seeinggg Through the Human Body

Source: uhrad.com. Medical Imaging Seeinggg Through the Human Body

Elsa Ange lin i Department TSI ENST

1 It all started in 1845 with the first X-ray image

Roentgen’s wife Von Kolliker 2 History of Medical Imaging

• 1845: Discovery of X-ray by Wilhelm Conrad Röntgen, german physicist. • 1972: First scanner set up by Allan Mc Cornack et Godfrey N. Hounsfield, Nobel prize in 1979 for this work. X Ray

• 1915: Ultrasound propagation principles for SONAR (SOund NAvigation Ranging). • 1955: First echography by Inge Edler (1911-2001), swedish cardiologist. US

• 1945: Discovery of nuclear resonance under a magnetic field by Edward Purcell and Felix Bloch, both nobel prize winners in 1952. • 1973: First MRI image on an animal by the american chemist Paul Lauterbur. P. MRI Lauterbur and P. Mansfield won the Nobel Prize for Physiology or Medicine in 2003 for the development of MRI. • 1980: Spectroscopy by magnetic resonance.

• 1934: Discovery of natural radioactivity by Henri Becquerel, Pierre et Marie Curie.

ear Discoveryyyy of artificial radioactivity by Irène et Frédéric Joliot-Curie ll • 1990: Nuclear medicine development with scintigraphy and positron emission tomography. Nuc 3 Terminology

• Transmission: Photons passing through the body • Absorption: Partial or total absorption of energy in the patient • Scatter: Radiation diverted in a new direction

Source: Utrecht University, NL • Transaxial - plane normal to a vector from head to toe. • Coronal - plane normal to a vector from front to back • Sagittal - plane normal to a vector from left to right. • Oblique – otherwise.

4 Imaging Data Types •2D: – A single slice. •3D: – A series of parallel slices with uniform spacing. – A series of slices with varying spacing and/or orientation. – A volumetric data set.

5 Imaging Support

Films Digital Display (hard copy) (soft copy) 6 Imaging Modalities

•X-Ray: – Traditional – Computerized Tomography • Ultrasound • Magnetic Resonance Imaging (MRI) • Nuclear Imaging

7 Conventional X-Ray

8 Conventional X-Ray

Physics Principles X-ray s E ≈ 5-150keV • Accelerating & decelerating electrons generate electromagnetic radiation • Bombardment of a target material with a e- beam of fast electrons A C • Electrons are emitted thermally from a heated cathode (C) and are accelerated tdthdtt(A)bthlidtoward the anode target (A) by the applied voltage potential V (~kV). V = 5-150kV • Electromagnetic radiation is produced by - + the quick deceleration of the electrons when hitting the target (bremsstrahlung). hν – ~99% of energy converted into heat. – Few generated X-ray photons with wavelength set by the amount of energy E1 loss E=hν=E2-E1 Nucleus E2 9 Conventional X-Ray

IFtiImage Formation • X-ray beam goes though the pa tien t with decrease energy, function of the absorption pattern inside Primary X-rays the body. patient

collimator

Screen + detector

10 Conventional X-Ray

ICtImage Capture • Image captured on phhhosphor screen, w ith conversion to visible light. Primary X- • Recording on film rays (negative image) patient lead • Display on video monitor (positive ima ge ) detector

11 Conventional X-Ray

StSystem D Diesign cathode scatters

lead

VERRE BOMBARDE

CONE PLOMBE

HUILE oil Optical field

Optical field 12 Conventional X-Ray

StSystem D Diesign

13 Conventional X-Ray

• Advantages: •Fast. • Inexpensive. • Disadvantages: • Ionizing radiation involved. • Projection images. • Poor blood vessel and soft-tissue contrasts.

14 Conventional X-Ray

• Applications: – Lungs, breasts, GI track. – Blood vessels (contrast agent). – Bones, joints .

15 Source: http://www.szote.u-szeged.hu/Radiology/Anatomy/ Conventional X-Ray Examples: Bones

11. Mastoid cells 1. Frontal sinus 12. NhNasopharynx 2. Ethmoidal sinus 13. Angle of mandible 3. Sphenoidal sinus 14. Anterior arch of the atlas 4. Maxillary sinus 15. Dens of axis 5. Anterior clinoid processes 1. Bifid spinous process of C3 16. Posterior arch of the atlas 6. Hypophyseal fossa 2. Superimposed articular processes 17. Internal occipital protuberance 7. Posterior clinoid processes 3. Uncinate processes 8. Clivus 4. Air filled trachea 9. Great density of the petrous A. Coronal suture 5. Transverse process of C7 part of the temporal bone B. Lambdoid suture 6. Transverse process of T1 10. External acoustic meatus C. The grooves for the branches of the 7. 1st rib middle meningeal vessels 8. Clavicle 16 Conventional X-Ray Examples: Lungs Patient with hemo-pneumothorax Patient with pacemaker Pleura l line

air + fluid

Source: www.mypacs.net 17 Conventional X-Ray Examppgpyles: Mammography • Low kV can be used (little attenuation) => sufficient photoelectric absorption to differentiate between normal tissue and pathology • Dose must be limited . • Breast must be compressed – To avoid motion. – To minimize focus/film distance. – To have equal tissue thickness.

18 Conventional X-Ray Examples: Fluoroscopy • Real-time X-ray imaging. • Direct v isu aliz ation on screen. • Used for guidance of interventions (mainly vascular and orthopedic).

Ex: Fluoroscopic guidance with umbilical catheter injecting contrast agent in the small bowel.

Source: www.mypacs.net 19 Conventional X-Ray Examples: Fluoroscopy

patient

C-arm

Source: Utrecht University , NL cathode 20 CtidThComputerized Tomography (CT)

21 CT

Physi cs P ri nci pl es • Same as X-ray.

22 CT

IFtiImage Formation • Same as X-ray.

23 CT

ICtImage Capture Measure = integral attenuation • Generation of a sliced view of body interior ((T)“T”) µ(x,y) ? (cf. tomos = slice in Greek).

• Computational intensive Patient’s image reconstruction (“C”). body

X-ray source

24 CT

ICtImage Capture • Translation and rotation of integral measure of absorption. • Backprojection

⎛ ⎞ I = Ioexp⎜− ∫ µ(x, y)dl⎟ ⎝ L ⎠ ⎛ I ⎞ => µtotal = ∫ µ(x,y)dl = −ln⎜ ⎟ L ⎝ I0 ⎠

25 CT g(s,θ) Image Capture: Backprojection ⎛ ⎞ I = Ioexp⎜− ∫ µ(x, y)dl⎟ y ⎝ ⎠ x’ L y’ s ⎛ I ⎞ g ≡ ln⎜ o ⎟ (Signal) θ ⎝ I ⎠ µ(x,y) unknown x absorption g(s,θ) = ∫ µ(x, y)dl L

The Radon transform g(s,θ) of a function µ(x,y) is defined as its line integral along a line inclined at an angle θ from the y-axis and at a distance s from the origin. 26 CT Image Capture: Backprojection

g(s,θ) = ∫ µ(x, y)dl g(s,θ) L y • The Radon transform maps x’ y’ the spatial domain (x,y) to the s domain (s,θ). • Each point in the (s,θ) space θ corresponds to a line in the µ(x,y) spatial domain (x,y). unknown x absorption g(s,θ) = ∫∫ µ(x, y)δ (x cosθ + ysinθ − s)dxdy = ∫ µ(s cosθ − y' sinθ,s sinθ + y' cosθ)dy'

27 CT 2D-frequency Image Capture: Backprojection domain of µ((,y)x,y) Radon Transform & Projection Theorem (Center slice theorem) 2D-space domain of µ(xyx,y)

g(s,θ) s ω y 1D-Fourier y transform θ θ F(g()(s))

x ωx µ(xyx,y)

28 CT Image Capture: Hounsfield Units

• Relates the linear attenuation coefficient of a local region µ to the linear attenuation coefficient of water, µW @ 70 keV (=Eeff). • Based on measu rements w ith the original EMI scanner inv ented by Hounsfield.

µ − µ HU = 1000 • w µ w

• Assign calibrated values to gray scale of CT images. 29 CT

StSystem D Diesign • 1st generation: Original resolution: Translation 80 × 80 pp(ixels (ea. 3 × 3 mm2), & Rotation 13mm slice thickness, 5min scan time, 20min reconstruction.

• 2nd generation: reduced number of Translation view angles ⇒ scan time ~30 s. & Rotation • 3rd generation: scan time ~seconds (reduced dose, motion artifacts). Reconstruction time only ~seconds. Rotation CT

StSystem D Diesign • 4th generation: scan time, reconstruction time ~sec.

only Rotation of sources

• Spiral: Continuous linear motion of patient table during multiple scans. IdIncreased coverage vol ume per rotation. CT Example: Image quality 1975 2000

128x128 pixels, 1-4 hours acquisition, 512x512pixels, 0.35 sec aquisition, 1-5 days computation <1sec computation 32 CT Example: Lungs

33 CT Example: Lungs

Ex: CT of right lung with active pulmonary tuberculosis: shows centrilobular lesions (nodules or bhilitt2branching linear structures 2-4idit)4 mm in diameter) in and around the small airways.

Source: www.mypacs.net

34 CT Examples: Abdomen

Diagnosis of appendicitis 35 CT Example: Abdomen Scout CTTRA CT Coronal MPR

Source: www.mypacs.net Virtual endoscopy

36 CT Example: Blood vessels

37 CT Example: Blood Vessels

38 CT

Vitrea© 39 CT • Calcium Scoring

TtlSTotal Score = S

Hn x-factor (Agatston Scoring)

130-199 1

200-299 2

300-399 3

>400 4

Area = 15 mm2 Area = 8 mm2 Peak CT = 450 Peak CT = 290 Score = 15 x 4 = 60 Score = 8 x 2 = 16 40 Ultrasound

41 Ultrasound

Physi cs P ri nci pl e • Traveling pressure waves through a medium.

42 Ultrasound

Physi cs P ri nci pl e

20 Hz 20 kHz 1MHz1 MHz 20 MHz infra- audible sound ULTRASOUND sound Diagnostic Ultrasound

101 102 103 104 105 106 107 15 Freqqy()uency f (Hz) flight ~ 10 18 fxray ~ 10 43 Ultrasound

IFtiImage Formation

• Sound waves propagate N e throug h the bo dy. ar Fiel

• At each interface, part is d reflec ted , par t i s transmitted. Far F • RfltdReflected waves are ield recorded back.

Source: The essential physics of Medical Imaging 44 Ultrasound transducer Ultrasound Pulse IFtiImage Formation

Echo

Echo TISSUE D = c×Time/2 c=154mm/c = 1.54 mm/µs

45 Ultrasound Imaggpe Capture • Recorded signals: – Specular reflection, Diffuse scattering, Rayleigh scattering • Frame rate (FR) =number of times per second a sweep of the ultrasound beam is T_line = 2×D/c performed. – The higher the frame rate, the T_frame = N ×Tline = better the temporal resolution. 2×N×D/c – Limited by: • Time delay from maximum depth. FR_max = 1/ Tframe • Speed of sound.

46 Ultrasound Piezoelectric Element StSystem D Diesign AtiIltAcoustic Insulator Transducer

Electric Connector Backing Material Phased array transducer Matching Layer Displ ay

47 Ultrasound

• Advantages: – Portable. – Inexpensive. – Good spatial resolution (~1mm). – High temporal resolution. • Disadvantages: – Poor image quality. – High level of noise.

48 Ultrasound

StSystem D Diesign

A-mode amplitude display

B-mode Br ight ness di spl ay (Gray-scale) 49 Ultrasound

StSystem D Diesign

A-mode B-mode

50 Ultrasound Applications • Obstetric • HtHeart • GI track (liver, gall bladder, pancreas) • Urinary track (bladder, kidneys) • Genital organs (prostate, testicles, ovaries, uterus). • Blood vessels (Doppler).

51 Ultrasound Example: Blood vessels

– Establish number of fetus. – Check position of placenta. – Determine fetal age and development. – Check for congenital defects. – Check fetus position.

52 Ultrasound Example: Obstetric

1961: First image of fetus 1990: First 3D visualization of fetus

53 Ultrasound Example: Heart - Valve diseases. - Cardiac function (pumping efficiency). - Bloo d c lo ts in car diac c ham ber.

54 Ultrasound Example: Heart

• Real-Time 3D Ultrasound 55 Ultrasound •Bioppygsy guidance. Examples: Abdomen • Diagnosis of abdominal pains, kidney stones, inflamed appendicitis. kidney

appendicitis liver 56 Ultrasound Example: Blood vessels • Artery blockage from blood clots. • Arteriosclerosis (plaques). • Stent position

57 Ultrasound Example: Blood vessels • Doppler

58 Magnetic Resonance Imaging (MRI)

59 MRI • Nuclei with magnetic dipoles Physi cs P ri nci pl e (H). • Magnetic field B0 makes No magnetic field Magnetic field nuclei precess along its direction. • The precession rate is the Larmor frequency.

• fL = γ B0 (43×15=64MHzfor1.5 = 64 MHz for Hydrogen into a 1.5T magnet).

Source: Hielscher, Columbia Univ. 60 MRI Image Formation • Nuclei with maggpnetic dipole moment µ, and angular momentum S. z • Net magnetization M = density of µ. B0 n m = rg z

EE ee yy +1/2 • Tip M away from B0 ⇨ Precession at frequency γB0, producing a measurable ∆Ε = γΒSpin0 RF magnetic field. mflipz = -1/2 transi Z | B0 tion J or µ or M • For every 1,000,000 nuclei in upper state (mz=+1/2)B there are 1,000,001 nuclei in lower state0 (mz=-1/2). • This difference| is enough to result in macroscopic nettitiftilt magnetization of material. Y

|B0|×γ×t X 61 MRI Image Capture • As the magnetization precesses it creates its own RF magnetic field. Z • This field is much smaller than the B0 exciting RF field. J or µ or M • It can be detected with a standard radio receiver (e.g. RF coils used to tip M away from B0) • The resulting signal from precession is Y called the Free Induction Decay or FID. |B0|×γ×t

62 MRI System Design • Main Magnet – High, constant,Uniform Field, B0 B0. • Gradient Coils B – Produce pulsed, linear gradients in 0

this field: Gx, Gy, & Gz B • RF coils 1

– Transmitter: B1 Excites NMR signal B0 to generate Free Induction Decay ( FID). – Receiver: Senses FID. 63 MRI System Design Magnet + shielding + cooling systems

ggyantry

64 MRI

• Advantages: – High image quality. – Good spatial resolution (~1mm). – All tissues (except lung). • Disadvantages: – Very expensive scanners. – Some patients cannot be imaged (pacemaker, claustrophobia).

65 MRI Applications • Brain (Multiple sclerosis, Alzheimer’s disease, epilepsy, tumors) • Spine • Muscles, tendons. • Blood vessels: angiography (strokes, aneurism) • Heart • soft tissues

66 MRI Example: Heart • CINE MRI

Courtesy of Robert R. Edelman 67 MRI Example: Heart

MRI for myocardial perfusion 68 MRI Example: Blood vessels

MtiRMagnetic Resonance Angiography

69 MRI Example: Blood vessels

Aorta 70 MRI Example: Brain

71 MRI Example: Brain • Diagnosis of Alzheimer’s and Parkinson’s disease.

72 MRI Example: Blood vessels

MR Angiography

73 Nuclear Imaging (PET & SPECT)

74 Nuclear Imaging

Physi cs P ri nci pl e: PET Nuclear imaging is the use of radioactive materials for imaging structures and function inside the body.

75 Nuclear Imaging

Physi cs P ri nci pl e: PET • In unstable nucleus, (more protons than neutrons) proton converts to neutron under emission of positron. • Positron travels limited distance in tissue. • Positron can combine with electron of nearby atom and emits two 511 keV X-ray photons (γ rays) that travel in opposite direction.

76 Nuclear Imaging

ICtImage Capture: PET

Anger Camera

77 Nuclear Imaging

ICtImage Capture: PET

78 Nuclear Imaging

ICtImage Capture: SPECT

79 Nuclear Imaging

ICtImage Capture: SPECT

80 Nuclear Imaging

StSystem D Diesign: PET

PM: photo multiplier

81 Nuclear Imaging unknown StSystem D Diesign: SPECT activity & absorption cross-section • Coincidence occurs with α(x,y) ,µ(x,y)

simultaneous detection of )) θ

2 opposite detectors. , • Number of counts at the σ L I( 1 detectors gives the line Lmax integral LLmax⎛⎞ max • Use standard g(s ,θα )=−∫∫ (xy , µ )exp⎜⎟ ( xydldl , thtomography LLmin⎝⎠ 1 reconstruction algorithm problem is ill-posed! or statistical approaches ⇒ different combinations of (EM). α and µ can yield identical measurements 82 Nuclear Imaging

• Advantages – Functional imaggging. • Disadvantages – Poor spatial resolution (~ 8mm). – High level of noise. – Expensive hardware. – Need of cyclotron.

83 Nuclear Imaging Applications

• Heart • Lungs • Kidneys • Bladder • GI Track • Endocrine system (hormones) • Immune system (white blood cells).

84 Nuclear Imaging Whole Body

Clinical History: A 71year-old male with history of lung carcinoma, now with bilateral pulmonary nodules and mediastinal Figure 1. Whole-body gallium-67 scan adenopathy.Findings: Bone Scan: Increased showing lymphoma in the chest, the spleen, the abdomen, and the groin. The chest and radiopharmaceutical uptake along cortical spleen sites were known before the scan. The margins of the bilateral femurs and tibias. No abdominal and groin uptakes were detected evidence of bony metastases . only by the scan. Source: http://www.nucmednet.com/galymph.htm Diagnosis: Hypertrophic osteoarthropathy http://www.uhrad.com/spectarc.htm 85 Nuclear Imaging Example: Lung SPECT scan for lung perfusion (pulmonary embolism)

Source: Brigham & women’s Hospital 86 Nuclear Imaging Example: Heart • Perfusion Imaging

Stress exams

Abnormal Stress blood flow

Normal blood flow Rest

87 Nuclear Imaging Example: Brain

Source: www.med.harvard.edu/AANLIB 88 Nuclear Imaging Example: Brain

Source: www.med.harvard.edu/AANLIB 89 Nuclear Imaging Example: Brain PET with FDG tracer for diagnosis of brain tumor

Source: V. Cunningham, GlaxoSmithKline. 90 Nuclear Imaging Example: Brain PET for in-vivo testing of new drugs

Source: V. Cunningham, GlaxoSmithKline. 91 Research in Medical Imaging

92 Research in Medical Imaging • Topics – Improve image quality. – Extraction of organ contours. – Quantitative measures on organs (volume, cardiac function, deformations, contractility,…). – Modelization of organs. – Validation of image information for diagnosis. – Tumor detection. – Functional analysis , neuroscience . • Tools: – Computers, mathematics, programming, biology, physics, clinical studies.

93 Research in Medical Imaging Example: Denoising of 3DRX spitdine study

Original Gaussian filtering

Denoising Application Wavelet Adaptive Wavelet Thresholding Thresholding 94 Research in Medical Imaging Example: Registration of MRI and PET abd omen i mages

95 Research in Medical Imaging Example: Segmentation of cortical b rai n st ruct ures

96 Research in Medical Imaging Example: Segmentation of sub-cortical st ruct ures

Lateral ventricles Third ventricle Caudate nucleus Thalamu s

97 Research in Medical Imaging Example: Segmentation of sub-cortical st ruct ures

98 Research in Medical Imaging Example: Diffusion Tensor MRI for Bra in White M att er Fib ers

99 Research in Medical Imaging Example: Functional Brain MRI

Motor control of fingers

100 Research in Medical Imaging Example: Functional MRI

Motor control of right hand 101 Research in Medical Imaging Example: Fetal Imaging

102 Research in Medical Imaging Example: Fetal Imaging

103 Books

•Foundation of Medical Imaging, Z.H. Cho, J.P. Jones, M. Singh, John Wiley &Sons, Inc., New York 1993, ISBN 0-471- 54573-2.

•Principles of Medical Imaging, K.K. Shung, M.B. Smith, B. Tsui, Academic Press, San Diego 1992, ISBN 0-12-640970-6.

•The Essential Physics of Medical Imaging (2nd Edition) ,Jerrold T. Bushberg, J. Anthony Seibert, Edwin M. Leidholdt Jr., John M. Boone, Lippincott Williams & Wilkins; 2nd edition, ISBN 0683301187.

•IRImage Reconstructi iiRdilon in Radiology, J.A . P ark er, CRS Press, Boca Raton, FL 1990, ISBN 0-8493-0150-5/90.

•Principles of Magnetic Resonance Imaging, Zhi-Pei Liang, P.C. Lauterbur IEEE Press, New York, NY 2000, ISBN 0-7803- 4723-4. 104