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Multimodality Imaging (MRI, PET, CT, etc..) Jonathan Dyke, Ph.D. Assistant Research Professor of Physics in Radiology Citigroup Biomedical Imaging Center.

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Presentation on theme: "Multimodality Imaging (MRI, PET, CT, etc..) Jonathan Dyke, Ph.D. Assistant Research Professor of Physics in Radiology Citigroup Biomedical Imaging Center."— Presentation transcript:

1 Multimodality Imaging (MRI, PET, CT, etc..) Jonathan Dyke, Ph.D. Assistant Research Professor of Physics in Radiology Citigroup Biomedical Imaging Center Weill Cornell Medical College Sackler Institute for Developmental Psychobiology Summer Lecture Series July 9, 2009


3 Cyclotron Radiochemistry

4 Cyclotron design from Ernest Lawrence’s 1934 patent application.

5 #protons + #neutrons = Mass # Atomic # = # protons (never changes) Basic HS Chemistry is useful. What does the atomic # define? What does the atomic mass define?

6 Radioisotope Production

7 16 O + p -> 18 F + n 89 Target Material: Purified Water Production of 18 F precursor to FDG

8 Positron Emission Tomography “PET” Scan (“DOG” Scan)

9 Is a positron stuff of fiction? e + + e - ->  a +  b

10 Courtesy: Brookhaven National Lab PET: Coincidence Detection

11 Filtered Back Projection (Key for both PET and CT!) Courtesy: Univ British Columbia

12 Clinical Applications of PET Alzheimer’s Disease

13 Primate - 11 C-Raclopride Imaging Courtesy: Shankar Vallabhajosula, Ph.D.

14 18 F-FDG Lymphoma Study: 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG)

15 11 C-5-Hydroxytryptophan (5-HTP)

16 Image Analysis: Standard Uptake Value: Courtesy: PET/CT in clinical practice By T. B. Lynch, James Clarke Pre-Tx SUV=15 Post-Tx SUV=2

17 Computed Tomography “CAT Scan”

18 Creation of X-Rays Circa 1896

19 Circa 1900 Circa 2000 X-Ray Tube Construction

20 X-Ray Densities Do the following appear Dark or light on an X-Ray image? Air Fat Bone

21 CT Hounsfield Units

22 CT Hardware

23 Advantages: 1)CT completely eliminates the superimposition of images of structures outside the area of interest. 2) because of the inherent high-contrast resolution of CT, differences between tissues that differ in physical density by less than 1% can be distinguished. 3)data from a single CT imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as images in the axial, coronal, or sagittal planes, depending on the diagnostic task. This is referred to as multiplanar reformatted imaging. In the ED it’s FAST!

24 CT Diagnostic Utility: Head: Chest: Cardiac: Abdominal and pelvic: Extremities: Trauma, Stroke, Tumor, Biopsy Lungs, Pneumonia, Emphysema, Embolism Coronary artery disease (High Dose) Renal stones, appendicitis, pancreatitis, diverticulitis Fractures, dislocations.

25 CT - Stroke

26 CT Perfusion CBF CBV MTT AJNR 2000;21:1441–1449.

27 CT Radiation Dose Diagnostic Advantage Vs. Increased Risk Cancer Assumes linear relationship between radiation dose and cancer risk (Controversial). Risk for pediatric patients developing cancer from CT scan is greater than adults. ~ 500 in every 600,000 scans. “CT is an extremely valuable tool, and nobody should hesitate to undergo CT when it is indicated.”



30 Dia Weakest  -1 Para Weak  ~10 Ferro Strong  ~25,000 Super Strong  ~5000 Magnetism of Materials

31 How does it affect the signal? What type of material is Gadolinium? How many unpaired e - does in Gd-DTPA? What compound do we detect the effect of contrast on?

32 Contrast Mechanisms Dictate Method of Study in Magnetic Resonance Imaging How does an agent affect relaxation times? 1 = 1 + R 1,2 C T 1,2 T 10,20 Solomon-Bloembergen Equations (1955)

33 What factors influence whether the T 1 or T 2 effect will dominate the MRI signal?

34 Clinical Apps: Why are contrast agents necessary given the excellent resolution of un-enhanced MRI images? When is a contrast scan prescribed? Tumor, Stroke, Angiography CNS disease

35 But.. Talk is cheap..

36 Nephrogenic Systemic Fibrosis



39 What physical aspects or systems In nature exhibit diffusion? What principles govern diffusion?

40 The “Drunken” Walk Einstein – 1905 How far does a drunk walk? = 2 D t vs. R(t)= v t D H O = 3x10 -3 mm 2 /s D brain = 1x10 -3 mm 2 /s 2

41 What affect does diffusion have on the MRI signal? S=S 0 e –b D DWI Atten Brain = 1/(2.782) DWI Atten CSF = 1/(2.782^3)

42 How can you image diffusion at the cellular level accounting for patient motion? Patient motion ~ 1-2mm Diffusion length ~ 10-100  m

43 90 o Excitation Image Acquisition RF Gx Gy Gz G 180 o G Pulse Sequence: Spin-Echo Diffusion Weighting

44 Why the different contrast between a DWI & ADC image? DWI = ADC

45 Clinical Apps: Acute AML pre/post Tx *Courtesy: Doug Ballon, 2003

46 A.W. Song, Isotropic vs. Anisotropic

47 Diffusion Tensor Imaging 3T MRI – NYP - Tumor



50 Roy, C.S., and Sherrington, C.S. 1890. On the regulation of the blood supply of the brain. J. Physiol. 11:85-108. 100 years pass….. Ogawa, S., Lee, T.M., Nayak, A.S., and Glynn, P. 1990. Oxygenation-sensitive contrast I magnetic resonance image of rodent brain at high magnetic fields. Magn. Reson. Med. 14:68-78.

51 Oxyhemoglobin is diamagnetic Deoxyhemoglobin is paramagnetic Neuronal activity->Less deoxyhemoglobin Less susceptibility difference between capillary vessel and brain tissue Longer T 2 * Signal increase in T 2 * Sequence How big an increase are we talking about? How does BOLD really work?

52 Blood Oxygen Level Dependent Signal Source: Buxton book Ch 17

53 Dale & Buckner, 1997 Hemodynamic Response Repeated Trials – Dale/Buckner 1997

54 Motor Activation in AFNI

55 Where do we expect activation?

56 Cortical mapping in the surgical suite.

57 Neuron, 2006,18;643-653. – Courtesy BJ Casey

58 Clinical Apps: Improving clinical procedures, e.g. presurgical planning for brain tumors Direct: Mapping of functional properties of adjacent tissue Indirect: Understanding of likely consequences of a treatment Understanding cognition Studying brain development Investigating brain physiology ** Henning – Minimally Conscious State


60 Physiologically, what happens when a tracer enters the blood supply? What factors influence the distribution and kinetics? Johns Hopkins – Dept Radiology

61 T 1 W – DCE MRI DYNAMIC CONTRAST ENHANCED IMAGING 2D Fast Spoiled Gradient Echo, 12 mm slice, 8/0 slices, TR/TE 8 ms/2 ms, 15.63 kHz RBW, 22 cm FOV, 256 x 128 matrix, 8.56 sec/resolution

62 1 2 3 4 Pediatric Osteogenic Sarcoma: Post-Chemotherapy Grade IV Responder: 100% Necrotic 1 4 3 2

63 DCE-MRI & ANGIOGENESIS What role does neovasculature fill in tumor growth? (Goldman,1907) How far from a vessel can a tumor cell survive? (Thomlinson & Gray,1955) Does DCE produce any physiologically significant parameters?

64 Pharmacokinetic Modeling of Tracer Kinetics (Kety, 1951) v e dC e (t) = K trans (C p (t)-C e (t)) dt Cp

65 k ep Interstitial Lesion k el K in k 12 Plasma Intravascular Brix/Hoffman 2 Compartment Model Gd-DTPA 0.1 mM/kg

66 Does this model actually fit real data?

67 CLINICAL APPS: Tumors: breast, brain, bone Drug Trials: anti-angiogenic Arthritis: joint/synovium BBB leakage/permeability


69 Representative Perfusion Maps MTT EPI CBF CBV 62 year old with left MCA territorial stroke. The perfusion maps show prolonged MTT with corresponding decreased CBF and CBV.

70 “Arterial Input Function” Raw SI-ln(S/S0) Minutes

71 “CT Perfusion is for wimps.” Difficulties in MRP quantitation. Delay Dispersion Saturation Effects Partial Volume Effects Susceptibility Masking Conversion to Concentration Refs: van Osch,2000; Rausch,2001; Wu,2003

72 Cerebral Blood Volume Cerebral Blood Flow Mean Transit Time MTT=CBV/CBF Central Volume Theorem CBF (ml/100 gm/min) Normal GM = 39+/-10.3 Normal WM = 14.7+/-4.1 Ischemia < 10.0 CBV (ml/100 gm ) Normal GM = 4.4%+/-0.9 Normal WM = 2.3%+/-0.4 Ischemia = >6 ml

73 DWI/PWI Services in Stroke:


75 NMR Active Nuclei What can we see?

76 Raw Signal “FID” FFT

77 “Chemical Shift” Electron Shielding

78 Water = 4.7ppm Lipid = 1.3 ppm  =(4.7-1.3) ppm*127.5MHz = 434 Hz @ 3.0 Tesla T=1/  = 2.3 ms (IP, OOP)

79 NAA CHO CRE LAC 1 H Metabolites

80 A sampling of 1 H metabolites

81 Ex-vivo Mouse brain perchloric acid extract @ 11.4T What price is paid in detecting these signals?

82 Grade III GBM Pre-Tx Dyke JP, Sanelli PC, Voss HU, Serventi JV, Stieg PE, Schwartz TH, Ballon D, Shungu DC, Pannullo SC. Monitoring the Effects of BCNU Chemotherapy Wafers (Gliadel®) in Glioblastoma Multiforme with Proton Magnetic Resonance Spectroscopic Imaging at 3.0 Tesla. J Neurooncol. 2007 Mar;82(1):103-10.

83 31 P Metabolites @ 3.0 Tesla

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