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:
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
Cyclotron design from Ernest Lawrence’s 1934 patent application.
#protons + #neutrons = Mass # Atomic # = # protons (never changes) Basic HS Chemistry is useful. What does the atomic # define? What does the atomic mass define?
16 O + p -> 18 F + n 89 Target Material: Purified Water Production of 18 F precursor to FDG
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
Computed Tomography “CAT Scan”
Creation of X-Rays Circa 1896
Circa 1900 Circa 2000 X-Ray Tube Construction
X-Ray Densities Do the following appear Dark or light on an X-Ray image? Air Fat Bone
CT Hounsfield Units
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!
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.”
Roy, C.S., and Sherrington, C.S On the regulation of the blood supply of the brain. J. Physiol. 11: years pass….. Ogawa, S., Lee, T.M., Nayak, A.S., and Glynn, P Oxygenation-sensitive contrast I magnetic resonance image of rodent brain at high magnetic fields. Magn. Reson. Med. 14:68-78.
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?
Blood Oxygen Level Dependent Signal Source: Buxton book Ch 17
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
MR PERFUSION IMAGING
Physiologically, what happens when a tracer enters the blood supply? What factors influence the distribution and kinetics? Johns Hopkins – Dept Radiology
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, kHz RBW, 22 cm FOV, 256 x 128 matrix, 8.56 sec/resolution
Pediatric Osteogenic Sarcoma: Post-Chemotherapy Grade IV Responder: 100% Necrotic
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?
Pharmacokinetic Modeling of Tracer Kinetics (Kety, 1951) v e dC e (t) = K trans (C p (t)-C e (t)) dt Cp
k ep Interstitial Lesion k el K in k 12 Plasma Intravascular Brix/Hoffman 2 Compartment Model Gd-DTPA 0.1 mM/kg
Does this model actually fit real data?
CLINICAL APPS: Tumors: breast, brain, bone Drug Trials: anti-angiogenic Arthritis: joint/synovium BBB leakage/permeability
T 2* W – DSC MRI DYNAMIC SUSCEPTIBILITY CONTRAST
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.
“Arterial Input Function” Raw SI-ln(S/S0) Minutes
“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
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
DWI/PWI Services in Stroke:
NMR Active Nuclei What can we see?
Raw Signal “FID” FFT
“Chemical Shift” Electron Shielding
Water = 4.7ppm Lipid = 1.3 ppm =( ) ppm*127.5MHz = Tesla T=1/ = 2.3 ms (IP, OOP)
NAA CHO CRE LAC 1 H Metabolites
A sampling of 1 H metabolites
Ex-vivo Mouse brain perchloric acid 11.4T What price is paid in detecting these signals?
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 Mar;82(1):