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Modern Medical Imaging

Nuclear Medicine, PET, SPECT Interventional Radiology

X-Ray Computed Tomography (CT) Ultrasonography (US)

Magnetic Resonance Imaging (MRI) Radiography and Angiography

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Molecular Imaging Definitions

Molecular Imaging is the visualization, characterization, andmeasurement of biological processes at the molecular and cellular levels in humans and other living systems.

•Includes 2D and 3D imaging and quantification over time•Radiotracer imaging and nuclear medicine•MR imaging and MR spectroscopy•Optical imaging•Ultrasound•Other techniques

SNM and MICoE Standard Definitions Task Force, 2007

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Molecular Imaging Definitions

Molecular Imaging Agents are probes used to visualized,characterize, and measure biological processes in living systems.

•Endogenous molecules

••Exogenous probes

Molecular Imaging Instrumentation comprises of tools that enablevisualization and quantification in space and time of signals frommolecular imaging agents.

SNM and MICoE Standard Definitions Task Force, 2007

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Molecular Imaging Definitions

Molecular Imaging Quantification is the determination of regionalconcentrations of molecular imaging agents and biologicalparameters.

•Provides measurements of processes at molecular andcellular levels.

•Quantification is key for MI data and image analysis, inter-and intrasubject comparisons.

SNM and MICoE Standard Definitions Task Force, 2007

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Instrumentation Needs for Molecular Imaging

•Contrast Resolution•

•Spatial Resolution•

•Temporal Resolution

Achieved through combination of imagingsystem, intrinsic or extrinsic contrast.

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Noninvasive in vivo Small Animal Imaging and Intervention

Magnetic Resonance Imaging Optical Imaging: Fluorescence & Bioluminescence

 μ -CT, PET, SPECTHybrid Imaging Systems

Ultrasound

Targeted Therapy

Molecular Theranostics

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Exogenous Imaging Probes

Weissleder . Nat Rev Cancer 2:1-8, 2002

-Enzyme activatable NIR fluorochromes

 Magneticnanosensors

 Activatable paramagnetic

chelators

,Most clinical MRI,CT US contrast

agents

 Most clinical,nuclear medicine

,PET SPECTradiotracers

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Concentration Sensitivity of Imaging Modalities

Imaging Technique Sensitivity (mol/L)PET 10-11 -10-12

SPECT 10-10 -10-11

CT Not well characterizedMRI 10-3-10-5

Ultrasound Not well characterized

Bioluminescence 10

-13

-10

-16

Fluorescence 10-9-10-11