Molecular Imaging &Positron Emission Tomography  

Nicholas Mulhern BME 281

Molecular Imaging• Produces Images of the body• Allows Visualization of the cellular function• Fine molecular changes• understanding molecular pathways

• Allows for quantitative tests• More objectivity to the study of Specific Areas

• Noninvasive manner• Origins in the 1950’s

Why its important?• Earlier and more precise Disease diagnosis• Cancer• Neurological • Cardiovascular diseases

• Elucidate biochemical processes• Track the impact of experimental drugs• clinical trials

• Many Applications • Oncology, Neuroimaging, Cardiology, Pharmacology Small animal

imaging, Musculo-skeletal imaging

(PET) • Provides a three-dimensional image or picture of functional

processes in the body• blood flow • other biochemical functions

Biomarkers

• Injected into Patient• tagged with a radioactive atom

• Molecule determines the function imaged

• Indicator of the Biological state• Help image particular targets or

pathways• Chemically interact with their

surroundings • Alter Images according to Molecular

changes• Carbon-11, Fluorine-18, Oxygen-15, or

Nitrogen-13• short decay time positron emitting radionuclide

Fluorodeoxyglucose (FDG)

Gamma Ray Detector• Flat table moves incrementally within Housing • Circular Gamma ray detector Array

• “Donut Shaped”• Contains series of scintillation crystals• connected to a photomultiplier tube

• Scintillation crystals• convert the gamma rays, emitted from the patient, to photons of light

• Photomultiplier Tubes • Convert and amplify the photons to electrical signals

Electrical signals • Electrical signals are then processed by the computer to

generate images• The table is then moved• process is repeated• Time Dedication• 60 min Resting Period• Scan 30 minutes

• Analytical results within • 24 hours

Result Imaging

• Resulting in a series of thin slice images • Region of interest • brain, breast, liver• These thin slice images can be assembled into a 3D representation of

the patient's body

shows that leukemia present in the bone marrow before treatment, left, persisted after chemotherapy, right.

Brain scans of a healthy person (top of image) and a person with schizophrenia (bottom)

Today • Few PET centers in the country • Must be located near a particle accelerator device • It produces the short-lived radioisotopes used in the technique

• PET/CT scanner "co-registration" • Combines CT X-ray Scan simultaneously • Provides Anatomic Info: what the structure is • Metabolic Inform: what it is doing biochemically

• TIME Magazine as the medical invention of the year in 2000

A complete body PET/ CT Fusion Image

Sources• http://www.rikenresearch.riken.jp/eng/frontline/6414• http://mips.stanford.edu/grants/icmic/2010-2015/• http://www.howstuffworks.com/nuclear-medicine1.htm• http://blog.cleveland.com/medical/2009/03/

is_my_chemo_working_new_use_fo.html• http://sitemaker.umich.edu/pet.chemistry/

positron_emission_tomography• http://www.biologyreference.com/Po-Re/Psychiatric-

Disorders-Biology-of.html#b