1. Positron Emission Tomography
Magnetic Resonance
Imaging
&
Positron Emission Tomography
AUBREY OVERSON

2. OUTLINE COMPARISON PET SCAN ~positron emission ~making of isotopes
~detector
MRI
~A bit of physics of the system
~image reconstruction
COMPARISON

3. Positron Emission Tomography
Simultaneously & collinear
produces two photons
with energy 511 KeV (mec2)
travel nearly 180º back to back
this is measured by a coincidence detector

4. 11C=20.34min; 13N=9.96 min; 15O=2.05 min; 18F =110min;
CYCLOTRON
Also has better radionuclides with a low atomic numbers (11C, 13N, 15O, 18F)
which have a higher affinity of the human body as well as relatively short half lives…
11C=20.34min; 13N=9.96 min; 15O=2.05 min; 18F =110min;

5. collimator crystal  photomultiplier  coincidence circuit
Scintillation Camera
collimator crystal  photomultiplier  coincidence circuit

6. IMAGE RECONSTRUCTION 2D projection  3D Image
Filtered Back-projection (FBP).
MRI contrast works by altering the local magnetic field in the tissue being examined. Normal and abnormal tissue will respond differently to this slight alteration, giving us differing signals. These varied signals are transferred to the images, allowing us to visualize many different types of tissue abnormalities and disease processes better than we could without the contrast.

7. Magnetic Resonance Imaging (MRI)
Larmor Frequency

8. More MRI details
When the RF pulse is turned off, the hydrogen protons begin return to their natural alignment within the magnetic field and release their excess stored energy. When they do this, they give off a signal that the coil now picks up and sends to the computer system. What the system receives is mathematical data that is converted, through the use of a Fourier transform, into a picture that we can put on film. That is the "imaging" part of MRI.

9. COMPARISONS PET MRI 500 machines in US Very common Metabolic processes
Advantage of false color
More sensitivity and resolution than SPECT or CT
$ dollars per scan
MRI
Very common
does not use ionizing radiation is a comfort to many patients, ability to image in any plane.
It gives images of brain tumors, abscesses, swelling, bleeding, nerve damage, and other disorders that increase the fluid content of tissues.