Physics of PET /Radiation Safety
Final Exam - Take Home
May 25, 2007
Test is due June 25, 2007
This exam includes material from the entire semester
Show all work.
USE SEPARATE PAPER FOR ALL ANSWERS
Be sure to write your name on the paper that you use.
Remember, credit is given for work shown, not simply the correct answer.
1. Find the unknown element X in the following reaction equations for cyclotron produced
radionuclides:
A:
1
H + 160

X + 4He
B:
1
P + 18O

1
C:
20
D:
1
Ne + 2H
H + 160


n +
18
X
X + 4He
X + 4He
2 In two or three sentences, define the following:
a.
Projection
b.
ray sum
c.
randoms
d.
acquisition angle
e.
coincidence window
f.
blank scan
3.
Pictured below is a sinogram
Label the Y (vertical axis), and describe what it means
Label the X axis, and define what it means
4 You are using a PET Tomograph to acquire images of three point sources. . You place
three point sources containing F-18 on the PET pallet. One point source is in the exact
middle of the detectors, the other two are 10cm away on each side of the middle source.
You acquire a set of projection images.
a.
b.
Draw a graph of the sinogram of the three sources for a 180 degree acquisition
Label the vertical and horizontal axis.
2
5
Ga-68 is a PET radionuclide which has been used in research applications. How much
Ga-68 would you have to start with to have 30mCi at the end of 100 minutes?
T1/2 = 68.3 minutes
6
The sine waves in the diagram below, labeled s1, s2, s3, s4, s5, are added together to
produce the wave at the bottom.
The classic equation for a sine wave is given as: y = A * sin(w*t)
Where: A = amplitude, w = frequency, t = time.
For example, S1 above is expressed as
S2
=
S3
=
S4
=
5 * sin(1 * t)
3 * sin (2 * t)
2 * sin (3 * t)
1 * sin (4 * t)
Based on these data. draw the following graph:
Label the vertical axis Amplitude, label the horizontal axis Frequency.
Plot , on this graph, the amplitude vs. frequency for each of the above equations.
3
This graph is an example of a (fill in the blanks) F_______ T_____________
7.
Identify the anatomical location of three lesions in this image.
8. Go to this site:
http://www.alasbimnjournal.cl/revistas/2/abpetspect.htm
Then describe the biodistribution of FDG.
9.
Describe the principle of a “Time of Flight” PET system.
10. In a Time of Flight system, one photon was detected in 4 nanoseconds, the other in 6
nanoseconds.
a.
b.
How far did each photon travel?
What is the diameter of the detector?
4
11.
What is the average distance traveled before annihilation of the following
radionuclides
Rb-82
_______________________________
N-13
_______________________________
O-15
_______________________________
C-11
_______________________________
F-18
________________________________
12.
Based on your answers, which radionuclide should yield the highest resolution
images? Which should yield the lowest resolution images?
13. The most important application of clinical PET is in (check one):
a. Evaluation of epilepsy
______
b Differentiating benign from malignant lung nodules
______
c. Myocardial viability
______
14.
What does it mean to “filter” an image?
15.
Why is attenuation correction used in PET?
5