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Quiz

Medical Biophysics 3505F Quiz: Lecture 5- Review QuestionsExam


Department
Medical Biophysics
Course Code
MEDBIO 3505F
Professor
Niel Gelman
Study Guide
Quiz

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Review Questions I for MBP3505F (Sept 21, 2017)
1) Consider an NMR signal obtained with 2 Tesla magnetic field from a phantom containing inorganic
phosphate (Pi). If the signal is given by
S(t) = S(0) exp{-(t/T2*)2} exp{-i2S'fpi t}, t t 0
S(t) = 0, t < 0
Suppose that 'fPi is the frequency shift for the Pi signal relative to the PCr frequency and that T2* = 2
ms.
a) Determine the earliest time (t > 0) at which the real part of this signal is equal to zero.
b) What is the value of the imaginary part of this signal relative to S(0) at the earliest time that the
real part is equal to zero? (i.e., at the time calculated in part a)
c) What is the value of the magnitude of the signal, relative to S(0), at t = 3 ms?
2) Suppose you acquire the 1H NMR signal from a phantom containing creatine, choline and an
unkown biochemical (in aqueous solution) in a 3 Tesla magnet. The concentration of creatine is 10
mM.
a) Assume that the unknown biochemical produces a signal component with a single frequency. If the
frequency of the signal from the unknown is 100 Hz higher than that of Creatine, what is the value
of the chemical shift for this unknown.
b) If SCh(0)/SCr(0) = 6, what is the concentration of choline? SCr(0) and SCh(0) are the signal
amplitudes at t = 0 for the CH3 protons in creatine and choline, respectively.
3) Suppose that you place three small water filled containers in the magnet of an NMR system. The
volume of water in each container is the same. One container is placed at the center of the magnet
where the magnetic field strength is exactly equal to B0. The 2nd and 3rd containers are placed at
locations where the magnetic field strengths are exactly equal to B0 + 10 PT and B0 - 10 PT (where
1 PT = 10-6 Tesla). Determine the time from the start of the NMR signal to the time at which the
signal is equal to zero. Assume that the magnetic field is uniform within each of the containers and
that the three signal components decay at the same rate (i.e, all have the same value of T2*).
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