Answer of 2 Question - Essay Example

Physics Term Paper. Response to question one. Given the MRI scanner with the operation frequency at 300MKz, the field strength is given by the formula: w= YBo where w is the operation frequency, Y is Young’s modulus, and Bo is the magnetic field strength. The magnetic field strength is, therefore, given by Bo= . Young’s modulus is depended on the beam of protons that is exposed. According to Sheil (28), the exposed proton dose of 9.5nC mm-2 leads to Young’s modulus of 4.254GPa, the magnetic field strength Bo = =0.

7052186TThe Larmor Frequency (V) = Where m is the mass, e is the proton charge, B is the magnetic field applied (Sheil, 23).Hence V = = HzFrom the question the gradient strength is 10m/m and the dimensions of the given slice are -5cm, 0.4cm, and 5cm. The thickness for this slice is given by ∆z = where Gz is the gradient strength, ∆z is the slice thickness, γ is the young modulus, and δf is the offset frequency. Therefore, making the offset frequency to be the subject of the formula we get δf = where δf is the offset frequency (Sheil, 44).

Hence, δf = = HzResponse to question two.From the figure, 7.9 showing out the signal of MRI obtained from fat and water there were two signals that were received. These signals include the signals from water which were at 4.8ppm and the signal from fat which was at 1.5ppm. The signal from water was displayed by a peak that was due to protons in water while that from fat was displayed by a peak due to protons within the fat. In the body of an organism, fat and water are the key components of protons.

The molecules of fat and water contain a number of protons whose molecules is extremely beneficial in MR signal.From the figure, there were two peaks. One peak, which was 4.8ppm, was due to protons in water. Another peak, which was 1.5ppm, was due to protons in fat. These two peaks had different ppm because of a number of reasons. First, the relaxation time (T1) for water takes a longer duration of time compared to that of fat. This was evident in figure 7.10 where the weighted T1 image recorded reduced signals from water.

In addition to this, transverse time of relaxation (T2) of water that was free had a short correlation time compared to that of fat. The decay of T2 is because of the interactions that are magnetic which occur in between the protons that are spinning. It is for this reason that the fat ppm had a shorter peak compared to that of water. Research has shown out that water has a longer time of relaxation since its natural motion frequency is higher compared to the clinically used larmor frequency (Sheil, 10).

Relaxation time involves the time taken by protons to remain either coherent or have a phase rotation. This rotation normally follows a ninety degree radio frequency. Secondly, the nuclei of proton in water and fat in a homogenous field do have resonance frequencies that differ. These frequencies differ because of the nuclei shielding that is different. The signals that were detected had magnitude that relied on the persistence of the signal, longitudinal recovery in signal repetition, and the speed of decay of the transverse magnetic field strength.

The influence of T1 and T2 times of relaxations is, therefore, depended on the values of the delay time of echo and the repetition time of the signals. Protons that are mobile (associated with liquids) bring back an MR signal. On the other hand, solids do have T2s are extremely short; therefore, fail to give out MR signal.Work citedSheil, W. Magnetic Resonance Imaging Scan. London: MCL-T Ltd. 2007. Print