How much more heating does a 90-degree RF pulse produce compared to a 45-degree RF pulse?

The correct answer is that a 90-degree RF pulse produces four times more heating than a 45-degree RF pulse due to the relationship between the power deposition and the flip angle of the RF pulses in magnetic resonance imaging (MRI).

When RF pulses are applied, the heating effect is related to the amount of energy deposited in the tissue, which is influenced by the angle of the flip. The energy deposition (and consequently heating) is proportional to the sine of the flip angle squared. This means that for a 45-degree pulse, the energy deposition can be represented by ( \sin^2(45^\circ) = (0.707)^2 ), which equals approximately 0.5. For a 90-degree pulse, the energy deposition becomes ( \sin^2(90^\circ) = 1 ).

Thus, the relationship can be established:

• Heating from 45-degree pulse: 0.5 (or half the maximum energy deposition)
• Heating from 90-degree pulse: 1 (maximum energy deposition)

When comparing the two, the energy deposition from the 90-degree pulse is indeed double that of the 45-degree pulse in terms of direct heating. However, when calculating heating in relation to the power input