Magnetic Resonance Imaging (MRI) Practice Test

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Calculate the effective TR for a patient with a heart rate of 70 bpm.

600 ms
800 ms
857 ms
900 ms

The correct answer is: 857 ms

To determine the effective repetition time (TR) in a cardiac MRI setting, it is important to understand the relationship between heart rate and the time intervals in which the heart beats. The effective TR is calculated by recognizing that the heart rate directly influences the time interval between each heartbeat. A heart rate of 70 beats per minute (bpm) means the heart is completing 70 cycles in a minute. To find the time for each cycle, you can use the formula: Time per beat (in seconds) = 60 seconds / heart rate (in beats per minute) So, for 70 bpm: Time per beat = 60 / 70 = approximately 0.857 seconds. To convert this time into milliseconds, it is multiplied by 1000: 0.857 seconds x 1000 = 857 milliseconds. Thus, the effective TR is calculated to be 857 milliseconds, which aligns with the correct answer choice. This value is crucial for setting pulse sequences in cardiac MRI, as it ensures that imaging captures the heart at an optimal phase in its cycle, thereby enhancing image quality and diagnostic usefulness.