Magnetic Resonance Imaging (MRI) Practice Test

Which of the following techniques enhances T1-weighted imaging compared to T2-weighted imaging?

1. Long echo time

2. Short echo time

3. High proton density

4. High flip angle

The correct answer is: High flip angle

The enhancement of T1-weighted imaging compared to T2-weighted imaging is significantly influenced by the use of a high flip angle. T1-weighted imaging emphasizes contrasts that arise from differences in tissue relaxation times, particularly T1 recovery. A high flip angle increases the amount of longitudinal magnetization that is available for detection, thereby enhancing the signal from fat and water in tissues where T1 is relatively long. Using a high flip angle can also help saturate more of the T2 components through a process called nonsaturation, which effectively emphasizes T1 differences. This results in greater contrast between tissues that have differing T1 values, allowing for a more pronounced distinction in the imagery compared to T2-weighted sequences, which tend to highlight differences in T2 decay times instead. In contrast, a long echo time would generally favor T2 weighting, while a short echo time generally improves signal but does not specifically enhance T1 contrast. High proton density may improve image brightness overall but does not directly enhance T1-weighted imaging specifically. Therefore, the application of a high flip angle is vital for achieving improved T1-weighted imaging characteristics.