30 Questions
Which of the following parameters controls the length of a relaxation period after the application of one RF excitation pulse to the beginning of the next?
Repetition time (TR)
What is the time between an RF excitation pulse and the collection of the signal called?
Echo time (TE)
Which parameter reflects the strength and timing of the gradients used to generate diffusion-weighted images?
b-value
Which contrast mechanism is a measure of the magnitude of diffusion within tissue?
Apparent diffusion coefficient (ADC)
Which process is responsible for the recovery of longitudinal magnetization?
T1 recovery
What is the process called when the amount of magnetization in the transverse plane gradually decreases?
T2 decay
What are the three mechanisms that obtain contrast in MRI images?
T1 recovery, T2 decay, and proton density
Contrast in an MRI image refers to
The difference in signal strength between high signal areas and low signal areas
What is the purpose of creating contrast in an MRI image?
To distinguish between different structures/tissues/pathologies
Which of the following is NOT a contrast mechanism in MRI?
Scanning pulse sequences
What is the definition of contrast in an MRI image?
The difference in signal strength between high signal areas and low signal areas
Which of the following is NOT a factor affecting image contrast in MRI?
Image resolution
What is the mean of angiography in MRI?
The study of blood vessels using MRI
What is the purpose of contrast agents in MRI?
To enhance the visualization of certain tissues/pathologies
Which of the following is true about T1-weighted images?
They use a short TR and exhibit bright fat and dark fluid.
What does the T1 time of a tissue represent?
The time it takes for 63% of the longitudinal magnetization to recover.
How does the TR affect T1 contrast in an MRI image?
A shorter TR results in stronger T1 weighting.
What is the main cause of dephasing in an MR signal?
Field inhomogeneity.
Why is T2 an image contrast parameter?
Different tissues have different T2 dephasing rates.
What is the most marked difference in T1 recovery rates?
Between fat and pure water.
What is the role of the TR in T1 contrast?
To control the recovery of the magnetic vectors.
Which of the following is true about T2* decay in water molecules in comparison to solid bone?
T2* decay occurs at a slower rate in water molecules
What is the purpose of waiting for a certain time period after the application of the 90° Pulse before sampling the returning signal in MRI?
To increase the contrast between tissues
Which of the following statements about fat in MRI is true?
Fat returns an intermediate signal
What is the echo time (TE) in MRI?
The time between application of the excitation pulse and collection of the MR signal
What happens to the signal differences between tissues when a short echo time (TE) is used in MRI?
The signal differences between tissues become smaller
What happens to the signal differences between tissues when a long echo time (TE) is used in MRI?
The signal differences between tissues become larger
What type of image is obtained with a long echo time (TE) in MRI?
T2-weighted image
What does proton density refer to in MRI?
The number of hydrogen nuclei present within a given volume of tissue
What is the purpose of a proton density weighted image in MRI?
To enhance proton density contrast
Understanding Contrast in Medical Imaging: Test your knowledge on the factors that contribute to image contrast, such as the different rates of T1 recovery in various tissues. Discover why fat and pure water exhibit the most pronounced contrast in magnetic resonance imaging (MRI).
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