Mastering Image Contrast in Medical Imaging

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?

Flip angle (FA)
Echo time (TE)
Turbo-factor or echo train length (ETL/TF)
Repetition time (TR) (correct)

What is the time between an RF excitation pulse and the collection of the signal called?

Echo time (TE) (correct)
Flip angle (FA)
Turbo-factor or echo train length (ETL/TF)
Repetition time (TR)

Which parameter reflects the strength and timing of the gradients used to generate diffusion-weighted images?

b-value (correct)
Repetition time (TR)
Echo time (TE)
Flip angle (FA)

Which contrast mechanism is a measure of the magnitude of diffusion within tissue?

Apparent diffusion coefficient (ADC) (C) Signup and view all the answers

Which process is responsible for the recovery of longitudinal magnetization?

T1 recovery (C) Signup and view all the answers

What is the process called when the amount of magnetization in the transverse plane gradually decreases?

T2 decay (B) Signup and view all the answers

What are the three mechanisms that obtain contrast in MRI images?

T1 recovery, T2 decay, and proton density (D) Signup and view all the answers

Contrast in an MRI image refers to

The difference in signal strength between high signal areas and low signal areas (D) Signup and view all the answers

What is the purpose of creating contrast in an MRI image?

To distinguish between different structures/tissues/pathologies (B) Signup and view all the answers

Which of the following is NOT a contrast mechanism in MRI?

Scanning pulse sequences (B) Signup and view all the answers

What is the definition of contrast in an MRI image?

The difference in signal strength between high signal areas and low signal areas (D) Signup and view all the answers

Which of the following is NOT a factor affecting image contrast in MRI?

Image resolution (A) Signup and view all the answers

What is the mean of angiography in MRI?

The study of blood vessels using MRI (B) Signup and view all the answers

What is the purpose of contrast agents in MRI?

To enhance the visualization of certain tissues/pathologies (A) Signup and view all the answers

Which of the following is true about T1-weighted images?

They use a short TR and exhibit bright fat and dark fluid. (A) Signup and view all the answers

What does the T1 time of a tissue represent?

The time it takes for 63% of the longitudinal magnetization to recover. (D) Signup and view all the answers

How does the TR affect T1 contrast in an MRI image?

A shorter TR results in stronger T1 weighting. (B) Signup and view all the answers

What is the main cause of dephasing in an MR signal?

Field inhomogeneity. (B) Signup and view all the answers

Why is T2 an image contrast parameter?

Different tissues have different T2 dephasing rates. (A) Signup and view all the answers

What is the most marked difference in T1 recovery rates?

Between fat and pure water. (B) Signup and view all the answers

What is the role of the TR in T1 contrast?

To control the recovery of the magnetic vectors. (A) Signup and view all the answers

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 (D) Signup and view all the answers

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 (B) Signup and view all the answers

Which of the following statements about fat in MRI is true?

Fat returns an intermediate signal (B) Signup and view all the answers

What is the echo time (TE) in MRI?

The time between application of the excitation pulse and collection of the MR signal (C) Signup and view all the answers

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 (D) Signup and view all the answers

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 (B) Signup and view all the answers

What type of image is obtained with a long echo time (TE) in MRI?

T2-weighted image (A) Signup and view all the answers

What does proton density refer to in MRI?

The number of hydrogen nuclei present within a given volume of tissue (C) Signup and view all the answers

What is the purpose of a proton density weighted image in MRI?

To enhance proton density contrast (D) Signup and view all the answers