Physics Basic Test: MCQ Quiz!

Inversion recovery is a technique used to produce heavily T1 weighted images at low field. In this technique, the TE (echo time) parameter controls the amount of T2 decay. To minimize T2 effects and enhance T1 weighting, the TE is usually kept short. Therefore, the statement "When inversion recovery is used to produce predominantly heavily T1 weighted images at low field, the TE controls the amount of T2 decay, so it is usually kept short to minimize T2 effects" is true.

In Fast Spin Echo imaging, the echo data at the time of the effective TE is stored in the center of k-space. This is because the center of k-space contains low spatial frequencies, which are important for image contrast and resolution. Storing the echo data in the center allows for better image quality and reduces artifacts.

Spin echo pulse sequences are a type of magnetic resonance imaging (MRI) technique that involves the use of a 180-degree radiofrequency pulse to reverse the dephasing of spins in the tissue. This results in the generation of a spin echo signal, which is then used to create the MRI image. EPI (Echo Planar Imaging) is a different type of pulse sequence that is not a spin echo sequence. EPI uses a train of RF pulses and rapidly varying gradients to acquire multiple echoes in a single excitation, allowing for fast imaging. Therefore, EPI is not a spin echo pulse sequence.

The statement suggests that as ETL (Extract, Transform, Load) increases, the scan time also increases. However, the correct answer is False. This means that there is no direct relationship between ETL and scan time. Increasing the ETL process does not necessarily result in an increase in scan time. Other factors such as data volume, complexity of transformations, and hardware capabilities can also impact scan time.

The question states that each manufacturer uses different acronyms to distinguish between pulse sequences. It specifically mentions a Siemens scanner, and asks for the acronym used for a fast spin-echo sequence on this scanner. Among the given options, TSE is the only one that matches the description of a fast spin-echo sequence. Therefore, TSE is the correct answer.

The STIR time for fat refers to the time it takes for fat to recover its magnetization after being saturated. In this case, the correct answer is 100-175ms, which means that it takes approximately 100 to 175 milliseconds for fat to recover its magnetization.

The echo spacing can be determined by finding the time difference between consecutive echo samples. In this case, the time differences between the samples are 20ms (80-60) and 20ms (100-80). Since the time differences are consistent, the echo spacing is 20ms.

A Fast (Turbo) Spin Echo MRI sequence utilizes multiple 180-degree refocusing pulses. This sequence is designed to reduce the scanning time by acquiring multiple echoes in a single repetition time (TR). It is called "fast" because it allows for faster imaging compared to traditional spin echo sequences. The term "turbo" refers to the use of an echo train, where multiple echoes are acquired in rapid succession, further reducing the scan time. Therefore, the correct answer is Fast (Turbo) Spin Echo.

A pulse sequence in MRI refers to a specific combination and timing of excitation and gradient pulses that are used to disturb and manipulate the nuclear magnetic vector (NMV) orientation. This sequence determines the contrast, resolution, and other imaging characteristics of the MRI scan. It includes the excitation pulse that tips the NMV into the transverse plane, gradient pulses that encode spatial information, and other pulses for signal acquisition and manipulation. The pulse sequence is a crucial component of MRI imaging and different sequences are used for different types of imaging and clinical applications.

For an SS-FSE sequence, half of the K space lines are acquired. This means that only half of the spatial frequency information is collected during the acquisition. The SS-FSE sequence is a fast spin echo sequence that uses a reduced number of echoes to speed up the imaging process. By acquiring only half of the K space lines, the sequence can be completed faster while still providing sufficient image quality.

The scan time can be calculated by multiplying the TR (4000ms) by the number of averages (1 NSA) and the number of echoes (16 ETL). The product is then divided by 60 to convert it to minutes. Therefore, the scan time is 1.07 minutes.

Increasing the ETL (Echo Train Length) in MRI imaging does not directly increase the number of slices per TR (Repetition Time). The number of slices per TR is determined by the slice thickness and the TR itself. The ETL refers to the number of echoes acquired during each TR and is related to the image contrast and signal-to-noise ratio. Increasing the ETL may improve image quality but it does not affect the number of slices acquired per TR. Therefore, the statement is false.

Driven Equilibrium is a technique used in MRI imaging to increase the signal intensity in fluid-based structures. By using a combination of RF pulses and gradients, the technique manipulates the magnetization of the fluid molecules, resulting in a higher signal intensity. This allows for better visualization and characterization of fluid-filled structures in the body, such as blood vessels or cerebrospinal fluid. The advantage of using Driven Equilibrium is therefore an increase in signal intensity in fluid-based structures.

The statement is false because the inversion time is the time between the inversion RF pulse and the imaging sequence, not the 180o rephasing pulse. The 180o rephasing pulse is used to restore the magnetization to its original longitudinal direction before the imaging sequence begins. Therefore, the inversion time does not include the time between the inversion RF pulse and the 180o rephasing pulse.

Driven Equilibrium is a technique used in Fast Spin Echo where a reverse flip angle is applied at the end of the echo train. This reverse flip angle helps to push any remaining transverse magnetization back into the longitudinal plane. By doing so, it helps to reduce the residual transverse magnetization and improve the contrast in the resulting image.