Magnetic Resonance Imaging (MRI) Practice Test

What imaging parameter might the operator adjust when performing a PCA MRA sequence on a geriatric patient?

1. VENC

2. RF coils

3. Gauss

4. Shimming

The correct answer is: VENC

When performing a PCA (Posterior Cerebral Artery) MRA (Magnetic Resonance Angiography) sequence, the operator may adjust the VENC, or velocity encoding, to optimize the imaging parameters for the patient being scanned. In the context of geriatric patients, who may have variations in blood flow dynamics or reduced cardiac output, properly setting the VENC is crucial. This adjustment helps to accurately capture the velocities of the blood flow in the arteries, which is particularly important for detecting vascular conditions or abnormalities. If the VENC is set too low, slower flow velocities may not be adequately represented, leading to potential missed diagnoses. Conversely, if set too high, there may be a loss of signal from faster flows, which can also obscure important information. Other options such as RF coils, Gauss, and shimming serve different purposes. RF coils are selected based on the area being imaged and are typically not adjusted per individual patient. Gauss refers to the unit of measurement for magnetic field strength and is a fixed characteristic of the MRI machine. Shimming is aimed at improving uniformity of magnetic field and is generally set during the initial calibration of the MRI system and is less frequently adjusted for individual patients. Hence, adjusting the