Which parameters are standard for a PD weighted axial knee spin echo sequence?

The correct choice for parameters standard for a PD (Proton Density) weighted axial knee spin echo sequence is characterized by using a short echo time (TE) and a longer repetition time (TR). This is because a shorter TE helps to enhance the signal from the protons in the tissues, particularly highlighting fatty tissues and cartilage, which are important for visualizing the knee anatomy in a PD-weighted sequence.

In this case, a TE of 23ms is considered short enough to effectively demonstrate the differences in signal intensity from various tissues, while the TR of 2000ms provides sufficient time for full relaxation of protons, ensuring an optimal signal is captured.

In the context of MRI, PD-weighted sequences rely on adequately sampling the signal from proton-rich tissues while minimizing T1 and T2 effects that can obscure fine details. The chosen parameters in this option balance these factors effectively, making it suitable for assessing knee pathologies such as cartilage injuries or meniscus tears.

Other choices may not adequately represent the required parameters for obtaining a clear PD-weighted image of the knee. For example, options with longer TE values risk increased signal loss from T2 decay, while those with very short TR values may not provide enough time for adequate relaxation, diminishing