Dynamic MRI of the Kidneys

Figure shows the five main dynamic phases of renal enhancement in MR Imaging (note that arterial and venous phases are also existed, however their importance is limited in the evaluation of renal parenchyma).
1. Mask/native phase obtained prior to the contrast injection (unenhanced images).
2. Corticomedullary phase obtained approximately 40 sec after the contrast injection shows brisk enhancement of renal cortex. In comparison, renal medulla remains very low in signal intensity.
3. Nephrographic phase obtained approximately 90-100 sec after the contrast injection reveals uniform enhancement of renal cortex and medulla. Note lack of excretion into renal collecting systems. Nephrographic is the most important phase in order to detect small renal masses (e.g. small renal carcinoma).
4. Early excretory phase obtained approximately 180 sec after the contrast injection shows excretion into renal collecting systems.
5. Late excretory phase obtained approximately 300 sec after the contrast injection reveals renal parenchyma signal intensity to be less intense than that shown in either 3 and 4.

Dynamic MRI of the Kidneys

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