The time-signal intensity curve (TIC) from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) reflects the hemodynamic features of a specific lesion. The TIC is obtained by repeated MRI scans after the injection of contrast agent; a qualified TIC usually takes 12 minutes to complete the scans. Temporal resolution is the main determinant; a higher temporal resolution means a smoother TIC. When a TIC is measured under DCE-MRI, the patient should not move, with a region of interest (ROI) of at least 3 pixels putting on the part of lesion that has fastest enhancement with fastest washout, or, the most worrisome part. No uniform criteria for the interpretation of the kinetic curve have been available. Some authors emphasize the shape of TIC under DCE-MRI, while others are more interested in the enhancement threshold values of malignancy.
The enhancement rate was calculated according to the following enhancement formula:
enhancement rate = [(SI post - SI pre)/SI pre] × 100(%)
Since the signal intensities differ among different scan series, the calculation of enhancement rate should ensure that the pre-scan and dynamic contrast-enhanced scan are conducted within the same series; otherwise, the signal intensities need to be adjusted.
The kinetic curve can be classified into three categories. Early enhancement (2 minutes after agent injection), during which the initial rise of the enhanced curve can be divided into “slow”, “medium”, and “rapid”. An initial peak signal intensity within 90 seconds >90% is defined as rapid enhancement, which is highly suggestive of malignancy. The signal intensity 2 minutes after contrast injection is defined as “delayed phase” (Figure 1), which is divided into “persistent” (type I), “plateau” (type II), and “washout” (type III). Persistent (type 1) - a pattern of progressive enhancement, with continuous increase in signal intensity; plateau (type 2) - the signal intensity reached a peak 2 minutes after contrast medium injection, followed by a flattening during the delayed phase; washout (type 3) - an initial increase and subsequent decrease in signal intensity 2 minutes after contrast medium injection (Figures 2-11). The initial rise usually reflects the scope of tumor angiogenesis, whereas the delayed phase reflects the formation of stromal tumor cells. Generally, a persistent curve is suggestive of benign changes; washout, malignancy; and palteau, either benign change or malignancy. The kinetic curve is especially helpful for the diagnosis and treatment of morphologically benign lesions; for lesions that are morphologically suspected to be malignant, biopsy should be performed regardless of its kinetic curve.
Disclosure: The authors declare no conflict of interest.