How are benign and malignant lesions differentiated on magnetic resonance mammography (breast MRI)?

Updated: Feb 25, 2019
  • Author: Preeti Gupta, MD, FRCR; Chief Editor: Eugene C Lin, MD  more...
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Answer

Answer

A lesion may contain many different kinetic patterns. The most suspicious pattern within a lesion is usually considered for characterizing it.

These 3 basic curve shapes were described by Kuhl and co-investigators [50] .

In a study to determine the value of using such signal-time measurements with dynamic 2D MRM, Kuhl et al found that lesions with type I enhancement were more likely to be benign than malignant, whereas lesions with a type II or III enhancement curve were more likely to be malignant. The investigators studied 266 lesions. [51] These were subsequently excised, and 101 were proven to be malignant.

The researchers showed that 9% of breast cancers had a type I enhancement curve; 33.6%, type II; and 57.4%, type III. Conversely, 83% of benign lesions had a type I curve; 11.5%, type II; and 5.5%, type III. In this analysis, the sensitivity, specificity, and diagnostic accuracy were 91%, 83%, and 86%, respectively.

Various methods of differentiating benign patterns from malignant patterns of enhancement have been described. [52, 53]

The use of computer-aided detection (automated, pixel-by-pixel, color parametric map analysis of the enhancement rate and intensity) is useful for improving reliability of assessment of the large number of images typically obtained with dynamic breast MRI. [54] This technique can also be used to instantly graph the time-enhancement curve as the cursor is moved across the dataset; this information adds to the diagnostic confidence in assessing the nature of an enhancing area.

(See the image below.)

Typical parametric color mapping software used to Typical parametric color mapping software used to map the rate of contrast enhancement on a series of dynamic images acquired at the same locations over a period of time. By arbitrary convention, red and yellow represents faster and more-intense enhancement, while blue and green represent slower and weaker enhancement.

These maps are arbitrary, but typically, lesions that are strongly and/or rapidly enhancing appear red, whereas slowly or weakly enhancing lesions appear blue or green. Intermediate lesions usually are orange or yellow. These have been developed and commercialized to simplify the analysis of the large amount of image data. [55] These maps are helpful for the rapid evaluation of multiple foci of enhancement.

Even if such a workstation is lacking, all MR consoles have ROI measurement capabilities. The detection of suspicious foci depends, then, on visual analysis, with ROIs placed over each suspect area and the mean signal intensity being read off the screen. These data can be entered into standard software programs, such as spreadsheet programs, for further analysis and charting.


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