Contrast-enhanced MRI of the breast: accuracy, value, controversies, solutions

Abstract

Objective: Contrast-enhanced MRI of the breast has been one of the most controversial areas of MRI. Even though most investigators have, in selected indications, been able to improve accuracy by the additional use of contrast-enhanced MRI, its abuse has been feared not only because of increased costs for imaging, but also because of increased biopsy rates caused by false positive calls and because of errors caused by insufficient standardisation. In this article an overview is given of the present knowledge about contrast-enhanced MRI of the breast. Factors that influence the accuracy and reproducibility of contrast-enhanced MRI are analysed. Method: Factors that influence accuracy include: (1) technical factors that influence accuracy, e.g. slice thickness (partial volume effect), motion reduction, reduction of (cardiac) artifacts, dosage of contrast agent, choice of pulse sequence and echotime, and choice of the method for elimination of fat signal. (2) Hormonal factors (timing of the examination with reference to the menstrual cycle, hormonal replacement therapy). They influence accuracy and must be taken into account. (3) Interpretation guidelines-their choice influences sensitivity and specificity mostly inversely and the use of information from conventional imaging appears necessary. (4) Patient selection influences accuracy for statistical and for biological reasons. Results: Based on the present literature and on the experiences gathered in six German universities (> 12 000 examinations) an excellent sensitivity (> 98%) can be achieved for the combination of mammography and MRI. However, specificity strongly varies with the indications. Recommended indications include examination of breasts with impaired evaluation due to severe scarring, after silicon implants and in the dense breast, exclusion of multicentricity and search for primary tumor. Indications under investigation include high risk patients and strictly selected problem cases. Conclusion: If appropriately applied and used for selected indications, contrast-enhanced MRI may allow a significant diagnostic gain. In order to take advantage of the full potentials of contrast-enhanced MRI the development of commercially available biopsy coils is essential.