Abstract
In this thesis, the value of various MRI techniques was addressed in patients with nonpalpable breast lesions. Both studies with an emphasis on the clinical – epidemiological aspects of MRI of the breast (chapters 2, 3, 6) and studies that focused primarily on the physics – technical aspects (chapters 4,
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5, 7) were performed. In a diagnostic meta-analysis (chapter 2), we found an overall sensitivity of dynamic contrast-enhanced Breast MRI of 0.90 (95% CI 0.88 – 0.92) and an overall specificity of 0.72 (95% CI 0.67 – 0.77) using the bivariate analysis apporach for diagnostic meta-analyses. The specificity varied more across the individual studies than the sensitivity did. In chapter 3, the rationale, objectives and study design of the MONET - study (MR mammography Of Nonpalpable BrEast Tumors) were described. The purpose of this randomized study is to evaluate whether performing dynamic contrast-enhanced Breast MRI in addition to mammography in patients with nonpalpable suspicious breast lesions will improve breast cancer management. The results of the MONET – study are expected to be available medio 2010. The influence of the choice of b-values on the ADC of suspicious breast lesions in quantitative DWI of the breast was assessed in chapter 4. The magnitude of the ADC value varied with the choice of different b-values. However, the diagnostic performance was not affected by the choice of the b-values. These results imply, that to differentiate benign from malignant breast lesions, the choice of the b-values is not relevant. However, when the absolute ADC value of a lesion would be compared to reported ADC threshold values in literature, the b-values should be taken into account. In our computer simulations and phantom experiments, we found that in the simple situation of a single hypointensity or calcification against a homogeneous background, the hypointensity or calcification could be visualized on MR images with both a negative and a positive contrast by applying a projection dephaser in the slice select direction (chapter 5). If these results could be extrapolated to the clinical situation of a patient with microcalcifications in the breast, a challenging diagnostic problem could potentially be overcome. The results described in chapter 6 show that MRI-guided 14-gauge core-needle biopsy at 3T is a safe and effective method for breast biopsy in lesions that are occult on mammography and ultrasound. The 9.5 mm susceptibility artifact caused by the biopsy needle did not hamper the procedure. In case of a benign biopsy result, 6 month follow-up Breast MRI should be performed. The performance of proton resonance frequency shift (PRFS) – based MR thermometry in clinical practise can be hampered by local magnetic field disturbances in the breast due to respiration and cardiac motion. We found these field disturbances in the breast to amount to approximately 0.13 ppm due to regular respiration and 0.16 ppm due to maximum capacity respiration and due to cardiac motion
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