Dynamic MR imaging of breast lesions: correlation with microvessel distribution pattern and histologic characteristics of prognosis.

PURPOSE: To evaluate the association of dynamic enhancement parameters of benign and malignant breast lesions at magnetic resonance (MR) imaging with microvessel distribution and histologic prognostic tumor characteristics. MATERIALS AND METHODS: Regional review board approval and informed consent were obtained. Surgical resection specimens of breast lesions (32 benign, 86 malignant) in 118 patients (age range, 28-86 years; mean, 58 years) who had undergone dynamic T1-weighted MR imaging of both breasts were included in the study. Different MR enhancement parameters and microvessel density (MVD) distribution were determined. In malignant lesions, TNM stage, tumor grade, proliferative activity, and hormone receptor expression were determined. Spearman correlation coefficients; Wilcoxon, Fisher exact, Kruskal Wallis, and chi(2) tests; and logistic regression analysis were used for evaluation. RESULTS: Malignant lesions exhibited a higher ratio of microvessels in tumor periphery versus tumor center than did benign lesions (P < .0005). High vessel ratios (P = .001) and low central vessel numbers (P = .007) were associated with high tumor grade. In malignant lesions, initial enhancement ratios of periphery to center of lesion correlated with the corresponding microvessel ratios (r = 0.61). Yet, a high peripheral MVD was not associated with strong peripheral enhancement (r = -0.09). High enhancement ratios, washout rates, and early enhancement peaks were associated with unfavorable, albeit not significant, prognostic indicators. Visible rim enhancement was the most accurate prognostic enhancement criterion for estrogen receptor status (P = .007), tumor grade (P = .06), and lymph node status (P = .046). Washout was the best discriminating criterion for proliferative activity. CONCLUSION: The different enhancement behaviors of malignant and benign breast lesions cannot be explained by MVD alone; however, a low MVD in the center of carcinoma is reflected quantitatively by a high enhancement ratio and qualitatively by rim enhancement, with an implication of adverse prognosis.

Assessment of left ventricular function by breath-hold cine MR imaging: Comparison of different steady-state free precession sequences.

PURPOSE: To compare steady-state free precession (SSFP) sequence protocols with different acquisition times (TA) and temporal resolutions (tRes) due to the implementation of a view sharing technique called shared phases for the assessment of left ventricular (LV) function by breath-hold cine magnetic resonance (MR) imaging. MATERIALS AND METHODS: End-diastolic and end-systolic volumes (EDV, ESV) were measured in contiguous short-axis slices with a thickness of 8 mm acquired in 10 healthy male volunteers. The following true fast imaging with steady-state precession (TrueFISP) sequence protocols were compared: protocol A) internal standard of reference, segmented: tRes 34.5 msec, TA 18 beats per slice; protocol B) segmented, shared phases: tRes 34.1 msec, TA 10 beats per slice; and protocol C) real-time, shared phases, parallel acquisition technique: tRes 47.3 msec, TA 24 beats for 12 slices covering the entire left ventricle. RESULTS: Phase sharing leads to a significant decrease in EDV, stroke volume (SV), and ejection fraction (EF) (median difference -7.0 mL [*], -9.6 mL, and -3.4%, respectively, for protocol B; -15.3 mL, -13.3 mL, and -2.4% for protocol C; P = 0.002, *P = 0.021). The observed median difference of real-time EDV and SV estimates is of clinical relevance. Real-time cine MR imaging shows a greater variability of EDV and SV. No relevant differences in ESV were observed. CONCLUSION: The true cine frame duration of both shared phases sequence protocols exceeds the period of isovolumetric contraction (IVCT) of the left ventricle resulting in a systematic and significant underestimation of EDV and consequently SV and EF. SSFP sequence protocol parameters, particularly tRes and use of view sharing techniques, should therefore be known at follow-up examinations in order to be able to assess LV remodeling in patients with heart failure.

Combination of low and high resolution sequences in two orientations for dynamic contrast-enhanced MRI of the breast: more than a compromise.

The purpose was to combine T1-weighted 3D gradient echo sequences at low and high spatial resolution (and short and longer acquisition time, respectively) in two orientations without compromising signal/time curve analysis and to evaluate the incremental value of assessing architectural features in high resolution images in dynamic contrast-enhanced MR mammography. T1-weighted 3D-FLASH sequences in a 1.5-T scanner (512 x 256 pixel matrix at high resolution; 256 x 128 pixels at low resolution sequences, 72 slices, 1.7-mm slice thickness, TR 8.8 ms, TE 4.5 ms, flip angle 25 degrees) were acquired in a special order during a single investigation. Three observers evaluated architectural features of 36 histopathologically proven lesions using high or low resolution images independently. Architectural features of each lesion were assessed by rating on two three-point scales. Kappa statistics verified the decrease of inter-observer variability. All observers improved assessment of architectural features regarding high resolution images in transversal and coronal orientation (observer A: eight positive, three negative corrections; B: 12/5; C: 16/4). Most positive corrections resulted from improved detection of morphologic criteria of malignancy. Mean inter-observer agreement significantly (P<0.05) increased from "slight" to "moderate" (mean weighted kappa increased from 0.185 to 0.422). This protocol at the charge of slightly enlarged time for measurement offers an elegant way to improve analysis of architectural features in MRM.