Differential diagnosis of mammographically and clinically occult breast lesions on diffusion-weighted MRI.

PURPOSE: To investigate the diagnostic performance of diffusion-weighted imaging (DWI) for mammographically and clinically occult breast lesions. MATERIALS AND METHODS: The study included 91 women with 118 breast lesions (91 benign, 12 ductal carcinoma in situ [DCIS], 15 invasive carcinoma) initially detected on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and assigned BI-RADS category 3, 4, or 5. DWI was acquired with b = 0 and 600 s/mm(2). Lesion visibility was assessed on DWI. Apparent diffusion coefficient (ADC) values were compared between malignancies, benign lesions, and normal (no abnormal enhancement on DCE-MRI) breast tissue, and the diagnostic performance of DWI was assessed based on ADC thresholding. RESULTS: Twenty-four of 27 (89%) malignant and 74/91 (81%) benign lesions were hyperintense on the b = 600 s/mm(2) diffusion-weighted images. Both DCIS (1.33 +/- 0.19 x 10(-3) mm(2)/s) and invasive carcinomas (1.30 +/- 0.27 x 10(-3)mm(2)/s) were lower in ADC than benign lesions (1.71 +/- 0.43 x 10(-3)mm(2)/s; P < 0.001), and each lesion type was lower in ADC than normal tissue (1.90 +/- 0.38 x 10(-3)mm(2)/s, P

Diffusion tensor MRI: preliminary anisotropy measures and mapping of breast tumors.

PURPOSE: To investigate whether diffusion tensor imaging (DTI) measures of anisotropy in breast tumors are different from normal breast tissue and can improve the discrimination between benign and malignant lesions. MATERIALS AND METHODS: The study included 81 women with 105 breast lesions (76 malignant, 29 benign). DTI was performed during breast MRI examinations, and fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were measured for breast lesions and normal tissue in each subject. FA and ADC were compared between cancers, benign lesions, and normal tissue by univariate and multivariate analyses. RESULTS: The FA of carcinomas (mean +/- SD: 0.24 +/- 0.07) was significantly lower than normal breast tissue in the same subjects (0.29 +/- 0.07; P < 0.0001). Multiple logistic regression showed that FA and ADC were each independent discriminators of malignancy (P < 0.0001), and that FA improved discrimination between cancer and normal tissue over ADC alone. However, there was no difference in FA between malignant and benign lesions (P = 0.98). CONCLUSION: Diffusion anisotropy is significantly lower in breast cancers than normal tissue, which may reflect alterations in tissue organization. Our preliminary results suggest that FA adds incremental value over ADC alone for discriminating malignant from normal tissue but does not help with distinguishing benign from malignant lesions.

Diffusion tensor magnetic resonance imaging of the normal breast.

PURPOSE: The objective of this study was to evaluate diffusion anisotropy of the breast parenchyma and assess the range and repeatability of diffusion tensor imaging (DTI) parameters in normal breast tissue. MATERIALS AND METHODS: The study was approved by our institutional review board and included 12 healthy females (median age, 36 years). Diffusion tensor imaging was performed at 1.5 T using a diffusion-weighted echo planar imaging sequence. Diffusion tensor imaging parameters including tensor eigenvalues (lambda(1), lambda(2), lambda(3)), fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured for anterior, central and posterior breast regions. RESULTS: Mean normal breast DTI measures were lambda(1)=2.51 x 10(-3) mm(2)/s, lambda(2)=1.89 x 10(-3) mm(2)/s, lambda(3)=1.39 x 10(-3) mm(2)/s, ADC=1.95+/-0.24 x 10(-3) mm(2)/s and FA=0.29+/-0.05 for b=600 s/mm(2). Significant regional differences were observed for both FA and ADC (P<.05), with higher ADC in the central breast and higher FA in the posterior breast. Comparison of DTI values calculated using b=0, 600 s/mm(2) vs. b=0, 1000 s/mm(2), showed significant differences in ADC (P<.001), but not FA. Repeatability assessment produced within-subject coefficient of variations of 4.5% for ADC and 11.4% for FA measures. CONCLUSION: This study demonstrates anisotropy of water diffusion in normal breast tissue and establishes a normative range of breast FA values. Attention to the influence of breast region and b value on breast DTI measurements may be important for clinical interpretation and standardization of techniques.

Quantitative diffusion-weighted imaging as an adjunct to conventional breast MRI for improved positive predictive value.

OBJECTIVE: The purpose of our study was to investigate whether adding diffusion-weighted imaging (DWI) to dynamic contrast-enhanced MRI (DCE-MRI) could improve the positive predictive value (PPV) of breast MRI. MATERIALS AND METHODS: The retrospective study included 70 women with 83 suspicious breast lesions on DCE-MRI (BI-RADS 4 or 5) who underwent subsequent biopsy. DWI was acquired during clinical breast MRI using b = 0 and 600 s/mm(2). Apparent diffusion coefficient (ADC) values were compared for benign and malignant lesions. PPV was calculated for DCE-MRI alone (based on biopsy recommendations) and DCE-MRI plus DWI (adding an ADC threshold) for the same set of lesions. Results were further compared by lesion type (mass, nonmasslike enhancement) and size. RESULTS: Of the 83 suspicious lesions, 52 were benign and 31 were malignant (11 ductal carcinoma in situ [DCIS], 20 invasive carcinoma). Both DCIS (mean ADC, 1.31 +/- 0.24 x 10(-3) mm(2)/s) and invasive carcinoma (mean ADC, 1.29 +/- 0.29 x 10(-3) mm(2)/s) exhibited lower mean ADC than benign lesions (1.70 +/- 0.44 x 10(-3) mm(2)/s, p < 0.001). Applying an ADC threshold of 1.81 x 10(-3) mm(2)/s for 100% sensitivity produced a PPV of 47% versus 37% for DCE-MRI alone, which would have avoided biopsy for 33% (17/52) of benign lesions without missing any cancers. DWI increased PPV similarly for masses and nonmasslike enhancement and preferentially improved PPV for smaller (< or = 1 cm) versus larger lesions. CONCLUSION: DWI shows potential for improving the PPV of breast MRI for lesions of varied types and sizes. However, considerable overlap in ADC of benign and malignant lesions necessitates validation of these findings in larger studies.

Metabolic and vascular features of dynamic contrast-enhanced breast magnetic resonance imaging and (15)O-water positron emission tomography blood flow in breast cancer.

RATIONALE AND OBJECTIVES: We sought to (1) describe associations between measures of tumor perfusion by dynamic contrast-enhanced breast magnetic resonance imaging (DCE-MRI), blood flow by (15)O-water positron emission tomography (PET) and metabolism by (18)F-fluorodeoxyglucose ((18)F)-FDG PET and (2) improve our understanding of tumor enhancement on MRI through independent measures of tumor metabolism and blood flow. MATERIALS AND METHODS: We performed a retrospective analysis of the existing PET and MRI databases from the Departments of Nuclear Medicine and Radiology. We identified patients with locally advanced breast cancer who underwent (15)O-water/(18)F-FDG PET within 1 month of clinical DCE-MRI between February 2004 and August 2006. The (15)O-water PET blood flow and (18)F-FDG metabolic rate and tissue transport constant (K(1)) in the primary malignancy were calculated. DCE-MRI peak percent enhancement and peak signal enhancement ratio (SER) were measured for each tumor. Correlations and regression analysis of these variables were performed. RESULTS: Fifteen patients with complete PET and DCE-MRI data were included in the analysis cohort. Peak SER correlated significantly with blood flow (r = 0.73, P = .002) and K(1) (r = 0.76, P = .001). However, peak SER did not correlate significantly with FDG metabolic rate (r = 0.44, P = .101). There were no significant correlations between peak percent enhancement and any of the PET parameters. CONCLUSIONS: Our findings suggest that tumor perfusion, represented by (15)O-water PET blood flow, is an important factor in the MRI enhancement of locally advanced breast cancer. A lack of correlation of FDG metabolic rate with blood flow and DCE-MRI kinetics suggests that (18)F-FDG PET provides complementary metabolic information independent of vascular factors.

Dynamic contrast-enhanced magnetic resonance imaging of tumor-induced lymph flow.

The growth of metastatic tumors in mice can result in markedly increased lymph flow through tumor-draining lymph nodes (LNs), which is associated with LN lymphangiogenesis. A dynamic magnetic resonance imaging (MRI) assay was developed, which uses low-molecular weight gadolinium contrast agent to label the lymphatic drainage, to visualize and quantify tumor-draining lymph flow in vivo in mice bearing metastatic melanomas. Tumor-bearing mice showed greatly increased lymph flow into and through draining LNs and into the bloodstream. Quantitative analysis established that both the amount and the rate of lymph flow through draining LNs are significantly increased in melanoma-bearing mice. In addition, the rate of appearance of contrast media in the bloodstream was significantly increased in mice bearing melanomas. These results indicate that gadolinium-based contrast-enhanced MRI provides a noninvasive assay for high-resolution spatial identification and mapping of lymphatic drainage and for dynamic measurement of changes in lymph flow associated with cancer or lymphatic dysfunction in mice. Low-molecular weight gadolinium contrast is already used for 1.5-T MRI scanning in humans, which should facilitate translation of this imaging assay.