Faculty Bibliography

Purpose To demonstrate the feasibility of the use of a rapid, noninvasive, in vivo imaging method to measure fatty acid fractions of breast adipose tissue during diagnostic breast magnetic resonance (MR) examinations and to investigate associations between fatty acid fractions in breast adipose tissue and breast cancer status by using this method. Materials and Methods The institutional review board approved this retrospective HIPAA-compliant study and informed consent was waived. Between July 2013 and September 2014, multiple-echo three-dimensional gradient-echo data were acquired for 89 women. Spectra were generated and used to estimate fractions of monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA), and saturated fatty acid (SFA) in the breast adipose tissue. Analysis of covariance and exact Mann-Whitney tests were used to compare groups and the Spearman rank correlation coefficient was used to characterize the association of each imaging measure with each attribute. Results For postmenopausal women, MUFA was lower (0.38 +/- 0.06 vs 0.46 +/- 0.10; P < .05) and SFA was higher (0.31 +/- 0.07 vs 0.19 +/- 0.11; P < .05) for women with invasive ductal carcinoma than for those with benign tissue. No correlation was found between body mass index (BMI) and fatty acid fractions in breast adipose tissue. In women with benign tissue, postmenopausal women had a higher PUFA (0.35 +/- 0.06 vs 0.27 +/- 0.05; P < .01) and lower SFA (0.19 +/- 0.11 vs 0.30 +/- 0.12; P < .05) than premenopausal women. Conclusion There is a possible link between the presence of invasive ductal carcinoma and fatty acid fractions in breast adipose tissue for postmenopausal women in whom BMI values are not correlated with the fatty acid fractions. (c) RSNA, 2016 Online supplemental material is available for this article.

OBJECTIVE: MRI-guided needle localization allows access to MRI-detected mammographically occult breast lesions that are not amenable to MRI-guided biopsy. The purpose of this study was to examine the safety and outcomes of MRI-guided needle localization. MATERIALS AND METHODS: Ninety-nine consecutive breast lesions that underwent preoperative MRI-guided needle localization were identified. Clinical indications for breast MRI, reasons for performing MRI-guided needle localization, and surgical pathology results were recorded. Lesion characteristics, procedure time, and complications were assessed. RESULTS: Of 99 lesions, 60 (60.6%) were in a location inaccessible for MRI biopsy, necessitating MRI-guided needle localization. Histologic evaluation revealed 38 (38.4%) carcinomas, 31 (31.3%) high-risk lesions, and 30 (30.3%) benign lesions. Carcinoma was more likely to be found in women with known cancer (31/61 [50.8%]; p = 0.003) than in women undergoing imaging for high-risk screening (2/18 [11.1%]) or problem solving (6/20 [30%]). Masses (p = 0.013) and foci (p < 0.001) were more likely to be malignant than were lesions with nonmass enhancement. Foci were significantly more often malignant compared with all other lesion types (9/10 [90%]; p < 0.001). The mean (+/- SD) procedure time was 32.9 +/- 9.39 minutes. All lesions were occult on specimen radiographs. There were no procedure-related complications. CONCLUSION: The positive predictive value of MRI-guided needle localization (38.4%) is comparable to that of mammography- and tomosynthesis-guided localizations and is highest in women with a known diagnosis of cancer. It is highly accurate in targeting small enhancing lesions, thereby improving surgical management. MRI-guided needle localization is a safe, accurate, and time-efficient procedure.

PURPOSE: To examine heterogeneous breast cancer through intravoxel incoherent motion (IVIM) histogram analysis. MATERIALS AND METHODS: This HIPAA-compliant, IRB-approved retrospective study included 62 patients (age 48.44 +/- 11.14 years, 50 malignant lesions and 12 benign) who underwent contrast-enhanced 3 T breast MRI and diffusion-weighted imaging. Apparent diffusion coefficient (ADC) and IVIM biomarkers of tissue diffusivity (Dt), perfusion fraction (fp), and pseudo-diffusivity (Dp) were calculated using voxel-based analysis for the whole lesion volume. Histogram analysis was performed to quantify tumour heterogeneity. Comparisons were made using Mann-Whitney tests between benign/malignant status, histological subtype, and molecular prognostic factor status while Spearman's rank correlation was used to characterize the association between imaging biomarkers and prognostic factor expression. RESULTS: The average values of the ADC and IVIM biomarkers, Dt and fp, showed significant differences between benign and malignant lesions. Additional significant differences were found in the histogram parameters among tumour subtypes and molecular prognostic factor status. IVIM histogram metrics, particularly fp and Dp, showed significant correlation with hormonal factor expression. CONCLUSION: Advanced diffusion imaging biomarkers show relationships with molecular prognostic factors and breast cancer malignancy. This analysis reveals novel diagnostic metrics that may explain some of the observed variability in treatment response among breast cancer patients. KEY POINTS: * Novel IVIM biomarkers characterize heterogeneous breast cancer. * Histogram analysis enables quantification of tumour heterogeneity. * IVIM biomarkers show relationships with breast cancer malignancy and molecular prognostic factors.

RATIONALE AND OBJECTIVES: This study aimed to determine frequency of discordant lesions and discordant false-negative cancers at stereotactic vacuum-assisted biopsy (SVAB). MATERIALS AND METHODS: Institutional database was searched for discordant SVAB results between January 1, 2005 and December 31, 2012, in this retrospective institutional review board-approved Health Insurance Portability and Accountability Act-compliant study. Patient age, indication for initial mammogram, breast density, lesion size, Breast Imaging Reporting and Data System categorization, operator experience, biopsy needle gauge, biopsy histology, and final surgical histology of discordant lesions were collected and entered into a Microsoft Excel spreadsheet. Discordant rate and false-negative rates were calculated. Fisher exact test was used to assess prevalence of discordance using 11-Gauge needles versus 9-Gauge needles. Patient age, lesion Breast Imaging Reporting and Data System, operator days of experience, mammographic density, and lesion size were evaluated for association with false-negative discordant lesions using an exact Mann-Whitney U test. RESULTS: A total of 1861 SVABs were performed, 224 (12%) with an 11-Gauge VAB device and 1637 (88%) with a 9G Suros or Eviva device. Majority (1409 of 1861; 76%) of SVABs targeted calcifications. Twenty-three of 1861 (1.2%) discordant lesions were identified in 23 women. Seven of 23 (30%) discordant lesions were found to be cancers after final surgical pathology. Needle gauge was not associated with discordance. Operator experience was not associated with false-negative discordance. CONCLUSIONS: A relatively low discordance rate (1.2%) was observed. However, a high percentage (30%; range in literature 11.7%-53.8%) of our discordant lesions were false negatives. This study emphasizes the need for careful radiological-pathologic review after SVAB and for repeat biopsy or surgical excision in the setting of discordance.

PURPOSE: This study aims to investigate the feasibility of using simultaneous breast MRI and PET to assess the synergy of MR pharmacokinetic and fluorine-18 fluorodeoxyglucose (F-FDG) uptake data to characterize tumor aggressiveness in terms of metastatic burden and Ki67 status. METHODS: Twelve consecutive patients underwent breast and whole-body PET/MRI. During the MR scan, PET events were simultaneously accumulated. MR contrast kinetic model parametric maps were computed using the extended Tofts model, including the volume transfer constant between blood plasma and the interstitial space (K), the transfer constant from the interstitial space to the blood plasma (kep), and the plasmatic volume fraction (Vp). RESULTS: Patients with systemic metastases had a significantly lower kep compared to those with local disease (0.45 vs. 0.99 min, P = 0.011). Metastatic burden correlated positively with K and standardized uptake value (SUV), and negatively with kep. Ki67 positive tumors had a significantly greater K compared to Ki67 negative tumors (0.29 vs. 0.45 min, P = 0.03). A negative correlation was found between metabolic tumor volume and transfer constant (K or Kep). CONCLUSION: These preliminary results suggest that MR pharmacokinetic parameters and FDG-PET may aid in the assessment of tumor aggressiveness and metastatic potential. Future studies are warranted with a larger cohort to further assess the role of pharmacokinetic modeling in simultaneous PET/MRI imaging.

Quantitative standardized uptake values (SUVs) from fluorine-18 (18F) fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) are commonly used to evaluate the extent of disease and response to treatment in breast cancer patients. Recently, PET/magnetic resonance imaging (MRI) has been shown to qualitatively detect metastases from various primary cancers with similar sensitivity to PET/CT. However, quantitative validation of PET/MRI requires assessing the reliability of SUVs from MR attenuation correction (MRAC) relative to CT attenuation correction (CTAC). The purpose of this retrospective study was to assess the utility of PET/MRI-derived SUVs in breast cancer patients by testing the hypothesis that SUVs derived from MRAC correlate well with those from CTAC. Between August 2012 and May 2013, 35 breast cancer patients (age 37-78 years, 1 man) underwent clinical 18F-FDG PET/CT followed by PET/MRI. One hundred seventy metastases were seen in 21 of 35 patients; metastases to bone in 16 patients, to liver in seven patients, and to nonaxillary lymph nodes in eight patients were sufficient for statistical analysis on an organ-specific per patient basis. SUVs in the most FDG-avid metastasis per organ per patient from PET/CT and PET/MRI were measured and compared using Pearson's correlations. Correlations between CTAC- and MRAC-derived SUVmax and SUVmean in 31 metastases to bone, liver, and nonaxillary lymph nodes were strong overall (rho = 0.80, 0.81). SUVmax and SUVmean correlations were also strong on an organ-specific basis in 16 bone metastases (rho = 0.76, 0.74), seven liver metastases (rho = 0.85, 0.83), and eight nonaxillary lymph node metastases (rho = 0.95, 0.91). These strong organ-specific correlations between SUVs from PET/CT and PET/MRI in breast cancer metastases support the use of SUVs from PET/MRI for quantitation of 18F-FDG activity.

OBJECTIVE: This study evaluates use of an abbreviated magnetic resonance imaging protocol with T2-weighted imaging in detecting biopsy-proven unifocal breast cancer. MATERIALS AND METHODS: This is an institutional review board approved retrospective study of patients with biopsy-proven unifocal breast cancer (88% invasive; 12% in situ) undergoing magnetic resonance imaging. In three separate sessions, three breast imagers evaluated (1) T1-weighted non-contrast, post-contrast and post-contrast subtracted images, (2) T1-weighted images with clinical history and prior imaging, and (3) T1-weighted images and T2-weighted images with clinical history and prior imaging. Protocols were compared for cancer detection, reading time and lesion conspicuity. An independent breast radiologist retrospectively analyzed initial enhancement ratio of cancers and retrospectively reviewed lesion morphology and final pathology. RESULTS: All 107 cancers were identified at first protocol by at least one reader; five cancers were missed by either one or two readers. One cancer was missed by one reader at protocols two and three. Mean percentage detection for protocol one was 97.8%; protocol two, 99.4%, protocol three, 99.4%. T2-weighted images did not alter cancer detection but increased lesion conspicuity for 2/3 readers. 3/5 missed lesions were low grade cancers. Initial enhancement ratio was positively associated with increasing tumor grade (p=0.031) and pathology (p=0.002). Reader interpretation time decreased and lesion conspicuity increased as initial enhancement ratio increased. CONCLUSION: Abbreviated magnetic resonance imaging has high rate of detection for known breast cancer and short interpretation time. T2 weighted imaging increased lesion conspicuity without altering detection rate. Initial enhancement ratio correlated with invasive disease and tumor grade.

RATIONALE AND OBJECTIVES: To investigate whether quantitative kinetic analysis of lesions and background parenchyma in breast magnetic resonance imaging can elucidate differences between BRCA carriers and sporadic controls with high risk for breast cancer. MATERIALS AND METHODS: Fifty-nine BRCA and 59 control cases (49 benign, 10 malignant) were examined in this study. Principal component analysis was applied for quantitative analysis of dynamic signal in background parenchyma (B) and lesion (L) in terms of initial enhancement ratio (IER) and delayed enhancement ratio (DER). RESULTS: Control B-IER, B-DER, L-IER, and L-DER were higher than BRCA cases in all women and in women with benign lesions; statistically significant differences in B-IER and B-DER (all women: P = 0.02 and P = 0.02, respectively; benign only: P = 0.005 and P = 0.005, respectively). In the control cohort, B-IER and B-DER were higher in the premenopausal women than in the postmenopausal women (P = 0.013 and 0.003, respectively), but not in the BRCA cohort; this led to significant differences in B-IER and B-DER between the control and the BRCA groups in the premenopausal women (P = 0.01 and 0.01, respectively) but not in the postmenopausal women. CONCLUSION: Results suggest possible differences in the vascular properties of background parenchyma between BRCA carriers and noncarriers and its association with menopausal status.

BACKGROUND: To evaluate the influence of temporal sparsity regularization and radial undersampling on compressed sensing reconstruction of dynamic contrast-enhanced (DCE) MRI, using the iterative Golden-angle RAdial Sparse Parallel (iGRASP) MRI technique in the setting of breast cancer evaluation. METHODS: DCE-MRI examinations of the breast (n = 7) were conducted using iGRASP at 3 Tesla. Images were reconstructed with five different radial undersampling schemes corresponding to temporal resolutions between 2 and 13.4 s/frame and with four different weights for temporal sparsity regularization (lambda = 0.1, 0.5, 2, and 6 times of noise level). Image similarity to time-averaged reference images was assessed by two breast radiologists and using quantitative metrics. Temporal similarity was measured in terms of wash-in slope and contrast kinetic model parameters. RESULTS: iGRASP images reconstructed with lambda = 2 and 5.1 s/frame had significantly (P < 0.05) higher similarity to time-averaged reference images than the images with other reconstruction parameters (mutual information (MI) >5%), in agreement with the assessment of two breast radiologists. Higher undersampling (temporal resolution < 5.1 s/frame) required stronger temporal sparsity regularization (lambda >/= 2) to remove streaking aliasing artifacts (MI > 23% between lambda = 2 and 0.5). The difference between the kinetic-model transfer rates of benign and malignant groups decreased as temporal resolution decreased (82% between 2 and 13.4 s/frame). CONCLUSION: This study demonstrates objective spatial and temporal similarity measures can be used to assess the influence of sparsity constraint and undersampling in compressed sensing DCE-MRI and also shows that the iGRASP method provides the flexibility of optimizing these reconstruction parameters in the postprocessing stage using the same acquired data. J. Magn. Reson. Imaging 2015.