Feasibility of high spatiotemporal resolution for an abbreviated 3D radial breast MRI protocol

New Approaches and Recommendations for Risk-Adapted Breast Cancer Screening

Population-based breast cancer screening using mammography as the gold standard imaging modality has been in clinical practice for over 40 years. However, the limitations of mammography in terms of sensitivity and high false-positive rates, particularly in high-risk women, challenge the indiscriminate nature of population-based screening. Additionally, in light of expanding research on new breast cancer risk factors, there is a growing consensus that breast cancer screening should move toward a risk-adapted approach. Recent advancements in breast imaging technology, including contrast material-enhanced mammography (CEM), ultrasound (US) (automated-breast US, Doppler, elastography US), and especially magnetic resonance imaging (MRI) (abbreviated, ultrafast, and contrast-agent free), may provide new opportunities for risk-adapted personalized screening strategies. Moreover, the integration of artificial intelligence and radiomics techniques has the potential to enhance the performance of risk-adapted screening. This review article summarizes the current evidence and challenges in breast cancer screening and highlights potential future perspectives for various imaging techniques in a risk-adapted breast cancer screening approach. EVIDENCE LEVEL: 1. TECHNICAL EFFICACY: Stage 5.

Abbreviated Breast MRI: Our Two-Year Initial Experience

OBJECTIVE

The aim of this study was to retrospectively evaluate and present our two-year experience with abbreviated breast MRI at our academic institution as a screening tool to identify primary breast cancers.

METHODS

Employing eight specialty trained breast radiologists, studies were interpreted using the BI-RADS MRI lexicon in this IRB-approved retrospective study. The protocol utilized T1-weighted, fat-saturated, pre- and post-contrast, short  T1 inversion recovery images, and was completed within 10 minutes. Abbreviated breast MRI was offered to asymptomatic women of all breast densities, whose ages ranged from 24 to 90 years. Statistical analysis was performed for comparative data utilizing estimated odds ratios.

RESULTS

Of 1338 patients that met inclusion criteria, 83% (1111/1338) were BI-RADS 1 or 2, 9.0% (121/1338) were BI-RADS 3, and 8% (106/1338) were categorized as either BI-RADS 4 or 5 with recommended biopsy. Biopsy of BI-RADS 4 and 5 categorized patients yielded 15 cancers for a positive predictive value (PPV) 2 of 14.2% and a PPV3 of 18.5%, with 76% (81/106) of patients undergoing the recommended biopsy. An additional cancer was detected in a BI-RADS 3 finding. All cancers detected were in women with heterogeneously dense or extremely dense breasts. Therefore, 16 cancers were detected, yielding a cancer detection rate of 12.0 per 1000. Over the next 12 to 24 months, no interval cancers were detected.

CONCLUSION

Abbreviated breast MRI demonstrates a higher cancer detection rate compared with mammography only and may provide a supplemental screening method to detect breast cancers in patients with varying risk factors.

An Anthropomorphic Digital Reference Object (DRO) for Simulation and Analysis of Breast DCE MRI Techniques

Advances in accelerated magnetic resonance imaging (MRI) continue to push the bounds on achievable spatial and temporal resolution while maintaining a clinically acceptable image quality. Validation tools, including numerical simulations, are needed to characterize the repeatability and reproducibility of such methods for use in quantitative imaging applications. We describe the development of a simulation framework for analyzing and optimizing accelerated MRI acquisition and reconstruction techniques used in dynamic contrast enhanced (DCE) breast imaging. The simulation framework, in the form of a digital reference object (DRO), consists of four modules that control different aspects of the simulation, including the appearance and physiological behavior of the breast tissue as well as the MRI acquisition settings, to produce simulated k-space data for a DCE breast exam. The DRO design and functionality are described along with simulation examples provided to show potential applications of the DRO. The included simulation results demonstrate the ability of the DRO to simulate a variety of effects including the creation of simulated lesions, tissue enhancement modeled by the generalized kinetic model, T1-relaxation, fat signal precession and saturation, acquisition SNR, and changes in temporal resolution.

3D MR fingerprinting using Seiffert spirals

PURPOSE

Seiffert spirals were recently explored as an efficient way to traverse 3D k-space compared to traditional 3D techniques. Several studies have shown the ability of 3D MR fingerprinting (MRF) techniques to acquire T₁ and T₂ relaxation maps in a short period of time. However, these sequences do not sample across a large region of 3D k-space every TR, especially in the way that Seiffert trajectories can.

METHODS

A 3D MRF sequence was designed using 8 Seiffert spirals rotated in 3D k-space, with flip angle modulation for T₁ and T₂ sensitivity. The sequence was compared to an MRF sequence using a 2D spiral rotated in 3D k-space using the tiny golden angle acquisition with similar resolution/readout duration. Both sequences were evaluated using simulations, phantom validation, and in vivo imaging.

RESULTS

In all experiments, the Seiffert spiral MRF sequence performed similar to if not better than the multi-axis 2D spiral MRF sequence. Strong intraclass correlation coefficients (> 0.9) were found between conventional and MRF sequences in phantoms, whereas the in vivo results showed slightly less aliasing artifact with the Seiffert trajectory.

CONCLUSION

In this study, Seiffert spirals were used within the MRF framework to acquire high-resolution T₁ and T₂ relaxation time maps in less than 2.5 min. The reduced aliasing artifacts seen with the Seiffert sequence suggests that sampling over 3D k-space evenly each TR can improve quantification or shorten scan times.

Effects of k-space orders on the time-intensity curves in dynamic contrast-enhanced magnetic resonance imaging of the breast based on simulation study

PURPOSE

This study aims to investigate the influence of time-intensity curves (TICs) on the shapes using a dynamic contrast-enhanced magnetic resonance imaging (MRI) study depending on the Cartesian and radial orders for benign and cancerous breast tumors.

METHODS

Based on kinetic curve parameters, the signal intensities of six concentration gradients comprising two benign and four cancer models were used. The study aimed to construct a dynamic simulated image by creating a digital phantom image according to the following steps: (1) creating a simple numerical phantom, (2) setting the signal intensity in the contrast area, (3) creating the k-space in each time phase, (4) extracting data from k-space in each time phase, (5) filling in the k-space and adding data to the k-space assembly, and (6) creating a magnitude image. The TICs of Cartesian (centric and sequential) and radial (full-length [RFL] and half-length [RHL]) orders were created and sigmoid curve fitting was performed to compare these curves. Maximum slope (MS, s^-1), width of the response (WOR, s), and primary signal response (PSR) were then calculated. Phase encode steps were set for 512 and 256.

RESULTS

MS was significantly decreased by radial order in the cancer model. No change was observed in WOR in Cartesian order, whereas RFL and RHL orders increased in the cancer models. PSR increased remarkably in the radial orders of cancer models. The difference in the fill slope in radial orders was remarkable when the TIC was steeper compared with when it was gentle, especially RHL. In WOR, both radial RFL and RHL were well matched except for the one benign model, and the shape of radial TIC was similar to sequential order as compared to centric order in 256 steps.

CONCLUSION

The effects of Cartesian and radial orders on the patterns of TICs in a dynamic contrast-enhanced MRI study of benign and cancerous breast tumors were revealed. Interestingly, the TIC gradient of radial orders became gentler, particularly in the breast cancer MRI.

Assessment of vascular stiffness in the internal carotid artery proximal to the carotid canal in Alzheimer's disease using pulse wave velocity from low rank reconstructed 4D flow MRI

Clinical evidence shows vascular factors may co-occur and complicate the expression of Alzheimer's disease (AD); yet, the pathologic mechanisms and involvement of different compartments of the vascular network are not well understood. Diseases such as arteriosclerosis diminish vascular compliance and will lead to arterial stiffness, a well-established risk factor for cardiovascular morbidity. Arterial stiffness can be assessed using pulse wave velocity (PWV); however, this is usually done from carotid-to-femoral artery ratios. To probe the brain vasculature, intracranial PWV measures would be ideal. In this study, high temporal resolution 4D flow MRI was used to assess transcranial PWV in 160 subjects including AD, mild cognitive impairment (MCI), healthy controls, and healthy subjects with apolipoprotein ɛ4 positivity (APOE4+) and parental history of AD dementia (FH+). High temporal resolution imaging was achieved by high temporal binning of retrospectively gated data using a local-low rank approach. Significantly higher transcranial PWV in AD dementia and MCI subjects was found when compared to old-age-matched controls (AD vs. old-age-matched controls: P <0.001, AD vs. MCI: P = 0.029, MCI vs. old-age-matched controls P = 0.013). Furthermore, vascular changes were found in clinically healthy middle-age adults with APOE4+ and FH+ indicating significantly higher transcranial PWV compared to controls (P <0.001).

Intracranial vascular flow oscillations in Alzheimer's disease from 4D flow MRI

Recent modeling and experimental evidence suggests clearance of soluble metabolites from the brain can be driven by low frequency flow oscillations (LFOs) through the intramural periarterial drainage (IPAD) pathway. This study investigates the use of 4D flow MRI to derive LFOs from arterial and venous measures of blood flow. 3D radial 4D flow MRI data were acquired on a 3.0 T scanner and reconstructed using a low-rank constraint to produce time resolved measurements of blood flow. Physical phantom experiments were performed to validate the time resolved 4D flow against a standard 2D phase contrast (PC) approach. To evaluate the ability of 4D flow to distinguish physiologic flow changes from noise, healthy volunteers were scanned during a breath-hold (BH) maneuver and compared against 2D PC measures. Finally, flow measures were performed in intracranial arteries and veins of 112 participants including subjects diagnosed with Alzheimer's disease (AD) clinical syndrome (n = 23), and healthy controls (n = 89) on whom apolipoprotein ɛ4 positivity (APOE4+) and parental history of AD dementia (FH+) was known. To assess LFOs, flow range, standard deviation, demeaned temporal flow changes, and power spectral density were quantified from the time series. Group differences were assessed using ANOVA followed by Tukey-Kramer method for pairwise comparison for adjusted means (P < 0.05). Significantly lower LFOs as measured from flow variation range and standard deviations were observed in the arteries of AD subjects when compared to age-matched controls (P = 0.005, P = 0.011). Results suggest altered vascular function in AD subjects. 4D flow based spontaneous LFO measures might hold potential for longitudinal studies aimed at predicting cognitive trajectories in AD and study disease mechanisms.

Abbreviated Breast MRI: Road to Clinical Implementation

Breast MRI offers high sensitivity for breast cancer detection, with preferential detection of high-grade invasive cancers when compared to mammography and ultrasound. Despite the clear benefits of breast MRI in cancer screening, its cost, patient tolerance, and low utilization remain key issues. Abbreviated breast MRI, in which only a select number of sequences and postcontrast imaging are acquired, exploits the high sensitivity of breast MRI while reducing table time and reading time to maximize availability, patient tolerance, and accessibility. Worldwide studies of varying patient populations have demonstrated that the comparable diagnostic accuracy of abbreviated breast MRI is comparable to a full diagnostic protocol, highlighting the emerging role of abbreviated MRI screening in patients with an intermediate and high lifetime risk of breast cancer. The purpose of this review is to summarize the background and current literature relating to abbreviated MRI, highlight various protocols utilized in current multicenter clinical trials, describe workflow and clinical implementation issues, and discuss the future of abbreviated protocols, including advanced MRI techniques.

Breast MRI: Is Faster Better?

OBJECTIVE. Fast breast MRI protocols have the same sensitivity as conventional protocols, but their specificity is variable and can be inadequate. An ultrafast sequence provides early enhancement of lesion characteristics that optimize the characterization of the fast protocol, increasing positive predictive values without increasing time. CONCLUSION. These new abbreviated protocols could constitute a viable screening tool both for women at high risk of breast cancer and for those at intermediate risk with high breast density.

Value of an abbreviated protocol of breast magnetic resonance imaging for screening high-risk patients

OBJECTIVE

Value the utility of breast MRI abbreviated protocols for the screening of breast cancer in high-risk patients compared to the full protocol.

METHODS

We performed a retrospective review of 157 breast MRI of 82 high-risk patients practiced in our hospital between January 2011 and January 2017. Clinical, radiological and anatomopathological parameters were analyzed. Reading of the different protocols (MIP, abbreviated and full) was made by an expert radiologist. Subsequent statistical analysis was done.

RESULTS

A total amount of 12 findings classified as BI-RADS 4 and 5 were identified and performed a biopsy, resulting 11 of them to be malignant (91.67%) and 1 benign (8.33%). The malignant wounds included 4 intraductal carcinoma (33.33%) and 7 infiltrating ductal carcinoma (58.33%). All injuries were detected with the three protocols and no significant differences were found between their respective area under the ROC curve (p=0.0650).

CONCLUSIONS

In our study there are no significant differences between the different protocols (MIP, abbreviated and full), which places the abbreviated protocol as a promising tool for breast cancer screening in high-risk patients.

Comparison of Pathologic Response Evaluation Systems After Neoadjuvant Chemotherapy in Breast Cancers: Correlation With Computer-Aided Diagnosis of MRI Features

OBJECTIVE. The objective of our study was to compare pathologic response assessment systems with dynamic contrast-enhanced MRI (DCE-MRI) features and evaluate the predictive performance of DCE-MRI features relative to different pathologic response assessment systems after neoadjuvant chemotherapy (NAC). MATERIALS AND METHODS. This retrospective study included 223 women (mean age, 47.2 years; age range, 31-71 years) who underwent DCE-MRI before and after completing NAC before definitive surgery between January and December 2015. Six MRI features (i.e., tumor size; angio volume; peak enhancement; and persistent, plateau, and washout enhancing components) were measured and correlated with the Miller-Payne grading system, residual cancer burden (RCB) class, and modified in-breast RCB index. Percentage changes in MRI features were correlated with pathologic assessment systems using the Spearman rank correlation test; ROC curves were analyzed to predict pathologic outcomes. RESULTS. All six MRI features correlated most strongly with the in-breast RCB index (r = -0.75 to -0.51, p < 0.001) followed by the Miller-Payne system (r = 0.47-0.72, p < 0.001) and RCB class (r = -0.58 to -0.41, p < 0.001). The in-breast RCB index correlated most strongly with the angio volume reduction rate (r = -0.75, p < 0.001) followed by maximum diameter (r = -0.69, p < 0.001), peak enhancement (r = -0.67, p < 0.001), washout component (r = -0.60, p < 0.001), plateau component (r = -0.59, p < 0.001), and persistent component (r = -0.51, p < 0.001). CONCLUSION. The in-breast RCB index correlated best with changes in DCE-MRI features, and the MRI-measured angio volume reduction rate correlated best with pathologic tumor responses.

Characterization of Sub-1 cm Breast Lesions Using Radiomics Analysis

BACKGROUND

Small breast lesions are difficult to visually categorize due to the inherent lack of morphological and kinetic detail.

PURPOSE

To assess the efficacy of radiomics analysis in discriminating small benign and malignant lesions utilizing model free parameter maps.

STUDY TYPE

Retrospective, single center.

POPULATION

In all, 149 patients, with a total of 165 lesions scored as BI-RADS 4 or 5 on MRI, with an enhancing volume of <0.52 cm³ .

FIELD STRENGTH/SEQUENCE

Higher spatial resolution T₁ -weighted dynamic contrast-enhanced imaging with a temporal resolution of ~90 seconds performed at 3.0T.

ASSESSMENT

Parameter maps reflecting initial enhancement, overall enhancement, area under the enhancement curve, and washout were generated. Heterogeneity measures based on first-order statistics, gray level co-occurrence matrices, run length matrices, size zone matrices, and neighborhood gray tone difference matrices were calculated. Data were split into a training dataset (~75% of cases) and a test dataset (~25% of cases).

STATISTICAL TESTS

Comparison of medians was assessed using the nonparametric Mann-Whitney U-test. The Spearman rank correlation coefficient was utilized to determine significant correlations between individual features. Finally, a support vector machine was employed to build multiparametric predictive models.

RESULTS

Univariate analysis revealed significant differences between benign and malignant lesions for 58/133 calculated features (P < 0.05). Support vector machine analysis resulted in areas under the curve (AUCs) ranging from 0.75-0.81. High negative (>89%) and positive predictive values (>83%) were found for all models.

DATA CONCLUSION

Radiomics analysis of small contrast-enhancing breast lesions is of value. Texture features calculated from later timepoints on the enhancement curve appear to offer limited additional value when compared with features determined from initial enhancement for this patient cohort.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1468-1477.

Abbreviated MRI of the Breast: Does It Provide Value?

MRI of the breast is the most sensitive test for breast cancer detection and outperforms conventional imaging with mammography, digital breast tomosynthesis, or ultrasound. However, the long scan time and relatively high costs limit its widespread use. Hence, it is currently only routinely implemented in the screening of women at an increased risk of breast cancer. To overcome these limitations, abbreviated dynamic contrast‐enhanced (DCE)‐MRI protocols have been introduced that substantially shorten image acquisition and interpretation time while maintaining a high diagnostic accuracy. Efforts to develop abbreviated MRI protocols reflect the increasing scrutiny of the disproportionate contribution of radiology to the rising overall healthcare expenditures. Healthcare policy makers are now focusing on curbing the use of advanced imaging examinations such as MRI while continuing to promote the quality and appropriateness of imaging. An important cornerstone of value‐based healthcare defines value as the patient's outcome over costs. Therefore, the concept of a fast, abbreviated MRI exam is very appealing, given its high diagnostic accuracy coupled with the possibility of a marked reduction in the cost of an MRI examination. Given recent concerns about gadolinium‐based contrast agents, unenhanced MRI techniques such as diffusion‐weighted imaging (DWI) are also being investigated for breast cancer diagnosis. Although further larger prospective studies, standardized imaging protocol, and reproducibility studies are necessary, initial results with abbreviated MRI protocols suggest that it seems feasible to offer screening breast DCE‐MRI to a broader population. This article aims to give an overview of abbreviated and fast breast MRI protocols, their utility for breast cancer detection, and their emerging role in the new value‐based healthcare paradigm that has replaced the fee‐for‐service model.

Level of Evidence: 1

Technical Efficacy: Stage 2

J. Magn. Reson. Imaging 2019;49:e85–e100.