Comparison of Breast MR Imaging with Molecular Breast Imaging in Breast Cancer Screening, Diagnosis, Staging, and Treatment Response Evaluation

Molecular Breast Imaging and Positron Emission Mammography

There is growing interest in application of functional imaging modalities for adjunct breast imaging due to their unique ability to evaluate molecular/pathophysiologic changes, not visible by standard anatomic breast imaging. This has led to increased use of nuclear medicine dedicated breast-specific single photon and coincidence imaging systems for multiple indications, such as supplemental screening, staging of newly diagnosed breast cancer, evaluation of response to neoadjuvant treatment, diagnosis of local disease recurrence in the breast, and problem solving. Studies show that these systems maybe especially useful for specific subsets of patients, not well served by available anatomic breast imaging modalities.

Impact of Tomosynthesis Acquisition on 3D Segmentations of Breast Outline and Adipose/Dense Tissue with AI: A Simulation-Based Study

Digital breast tomosynthesis (DBT) reconstructions introduce out-of-plane artifacts and false-tissue boundaries impacting the dense/adipose and breast outline (convex hull) segmentations. A virtual clinical trial method was proposed to segment both the breast tissues and the breast outline in DBT reconstructions. The DBT images of a representative population were simulated using three acquisition geometries: a left-right scan (conventional, I), a two-directional scan in the shape of a "T" (II), and an extra-wide range (XWR, III) left-right scan at a six-times higher dose than I. The nnU-Net was modified including two losses for segmentation: (1) tissues and (2) breast outline. The impact of loss (1) and the combination of loss (1) and (2) was evaluated using models trained with data simulating geometry I. The impact of the geometry was evaluated using the combined loss (1&2). The loss (1&2) improved the convex hull estimates, resolving 22.2% of the false classification of air voxels. Geometry II was superior to I and III, resolving 99.1% and 96.8% of the false classification of air voxels. Geometry III (Dice = (0.98, 0.94)) was superior to I (0.92, 0.78) and II (0.93, 0.74) for the tissue segmentation (adipose, dense, respectively). Thus, the loss (1&2) provided better segmentation, and geometries T and XWR improved the dense/adipose and breast outline segmentations relative to the conventional scan.

Monte Carlo-derived 99m Tc uptake quantification with commercial planar MBI: Absolute tumor activity

BACKGROUND

Molecular breast imaging (MBI) of 99m Tc-sestamibi is an emerging adjunct qualitative tool in the detection and diagnosis of breast cancer.

PURPOSE

This work outlines the development and performance evaluation of a methodology to absolutely quantify tumor 99m Tc activity uptake using a commercially available dual-headed MBI system by implementing corrections for background, scatter, attenuation, and detector characteristics.

METHODS

A validated Monte Carlo application of a commercial MBI system was used to simulate over 7000 unique acquisitions of spherical and ellipsoidal tumors in breast tissue. Tumor absolute activity was calculated following background, scatter, and attenuation corrections of tumor region of interest counts. The methodology was first optimized using a set of high-uptake spherical tumors, and its accuracy and precision was then assessed in a set of spherical tumors with clinical uptake conditions. Finally, the performance of the activity methodology was evaluated under various bias and uncertainty conditions to better characterize the technique under expected clinical measurement conditions.

RESULTS

In a test set of images with clinically relevant contrast and noise conditions, the mean ± standard deviation relative error in total tumor activity was 0.5% ± 6.5% (n = 2363) under ideal measurement conditions. Allowing for variability in tumor and background contours and in estimated tumor depths, the expected accuracy of the methodology in clinical practice was 0.5% ± 11.1% (n = 2363), with minimal loss of accuracy for ellipsoidal tumors.

CONCLUSIONS

Planar MBI photopeak images acquired with standard-of-care protocols can be used to accurately quantify absolute tumor 99m Tc activity with an accuracy and precision of 0.5% ± 11.1%. The reported precision was based on a comprehensive evaluation of random errors and systematic biases.

Functional tumor diameter measurement with Molecular Breast Imaging: development and clinical application

Purpose:Molecular breast imaging (MBI) is used clinically to visualize the uptake of^99mTc-sestamibi in breast cancers. Here, we use Monte Carlo simulations to develop a methodology to estimate tumor diameter in focal lesions and explore a semi-automatic implementation for clinical data.Methods:A validated Monte Carlo simulation of the GE Discovery NM 750b was used to simulate >75,000 unique spherical/ellipsoidal tumor, normal breast, and image acquisition conditions. Subsets of this data were used to 1) characterize the dependence of the full-width at half-maximum (FWHM) of a tumor profile on tumor, normal breast, and acquisition conditions, 2) develop a methodology to estimate tumor diameters, and 3) quantify the diameter accuracy in a broad range of clinical conditions. Finally, the methodology was implemented in patient images and compared to diameter estimates from physician contours on MBI, mammography, and ultrasound imaging.Results:Tumor profile FWHM was determined be linearly dependent on tumor diameter but independent of other factors such as tumor shape, uptake, and distance from the detector. A linear regression was used to calculate tumor diameter from the FWHM estimated from a background-corrected profile across a tumor extracted from a median-filtered single-detector MBI image, i.e., diameter = 1.2 mm + 1.2 x FWHM, for FWHM ≥ 13 mm. Across a variety of simulated clinical conditions, the mean error of the methodology was 0.2 mm (accuracy), with >50% of cases estimated within 1-pixel width of the truth (precision). In patient images, the semi-automatic methodology provided the longest diameter in 94% (60/64) of cases. The estimated true diameters, for oval lesions with homogeneous uptake, differed by ± 5 mm from physician measurements.Conclusion:This work demonstrates the feasibility of accurately quantifying tumor diameter in clinical MBI, and to our knowledge, is the first to explore its implementation and application in patient data.

Breast imaging: Beyond the detection

Breast cancer is a heterogeneous disease nowadays, including different biological subtypes with a variety of possible treatments, which aim to achieve the best outcome in terms of response to therapy and overall survival. In recent years breast imaging has evolved considerably, and the ultimate goal is to predict these strong phenotypic differences noninvasively. Indeed, breast cancer multiparametric studies can highlight not only qualitative imaging parameters, as the presence/absence of a likely malignant finding, but also quantitative parameters, suggesting clinical-pathological features through the evaluation of imaging biomarkers. A further step has been the introduction of artificial intelligence and in particular radiogenomics, that investigates the relationship between breast cancer imaging characteristics and tumor molecular, genomic and proliferation features. In this review, we discuss the main techniques currently in use for breast imaging, their respective fields of use and their technological and diagnostic innovations.

Supplemental Cancer Screening for Women With Dense Breasts: Guidance for Health Care Professionals

Mammography is the standard for breast cancer screening. The sensitivity of mammography in identifying breast cancer, however, is reduced for women with dense breasts. Thirty-eight states have passed laws requiring that all women be notified of breast tissue density results in their mammogram report. The notification includes a statement that differs by state, encouraging women to discuss supplemental screening options with their health care professionals (HCPs). Several supplemental screening tests are available for women with dense breast tissue, but no established guidelines exist to direct HCPs in their recommendation of preferred supplemental screening test. Tailored screening, which takes into consideration the patient's mammographic breast density and lifetime breast cancer risk, can guide breast cancer screening strategies that are more comprehensive. This review describes the benefits and limitations of the various available supplemental screening tests to guide HCPs and patients in choosing the appropriate breast cancer screening.

Novel Approaches to Screening for Breast Cancer

Screening for breast cancer reduces breast cancer-related mortality and earlier detection facilitates less aggressive treatment. Unfortunately, current screening modalities are imperfect, suffering from limited sensitivity and high false-positive rates. Novel techniques in the field of breast imaging may soon play a role in breast cancer screening: digital breast tomosynthesis, contrast material-enhanced spectral mammography, US (automated three-dimensional breast US, transmission tomography, elastography, optoacoustic imaging), MRI (abbreviated and ultrafast, diffusion-weighted imaging), and molecular breast imaging. Artificial intelligence and radiomics have the potential to further improve screening strategies. Furthermore, nonimaging-based screening tests such as liquid biopsy and breathing tests may transform the screening landscape. © RSNA, 2020 Online supplemental material is available for this article.

Molecular Breast Imaging-guided Percutaneous Biopsy of Breast Lesions: A New Frontier on Breast Intervention

Molecular breast imaging (MBI) is an increasingly recognized nuclear medicine imaging modality to detect breast lesions suspicious for malignancy. Recent advances have allowed the development of tissue sampling of MBI-detected lesions using a single-headed camera (breast-specific gamma imaging system) or a dual-headed camera system (MBI system). In this article, we will review current indications of MBI, differences of the two single- and dual-headed camera systems, the appropriate selection of biopsy equipment, billing considerations, and radiation safety. It will also include practical considerations and guidance on how to integrate MBI and MBI-guided biopsy in the current breast imaging workflow.

Molecular Breast Imaging in Clinical Practice

OBJECTIVE. The purpose of this article is to review clinical uses and image interpretation of molecular breast imaging (MBI) and clarify radiation risks. CONCLUSION. MBI detects additional cancers compared with conventional imaging in women with dense breasts and those with elevated risk of breast cancer. Its role as an imaging biomarker of cancer risk and in assessing neoadjuvant chemotherapy response is growing. Radiation risk is minimal; benefit-to-risk ratio is similar to that of mammography. MBI is low cost, well tolerated, and easily adapted into clinical practice.