Molecular Breast Imaging for Screening in Dense Breasts: State of the Art and Future Directions

Updates in Breast Cancer Screening and Diagnosis

OPINION STATEMENT

Breast cancer does not wait until a woman reaches her 50's to strike. One in six cases occurs in women between the ages of 40 and 49 and breast cancer is the most prevalent cancer and the leading cause of cancer-related deaths among women under 50 in the United States (10% of breast cancer deaths), emphasizing the urgency of early detection (American Society. 2024). Duffy et al. highlight the vital role of mammography screening in younger women, showing that starting screening at 40 reduces breast cancer mortality, with a consistent absolute reduction over time (Duffy et al. Health Technol Assess. 24(55):1-24, 2020). By starting yearly mammograms at 40, we could see a remarkable 40% reduction in breast cancer deaths (Monticciolo et al. J Am Coll Radiol. 18(9):1280-8, 2021). Screening at age 40 also adds little to the burden of overdiagnosis that already arises from screening at age 50 and older. Comparing this to biennial screening between ages 50-74, yearly screening at 40 saves approximately 13,770 more lives annually according to a report by the American Cancer Society published in JAMA in 2015 (Oeffinger et al. JAMA. 314(15):1599-614, 2015). But it's not just about saving lives; it's also about preserving quality of life. Between ages 40 and 49, 12-15% of years of life lost are attributed to breast cancer, highlighting the impact on women's lives. Early detection through screening can minimize these losses, ensuring more years spent with loved ones. It's clear: starting mammograms at age 40 saves lives. We must prioritize early detection and make screening accessible to all women, regardless of age. This proactive approach can reduce the burden of breast cancer and pave the way for a healthier future for women everywhere.

Molecular Breast Imaging Biopsy with a Dual-Detector System

Purpose To develop a molecular breast imaging (MBI)-guided biopsy system using dual-detector MBI and to perform initial testing in participants. Materials and Methods The Stereo Navigator MBI Accessory biopsy system comprises a lower detector, upper fenestrated compression paddle, and upper detector. The upper detector retracts, allowing craniocaudal, oblique, or medial or lateral biopsy approaches. The compression paddle allows insertion of a needle guide and needle. Lesion depth is calculated by triangulation of lesion location on the upper detector at 0° and 15° and relative lesion activity on upper and lower detectors. In a prospective study (July 2022-June 2023), participants with Breast Imaging Reporting and Data System category 2, 3, 4, or 5 breast lesions underwent MBI-guided biopsy. After injection of 740 MBq technetium 99m sestamibi, craniocaudal and mediolateral oblique MBI (2-minute acquisition per view) confirmed lesion visualization. A region of interest over the lesion permitted depth calculation in the system software. Upper detector retraction allowed biopsy device placement. Specimen images were obtained on the retracted upper detector, confirming sampling of the target. Results Of 21 participants enrolled (mean age, 50.6 years ± 10.1 [SD]; 21 [100%] women), 17 underwent MBI-guided biopsy with concordant pathology. No lesion was observed at the time of biopsy in four participants. Average lesion size was 17 mm (range, 6-38 mm). Average procedure time, including preprocedure imaging, was 55 minutes ± 13 (range, 38-90 minutes). Pathology results included invasive ductal carcinoma (n = 1), fibroadenoma (n = 4), pseudoangiomatous stromal hyperplasia (n = 6), and fibrocystic changes (n = 6). Conclusion MBI-guided biopsy using a dual-head system with retractable upper detector head was feasible, well tolerated, and efficient. Keywords: Breast Biopsy, Molecular Breast Imaging, Image-guided Biopsy, Molecular Breast Imaging-guided Biopsy, Breast Cancer Clinical trial registration no. NCT06058650 © RSNA, 2024.

Recent advancements in artificial intelligence for breast cancer: Image augmentation, segmentation, diagnosis, and prognosis approaches

Breast cancer is a significant global health burden, with increasing morbidity and mortality worldwide. Early screening and accurate diagnosis are crucial for improving prognosis. Radiographic imaging modalities such as digital mammography (DM), digital breast tomosynthesis (DBT), magnetic resonance imaging (MRI), ultrasound (US), and nuclear medicine techniques, are commonly used for breast cancer assessment. And histopathology (HP) serves as the gold standard for confirming malignancy. Artificial intelligence (AI) technologies show great potential for quantitative representation of medical images to effectively assist in segmentation, diagnosis, and prognosis of breast cancer. In this review, we overview the recent advancements of AI technologies for breast cancer, including 1) improving image quality by data augmentation, 2) fast detection and segmentation of breast lesions and diagnosis of malignancy, 3) biological characterization of the cancer such as staging and subtyping by AI-based classification technologies, 4) prediction of clinical outcomes such as metastasis, treatment response, and survival by integrating multi-omics data. Then, we then summarize large-scale databases available to help train robust, generalizable, and reproducible deep learning models. Furthermore, we conclude the challenges faced by AI in real-world applications, including data curating, model interpretability, and practice regulations. Besides, we expect that clinical implementation of AI will provide important guidance for the patient-tailored management.

Local texture statistics augment the power spectrum in modeling radiographic judgments of breast density

Purpose

Anatomical "noise" is an important limitation of full-field digital mammography. Understanding its impact on clinical judgments is made difficult by the complexity of breast parenchyma, which results in image texture not fully captured by the power spectrum. While the number of possible parameters for characterizing anatomical noise is quite large, a specific set of local texture statistics has been shown to be visually salient, and human sensitivity to these statistics corresponds to their informativeness in natural scenes.

Approach

We evaluate these local texture statistics in addition to standard power-spectral measures to determine whether they have additional explanatory value for radiologists' breast density judgments. We analyzed an image database consisting of 111 disease-free mammographic screening exams (4 views each) acquired at the University of Pittsburgh Medical Center. Each exam had a breast density score assigned by the examining radiologist. Power-spectral descriptors and local image statistics were extracted from images of breast parenchyma. Model-selection criteria and accuracy were used to assess the explanatory and predictive value of local image statistics for breast density judgments.

Results

The model selection criteria show that adding local texture statistics to descriptors of the power spectra produce better explanatory and predictive models of radiologists' judgments of breast density. Thus, local texture statistics capture, in some form, non-Gaussian aspects of texture that radiologists are using.

Conclusions

Since these local texture statistics are expected to be impacted by imaging factors like modality, dose, and image processing, they suggest avenues for understanding and optimizing observer performance.

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.

Clinical impact of molecular breast imaging as adjunct diagnostic modality in evaluation of indeterminate breast abnormalities and unresolved diagnostic concerns

PURPOSE

Improvements in molecular breast imaging (MBI) have increased the use of MBI as adjunct diagnostic modality and alternative to MRI. We aimed to assess the value of MBI in patients with equivocal breast lesions on conventional imaging, especially in terms of its ability to rule out malignancy.

METHODS

We selected patients who underwent MBI in addition to conventional diagnostics due to equivocal breast lesions between 2012 and 2015. All patients underwent digital mammography, target ultrasound and MBI. MBI was performed using a single-head Dilon 6800 gamma camera after administration of 600 MBq 99m Tc-sestamibi. Imaging was reported according to BI-RADS classification and compared with pathology or follow-up of ≥6 months.

RESULTS

Of 226 women included, pathology was obtained in 106 (47%) and (pre)malignant lesions were found in 25 (11%). Median follow-up was 5.4 years (IQR 3.9-7.1). Sensitivity was higher for MBI compared to conventional diagnostics (84% vs. 32%; P  = 0.002), identifying malignancy in 21 and 6 patients, respectively, but specificity did not differ (86% vs. 81%; P  = 0.161). Positive and negative predictive value were 43% and 98% for MBI and 17% and 91% for conventional diagnostics. MBI was discordant with conventional diagnostics in 68 (30%) patients and correctly changed diagnosis in 46 (20%) patients, identifying 15 malignant lesions. In subgroups with nipple discharge ( N  = 42) and BI-RADS 3 lesions ( N  = 113) MBI detected 7 of 8 occult malignancies.

CONCLUSION

MBI correctly adjusted treatment in 20% of patients with diagnostic concerns after conventional work-up, and could rule out malignancy with a high negative predictive value of 98%.

Molecular Breast Imaging in the Screening Setting

Early detection of breast cancer through screening mammography saves lives. However, the sensitivity of mammography for breast cancer detection is reduced in women with dense breast tissue. Imaging modalities for supplemental breast cancer screening include MRI, whole breast US, contrast-enhanced mammography, and molecular breast imaging (MBI). Molecular breast imaging with 99mTc-sestamibi is a functional imaging test to identify metabolically active areas in the breast with positioning analogous to mammography. Since 2011, there have been six large, published studies of screening MBI as a supplement to mammography involving over 6000 women from four different institutions. A multicenter, prospective clinical trial of 3000 women comparing breast cancer detection using screening digital breast tomosynthesis alone or in combination with MBI recently completed enrollment. This review focuses on the current evidence of MBI use for supplemental breast cancer screening, the strengths and limitations of MBI, and recent technological advances.

The Dense Breast Clinic: Initial Experience of a Patient-Centered Breast Imaging Clinic

OBJECTIVE

Establish a radiologist-run consultation clinic to review breast density and supplemental screening exams (SSEs) directly with patients in response to breast density reporting laws.

METHODS

Breast radiologists opened and staffed a clinic for formal patient consultations regarding breast density and SSEs. An IRB-approved questionnaire assessed patient knowledge of breast density, SSEs, and encounter satisfaction. Comparative statistical analyses were performed on knowledge-based questions.

RESULTS

From February 2019 to February 2021, 294 reimbursable consultations were performed with 215 patients completing pre- and post-consultation questionnaires (survey response rate, 73%). Median patient age was 58 years (range, 34-86 years) and 9% (19/210) had a personal history of breast cancer. An increase in patient knowledge of breast density and SSEs was observed as follows: breast density categories (9% correct pre-consultation (20/215), 86% correct post-consultation (185/215), P < 0.001), dense breast effects on cancer risk (39% correct pre-consultation (83/215), 84% post-consultation (180/215)), mammogram sensitivity (90% correct pre-consultation (193/215), 94% post-consultation (201/215)), and increased cancer detection with SSEs (82% correct pre-consultation (177/215), 95% post-consultation (205/215)) (P < 0.001). Post-consultation, 96% (200/209) were satisfied with the usefulness of information, 89% (186/209) strongly agreed they had sufficient knowledge of SSEs, and 81% (167/205) agreed they would like future opportunities to meet with a breast radiologist.

CONCLUSION

A consultation clinic staffed by breast radiologists focused on breast density and supplemental breast cancer screening can provide personalized patient counseling, engage patients in shared decision making, assist referring clinicians, and support high quality patient-centered care.

Abbreviated Molecular Breast Imaging: Feasibility and Future Considerations

OBJECTIVE

Molecular breast imaging (MBI) is a supplemental screening modality consistently demonstrating incremental cancer detection over mammography alone; however, its lengthy duration may limit widespread utilization. The study purpose was to assess feasibility of an abbreviated MBI protocol, providing readers with mediolateral oblique (MLO) projections only and assessing performance in lesion detection and localization.

METHODS

Retrospective IRB-exempt blinded reader study administered to 5 fellowship-trained breast imaging radiologists. Independent reads performed for 124 screening MBI cases, half abnormal and half negative/normal. Readers determined whether an abnormality was present, side of abnormality, and location of abnormality (medial/lateral). Abnormal cases had confirmatory biopsy or surgical pathology; normal cases had imaging follow-up ensuring true negative results. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to assess performance. A false negative result indicated that a reader failed to detect abnormal uptake; a false positive result indicated a reader incorrectly called an abnormality for a negative case. Tests for association included chi-square, Fisher-exact, and analysis of variance.

RESULTS

Mean reader performance for detecting abnormal uptake: sensitivity 96.8%, specificity 98.7%, PPV 98.8%, and NPV 96.9%. Accuracy in localizing lesions to the medial or lateral breast was 100%. There were no associations in reader performance with reader experience, reader technique, lesion morphology, or lesion pathology. Median lesion size was 1.0 cm (range: 0.4-8.0 cm). All readers correctly identified 97.7% (42/43) of lesions with malignant or elevated risk pathology.

CONCLUSION

An abbreviated MBI protocol (MLO images only) maintained high accuracy in lesion detection and localization.

Diagnostic capabilities of breast scintigraphy and molecular imaging of the mammary glands in the detection of various biological subtypes of breast cancer

Background. The accurate and early diagnosis of breast cancer can improve efficacy of the treatment. The standard diagnostic methods such as mammography, ultrasound, and magnetic resonance tomography have a pivotal role in the detection of breast tumors, however, in some cases, they have low diagnostic accuracy. Mammoscintigraphy (MSG) / molecular breast imaging (MBI) with tumor-specific radiopharmacy 99mTc-Technetril in patients with breast cancer can considerably increase the accuracy of diagnosis. However, the diagnostic performance of MSG / MBI in the detection of different biological subtypes of breast cancer is still under investigation.

Aim. To evaluate the accuracy of MSG / MBI with 99mTc-Technetril in diagnosis of different biological subtypes of breast cancer.

Materials and methods. The analysis included the results of MSG / MBI of 1080 patients (2154 mammary glands), who were examined for suspected breast cancer. MSG / MBI were performed 5–15 min after intravenous injection into the vein of one of the feet of 370–740 MBq of tumor-specific radiopharmacy 99mTc-Technetril. Examinations performed from 2007–2020 was carried out on the emission computed tomography Forte (Philips); since 2020 the molecular visualization has been providing on the special gamma-camera Discovery NM750b (General Electric). The obtained data were evaluated by 2 experienced radiologists. Verification of changes in breasts was provided by morphological examination (1060 cases) or dynamic observation.

Results. The sensitivity, specificity and overall accuracy of MSG / MBI were 90 %, 98 %, 95 % correspondingly. When diagnosing tumors with a diameter of up to 10 mm, the sensitivity of MSG / MBI was decreased to 83 %. In patients with various biological subtypes, the sensitivity of MSG / MBI was as follows: luminal A – 88 %; luminal B– – 91 %; luminal B+ – 92 %; triple negative – 93 %; HER2-positive – 96 %. The intensity of tumor uptake depended on the biological subtype of breast cancer. The average values of the 99mTc-Technetril uptake coefficient were as follows: luminal A – 1.59; luminal B– – 1.71; luminal B+ – 1.95; triple negative – 1.93; HER2-positive – 2.22.

Conclusion. Retrospective analysis indicate high diagnostic performance of MSG / MBI: sensitivity – 90 %, specificity – 98 %, accuracy – 95 %. There are significant differences in the intensity of 99mTc-Technetril accumulation in tumors in patients with different biological subtypes of breast cancer (p = 0.01–0.004). MSG / MBI characterized by significant differences in the sensitivity in the diagnosis of luminal A and HER2+ breast cancer subtypes: 88 % and 96 %, respectively (p = 0.02).

The Impact of Dense Breasts on the Stage of Breast Cancer at Diagnosis: A Review and Options for Supplemental Screening

The purpose of breast cancer screening is to find cancers early to reduce mortality and to allow successful treatment with less aggressive therapy. Mammography is the gold standard for breast cancer screening. Its efficacy in reducing mortality from breast cancer was proven in randomized controlled trials (RCTs) conducted from the early 1960s to the mid 1990s. Panels that recommend breast cancer screening guidelines have traditionally relied on the old RCTs, which did not include considerations of breast density, race/ethnicity, current hormone therapy, and other risk factors. Women do not all benefit equally from mammography. Mortality reduction is significantly lower in women with dense breasts because normal dense tissue can mask cancers on mammograms. Moreover, women with dense breasts are known to be at increased risk. To provide equity, breast cancer screening guidelines should be created with the goal of maximizing mortality reduction and allowing less aggressive therapy, which may include decreasing the interval between screening mammograms and recommending consideration of supplemental screening for women with dense breasts. This review will address the issue of dense breasts and the impact on the stage of breast cancer at the time of diagnosis, and discuss options for supplemental screening.

Advances and Future Directions in Molecular Breast Imaging

Molecular breast imaging (MBI) using 99mTc-sestamibi has advanced rapidly over the past decade. Technical advances allow lower-dose, higher-resolution imaging and biopsy capability. MBI can be used for supplemental breast cancer screening with mammography for women with dense breasts, as well as to assess neoadjuvant therapy response, evaluate disease extent, and predict breast cancer risk. This article highlights the current state of the art and future directions in MBI.

Updates in Molecular Breast Imaging

Molecular breast imaging (MBI) is a nuclear medicine study performed with dedicated gamma camera systems optimized to image the uptake of Tc-99m sestamibi in the breast. MBI provides a relatively low-cost and simple functional breast imaging method that can identify breast cancers obscured by dense fibroglandular tissue on mammography. Recent studies have also found that background levels of uptake in benign dense tissue may provide breast cancer risk information. This article discusses the latest updates in MBI technology, recent evidence supporting its clinical use, and work in progress that may aid in wider adoption of MBI.

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.

Molecular Breast Imaging: A Scientific Review

Molecular breast imaging (MBI) is a nuclear medicine technique that has evolved considerably over the past two decades. Technical advances have allowed reductions in administered doses to the point that they are now acceptable for screening. The most common radiotracer used in MBI, 99mTc-sestamibi, has a long history of safe use. Biopsy capability has become available in recent years, with early clinical experience demonstrating technically successful biopsies of MBI-detected lesions. MBI has been shown to be an effective supplemental screening tool in women with dense breasts and is also utilized for breast cancer staging, assessment of response to neoadjuvant chemotherapy, problem solving, and as an alternative to breast MRI in women who have a contraindication to MRI. The degree of background parenchymal uptake on MBI shows promise as a tool for breast cancer risk stratification. Radiologist interpretation is guided by a validated MBI lexicon that mirrors the BI-RADS lexicon. With short interpretation times, a fast learning curve for radiologists, and a substantially lower cost than breast MRI, MBI provides many benefits in the practices in which it is utilized. This review will discuss the current state of MBI technology, clinical applications of MBI, MBI interpretation, radiation dose associated with MBI, and the future of MBI.

Monte Carlo simulation of pixelated CZT detector with Geant4: validation of clinical molecular breast imaging system

Purpose. Molecular breast imaging (MBI) of^99mTc-sestamibi with dual-headed, pixelated, cadmium-zinc-telluride (CZT) detectors is increasingly used in breast cancer care for screening/detecting lesions, monitoring response to therapy, and predicting risk of cancer. MBI as a truly quantitative tool in these applications, however, is limited due the lack of absolute^99mTc-sestamibi uptake quantification. To help advance the field of quantitative MBI, we have developed a Monte Carlo simulation application of the GE Discovery NM 750b system.Methods. Our simulation consists of a two-step process using the Geant4 toolkit to model the detector and source geometry and to track photon interactions and a MATLAB script to model the charge transport within the pixelated CZT detector. Simulated detector and detector response model parameters were selected to match measured and simulated standard performance characteristics using various^99mTc point-, line-, and film-sources in air. The final model parameters were verified by comparing the count profiles, energy spectra, and region of interest counts between simulated and measured images of a breast phantom with two spherical lesions in 5 cm thick medium of air or water.Results. Final performance characteristics with^99mTc sources in air were: (1) energy resolution: 6.1% measured versus 5.9% simulated photopeak full-width at half-maximum (FWHM), (2) spatial resolution: mean error between measured and simulated FWHM of 0.08 mm across 4.4-14.0 mm FWHM range, and (3) sensitivity: 572 cpm/μCi measured versus 567 cpm/μCi simulated (<1% error). Good agreement was observed in the breast phantom line profiles through the spherical lesions and overall energy spectra, with <5% difference in sphere counts between simulated and measured data.Conclusion. A pixelated CZT charge transport and induction model was successfully implemented and validated to simulate imaging with the GE Discovery NM 750b system. This work will enable investigations improving MBI image quality and developing algorithms for uptake quantification.

Background Parenchymal Uptake on Molecular Breast Imaging and Breast Cancer Risk: A Cohort Study

BACKGROUND. Background parenchymal uptake (BPU) on molecular breast imaging (MBI) was identified in a case-control study as a breast cancer risk factor beyond mammographic density. To our knowledge, this finding has not yet been confirmed in a cohort study. OBJECTIVE. The objectives of this study were to examine the association of BPU with breast cancer and to estimate the absolute risk and discriminatory accuracy of BPU in a cohort study. METHODS. A retrospective cohort was established that included women without a history of breast cancer who underwent MBI from 2004 to 2015. Radiologists who were blinded to future breast cancer diagnoses assessed BPU on baseline MBI examinations as low (photopenic or minimal) or elevated (mild, moderate, or marked). Associations of BPU with breast cancer were estimated using multivariable Cox proportional hazards models of the time to diagnosis. The 5-year absolute risk was calculated for study subgroups. The discriminatory accuracy of BPU was also assessed. RESULTS. Among 2992 women (mean age, 56.3 years; SD, 10.6 years) who underwent MBI, breast cancer events occurred in 144 women (median follow-up, 7.3 years). Median time to diagnosis after MBI was 4.2 years (range, 0.5-11.6 years). Elevated BPU was associated with a greater breast cancer risk (hazard ratio [HR], 2.39; 95% CI, 1.68-3.41; p ≤ .001). This association remained in postmenopausal women (HR, 3.50; 95% CI, 2.31-5.31; p < .001) but was not significant in premenopausal women (HR, 1.29; 95% CI, 0.72-2.32; p = .39). The 5-year absolute risk of breast cancer was 4.3% (95% CI, 2.9-5.7%) for women with elevated BPU versus 2.5% (95% CI, 1.8-3.1%) for those with low BPU. Postmenopausal women with dense breasts and elevated BPU had a 5-year absolute risk of 8.1% (95% CI, 4.3-11.8%) versus 2.8% (1.8-3.8%) for those with low BPU. Among postmenopausal women, discriminatory accuracy for invasive cancer was improved with the addition of BPU versus use of the Gail risk score alone (C statistic, 65.1 vs 59.1; p = .04) or use of the Breast Cancer Surveillance Consortium risk score alone (C statistic, 66.4 vs 60.4; p = .04). CONCLUSION. BPU on MBI is an independent risk factor for breast cancer, with the strongest association observed among postmenopausal women with dense breasts. In postmenopausal women, BPU provides incremental discrimination in predicting breast cancer when combined with either the Gail model or the Breast Cancer Surveillance Consortium model. CLINICAL IMPACT. Observation of elevated BPU on MBI may identify a subset of women with dense breasts who would benefit most from supplemental screening or preventive options.

Screening Algorithms in Dense Breasts: AJR Expert Panel Narrative Review

Screening mammography reduces breast cancer mortality; however, when used to examine women with dense breasts, its performance and resulting benefits are reduced. Increased breast density is an independent risk factor for breast cancer. Digital breast tomosynthesis (DBT), ultrasound (US), molecular breast imaging (MBI), MRI, and contrast-enhanced mammography (CEM) each have shown improved cancer detection in dense breasts when compared with 2D digital mammography (DM). DBT is the preferred mammographic technique for producing a simultaneous reduction in recalls (i.e., additional imaging). US further increases cancer detection after DM or DBT and reduces interval cancers (cancers detected in the interval between recommended screening examinations), but it also produces substantial additional false-positive findings. MBI improves cancer detection with an effective radiation dose that is approximately fourfold that of DM or DBT but is still within accepted limits. MRI provides the greatest increase in cancer detection and reduces interval cancers and late-stage disease; abbreviated techniques will reduce cost and improve availability. CEM appears to offer performance similar to that of MRI, but further validation is needed. Dense breast notification will soon be a national standard; therefore, understanding the performance of mammography and supplemental modalities is necessary to optimize screening for women with dense breasts.

Supplemental Screening for Patients at Intermediate and High Risk for Breast Cancer

The sensitivity of mammography is more limited in patients with dense breasts and some patients at higher risk for breast cancer. Patients with intermediate or high risk for breast cancer may begin screening earlier and benefit from supplemental screening techniques beyond standard 2-dimensional mammography. A patient's individual risk factors for developing breast cancer, their breast density, and the evidence supporting specific modalities for a given clinical scenario help to determine the need for supplemental screening and the modality chosen. Additional factors include the availability of supplemental screening techniques at an individual institution, cost, insurance coverage, and state-specific breast density legislation.

Characterization of a multi-pinhole molecular breast tomosynthesis scanner

In recent years, breast imaging using radiolabelled molecules has attracted significant interest. Our group has proposed a multi-pinhole molecular breast tomosynthesis (MP-MBT) scanner to obtain 3D functional molecular breast images at high resolutions. After conducting extensive optimisation studies using simulations, we here present a first prototype of MP-MBT and evaluate its performance using physical phantoms. The MP-MBT design is based on two opposing gamma cameras that can image a lightly compressed pendant breast. Each gamma camera consists of a 250 × 150 mm² detector equipped with a collimator with multiple pinholes focusing on a line. The NaI(Tl) gamma detector is a customised design with 3.5 mm intrinsic spatial resolution and high spatial linearity near the edges due to a novel light-guide geometry and the use of square PMTs. A volume-of-interest is scanned by translating the collimator and gamma detector together in a sequence that optimises count yield from the scan region. Derenzo phantom images showed that the system can reach 3.5 mm resolution for a clinically realistic ^99mTc activity concentration in an 11-minute scan, while in breast phantoms the smallest spheres visible were 6 mm in diameter for the same scan time. To conclude, the experimental results of the novel MP-MBT scanner showed that the setup had sub-centimetre breast tumour detection capability which might facilitate 3D molecular breast cancer imaging in the future.

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.

The Clinical Utility of a Negative Result at Molecular Breast Imaging: Initial Proof of Concept

Purpose

To calculate the negative predictive value (NPV) and false-negative rate (FNR) of molecular breast imaging (MBI) performed in patients who had low-suspicion index findings on mammograms and US images.

Materials and Methods

This retrospective study included patients who had undergone MBI between January 2015 and July 2017, who had index findings on screening mammograms and/or US images, and for whom either histopathologic results or a minimum of 1-year imaging follow-up results were available. A drawn dose of 8 mCi (296 MBq) of technetium 99m sestamibi was administered to all patients for MBI. The NPV and FNR of MBI was calculated for the cohort of 381 findings among 338 women (median age, 56 years; age range, 28-89 years) included in this study.

Results

Overall, 292 of the 381 (76.6%) MBI results were interpreted as negative. Of the 292, 27 patients underwent subsequent biopsies, results of which were negative for cancer; one patient underwent biopsy, and the result was positive for cancer; and 264 patients had true-negative findings based on follow-up imaging for a minimum of 1 year. Of the 89 MBI acquisitions interpreted as positive, there were 36 cancers. The NPV was calculated to be 99.7% (291 of 292, 95% confidence interval [CI]: 99.1%, 100%), and the FNR was 2.7% (one of 37, 95% CI: 0%, 7.9%). Interposing MBI reduced the number of biopsies by 67.5%.

Conclusion

The concept of the clinical utility of a negative MBI result may be valid but requires further testing.Keywords: Breast, Molecular Imaging-Cancer© RSNA, 2020.

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.

Classification of Background Parenchymal Uptake on Molecular Breast Imaging Using a Convolutional Neural Network

PURPOSE

Background parenchymal uptake (BPU), which describes the level of radiotracer uptake in normal fibroglandular tissue on molecular breast imaging (MBI), has been identified as a breast cancer risk factor. Our objective was to develop and validate a deep learning model using image convolution to automatically categorize BPU on MBI.

METHODS

MBI examinations obtained for clinical and research purposes from 2004 to 2015 were reviewed to classify the BPU pattern using a standardized five-category scale. Two expert radiologists provided interpretations that were used as the reference standard for modeling. The modeling consisted of training and validating a convolutional neural network to predict BPU. Model performance was summarized in data reserved to test the performance of the algorithm at the per-image and per-breast levels.

RESULTS

Training was performed on 24,639 images from 3,133 unique patients. The model performance on the withheld testing data (6,172 images; 786 patients) was evaluated. Using direct matching on the predicted classification resulted in an accuracy of 69.4% (95% CI, 67.4% to 71.3%), and if prediction within one category was considered, accuracy increased to 96.0% (95% CI, 95.2% to 96.7%). When considering the breast-level prediction of BPU, the accuracy remained strong, with 70.3% (95% CI, 68.0% to 72.6%) and 96.2% (95% CI, 95.3% to 97.2%) for the direct match and allowance for one category, respectively.

CONCLUSION

BPU provided a robust target for training a convolutional neural network. A validated computer algorithm will allow for objective, reproducible encoding of BPU to foster its integration into risk-stratification algorithms.

Coherence-Based Beamforming Increases the Diagnostic Certainty of Distinguishing Fluid from Solid Masses in Breast Ultrasound Exams

Ultrasound is often used as a supplement for mammography to detect breast cancer. However, one known limitation is the high false-positive rates associated with breast ultrasound. We investigated the use of coherence-based beamforming (which directly displays spatial coherence) as a supplement to standard ultrasound B-mode images in 25 patients recommended for biopsy (26 masses in total), with the eventual goal of decreasing false-positive rates. Because of the coherent signal present within solid masses, coherence-based beamforming methods allow solid and fluid-filled masses to appear significantly different (p < 0.001). When presented to five board-certified radiologists, the inclusion of robust short-lag spatial coherence (R-SLSC) images in the diagnostic pipeline reduced the uncertainty of fluid-filled mass contents from 47.5% to 15.8% and reduced the percentage of fluid-filled masses unnecessarily recommended for biopsy from 43.3% to 13.3%. These results are promising for the potential introduction of R-SLSC (and related coherence-based beamforming methods) into the breast clinic to improve diagnostic certainty and reduce the number of unnecessary biopsies.

99mTC-sestamibi breast imaging: Current status, new ideas and future perspectives

Here we proposed the most recent innovations in the use of Breast Specific Gamma Imaging with ⁹⁹mTc-sestamibi for the management of breast cancer patients. To this end, we reported the recent discoveries concerning: a) the implementation of both instrumental devices and software, b) the biological mechanisms involved in the ⁹⁹mTc-sestamibi uptake in breast cancer cells, c) the evaluation of Breast Specific Gamma Imaging with ⁹⁹mTc-sestamibi as predictive markers of metastatic diseases. In this last case, we also reported preliminary data about the capability of Breast Specific Gamma Imaging with ⁹⁹mTc-sestamibi to identify breast cancer lesions with high propensity to form bone metastatic lesions due to the presence of Breast Osteoblast-Like Cells.

Dose Reduction in Molecular Breast Imaging With a New Image-Processing Algorithm

OBJECTIVE. The purpose of this study was to determine whether application of a proprietary image-processing algorithm would allow a reduction in the necessary administered activity for molecular breast imaging (MBI) examinations. MATERIALS AND METHODS. Images from standard-dose MBI examinations (300 MBq ^99mTc-sestamibi) of 50 subjects were analyzed. The images were acquired in dynamic mode and showed at least one breast lesion. Half-dose MBI examinations were simulated by summing one-half of the dynamic frames and were processed with the algorithm under study in both a default and a preferred filter mode. Two breast radiologists independently completed a set of two-alternative forced-choice tasks to compare lesion conspicuity on standard-dose images, half-dose images, and the algorithm-processed half-dose images in both modes. RESULTS. Relative to the standard-dose images, the half-dose images were preferred in 4, the default-filtered half-dose images in 50, and preferred-filtered half-dose images in 76 of 100 readings. Compared with standard-dose images, in terms of lesion conspicuity, the half-dose images were rated better in 2, equivalent in 6, and poorer in 92 of 100 readings. The default-filtered half-dose images were rated better, equivalent, or poorer in 13, 73, and 14 of 100 readings. The preferred-filtered half-dose images were rated as better, equivalent, or poorer in 55, 34, and 11 of 100 readings. CONCLUSION. Compared with that on standard-dose images, lesion conspicuity on images obtained with the algorithm and acquired at one-half the standard dose was equivalent or better without compromise of image quality. The algorithm can also be used to decrease imaging time with a resulting increase in patient comfort and throughput.

Comparative Benefit-to-Radiation Risk Ratio of Molecular Breast Imaging, Two-Dimensional Full-Field Digital Mammography with and without Tomosynthesis, and Synthetic Mammography with Tomosynthesis

Purpose

To apply previously published benefit-to-risk ratio methods for mammography and molecular breast imaging (MBI) risk estimates to an expanded range of mammographic screening techniques, compressed breast thicknesses, and screening views.

Materials and Methods

Only previously published estimates were used; therefore, this study was exempt from the requirement to obtain institutional review board approval. Benefit-to-risk ratios were calculated as the ratio of breast cancer deaths averted and lives lost to screening over 10-year intervals starting at age 40 years for MBI, two-dimensional (2D) full-field digital mammography (FFDM) alone, 2D FFDM with synthetic mammography, and 2D FFDM with tomosynthesis for two-, four-, and five-view screening mammography and compressed breast thicknesses of 20-29 mm, 50-59 mm, and 80-89 mm.

Results

Central estimates of the benefit-to-risk ratios ranged from 3 to 179 for screening mammography and from 5 to 9 for MBI. Benefit-to-risk ratios for MBI were inferior to those for mammography for most scenarios, but MBI may be performed at an equal or superior benefit-to-risk ratio for women aged 40-59 years with a compressed breast thickness of at least 80 mm and for those undergoing mammographic screening examinations with four or five views per breast. The benefit-to-risk ratios across all ages with use of tomosynthesis plus 2D FFDM as a screening examination were 45% lower than those for tomosynthesis plus synthetic mammography.

Conclusion

Benefit-to-risk ratios for MBI are within the lower range of those for mammography when accounting for variation in mammography technique, compressed breast thickness, and age. Benefit-to-risk ratios of synthetic mammography plus tomosynthesis are superior to those of tomosynthesis plus 2D FFDM.Keywords: Breast, Mammography, Molecular Imaging, Molecular Imaging-Cancer, Radiation Safety, Radionuclide Studies, Screening, Tomosynthesis© RSNA, 2019See also the commentary by Hruska in this issue.

Breast density implications and supplemental screening

Digital breast tomosynthesis (DBT) has been widely implemented in place of 2D mammography, although it is less effective in women with extremely dense breasts. Breast ultrasound detects additional early-stage, invasive breast cancers when combined with mammography; however, its relevant limitations, including the shortage of trained operators, operator dependence and small field of view, have limited its widespread implementation. Automated breast sonography (ABS) is a promising technique but the time to interpret and false-positive rates need to be improved. Supplemental screening with contrast-enhanced magnetic resonance imaging (MRI) in high-risk women reduces late-stage disease; abbreviated MRI protocols may reduce cost and increase accessibility to women of average risk with dense breasts. Contrast-enhanced digital mammography (CEDM) and molecular breast imaging improve cancer detection but require further validation for screening and direct biopsy guidance should be implemented for any screening modality. This article reviews the status of screening women with dense breasts. KEY POINTS: • The sensitivity of mammography is reduced in women with dense breasts. Supplemental screening with US detects early-stage, invasive breast cancers. • Tomosynthesis reduces recall rate and increases cancer detection rate but is less effective in women with extremely dense breasts. • Screening MRI improves early diagnosis of breast cancer more than ultrasound and is currently recommended for women at high risk. Risk assessment is needed, to include breast density, to ascertain who should start early annual MRI screening.

Molecular breast imaging detected invasive lobular carcinoma in dense breasts: A case report

This case highlights the role of molecular breast imaging (MBI) in evaluating persistent clinical concerns after a negative diagnostic mammogram and ultrasound. MBI is especially useful in the diagnosis of invasive lobular carcinoma due to its occult nature on conventional imaging modalities.

Dedicated Breast Gamma Camera Imaging and Breast PET: Current Status and Future Directions

Recent advances in nuclear medicine instrumentation have led to the emergence of improved molecular imaging techniques to image breast cancer: dedicated gamma cameras using γ-emitting ^99mTc-sestamibi and breast-specific PET cameras using ¹⁸F-fluorodeoxyglucose. This article focuses on the current role of such approaches in the clinical setting including diagnosis, assessing local extent of disease, monitoring response to therapy, and, for gamma camera imaging, possible supplemental screening in women with dense breasts. Barriers to clinical adoption and technologies and radiotracers under development are also discussed.

Breast Lesions Detected via Molecular Breast Imaging: Physiological Parameters Affecting Interpretation

RATIONALE AND OBJECTIVES

To evaluate correlations between molecular breast imaging (MBI) descriptor characteristics and positive predictive value (PPV) in detecting breast cancer.

MATERIALS AND METHODS

A retrospective review was performed on 193 suspicious findings from 153 women (31-81 years) with positive MBI examinations. We assessed associations between (i) lesion pattern (mass vs. nonmass) and PPV; (ii) lesion pattern and suspected likelihood of cancer (low vs. moderate vs. high); (iii) background parenchymal uptake (BPU) (homogeneous vs. heterogeneous) and PPV; (iv) breast density (dense vs. non-dense) and PPV; and (v) BPU and density.

RESULTS

One hundred ten of 153 patients were diagnosed with malignancy or high-risk pathology (PPV1 = 71.9%), and 130/193 biopsies resulted in malignant or high-risk lesions (PPV3 = 67.4%). Biopsies of mass vs. nonmass findings had comparable PPV3 (71.7% vs. 61.3%; P = .0717). Mass findings were correlated with higher suspicion for cancer than nonmass findings (P < .001). There was no significant difference in PPV3 when comparing biopsies from homogeneous vs. heterogeneous BPU (72.5% vs. 60.7%; P = .103). No association was found between patients' BPU and diagnosed cancer or high-risk lesions (P = .513). Biopsies from nondense breasts demonstrated higher PPV3 than biopsies from dense breasts (85.4% vs. 60.6%; P = .0025); patients with nondense breasts were more likely to be diagnosed with cancer or high-risk pathology (PPV1 = 87.8% vs. 66.0%; P = .00844). Dense breasts had a greater association with heterogeneous BPU (P = .0844).

CONCLUSION

Neither variability in mass or nonmass positive MBI findings, nor variability in BPU on MBI were significant determinants for the probability of malignancy. Dense breasts were associated with lower predictability and heterogeneous BPU on MBI.

Comparison of fan beam, slit-slat and multi-pinhole collimators for molecular breast tomosynthesis

Recently, we proposed and optimized dedicated multi-pinhole molecular breast tomosynthesis (MBT) that images a lightly compressed breast. As MBT may also be performed with other types of collimators, the aim of this paper is to optimize MBT with fan beam and slit-slat collimators and to compare its performance to that of multi-pinhole MBT to arrive at a truly optimized design. Using analytical expressions, we first optimized fan beam and slit-slat collimator parameters to reach maximum sensitivity at a series of given system resolutions. Additionally, we performed full system simulations of a breast phantom containing several tumours for the optimized designs. We found that at equal system resolution the maximum achievable sensitivity increases from pinhole to slit-slat to fan beam collimation with fan beam and slit-slat MBT having on average a 48% and 20% higher sensitivity than multi-pinhole MBT. Furthermore, by inspecting simulated images and applying a tumour-to-background contrast-to-noise (TB-CNR) analysis, we found that slit-slat collimators underperform with respect to the other collimator types. The fan beam collimators obtained a similar TB-CNR as the pinhole collimators, but the optimum was reached at different system resolutions. For fan beam collimators, a 6-8 mm system resolution was optimal in terms of TB-CNR, while with pinhole collimation highest TB-CNR was reached in the 7-10 mm range.

Molecular Breast Imaging: Administered Activity Does Not Require Adjustment Based on Patient Size

At our institution, molecular breast imaging (MBI) is performed with 300 MBq of ^99mTc-sestamibi for all patients. For some nuclear medicine procedures, administered activity or imaging time is increased for patients of larger size to obtain adequate counts. Our objective was to assess whether uptake of ^99mTc-sestamibi in the breast is influenced by patient size. Methods: Records from patients who underwent a clinical MBI examination between July and November 2016 were reviewed. Those in whom our standard injection and preparation techniques were followed were included in the analysis. Patients were injected with approximately 300 MBq of ^99mTc-sestamibi. Residual activity was measured to allow calculation of exact administered activity for each patient. Breast images were acquired at 10 min/view using a dual-head cadmium zinc telluride-based γ-camera. Breast thickness was measured as the distance between the 2 detectors. Patient height, weight, body surface area, and body mass index were obtained from records. Lean body mass with the James equation (LBM_James) and Janmahasatian correction (LBM_Janma) was calculated. Count density in the breast tissue was measured by drawing a region of interest around the central breast tissue of the right breast mediolateral-oblique view of the lower detector. Count density was expressed as cts/cm²/MBq of administered activity. Spearman correlation coefficient (r_s) was calculated. Results: A total of 200 patients were analyzed. No dose infiltration was suspected at any injection. Average administered activity was 292 MBq (SD, 13.8 MBq; range, 247-326 MBq). Average count density was 7.2 cts/cm²/MBq (SD, 2.7 cts/cm²/MBq; range, 3.1-17.8 cts/cm²/MBq). MBI count density was weakly negatively correlated with height (r_s = -0.18; P = 0.01), weight (r_s = -0.23; p = <0.001), body mass index (r_s = -0.16; P = 0.02), body surface area (r_s = -0.22; P = 0.002), LBM_James (r_s = -0.23; P = 0.001), and LBM_Janma (r_s = -0.23; P = 0.001). No correlation was observed between count density and breast thickness (r_s = 0.06; P = 0.37). Conclusion: Our results suggest a lack of relationship between uptake of ^99mTc-sestamibi in breast tissue and body size or compressed breast thickness. Altering from the standard 300 MBq of administered activity for larger patients is likely unnecessary.

Coil geometry effects on scanning single-coil magnetic induction tomography

Alternative coil designs for single coil magnetic induction tomography are considered in this work, with the intention of improving upon the standard design used previously. In particular, we note that the blind spot associated with this coil type, a portion of space along its axis where eddy current generation can be very weak, has an important effect on performance. The seven designs tested here vary considerably in the size of their blind spot. To provide the most discerning test possible, we use laboratory phantoms containing feature dimensions similar to blind spot size. Furthermore, conductivity contrasts are set higher than what would occur naturally in biological systems, which has the effect of weakening eddy current generation at coil locations that straddle the border between high and low conductivity features. Image reconstruction results for the various coils show that coils with smaller blind spots give markedly better performance, though improvements in signal-to-noise ratio could alter that conclusion.

Imaging Management of Breast Density, a Controversial Risk Factor for Breast Cancer

BACKGROUND

Breast density is well recognized as an independent risk factor for the development of breast cancer. However, the magnitude of risk is controversial. As the public becomes increasingly aware of breast density as a risk factor, legislation and notification laws in relation to breast density have become common throughout the United States. Awareness of breast density as a risk factor for breast cancer presents new challenges for the clinician in the approach to the management and screening of women with dense breasts.

METHODS

The evidence and controversy surrounding breast density as a risk factor for the development of breast cancer are discussed. Common supplemental screening modalities for breast cancer are also discussed, including tomosynthesis, ultrasonography, and magnetic resonance imaging. A management strategy for screening women with dense breasts is also presented.

RESULTS

The American College of Radiology recognizes breast density as a controversial risk factor for breast cancer, whereas the American Congress of Obstetricians and Gynecologists recognizes breast density as a modest risk factor. Neither organization recommends the routine use of supplemental screening in women with dense breasts without considering additional patient-related risk factors.

CONCLUSIONS

Breast density is a poorly understood and controversial risk factor for the development of breast cancer. Mammography is a screening modality proven to reduce breast cancer-related mortality rates and is the single most appropriate tool for population-based screening. Use of supplemental screening modalities should be tailored to individual risk assessment.

First Clinical Experience Using Stereotactic Breast Biopsy Guided by 99mTc-Sestamibi

OBJECTIVE

The purpose of this study is to evaluate a new device using molecular breast imaging (MBI) for ^99mTc-sestamibi-guided stereotactic lesion localization as a complementary biopsy tool.

MATERIALS AND METHODS

From December 2012 to May 2016, a total of 38 consecutive women (mean age, 59 years; range, 41-77 years) underwent ^99mTc-sestamibi-guided biopsy using a new MBI-based device and were retrospectively reviewed. The biopsy modality used five steps: stereotactic localization of the ^99mTc-sestamibi-avid lesion, calculation of coordinates of the lesion location using dedicated software, placement of the needle, verification of the correct needle position, and tissue sampling with a vacuum-assisted device followed by placement of a radiologic marker at the biopsy site and ex vivo measurement of the biopsy specimens.

RESULTS

The procedure was technically successful in all 38 lesions. In all cases, biopsy samples were radioactive and adequate for histopathologic analysis. Nineteen lesions (50%) were found to be malignant, and the remaining lesions were found to be benign. The mean procedure time was 71 minutes (range, 44-112 minutes). The radiologic marker was successfully deployed in 37 lesions (97%). Two hematomas and three vasovagal reactions were observed.

CONCLUSION

Technetium-99m sestamibi-guided biopsy performed using a dedicated MBI-based device is technically feasible and represents a valuable complementary biopsy tool in breast lesion diagnosis.

Comparison of Tc-99m maraciclatide and Tc-99m sestamibi molecular breast imaging in patients with suspected breast cancer

Background

Molecular breast imaging (MBI) performed with ^99mTc sestamibi has been shown to be a valuable technique for the detection of breast cancer. Alternative radiotracers such as ^99mTc maraciclatide may offer improved uptake in breast lesions. The purpose of this study was to compare relative performance of ^99mTc sestamibi and ^99mTc maraciclatide in patients with suspected breast cancer, using a high-resolution dedicated gamma camera for MBI. Women with breast lesions suspicious for malignancy were recruited to undergo two MBI examinations—one with ^99mTc sestamibi and one with ^99mTc maraciclatide. A radiologist interpreted MBI studies in a randomized, blinded fashion to assign an assessment score (1–5) and measured lesion size. Lesion-to-background (L/B) ratio was measured with region-of-interest analysis.

Results

Among 39 analyzable patients, 21 malignant tumors were identified in 21 patients. Eighteen of 21 tumors (86%) were seen on ^99mTc sestamibi MBI and 19 of 21 (90%) were seen on ^99mTc maraciclatide MBI (p = 1). Tumor extent measured with both radiopharmaceuticals correlated strongly with pathologic size (^99mTc sestamibi, r = 0.84; ^99mTc maraciclatide, r = 0.81). The L/B ratio in detected breast cancers was similar for the two radiopharmaceuticals: 1.55 ± 0.36 (mean ± S.D.) for ^99mTc sestamibi and 1.62 ± 0.37 (mean ± S.D.) for ^99mTc maraciclatide (p = 0.53). No correlation was found between the L/B ratio and molecular subtype for ^99mTc sestamibi (r_s = 0.12, p = 0.63) or ^99mTc maraciclatide (r_s = −0.12, p = 0.64). Of 20 benign lesions, 10 (50%) were seen on ^99mTc sestamibi and 9 of 20 (45%) were seen on ^99mTc maraciclatide images (p = 0.1). The average L/B ratio for benign lesions was 1.34 ±0.40 (mean ±S.D.) for ^99mTc sestamibi and 1.41 ±0.52 (mean ±S.D.) for ^99mTc maraciclatide (p = 0.75). Overall diagnostic performance was similar for both radiopharmaceuticals. AUC from ROC analysis was 0.83 for ^99mTc sestamibi and 0.87 for ^99mTc maraciclatide (p = 0.64).

Conclusions

^99mTc maraciclatide offered comparable lesion uptake to ^99mTc sestamibi, in both malignant and benign lesions. There was good correlation between lesion extent and uptake measured from both radiopharmaceuticals. ^99mTc maraciclatide offered a marginal (but not significant) improvement in sensitivity over ^99mTc sestamibi. Our findings did not support an association between the uptake of either radiopharmaceutical and tumor molecular subtype.

Trial registration

ClinicalTrials.gov, NCT00888589