Clinical Evidence

Nuclear imaging of the breast: Translating achievements in instrumentation into clinical use

Carrie B. Hruska and Michael K. O’Connor; Department of Radiology, Mayo Clinic

 

Approaches to imaging the breast with nuclear medicine and/or molecular imaging methods have been under investigation since the late 1980s when a technique called scintimammography was first introduced. This review charts the progress of nuclear imaging of the breast over the last 20 years, covering the development of newer techniques such as breast specific gamma imaging, molecular breast imaging, and positron emission mammography. Key issues critical to the adoption of these technologies in the clinical environment are discussed, including the current status of clinical studies, the efforts at reducing the radiation dose from procedures associated with these technologies, and the relevant radiopharmaceuticals that are available or under development. The necessary steps required to move these technologies from bench to bedside are also discussed. 

99mTc-Sestamibi Using a Direct Conversion Molecular Breast Imaging System to Assess Tumor Response to Neoadjuvant Chemotherapy in Women With Locally Advanced Breast Cancer

David Mitchell, MB,* Carrie B. Hruska, PhD,* Judy C. Boughey, MD,Þ Dietlind L. Wahner-Roedler, MD,þ Katie N. Jones, MD,* Cindy Tortorelli, MD,§ Amy Lynn Conners, MD,* and Michael K. O’Connor, PhD*

Purpose: The objective of this study was to determine the ability of breast imaging with 99mTc-sestamibi and a direct conversion molecular breast imaging (MBI) system to predict early response to neoadjuvant chemotherapy (NAC).

Conclusions: Changes in T/B ratio on MBI images performed at 3 to 5 weeks following initiation of NAC were accurate at predicting the presence or absence of residual disease at NAC completion.

White Paper: Molecular Breast Imaging: The quest to see more clearly

GE Healthcare

In July of 2012, a law was passed by the state of New York requiring mammography providers to inform patients if dense breast tissue was found on their exams. Multiple states including New York, Connecticut, Texas, Virginia and California, responded to a groundswell of patient advocacy. At issue is a basic limitation of mammography widely recognized by imagers; while x-ray mammography remains the gold standard for the detection of early breast cancers, it is significantly less accurate in women with dense breasts. The sensitivity of mammography in women with extremely dense breast tissue has been reported to be less than 50%. Making matters worse is the fact that dense breast tissue is an independent risk factor for breast cancer, resulting in a population of women with a greater number of breast cancers that are harder to find.

Dedicated dual-head gamma imaging for breast cancer screening in women with mammographically dense breasts

Deborah J. Rhodes, MD, , Carrie B. Hruska, PhD, , Stephen W. Phillips, MD1, , Dana H. Whaley, MD, and , Michael K. O’Connor, PhDFrom the Departments of Medicine (D.J.R.) and Radiology (C.B.H., S.W.P., D.H.W., M.K.O.), Mayo Clinic

 

Purpose: To compare performance characteristics of dedicated dual-head gamma imaging and mammography in screening women with mammographically dense breasts.

 

Conclusions: Addition of gamma imaging to mammography significantly increased detection of node-negative breast cancer in dense breasts by 7.5 per 1000 women screened (95% CI: 3.6, 15.4). To be clinically important, gamma imaging will need to show equivalent performance at decreased radiation doses.

Proof of concept for low-dose molecular breast imaging with a dual-head CZT gamma camera. Part II. Evaluation in patients

Carrie B. Hruska,Amanda L. Weinmann, Christina M. Tello Skjerseth, Eric M. Wagenaar, Amy L. Conners, Cindy L. Tortorelli, Robert W. Maxwell, Deborah J. Rhodes and Michael K. O’Connor, Department of Radiology, Mayo Clinic

 

Purpose: Molecular breast imaging (MBI) has shown promise as an adjunct screening technique to mammography for women with dense breasts. The demonstration of reliable lesion detection with MBI performed at low administered doses of Tc-99 m sestamibi, comparable in effective radiation dose to screening mammography, is essential to adoption of MBI for screening. The concept of per- forming low-dose MBI with dual-head cadmium zinc telluride (CZT) gamma cameras has been investigated in phantoms in Part I. In this work, the objectives were to evaluate the impact of the count sensitivity improvement methods on image quality in patient MBI exams and to determine if adequate lesion detection could be achieved at reduced doses.

Conclusions: Review of patient studies showed that registered optimized collimation and wide energy window resulted in a substantial gain in count sensitivity as previously indicated by phan- tom results. This proof of concept work indicates that MBI performed at administered doses of 296 MBq Tc-99 m sestamibi with the applied count sensitivity improvements permits the detection of small breast lesions in patients. Findings suggest that further reductions in acquisition duration or administered dose may be achievable.

Proof of concept for low-dose molecular breast imaging with a dual-head CZT gamma camera. Part I. Evaluation in phantoms

Carrie B. Hruska, Amanda L. Weinmann, and Michael K. O’Connor Department of Radiology, Mayo Clinic

 

Purpose: Molecular breast imaging (MBI) is a nuclear medicine technology that uses dual-head cadmium zinc telluride (CZT) gamma cameras to image functional uptake of a radiotracer, Tc-99m sestamibi, in the breast. An important factor in adoption of MBI in the screening setting is reduction of the necessary administered dose of Tc-99m sestamibi from the typically used dose of 740 MBq to approximately 148 MBq, such that MBI’s whole-body effective dose is comparable to that of screening mammography. Methods that increase MBI count sensitivity may allow a proportional reduction in the necessary administered dose. Our objective was to evaluate the impact of two count sensitivity improvement methods on image quality by evaluating count sensitivity, spatial resolution, and lesion contrast in phantom simulations.

 

Conclusions: Registered optimized collimation and wide energy window yield a substantial gain in count sensitivity and measurable gain in CNR, with some loss in spatial resolution compared to the standard collimator designs and energy windows used on these two systems. At low-count densities calculated to represent doses of 148 MBq, this tradeoff results in adequate count density and lesion contrast for detection of lesions 8 mm in the middle of a typical breast (3 cm deep) and lesions 6 mm close to the collimator (1 cm deep).

 

Molecular Breast Imaging at Reduced Radiation Dose for Supplemental Screening in Mammographically Dense Breasts
Carrie B. Hruska and Michael K. O’Connor; Department of Radiology, Mayo Clinic

 

OBJECTIVE. The purpose of this study was to assess the diagnostic performance of supplemental screening molecular breast imaging (MBI) in women with mammographically dense breasts after system modifications to permit radiation dose reduction.

CONCLUSION. When added to screening mammography, MBI performed using a radiopharmaceutical activity acceptable for screening (effective dose 2.4 mSv) yielded a supplemental cancer detection rate of 8.8 per 1000 women with mammographically dense breasts.