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

PURPOSE: To compare performance characteristics of dedicated dual-head gamma imaging and mammography in screening women with mammographically dense breasts. MATERIALS AND METHODS: Asymptomatic women (n = 1007) who had heterogeneously or extremely dense breasts on prior mammograms and additional risk factors provided informed consent to enroll in an institutional review board-approved HIPAA-compliant protocol. Participants underwent mammography and gamma imaging after a 740-mBq (20-mCi) technetium 99m sestamibi injection. Reference standard (more severe cancer diagnosis or 12-month follow-up findings) was available for 936 of 969 eligible participants. Diagnostic yield, sensitivity, specificity, and positive predictive values (PPVs) were determined for mammography, gamma imaging, and both combined. RESULTS: Of 936 participants, 11 had cancer (one with mammography only, seven with gamma imaging only, two with both combined, and one with neither). Diagnostic yield was 3.2 per 1000 (95% confidence interval [CI]: 1.1, 9.3) for mammography, 9.6 per 1000 (95% CI: 5.1, 18.2) for gamma imaging, and 10.7 per 1000 (95% CI: 5.8, 19.6) for both (P = .016 vs mammography alone). One participant had a second ipsilateral cancer detected with gamma imaging only. Prevalent screening gamma imaging demonstrated equivalent specificity relative to incident screening mammography (93% [861 of 925] vs 91% [840 of 925], P = .069). Of eight cancers detected with gamma imaging only, six (75%) were invasive (median size, 1.1 cm; range, 0.4-5.1 cm); all were node negative. The ratio of the number of patients with breast cancer per number of screening examinations with abnormal findings was 3% (three of 88) for mammography and 12% (nine of 73) for gamma imaging (P = .01). The number of breast cancers diagnosed per number of biopsies performed was 18% (three of 17) for mammography and 28% (10 of 36) for gamma imaging (P = .36). CONCLUSION: 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.

Molecular breast imaging: use of a dual-head dedicated gamma camera to detect small breast tumors.

OBJECTIVE: Molecular breast imaging with a single-head cadmium zinc telluride (CZT) gamma camera has previously been shown to have good sensitivity for the detection of small lesions. To further improve sensitivity, we developed a dual-head molecular breast imaging system using two CZT detectors to simultaneously acquire opposing breast views and reduce lesion-to-detector distance. We determined the incremental gain in sensitivity of molecular breast imaging with dual detectors. SUBJECTS AND METHODS: Patients with BI-RADS category 4 or 5 lesions < 2 cm that were identified on mammography or sonography and scheduled for biopsy underwent molecular breast imaging as follows: After injection of 740 MBq of technetium-99m ((99m)Tc) sestamibi, 10-minute craniocaudal and mediolateral oblique views of each breast were acquired. Blinded reviews were performed using images from both detectors 1 and 2 and images from detector 1 only (simulating a single-head system). Lesions were scored on a scale of 1-5; 2 or higher was considered positive. RESULTS: Of the 150 patients in the study, 128 cancers were confirmed in 88 patients. Averaging the results from the three blinded readers, the sensitivity of dual-head molecular breast imaging was 90% (115/128), whereas the sensitivity from review of only single-head molecular breast imaging was 80% (102/128). The sensitivity for the detection of cancers < or = 10 mm in diameter was 82% (50/61) for dual-head molecular breast imaging and 68% (41/61) for single-head molecular breast imaging. On average, 13 additional cancers were seen on dual-head images and the tumor uptake score increased by 1 or more in 60% of the identified tumors. CONCLUSION: Gains in sensitivity with the dual-head system molecular breast imaging are partially due to increased confidence in lesion detection. Molecular breast imaging can reliably detect breast lesions < 2 cm and dual-head molecular breast imaging can significantly increase sensitivity for subcentimeter lesions.

Scientific Impact Recognition Award: Molecular breast imaging: a review of the Mayo Clinic experience.

BACKGROUND: Molecular breast imaging (MBI) depicts functional uptake of targeted radiotracers in the breast using dedicated gamma cameras. METHODS: MBI studies were performed under several institutional protocols evaluating the use of MBI in screening and diagnosis. RESULTS: By using a single-head system, sensitivity for breast cancer detection was 85% (57 of 67) overall and 29% for tumors 5 mm or less in diameter. Sensitivity improved to 91% (117 of 128) overall and 69% for tumors 5 mm or less using a dual-head system. In 650 high-risk patients undergoing breast cancer screening, MBI detected 7 cancers, 5 of which were missed on mammography. In 24 of 149 (16%) breast cancer patients MBI detected additional disease not seen on mammography. The sensitivity of MBI was 88% (83 of 94) for invasive ductal carcinoma, 79% (23 of 29) for invasive lobular carcinoma, and 89% (25 of 28) for ductal carcinoma in situ. CONCLUSIONS: MBI can detect invasive ductal carcinoma, ductal carcinoma in situ, and invasive lobular carcinoma. It has a promising role in evaluating the extent of disease and multifocal disease in the breast for surgical treatment planning.

Molecular breast imaging: advantages and limitations of a scintimammographic technique in patients with small breast tumors.

Preliminary studies from our laboratory showed that molecular breast imaging (MBI) can reliably detect tumors <2 cm in diameter. This study extends our work to a larger patient population and examines the technical factors that influence the ability of MBI to detect small breast tumors. Following injection of 740 MBq Tc-99m sestamibi, MBI was performed on 100 patients scheduled for biopsy of a lesion suspicious for malignancy that measured <2 cm on mammography or sonography. Using a small field of view gamma camera, patients were imaged in the standard mammographic views using light pain-free compression. Subjective discomfort, breast thickness, the amount of breast tissue in the detector field of view, and breast counts per unit area were measured and recorded. Follow-up was obtained in 99 patients; 53 patients had 67 malignant tumors confirmed at surgery. Of these, 57 of 67 were detected by MBI (sensitivity 85%). Sensitivity was 29%, 86%, and 97% for tumors <5, 6-10, and > or =11 mm in diameter, respectively. In seven patients, MBI identified eight additional mammographically occult tumors. Of 47 patients with no evidence of cancer at biopsy or surgery, there were 36 true negative and 11 false positive scans on MBI. MBI has potential for the regular detection of malignant breast tumors less than 2 cm in diameter. Work in progress to optimize the imaging parameters and technique may further improve sensitivity and specificity.

Molecular breast imaging: a new technique using technetium Tc 99m scintimammography to detect small tumors of the breast.

OBJECTIVE: To determine the sensitivity of molecular breast imaging (MBI) to detect small cancers of the breast. PATIENTS AND METHODS: A cadmium-zinc-telluride gamma camera with a field of view of 20 x 20 cm was used. The detector elements were 2.5 x 2.5 mm. The gamma camera was mounted on a modified mammographic gantry. Between November 2001 and March 2004, we performed MBI on patients who were scheduled to undergo biopsy for a lesion suggestive of malignancy that was smaller than 2 cm on a mammogram. Patients were injected with 20 mCi of technetium Tc 99m sestamibi and underwent imaging immediately after injection. Using light pain-free compression, we obtained craniocaudal and mediolateral oblique views of each breast. RESULTS: Of the 40 women included in the study, 26 had a total of 36 malignant lesions confirmed at surgery. Of these 36 lesions, 33 were detected by MBI (overall sensitivity, 92%). Of the 22 malignant lesions 1 cm or smaller in diameter, 19 were detected by MBI (sensitivity, 86%). Two patients had false-negative MBI results. Of the 14 malignant lesions larger than 1 cm in diameter, all were identified correctly by MBI. In 4 patients, MBI identified additional lesions not seen on mammography that were confirmed subsequently on magnetic resonance imaging and were true-positive cases at surgery. Three of these patients had lesions in the breast contralateral to the breast containing the initial mammographic finding suggestive of malignancy. Of 14 patients with no evidence of cancer at biopsy or surgery, 9 had true-negative (normal) scans and 5 had false-positive scans on MBI. False-positive results included benign fibroadenoma (2 patients), inflammatory fat necrosis (1 patient), benign breast parenchyma (1 patient), and complex sclerosing lesion (1 patient). CONCLUSION: This prototype gamma camera system for MBI reliably detects malignant breast lesions smaller than 2 cm. Furthermore, we obtained the highest sensitivity (86%) yet reported for the detection of lesions smaller than 1 cm. These results suggest an important role for MBI, particularly for women in whom the sensitivity of mammography is reduced by the density of the breast parenchyma.

Primary mammary (non-Hodgkin) lymphoma presenting as locally advanced breast cancer.

Primary mammary lymphoma is a rare tumor that presents commonly as a large mass with no specific mammographic appearance and can be confused with poorly differentiated carcinoma on frozen section. With appropriate treatment, this breast malignancy has a relatively good prognosis. We report a case of primary mammary non-Hodgkin lymphoma in a 74-year-old woman that originally presented as locally advanced breast cancer with secondary inflammatory skin changes. Clinical findings, diagnostic work-up, and follow-up are provided along with a review of the literature on primary mammary lymphoma.

Evaluation of a small cadmium zinc telluride detector for scintimammography.

UNLABELLED: The purpose of this study was to evaluate a small semiconductor-based gamma camera that may have applications in scintimammography. METHODS: A small cadmium zinc telluride (CZT) detector was evaluated. The detector had a field of view of 20 x 20 cm with detector elements of 2.5 x 2.5 mm in size. Both short-bore (35 mm) and long-bore (50 mm) collimators, matched to the geometry of the detector elements, were evaluated. The imaging performance of the CZT detector was compared with that of a conventional gamma camera equipped with all-purpose and ultra-high-resolution collimators. The performance of both systems with respect to breast imaging was evaluated using a water tank containing small glass spheres, 1.8-9.8 mm in diameter. The effects of variations in breast thickness, tumor depth, and tumor-to-background ratio were all simulated in this phantom model. Total counts per image were adjusted to approximate the count density observed in clinical scintimammographic studies. RESULTS: Sensitivity of the CZT detector was 76% that of the equivalent NaI system. The system demonstrated excellent integral uniformity. The energy resolution of the CZT system was 6.5% for (99m)Tc. Spatial resolution with the long-bore collimator was superior to that of a conventional large field-of -view gamma camera equipped with an ultra-high- resolution collimator, over the range 0-6 cm from the collimator face. A blinded review of breast phantom images showed that small spheres (< or =7 mm in diameter) were better seen and had a better tumor-to-background ratio with the CZT system than with the conventional gamma camera. CONCLUSION: A small CZT detector offers superior performance to a conventional gamma camera and should permit reliable detection of breast tumors <1 cm in size.