Occult breast cancer: scintimammography with high-resolution breast-specific gamma camera in women at high risk for breast cancer

Diagnostic performance of a novel high-resolution dedicated axillary PET system in the assessment of regional nodal spread of disease in early breast cancer

Background

In early breast cancer, a non-invasive method with higher sensitivity and negative predictive value (NPV) is needed to identify and recognize more indolent axillary lymph nodes (ALNs). This study aimed to assess whether a novel high-resolution dedicated ALN positron emission tomography (LymphPET) system could improve sensitivity in detecting early breast cancer (clinical N0-N1 stage).

Methods

A total of 103 patients with clinical stage T1-2N0-1M0 breast cancer were evaluated by ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) LymphPET. The maximum single-voxel PET uptake value of ALNs (maxLUV) and the tumor-to-background ratio (TBR) for fat (TBR1) and muscle (TBR2) tissue were calculated. Then, 78 patients with cN0 stage breast cancer received sentinel lymph node biopsy alone or combined with axillary lymph node dissection (ALND), and 25 patients with cN1 stage breast cancer underwent fine-needle aspiration.

Results

A total of 99 invasive breast carcinoma cases were included in this study. The diagnostic sensitivity of LymphPET was 88%, specificity was 79%, false-negative rate was 12%, the false-positive rate was 21%, positive predictive value was 75%, NPV was 90%, and accuracy was 83%. The maxLUV was superior to TBR1 and TBR2 in detecting ALNs, with 0.27 being the most optimal cutoff value.

Conclusions

The ¹⁸F-FDG LymphPET system can be used to identify and recognize more indolent ALNs of breast cancer due to greater sensitivity and a much higher NPV.

Diagnostic Performance of MRI, Molecular Breast Imaging, and Contrast-enhanced Mammography in Women with Newly Diagnosed Breast Cancer

Background Staging newly diagnosed breast cancer by using dynamic contrast material-enhanced MRI is limited by access, high cost, and false-positive findings. The utility of contrast-enhanced mammography (CEM) and ^99mTc sestamibi-based molecular breast imaging (MBI) in this setting is largely unknown. Purpose To compare extent-of-disease assessments by using MRI, CEM, and MBI versus pathology in women with breast cancer. Materials and Methods In this HIPAA-compliant prospective study, women with biopsy-proven breast cancer underwent MRI, CEM, and MBI between October 2014 and April 2018. Eight radiologists independently interpreted each examination result prospectively and were blinded to interpretations of findings with the other modalities. Visibility of index malignancies, lesion size, and additional suspicious lesions (malignant or benign) were compared during pathology review. Accuracy of index lesion sizing and detection of additional lesions in women without neoadjuvant chemotherapy were compared. Results A total of 102 women were enrolled and 99 completed the study protocol (mean age, 51 years ± 11 [standard deviation]; range, 32-77 years). Lumpectomy or mastectomy was performed in 71 women (79 index malignancies) without neoadjuvant chemotherapy and in 28 women (31 index malignancies) with neoadjuvant chemotherapy. Of the 110 index malignancies, MRI, CEM, and MBI depicted 102 (93%; 95% confidence interval [CI]: 86%, 97%), 100 (91%; 95% CI: 84%, 96%), and 101 (92%; 95% CI: 85%, 96%) malignancies, respectively. In patients without neoadjuvant chemotherapy, pathologic size of index malignancies was overestimated with all modalities (P = .02). MRI led to overestimation of 24% (17 of 72) of malignancies by more than 1.5 cm compared with 11% (eight of 70) with CEM and 15% (11 of 72) with MBI. MRI depicted more (P = .007) nonindex lesions, with sensitivity similar to that of CEM or MBI, resulting in lower positive predictive value of additional biopsies (13 of 46 [28%; 95% CI: 17%, 44%] for MRI; 14 of 27 [52%; 95% CI: 32%, 71%] for CEM; and 11 of 25 [44%; 95% CI: 24%, 65%] for MBI (overall P = .01). Conclusion Contrast-enhanced mammography, molecular breast imaging, and MRI showed similar detection of all malignancies. MRI depicted more nonindex suspicious benign lesions than did contrast-enhanced mammography or molecular breast imaging, leading to lower positive predictive value of additional biopsies. All three modalities led to overestimation of index tumor size, particularly MRI. © RSNA, 2019 Online supplemental material is available for this article.

Application of Imaging Technologies in Breast Cancer Detection: A Review Article

One of the techniques utilised in the management of cancer in all stages is multiple biomedical imaging. Imaging as an important part of cancer clinical protocols can provide a variety of information about morphology, structure, metabolism and functions. Application of imaging technics together with other investigative apparatus including in fluids analysis and vitro tissue would help clinical decision-making. Mixed imaging techniques can provide supplementary information used to improve staging and therapy planning. Imaging aimed to find minimally invasive therapy to make better results and reduce side effects. Probably, the most important factor in reducing mortality of certain cancers is an early diagnosis of cancer via screening based on imaging. The most common cancer in women is breast cancer. It is considered as the second major cause of cancer deaths in females, and therefore it remained as an important medical and socio-economic issue. Medical imaging has always formed part of breast cancer care and has used in all phases of cancer management from detection and staging to therapy monitoring and post-therapeutic follow-up. An essential action to be performed in the preoperative staging of breast cancer based on breast imaging. The general term of breast imaging refers to breast sonography, mammography, and magnetic resonance tomography (MRT) of the breast (magnetic resonance mammography, MRM).

Further development in technology will lead to increase imaging speed to meet physiological processes requirements. One of the issues in the diagnosis of breast cancer is sensitivity limitation. To overcome this limitation, complementary imaging examinations are utilised that traditionally includes screening ultrasound, and combined mammography and ultrasound. Development in targeted imaging and therapeutic agents calls for close cooperation among academic environment and industries such as biotechnological, IT and pharmaceutical industries.

Performance evaluation of a high resolution dedicated breast PET scanner

PURPOSE

Early stage breast cancers may not be visible on a whole-body PET scan. To overcome whole-body PET limitations, several dedicated breast positron emission tomography (DbPET) systems have emerged nowadays aiming to improve spatial resolution. In this work the authors evaluate the performance of a high resolution dedicated breast PET scanner (Mammi-PET, Oncovision).

METHODS

Global status, uniformity, sensitivity, energy, and spatial resolution were measured. Spheres of different sizes (2.5, 4, 5, and 6 mm diameter) and various 18 fluorodeoxyglucose ((18)F-FDG) activity concentrations were randomly inserted in a gelatine breast phantom developed at our institution. Several lesion-to-background ratios (LBR) were simulated, 5:1, 10:1, 20:1, 30:1, and 50:1. Images were reconstructed using different voxel sizes. The ability of experienced reporters to detect spheres was tested as a function of acquisition time, LBR, sphere size, and matrix reconstruction voxel size. For comparison, phantoms were scanned in the DbPET camera and in a whole body PET (WB-PET). Two patients who just underwent WB-PET/CT exams were imaged with the DbPET system and the images were compared.

RESULTS

The measured absolute peak sensitivity was 2.0%. The energy resolution was 24.0% ± 1%. The integral and differential uniformity were 10% and 6% in the total field of view (FOV) and 9% and 5% in the central FOV, respectively. The measured spatial resolution was 2.0, 1.9, and 1.7 mm in the radial, tangential, and axial directions. The system exhibited very good detectability for spheres ≥4 mm and LBR ≥10 with a sphere detection of 100% when acquisition time was set >3 min/bed. For LBR = 5 and acquisition time of 7 min the detectability was 100% for spheres of 6 mm and 75% for spheres of 5, 4, and 2.5 mm. Lesion WB-PET detectability was only comparable to the DbPET camera for lesion sizes ≥5 mm when acquisition time was >3 min and LBR > 10.

CONCLUSIONS

The DbPET has a good performance for its clinical use and shows an improved resolution and lesion detectability of small lesions compared to WB-PET.

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

OBJECTIVE

The purposes of this review are to discuss the motivation for supplemental screening, to address molecular breast imaging (MBI) radiation dose concerns, and to provide an updated guide to current MBI technology, clinical protocols, and screening performance. Future directions of MBI are also discussed.

CONCLUSION

MBI offers detection of mammographically occult cancers in women with dense breasts. Although MBI has been under investigation for nearly 15 years, it has yet to gain widespread adoption in breast screening.

Benefit to Radiation Risk of Breast-specific Gamma Imaging Compared with Mammography in Screening Asymptomatic Women with Dense Breasts

Purpose To estimate the benefit-to-radiation risk ratios of mammography alone, breast-specific gamma imaging (BSGI) alone, and mammography plus BSGI in women with dense breasts who were asymptomatic and examined in the 2015 study by Rhodes et al. Materials and Methods This study uses previously published breast cancer detection rates and estimates of radiation dose and radiation risk and is, therefore, exempt from institutional review board approval. By using breast cancer detection rates for mammography alone, BSGI alone, and mammography plus BSGI from the study by Rhodes et al, as well as lifetime estimates of radiation-induced cancer mortality for mammography and BSGI on the basis of the Biologic Effects of Ionizing Radiation VII report, the benefit-to-radiation risk ratios of mammography alone, BSGI alone, and mammography plus BSGI performed annually over 10-year age intervals from ages 40 to 79 years are estimated. Results The benefit-to-radiation risk ratio is estimated to be 13 for women who are 40-49 years old and are screened with mammography, a figure that approximately doubles for each subsequent 10-year age interval up to 70-79 years old. For low-dose BSGI, annual screening benefit-to-radiation risk ratios are estimated to be 5 for women 40-49 years old and to double by age 70-79 years, while mammography plus BSGI has benefit-to-radiation risk ratios similar to those of BSGI alone. There are wide ranges for all of these estimates. Conclusion While lower dose (300 MBq) BSGI has estimated benefit-to-radiation risk ratios well in excess of 1 for screening of asymptomatic women with dense breasts who are 40 years old and older, it does not match the benefit-to-radiation risk ratio of screening mammography. ^© RSNA, 2016.

Validity of breast-specific gamma imaging for Breast Imaging Reporting and Data System 4 lesions on mammography and/or ultrasound

Purpose

The purpose of this study was to assess the breast-specific gamma imaging (BSGI) in Breast Imaging Reporting and Data System (BI-RADS) 4 lesions on mammography and/or ultrasound.

Methods

We performed a retrospective review of 162 patients who underwent BSGI in BI-RADS 4 lesions on mammography and/or ultrasound.

Results

Of the 162 breast lesions, 66 were malignant tumors and 96 were benign tumors. Sensitivity and specificity of BSGI were 90.9% and 78.1%, and positive predictive value and negative predictive value were 74.1% and 92.6%. The sensitivity or specificity of mammography and ultrasound were 74.2% and 56.3% and 87.9% and 19.8%, respectively. The sensitivity and specificity of BSGI for breast lesions ≤1 cm were 88.0% and 86.8%, while the values of beast lesions >1 cm were 92.7% and 61.5%. The sensitivity or specificity of BSGI and mammography for patients with dense breasts were 92.0% and 81.3% and 72.0% and 50.0%, respectively. 26 patients showed neither a nodule nor microcalcification on ultrasound, but showed suspicious calcification on mammography. The sensitivity and specificity of BSGI with microcalcification only lesion were 75.0% and 94.4%.

Conclusion

This study demonstrated that BSGI had shown high sensitivity and specificity, as well as positive and negative predictive values in BI-RADS 4 lesions on ultrasound and/or mammography. BSGI showed excellent results in dense breasts, in lesions that are less than 1 cm in size and lesions with suspicious microcalcification only.

Comparison of breast specific gamma imaging and molecular breast tomosynthesis in breast cancer detection: Evaluation in phantoms

PURPOSE

Breast specific gamma imaging or molecular breast imaging (BSGI) obtains 2D images of (99m)Tc sestamibi distribution in the breast. Molecular breast tomosynthesis (MBT) maps the tracer distribution in 3D by acquiring multiple projections over a limited angular range. Here, the authors compare the performance of the two technologies in terms of spatial resolution, lesion contrast, and contrast-to-noise ratio (CNR) in phantom studies under conditions of clinically relevant sestamibi dose and imaging time.

METHODS

The systems tested were a Dilon 6800 and a MBT prototype developed at the University of Virginia. Both systems comprise a pixelated sodium iodide scintillator, an array of position sensitive photomultipliers, and a parallel hole collimator. The active areas and energy resolution of the systems are similar. System sensitivity, spatial resolution, lesion contrast, and CNR were measured using a Petri dish, a point source phantom, and a breast phantom containing simulated lesions at two depths, respectively. A single BSGI projection was acquired. Five MBT projections were acquired over ±20°. For both modalities, the total scan count density was comparable to that observed for each in typical 10 min human scans following injection of 22 mCi (814 MBq) of (99m)Tc-sestamibi. To assess the impact of reducing the tracer dose, the pixel counts of projection images were later binomially subsampled by a factor of 2 to give images corresponding to an injected activity of approximately 11 mCi (407 MBq). Both unprocessed (pixelated) BSGI projections and interpolated (smoothed) BSGI images displayed by default on the Dilon 6800 workstation were analyzed. Volumetric images were reconstructed from the MBT projections using a maximum likelihood expectation maximization algorithm and extracted slices were analyzed.

RESULTS

Over a depth range of 1.5-7.5 cm, BSGI spatial resolution was 5.6-11.5 mm in unprocessed projections and 5.7-12.0 mm in interpolated images. Over the same range, the in-slice MBT spatial resolution was 6.7-9.4 mm. Lesion contrast was significantly improved with MBT relative to BSGI for five out of eight lesions imaged at either the 22 mCi or the 11 mCi dose level (p < 0.05). At both dose levels, significant improvements in CNR with MBT were also found for five out of eight lesions (9.8, 7.8, 6.2 mm lesions at water depth of 1.7 cm and 9.8, 7.8 mm lesions at water depth of 4.5 cm, p < 0.05). The 6.2 and 4.9 mm lesions located at 4.5 cm below the water surface were not visible in either modality at either activity level.

CONCLUSIONS

Under conditions of equal dose, imaging time and similar detectors, compared to BSGI, MBT provided higher lesion contrast, higher CNR, and spatial resolution that was less depth dependent.

Breast-Specific γ-Imaging for the Detection of Mammographically Occult Breast Cancer in Women at Increased Risk

Breast-specific γ-imaging (BSGI) is a physiologic imaging modality that can detect subcentimeter and mammographically occult breast cancer, with a sensitivity and specificity comparable to MRI. The purpose of this study was to determine the incremental increase in breast cancer detection when BSGI is used as an adjunct to mammography in women at increased risk for breast cancer.

METHODS

All patients undergoing BSGI from April 2010 through January 2014 were retrospectively reviewed. Eligible patients were identified as women at increased risk for breast cancer and whose most recent mammogram was benign. Examinations exhibiting focally increased radiotracer uptake were considered positive. Incremental increase in cancer detection was calculated as the percentage of mammographically occult BSGI-detected breast cancer and the number of mammographically occult breast cancers detected per 1,000 women screened.

RESULTS

Included in this study were 849 patients in whom 14 BSGI examinations detected mammographically occult breast cancer. Patients ranged in age from 26 to 83 y, with a mean age of 57 y. Eleven of 14 cancers were detected in women with dense breasts. The addition of BSGI to the annual breast screen of asymptomatic women at increased risk for breast cancer yields 16.5 cancers per 1,000 women screened. When high-risk lesions and cancers were combined, BSGI detected 33.0 high-risk lesions and cancers per 1,000 women screened.

CONCLUSION

BSGI is a reliable adjunct modality to screening mammography that increases breast cancer detection by 1.7% (14/849) in women at increased risk for breast cancer, comparable to results reported for breast MRI. BSGI is beneficial in breast cancer detection in women at increased risk, particularly in those with dense breasts.

Comparative Diagnostic Utility of Low-Dose Breast-Specific Gamma Imaging to Current Clinical Standard

To retrospectively compare low-dose (7-10 mCi) to high-dose (15-30 mCi) breast-specific gamma imaging (BSGI) in the detection of breast cancer. A retrospective review of 223 consecutive women who underwent BSGI exam between February 2011 and August 2013 with subsequent pathologic analysis was performed. Women were divided into low-dose and high-dose groups. The results of BSGI and pathology were compared, and the sensitivity, positive predictive value (PPV), and negative predictive value (NPV) were determined. A subgroup analysis was performed to evaluate specificity using benign follow-up imaging to establish true-negative results. There were 223 women who met inclusion criteria with 109 patients with 153 lesions in the low-dose group and 114 patients with 145 lesions in the high-dose group. Pathologic correlation demonstrates sensitivities of 97.6% (95% CI = 90.9-99.6%) and 94.6% (95% CI = 84.2-98.6%; p = 0.093), PPVs of 62.1% (95% CI = 53.2-70.3%) and 50.5% (95% CI = 40.6-60.3%, p = 0.089), and NPVs of 90.5% (95% CI = 68.2-98.3%) and 92.5% (95% CI = 78.5-98.0%, p = 0.781) in the low-dose and high-dose groups, respectively. Subgroup analysis included 72 patients with 98 lesions in the low-dose group and 116 patients with 132 lesions in the high-dose group, with a specificity of 53.7% (95% CI = 39.7-67.1%) and 66.3% (95% CI = 56.2-75.2%%, p = 0.143), respectively. Low-dose BSGI demonstrated high sensitivity and NPV in the detection of breast cancer comparable to the current standard dose BSGI, with moderate specificity and PPV in a limited subgroup analysis, which was associated with a substantial number of false-positives.

Added value of semi-quantitative breast-specific gamma imaging in the work-up of suspicious breast lesions compared to mammography, ultrasound and 3-T MRI

OBJECTIVE

To prospectively analyse the diagnostic value of semi-quantitative breast-specific gamma imaging (BSGI) in the work-up of suspicious breast lesions compared with that of mammography (MG), breast ultrasound and MRI of the breast.

METHODS

Within a 15-month period, 67 patients with 92 breast lesions rated as Category IV or V according to the breast imaging reporting and data system detected with MG and/or ultrasound were included into the study. After the injection of 740-1110 MBq of Technetium-99m ((99m)Tc) SestaMIBI intravenously, scintigrams were obtained in two projections comparable to MG. The BSGI was analysed visually and semi-quantitatively by calculating a relative uptake factor (X). With the exception of two patients with cardiac pacemakers, all patients underwent 3-T breast MRI. Biopsy results were obtained as the reference standard in all patients. Sensitivity, specificity, positive- and negative-predictive values, accuracy and area under the curve were calculated for each modality.

RESULTS

Among the 92 lesions, 67 (72.8%) were malignant. 60 of the 67 cancers of any size were detected by BSGI with an overall sensitivity of 90%, only exceeded by ultrasound with a sensitivity of 99%. The sensitivity of BSGI for lesions <1 cm declined significantly to 60%. Overall specificity of ultrasound was only 20%. Specificity, accuracy and positive-predictive value were the highest for BSGI (56%, 80% and 85%, respectively). X was significantly higher for malignant lesions (mean, 4.27) and differed significantly between ductal types (mean, 4.53) and the other histopathological entities (mean, 3.12).

CONCLUSION

Semi-quantitative BSGI with calculation of the relative uptake factor (X) can help to characterize breast lesions. BSGI negativity may obviate the need for biopsy of breast lesions >1 cm with low or intermediate prevalence for malignancy.

ADVANCES IN KNOWLEDGE

Compared with morphological imaging modalities, specificity, positive-predictive value for malignancy and accuracy were the highest for BSGI in our study. BSGI negativity may support the decision not to biopsy in selected lesions with a low or low-to-moderate pre-test probability for malignancy.

Alternative screening for women with dense breasts: breast-specific gamma imaging (molecular breast imaging)

OBJECTIVE. Given mammography's limitations in evaluating dense breasts, examination with breast-specific gamma imaging (BSGI)-also called molecular breast imaging (MBI)-has been proposed. We review the literature pertinent to the performance of BSGI in patients with dense breasts. CONCLUSION. Many studies have reported the sensitivity of BSGI in finding cancers even in dense breasts. However, BSGI has not yet been validated as an effective screening tool in large prospective studies. In addition, whole-body dose remains a significant concern.

Breast cancer screening controversies: who, when, why, and how?

Mammographic screening is effective in reducing mortality from breast cancer. The issue is not whether mammography is effective, but whether the false positive rate and false negative rates can be reduced. This review will discuss controversies including the reduction in breast cancer mortality, overdiagnosis, the ideal screening candidate, and the optimal imaging modality for breast cancer screening. The article will compare and contrast screening mammography, tomosynthesis, whole-breast screening ultrasound, magnetic resonance imaging, and molecular breast imaging. Though supplemental imaging modalities are being utilized to improve breast cancer diagnosis, mammography still remains the gold standard for breast cancer screening.

Diagnostic workup and costs of a single supplemental molecular breast imaging screen of mammographically dense breasts

OBJECTIVE

The purpose of this study was to examine additional diagnostic workup and costs generated by addition of a single molecular breast imaging (MBI) examination to screening mammography for women with dense breasts.

SUBJECTS AND METHODS

Women with mammographically dense breasts presenting for screening mammography underwent adjunct MBI performed with 300 MBq (99m)Tc-sestamibi and a direct-conversion cadmium-zinc-telluride dual-head gamma camera. All subsequent imaging tests and biopsies were tracked for a minimum of 1 year. The positive predictive value of biopsies performed (PPV3), benign biopsy rate, cost per patient screened, and cost per cancer detected were determined.

RESULTS

A total of 1651 women enrolled in the study. Among the 1585 participants with complete reference standard, screening mammography alone prompted diagnostic workup of 175 (11.0%) patients and biopsy of 20 (1.3%) and yielded five malignancies (PPV3, 25%). Results of combined screening mammography plus MBI prompted diagnostic workup of 279 patients (17.6%) and biopsy of 67 (4.2%) and yielded 19 malignancies (PPV3, 28.4%). The benign biopsy rates were 0.9% (15 of 1585) for screening mammography alone and 3.0% (48 of 1585) for the combination (p < 0.001). The addition of MBI increased the cost per patient screened from $176 for mammography alone to $571 for the combination. However, cost per cancer detected was lower for the combination ($47,597) than for mammography alone ($55,851).

CONCLUSION

The addition of MBI to screening mammography of women with dense breasts increased the overall costs and benign biopsy rate but also increased the cancer detection rate, which resulted in a lower cost per cancer detected than with screening mammography alone.

[Molecular breast imaging. An update]

CLINICAL/METHODICAL ISSUE

The aim of molecular imaging is to visualize and quantify biological, physiological and pathological processes at cellular and molecular levels. Molecular imaging using various techniques has recently become established in breast imaging.

STANDARD RADIOLOGICAL METHODS

Currently molecular imaging techniques comprise multiparametric magnetic resonance imaging (MRI) using dynamic contrast-enhanced MRI (DCE-MRI), diffusion-weighted imaging (DWI), proton MR spectroscopy ((1)H-MRSI), nuclear imaging by breast-specific gamma imaging (BSGI), positron emission tomography (PET) and positron emission mammography (PEM) and combinations of techniques (e.g. PET-CT and multiparametric PET-MRI).

METHODICAL INNOVATIONS

Recently, novel techniques for molecular imaging of breast tumors, such as sodium imaging ((23)Na-MRI), phosphorus spectroscopy ((31)P-MRSI) and hyperpolarized MRI as well as specific radiotracers have been developed and are currently under investigation.

PRACTICAL RECOMMENDATIONS

It can be expected that molecular imaging of breast tumors will enable a simultaneous assessment of the multiple metabolic and molecular processes involved in cancer development and thus an improved detection, characterization, staging and monitoring of response to treatment will become possible.

99mTc-sestamibi using a direct conversion molecular breast imaging system to assess tumor response to neoadjuvant chemotherapy in women with locally advanced breast cancer

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).

METHODS

Patients undergoing NAC for breast cancer were imaged with a direct conversion-MBI system before (baseline), at 3 to 5 weeks after onset, and after completion of NAC. Tumor size and tumor-to-background (T/B) uptake ratio measured from MBI images were compared with extent of residual disease at surgery using the residual cancer burden.

RESULTS

Nineteen patients completed imaging and proceeded to surgical resection after NAC. Mean reduction in T/B ratio from baseline to 3 to 5 weeks for patients classified as RCB-0 (no residual disease), RCB-1 and RCB-2 combined, and RCB-3 (extensive residual disease) was 56% (SD, 0.20), 28% (SD, 0.20), and 4% (SD, 0.15), respectively. The reduction in the RCB-0 group was significantly greater than in RCB-1/2 (P = 0.036) and RCB-3 (P = 0.001) groups. The area under the receiver operator characteristic curve for determining the presence or absence of residual disease was 0.88. Using a threshold of 50% reduction in T/B ratio at 3 to 5 weeks, MBI predicted presence of residual disease at surgery with a diagnostic accuracy of 89.5% (95% confidence interval [CI], 0.64%-0.99%), sensitivity of 92.3% (95% CI, 0.74%-0.99%), and specificity of 83.3% (95% CI, 0.44%-0.99%). The reduction in tumor size at 3 to 5 weeks was not statistically different between RCB groups.

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.

Invasive ductal carcinoma arising from dense accessory breast visualized with 99mTc-MIBI breast-specific γ imaging

Primary accessory breast cancer is extremely rare, and the diagnostic efficacy of Tc-MIBI breast-specific γ imaging (BSGI) has not been reported elsewhere. We present a case of primary carcinoma arising from dense accessory breast that was visualized with BSGI. A 43-year-old female patient with a palpable axillary mass underwent mammography, which showed dense parenchyma on both of the anatomic and accessory breasts with no abnormality. Subsequent BSGI showed no abnormal uptake in bilateral anatomic breasts, but focal abnormal uptake was noted in the accessory breast. Permanent pathologic evaluation confirmed invasive ductal carcinoma (not otherwise specified type) of the accessory breast.

Radionuclide methods and instrumentation for breast cancer detection and diagnosis

Breast cancer mammography is a well-acknowledged technique for patient screening due to its high sensitivity. However, in addition to its low specificity the sensitivity of mammography is limited when imaging patients with dense breasts. Radionuclide imaging techniques, such as coincidence photon-based positron emission tomography and single photon emission computed tomography or scintimammography, can play a role in assisting screening of such patients. Radionuclide techniques can also be useful in assessing treatment response of patients with breast cancer to therapy, and staging of patients to diagnose the disease extent. However, the performance of these imaging modalities is generally limited because of the poor spatial resolution and sensitivity of the commercially available multipurpose imaging systems. Here, we describe some of the dedicated imaging systems (positron emission mammography [PEM] and breast-specific gamma imaging [BSGI]) that have been developed both commercially and in research laboratories for radionuclide imaging of breast cancer. Clinical studies with dedicated PEM scanners show improved sensitivity to detecting cancer in patients when using PEM in conjunction with additional imaging modalities, such as magnetic resonance imaging or mammography or both, as well as improved disease staging that can have an effect on surgical planning. High-resolution BSGI systems are more widely available commercially and several clinical studies have shown very high sensitivity and specificity in detecting cancer in high-risk patients. Further development of dedicated PEM and BSGI systems is ongoing, promising further expansion of radionuclide imaging techniques in the realm of breast cancer detection and treatment.

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

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.

Collimator design for a dedicated molecular breast imaging-guided biopsy system: proof-of-concept

PURPOSE

Molecular breast imaging (MBI) is a dedicated nuclear medicine breast imaging modality that employs dual-head cadmium zinc telluride (CZT) gamma cameras to functionally detect breast cancer. MBI has been shown to detect breast cancers otherwise occult on mammography and ultrasound. Currently, a MBI-guided biopsy system does not exist to biopsy such lesions. Our objective was to consider the utility of a novel conical slant-hole (CSH) collimator for rapid (<1 min) and accurate monitoring of lesion position to serve as part of a MBI-guided biopsy system.

METHODS

An initial CSH collimator design was derived from the dimensions of a parallel-hole collimator optimized for MBI performed with dual-head CZT gamma cameras. The parameters of the CSH collimator included the collimator height, cone slant angle, thickness of septa and cones of the collimator, and the annular areas exposed at the base of the cones. These parameters were varied within the geometric constraints of the MBI system to create several potential CSH collimator designs. The CSH collimator designs were evaluated using Monte Carlo simulations. The model included a breast compressed to a thickness of 6 cm with a 1-cm diameter lesion located 3 cm from the collimator face. The number of particles simulated was chosen to represent the count density of a low-dose, screening MBI study acquired with the parallel-hole collimator for 10 min after a ∼150 MBq (4 mCi) injection of Tc-99m sestamibi. The same number of particles was used for the CSH collimator simulations. In the resulting simulated images, the count sensitivity, spatial resolution, and accuracy of the lesion depth determined from the lesion profile width were evaluated.

RESULTS

The CSH collimator design with default parameters derived from the optimal parallel-hole collimator provided 1-min images with error in the lesion depth estimation of 1.1 ± 0.7 mm and over 21 times the lesion count sensitivity relative to 1-min images acquired with the current parallel-hole collimator. Sensitivity was increased via more vertical cone slant angles, larger annular areas, thinner cone walls, shorter cone heights, and thinner radiating septa. Full width at half maximum trended in the opposite direction as sensitivity for all parameters. There was less error in the depth estimates for less vertical slant angles, smaller annular areas, thinner cone walls, cone heights near 1 cm, and generally thinner radiating septa.

CONCLUSIONS

A Monte Carlo model was used to demonstrate the feasibility of a CSH collimator design for rapid biopsy application in molecular breast imaging. Specifically, lesion depth of a 1-cm diameter lesion positioned in the center of a typical breast can be estimated with error of less than 2 mm using circumferential count profiles of images acquired in 1 min.

Contrast-noise-ratio (CNR) analysis and optimisation of breast-specific gamma imaging (BSGI) acquisition protocols

BACKGROUND

Breast cancer is one of the most prevalent forms of cancer in women. Breast-specific gamma imaging (BSGI) is a diagnostic imaging method that uses sestamibi-labelled 99Tc and a dedicated gamma camera to localize malignant lesions in breast tissue. The aim of this study is to investigate if the current acquisition protocol for BSGI at our hospital is optimized for the detection of lesions in our patients.

METHODS

We analyzed patient data and performed a phantom study with a Dilon 6800 gamma camera. The patient data were collected from a group of 13 patients (740 MBq 99mTc-sestamibi, four views per patient were dynamically acquired with a frame duration of 30 s per frame and a total acquisition time of 8 min per view). Reduced-time static images were created, and contrast-to-noise ratios of identified hotspots were determined for different acquisition times. For the phantom study, we used a contrast detail phantom to investigate the contrast and resolution properties, within the range of relevant clinical acquisition parameters. The phantom was filled with a concentration of 80 MBq in 500 ml of water, and we dynamically acquired frames for a total acquisition time of 60 min using a general purpose (GP) collimator. To compare the GP collimator with the high-resolution collimator, a second acquisition was made for both collimators with a total acquisition time of 16 min.

RESULTS

The initial analysis of BSGI scans of the 13 patients showed that a dose reduction by a factor of 3 would not have reduced the number of observable hotspots in each of the acquired views. However, a subsequent systematic analysis of our protocol with a contrast-detail phantom showed that dose reduction results in a lower observability of hotspots, whereas increased doses resulted in a higher observability.

CONCLUSION

We believe that the results of our phantom study are relevant for clinical practice and that further dose reduction cannot be recommended for the BSGI exams at our hospital and that an increase of the administered activity should be considered.

Clinical usefulness of breast-specific gamma imaging as an adjunct modality to mammography for diagnosis of breast cancer: a systemic review and meta-analysis

PURPOSE

The purpose of this study was to assess the diagnostic performance of breast-specific gamma imaging (BSGI) as an adjunct modality to mammography for detecting breast cancer.

METHODS

Comprehensive searches of MEDLINE (1984 to August 2012) and EMBASE (1994 to August 2012) were performed. A summary receiver operating characteristic curve (SROC) was constructed to summarize the overall test performance of BSGI. The sensitivities for detecting subcentimetre cancer and ductal carcinoma in situ (DCIS) were pooled. The potential of BSGI to complement mammography was also evaluated by identifying mammography-occult breast cancer.

RESULTS

Analysis of the studies revealed that the overall validity estimates of BSGI in detecting breast cancer were as follows: sensitivity 95 % (95 % CI 93-96 %), specificity 80 % (95 % CI 78-82 %), positive likelihood ratio 4.63 (95 % CI 3.13-6.85), negative likelihood ratio 0.08 (95 % CI 0.05-0.14), and diagnostic odds ratio 56.67 (95 % CI 26.68-120.34). The area under the SROC was 0.9552 and the Q* point was 0.8977. The pooled sensitivities for detecting subcentimetre cancer and DCIS were 84 % (95 % CI 80-88 %) and 88 % (95 % CI 81-92 %), respectively. Among patients with normal mammography, 4 % were diagnosed with breast cancer by BSGI, and among those with mammography suggestive of malignancy or new biopsy-proven breast cancer, 6 % were diagnosed with additional cancers in the breast by BSGI.

CONCLUSION

BSGI had a high diagnostic performance as an excellent adjunct modality to mammography for detecting breast cancer. The ability to identify subcentimetre cancer and DCIS was also high.

A novel functional infrared imaging system coupled with multiparametric computerised analysis for risk assessment of breast cancer

OBJECTIVE

We evaluated a functional three-dimensional (3D) infrared imaging system (3DIRI) coupled with multiparametric computer analysis for risk assessment of breast cancer. The technique provides objective risk assessment for the presence of a malignant tumour based on automated parameters derived from a clinically known training set.

METHODS

Following institutional review board approval, we recruited 434 women for this prospective multicentre trial, including 256 healthy woman undergoing routine screening mammography with BI-RADS-1 results and 178 women with newly diagnosed breast cancer. This was a two-phase study: an initial training and calibration phase, followed by a two-armed blinded evaluation phase (52 healthy and 66 with breast cancer). 3DIRI data sets were acquired using a non-contact, no radiation system.

RESULTS

The sensitivity and specificity of functional infrared imaging in providing the correct risk for the presence of breast cancer were 90.9 % and 72.5 %, respectively. The area under the ROC curve was 86 %. Forty-two of the 60 (70 %) cancers in women correctly classified by the system as suspicious were smaller than 20 mm in size.

CONCLUSION

The preliminary blinded results of this novel technology show sufficient performance of functional infrared imaging in providing risk assessment for breast cancer to warrant further clinical studies.

KEY POINTS

• 3D functional infrared imaging (3DIRI) provides new metabolic signatures from breast lesions. • 3DIRI offers high sensitivity for risk assessment of breast cancer. • It also has reasonable specificity. • This initial experience warrants further evaluation in larger clinical trials.

Diagnostic Performance of Breast-Specific Gamma Imaging (BSGI) for Breast Cancer: Usefulness of Dual-Phase Imaging with (99m)Tc-sestamibi

PURPOSE

The aim of this study was to investigate the usefulness of breast-specific gamma imaging (BSGI) with dual-phase imaging for increasing diagnostic performance and interpreter confidence.

METHODS

We studied 76 consecutive patients (mean age: 49.3 years, range: 33-61 years) who received 925 MBq (25 mCi) (99m)Tc-sestamibi intravenously. Craniocaudal and mediolateral oblique planar images were acquired for all patients. Delayed images were obtained from all patients 1 h after tracer injection, except for patients with no definite abnormal uptake. All images were classified into four categories: group 1 (definite negative) = no definite abnormal uptake; group 2 (possible negative) = symmetrically diffuse and amorphous uptake; group 3 (possible positive) = asymmetrically mild and nodular uptake; group 4 (definite positive) = asymmetrically intense and nodular uptake. To evaluate diagnostic performance, the BSGI studies were classified as positive (group 3 or 4) or negative (group 1 or 2) for malignancy according to a visual analysis. The final diagnoses were derived from histopathological confirmation and/or imaging follow-up after at least 6 months (range: 6-14 months) by both ultrasonography and mammography.

RESULTS

The patients' ages ranged from 33 to 61 years, with an average of 49.3 years. Thirteen patients were diagnosed with malignancy, and 63 patients were diagnosed as negative for malignancy. Using early images, 43 patients were classified as group 1, 12 as group 2, 10 as group 3 and 11 as group 4. Based on early images, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of BSGI were 77 %, 83 %, 48 %, 95 % and 82 %, respectively. Dual-phase BSGI had a sensitivity, specificity, PPV, NPV and accuracy of 69 %, 95 %, 75 %, 94 % and 91 %, respectively. The BSGI specificity was significantly higher with dual-phase imaging than with single-phase imaging (p = 0.0078), but the sensitivity did not differ significantly (p = 1.0). Based on dual-phase imaging, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of BSGI for the evaluation of US BI-RADS 4 lesions were 60 %, 86 %, 67 %, 83 % and 78 %, respectively.

CONCLUSION

Dual-phase imaging in BSGI showed good diagnostic performance and would be useful for increasing interpreter diagnostic confidence, with higher specificity, positive predictive value and accuracy for breast cancer screening as well as the differential diagnosis of breast disease compared with single-phase imaging.

Breast-specific gamma imaging in the detection of atypical ductal hyperplasia and lobular neoplasia

RATIONALE AND OBJECTIVES

Atypical lesions such as atypical ductal hyperplasia (ADH) and lobular neoplasia are nonmalignant lesions that are associated with significant increased risk of developing breast cancer. Atypical lesions have been reported to present with focal increased radiotracer uptake on breast-specific gamma imaging (BSGI) examination, a novel physiologic tool for the detection of breast cancer. To date the sensitivity of BSGI in the detection of atypical lesions has not been reported. The purpose of this study is to determine the sensitivity of BSGI in detecting ADH and lobular neoplasia.

MATERIALS AND METHODS

A total of 1316 patients who received a BSGI exam between January 2006 and July 2009 were retrospectively reviewed. All patients who underwent minimally invasive biopsy and subsequent surgical excision where the highest pathology was solely ADH or lobular neoplasia (reported as ALH, lobular carcinoma in situ or lobular neoplasia), according to the pathology database were included (n = 15). The sensitivity was determined as the percentage of positive BSGI exams out of all patients diagnosed with ADH or lobular neoplasia who received a BSGI.

RESULTS

Patient ages ranged from 39 to 67 (mean, 52). Eight of 15 patients had ADH, 6/15 lobular neoplasia, and 1/15 ADH and lobular neoplasia in one lesion. Fifteen of the 15 (100%) patients with surgically confirmed ADH or lobular neoplasia had a positive BSGI, with focally increased radiotracer uptake at the site of the verified high-risk lesion.

CONCLUSION

BSGI has a high sensitivity for the detection of atypical, high-risk breast lesions. A diagnosis of an atypical lesion is concordant with focal increased radiotracer uptake with BSGI and can identify women at increased risk for breast cancer.

Breast molecular imaging: a retrospective review of one institutions experience with this modality and analysis of its potential role in breast imaging decision making

Breast Molecular Imaging (or Breast-Specific Gamma Imaging) has been previously shown to be both sensitive and specific for the detection of breast cancer. The purpose of our study was to retrospectively review all cases of Breast Molecular Imaging (BMI) performed at our institution to determine BMI's potential role in Breast Imaging decision making. A total of 416 cases of BMI from January 2007 to November 2009 were analyzed and the following data were collected: indication for examination, BIRADS assignment after BMI, biopsy outcomes, sensitivity and specificity of the modality and patient follow-up. Fifty-six percent of cases were ordered for an indeterminate asymmetry or focal asymmetry, 14% for evaluation of calcifications, and less than 10% each for the remainder of the indications including palpable lumps with negative imaging, evaluation of extent of disease in patients with known breast cancer and screening of high risk patients who could not undergo MRI. BMI was also shown to be helpful in evaluation of lesions that were difficult to biopsy or for patients that desired further testing rather than biopsy or short term follow-up of abnormalities. Seventy percent of BMI cases performed completed the diagnostic evaluation with BIRADS 1 or BIRADS 2 designations. Only 14% of cases ultimately resulted in biopsy. Contra-lateral findings were discovered in 10% of patients, more than half of which were occult malignancies or high-risk lesions. Of the lesions for which biopsy was recommended, 43% were malignant and 15% were high-risk lesions. Sensitivity of the test at our institution was 93% and specificity 78.9%. Our results show that BMI is both a sensitive and specific test which is useful as an adjunct to standard breast imaging modalities for problem solving in indeterminate cases.

Emerging techniques and molecular imaging in breast cancer

The sensitivity of screening mammography is limited in the evaluation of dense breasts, with as few as 45% of cancers visible in extremely dense breasts. Supplementary imaging for improved sensitivity in women with dense breasts is necessary to overcome this limitation. Emerging technologies that advance the applications of digital mammography include digital breast tomosynthesis and dedicated breast cone-beam computed tomography. Molecular imaging goes beyond structural imaging. A functional imaging technique that provides information on the biology, physiology, and metabolic pathways of cancer might help to improve the sensitivity and specificity of breast cancer diagnosis, facilitate early assessment of treatment response, and help individualize therapy options for patients. Advanced magnetic resonance, nuclear medicine, and optical imaging techniques in the realm of molecular imaging will be explored in this article.

Molecular Imaging in Breast Cancer - Potential Future Aspects

SUMMARY: Molecular imaging aims to visualize and quantify biological, physiological, and pathological processes at cellular and molecular levels. Recently, molecular imaging has been introduced into breast cancer imaging. In this review, we will present a survey of the molecular imaging techniques that are either clinically available or are being introduced into clinical imaging. We will discuss nuclear imaging and multiparametric magnetic resonance imaging as well as the combined application of molecular imaging in the assessment of breast lesions. In addition, we will briefly discuss other evolving molecular imaging techniques, such as phosphorus magnetic resonance spectroscopic imaging and sodium imaging.

Breast imaging: A survey

Breast cancer is the second leading cause of death in women. It occurs when cells in the breast start to grow out of proportion and invade neighboring tissues or spread throughout the body. Mammography is one of the most effective and popular modalities presently used for breast cancer screening and detection. Efforts have been made to improve the accuracy of breast cancer diagnosis using different imaging modalities. Ultrasound and magnetic resonance imaging have been used to detect breast cancers in high risk patients. Recently, electrical impedance imaging and nuclear medicine techniques are also being widely used for breast cancer screening and diagnosis. In this paper, we discuss the capabilities of various breast imaging modalities.

Comparison of radiation exposure and associated radiation-induced cancer risks from mammography and molecular imaging of the breast

PURPOSE

Recent studies have raised concerns about exposure to low-dose ionizing radiation from medical imaging procedures. Little has been published regarding the relative exposure and risks associated with breast imaging techniques such as breast specific gamma imaging (BSGI), molecular breast imaging (MBI), or positron emission mammography (PEM). The purpose of this article was to estimate and compare the risks of radiation-induced cancer from mammography and techniques such as PEM, BSGI, and MBI in a screening environment.

METHODS

The authors used a common scheme for all estimates of cancer incidence and mortality based on the excess absolute risk model from the BEIR VII report. The lifetime attributable risk model was used to estimate the lifetime risk of radiation-induced breast cancer incidence and mortality. All estimates of cancer incidence and mortality were based on a population of 100 000 females followed from birth to age 80 and adjusted for the fraction that survives to various ages between 0 and 80. Assuming annual screening from ages 40 to 80 and from ages 50 to 80, the cumulative cancer incidence and mortality attributed to digital mammography, screen-film mammography, MBI, BSGI, and PEM was calculated. The corresponding cancer incidence and mortality from natural background radiation was calculated as a useful reference. Assuming a 15%-32% reduction in mortality from screening, the benefit/risk ratio for the different imaging modalities was evaluated.

RESULTS

Using conventional doses of 925 MBq Tc-99m sestamibi for MBI and BSGI and 370 MBq F-18 FDG for PEM, the cumulative cancer incidence and mortality were found to be 15-30 times higher than digital mammography. The benefit/risk ratio for annual digital mammography was >50:1 for both the 40-80 and 50-80 screening groups, but dropped to 3:1 for the 40-49 age group. If the primary use of MBI, BSGI, and PEM is in women with dense breast tissue, then the administered doses need to be in the range 75-150 MBq for Tc-99m sestamibi and 35 MBq-70 MBq for F-18 FDG in order to obtain benefit/risk ratios comparable to those of mammography in these age groups. These dose ranges should be achievable with enhancements to current technology while maintaining a reasonable examination time.

CONCLUSIONS

The results of the dose estimates in this study clearly indicate that if molecular imaging techniques are to be of value in screening for breast cancer, then the administered doses need to be substantially reduced to better match the effective doses of mammography.

Characterizing the contribution of cardiac and hepatic uptake in dedicated breast SPECT using tilted trajectories

A small field of view, high resolution gamma camera has been integrated into a dedicated breast, single photon emission computed tomography (SPECT) device. The detector can be flexibly positioned relative to the breast and image beyond the chest wall, allowing the system to capture direct views of the heart and liver. The incomplete sampling of these organs creates artifacts in reconstructed images, complicating lesion detection. To understand the limits imposed on a 3D acquisition trajectory, sequential tilted trajectories at increasing polar tilt are utilized to collect data of anthropomorphic phantoms filled with aqueous (99m)Tc in a clinically realistic concentration ratio. The counts collected per projection between different scans and the SNR, contrast and resolution (FWHM) of two hot lesions were compared. As expected, the counts per projection increased when the camera had direct views of the heart and liver, but remained relatively constant at other angles. The SNR, contrast and FWHM were more affected by the insufficient sampling of the data by the large polar angles than by the cardiac and hepatic activity. An upper bound on polar tilt for each azimuthal position reduces the artifacts in the reconstructed images. Such trajectories were implemented to show artifact-free reconstructed images.

Molecular and Functional Imaging of Breast Cancer

Background

Significant efforts have been directed toward developing and enhancing imaging methods for the early detection, diagnosis, and characterization of small breast tumors. Molecular and functional imaging sets the stage for enhancement of current methodology.

Methods

Current imaging modalities are described based on the molecular characteristics of normal and malignant tissue. New molecular imaging methods that have the potential for clinical use are also discussed.

Results:

Dynamic contrast-enhanced magnetic resonance imaging is more sensitive than mammography in BRCA1 carriers. It is used in screening and in the early evaluation of neoadjuvant therapy. Positron emission mammography is 91% sensitive and 93% specific in detecting primary breast cancers. Sentinel node scintigraphy is a key component of axillary lymph node evaluation. Other imaging modalities being studied include Tc99m sestamibi, radiolabeled thymidine or uridine, estrogen receptor imaging, magnetic resonance spectroscopy, and diffusion magnetic resonance imaging.

Conclusions

Molecular and functional imaging of the breast will likely alter clinical practice in diagnosing and staging primary breast cancer and assessing response to therapy since it will provide earlier information regarding the underlying biology of individual breast cancers, tumor stage, potential treatment strategies, and biomarkers for early evaluation of treatment effects.

Detection of occult foci of breast cancer using breast-specific gamma imaging in women with one mammographic or clinically suspicious breast lesion

RATIONALE AND OBJECTIVES

The aim of this study was to determine how often breast-specific gamma imaging (BSGI) identifies occult cancerous lesions in women with one suspicious lesion detected on mammography or physical exam.

MATERIALS AND METHODS

A retrospective review was performed of the records of all patients who underwent BSGI between January 1, 2004, and June 4, 2007. Included in the study were 159 women who had one suspicious breast lesion on physical exam and/or mammography and who underwent BSGI to evaluate for occult lesions in the breast. All patients had one or more foci of cancer proven pathologically. BSGI findings were classified as normal or abnormal on the basis of the presence of focal radiotracer uptake.

RESULTS

BSGI detected additional suspicious lesions occult to mammography and physical exam in 46 of 159 women (29%). BSGI identified occult cancer in 14 of 40 women (35%) who underwent biopsy or excision because of BSGI findings and in 14 of the 159 (9%) women in this study. In nine women, the occult cancer was present in the same breast as the index lesion (6%), and in five women, the occult cancer was found in the contralateral breast (3%).

CONCLUSIONS

BSGI is an effective imaging modality in the identification of mammographically and clinically occult cancer in women with one suspicious breast lesion.

Dual-modality breast tomosynthesis

PURPOSE

To evaluate the clinical performance of a hybrid scanner that uses dual-modality tomosynthesis (DMT) and technetium 99m sestamibi to provide coregistered anatomic and functional breast images in three dimensions.

MATERIALS AND METHODS

A prospective pilot evaluation of the scanner was performed in women scheduled to undergo breast biopsy after institutional review board approval and informed consent were obtained. All subject data were handled in compliance with the rules and regulations concerning the privacy and security of protected health information under HIPAA. The study included 17 women (mean age, 53 years; age range, 44-67 years) and 21 biopsy-sampled lesions. Results of DMT scanning were compared with histopathologic results for the 21 lesions.

RESULTS

Of the 21 lesions, seven were malignant, and 14 were benign. Among the 13 subjects with one lesion each, three had positive biopsy results, and 10 had negative biopsy results. Among the four subjects with two lesions, the biopsy results were as follows: bilateral in one, both negative; bilateral in one, both positive; unilateral in two, one positive and one negative. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of DMT scanning were 86%, 100%, 100%, 93%, and 95%, respectively.

CONCLUSION

Pilot clinical evaluation of the DMT scanner suggests that it is a feasible and accurate method with which to detect and diagnose breast cancer. Systems such as the DMT scanner that are designed specifically for three-dimensional multimodality breast imaging could make possible some of the advances in tumor detection, localization, and characterization of breast cancer that are now being observed with whole-body three-dimensional hybrid systems, such as positron emission tomography/computed tomography (CT) or single photon emission computed tomography/CT.

Observer detection limits for a dedicated SPECT breast imaging system

An observer-based contrast-detail study is performed in an effort to evaluate the limits of object detectability using a dedicated CZT-based breast SPECT imaging system under various imaging conditions. A custom geometric contrast-resolution phantom was developed that can be used for both positive ('hot') and negative contrasts ('cold'). The 3 cm long fillable tubes are arranged in six sectors having equal inner diameters ranging from 1 mm to 6 mm with plastic wall thicknesses of <0.25 mm, on a pitch of twice their inner diameters. Scans of the activity filled tubes using simple circular trajectories are obtained in a 215 mL uniform water filled cylinder, varying the rod:background concentration ratios from 10:1 to 1:10 simulating a large range of biological uptake ratios. The rod phantom is then placed inside a non-uniformly shaped 500 mL breast phantom and scans are again acquired using both simple and complex 3D trajectories for similarly varying contrasts. Summed slice and contiguous multi-slice images are evaluated by five independent readers, identifying the smallest distinguishable rod for each concentration and experimental setup. Linear and quadratic regression is used to compare the resulting contrast-detail curves. Results indicate that in a moderately low-noise 500 mL background, using the SPECT camera having 2.5 mm intrinsic pixels, the mean detectable rod was approximately 3.4 mm at a 10:1 ratio, degrading to approximately 5.2 mm with the 2.5:1 concentration ratio. The smallest object detail was observed using a 45 degrees tilted trajectory acquisition. The complex 3D projected sine wave acquisition, however, had the most consistent combined intra- and inter-observer results, making it potentially the best imaging approach for consistent results.