Patricia Goodale Judy

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.

Intraoperative Imaging Guidance for Sentinel Node Biopsy in Melanoma Using a Mobile Gamma Camera

Objective:To evaluate the sensitivity and clinical utility of intraoperative mobile gamma camera (MGC) imaging in sentinel lymph node biopsy (SLNB) in melanoma. Background:The false-negative rate for SLNB for melanoma is approximately 17%, for which failure to identify the sentinel lymph node (SLN) is a major cause. Intraoperative imaging may aid in detection of SLN near the primary site, in ambiguous locations, and after excision of each SLN. The present pilot study reports outcomes with a prototype MGC designed for rapid intraoperative image acquisition. We hypothesized that intraoperative use of the MGC would be feasible and that sensitivity would be at least 90%. Methods:From April to September 2008, 20 patients underwent Tc99 sulfur colloid lymphoscintigraphy, and SLNB was performed with use of a conventional fixed gamma camera (FGC), and gamma probe followed by intraoperative MGC imaging. Sensitivity was calculated for each detection method. Intraoperative logistical challenges were scored. Cases in which MGC provided clinical benefit were recorded. Results:Sensitivity for detecting SLN basins was 97% for the FGC and 90% for the MGC. A total of 46 SLN were identified: 32 (70%) were identified as distinct hot spots by preoperative FGC imaging, 31 (67%) by preoperative MGC imaging, and 43 (93%) by MGC imaging pre- or intraoperatively. The gamma probe identified 44 (96%) independent of MGC imaging. The MGC provided defined clinical benefit as an addition to standard practice in 5 (25%) of 20 patients. Mean score for MGC logistic feasibility was 2 on a scale of 1–9 (1 = best). Conclusions:Intraoperative MGC imaging provides additional information when standard techniques fail or are ambiguous. Sensitivity is 90% and can be increased. This pilot study has identified ways to improve the usefulness of an MGC for intraoperative imaging, which holds promise for reducing false negatives of SLNB for melanoma.

Analysis of Image Combination Methods for Conjugate Breast Scintigraphy

The main objective of the present study was to determine if combining the two images from a conjugate counting system might improve the contrast and signal-to-noise ratio (SNR) of small lesions in all regions of the breast compared to images from a single camera. Several methods for combining the opposing pixels of the two camera images were compared: multiplication, geometric mean, and summation. The image quality metrics measured were spatial resolution, lesion contrast and lesion SNR. These quantities were evaluated both theoretically and experimentally. A capillary phantom was used to measure the spatial resolution as a function of lesion depth and to assess the translation and angular offsets between the two cameras. An acrylic box phantom, with spherical lesions suspended inside, was used to evaluate contrast and SNR as a function of lesion position. Both theoretically and experimentally the spatial resolution in the product images was superior to that in the single images, geometric mean or summation images. Relative to the single camera images, the geometric mean or the summed images, the lesion contrast and SNR of the product images were superior, irrespective of lesion depth, and were more constant with changing lesion depth compared to the single camera images. These findings suggest that improved lesion detectability is possible by imaging simultaneously from both sides of the breast, and forming a combined image using pixel-by-pixel multiplication. This may be especially important if the location of the lesion within the breast is not known a priori.

Optimised breast tomosynthesis with a novel CMOS flat panel detector

Breast tomosynthesis is a promising technology for breast imaging Although existing tomosynthesis systems using detector technology developed for FFDM and uniform acquisition parameters have demonstrated the potential to improve the effectiveness of breast screening, the full potential of tomosynthesis is yet to be realised The effectiveness of tomosynthesis depends on multiple factors, including acquisition geometry, number of projections, reconstruction software and X-ray detector performance In this study, the authors investigated the use of a specially designed 29 cm x 23 cm CMOS flat panel X-ray detector with a novel Active Pixel Sensor with high spatial resolution, high speed read-out, low noise, negligible image lag and a unique ability to reconfigure imaging parameters such as resolution and gain during an acquisition Advanced tomosynthesis acquisition methods were used with the new detector including non-uniform spacing of projection views This combination of optimised X-ray detector and optimised acquisition methods provides enhanced imaging performance.

Tomographic Dual Modality Breast Scanner

We are developing a breast scanner that obtains co-registered dual modality tomographic images of the breast using x-ray imaging (digital breast tomosynthesis) and gamma emission imaging (limited angle breast SPECT). The project is a collaborative effort among the Jefferson Lab (Newport News, VA), Dexela Ltd., (Sudbury MA), and the University of Virginia (UVa) (Charlottesville, VA). The scanner is currently undergoing pilot clinical evaluation at UVas Breast Care Center. Here we report on the design of the scanner, choice of acquisition parameters, and present some early phantom and human breast images.

Molecular breast imaging with directly opposing compact gamma cameras

The goal of this study was to evaluate the efficacy of operating a two-head gamma camera system in a configuration in which the two cameras are positioned on opposite sides of the compressed breast, aligned precisely with each other and with precisely anti-parallel viewing directions. The main objective of the present study was to determine if the combination of the two resulting images might allow for better sensitivity for small lesions in all regions of the breast. Two pairs of gamma cameras were evaluated; one composed of commercially available gamma cameras and the other composed of two research-based gamma cameras. For each pair, an acrylic box phantom, with two spherical lesions suspended inside, was used to evaluate contrast and SNR as a function of lesion position, first for images from the two cameras separately and then for images obtained from pixel- by-pixel multiplication or summation of the individual images. A capillary phantom was used to quantify the spatial resolution as a function of lesion depth for the cameras individually as well as for the resulting multiplied images. Lastly, gelatin phantoms were imaged, each containing a single cube-shaped lesion of ~8 mm side length positioned at varying depths within the phantom. Relative to the single camera images or the summed images, the lesion contrast and SNR of the multiplication image were superior, irrespective of lesion depth, and were much more constant with changing lesion depth. Except when the lesion was less than a centimeter from one of the cameras, the SNR of the multiplied image exceeded that of a single camera image obtained using twice the acquisition time. These findings suggest that improved lesion detectability is possible by imaging simultaneously from both sides of the breast, especially if the location of the lesion within the breast is not known a priori.

Scanner for integrated x-ray breast tomosynthesis and molecular breast imaging tomosynthesis

A dual modality tomosynthesis (DMT) breast scanner has been developed that combines x-ray breast tomosynthesis (XBT) and molecular breast imaging tomosynthesis (MBIT) on a common upright gantry to obtain co-registered structural and functional tomosynthesis images This paper describes the scanners design and operation, and summarizes the results of a pilot clinical evaluation using the tracer 99mTc-sestamibi The pilot study results suggest that DMT breast scanning is feasible and provides improved specificity and positive predictive value compared to XBT alone Potential clinical roles for DMT scanning include problem solving for equivocal mammographic/ultrasound studies; as an aid in biopsy target selection following a positive mammogram with multiple suspicious areas; cancer surveillance in patients with a personal history of breast cancer; pre-surgical planning for determination of disease extent; as an alternative for women for whom MRI is impossible; and for monitoring response to neoadjuvant therapy.

Dual modality surgical guidance for non-palpable breast lesions

Currently, the majority of lumpectomy and excisional biopsy procedures are performed using the wire localization (WL) technique; however, this technique suffers from several drawbacks including inaccuracy in placement of the wire, possible displacement of the wire prior to surgery, and ambiguity of the lesions location along the wire. We propose dual modality surgical guidance (DMSG) as a means to overcome many of the problems associated with WL. The approach uses a dual modality (digital mammography and breast scintigraphy) breast imaging system developed in our lab to place a small radioactive marker (a radiomarker), directly into the lesion. Here we present the results of measurements of the localization and injection accuracy of our system. The localization accuracy, evaluated by determining the difference between the known and measured inter-well separations, were within 0.76 mm (standard deviation of 0.46 mm) of the true distances for x-ray imaging and within 0.66 mm (standard deviation of 0.43) for gamma imaging. Our maximum error in injection accuracy in any of the three Cartesian coordinates was 1.8 mm. On average, the errors were 0.6, 0.4, and 0.9 mm for x, y, and z respectively. The results of these phantom tests provide encouragement that our upright digital mammography unit can accurately a) locate a lesion in three dimensions, b) inject a radiomarker into the lesion, and c) assess the offset between the lesion and radiomarker centers.

Dual modality image guided breast surgery using radiomarkers

Currently, the majority of lumpectomy and excisional biopsy procedures involving non-palpable breast lesions are performed using the wire localization technique. We are investigating dual modality surgical guidance as a means of overcoming many of the problems associated with wire localization. The technique uses a dual modality (digital mammography, breast scintigraphy) breast imaging system to place a marker composed of radiolabeled albumin into the lesion. In order to assist the surgeon in identifying a possible surgical path, a point will be marked on the surface of the breast that is geometrically closest to the lesion (the closest skin point, or CSP). In this paper we present the results of measurements of the localization and needle positioning accuracy of our system. We also describe the results of phantom measurements designed to determine the impact of mild breast compression on identification of the CSP. The localization accuracy was found to be within 0.4 mm for both X-ray and gamma imaging. On average, the errors in injection accuracy were 0.4, 0.6, and 0.5 mm for the x, y, and z dimensions, respectively. The result of the compressible phantom tests was that the path length from the lesion to the CSP determined under mild compression differed from that with the breast uncompressed by only ~10%. These results provide encouragement that we can accurately locate a lesion, inject the radiomarker into it, and identify a potential incision point whose distance from the lesion is within 10% of the shortest possible distance.