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    Awarded Grants
    Dual Modality Imaging for Radioguided Breast Surgery

    Scientific Abstract:
    Background: In recent years, mammography has significantly advanced the detection of early stage breast cancer. However, the increased rate of detection of nonpalpable masses has resulted in greater challenges for the breast surgeon during surgical biopsy or lumpectomy. In part because of the uncertainty in lesion location, the positive margin rate for nonpalpable lesions is reported to be greater than 50%. This uncertainty can also result in the removal of unnecessarily large portions of breast tissue, resulting in increased morbidity and greater disfigurement. The most widely used technique for guidance in breast surgery is wire localization (WL). In WL, either radiography or ultrasound guidance is used to insert a wire into the breast and through the lesion. However, there are several drawbacks to WL. First, although care is taken to place the wire through the center of the lesion, current guidance techniques make this difficult. Furthermore, even if the wire is placed properly, it is often difficult for the surgeon to identify the location of the lesion along the length of the wire. Second, the time between when the WL is performed and when the woman is admitted to surgery can be many hours or even days. Since the wire protrudes from the breast during this time, there is a chance that the wire may be inadvertently moved. Third, the path of the wire through the breast is determined by the nature of the imaging technique used to place it, and is therefore unlikely to be the optimum surgical path. Thus, if the wire location at the skin surface is chosen for the point of surgical incision, more breast tissue than necessary may be cut. Objective/Hypothesis: The overall goal of this proposed project is the development of an innovative technique for intraoperative guidance during the surgical excision of nonpalpable breast lesions. The approach, dual modality surgical guidance (DMSG), uses a modified version of a dual modality (digital mammography and breast scintigraphy) breast scanning system developed in our lab. Our hypothesis is that our modified dual modality breast scanner can be used to accurately inject a small amount of a radiolabeled substrate into a lesion in the breast, and then to verify the position of the radiomarker relative to the lesion. Following radiomarking, a hand-held gamma probe can be used to locate and excise the marked lesion. We also hypothesize that DMSG and sentinel lymph node (SLN) mapping can be combined in a single surgical procedure by using two different isotopes. Specific Aims: 1. Modify an upright mammography gantry so that it is capable of accurate 3-dimensional localization using either x-ray transmission or gamma emission imaging. 2. Design a 3-dimensional radiotracer injection system and integrate it into the dual modality breast scanner. 3. Perform a pilot clinical evaluation of the tumor marking procedure without and with SLN mapping among patients scheduled for excisional biopsy or lumpectomy. Study Design: Tasks associated with Specific Aim 1 are to a) design and build a breast support and compression paddle, b) install the gamma camera on the gantry, c) mount the x-ray detector, d) develop 3-D localization algorithms, dual modality phantoms and alignment tools, and e) evaluate the localization accuracy of the entire system. Those associated with Specific Aim 2 are to a) mount the 3-axis needle positioning system on the gantry, b) develop calibration procedures to align the co-ordinate system of the needle stage with that of the gantry arm and detectors, and d) test the accuracy of the injection system using injectable phantoms. Under Specific aim 3, we will perform a pilot clinical study in two stages. In the first stage, we will evaluate our ability to accurately mark the lesion center and compare its performance with WL. In the second stage, we will evaluate the performance characteristics of DMSG when used in conjunction with SLN mapping. Potential Outcomes and Benefits: We anticipate that this approach to image-guided intervention, relative to current WL techniques, will permit more rapid and more precise intraoperative identification of nonpalpable lesions. The potential results of better lesion localization include decreased likelihood of positive margins in the excised specimen, and removal of a smaller mass of breast tissue. These improvements would result in decreased morbidity and trauma to the patient. In addition, combining lumpectomy and SLN mapping in one surgical procedure would reduce recovery time and cost for breast cancer patients.

    Lay Abstract:
    In recent years, mammography has significantly advanced the detection of early stage breast cancer. However, the detection of smaller cancers has resulted in increased difficulty for surgeons attempting to locate the small masses (lesions) during surgical biopsy or lesion removal (excision). A result of the uncertainty in locating the lesion is that the fraction of surgical procedures involving small breast lesions that require a second surgery due to missed cancerous tissue is reported to be greater than 50%. A second result of uncertainty in lesion position is the removal of unnecessarily large portions of breast tissue, resulting in increased morbidity and disfigurement. The most widely used technique for guidance in breast surgery is wire localization (WL). In WL, either x-ray or ultrasound guidance is used to insert a wire into the breast and through the lesion. However, there are several drawbacks to WL. First, although care is taken to place the wire through the center of the lesion, current guidance techniques make this difficult. Furthermore, even if the wire is placed properly, it is often difficult for the surgeon to identify the location of the lesion along the length of the wire. Second, the time between when the WL is performed and when the woman is admitted to surgery can be many hours or even days. Since the wire protrudes from the breast during this time, there is a chance that the wire may be inadvertently moved. Third, the path of the wire through the breast is determined by the nature of the imaging technique used to place it, and is therefore unlikely to be the most optimum surgical path. Thus if the wire location at the skin surface is chosen for the point of surgical incision, more breast tissue than necessary may be cut. The primary goal of this proposed project is the development of an innovative technique that will serve as an alternative to WL for guidance during surgical removal of small breast lesions. The approach makes use of a unique breast scanner that combines digital mammography with nuclear medicine imaging. The dual modality scanner was developed by our group, funded in part by a previous Komen Foundation Imaging Grant. In this proposed project, we will modify a second dual modality scanner so that it can be used for image-guided breast surgery. Prior to surgery, the modified scanner will be used to guide the injection of a small amount of a liquid precisely at the center of the lesion. The liquid will be labeled with a gamma ray emitting isotope (i.e. it is a radiomarker) and will serve as a guide for the surgeon. Although the amount of radiation emitted by the radiomarker is very small so that the radiation dose to the patient and surgeon is negligible, it can easily be detected by the surgeon using a hand-held gamma probe. The surgeon will first use the probe to determine the optimum point of access on the skin, then to locate and remove the radiomarker and the tissue immediately around it. A second goal of this project is to make our proposed radiomarking technique compatible with sentinel lymph node (SLN) mapping. SLN is a surgical procedure recently developed to determine if cancer has spread to the lymphatic system. In SLN, the sentinel node is surgically removed and analyzed for the presence of malignant cells. It has greatly reduced the number of cases in which the entire lymphatic complex near the breast is unnecessarily removed. However, like our proposed technique for lesion marking, SLN uses an injected isotope-labeled compound, which could create a background making it difficult to locate the lesion radiomarker. But by using a specially selected isotope for lesion marking, it is feasible to incorporate lesion localization and removal in the same surgical procedure as SLN mapping. Since currently lesion removal and SLN mapping are typically performed separately, this proposed technique would result in a significant reduction in surgical and recovery time, trauma, and cost for breast cancer patients. We anticipate that relative to current WL techniques, this new approach to image-guided breast surgery will permit more rapid and more precise identification of small lesions. It could also permit the surgeon to better determine the optimal incision path, allowing the minimum amount of breast tissue to be cut. Greater certainty in lesion location could decrease the likelihood of missed cancerous tissue, and could result in the removal of smaller amounts of breast tissue. This approach also promises better comfort for the patient prior to surgery and elimination of the risk that the lesion marker will move. Overall, these improvements would result in decreased cost, morbidity, and trauma for breast cancer patients.