Intravascular Ultrasonic Probe Imaging During Core Biopsy Procedures University of Wisconsin-Madison College of Engineering BME 201 March 12, 2004 Team Members: Megan Buroker Kevin Johnson Noelle Simatic Joseph Zechlinski Client: Fredrick Kelcz, Ph.D. Advisor: Prof. Justin Williams, Ph.D. College of Engineering2Abstract Core biopsy procedures are currently subject to high specificity due to inaccurate imaging of small tumors around the biopsy needle. Design alternatives to improve MRI guided core biopsy yield using optical fluorescence and ultrasonic imaging were explored. Optical fluorescence techniques using fiber optics are currently being researched Dr. Nimmi Ramanujam. These techniques differentiate between cancerous tissue and normal tissue by comparing the concentrations of specific fluorophores. As these techniques were being explored by another research group, this design was not chosen. Ultrasonic imaging can differentiate between tissue types by the differences in echogenic calcifications. The basics of IVUS probes were used to develop two ultrasonic methods: an integrated ultrasonic probe and a catheter based IVUS probe technique. The integrated design involves the redesign of an IVUS probe to attach it to the core biopsy procedure. This technique provides effective 360 degree imaging, however the cost associated with the redesign makes it impractical. The chosen design involves the insertion of a catheter based IVUS probe, once the needle is in place. This technique should provide accurate imaging and is extremely practical to implement. However, this techniques will require experimentation to evaluate its ability to image within the needle in the presence of a strong magnetic field.3§1. Problem Statement During stereotactic biopsy procedures, needle placement is difficult to verify. In cases of small tumors or calcifications, the needle itself can actually prevent imaging of the suspicious area; therefore, many stereotactic procedures lead to false negatives. The goal of this project is to improve biopsy yield via local imaging around the needle. §2. Background Info Before determining the method of imaging, it is crucial to understand the characteristics of cancerous breast tissue. As such, breast cancer and biopsy procedures were extensively researched. §2.1 Breast Cancer Core biopsy procedures are often required to diagnosis breast cancer. Breast cancer affects over 200,000 people per year, and early detection has been a continued requirement for successful treatment. Many simple forms detection exist, including self breast exams and mammography, however they often produce inconclusive results. [11] Mammography provides the early detection of breast cancer with higher certainty than self breast exams. It is recommended that women over the age of 40 receive one every year. A mammogram lets the doctors view the breast from a film box with a small x-ray dose. It detects 80-90% of all breast cancers, even small, non-palpable cancerous lesions which cannot be found self exams. Suspicious lesions in mammography lead to further examination using ultrasound and biopsies. [9] One possible finding on a mammogram is a calcification. As their name suggests, calcifications are small build-ups of calcium and minerals in the breast tissue. This is a common4sign of aging; generally most calcifications are benign. To decide whether or not further testing is necessary, size, shape, and distribution of the calcifications are analyzed. [13] In one study, 17% of biopsies taken after suspicious calcifications turned out to be invasive cancers. [10] In these cases, early detection is a matter of life or death. If tumors are found, doctors will classify the type and stage of breast cancer into four categories, stages 0-4. The stage is dependent on the tumor’s size and ability to metastasize. Stage 0 consists of lobular carcinoma in situ and ductal carcinoma in situ. In this stage, abnormal cells stay within the lining of the lobule or ducts and have not invaded any other nearby cells. Stage 4 is the highest level of cancer as the cancer has spread throughout the body. [2] Even after successful treatment, there is always a chance that the cancer will come back. Early detection improves the chances that secondary treatment will not be needed. §2.2 Core Biopsy Procedures Biopsy is often required to correctly diagnose suspicious breast tissues discovered during a regular mammogram. Radiologists depend heavily on pathological analysis of excised tissue, as it is the most accurate method for cancer diagnosis. Several options are available, including fine needle aspiration, stereotactic biopsy, excisional biopsy, and core biopsy. Core biopsy is a popular option and is very accurate in diagnosing most tumors and calcifications. Core biopsy is a method by which small sections of suspicious breast tissue are removed with a specialized needle, which is hollow with a short cutting edge near its end (Figure 1). Needles are typically 11 or 14 gauge with an internal diameter of 3-4 mm. When the lump is palpable, the needle is simply hand-guided by the physician. In other cases, the procedure is generally guided by ultrasound or magnetic resonance imaging (MRI). [4]5 MRI has extremely high spatial resolution, and as such, it is an ideal method to provide accurate imaging feedback during needle insertion. After suspicious tissue is observed in a mammogram, the patient returns for a second appointment during which the biopsy actually occurs. An MR image is taken while the breast is immobilized under light compression. A small incision is made under local anesthesia, and a small plastic clip with a trailing wire is inserted at the abnormal site. A second MR image then verifies correct placement of the clip, after which the core needle is guided by the protruding wire to the biopsy site. A grid system is placed beside the breast and used to guide the needle to a preset depth, also aligning it according to the second MR image. An electric motor is attached to the end of the needle to provide torque, spinning the cutting edge to remove a small cylindrical bore of tissue. Three to six tissue samples are taken to ensure an accurate diagnosis; each sample is approximately 2.0 cm long and 0.16 cm in diameter. Each sample is then sent to the lab, where chemical analysis can be. The entire biopsy procedure lasts 15 minutes, and
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