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Technical Innovation |
1 Department of Radiology, Breast Imaging, Duke University Medical Center, Box
3808, Duke South Hospital, Durham, NC 27710.
2 University of Washington Seattle Cancer Care Alliance, Seattle, WA.
Received March 29, 2005;
accepted after revision September 29, 2005.
Address correspondence to S. V. Ghate
(ghate001{at}mc.duke.edu).
Abstract
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CONCLUSION. The compact portable battery-operated biopsy system can be used successfully for MRI-guided core breast biopsy and is an alternative to current systems.
Keywords: biopsy • breast • MR technique
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When the procedures were performed, written informed consent had been obtained after risks and benefits were explained to the patient. All imaging was performed with a conventional 1.5-T MR scanner (Signa, GE Healthcare). Each procedure was performed with the patient in a prone position, and a dedicated surface breast coil was used (Liberty 5000, USA Instruments). The affected breast was stabilized with moderate compression from a lateral fenestrated grid. Three fiducial markers were placed around the expected site of the lesion, and localizing sequences were acquired. Gadopentetate dimeglumine (Magnevist, Berlex) 0.1 mmol/L per kilogram of body weight was administered rapidly through an existing peripheral IV catheter, and sagittal T1-weighted fat-suppressed gradient-recalled echo sequences (TR/TE, 17/2.0; field of view, 16-18 cm; slice thickness, 1-2 mm; matrix, 512 x 512; no gap) were acquired. Images were reviewed on the monitor, and a cursor was placed at the site of the lesion. Horizontal (x-axis) and vertical (y-axis) coordinates were determined by measurement of the distance from the fiducial marker to the lesion. Depth (z-axis) was determined by calculation of the number of sagittal slices from the grid to the lesion. One centimeter was added to the depth calculation to account for the thickness of the fenestrated grid.
The MRI table and patient were withdrawn from the magnet, and the location of the lesion was established on the grid. The skin was anesthetized, and a small skin incision was made with a number 11 surgical blade. An MRI-compatible coaxial needle consisting of an outer plastic sheath and an inner titanium stylet (Vacora, Bard) was advanced, and the tip of the sheath was placed approximately 1 cm lateral to lesion center. The inner stylet was removed, and limited axial and sagittal sequences were obtained with the coaxial sheath in place to document appropriate targeting of the lesion. The handheld vacuum-assisted biopsy needle was inserted through the plastic sheath, the device was fired to advance the needle, and a mean of eight cores (range, five to 12) were obtained in an around-the-clock manner and submitted for histologic evaluation.
After tissue acquisition was complete, the biopsy device was removed and an MRI-compatible marker clip (Artemis Medical) was deployed through the plastic sheath. Postprocedure sagittal T1-weighted imaging was performed to document adequate sampling of the lesion, to document marker placement, and to determine the presence of postprocedure hematoma. Imaging-histologic correlation was performed for all biopsy results to determine concordance. A 6-month follow-up MRI examination was recommended for all concordant benign lesions, and surgical excision was recommended for all malignant, discordant benign, or high-risk lesions.
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An unsuccessful attempt was made to sample one lesion that was posterior to the biopsy compression grid by application of suction and posterior sampling. Postprocedure imaging showed the biopsy cavity anterior to the lesion, indicating inadequate sampling, and surgical excision was recommended.
The 19 successfully sampled lesions (size range, 4-20 mm; mean size, 8 mm) resulted in one invasive ductal carcinoma (Figs. 2A, 2B and 2C), four high-risk lesions (two atypical ductal hyperplasia, one lobular carcinoma in situ, one papilloma with atypia with adjacent radial scar), and 14 benign lesions, including one fibroadenoma, three areas of fibrosis, two areas of fibrocystic change, one area of fat necrosis and fibrocystic change, one area with sclerosing adenosis, one hemangioma, one benign lymph node, and four areas of benign breast tissue. The papilloma and radial scar were present in the same biopsy.
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All 14 of the benign lesions were determined to be concordant with imaging characteristics, and 6-month follow-up MRI was recommended for stability. Fourteen percent (2/14) of the benign biopsy findings were confirmed at surgery in patients who chose mastectomy for ipsilateral malignant lesions. Twenty-nine percent (4/14) of the lesions were examined with follow-up MRI 4-8 months after biopsy. The images showed resolution of the lesion in three cases and decreased size of the lesion in one case. Although mammographic follow-up was not recommended for these lesions because the lesions were occult to mammography, 21% (3/14) of the lesions had negative results on follow-up mammography but were not imaged with follow-up MRI. In the case of 7% (1/14) of the lesions, the patient was receiving neoadjuvant therapy for known breast cancer in the ipsilateral breast and had not yet undergone follow-up breast imaging. The patients who underwent 29% (4/14) of the biopsies were lost to follow-up.
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Advantages of MRI-guided vacuum-assisted core biopsy include lower risk, morbidity, and expense compared with surgical biopsy; greater accuracy than fine-needle aspiration [2]; and larger volume of tissue sampled compared with automated gun core needle biopsy [3], resulting in lower sampling error. The Vacora vacuum-assisted biopsy system has a compact frame, and the lightweight mechanical housing is easy to hold and maneuver during procedures. Although multiple insertions are necessary to retrieve tissue, the stylet can be easily slipped through the coaxial sheath for rapid tissue retrieval. The battery-operated needle system with an attached integrated vacuum cylinder is independent of bulky wires, cables, and cumbersome vacuum carts and therefore is easy to store and carry in and out of the MRI room.
Our success rate of 95% falls within the 94-98% range reported for other MRI-guided vacuum-assisted systems confirmed with surgical histologic examination [4-6]. Our rate of positive biopsy findings (5% malignant, 21% atypia, 74% benign) included a larger number of false-positive results than previously reported [4-6], probably because of our small sample size.
Limitations of the technique parallel those described for stereotactic biopsy and MRI biopsy in previous studies, including difficulty of accessing lesions in a thinly compressed breast [7, 8] and lesions located far posteriorly within the breast [8]. In two patients with thin breasts and medially located lesions, vacuum-assisted biopsy resulted in minimal piercing of the skin in the medial aspect (the side opposite the skin entry site) that produced temporary discomfort for the patient. Decreasing the amount of compression [8], injecting a generous amount of local anesthetic medial to the lesion [7], and accurately measuring the depth of the lesion with respect to the thickness of the breast may help to avoid this problem in the future.
Posterior lesions pose challenges for all core biopsies, as previously described for prone stereotactic biopsy [8], because of the difficulty of capturing the lesion in the fenestrated grid. Liberman et al. [6] found that tissue adjacent to the needle can be acquired with vacuum-assisted biopsy if needle placement is close to but not exactly at the site of the lesion. This modification is potentially useful for accessing lesions located just posterior to the fenestrated grid; however, we were unsuccessful in our attempt to perform biopsy on a lesion posterior to the grid.
In conclusion, the Vacora core needle biopsy system is a vacuum-assisted device that can be successfully used for MRI-guided core breast biopsy. In our experience, this portable handheld battery-operated device is a versatile alternative to other vacuum-assisted systems.
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