Stereotactic directional vacuum-assisted breast biopsy in 480 patients with microcalcifications: radiological and pathological correlation

Abstract

Since 1999 our group started with practical experience on diagnostic use of small, transportable prototypes of high-resolution gamma cameras (patented) for radioguided surgery: the Imaging Probe (IP). First experiences allowed us to develop dedicated prototypes for specific applications. At the moment the most intriguing field is guiding biopsy. Dedicated detectors, characterized by low cost and weight, allow to transfer imaging where the biopsy has to be done. In this paper, a new combined application for breast cancer detection is described. In present system IP is put inside a Fisher digital stereotactic device prepared for Mammotome biopsy: so biopsy can contemporaneously be driven by X-ray stereotaxis and 99mTc-Sestamibi (MIBI) images from IP. The Field Of View (FOV) is about 2×2 cm2 and 0.8 kg weight. This novel scintillation camera is based upon the compact Hamamatsu R7600-00-C8 Position Sensitive Photomultiplier Tube (PSPMT), coupled to scintillating arrays. The PSPMT can be arranged as array when larger FOV is needed.Present application was provided with off line software for image fusion running on the IP dedicated PC. It was matched with the Fisher digital stereotactic X-ray device dedicated to address Mammotome (Ethicon Endo-surgery by Johnson and Johnson) towards breast opacities. Spatial resolution of the IP was 2.5 mm Full-Width Half-Maximum (FWHM) at laboratory tests. A preliminary IP–X-ray digital system inter-calibration was performed using a Perspex-lead phantom. 99mTc MIBI was injected at the dose of 740 MBq 1 h before biopsy to three patients with breast opacities of respectively 0.6, 0.8 and 1.5 cm, scheduled for Mammotome biopsy. Sixty-four pixel scintigraphic images were acquired before and after biopsy in each patient. Operator was allowed to slightly correct the direction of the Mammotome needle taking into account stereotactic X-ray, scintigraphic and fused images. Bioptic samples were also counted with IP before sending them to pathologist.High-resolution IP scintigraphy showed substantial, though not exact, matching between MIBI hot spots and X-ray opacities. More than one hot spot were detected even in the smallest 0.6 cm lesion. Post biopsy scintigraphy showed absence of significant hot spots in two patients, whereas in the third one of the three hot spots still was partially present. All the lesions showed cancer at histological exam. Measurement of radioactivity on biopsy specimens confirmed the heterogeneous distribution of radioactivity within cancers that IP had detected before biopsy. Or study confirms the ability of IP to guide biopsy or anyway to correct X-ray stereotactic drive.