3.0-T MR-guided focused ultrasound for preoperative localization of nonpalpable breast lesions: an initial experimental ex vivo study.
OBJECTIVE
To compare the accuracy of magnetic resonance-guided focused ultrasound (MRgFUS) with MR-guided needle-wire placement (MRgNW) for the preoperative localization of nonpalpable breast lesions.


METHODS
In this experimental ex vivo study, 15 turkey breasts were used. In each breast phantom an artificial nonpalpable "tumor" was created by injecting an aqueous gel containing gadolinium. MRgFUS (n = 7) was performed with the ExAblate 2000 system (InSightec). With MRgFUS the ablated tissue changes in color and increases in stiffness. A rim of palpable and visible ablations was created around the tumor to localize the tumor and facilitate excision. MRgNW (n = 8) was performed by MR-guided placement of an MR-compatible needle-wire centrally in the tumor. After surgical excision of the tumor, MR images were used to evaluate tumor-free margins (negative/positive), minimum tumor-free margin (mm), and excised tissue volume (cm(3)).


RESULTS
With MRgFUS localization no positive margins were found after excision (0%). With MRgNW two excision specimens (25%) had positive margins (P = 0.48). Mean minimum tumor-free margin (+/-SD) with MRgFUS was significantly larger (5.5 +/- 2.4 mm) than with MRgNW (0.9 +/- 1.4 mm) (P < 0.001). Mean volume +/- SD of excised tissue did not differ between MRgFUS and MRgNW localization, ie, 44.0 +/- 9.4 cm(3) and 39.5 +/- 10.7 cm(3) (P = 0.3).


CONCLUSIONS
The results of this experimental ex vivo study indicate that MRgFUS can potentially be used to localize nonpalpable breast lesions in vivo.
Department of Radiology, Stanford University Medical Center, Stanford, California, USA. a.c.schmitz@umcutrecht.nl
Annemarie C
AC
Schmitz
Maurice A A J
MA
van den Bosch
Viola
V
Rieke
Frederick M
FM
Dirbas
Kim
K
Butts Pauly
Willem P Th M
WP
Mali
Bruce L
BL
Daniel
D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology* / Q000601:surgery*; D003287:Contrast Media / Q000008:administration & dosage; D004564:Electrocoagulation / Q000379:methods*; D005260:Female; D005682:Gadolinium / Q000008:administration & dosage; D066298:In Vitro Techniques; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D019047:Phantoms, Imaging; D014422:Turkeys; D014464:Ultrasonic Therapy
D003287:Contrast Media; D005682:Gadolinium