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Ultrasonics. 2015 Sep;62:50-5. doi: 10.1016/j.ultras.2015.04.012. Epub 2015 May 5.

High and low frequency subharmonic imaging of angiogenesis in a murine breast cancer model.

Author information

1
Department of Radiology, Thomas Jefferson University, Philadelphia, PA 19107, USA; School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA 19104, USA.
2
Yale University, New Haven, CT 06520, USA.
3
University of Pittsburgh, Pittsburgh, PA 15260, USA.
4
Department of Radiology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
5
Plymouth-Whitemarsh High School, Plymouth Meeting, PA 19462, USA.
6
Department of Radiology, Thomas Jefferson University, Philadelphia, PA 19107, USA; Department of Radiologic Sciences, Jefferson College of Health Professions, Thomas Jefferson University, Philadelphia, PA 19107, USA.
7
Department of Radiology, Thomas Jefferson University, Philadelphia, PA 19107, USA. Electronic address: flemming.forsberg@jefferson.edu.

Abstract

This project compared quantifiable measures of tumor vascularity obtained from contrast-enhanced high frequency (HF) and low frequency (LF) subharmonic ultrasound imaging (SHI) to 3 immunohistochemical markers of angiogenesis in a murine breast cancer model (since angiogenesis is an important marker of malignancy and the target of many novel cancer treatments). Nineteen athymic, nude, female rats were implanted with 5×10(6) breast cancer cells (MDA-MB-231) in the mammary fat pad. The contrast agent Definity (Lantheus Medical Imaging, N Billerica, MA) was injected in a tail vein (dose: 180μl/kg) and LF pulse-inversion SHI was performed with a modified Sonix RP scanner (Analogic Ultrasound, Richmond, BC, Canada) using a L9-4 linear array (transmitting/receiving at 8/4MHz in SHI mode) followed by HF imaging with a Vevo 2100 scanner (Visualsonics, Toronto, ON, Canada) using a MS250 linear array transmitting and receiving at 24MHz. The radiofrequency data was filtered using a 4th order IIR Butterworth bandpass filter (11-13MHz) to isolate the subharmonic signal. After the experiments, specimens were stained for endothelial cells (CD31), vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2). Fractional tumor vascularity was calculated as contrast-enhanced pixels over all tumor pixels for SHI, while the relative area stained over total tumor area was calculated from specimens. Results were compared using linear regression analysis. Out of 19 rats, 16 showed tumor growth (84%) and 11 of them were successfully imaged. HF SHI demonstrated better resolution, but weaker signals than LF SHI (0.06±0.017 vs. 0.39±0.059; p<0.001). The strongest overall correlation in this breast cancer model was between HF SHI and VEGF (r=-0.38; p=0.03). In conclusion, quantifiable measures of tumor neovascularity derived from contrast-enhanced HF SHI appear to be a better method than LF SHI for monitoring angiogenesis in a murine xenograft model of breast cancer (corresponding in particular to the expression of VEGF); albeit based on a limited sample size.

KEYWORDS:

Breast cancer; Murine xenografts; Signal processing; Subharmonic imaging; Ultrasound contrast agent

PMID:
25979676
PMCID:
PMC4504767
DOI:
10.1016/j.ultras.2015.04.012
[Indexed for MEDLINE]
Free PMC Article

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