Academic Radiology
Volume 16, Issue 1 , Pages 71-78, January 2009

Delta-projection Imaging on Contrast-enhanced Ultrasound to Quantify Tumor Microvasculature and Perfusion1

  • Chandra M. Sehgal, PhD

      Affiliations

    • Department of Radiology, University of Pennsylvania Medical Center, 3400 Spruce Street, Philadelphia, PA 19104
    • Corresponding Author InformationAddress correspondence to: C.M.S.
    • ,
  • Theodore W. Cary, BA

      Affiliations

    • Department of Radiology, University of Pennsylvania Medical Center, 3400 Spruce Street, Philadelphia, PA 19104
    • ,
  • Peter H. Arger, MD

      Affiliations

    • Department of Radiology, University of Pennsylvania Medical Center, 3400 Spruce Street, Philadelphia, PA 19104
    • ,
  • Andrew K.W. Wood, DVSc, PhD

      Affiliations

    • Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania

Received 12 June 2008; accepted 2 July 2008.

Rationale and Objectives

The aim of this study was to assess the Δ-projection image processing technique for visualizing tumor microvessels and for quantifying the area of tissue perfused by them on contrast-enhanced ultrasound images.

Materials and methods

The Δ-projection algorithm was implemented to quantify perfusion by tracking the running maximum of the difference (Δ) between the contrast-enhanced ultrasound image sequence and a baseline image. Twenty-five mice with subcutaneous K1735 melanomas were first imaged with contrast-enhanced grayscale and then with minimum-exposure contrast-enhanced power Doppler (minexCPD) ultrasound. Delta-projection images were reconstructed from the grayscale images and then used to evaluate the evolution of tumor vascularity during the course of contrast enhancement. The extent of vascularity (ratio of the perfused area to the tumor area) for each tumor was determined quantitatively from Δ-projection images and compared to the extent of vascularity determined from contrast-enhanced power Doppler images. Delta-projection and minexCPD measurements were compared using linear regression analysis.

Results

Delta-projection was successfully performed in all 25 cases. The technique allowed the dynamic visualization of individual blood vessels as they filled in real time. Individual tumor blood vessels were distinctly visible during early image enhancement. Later, as an increasing number of blood vessels were filled with the contrast agent, clusters of vessels appeared as regions of perfusion, and the identification of individual vessels became difficult. Comparisons were made between the perfused area of tumors in Δ-projections and in minexCPD images. The Δ-projection perfusion measurements were correlated linearly with minexCPD.

Conclusion

Delta-projection visualized tumor vessels and enabled the quantitative assessment of the tumor area perfused by the contrast agent.

Key Words: Ultrasound contrast agents, power Doppler, angiogenesis, vascular disrupting agent, tumor perfusion

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1 This study was supported by grant EB001713 from the National Institutes of Health, Bethesda, MD.

PII: S1076-6332(08)00416-9

doi:10.1016/j.acra.2008.07.013

Academic Radiology
Volume 16, Issue 1 , Pages 71-78, January 2009

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