Evaluating tissue microcirculation

Xiuling Qi, PhD

MRI and ultrasound can evaluate the tissue microcirculation in a noninvasive manner, using intra-vascular contrast agents that calculate relative blood volume, which is valuable and helpful for clinical diagnosis and treatment of the tumour. Many medical imaging studies have been conducted to detect and assess the morphological shape and structures of a tumour and to follow up clinical treatments. However, the functional blood flow and blood volume in the tumour and tissue can provide more physiological information of tumour growth.

My protocols are focused on blood volume calculation from the micro-circulations of tumour and tissue in vivo. A VX2 tumour model was used to evaluate the blood volume fraction, including the use of MRI with Clariscan, an intravascular contrast agent and ultrasound with Definity, a micro bubble (Abstract, ISMRM 2002).

I also performed the study using micro-CT to provide more information on the density of the blood vessels from microcirculation and compared to the 3D MRI studies. The minimum blood vessels in the tissue could be observed around 30 to 50 micrometers in diameter (Abstract, ISMRM 2004).

In addition, I study the effect of changing %O2 on the SSFP signal in the kidney and muscle of rabbits. We hope that changes in %O2 in the tissues (including the myocardium) may be detectable with improved sensitivity with SSFP.

References

1. X. Qi and G.A. Wright, “Using Population Data to Calibrate MRI-based Blood Oxygen Saturation Measurements in CHD Patients and Volunteers,” 8th Scientific Meeting of International Society for Magnetic Resonance in Medicine, 3:1570, 2000.
2. X. Qi, N. Merchant, F. Walker, G.D. Webb, P. McLaughlin, J. Stainsby, G.A. Wright, “MRI Assessment of Atrial Septal Defects in Adults,” 9th Scientific Meeting of International Society for Magnetic Resonance in Medicine, p. 455, April 2001.
3. X. Qi, P. Burns, J. Hong, J. Stainsby, G. Wright, “Characterizing Blood Volume Fraction (BVF) in a VX2 Tumour by MRI and Ultrasound”, 10th Scientific Meeting of International Society for Magnetic Resonance in Medicine, number 2106, May 18-24, 2002.
4. X.L. Qi, E.R. Valsangiacomo, C.K. Macgowan, L.N. Nield, S.-J. Yoo, L.K. Hornberger, G.A. Wright, “In-vivo MRI Measurement of Blood Oxygen Saturation in Children with Congenital Heart Disease”, 10th Scientific Meeting of International Society for Magnetic Resonance in Medicine, number 511, May 18-24, 2002.