Imaging hemodynamics

Abstract

Microvascular permeability is a pharmacologic indicator of tumor response to therapy, and it is expected that this biomarker will evolve into a clinical surrogate endpoint and be integrated into protocols for determining patient response to antiangiogenic or antivascular therapies. This review discusses the physiological context of vessel permeability in an imaging setting, how it is affected by active and passive transport mechanisms, and how it is described mathematically for both theoretical and complex dynamic microvessel membranes. Many research groups have established dynamic-enhanced imaging protocols for estimating this important parameter. This review discusses those imaging modalities, the advantages and disadvantages of each, and how they compare in terms of their ability to deliver information about therapy-associated changes in microvessel permeability in humans. Finally, this review discusses future directions and improvements needed in these areas.

Targeting Tumor Perfusion and Oxygenation Modulates Hypoxia and Cancer Sensitivity to Radiotherapy and Systemic Therapies

“…Useful imaging systems have been developed to monitor angiogenesis and the microvasculature in vivo, including DCE-MRI (Choyke, et al 2003), PET and Single Photon Emission Computed Tomography (SPECT), CT, Doppler ultrasound, and optical imaging methods (see Jennings, et al, 2008).…”

“…Preclinical and clinical studies suggest that a successful antivascular treatment results in a decrease in the rate of enhancement along with a decreased amplitude and a slower washout, and that poor response can result in persistent abnormal enhancement (Gillies et al, 2002). (Jennings et al, 2008). A requirement for quantification of perfusion using dynamic methods is an accurate determination of an arterial input function, which can be obtained non-invasively in a purely arterial region of interest, such as the aorta.…”

“…Hemodynamic parameters may be extracted from dynamic changes in X-ray attenuation caused by the intravenous injection of an iodinated contrast agent. Perfusion CT data can deliver quantitative hemodynamic information, such as blood volume, blood flow, permeability surface-area product and mean transit time (MTT) (Jennings et al, 2008).…”

“…Typical parameters that are estimated using Doppler ultrasound include: percent intratumor contrast agent uptake, enhancement timing and pattern, percent blood volume fraction, red blood cell velocity, and perfusion; depending on the type of study and tracer used (Jennings et al, 2008).…”

Surrogate MR markers of response to chemo‐ or radiotherapy in association with co‐treatments: a retrospective analysis of multi‐modal studies

“…Those changes can be assessed in vivo using DCE-MRI (17)(18)(19)(20), or 'non-MR' methods, including CT with iodinated contrast agent, and nuclear medicine (PET/SPECT) (46). It is important to note that the basal blood flow value has no prognostic value in this context; only 'delta' values extracted from dynamic studies are relevant, in contrast to the absolute basal pO 2 value, which can give predictive data.…”