Oxygenation of tumors as evaluated by phosphorescence imaging

Methods for noninvasive imaging of tissue hypoxia

The purpose of this review is to provide an overview of the methods available for imaging tissue oxygenation. The following imaging methods are reviewed: phosphorescence, near-infrared (NIR), positron emission tomography (PET), magnetic resonance imaging ((19)F MRI and BOLD MRI), and electron paramagnetic resonance (EPR). The methods are based on different principles and differ in their ability to accurately quantify tissue oxygenation, either the absolute value of a particular measure of oxygenation (partial pressure of oxygen, concentration), or a parameter related to it (oxygen saturation). Methods that can provide images of relative changes in oxygenation or visualization of hypoxia in a specific tissue of interest are also considered valuable tools for biomedical research and clinical applications.

Is phosphorescence lifetime an indicator of angiogenesis in cortical sarcoma?

In this paper, the oxygen dependent phosphorescence quenching method is proposed to study the correlation between the phosphorescence lifetime and microvessel density in tumors. In the implementation, the S180 transplanted tumor in the mouse is used for the collection of the time-resolved phosphorescence, the tumor microvessel density is measured by immunohistochemical examination of FVIII, the correlation between microvessel density and phosphorescence lifetime is analyzed by multiple regression method. The results show the phosphorescence decay constant measured in tumors is enlarged in the tumor progression. Furthermore, the relative total microvessel area is positively correlative with the phosphorescence lifetime, which is estimated by a two dimension regression equation. It is concluded phosphorescence lifetime is a valuable indicator of angiogenesis during the tumor development.

Tumor oxygenation status as a prognostic marker

Tumor oxygenation status is an independent prognostic indicator in cancer because it influences tumor progression and treatment outcome. Its quantitative value is determined by a number of tumor vascular parameters such as microvascular density, blood flow, blood volume, blood oxygen saturation, tumor tissue pO2, and resistance to oxygen diffusion within the tumor. Over the past several years, considerable time and effort have been invested into developing techniques to effectively and reliably measure the oxygenation status of a tumor. The measurement and interpretation of data obtained with currently available methods is complicated by the heterogeneity in tumor oxygenation. Currently available techniques can be broadly classified into direct invasive methods, direct non-invasive methods, and measurement of surrogate endogenous markers of tumor oxygenation. Of these methods, the Eppendorf pO2 histograph is considered the 'gold standard' and even so has several limitations. Given the importance of tumor oxygenation status in therapy and in predicting disease progression, it is imperative that reliable, globally usable, and technically simplistic methods be developed to yield a consistent, comprehensive, and reliable profile of tumor oxygenation. Until newer more reliable techniques are developed, existing independent techniques or appropriate combinations of techniques should be optimized and validated using known endpoints in tumor oxygenation status and/or treatment outcomes.

Endoscopic components separation for abdominal compartment syndrome

BACKGROUND

Sustained intraabdominal pressures of 14 to 20 mm Hg have significant pathophysiological consequences, but there is currently no satisfactory low-morbidity procedure appropriate for intervention early in the disease process of abdominal compartment syndrome (ACS). The anatomical principles of abdominal wall components separation were used to develop a percutaneous procedure that increased abdominal capacity and decreased abdominal pressure.

METHODS

Using a porcine model, we determined abdominal capacity changes by helium insufflation. Corn oil was then used to create an episode of sustained intraabdominal hypertension and changes in intraabdominal pressure and intestinal mucosal oxygenation were determined.

RESULTS

Endoscopic abdominal wall components separation (EACS) increased abdominal capacity by 1 L (from 0.89 +/- 0.39 L to 1.95 +/- 0.48 L; P <0.001). During intraabdominal hypertension, EACS decreased abdominal pressure by 31.6% (from 15.9 +/- 2.1 to 11.0 +/- 1.5 mm Hg; P <0.001). Intestinal PO(2) was increased by 61% (18.8 +/- 11.4 to 30.3 +/- 11.7; P = 0.012)

CONCLUSIONS

A minimally invasive procedure (EACS) is feasible and has demonstrated effectiveness in a porcine model of ACS.