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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Assessment of the oxygenation status of brain tumors has been studied increasingly with imaging techniques in light of recent advances in oncology. Tumor oxygen tension is a critical factor influencing the effectiveness of radiation and chemotherapy and malignant progression. Hypoxic tumors are resistant to treatment, and prognostic value of tumor oxygen status is shown in head and neck tumors. Strategies increasing the tumor oxygenation are being investigated to overcome the compromising [figure: see text] effect of hypoxia on tumor treatment. Administration of nicotinamide and inhalation of various high oxygen concentrations have been implemented. Existing methods for assessment of tissue oxygen level are either invasive or insufficient. Accurate and noninvasive means to measure tumor oxygenation are needed for treatment planning, identification of patients who might benefit from oxygenation strategies, and assessing the efficacy of interventions aimed to increase the radiosensitivity of tumors. Of the various imaging techniques used to assess tissue oxygenation, MR spectroscopy and MR imaging are widely available, noninvasive, and clinically applicable techniques. Tumor hypoxia is related closely to insufficient blood flow through chaotic and partially nonfunctional tumor vasculature and the distance between the capillaries and the tumor cells. Information on characteristics of tumor vasculature such as blood volume, perfusion, and increased capillary permeability can be provided with MR imaging. MR imaging techniques can provide a measure of capillary permeability based on contrast enhancement and relative cerebral blood volume estimates using dynamic susceptibility MR imaging. Blood oxygen level dependent contrast MR imaging using gradient echo sequence is intrinsically sensitive to changes in blood oxygen level. Animal models using blood oxygen level-dependent contrast imaging reveal the different responses of normal and tumor vasculature under hyperoxia. Normobaric hyperoxia is used in MR studies as a method to produce MR contrast in tissues. Increased T2* signal intensity of brain tissue has been observed using blood oxygen level-dependent contrast MR imaging. Dynamic blood oxygen level-dependent contrast MR imaging during hyperoxia is suggested to image tumor oxygenation. Quantification of cerebral oxygen saturation using blood oxygen level-dependent MR imaging also has been reported. Quantification of cerebral blood oxygen saturation using MR imaging has promising clinical applications; however, technical difficulties have to be resolved. Blood oxygen level dependent MR imaging is an emerging technique to evaluate the cerebral blood oxygen saturation, and it has the potential and versatility to assess oxygenation status of brain tumors. Upon improvement and validation of current MR techniques, better diagnostic, prognostic, and treatment monitoring capabilities can be provided for patients with brain tumors.
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PMID:Hypoxia imaging in brain tumors. 1268 10

Platelet-derived growth factors (PDGF) play a major role in pericyte recruitment in tumor capillaries. Pericytes are required for proper vessel development, and contribute to tumor angiogenesis by promoting stabilization and maturation of newly formed vessels. To investigate the effects of pericyte coverage on tumor vessel morphology and function in vivo, tumors derived from B16 melanoma cells transfected with either control plasmid (B16/ctr) or plasmid encoding full-length PDGF-BB (B16/PDGF), the latter previously shown to have enhanced blood vessel pericyte coverage and an increased tumor growth rate, were assessed using histopathological methods, Hoechst 33342-based perfusion analyses, and two noninvasive susceptibility magnetic resonance imaging (MRI) methods. Susceptibility-contrast MRI, incorporating the use of ultrasmall superparamagnetic iron oxide particles, revealed a significant (p < 0.05) reduction in vessel size index (R(v)) of B16/PDGF tumors, and which was validated histologically by the presence of significantly smaller (p < 0.001), more punctate blood vessels identified by fluorescence microscopy of the perfusion marker Hoechst 33342. Intrinsic-susceptibility MRI was used to measure the transverse MRI relaxation rate R(2)*, sensitive to changes in endogenous paramagnetic [deoxyhaemoglobin], and used to probe for vascular maturation and function. Hypercapnia (5% CO(2)/95% air) induced a negligible Delta R(2)* response in the B16/ctr and B16/PDGF tumors. In contrast, hyperoxia (5% CO(2)/95% O(2)) induced a significantly greater R(2)* reduction in the B16/PDGF tumors (p < 0.02). Together the susceptibility MRI-derived biomarkers reveal novel pericyte-dependent changes in the morphology and function of the perfused tumor vasculature in vivo.
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PMID:The effects of tumor-derived platelet-derived growth factor on vascular morphology and function in vivo revealed by susceptibility MRI. 1803 83

Recently, we have demonstrated the feasibility of using hemodynamic response imaging (HRI), a functional magnetic resonance imaging (MRI) method combined with hypercapnia and hyperoxia, for monitoring vascular changes during liver pathologies without the need of contrast material. In this study, we evaluated HRI ability to assess changes in liver tumor vasculature during tumor establishment, progression, and antiangiogenic therapy. Colorectal adenocarcinoma cells were injected intrasplenically to model colorectal liver metastasis (CRLM) and the Mdr2 knockout mice were used to model primary hepatic tumors. Hepatic perfusion parameters were evaluated using the HRI protocol and were compared with contrast-enhanced (CE) MRI. The hypovascularity and the increased arterial blood supply in well-defined CRLM were demonstrated by HRI. In CRLM-bearing mice, the entire liver perfusion was attenuated as the HRI maps were significantly reduced by 35%. This study demonstrates that the HRI method showed enhanced sensitivity for small CRLM (1-2 mm) detection compared with CE-MRI (82% versus 38%, respectively). In addition, HRI could demonstrate the vasculature alteration during CRLM progression (arborized vessels), which was further confirmed by histology. Moreover, HRI revealed the vascular changes induced by rapamycin treatment. Finally, HRI facilitates primary hepatic tumor characterization with good correlation to the pathologic differentiation. The HRI method is highly sensitive to subtle hemodynamic changes induced by CRLM and, hence, can function as an imaging tool for understanding the hemodynamic changes occurring during CRLM establishment, progression, and antiangiogenic treatment. In addition, this method facilitated the differentiation between different types of hepatic lesions based on their vascular profile noninvasively.
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PMID:Vascular profile characterization of liver tumors by magnetic resonance imaging using hemodynamic response imaging in mice. 2139 Jan 87