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Radiation treatment success and high tumor oxygenation and success have been known to be highly correlated. This suggests that radiation therapy guided by images of tumor regions with low oxygenation, oxygen-guided radiation therapy (OGRT) may be a promising enhancement of cancer radiation treatment. Before applying the technique to human subjects, OGRT needs to be tested in animals, most easily in rodents. Electron paramagnetic resonance imaging provides quantitative maps of tissue and tumor oxygen in rodents with 1 mm spatial resolution and 1 torr pO resolution at low oxygen levels. The difficulty of using mouse models is their small size and that of their tumors. To overcome this we used XRAD225Cx micro-CT/ therapy system and 3D printed conformal blocks. Radiation is delivered first to a uniform 15% tumor control dose for the whole tumor and then a boost dose to either hypoxic tumor regions or equal volumes of well oxygenated tumor. Delivery of the booster dose used a multiple beam angles to deliver radiation beams whose shape conforms to that of all hypoxic regions or fully avoids those regions. To treat/avoid all hypoxic regions we used individual radiation blocks 3D-printed from acrylonitrile butadiene styrene polymer infused with tungsten particles fabricated immediately after imaging to determine regions with pO less than 10 torr. Preliminary results demonstrate the efficacy of the radiation treatment with hypoxic boosts with syngeneic FSa fibrosarcoma tumors in the legs of C3H mice. [ABSTRACT FROM AUTHOR]

EPR (Electron Paramagnetic Resonance) imaging is particularly useful in monitoring hypoxic zones in tumors which are highly resistant to radiation and chemotherapeutic treatment. This first part of the article covers aspects of CW (continuous wave) imaging with details of FT (pulsed Fourier Transform)-EPR imaging covered in Part 2, to be published in the next issue of Resonance. [ABSTRACT FROM AUTHOR]

Tumor hypoxia plays a fundamental role in tumor progression and treatment resistance. Recent evidence that hypoxia also influences the regulation and transcription of various genes involved in malignant growth and metastases, and promotes a more aggressive tumor phenotype makes its diagnosis even more important.The evidence for the biology of hypoxia in tumors, and imaging of hypoxia with different technologies was reviewed through literature review and Medline searches, and clinical studies with 18F-fluoromisonidazole (FMISO) Positron Emission Tomography (PET).Until recently, determination of the level of tumor oxygenation was only possible using invasive methods that limited its clinical application. Imaging techniques that have shown promise in assessing hypoxia include magnetic resonance imaging and spectroscopy, single photon emission computed tomography (SPECT) and PET. Quantitative hypoxia measurement with 18F-FMISO PET in patients with malignant gliomas and lung cancer have demonstrated intratumoural hypoxia and dissociation of glucose metabolism from hypoxia in some cases, indicating the complex nature of cellular metabolic response to stress.The emerging role of therapies that have improved efficacy in hypoxic conditions, and recent advances in the ability to noninvasively measure in vivo intratumoral hypoxia with functional imaging has renewed interest in the clinical measurement of tumor hypoxia and its impact on cancer treatment. [Copyright &y& Elsevier]

In vivo temporal electron paramagnetic resonance (EPR) imaging of the blood-brain barrier-permeable nitroxide radical, 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidin-1-yloxy (PCAM), in the brain of rats was conducted following acute administration of risperidone (RSP) or haloperidol (HPD). The half-life of the signal intensity of PCAM was obtained from a selected area in the temporal EPR images. The half-lives in the striatum and cerebral cortex for the RSP- or HPD-treated rats were significantly longer than for the control rats (p < 0.01). This finding indicates that the reducing abilities of the striatum and cerebral cortex decreased in the rats to which either RSP or HPD had been acutely administrated because the half-life of PCAM in the selected region of the brain reflects its reducing ability. [ABSTRACT FROM AUTHOR]

The article presents an electron spin resonance (ESR) spectroscopy where a ~0.01 M solution of compound 1 in toluene was placed in a tube 3 millimeter in diameter and argon was bubbled through the solution. The results indicate that the primary phenoxyl radical 1a with ortho-isobornyl substituents is less stable than radical 2a containing tert-butyl groups.