Common Pediatric Cerebellar Tumors: Correlation between Cell Densities and Apparent Diffusion Coefficient Metrics
ABSTRACT Purpose:To test whether there is correlation between cell densities and apparent diffusion coefficient (ADC) metrics of common pediatric cerebellar tumors.Materials and Methods:This study was reviewed for issues of patient safety and confidentiality and was approved by the Institutional Review Board of the University of Texas Southwestern Medical Center and was compliant with HIPAA. The need for informed consent was waived. Ninety-five patients who had preoperative magnetic resonance imaging and surgical pathologic findings available between January 2003 and June 2011 were included. There were 37 pilocytic astrocytomas, 34 medulloblastomas (23 classic, eight desmoplastic-nodular, two large cell, one anaplastic), 17 ependymomas (13 World Health Organization [WHO] grade II, four WHO grade III), and seven atypical teratoid rhabdoid tumors. ADCs of solid tumor components and normal cerebellum were measured. Tumor-to-normal brain ADC ratios (hereafter, ADC ratio) were calculated. The medulloblastomas and ependymomas were subcategorized according to the latest WHO classification, and tumor cellularity was calculated. Correlation was sought between cell densities and mean tumor ADCs, minimum tumor ADCs, and ADC ratio.Results:When all tumors were considered together, negative correlation was found between cellularity and mean tumor ADCs (ρ = -0.737, P < .05) and minimum tumor ADCs (ρ = -0.736, P < .05) of common pediatric cerebellar tumors. There was no correlation between cellularity and ADC ratio. Negative correlation was found between cellularity and minimum tumor ADC in atypical teratoid rhabdoid tumors (ρ = -0.786, P < .05). In atypical teratoid rhabdoid tumors, no correlation was found between cellularity and mean tumor ADC and ADC ratio. There was no correlation between the ADC metrics and cellularity of the pilocytic astrocytomas, medulloblastomas, and ependymomas.Conclusion:Negative correlation was found between cellularity and ADC metrics of common pediatric cerebellar tumors. Although ADC metrics are useful in the preoperative diagnosis of common pediatric cerebellar tumors and this utility is generally attributed to differences in cellularity of tumors, tumor cellularity may not be the sole determinant of the differences in diffusivity.© RSNA, 2013.
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ABSTRACT: Hypoxia is a critical hallmark of glioma, and significantly compromises treatment efficacy. Unfortunately, techniques for monitoring glioma pO2 to facilitate translational research are lacking. Furthermore, poor prognoses of patients with malignant glioma, in particular glioblastoma multiforme, warrant effective strategies that can inhibit hypoxia and improve treatment outcome. EPR oximetry using implantable resonators was implemented for monitoring pO2 in normal cerebral tissue and U251 glioma in mice. Breathing carbogen (95% O2 + 5% CO2 ) was tested for hyperoxia in the normal brain and glioma xenografts. A new strategy to inhibit glioma growth by rationally combining gemcitabine and MK-8776, a cell cycle checkpoint inhibitor, was also investigated. The mean pO2 of left and right hemisphere were approximately 56 - 69 mmHg in the normal cerebral tissue of mice. The mean baseline pO2 of U251 glioma on the first and fifth day of measurement was 21.9 ± 3.7 and 14.1 ± 2.4 mmHg, respectively. The mean brain pO2 including glioma increased by at least 100% on carbogen inhalation, although the response varied between the animals over days. Treatment with gemcitabine + MK-8776 significantly increased pO2 and inhibited glioma growth assessed by MRI. In conclusion, EPR oximetry with implantable resonators can be used to monitor the efficacy of carbogen inhalation and chemotherapy on orthotopic glioma in mice. The increase in glioma pO2 of mice breathing carbogen can be used to improve treatment outcome. The treatment with gemcitabine + MK-8776 is a promising strategy that warrants further investigation. © 2014 Wiley Periodicals, Inc.International Journal of Cancer 04/2015; 136(7). DOI:10.1002/ijc.29132 · 5.01 Impact Factor
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ABSTRACT: The purpose of our study was to test the accuracy and applicability of decision rules utilizing apparent diffusion coefficient (ADC) ratios on accurate preoperative diagnosis of common pediatric cerebellar tumors across two institutions.Neuroradiology 06/2014; 56(9). DOI:10.1007/s00234-014-1398-z · 2.37 Impact Factor
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ABSTRACT: Since its introduction in the early 1990s, diffusion-weighted magnetic resonance imaging (MRI) has played a crucial role in the non-invasive evaluation of tissue microstructure of brain parenchyma in vivo. Diffusion anisotropy, in particular, has been extensively used to infer histological changes due to brain maturation and pathology, as it shows a clear dependence on tissue architecture. Although the resolution used in most studies lies in the macroscopic range, the information provided originates at the microscopic level and, as such, diffusion MRI serves as a microscope that can reveal profound details of tissue with direct clinical and research applications. The interpretation of diffusion parameters of white matter rests on what is known to drive diffusion anisotropy, namely axonal membranes, density and coherence, as well as myelin sheaths. However, these factors interact to modulate anisotropy, making interpretations potentially difficult. While there are numerous publications that report diffusion changes in response to particular, histologically confirmed tissue abnormalities in animal models of disease, the microscopic correlates of altered diffusion parameters due to neurological disorders in humans have been difficult to characterize. Animal models may provide insight into the mechanisms involved, but do not necessarily provide accurate representations of the human condition, making human diffusion MRI studies with direct histological confirmation crucial for our understanding of tissue changes secondary to neurodevelopment and disease. This work provides a synopsis of tissue characteristics that give rise to highly informative, specific diffusion patterns, but also of how methodological and artifactual aspects can provide erroneous diffusion measurements that do not accurately reflect tissue and may lead to misinterpretation of results. Examples of diffusion changes due to human conditions are provided to illustrate the wealth of applications of diffusion MRI in clinical and research fields.Neuroscience 09/2013; 276. DOI:10.1016/j.neuroscience.2013.09.004 · 3.33 Impact Factor