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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- "In a different study, the same authors reported that the tract count per voxel (as derived from whole brain tractography) also correlated with quantitative histology (Stadlbauer et al., 2010), a finding that is explained in part by the dependence of the tracking algorithms on FA values. Edema and fluid accumulation in solid tumors lead to an enlarged extracellular space and, in turn, to increased MD, while highly cellular tumors show the reverse pattern (Humphries et al., 2007; Fatima et al., 2013; Koral et al., 2013). Brain abscesses generally display low values of MD, which shows a strong negative correlation with the number of viable inflammatory cells in the medium (Mishra et al., 2005), and thus diffusion MRI can be used to differentiate them from necrotic brain tumors (Reddy et al., 2006). "
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
- Radiology 08/2013; 268(2):318-22. DOI:10.1148/radiol.13130420 · 6.21 Impact Factor
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ABSTRACT: PurposeTo determine the usefulness of q-space MR imaging as means of evaluating the depth of mural invasion, the histologic grades, and lymph node metastasis in esophageal carcinomas.Methods Twenty esophageal specimens each containing a carcinoma were studied with a 7.0 Tesla MR imaging system. q-Space MR images were obtained with a 50-60 mm × 25-30 mm field of view, 256 × 128 matrix, 2 mm section thickness, 10 b values ranging from 0 to 7163 s/mm2, and a motion-probing gradient in the y-direction, and the MR images were compared with the histopathologic findings.ResultsThe mean displacement maps, probability for zero displacement maps, and kurtosis maps in all 20 carcinomas (100%) made it possible to identify the depth of tumor invasion of the esophageal wall. These q-space MR imaging parameters were significantly correlated with the histologic grades of the esophageal carcinomas (P < 0.01), and also significantly correlated with their nuclear-cytoplasmic ratios (P < 0.01 or P < 0.001) and tumor cellularity (cell density) (P < 0.01 or P < 0.001). The q-space MR imaging parameters were also capable of differentiating between the metastatic lymph nodes and nonmetastatic lymph nodes (P < 0.01).Conclusionq-Space MR imaging ex vivo provides excellent diagnostic accuracy for evaluating mural invasion by esophageal carcinomas, the histologic grades of esophageal carcinomas, and lymph node metastasis by esophageal carcinomas. Magn Reson Med 73:2262-2273, 2015. © 2014 Wiley Periodicals, Inc.Magnetic Resonance in Medicine 06/2014; 73(6). DOI:10.1002/mrm.25334 · 3.40 Impact Factor