Underneath the Arches, no. 61, October 24, 1968

Underneath the Arches was Grand Valley State\u27s faculty and staff newsletter, published from 1963 to 1971. It was a precursor to the Forum

Image_1_Electron Density of Adipose Tissues Determined by Phase-Contrast Computed Tomography Provides a Measure for Mitochondrial Density and Fat Content.TIF

<p>Phase-contrast computed tomography (PCCT) is an X-ray-based imaging method measuring differences in the refractive index during tissue passage. While conventional X-ray techniques rely on the absorption of radiation due to differing tissue-specific attenuation coefficients, PCCT enables the determination of the electron density (ED). By the analysis of respective phantoms and ex vivo specimens, we identified the components responsible for different electron densities in murine adipose tissue depots to be cellular fat and mitochondrial content, two parameters typically different between white adipose tissue (WAT) and brown adipose tissue (BAT). Brown adipocytes provide mammals with a means of non-shivering thermogenesis to defend normothermia in a cold environment. Brown adipocytes are found in dedicated BAT depots and interspersed within white fat depots, a cell type referred to as brite (brown in white) adipocyte. Localization and quantification of brown and brite adipocytes in situ allows an estimate of depot thermogenic capacity and potential contribution to maximal metabolic rate in the cold. We utilized PCCT to infer the composition of white, brite, and brown adipose tissue from ED of individual depots. As proof of principle, we imaged mice 10, 20, and 30 days of age. During this period, several WAT depots are known to undergo transient browning. Based on ED, classical WAT and BAT could be clearly distinguished. Retroperitoneal and inguinal WAT depots increased transiently in ED during the known remodeling from white to brite/brown and back to white. We systematically analyzed 18 anatomically defined adipose tissue locations and identified changes in fat content and mitochondrial density that imply an orchestrated pattern of simultaneous browning and whitening on the organismic level. Taken together, PCCT provides a three-dimensional imaging technique to visualize ED of tissues in situ. Within the adipose organ, ED provides a measure of mitochondrial density and fat content. Depending on experimental setting, these constitute surrogate markers of cellular distribution of white, brite, and brown adipocytes and thereby an estimate of thermogenic capacity.</p

Data_Sheet_1_Electron Density of Adipose Tissues Determined by Phase-Contrast Computed Tomography Provides a Measure for Mitochondrial Density and Fat Content.zip

<p>Phase-contrast computed tomography (PCCT) is an X-ray-based imaging method measuring differences in the refractive index during tissue passage. While conventional X-ray techniques rely on the absorption of radiation due to differing tissue-specific attenuation coefficients, PCCT enables the determination of the electron density (ED). By the analysis of respective phantoms and ex vivo specimens, we identified the components responsible for different electron densities in murine adipose tissue depots to be cellular fat and mitochondrial content, two parameters typically different between white adipose tissue (WAT) and brown adipose tissue (BAT). Brown adipocytes provide mammals with a means of non-shivering thermogenesis to defend normothermia in a cold environment. Brown adipocytes are found in dedicated BAT depots and interspersed within white fat depots, a cell type referred to as brite (brown in white) adipocyte. Localization and quantification of brown and brite adipocytes in situ allows an estimate of depot thermogenic capacity and potential contribution to maximal metabolic rate in the cold. We utilized PCCT to infer the composition of white, brite, and brown adipose tissue from ED of individual depots. As proof of principle, we imaged mice 10, 20, and 30 days of age. During this period, several WAT depots are known to undergo transient browning. Based on ED, classical WAT and BAT could be clearly distinguished. Retroperitoneal and inguinal WAT depots increased transiently in ED during the known remodeling from white to brite/brown and back to white. We systematically analyzed 18 anatomically defined adipose tissue locations and identified changes in fat content and mitochondrial density that imply an orchestrated pattern of simultaneous browning and whitening on the organismic level. Taken together, PCCT provides a three-dimensional imaging technique to visualize ED of tissues in situ. Within the adipose organ, ED provides a measure of mitochondrial density and fat content. Depending on experimental setting, these constitute surrogate markers of cellular distribution of white, brite, and brown adipocytes and thereby an estimate of thermogenic capacity.</p

Principle of the reverse projection method.

<p>Starting from the phase stepping curve (a) that is recorded without sample (reference scan), the sample is measured with grating positions corresponding to the two linear regions of the stepping curve. The two recorded intensities can then be used to obtain the attenuation of the sample as well as its differential phase shift Δ<i>φ</i>_<i>s</i>. Panel (b) shows the histogram of the differential phase-contrast projections of a tomographic scan of a biomedical sample. The red lines mark the region where the error of the linear approximation is less than 5%. Only 0.1% of all pixels lie outside of this region.</p

Mean values and the corresponding standard deviation of the refractive index decrement <i>δ</i> relative to water, exemplary for the materials formalin (fluid inside the tube), PMMA and the Falcon tube.

<p>Mean values and the corresponding standard deviation of the refractive index decrement <i>δ</i> relative to water, exemplary for the materials formalin (fluid inside the tube), PMMA and the Falcon tube.</p

Dark-field/scattering signal strength.

<p>(a) Exemplary dark-field projection of the measured biological sample. The sample shows a smooth dark-field signal close to unity, a prerequisite for successful application of the reverse projection method. (b) Histogram of dark-field values in all projections of one tomographic scan. The peak of the sample’s dark-field is narrow and close to unity. Further, there are next to no pixels with extreme values, which could hinder the applicability of the RP method.</p

Root mean squared error and structure similarity of the tomographic reconstructions displayed in Figs 6 and 7 compared to the reference scan.

<p>Root mean squared error and structure similarity of the tomographic reconstructions displayed in Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184217#pone.0184217.g006" target="_blank">6</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184217#pone.0184217.g007" target="_blank">7</a> compared to the reference scan.</p

Comparing the tomographic reconstructions of a high statistic scans obtained by widely-used phase stepping approach and the reverse projection method.

<p>(a) Tomographic reconstructions of the differential phase contrast projections, obtained with the PS approach (left) and the RP method (right). (b) Line plot at the position marked by the dashed lines in (a). Both images appear very similar, which is also apparent in the line plot. The contrast in the RP image is slightly weaker, since high values are underestimated by this method.</p

Image quality and quantitative accuracy of the RP method in a low-dose scenario.

<p>Comparison of the reconstructions obtained with the PS method (a, 111 counts/pixel/projection) and the RP method (b, 44.4 mean counts) with a reference scan (c). Remarkably, the RP reconstruction shows superior image quality compared to the PS method, even though only 2 of the 5 steps of the PS approach are used to generate the RP reconstruction. Panel (d) shows a difference image of (b) and (c), which is dominated by noise. That implies a good quantitative accuracy of the RP method. This finding is confirmed by line plot in panel (e) which shows plots along the lines displayed in panels (b) and (c). Note that the values for the RP method were averaged over 4 slices and 4 pixels in direction perpendicular to the line for improved readability.</p

Comparison of unfiltered and filtered tomographic slices of a metastasis of a low-grade adenocarcinoma in a steatotic liver.

<p>Axial slices of the conventional absorption-based (A, D) and the phase-contrast (B, E) tomography windowed using the same window level and window width. The histograms of both unfiltered (C) and filtered (F) tomographic datasets demonstrate the filtering result and the red dashed markers show the window level. The areas I (red, surrounding formalin) and II (blue, high-contrast tumor in (B) mark the regions of 30×30 pixels, which were averaged for CNR calculation.</p