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INTRODUCTION: Hypoxic pulmonary vasoconstriction optimises oxygenation in the lung by matching the local-blood perfusion to local-ventilation ratio upon exposure to alveolar hypoxia. It plays an important role in various pulmonary diseases, but few imaging evaluations of this phenomenon in humans. This study aimed to determine whether chest digital dynamic radiography could detect hypoxic pulmonary vasoconstriction as changes in pulmonary blood flow in healthy individuals. METHODS: Five Asian men underwent chest digital dynamic radiography before and after 60 sec breath-holding at the maximal inspiratory level in upright and supine positions. Alveolar partial pressure of oxygen and atmospheric pressure were calculated using the blood gas test and digital dynamic radiography imaging, respectively. To evaluate the blood flow, the correlation rate of temporal change in each pixel value between the lung fields and left cardiac ventricles was analysed. RESULTS: Sixty seconds of breath-holding caused a mean reduction of 26.7 ± 6.4 mmHg in alveolar partial pressure of oxygen. The mean correlation rate of blood flow in the whole lung was significantly lower after than before breath-holding (before, upright 51.5%, supine 52.2%; after, upright 45.5%, supine 46.1%; both P < 0.05). The correlation rate significantly differed before and after breath-holding in the lower lung fields (upright, 11.8% difference; supine, 10.7% difference; both P < 0.05). The mean radiation exposure of each scan was 0.98 ± 0.09 mGy. No complications occurred. CONCLUSIONS: Chest digital dynamic radiography could detect the rapid decrease in pulmonary perfusion in response to alveolar hypoxia. It may suggest hypoxic pulmonary vasoconstriction in healthy individuals.
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BACKGROUND: Crystal X-ray interferometer-based phase-contrast X-ray computed tomography (C-PCCT) enables the depiction of internal structures of biological tissue without contrast agents. PURPOSE: To determine the advantage of this technique in visualizing detailed morphological structures of a rare spontaneous brain tumor in an aged rat. MATERIAL AND METHODS: An aged rat's spontaneous brain tumor was imaged by C-PCCT without contrast agent. Three-dimensional (3D) images of the tumor microvasculature were reconstructed and compared with pathological pictures. RESULTS: C-PCCT depicted the tumor's various pathological features clearly, e.g. its cell density and vasculature, and blood clots caused by hemorrhaging and/or hematomas. The obtained images resembled pathological pictures with a magnification of ×20 and were used to reconstruct 3D images of the tumor vascularity up to approximately 26 µm in diameter. CONCLUSION: Since C-PCCT is able to depict various pathological conditions, it might be useful for cancer research.
