[Energy dependence of Hounsfield numbers]

Characterization and differentiation of body fluids, putrefaction fluid, and blood using Hounsfield unit in postmortem CT

The purpose of the present study was to evaluate the ranges of Hounsfield unit (HU) found in body fluids, putrefaction fluids, and blood on postmortem CT and how these ranges are affected by postmortem interval, temperatures, and CT beam energy. Body fluids, putrefaction fluids, and blood from a total of 53 corpses were analyzed to determine the ranges of HU values from postmortem CT images that were taken prior to autopsy. The fluids measured in CT images were obtained at autopsy and examined in terms of macroscopic and microscopic appearances. Body fluids and blood were also collected in plastic bottles, which were subjected to CT scans at different beam energies (80-130 kV) and at various fluid temperatures (4 to 40 °C). At a postmortem interval of 1 to 4 days, the ranges of HU values of the serous fluids (13-38 HU) and the nonsedimented blood (40-88 HU) did not overlap. In the sedimented blood, the upper serum layer exhibited HU value ranges that overlapped with those of the serous fluids. The putrefaction fluids exhibited a range of HU values between 80 and -130 HU. Elevated HU values were observed in fluids with accretive cell impurities. HU values decreased slightly with increasing temperature and CT beam energy. We concluded that serous fluids and blood in fresh corpses can be characterized and differentiated from each other based on HU value ranges. In contrast, body fluids in decomposed corpses cannot be differentiated by their HU value ranges. Different beam energies and corpse temperatures had only minor influences on HU value ranges and therefore should not be obstacles to the differentiation and characterization of body fluids and blood.

Building a 3D Computed Tomography Scanner From Surplus Parts

Computed tomography (CT) scanners are expensive imaging devices, often out of reach for small research groups. Designing and building a CT scanner from modular components is possible, and this article demonstrates that realization of a CT scanner from components is surprisingly easy. However, the high costs of a modular X-ray source and detector limit the overall cost savings. In this article, the possibility of building a CT scanner with available surplus X-ray parts is discussed, and a practical device is described that incurred costs of less than $16,000. The image quality of this device is comparable with commercial devices. The disadvantage is that design constraints imposed by the available components lead to slow scan speeds and a resolution of 0.5 mm. Despite these limitations, a device such as this is attractive for imaging studies in the biological and biomedical sciences, as well as for advancing CT technology itself.

Evaluation of labio-lingual bony support of lower incisors in orthodontically untreated adults with the help of computed tomography

The aim of the present study was to assess bone volume and bone density in orthodontically untreated adults using a CT analyzing method, with reference data in the clinically essential area of the lower incisors being obtained. For quantitative and qualitative assessment of the labial and lingual bony support of the lower incisors, existing CT-images of 20 adult men with a near-to-normal occlusion and a clinically healthy periodontal situation were evaluated. With the help of a special program (SIM/Plant) and on the basis of axial scans, sagittal scans were constructed, permitting the individual imaging of the lower incisors and their alveolar process. The bony support of each tooth was registered labially and lingually perpendicular to the tooth axis at intervals corresponding to 10% of the root length. At the various root levels, especially at the upper parts of the roots, only small amounts of bony support, if any, were frequently observed. Labially, bony fenestrations and dehiscences were frequently seen, but lingually mostly dehiscences. No clinically relevant association was found between labial bony support and cephalometrically registered inclination of the lower incisors. Bone density, which was registered in Hounsfield units at the gingival, middle and apical thirds of the root levels, increased from the gingival to the apical thirds of the roots, generally with lower lingual than labial values. Before initiating orthodontic treatment a thorough clinical assessment of the anatomical situation in the lower incisor segment should be carried out. At present bone volume in this area can be reliably assessed only with computed tomography; however, this has to be weighed up against increased radiation risks. Therefore, the form of the symphysis should initially be roughly assessed by means of conventional cephalometry, with additional CT-based analysis of individual teeth being confined to special indications.