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Detection and Description of Tissue Disease: Advances in the Use of Nanomedicine for Medical Imaging
Published in Dan Peer, Handbook of Harnessing Biomaterials in Nanomedicine, 2021
Jason L. J. Dearling, Alan B. Packard
Computed tomography (CT) is an imaging modality in which x-rays are projected through the subject at different angles and the resulting data are then reconstructed into three-dimensional images. X-rays are able to pass through the different types of tissue to varying degrees, with bone being relatively radiodense, air being essentially radiotransparent, and water lying between these two extremes. The attenuation of the x-rays is measured in Hounsfield Units (HU), with air and water arbitrarily set to 0 and 1000, respectively. As soft tissues tend to have very similar radiodensities, CT imaging can be significantly improved by injecting radiopaque compounds intravenously, improving the definition of vascular structures and providing some degree of soft tissue targeting and differentiation.
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Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Nohyun Lee, Seung Hong Choi, Taeghwan Hyeon
where µv is the attenuation coefficient of a voxel and µW is the attenuation coefficient of water. Although the CT number is dimensionless, the HU (Hounsfield unit) is used as a unit to honor the great contribution of Godfrey Hounsfield. Based on the equation, air and water have CT numbers of −1000 HU and 0 HU, respectively, and the measured CT number of a dense bone is approximately +1000 HU. Thus, a human body has a very large range of CT numbers from −1000 HU for lungs to +1000 HU for bones. This large range is problematic because most soft tissues have CT numbers ranging from 40 to 80 HU. Therefore, a suitable imaging range should be selected by adjusting the window width (the range of CT numbers that are displayed) and the window level (the CT number around which the window is centered).
X-Ray and Computed Tomography
Published in Ravishankar Chityala, Sridevi Pudipeddi, Image Processing and Acquisition using Python, 2020
Ravishankar Chityala, Sridevi Pudipeddi
The HU is the system of units used in CT that represents the linear attenuation coefficient of an object. It provides a standard way of comparing images acquired using different CT machines. The conversion of reconstructed pixel values to HUs is a linear transformation given by HU=(μ−μwμw)∗1000where μ is the linear attenuation coefficient of the object and μw is the linear attenuation coefficient of water. Thus, water has an HU of 0 and air has an HU of −1000 since μ of air is 0.
Evaluation of postoperative dental implant primary stability using 3D finite element analysis
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
The simplified linear elastic material properties of the artificial bone blocks (Table 1) were determined from the literature data (Premnath et al. 2013; Pammer and Bognár 2015). The grading system to classify the structure and the mechanical properties of the patient’s bone are based on the observations of the dentists. The classes of the grading system are D1–D4, where D1 is the densest class which builds up almost entirely from cortical bone tissue and the anatomic location of this class is the anterior mandible. D4 class bone builds up from low-density trabecular tissue and its anatomic location is the posterior maxilla. The D2 and D3 bone class is said to be the most suitable class for implantation because its venous system is enough to provide the perfect amount of nutrient for the tissue regeneration and its mechanical properties are ideal for implantation (Premnath et al. 2013; Pammer and Bognár 2015; Trisi et al. 2010). The Hounsfield unit (HU) is a way to comprise radiation attenuation values in different tissues and to determine their grade. Table 1 shows the correlation between the different physical parameters (Misch 1999).
Morph-Rec: A Novel Computer-Aided Liver Segmentation Model based on Morphological Reconstruction Operation
Published in IETE Journal of Research, 2023
Emerson Nithiyaraj E, Arivazhagan Selvaraj
The pixel values of all the CT slices are in Hounsfield units [24]. Hounsfield units (HU) are dimensionless units used in computed tomography (CT) scanning to communicate CT values in a standardized and easy-to-understand format. The Hounsfield unit values are windowed within the range [−100, 400] for every CT slice. So, all values above +400 will be white and all values below −100 will be black. This windowing process excludes the irrelevant organs and increases the image contrast. A Gaussian filter with a sigma value of 0.3 is applied to each windowed CT slice to reduce the granular noise of the CT images and to smoothen the texture of the CT image [25]. The pre-processed CT slices are stored in a Portable Graphics Format (.png) image format.
Dosimetric effect of carbon fiber treatment couch in boron neutron capture therapy
Published in Journal of Nuclear Science and Technology, 2023
Yongquan Wang, Huangxin Wu, Junliang Du, Jinyang Li, Xingcai Guan, Long Gu
As shown in Figure 4, after obtaining computed tomography (CT) images, the human body’s external contour is delineated first and the CT system couch is removed to add the actual treatment couch during radiotherapy dose calculation. Due to the need for special attention to skin dose in BNCT, the region of interest (ROI) is delineated into two: skin and other normal tissues. In this study, the skin structure is defined as the region extending 3 mm inward from the external contour [5], while the remaining region is considered as other normal tissues. A detailed realistic human head model (Figure 5) was created using computed tomography (CT) images. A portion of the BSA port model has been integrated into the voxel model to enhance the realism of the geometric conditions. In order to maintain the accuracy of dose calculation, the voxel size was consistent with the original CT image (0.80734 × 0.80734 × 3 mm3), with a total of 2,553,000 voxels (150, 230, 74). Hounsfield Units (HU) are dimensionless units universally used in computed tomography (CT) scanning to express CT numbers in a standardized and convenient form. They are used to measure radiodensity. The HU values of each voxel were converted into material density and element composition using the method of Massachusetts General Hospital and Harvard Medical School [13], which was further improved based on the work of [14], and the method has been validated for its accuracy in RT-PHITS [15] by Hu [5,16]. The HU space is divided into 27 groups: 1 group for air, 1 group for lung tissue, 7 groups for soft tissues, 15 groups for skeletal tissues, and 3 groups for high-Z materials, as shown in Table 1. The 10B concentration in the skin, normal tissue, and tumor were set as 25, 18 ppm, and 60 ppm [17], respectively. It is worth mentioning that 10B in normal tissue only exists in lung tissue and soft tissues, and skeletal tissues do not contain 10B.