{
  "id": 172464,
  "title": "What is a CT scan, exactly?",
  "url": "/competitions/osic-pulmonary-fibrosis-progression/discussion/172464",
  "author_name": "SAURABH THAKUR",
  "post_date": "2020-08-05T06:25:02.788000",
  "votes": 0,
  "comment_count": 0,
  "views": 0,
  "content": "<p>CT scans are essentially 3D X-rays, represented as a 3D array of array of single channel data. \n...................................</p>\n\n<p>Voxel\nA voxel is the 3D equivalent to the familiar two-dimensional pixel. It encloses a volume\nof space (hence, “volumetric pixel”), rather than an area, and is typically\narranged in a 3D grid to represent a field of data. Each of those dimensions will have\na measurable distance associated with it. Often, voxels are cubic, but for this chapter,\nwe will be dealing with voxels that are rectangular prisms.\n..............................................</p>\n\n<p>Each voxel of a CT scan has a numeric value that roughly corresponds to the average\nmass density of the matter contained inside. Most visualizations of that data show\nhigh-density material like bones and metal implants as white, low-density air and lung\ntissue as black, and fat and tissue as various shades of gray. Again, this ends up looking\nsomewhat similar to an X-ray, with some key differences.\nThe primary difference between CT scans and X-rays is that whereas an X-ray is a\nprojection of 3D intensity (in this case, tissue and bone density) onto a 2D plane, a CT\nscan retains the third dimension of the data. </p>\n\n<p>.................................................</p>\n\n<p>NOTE CT scans actually measure radiodensity, which is a function of both\nmass density and atomic number of the material under examination. </p>",
  "messages": [
    {
      "id": 958787,
      "postDate": "2020-08-05T06:25:02.790Z",
      "content": "<p>CT scans are essentially 3D X-rays, represented as a 3D array of array of single channel data. \n...................................</p>\n\n<p>Voxel\nA voxel is the 3D equivalent to the familiar two-dimensional pixel. It encloses a volume\nof space (hence, “volumetric pixel”), rather than an area, and is typically\narranged in a 3D grid to represent a field of data. Each of those dimensions will have\na measurable distance associated with it. Often, voxels are cubic, but for this chapter,\nwe will be dealing with voxels that are rectangular prisms.\n..............................................</p>\n\n<p>Each voxel of a CT scan has a numeric value that roughly corresponds to the average\nmass density of the matter contained inside. Most visualizations of that data show\nhigh-density material like bones and metal implants as white, low-density air and lung\ntissue as black, and fat and tissue as various shades of gray. Again, this ends up looking\nsomewhat similar to an X-ray, with some key differences.\nThe primary difference between CT scans and X-rays is that whereas an X-ray is a\nprojection of 3D intensity (in this case, tissue and bone density) onto a 2D plane, a CT\nscan retains the third dimension of the data. </p>\n\n<p>.................................................</p>\n\n<p>NOTE CT scans actually measure radiodensity, which is a function of both\nmass density and atomic number of the material under examination. </p>",
      "rawMarkdown": " \nCT scans are essentially 3D X-rays, represented as a 3D array of array of single channel data. \n...................................\n\nVoxel\nA voxel is the 3D equivalent to the familiar two-dimensional pixel. It encloses a volume\nof space (hence, “volumetric pixel”), rather than an area, and is typically\narranged in a 3D grid to represent a field of data. Each of those dimensions will have\na measurable distance associated with it. Often, voxels are cubic, but for this chapter,\nwe will be dealing with voxels that are rectangular prisms.\n..............................................\n\nEach voxel of a CT scan has a numeric value that roughly corresponds to the average\nmass density of the matter contained inside. Most visualizations of that data show\nhigh-density material like bones and metal implants as white, low-density air and lung\ntissue as black, and fat and tissue as various shades of gray. Again, this ends up looking\nsomewhat similar to an X-ray, with some key differences.\nThe primary difference between CT scans and X-rays is that whereas an X-ray is a\nprojection of 3D intensity (in this case, tissue and bone density) onto a 2D plane, a CT\nscan retains the third dimension of the data. \n\n.................................................\n\nNOTE CT scans actually measure radiodensity, which is a function of both\nmass density and atomic number of the material under examination. "
    }
  ],
  "comments": [],
  "raw_markdown_by_id": {
    "958787": " \nCT scans are essentially 3D X-rays, represented as a 3D array of array of single channel data. \n...................................\n\nVoxel\nA voxel is the 3D equivalent to the familiar two-dimensional pixel. It encloses a volume\nof space (hence, “volumetric pixel”), rather than an area, and is typically\narranged in a 3D grid to represent a field of data. Each of those dimensions will have\na measurable distance associated with it. Often, voxels are cubic, but for this chapter,\nwe will be dealing with voxels that are rectangular prisms.\n..............................................\n\nEach voxel of a CT scan has a numeric value that roughly corresponds to the average\nmass density of the matter contained inside. Most visualizations of that data show\nhigh-density material like bones and metal implants as white, low-density air and lung\ntissue as black, and fat and tissue as various shades of gray. Again, this ends up looking\nsomewhat similar to an X-ray, with some key differences.\nThe primary difference between CT scans and X-rays is that whereas an X-ray is a\nprojection of 3D intensity (in this case, tissue and bone density) onto a 2D plane, a CT\nscan retains the third dimension of the data. \n\n.................................................\n\nNOTE CT scans actually measure radiodensity, which is a function of both\nmass density and atomic number of the material under examination. "
  }
}