Spin is the angular momentum intrinsic to a body. Spin is an intrinsic property of every elementary particles related to angular momentum.

Thorium (232Th) is a naturally radioactive element. Thorium is the parent nuclide of one radioactive series, and specific thorium nuclides are decay products of three radionuclide series.

See also Thorotrast.

Tomography is imaging by sections or sectioning to obtain images of slices through objects like the human body. Tomography is derived from the Greek words 'to cut or section' (tomos) and 'to write' (graphein). A device used in tomography is called a tomograph, while the image produced is a tomogram.
The first medical applications utilized x-rays for images of tissues based on their x-ray attenuation coefficient. The mathematical basis for tomographic imaging was laid down by Johann Radon. This type of imaging is used in different medical applications as for example computed tomography, ultrasound imaging, positron emission tomography and magnetic resonance imaging (MRI) also called magnetic resonance tomography (MRT).
Conventional x-ray tomographic techniques show organ structures lying in a predetermined plane (the focal plane), while blurring the tissue structures in planes above and below by linear or complex geometrical motion of the x-ray tube and film cassette.
Basically, computed tomography is the reconstruction of an image from its projections. In the strict sense of the word, a projection at a given angle is the integral of the image in the direction specified by that angle. The CT images (slices) are created in the axial plane, while coronal and sagittal images can be rendered by computer reconstruction.

See also Zonography, Computed or Computerized Axial Tomography, Resolution Element, Radiographic Noise, Intravenous Pyelogram.

A voxel is a volume element (volumetric pixel) representing a value in the three dimensional space (expressed in units of mm³), corresponding to a pixel for a given slice thickness. Voxels are frequently used in the visualization and analysis of medical data. The CT pixel intensity is proportional to the signal intensity of the appropriate voxel. Voxels are associated with CT numbers.