Radiology Fundamentals

• Radiology is a branch of medicine concerned with radiant energy and radioactive substances.
• Radiology is used for prevention, diagnosis, and treatment of diseases.
• Ionizing radiation studies cause the release of ions from the tissue.
• Nonionizing studies do not cause the release of ions. For example, MRI uses magnetic fields to move molecules around.
• Gamma rays are used for conventional radiographs.
• The central ray is the center of the beam.
• The x-ray is like a flashlight. It gets wider and weaker as you move farther away.
• The most clear part of the x-ray is the center. It is the strongest.
• The particles of x-ray that make it through the body hit the image receptor and expose the film.
• Areas of white on a film are areas where none of the particles made it through the body.
• Radiopaque areas are not easily penetrated by x-rays.
• Radiolucent areas are easily penetrated by x-rays.
• Bone is the most radiodense biological tissue. The least amount of x-rays will make it through bone.
• Blood will show as gray on x-rays.
• Fractures are places on film that the x-rays got through where they should not have.
• Increased thickness of an object will affect radiodensity. The more thick, the less radiodense (less rays make it through).
• Position is the patient's physical position.
• Radiographic position is the body part that is closest to the image receptor.
• Projection is the path of the x-ray beam as it travels through the patient to the image receptor.
• Decubitus is when the body is positioned on a horizontal surface and the use of a horizontal x-ray beam.
• Decubitus is used to detect air-fluid levels or free air in a body cavity (chest or abdomen).
• Anterior posterior project is when the beam travels through the patient in an anterior-to-posterior direction. This is the conventional view of most body regions.
• Posterior to anterior projection is when the beam travels through the patient from back to front.
• Posterior-Anterior projection is the conventional view of the hand, wrist, and chest.
• Lateral project is when the beam moves from left to right or right to left.
• Oblique projection is typically shot at 45 degree angles to sagittal or frontal planes.
• Lateral projects are named from the side the x-ray ends.
• The radiograph is viewed as if the patient were facing you. They will be in anatomical position.
• INT = limb is internally rotated
• EXT = limb is externally rotated
• WTB = patient is standing
• DECUB = patient is recumbent
• INSP = patient is in a state of inspiration
• EXP = patient in state of expiration
• Density of x-ray is the amount of blackening. It can be adjusted by varying current, exposure time, intensity, and distance.
• Current can be adjusted by increasing or decreasing the energy of the x-ray.
• The increased exposure time on an x-ray can wash out really thin areas.
• Current x exposure time = intensity
• Moving the patient closer to the x-ray will increase intensity.
• The area of focus on the x-ray should be in the center of the image.