Lecture 1: Radiation Safety & Physics

What does ALARA mean?

as low as reasonably achievable: maintain exposures well below dose limits while still achieving diagnostic goals

How can ALARA be applied in practice?

• using shielding: lead apron, thyroid shield, gloves

• increase distance

• reduce exposure time

• collimate the beam

• rotate staff and use sedation or sandbags to minimize retakes

What type of radiation does PPE protect against?

scatter radiation

PPE does not protect against the ________.

primary beam

What is produced when x-rays deflect from tissue or equipment and increases occupational exposure?

scatter radiation

What is the function of collimation and grids?

reduce scatter radiation for better images and safety purposes

What is the top concern for low-dose exposure to radiation over time?

skin cancer

What are the properties of x-rays?

• part of electromagnetic spectrum

• no mass/charge

• travel at light speed in straight lines

• can ionize atoms

• penetrate matter variably

How are x-rays produced?

high-speed electrons from the cathode strike the anode inside a vacuum tube

What does mA control in an x-ray?

controls electron quantity (analogous to raising light bulb wattage)

What does kVp control in an x-ray?

controls voltage and electron energy, improves penetration and contrast

What is grey scale?

different tissues (air, fat, soft tissue, bone, metal) absorb x-rays differently, creating radiographic contrast

How do you determine what to set the kVp and mA for your x-ray?

use a measuring caliper → size of patient and part of body being radiographed determines values

How is radiation exposure monitored?

dosimeter badges worn outside lead aprons

How can equine and field radiography be taken safely?

use plate extenders, maximize distance from beam, apply same PPE standards outdoors

What is used between the patient and detector to filter scatter radiation and improve image quality?

grids