Lecture 3 Flashcards
Hazards of radiation
- Ionising radiation is harmful to living tissues, causes intracellular ionisation causing free radical production, this interferes with the molecular chemistry of the cells
- doses of radiation are cumulative - long term exposure to small does = bad
What does the damage from radiation depend on?
- The tissue irradiated
- The charectoristics of the radiation e.g x-ray
- Dose of radiation
-Time period of exposure
What tissues are most commonly effected by radiation?
Rapidly diving cells so skin, gut and gametes - gametes means that side effects can be passed onto the next generation
e.g Bone marrow, ovary/ testes, skin, GI tract, embryo (pregnant)
Effects of radiation
- inflammation
- Slowed cell growth
- Necrosis
- potential malignant change - may take years to manifest
- Genetic mutation - effects individual or future generations
e.g. skin cancer developing several years after work with X-rays has ceased
ALARA/ ALARP principle
As Low As Reasonable Achievable/ Practicable
0 won’t always be practical e.g x-raying a horse in the field
Keep doses of radiation to patients and personnel
Methods of protection
- increase space/ distance - link to the inverse square law of X-rays
- Barriers
- Protective clothing - Lead aprons and gloves
- Time - reduced time = reduced radiation dose
Barriers as a method of protection
Stone or brick wall usually sufficient enough to stop scattered radiation but not necessarily primary beam
A cavity wall is usually adequate - lead or barium plaster can be added to stop the primary beam
Protective clothing as a method of protection
Lead aprons or gloves
Only provides protection to scattered radiation, not against the primary beam
Time as a method of protection
Shortening time reduces the radiation dose
shortening examination times for certain procedures such as scinitgraphy (using radioactive isotopes) and fluoroscopy (continuous x-ray production) will reduce doses to personnel
Legislation from?
BVA guidance notes - safe use of ionising radiation in veterinary practice
Ionising radiation regulations 2017 (IRR17)
What does the legislation state practices must do?
- Notify health and safety executive that they are using radiation on the premise - part of formal notification procedures
- Have a ‘local rules’ document in place- details specific information about personnel
Who enforces the legislation
External to practice: Radiation protection adviser (RPA) - gives advice on radiation safety
Internal in practice: Radiation protection superviser (RPS) - the practice will nominate one, on daily basis will be involved with taking x-rays
What is a controlled area?
Area where the radiation dose may exceed 7.5uSv/hour
- Usually 2m around a vertical beam
only exists when xray machine is on and is connected to mains supply
- Access to this area needs to be restricted
- Must have waring signs and lights
- Can be temporary e.g. in stables
- The area will be defined with advise from the RPA
A practices local rules
- Names of RPA and RPS
- Controlled areas
- X-ray equipment being used
- Servicing and fault reporting arrangements - on an annual basis
- PPE- including safe storage and checks
- Personal dosimetry - personal monitoring of exposure
- Contingency plan (if emergency fault develops
- Record keeping - exposure book
- Written system of work e.g. training, personal permitted to be involved, access to controlled area etc.
Basic safety rules 1
- No animal should be manually restrained for radiography except in exceptional circumstances
- use positioning aids such as sand bags and foam blocks
Basic safety rules 2
Any person in x-ray area must wear protective clothing and stay as far away from the primary beam as possible
Basic safety rules 3
No part of any person should ever be in the primary x-ray beam - even with protective clothing
Basic safety rules 4 - direction of beam
If a horizontal beam is used it will continue through plaster so it should be directed at a solid barrier and needs to ensured people are not on the other side
Basic safety rules 5
No one under 16 should be involved in radiography
Basic safety rule 6
Risk assessment should be produced for pregnant members of staff
What are personal dosimeters?
- Are use to prove that personnel are staying under the legal limits of radiation
- personnel will wear them
- Can be film badges, thermoluminescent dosimeters (TLD) and digital monitors
Personal dosimeters
Individual use
Change regally (3 months)
Wear under any protective clothing (so measure the does you receive and not the dose the lead apron receives)
Store carefully e.g avoid washing machine, airports etc. (x-rays there will lead to dose accumulating on dosimeter)
Legal dose limits
General public = 1mSv
Trainees (16-18) = 6mSv
Occupational (18+) = 20mSv
effectively 6mSv for vets as occupation would be something like engineers
X-raying people?
NEVER take an x-ray of a person - either yourself or someone else - you/ the practice will be liable to protection if done so
