Radiation is the emission of energy, in the forms of waves or particles.
Ionising radiation is radiation that has enough energy to remove electrons from an atom, causing the atom to become charged or ionised.
Ionising radiation can be x-rays or gamma-rays.
X-rays can cause cellular damage and DNA mutation by:
- Creation of free radicals
- Direct ionisation of DNA – double strand breaks (a la radiotherapy)
- “Bystander effect” – mutagenic or fatal effects on adjacent but non radiated cells
Stochastic effects – malignancy risk, with risk or probability rising in a linear fashion dependent on age and gender
Deterministic effects – non cancer consequences, which occur after exceeding a specific dose and severity increases with dose (cataracts, skin changes, hair loss).
Gray (Gy) – measure of energy absorbed per unit of mass (1 Gy = 1 joule/kg)
Sieverts (Sv) – effective or equivalent dose, measure of delivery to heterogenous living tissue (1 Sv = 1 Gy)
Diagnostic imaging exposure generally measured in mSv.
| Annual background exposure | 2 mSv |
| Flight from Aust. to Europe | 0.2 mSv |
| CXR | 0.1 mSv |
| XR KUB | 0.7 mSv |
| XR IVP | 2 – 3 mSv |
| CT KUB (single phase) | 5 mSv |
| Multiphase CT | 10 – 20 mSv |
| MAG3 | 2.5 mSv |
| Bone scan | 6 mSv |
| PAE | 30 – 40 mSv |
| URS | 1 mSv |
| PCNL | 8 mSv |
Occupation exposure limit – should be no more than 20 mSv / year average (no single year more than 50 mSv).
Cancer risk (stochastic) from exposure to ionising radiation depends on the effective dose and the age at which this was received.
Urology patients at risk of excess radiation include:
- Stone formers
- Testicular cancer surveillance (younger patients, lots of CTs)
- Obese patients – significantly increased effective dose
- Pregnant women
- Children
Use of radiation can be potentially harmful to patient and to staff
How to reduce risk to patient:
- Minimise or avoid tests with high radiation
- Consider alternatives – US/MRI
- Only scan area of interest (i.e. CT pelvis only)
- Work with radiology – low dose CT can be possible
- Reduce fluoroscopy time and area exposed (collimation etc)
Strategies to reduce risk to staff/ourselves:
- Shielding – lead aprons, thyroids, consider lead glasses
- Minimise exposure time, fluoroscopy times
- Single shots instead of screening
- Collimation to reduce dose
- Increase distance from machine/patient
- Maintenance and testing of lead
- Measure own radiation dose with dosimeters – shown to reduce exposure levels
- Training and awareness for staff
- Consider alternatives like USS for PCNL access, ESWL etc
- X-ray tube under the patient to minimise distance and scatter
- Other routine things – laser aiming beam on II, saving last image and putting on B screen, dedicated OT staff