Improving image quality and optimizing dose in every Artis system.
In addition to protecting patients from excessive radiation exposure, physicians, technicians and other medical staff should be protected from unnecessary (i.e. scattered) radiation as well.
Care about your own safety and want to find out how you can reduce radiation exposure in addition to our CARE+CLEAR package? Here you can discover different ways of reducing radiation dose in the interventional lab.
Protect the operator
How to ... CARE
Part 1: AX dose saving
Reduce dose for the operator
Scattered radiation does not come directly from the X-ray tube, but rather is scattered by the patient, table, or other devices within the path of the X-ray beam. Usually most of the scattered radiation is generated where the X-ray beam hits the patient.
1. Collimate if applicable
Scattered radiation is approximately proportional to dose area product, that means 50% area translates into 50% scattered radiation (if dose = constant)! The collimation also results in an improved image quality (less scattered radiation, better contrast).
2. Stay away from the tube side
Scattered radiation can be reduced by installing the lateral C-arm with the tube on the left side of the table when the medical staff works on the right. Scattered radiation is mainly generated at the beam entrance location of the patient, which is on the left side in this configuration. At the operator’s working position (right side), radiation exposure from scatter is much lower.
3. Stay away from the patient
Scattered radiation is roughly proportional to the dose area product (DAP) and decreases with distance squared to the location the scatter is generated. That is, twice the distance results in a quarter of the scattered radiation.
4. Shield as much as possible
Scattered radiation is attenuated by matter. Typical shields:
- Apron (lead)
- Glass shields (lead)
- Glasses (lead)
- Lower/upper body protection
- Body (tissue, bone)
5. Bring the monitor as close as possible
The optimal eye to monitor distance is 1 meter or less for non-zoomed display.
6. RaySafe i2 Builds a Better Radiation Safety Culture™
RaySafe i2 dosimeter system is indispensable in creating a successful radiation safety culture. Once in place, both healthcare workers and management benefit from the radiation insight gained. Moreover, focus is returned to treating patients, versus worrying about unnecessary radiation exposure.
An active dosimeter that measures and records radiation every second. Data is transferred wirelessly to the i2 real-time display. It is maintenance-free, easy to wear and can be personalized with different colors and names.
Protect the patient
How to ... CARE
Part 2: Artis specific dose saving
Reduce dose for the patient
1. Select the adequate protocol
For especially dose-sensitive patients, it is possible to generate a special low-dose acquisition protocol. An acquisition pedal of the footswitch can be configured as a low-dose acquisition alternative to the ECC/TSC. A dose saving of 67% can be achieved by using an acquisition dose of 80 nGy/f instead of 240 nGy/f for interventional cardiology and an acquisition dose of 0.8 μGy/f instead of 2.4 μGy/f for interventional radiology.
- Choose a proper organ program
- Use low dose acquisition
- Use Fluoro Loop (Store Fluoro)
- Use Low Dose 3D protocols
2. Minimize footswitch-on time
Footswitch-on time: footswitch-on time controls how long the beam is on the body and thus how long the body is irradiated; less time means less radiation.
Less footswitch-on time ⇒ less skin dose
Example: ½ time on the pedal ⇒ ½ skin dose, ½ dose area product
3. Use low frame rate
High frame rates are used to visualize fast motion without stroboscopic effects. However, the higher the frame rate, the more radiation. Therefore it is best to keep the frame rate as low as possible.
Lower frame rate ⇒ lower skin dose
Example: 7.5 vs. 15 fps ⇒ 50% vs. 100% of skin dose and dose area product
CAREvision: Individually adjustable frame rate from 30 fps down to 0.5 fps
4. Zoom out as much as applicable
Increase of zoom size ⇒ increase of skin dose
⇒ decrease of skin dose area product (only for open collimation)
Effect on image quality:
For large patients at dose rate limit: Increase of zoom size ⇒ increase of image quality
For small patients: Decrease of zoom size ⇒ increase of image quality
5. Lower SID as much as applicable
SID: according to the quadratic law and a constant requested dose at the detector, a greater distance between the source and the imager increases the patient entrance dose. Raising SID from 105 cm (= SID 1) to 120 cm (= SID 2) increases patient entrance dose (i.e. the dose at the IRP) by approximately 30%.
6. Remove grid and increase SID
“Air Gap Technique” (for small patients only, <20 kg)
A simple way to reduce the dose in pediatric examinations, especially for babies or very thin patients, when scatter radiation can be expected to be negligible, is to remove the scatter grid in the flat detector housing.
The grid factor (i.e. the absorption of primary radiation due to the anti-scatter grid compared to free air) is 1.35, which translates into a dose saving of 26%* when removing the grid.
7. Use shallow angles as much as possible
An increase in patient’s thickness of about 3 cm results in twice the entrance dose for a constant detector entrance dose. This rule of thumb is based on the assumption that tissue absorbs radiation in a similar manner as water and that a certain quality of beam is applied.
For every 3 cm patient thickness, entrance dose is doubled (for const. exit dose)
A similar effect occurs when the direction of projection is changed to an oblique position. Because the shape of the body is more oval than circular, the length of the X-ray beam is now longer, resulting in a higher entrance dose. True values may differ significantly since the body is not really a homogeneous ellipsoid but consists of bones, organs, etc.
Shallow angles ⇒ less skin dose
* Nickoloff et al., Cardiovasc Intervent Radiol (2007) 30:168-176