Mobius AIRO Mobile CT System - Assessing Patient Risk; Reducing Risk from X-Ray Dose

MI-42-0001 Rev. 19 27
SAFETY: Radiation Safety
2.7.7 Assessing Patient Risk
How to Assess
Patient Risk
NOTE: Always check the displayed projected radiation dose before initiating the scan.
2.7.8 Reducing Risk from X-ray Dose
How to Reduce
Risk from X-ray
Dose
AIRO offers two means of reducing risk from X-Ray dose via Automatic Exposure Control (AEC) –
weight adapted scan protocols and X-ray Tube Current Modulation.
The general aim of an AEC system for CT is to reduce the variation in radiation doses to different
patient cross sections.
The AIRO adjusts the X-ray tube current based upon the size of the patient, which is configured by
the user through the selection of patient weight, and exam region (body part).
A constant tube current is used for an entire examination or scan series.
AIRO uses preset dosages based on the parameters entered for each scan (area, duration, patient
weight, etc.).
There is no manual mode with AIRO. As identified in the MI-42-0005 AIRO Application Guide for
Protocols and Principles, certain protocols use patient weight as an input to a calculation of constant
tube mA. The calculation is:
Adapted mA = Standard mA * Patient Weight / Standard Patient Weight
Where:
• Standard mA = mA for body region in specified patient category
• Standard Patient Weight = value specified in patient category (see MI-42-0005)
• Custom Patient Weights can be specified in user defined protocols.
In addition, AIRO 1.2 and higher supports Z-axis X-ray Tube Current Modulation (optional). Based
on a scout scan, this feature modulates tube current automatically as the Ring moves along the
specified length of the scan. The dose is limited to not exceed that which would normally be applied
based on the selected patient weight and exam region, but may reduce dose in areas of the patient
with a smaller cross section based on the scout scan.
To reduce the risk of patient overexposure:
NOTE: Using preset dosages does not replace the expertise of the operator.
Steps See
1. Enter the patient’s height and weight. Then specify the area to be
scanned.
6.8.2–6.8.17
2. Review the automatically calculated radiation dosage on the display. 6.8.18
Steps See
1. Enter patient data and scan area. 6.8.2–6.8.17
2. Review the automatically calculated radiation dosage on the display. 6.8.18
3. Evaluate the result.
Options
Dose is appropriate Initiate scan
Dose is inappropriate Check patient data and scan selections