1High precision CT scanCore principles of operator protection
Time protection: shorten exposure time
Operation optimization: Improve operational proficiency through skill training and reduce equipment debugging and scanning time. For example, using prospective electrocardiographic gating technology instead of retrospective scanning can reduce the radiation dose of cardiac examination by 80%.
Shift system: Implement a shift system for interventional radiology or nuclear medicine personnel who require long-term operations to limit their cumulative exposure time.
Distance protection: Increase the distance from the radiation source
Tool assistance: Use long handled instruments, robotic arms, and other equipment to operate, avoiding direct contact with patients or radiation areas.
Compartment operation: During CT scanning, the operator should monitor the patient through a lead glass observation window in the control room, and the dose equivalent rate outside the computer room should be ≤ 2.5 μ Sv/h.
Shielding protection: Wear protective equipment
Personal protective equipment: Choose lead rubber aprons, neck covers, glasses, and gloves (essential for interventional radiology) according to the type of operation. The lead equivalent of protective clothing should be ≥ 0.25mmPb.
Auxiliary facilities: Lead suspended protective screens and bed side protective curtains should be installed next to the equipment, and nuclear medicine operations should be carried out in lead shielded packaging cabinets.
2、 Key technologies for dose control
Low dose scanning protocol
Parameter optimization:
Tube voltage/current: Adjust according to the patient's body shape. If 80kV low voltage technology is used for children's examination, the dose can be reduced by 50%.
Automatic Exposure Control (ATCM): By monitoring patient attenuation characteristics in real-time and dynamically adjusting tube current, it reduces radiation dose by 20% -40%.
Iterative reconstruction algorithm: using IR technology instead of traditional FBP algorithm, reducing the dose by 60% -80% while ensuring image quality, especially suitable for sensitive areas such as head and neck, chest, etc.
Accurate control of scanning range
Accurate positioning: Using laser positioning lights or 3D scanning planning software to narrow the scanning range to the clinically required area, avoiding exposure of unrelated tissues.
Pitch optimization: In multi-slice spiral CT, increasing the pitch appropriately (such as from 1.0 to 1.5) can shorten the scanning time, but it is necessary to balance image resolution and dose.
Special population protection strategies
Child examination:
Using specialized pediatric protocols, the dosage is reduced to 20% -50% for adults.
Using wide body detectors (such as 256 row CT) to reduce scanning layers and minimize the risk of repeated exposure.
Pregnant women's examination:
Strictly evaluate the indications and do not perform CT scans unless necessary.
Focus on abdominal protection, cover the pelvic cavity with a lead apron, and use a low-dose protocol.
3、 Standard operating procedures and emergency management
Preparation before inspection
Patient notification: Explain the radiation risks to the patient and their family, sign an informed consent form, and focus on communicating with sensitive groups such as pregnant women and children.
Wear protective equipment: Wear lead bibs, lead caps, etc. for patients to protect sensitive organs such as the thyroid and gonads. For example, during a head CT scan, a lead scarf can reduce thyroid radiation dose by more than 50%.
Monitoring during inspection
Real time dose monitoring: By using the device's built-in dose reporting system or external dosimeters, the effective dose of a single examination can be monitored (such as about 2mSv for head CT and about 8mSv for abdominal CT).
Emergency braking: Familiarize yourself with the position of the emergency stop button on the equipment, and immediately terminate exposure in case of mechanical failure (such as a stuck examination bed).
Post inspection management
Equipment maintenance: Check the protective performance of the equipment daily to ensure that the lead doors and observation windows are not damaged, and that the exhaust fan ventilation is normal.
Dose recording: Operators are required to wear personal dosimeters and monitor the cumulative dose monthly. The annual effective dose limit is ≤ 20mSv.
4High precision CT scanTraining and Compliance Requirements
Qualification Certification
Operators need to hold a Radiation Worker Certificate, undergo a re examination every 4 years, and pass radiation protection knowledge training (≥ 24 hours per year).
Compliance with regulations
Implement the Basic Standards for Ionizing Radiation Protection and Radiation Source Safety, with a single CT scan dose not exceeding 20mSv and an annual cumulative dose of ≤ 100mSv.
Medical institutions need to publicize the radiation dose of CT scans and provide non radiation alternatives such as MRI for patients to choose from.
emergency response
Develop emergency response plans for radiation accidents and conduct regular drills. If unexpected exposure occurs, immediately assess the dose of the exposed personnel and conduct medical follow-up if necessary.