Decreasing patient dose will result in a proportional decrease in scatter dose to the operator. Therefore, techniques that reduce patient dose will generally also reduce your occupational dose. This is a “win-win” situation; you and your patient both benefit. (Of course, the greatest reduction occurs when imaging is performed without ionizing radiation, such as with ultrasound.) Additional techniques can be used with fluoroscopically guided procedures to reduce occupational dose. Both types of techniques are listed in Table and described in more detail below.
Key points for safe practice
Minimize Fluoroscopy Time
Fluoroscopy should be used only to observe objects or structures in motion. Review the last-image-hold for study, consultation, or education instead of additional fluoroscopic exposure. If available, use fluoroscopy loop recording to review dynamic processes. Use short taps of fluoroscopy instead of continuous operation. Fluoroscopy to determine or adjust collimator blade positioning can be eliminated by using the virtual collimation feature, when present.
Minimize the Number of Fluorographic Images
For digital subtraction angiography, use variable frame rates tailored to the examination (e.g., 1 image/s for 6 s, then 1 image every other second for 24 s, for arteriography of the celiac axis) instead of a constant frame rate (e.g., 2 images/s for 30 s). Suggested imaging sequences are available in some older standard textbooks [58
]. For documentation, use stored last-image-hold images instead of acquiring additional images. When available, use a stored fluoroscopy loop instead of a fluorographic acquisition, if the image quality is adequate to document the findings.
Use Available Patient Dose Reduction Technologies
These include low-fluoroscopy-dose-rate settings, low-frame-rate pulsed fluoroscopy, removal of the antiscatter grid, spectral beam filtration, and use of increased X-ray beam energy. Improved image processing within the fluoroscopic unit can compensate to a considerable degree for the reduced image quality due to decreased exposure levels. Catheters with highly radiopaque tips are easier to see. Children and some small adults can be imaged without the antiscatter grid. This technique reduces dose at the cost of somewhat decreased image quality.
Use Good Imaging-Chain Geometry
Position the patient support so that the patient is as far as possible from the X-ray tube. Place the image receptor as close as possible to the patient.
Adjust collimator blades tightly to the area of interest. Tight collimation reduces patient dose and improves image quality by reducing scatter. When beginning a case, position the C-arm over the area of interest, with the collimators almost closed. Open the collimators gradually until the desired field of view is obtained.
Use All Available Information to Plan the Interventional Procedure
When appropriate, use pre-procedure imaging (ultrasound, MRI, CT) to define the relevant anatomy and pathology and to plan the interventional procedure.
Position Yourself in a Low-Scatter Area
Stay as far away from the X-ray beam as possible. (Remember the inverse square law!) Use tubing extensions or needle holders so that your hands are away from the exposed field. Never place your hands in the X-ray beam. Use power injectors for contrast material injections when feasible, and step out of the procedure room during fluorographic acquisitions (digital subtraction angiography). When using angulated or lateral projections, keep in mind that the highest intensity of scattered radiation is located on the X-ray beam entrance side of the patient. When using these projections, the X-ray tube should be on the side opposite the operator whenever possible. Avoid using equipment with over-the-table X-ray tubes for interventional procedures.
Use Protective Shielding
When you perform fluoroscopically guided interventions, you should wear a personal protective apron and a thyroid shield. Ceiling-suspended shields can provide significant additional dose reduction, especially to unprotected areas of your head and neck. Leaded eyewear is recommended if ceiling-suspended shields cannot be used continuously during the entire procedure. Under-table lead drapes reduce lower extremity dose substantially and should be used whenever possible.
Use Appropriate Fluoroscopic Imaging Equipment
Imaging systems optimized for one type of procedure or body part may be suboptimal for others. Using fluoroscopy equipment under suboptimal conditions frequently results in increased radiation dose. Furthermore, high-radiation-dose procedures should be performed with fluoroscopic systems that incorporate recommended dose-reduction technology and comply with the most current International Electrotechnical Commission standards [60
]. Encourage your institution to purchase this kind of equipment for interventional laboratories.
Obtain Appropriate Training
You and all staff involved in the procedure should have a general knowledge of safe operating practices in a radiation environment. You should be thoroughly familiar with the operation of the particular fluoroscopy equipment you are using. If appropriate medical simulators are available, you should consider using them to learn and practice new skills before you apply them to patients.
Wear Your Dosimeters and Know Your Own Dose!
You need to know your occupational dose in order to ensure that you are working safely. Your dose data will not be accurate unless you always wear your dosimeters, and wear them correctly.