Embedded Files
different measures of radiation exposure. Absorbed dose is the energy delivered to an organ divided by the mass of the organ, in grays. Equivalent dose is the average absorbed dose in an organ or tissue multiplied by a radiation weighting factor, in sieverts. Because, in general, radiation used in medicine has a weighting factor of one, the absorbed dose and the equivalent dose are considered equal. The TED is the sum of the equivalent doses to all tissues and organs multiplied by a tissue-weighting factor for each organ or tissue.2 Endovascular procedures The long fluoroscopy times observed in this study reflect both the complexity of cases seen at our institution and the presence of a training program. In a study of radiation exposure during cardiology fellowship training, Watson et al3 found a statistically significant increase in exposure for cases done in the first versus the second year of fellowship. This difference was largely accounted for by an increased time for the less experienced operators to position the catheters. The needs of training must therefore be balanced against the increased fluoroscopy times for patients and staff alike. Methods to reduce exposure Radiation exposure is proportional to total fluoroscopy time. Therefore, the most effective way to reduce exposure to both the patient and staff is to reduce the total fluoroscopy time. Several steps can be taken toward this end. Catheter-guidewire exchanges with a stable wire position do not need to be visualized in their entirety. When the field of interest is repositioned by moving either the table or the C-arm, the desired position should be estimated and then fine-tuned under fluoroscopy, rather than imaged along the entire course. This is also true when obtaining oblique or angled projections. When cine-acquisition is performed, each screening should be carefully planned and have a specific objective. Poorly planned runs add no information to the procedure and increase exposure, contrast load, and operative time. The most important factor is to be conscious of when the fluoroscope is on and whether necessary information is being gathered. Simply measuring the fluoroscopic time may be enough to increase awareness and reduce overall time. Hough et al4 found that the use of audible radiation monitors, which were dose sensitive, led to a significant reduction in exposure to the staff who wore them. The next most effective way to reduce exposure is to increase the distance from the source. The exposure of the operator is largely due to scattered radiation that results from dispersion of the beam from its intended path by the subject. Scatter decreases with the square of the distance from the source, which is known as the inverse square law. There is a substantial drop in scattered radiation once one moves to between 30 and 50 cm from the scatter source.5, 6 For most endovascular interventions, the working distance from the source is largely fixed by the distance between the area of interest and the arterial access site. The radiation dose to the operator during cardiac interventions has been shown to increase by 1.5 to 2.6 times when the operator moves from the femoral to the subclavian position.7 Kuwayama et al8 found that radiation to the operator was increased by approximately two to three times and hand exposure increased 10-fold when a transcarotid versus a transfemoral route was used for neuroradiologic procedures. EAIA repair requires prolonged imaging over the abdomen and pelvis. Penetration of these tissues requires more energy and results in a significantly higher exposure than imaging the periphery.9 The beam source should be positioned under the patient (ie, posteroanterior imaging). This will decrease scatter and hand exposure of the operator. Placing the beam in the anteroposterior position
Report abuse