Newer, more efficient radiologic systems produce better imaging using low-dose fluoroscopy at 15 frames per second. In this article, we compare a new system to an earlier radiological system in which 15 to 60 frames was used to evaluate acquired radiation to our patients. Physician preference was the determinant for number of frames per second.

Fluoroscopy times measure only the dynamic usage and not the acquired patient radiation. In this study, we measured patient-acquired radiation during pediatric cardiac catheterization procedures using dosimeters placed at the right axilla, intrascapula, and thyroid positions.

Methods and Materials
Metal Oxide Semiconductor Field Effect Transistors (MOSFET) dosimeters were used to measure radiation acquired by the patient. These are high sensitivity dosimeters designed for low dose fluoroscopy as used in our catheterization laboratory.

Three dosimeters were placed on each patient. These were placed at the right axilla, posterior thyroid, and midscapula positions to best measure anterior-posterior and lateral radiation dosages. As per equipment policy, each dosimeter was calibrated every morning and acquired dosages were recorded in rad or rem following each catheterization procedure and then zeroed to baseline.

Parameters measured were total biplane fluoroscopy time in minutes and MOSFET dosimeter recordings in rads/rems at each site. Rads/rems were then divided by total minutes to equal patient-acquired rads/rems per total minute per fluoroscopy time.
Patients ranged in age from 1 day to 20 years. Weight ranged from 3 kilograms to 97 kilograms.

Results
In phase one, we examined results from older equipment in which physician preference dictated low-dose fluoroscopy at 15 frames per second pulsed fluoroscopy, versus 30“60 frames per second high-dosed pulsed fluoroscopy. Acquired patient radiation, as measured per the MOSFET system, averaged .925 rads per minute when utilizing low-dose pulsed fluoroscopy. Radiation measured two rads per minutes when utilizing high-dose pulsed fluoroscopy.

Phase two examined acquired patient radiation using a newer, more efficient system which utilizes low-dose fluoroscopy, producing better imaging and a greater ability to store data. There was no physician preference delineation here, as all procedures were performed using low-dose, pulsed fluoroscopy. The average fluoroscopy time was 11.19 minutes. The average acquired rads/rems as measured to MOSFET dosimeters was .85 rads/rems per minute of exposure.

Any reduction in radiation exposure may be significant in decreasing the risks to our patient population, particularly those requiring serial interventions in the catheterization laboratory.

Phase 1 (Figure 1) demonstrates spikes in acquired radiation when high-dose, pulsed fluoroscopy is utilized to obtain optimal imaging. Phase 2 shows the new technology, allowing for improved imaging at low-dose pulsed fluoroscopy.

Discussion
Clearly, unnecessary radiation exposure should be avoided. Children exposed to radiation are at a greater risk of developing cancer than adults due to their rapidly dividing cells and longer life expectancy. Due to their small size, children receive greater gonadal and thyroid exposures from radiation.

Minimizing procedure time and follow-up for those patients exceeding accepted parameters, reducing the x-ray field, placing head and groin shields under the patient and using low-dose pulsed fluoroscopy results in a significant decrease in patient-acquired radiation and an increase in patient safety.

Conclusion
We should continue to evaluate new technologies and advancements to decrease radiation dosing to our patients. As the survival rate of our congenital heart patient population continues to increase, we must remain acutely aware of what we can and should do to provide our patients with the safest possible environment.

Direct measurement, as obtained with the MOSFET system, affords us the ability to measure the decrease in patient-acquired radiation, without image compromise, using newer radiologic equipment at low-dose, pulsed fluoroscopy settings.

Acknowledgements
We would like to thank Arlene Porter, RN, and Jeff Rehbert, BIE, ME, who were helpful with revisions, and Jeff Rehbert for his help with graph production.

Mary Stevens can be contacted at cimds@mindspring.com