Measurement of patient skin dose in vertebroplasty using radiochromic dosimetry film

Abstract

Study design: We studied the radiation doses to which patients were exposed during 17 vertebroplasty operations.

Objective: The radiation doses during vertebroplasty were measured to determine maximum skin dose (MSD), a measure of the likelihood of radiation-induced skin effects.

Summary of background data: Vertebroplasty is performed with use of fluoroscopic guidance for needle placement and to monitor bone cement injection. This procedure requires relatively long duration of fluoroscopic guidance, and so, it demands dose measurements for patients.

Methods: From May 2006 to April 2008, 16 patients (7 men and 9 women; mean age 70.19 years, range 30-87 years) underwent a total of 17 vertebroplasty procedures. Total dose-area product (DAP), duration of fluoroscopy, and the parameters for anteroposterior (AP) and lateral (LAT) fluoroscopic and fluorography projections were recorded for each procedure. Gafchromic films were placed on the patients' skin to measure entrance surface dose and to evaluate the MSD.

Results: The MSD and DAP were higher in the LAT plane than in the AP plane. These results were expected because the fluoroscopy time was longer, and the number of fluorography runs was higher in the LAT plane than in the AP plane.The MSD values for the AP plane ranged between 0.184 Gy and 1.834 Gy, whereas those for the LAT plane ranged between 0.417 Gy and 2.362 Gy. The frequency distribution of values for both planes showed that most MSD values were in the range of 0 to 0.5 Gy and 0.5 to 1 Gy for the AP plane and 0.5 to 1 Gy and 1 to 1.5 Gy for the LAT plane. There was great variability in the MSD at each value for the parameters among individual instances.

Conclusion: When evaluating the MSD to a patient, a distinction should be made between AP and LAT projections, because an overall mean MSD value underestimates the contribution of x-ray absorption on the LAT plane. The use of radiochromic films to estimate radiation damage to the skin has been shown to have the limitation of relying on DAP values only.