Quantifying stent-induced dose perturbations in intravascular brachytherapy using 3D- printed phantoms and film dosimetry.

backgroundCoronary artery disease (CAD), the leading cause of death worldwide, is the narrowing of coronary arteries due to atherosclerotic plaque buildup. A common treatment for CAD is percutaneous coronary intervention (PCI), often involving stent placement. However, a common complication or in-stent restenosis (ISR) can occur in 10%-20% of patients which call for the use of therapies like intravascular brachytherapy (IVBT). IVBT delivers targeted beta radiation, typically from Sr-90/Y-90 sources, to inhibit neointimal hyperplasia and reduce restenosis rates. Accurate dose delivery is critical to treatment success, but challenges such as source positioning and dose uniformity persist. Recent advances in 3D printing and radiochromic film dosimetry offer promising tools for more precise dose verification in IVBT, enabling high-resolution assessment of dose distributions and stent-induced perturbations. PURPOSE: IVBT requires precise position to ensure effective treatment. However, stents introduce complexities in dose distribution due to their material and geometry, which can lead to attenuation and impact treatment outcomes. This study aimed to quantify stent-induced dose perturbations using a custom 3D-printed stent phantom and Gafchromic EBT-4 Film, providing insights for dosimetry of IVBT.

methodsDose measurements were conducted using a custom designed 3D-printed stent phantom. The film calibration was performed using the RIT film dosimetry package from 0 to 12 Gy. The phantom was designed for a Synergy XD Stent with a diameter of 3 mm with the Sr-90/Y-90 source catheter position designed to be in the center of the stent. Percent depth dose (PDD) distributions were modeled using the third-order exponential polynomial function and compared with Monte Carlo simulations to evaluate agreement. Discrepancies were quantified using root mean square error (RMSE) and mean absolute error (MAE). The stent effect on PDD was analyzed using a paired t-test, and a dose reduction factor (DRF) was calculated to assess attenuation.

resultsThe third-order exponential polynomial function demonstrated an excellent fit for both configurations, with R-squared values of 0.999 (no stent) and 0.999 (with stent). RMSE and MAE values were slightly higher for the with-stent dataset (0.038 and 0.036, respectively), reflecting increased discrepancies. The paired t-test showed a statistically significant difference between PDD values (t = -6.591, p < 0.0001). The average PDD difference between configurations was 4.26% in the clinically relevant region (2-5 mm). The DRF ranged from 1.18% to 7.92%, with an average attenuation of 4.5%.

conclusionThe presence of a stent significantly impacts dose delivery in IVBT, attenuating approximately 4.5% of the dose within clinically relevant depths. These findings highlight the importance of accounting for stent-induced attenuation in treatment planning to ensure accurate dose delivery. The custom stent phantom demonstrates its usefulness in capturing dose perturbations, offering an effective tool for improving IVBT dosimetry.