Effect of an optimized X-ray blanket design on operator radiation dose in cardiac catheterization based on real-world angiography

Abstract

Background: There is increasing concern and focus in the interventional cardiology community on potential long term health issues related to radiation exposure and heavy wearable protection. Optimized shielding measures may reduce operator dose to levels where lighter radioprotective garments can safely be used, or even omitted. X-ray blankets (XRB) are commercially available but suffer from small size and lack of stability. A larger XRB may reduce operator dose but could hamper vascular access and visualization. The aim of this study is to assess shielding effect of an optimized XRB during cardiac catheterization and estimate the potential reduction in annual operator dose based on DICOM Radiation Dose Structured Report (RDSR) data reflecting everyday clinical practice.

Methods: Data accumulated from 7681 procedures over three years in our RDSR repository was used to identify projection angles and radiation doses during cardiac catheterization. Using an anthropomorphic phantom and a scatter radiation detector, radiation dose to the operator (mSv) and patient (dose area product-DAP) was measured for each angiographic projection for three different shielding setups. Relative operator dose (mSv/DAP) was calculated and multiplied by DAP per projection to estimate effect on operator dose.

Results: Adding an optimized XRB to a standard shielding setup comprising a table- and ceiling-mounted shield resulted in a 94.9% reduction in estimated operator dose. The largest shielding effect was observed in left and cranial projections where the ceiling-mounted shield offered less protection.

Conclusions: An optimized XRB is a simple shielding measure that has the potential to reduce operator dose.

Fig 1. Illustration of measurement setup.

A 60x60cm X-ray blanket (flexible features not shown) is positioned just caudally to the image detector, and the X2 Survey sensor in the center of the photo is placed 140cm above the floor, 40cm caudally and laterally to the center of the primary beam. This corresponds to the position of the operator’s left shoulder during cardiac catheterization using a right radial approach.

Fig 2. C-arm angulation and percentage DAP in each projection.

Panel A: Scatterplot showing the precise C-arm angulation of 200 000 random samples out of 784 154 exposures. Only a sample was plotted to avoid overplotting and improve visualization. Although a large variation in C-arm angulation is present, it is easy to visualize the natural grouping categories. Panel B: Percentage DAP recorded in each projection. LAO (21.4%) and RAO-CRAN (14%) are where most patient doses are given.

Fig 3. Relative operator dose according to angiographic projection and shielding setup.

Each measurement was repeated five times and all measured values are individually plotted. The plot shows that standard shielding is least effective in left and cranial projections (CRAN, LAO, LAO-CRAN), whereas with the XRB the relative operator dose is consistently low. Thus, the XRB is more effective in the projections where the standard shielding has least effect.

Fig 4. Annual operator dose estimates according to shielding setup.

Calculations are based on a case load of 500 procedures / year and mean DAP per procedure 36 102 mGycm². A: Adding an X-ray blanket (XRB) to standard shielding resulted in a 94.9% reduction in annual operator dose. B: Contribution of each projection to annual operator dose. The percentage above the red columns represent percent reduction with an XRB compared to standard shielding. In the standard setup, CRAN, LAO and LAO-CRAN are responsible for the majority (86%) of operator dose. These are the projections where the ceiling-mounted shield is least effective and where adding an XRB leads to the largest incremental reduction in operator dose.