Temporal Trends in X-Ray Exposure during Coronary Angiography and Percutaneous Coronary Intervention

Abstract

Background: Percutaneous coronary intervention exposes patient and staff to ionizing radiation. Although staff only receive a small fraction of patient dose through scatter radiation, there are concerns about the potential health effects of repeated exposure. Minimizing both patient and occupational exposure is needed.

Objective: This article investigates patient and operator X-ray exposure over time in coronary intervention in relation to upgraded X-ray equipment, improved shielding, and enhanced operator awareness.

Materials and methods: Data regarding irradiation time, patient dose, and patient characteristics were extracted from the Norwegian Registry for Invasive Cardiology (NORIC) for procedures performed from 2013 to mid-2019. Personal operator dosimetry records were provided by the Norwegian Radiation and Nuclear Safety Authority. Improved operator shielding and awareness measures were introduced in 2018.

Results: In the period 2013 through June 2019, 21499 procedures were recorded in our institution. Mean dose area product (DAP) for coronary angiography decreased 37% from 2981 μGy·m² in 2013 to 1891 μGy·m² in 2019 (p < 0.001). For coronary intervention, DAP decreased 39% from 8358 μGy·m² to 5055 μGy·m². Personal dosimetry data indicate a 70% reduction in operator dose per procedure in 2019 compared to 2013. The most pronounced reduction occurred after improved radiation protection measures were implemented in 2018 (-48%).

Conclusions: This study shows a temporal trend towards considerable reduction in X-ray doses received by the patient and operator during cardiac catheterization. Upgraded X-ray equipment, improved shielding, and enhanced operator awareness are likely contributors to this development.

Figure 1

Trends in dose area product (DAP) and irradiation time per procedure. Between 2013 and 2019, there was a trend towards reduced DAP per procedure (a). On average, yearly reduction in DAP per procedure was 620 μGy·m² in PCI (p < 0.001) and 200 μGy·m² in coronary angiography (p < 0.001). Dots represent mean DAP per procedure. The linear regression line and standard error were calculated on the entire dataset (n = 20709). For irradiation time (b), there was a small but significant trend towards a reduction in irradiation time of 11 seconds per procedure per year in angiography (p < 0.001).

Figure 2

Influence of patient weight on dose area product (DAP) and irradiation time. Patient weight had a strong correlation to DAP (a). The dots represent the mean DAP for all patients with a specific weight. The linear regression line and standard error were calculated on the entire dataset (n = 20 709). Each additional kilogram patient weight leads to an increase in 130 μGy·m² in PCI and 56 μGy·m² in coronary angiography (p < 0.001).Patient weight had only a minor influence on irradiation time (b).

Figure 3

Influence of C-arm upgrade on dose area product (DAP). Boxplot representing DAP per procedure in the three cath labs at our institution before and after C-arm upgrade. Newer C-arms were associated with lower DAP per procedure both in isolated coronary angiography (a) and in PCI (b). Cath Lab 1, Siemens Axiom Artis dBC installed in 2006 was replaced with a Philips Azurion 7 B12/12 in 2018, which led to a 50% reduction of mean DAP in angiography and 41% in PCI (p < 0.001). Cath Lab 3, Siemens Artis Axiom dFC installed in 2005 was replaced in 2016 with a Siemens Artis Q. Mean doses on the new lab was 28% lower in angio and 32% lower in PCI (p < 0.001). Cath Lab 2, Philips Allura Xper FD10C installed in 2009 did not undergo an upgrade.

Figure 4

Improved operator shielding setup. Large ceiling-mounted protective shield with panel curtains on the lower end was installed in all cath labs in 2016. Pelvic lead apron was introduced as a standard of care at our center in 2018. Wheel-mounted mobile shield to the left of the operator was used at operator's discretion.

Figure 5

Trends in operator exposure. The ratio between received operator dose and given dose (mSv/DAP) is presented to assess the effects of operator shielding and is not affected by procedure numbers or irradiation time. (a) Pooled trends for mSv/DAP (in red-left, y-axis) and mSv/procedure (blue-right, y-axis) for all operators and fellows working in the cath lab. Between 2013 and 2019, there was a change in mSv/DAP from 4.48 × 10⁻⁶ mSv/μGy·m² to 1.98 × 10⁻⁶ mSv/μGy·m², which corresponds to a 56% reduction (p=0.02). The reduction in mSv/procedure was larger at 70% (p=0.004) as it is influenced by reduced given dose (DAP) per procedure. (b) Interoperator variability between consultants employed throughout the period.