Background Interventional X-ray systems used for cardiac catheterisation procedures are operated by pre-programmed automatic dose rate control. Radiographic factors are automatically selected based on imaging geometry and estimated patient thickness - which depends on image projection as well as patient size. Purpose The aim of this research was to determine optimal X-ray beam energy for cardiac image acquisition in a system-independent manner, for a range of paediatric and adult patient sizes. Methods Patients and iodine based contrast medium were simulated using polymethyl methacrylate (PMMA) and tin respectively. X-ray tube voltage (kVp) and Cu X-ray beam filtration were independently varied and images were captured on a flat panel detector based cardiac X-ray imaging system. Tin detail contrast was calculated and flat field image noise was measured to determine the contrast to noise ratio (CNR). Entrance surface and effective dose measurements were obtained to calculate CNR2 / dose, which determined dose efficiency. Results Lower kVp was favoured, more so for thinner PMMA; as Cu increased, lower kVp was favoured. For the smallest phantom (8.5 cm), CNR2 / dose was highest at 50 kVp with 0.4 mm Cu considering both dose measurements. For the largest phantom (30 cm), using 80 kVp with 0.25 mm Cu and 85 kVp with no filtration provided the highest CNR2 / dose for entrance surface and effective dose respectively. Conclusions Optimal beam energy can be used, with X-ray dose adjusted for clinically acceptable image quality and X-ray tube loading limits, for a given task and patient size.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)