Does the use of additional X-ray beam filtration during cine acquisition reduce clinical image quality and effective dose in cardiac interventional imaging?

Effective dose and image quality for different patient sizes during AP upper abdominal radiography: A phantom study

INTRODUCTION

Undertaking medical imaging examinations on obese patients can present practical challenges. Choosing optimal imaging protocols can be difficult, especially when promoting the ALARA principle. The aim of this study was to assess the effects of increasing body part thickness on image quality (IQ) and effective dose (ED) during upper abdominal radiography. A secondary aim was to determine the optimum exposure settings for larger sized patients.

METHODS

Underweight, standard, overweight and obese abdomen sizes were simulated using an anthropomorphic upper abdomen phantom, without and with additional fat layers (6, 10 and 16 cm). Phantoms were imaged using a variety of tube potentials (70-110 kVp), automatic exposure control (AEC) and a source-to-image distance of 120 cm. IQ was assessed visually using a relative visual grading analysis (VGA) method. Radiation dose was evaluated by calculating the ED using the Monte Carlo PCXMC 2.0 computer program.

RESULTS

IQ values showed a statistical reduction (p = 0.006) with increasing phantom size across all examined tube potentials. The highest IQ scores (3.3, 2.8, 2.5 and 2.2, respectively) were obtained at 70/75 kVp for all phantom thicknesses. As tube potential increased the IQ was also shown to decrease. ED showed a statistically significant increase (p < 0.001) with increasing phantom thicknesses.

CONCLUSION

Higher EDs were evident when applying lower tube potentials. Using an AEC with high tube potentials (105/110 kVp) can lead to a considerable decrease in ED with acceptable IQ when undertaking upper abdomen radiography on patients with large body part thicknesses.

IMPLICATION FOR PRACTICE

Applying higher values of tube potentials for patients who have a thicker abdomen can lead to decreased ED.

The role of a commercial radiation dose index monitoring system in establishing local dose reference levels for fluoroscopically guided invasive cardiac procedures

PURPOSE

The primary goal was to evaluate local dose level for fluoroscopically guided invasive cardiac procedures in a high-volume activity catheterization laboratory, using automatic data registration with minimal impact on operator workload. The secondary goal was to highlight the relationship between dose indices and acquisition parameters, in order to establish an effective strategy for protocols optimization.

METHODS

From September 2016 to December 2018, a dosimetric survey was conducted in the 2 rooms of the catheterization laboratory of our institution. Data collection burden was minimized using a commercial Radiation Dose Index Monitoring System (RDIMs) that analyzes dicom files automatically sent by the x-ray equipment. Data were combined with clinical information extracted from the HIS records reported by the interventional cardiologist. Local dose levels were established for different invasive cardiac procedures.

RESULTS

A total of 3029 procedures performed for 2615 patients were analyzed. Median KAP were 21 Gycm² for invasive coronary angiography (ICA) procedures, 61 Gycm² for percutaneous coronary intervention (PCI) procedures, 59 Gycm² for combined (ICA+PCI) procedures, 87 Gycm² for structural heart intervention (TAVI) procedures. A significant dose reduction (51% for ICA procedures and 58% for PCI procedures) was observed when noise reduction acquisition techniques were applied.

CONCLUSIONS

RDIMs are effective tools in the establishment of local dose level in interventional cardiology, as they mitigate the burden to collect and register extensive dosimetric data and exposure parameters. Systematic review of data support the multi-disciplinary team in the definition of an effective strategy for protocol management and dose optimization.

Equivalent thicknesses of beam hardening filters consisting of aluminium, copper, Al/Cu and Al/Gold combinations and plumbiferous acrylic for 40 to 150 kVp diagnostic spectra

PURPOSE

Beam hardening filters used to reduce patient doses typically consist of aluminium, copper, or a combination of both. Optically transparent filters containing lead in plumbiferous acrylic became available. One vendor also uses a combination of aluminium and gold. Data is provided to compare filter thicknesses in terms of half-value layer (HVL) for clinically relevant kVp.

METHODS

Equivalent filter thicknesses were defined by identical kVp and 1st HVL. Equivalent copper filter thicknesses were calculated for aluminium and typical filters found in radiographic and interventional systems. A verified semi-empirical spectrum calculation programme and National Institute of Standards and Technology (NIST) mass attenuation coefficients were applied. Lead acrylic filters were simulated by a two-component model of acrylic plus lead with mass thicknesses determined by matching 1 HVLs in Al at RQR5 using filter specifications.

RESULTS

Coefficients are provided to convert mm Cu to mm Al and vice versa for tube potentials from 40 to 150 kVp. 1 mm Al corresponds to 27.8 ± 1 μm Cu over the entire energy range simulated. Using this simple model as opposed to simulations of all individual filters made from Al/Cu combinations (1 and 2 mm Al, 1 Al + 0.1 and 0.2 Cu, 1.5 Al plus 0.3 and 0.6 Cu, 2 Al plus 0.1 Cu) for the entire energy range results in differences in equivalent Cu thicknesses below 4 μm Cu (3 μm for 50-150 kVp). kVp dependence is larger for filters containing larger Z elements. 1 mm Al plus 10 μm gold used by Shimadzu corresponds to 75-80 μm Cu, depending on kVp; plumbiferous acrylic with nominal filtrations of 1 Al plus 0.1 Cu, and 1 Al plus 0.2 Cu corresponded to 124-132 μm, and 206-232 μm Cu, respectively.

CONCLUSIONS

Experimental verification of the equivalence of aluminium and combined aluminium plus copper filters showed excellent agreement between calculated copper equivalent thickness and measurements with copper filters for clinical beams from 40 to 150 kVp.