Abstract
IntroductionTo design a custom phantom of the coronary arteries to optimize CT coronary angiography (CCTA) protocols. MethodsCharacteristics of the left and right coronary arteries (mean Hounsfield Unit (HU) values and diameters) were collected from consecutive CCTA examinations (n = 43). Four different materials (two mixtures of glycerine, gelatine and water, pig hearts, Ecoflex™ silicone) were scanned inside a Lungman phantom using the CCTA protocol to find the closest model to in vivo data. A 3D printed model of the coronary artery tree was created using CCTA data by exporting a CT volume rendering into Autodesk Meshmixer™ software. The model was placed in an acid bath for 5 h, then covered in Ecoflex™, which was removed after drying. Both the Ecoflex™ and pig heart were later filled with a mixture of contrast (Visipaque 320 mg I/ml), NaCl and gelatin and scanned with different levels of tube current and iterative reconstruction (ASiR-V). Objective (HU, noise and size (vessel diameter) and subjective analysis were performed on all scans. ResultsThe gelatine mixtures had HU values of 130 and 129, Ecoflex™ 65 and the pig heart 56. At the different mA/ASiR-V levels the contrast filled Ecoflex™ had a mean HU 318 ± 4, noise 47±7HU and diameter of 4.4 mm. The pig heart had a mean HU of 209 ± 5, noise 38±4HU and a diameter of 4.4 mm. With increasing iterative reconstruction level the visualisation of the pig heart arteries decreased so no measurements could be performed. ConclusionThe use of a 3D printed model of the arteries and casting with the Ecoflex™ silicone is the most suitable solution for a custom-designed phantom. Implications for practiceCustom designed phantoms using 3D printing technology enable cost effective optimisation of CT protocols.
Highlights
To design a custom phantom of the coronary arteries to optimize computed tomography (CT) coronary angiography (CCTA) protocols
While modern computed tomography (CT) scanners are equipped with increasingly complex technology, it is important that CT radiographers understand the impact different acquisition parameters have on each other, to ensure adherence to the ALARA principle of radiation protection,[1] considering both image quality and radiation dose
Coronary CT angiography (CCTA) is a minimally invasive examination compared to invasive coronary angiography and its use is growing considerably in light of recent clinical guidelines.[7]
Summary
To design a custom phantom of the coronary arteries to optimize CT coronary angiography (CCTA) protocols. Four different materials (two mixtures of glycerine, gelatine and water, pig hearts, EcoflexTM silicone) were scanned inside a Lungman phantom using the CCTA protocol to find the closest model to in vivo data. The model was placed in an acid bath for 5 h, covered in EcoflexTM, which was removed after drying Both the EcoflexTM and pig heart were later filled with a mixture of contrast (Visipaque 320 mg I/ml), NaCl and gelatin and scanned with different levels of tube current and iterative reconstruction (ASiR-V). Conclusion: The use of a 3D printed model of the arteries and casting with the EcoflexTM silicone is the most suitable solution for a custom-designed phantom. Regular optimization of CCTA is a necessity due to the constantly new technical developments that accrue in CT, coupled with reports of heterogenous radiation dose and image quality between imaging sites.[8]
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