Speaker
Description
Background
CT images are required to create a radiotherapy treatment plan. Metal hip implants can cause streaking and distortions in CT images, which can lead to inaccuracies in dose calculation and cause difficulties in visualising the target area. Iterative metal artefact reduction (iMAR) is a sophisticated algorithm designed to reduce the negative impact of metal artefacts and improve the qualitative and quantitative information gained from CT imaging. The aim of this work was to investigate the effect of different preset types of iMAR on the assignment of accurate Hounsfield Units (HUs) , spatial resolution and contrast resolution using a commercial image quality phantom and a bespoke 3D-printed pelvic phantom with a single metal hip or bilateral metal hips.
Methods
The commercial image quality phantom was setup within the 3D-printed anatomical pelvic phantom and scanned using a Siemens CT scanner for three setups including a single metal hip, bilateral metal hips and no metal hips. The images were analysed using ImageJ to explore the effects of iMAR on CT image quality.
Results
The Hip iMAR protocol, designed by Siemens, was effective in improving the accuracy of the HUs assigned to materials; for example when looking at the HU assigned to a 3D-printed replica of the prostate and bladder, the streaking caused by the bilateral metal hips had significant impact on the bladder and prostate with both being assigned significantly lower HUs values than expected of -88±64HU and -65±76HU respectively. When the Hip iMAR was introduced, the prostate and bladder values were -10±7HU and 53±8HU which are in line with the expected values of 2±9HU and 63±10HU.
Conclusion
From this investigation, it was established that iMAR is a useful and effective tool for reducing the negative effects of metal artefacts caused by metal hip implants when the Hip iMAR protocol is used.
