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Influence of Metal Artifacts Reduction Algorithm (MAR) On CT Number (Hounsfield Unit) Accuracy

R Holla1*, D Khanna2 , V Naik1 , B Pillai1 , (1)Amrita Institute of Medical Sciences,Amrita Vishwa Vidyapeetham, Kochi, Ernakulam, Kerala(2) Karunya University, Coimbatore, Tamilnadu


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: Metal Artifacts can seriously degrade the quality of CT images which can make the images diagnostically unusable. For an optimal image quality, artifacts occurred due to metal implants need to be suppressed. In the following studies two metal artifact reduction algorithms(MAR) SMAR (Smart Metal Artifacts Reduction) on GE optima 580W and OMAR (Orthopedic –Metal Artifact Reduction) on Philips iCT 256 were used. The influence of these algorithms on the CT number was studied.

Methods: Gammex 467 (Middleton, WI 53562, USA) tissue characterization phantom having different characterized tissue rods were scanned at GE optima 580W and Philips ICT 256 CT scanners. The CT numbers were measured for all the tissue characterization rods without the artifacts. The titanium and stainless steel rods were introduced to simulate the metal artifacts in the phantom and CT scan was obtained. The scanned images were reconstructed using metal artifact reduction algorithms on both the CT scanners. The procedure was repeated for 80,100.120, & 140 KVp tube potentials. The influence of MAR on the CT number for various tissue rods were investigated.

Results: For 80 KVp it was observed that after applying SMAR for titanium artifacts the mean HU error was 280HU for Cortical Bone, whereas the same error was less than 45HU for Philips OMAR. For 100KVp and above, no significant variation on CT numbers were observed for both the metal reduction algorithms.

Conclusion: The changes in the reconstructed CT numbers will influence the dose calculation when we use these CT scans for patient dosimetry in Radiotherapy.


Reconstruction, CT


IM- CT: Image Reconstruction

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