Bagcilar Medical Bulletin (Sep 2021)
The Effectiveness of CT Metal Artifact Reduction Technique and Its Contribution to Radiological Evaluation in Lumbar Stabilization
Abstract
Objective:Metal artifact reduction (MAR) systems, which have been patented by the firms and specific to them, have been developed to reduce the losses in the images, which are caused by artifacts, and to increase the diagnostic value of computed tomography (CT). The objective of this study is to determine the effectiveness of the MAR technique, which minimizes the image loss caused by metal artifacts in CTs taken for the lumbar spinal region where metallic implants are located, and its contributions to radiological evaluation.Method:Patients with spinal stabilization, whose CT imaging records of both standard and smartMAR (SMAR) reconstruction were performed between June 2020 and March 2021 and could be accessed, were evaluated. Critical anatomical structures were defined as: spinal canal (SC), neural foramen (NF), and prevertebral-paravertebral area (P-PA). The image quality of critical anatomical structures were evaluated using a 5-point image quality scale for soft tissue (400/35 HU) and bone window settings (2.500/480 HU) on standard and SMAR reconstructed CT images. In addition, the size of the flame artifact was measured and recorded in millimeters in standard and SMAR images.Results:Of the 24 patients with lumbar spinal stabilization who met the inclusion criteria, 8 were male, and 16 were female (66%). The age range was determined to be between 26 and 82 years (mean=60). The stabilization of all patients was in the form of posterior transpedicular screw and rod fixation. The radiation dose distribution ranged between 3.23 and 14.1 millisieverts (mSv) (mean=8.95 mSv). The worst visualization score was obtained on SC imaging, which was evaluated in the soft tissue window. In bone window evaluations of these structures, the visualization scores (median) in standard and SMAR imaging’s were found to be 3 and 4 (Z=-3.926, p<0.001) for SC, 4 and 5 for NF (Z=-3.666, p<0.001), and 4 and 5 (Z=-4.203, p<0.0001) for P-PA, respectively. These differences were also significant. Bone cortex visualization score (median), measured on bone window images, were determined to be 4 (minimum:2, maximum:5) and 5 (minimum:4, maximum:5) (Z=-4.028, p<0,0001) in standard and SMAR imagings, respectively. As an objective criterion, the flame artifact length, which was evaluated only in bone window images, was 26 mm on average (standard deviation ±9.78) (minimum:8, maximum:54 mm) in standard imaging, whereas it decreased to 3.66 mm (standard deviation ±2.54) (minimum:0, maximum:7 mm) in reconstructions via SMAR.Conclusion:The MAR technique significantly reduces the artifacts occurring with standard techniques in adjacent tissues applied for medical treatment purposes and allows a clearer evaluation of this region by the radiologist. The use of this technique enhances the quality of CT images and the diagnostic value of radiological examination. However, there is a need for the development of MAR software for optimal imaging.
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