Reduction of metal artifacts from knee tumor prostheses on CT images: value of the single energy metal artifact reduction (SEMAR) algorithm

Fang-Ling Zhang,Zhao-Hui Zhang,Ling Ma,Lei Ding,Xiao-Ling Zhang,Ruo-Cheng Li

doi:10.1186/s12885-021-09029-3

Abstract

BackgroundTo evaluate the effect of the single energy metal artifact reduction (SEMAR) algorithm with a multidetector CT (MDCT) for knee tumor prostheses.MethodsFirst, a phantom of knee tumor prosthesis underwent a MDCT scan. The raw data was reconstructed by iterative reconstruction (IR) alone and IR plus SEMAR. The mean value of the CT number and the image noise were measured around the prosthesis at the stem level and articular level. Second, 95 consecutive patients with knee tumor prostheses underwent MDCT scans. The raw data were also reconstructed by the two methods. Periprosthetic structures were selected at the similar two levels. Four radiologists visually graded the image quality on a scale from 0 to 5. Additionally, the readers also assessed the presence of prosthetic complication and tumor recurrence on a same scale.ResultsIn the phantom, when the SEMAR was used, the CT numbers were closer to normal value and the noise of images using soft and sharper kernel were respectively reduced by up to 77.1% and 43.4% at the stem level, and by up to 82.2% and 64.5% at the articular level. The subjective scores increased 1 ~ 3 points and 1 ~ 4 points at the two levels, respectively. Prosthetic complications and tumor recurrence were diagnosed in 66 patients. And the SEMAR increased the diagnostic confidence of prosthetic complications and tumor recurrence (4 ~ 5 vs. 1 ~ 1.5).ConclusionsThe SEMAR algorithm can significantly reduce the metal artifacts and increase diagnostic confidence of prosthetic complications and tumor recurrence in patients with knee tumor prostheses.

Highlights

To evaluate the effect of the single energy metal artifact reduction (SEMAR) algorithm with a multide‐ tector computed tomography (CT) (MDCT) for knee tumor prostheses
The knee tumor prosthesis consists of substantial highdensity metal alloy, which can produce extensive artifacts on CT images because of scattering, photon starvation and x-ray beam hardening [5], which can superimpose upon other structures and result in missed diagnosis of prosthetic complication
We reviewed the plain and enhanced CT images of the knee joint performed on 95 consecutive patients (59 males, 36 females; mean age, 24.2 years; age range, 9–64 years) with modular rotating-hinge knee tumor prostheses retrospectively (Beijing Lidakang Technology Co., Ltd)

Summary

Introduction

To evaluate the effect of the single energy metal artifact reduction (SEMAR) algorithm with a multide‐ tector CT (MDCT) for knee tumor prostheses. The survival rate of patients is currently satisfactory [2,3,4], there are still some potentially serious complications, including prosthetic osteolysis, breakage, infection, periprosthetic fracture, and especially tumor recurrence, meaning that radiologists have to provide a more accurate evaluation of periprosthetic structures and lesions. The knee tumor prosthesis consists of substantial highdensity metal alloy, which can produce extensive artifacts on CT images because of scattering, photon starvation and x-ray beam hardening [5], which can superimpose upon other structures and result in missed diagnosis of prosthetic complication. Various methods have been introduced to reduce the metal artifacts, including higher peak voltage, higher tube charge, MAR algorithms, the dual-energy CT techniques [6]. CT with metal artifact reduction (MAR) and dual-energy techniques are currently used to reduce the metal artifacts

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