Metal implants influence CT scan parameters leading to increased local radiation exposure: A proposal for correction techniques.

Ok Kyu Song,Myeong-Jin Kim,Jin-Young Choi,Yong Eun Chung,Nieun Seo,Mi-Suk Park,Song-Ee Baek,Gayle E Woloschak

doi:10.1371/journal.pone.0221692

Abstract

Metal implants not only deteriorate image quality, but also increase radiation exposure. The purpose of this study was to evaluate the effect of metal hip prosthesis on absorbed radiation dose and assess the efficacy of organ dose modulation (ODM) and metal artifact reduction (MAR) protocols on dose reduction. An anthropomorphic phantom was scanned with and without bilateral metal hip prostheses, and surface and deep level radiation doses were measured at the abdomen and pelvis. Finally, the absorbed radiation doses at pelvic and abdominal cavities in the reference, ODM, and two MAR scans (Gemstone spectral imaging, GE) were compared. The Mann Whitney-U test and Kruskal-Wallis test were performed to compare the volume CT dose index (CTDIvol) and mean absorbed radiation doses. Unilateral and bilateral metal hip prostheses increased CTDIVOL by 14.4% and 30.5%, respectively. MAR protocols decreased absorbed radiation doses in the pelvis. MAR showed the most significant dose reduction in the deep pelvic cavity followed by ODM. However, MAR protocols increased absorbed radiation doses in the upper abdomen. ODM significantly reduced absorbed radiation in the pelvis and abdomen. In conclusion, metal hip implants increased radiation doses in abdominopelvic CT scans. MAR and ODM techniques reduced absorbed radiation dose in abdominopelvic CT scans with metal hip prostheses.

Highlights

The number of total hip replacement surgeries with metal hip joints has gradually increased due to growing elderly populations in developed countries
The purpose of this study is to evaluate the effect of metal hip prosthesis on absorbed radiation doses and to assess the efficacy of organ dose modulation (ODM) and metal artifact reduction (MAR) on dose reduction
Implantation of unilateral and bilateral metal hip prostheses increased the CTDIVOL up to 14.4% and 33.1%, respectively

Summary

Introduction

The number of total hip replacement surgeries with metal hip joints has gradually increased due to growing elderly populations in developed countries. In the United States, 138,700 (142.2/100,000 population) total hip replacements were performed in 2000, and this number increased to 310,800 (257.0/100,000 population) in 2010 [1]. When metal hip replacement patients undergo abdominopelvic CT scans, the metal implants produce an area of photon starvation and beam hardening, resulting in dark and bright streaks that may mask important anatomical structures or lesions in the pelvic cavity [2]. In order to minimize these metal artifacts and improve image quality, metal artifact reduction (MAR) algorithms have been developed and many studies have shown that MARs are effective in reducing metal artifacts [2,3,4,5,6,7,8,9].

Objectives

Methods

Results

Conclusion