title: Magnetic resonance imaging (MRI) artefacts in hip prostheses: a comparison of different prosthetic compositions.
abstract: OBJECTIVE
  The purpose of the study was to compare the artefacts produced by different hip prostheses on magnetic resonance imaging (MRI).
  
  
  METHODS
  An identical MRI protocol was used to perform a quali-quantitative in vitro evaluation of artefacts caused by different hip prosthetic materials at different field strengths: prosthesis number 1, composed of cobalt-chrome-molybdenum (head and stem); prosthesis number 2, composed of ceramic (head) and titanium (stem); prosthesis number 3, composed of cobalt-chrome (head) and titanium (stem). All prostheses were imaged with both a clinical 1 Tesla (T) (Signa Horizon, General Electrics) and 1.5 T (Achieva, Philips) MRI system, using spin echo (SE) and gradient echo (GRE) sequences: sagittal T1 SE, coronal T2 fast SE (FSE), axial T1 SE, axial T2 FSE, sagittal T2 GRE, axial T2* GRE, coronal T1 GRE, axial T1 GRE. The artefacts produced by each prosthesis were assessed in each sequence at the different field strengths, by measuring the two longest diameters of the artefact in each section and sequence and comparing them to the actual diameters so as to obtain a ratio expressing the effective degree of artefact.
  
  
  RESULTS
  Cobalt-chrome produced the largest artefacts both in SE (1.73 at 1 T and 2.37 at 1.5 T) and GRE sequences (2.8 at 1 T and 3.06 at 1.5 T) followed by titanium (SE, 1.6 at 1 T, 2.13 at 1.5 T; GRE, 2 at 1 T, 2.94 at 1.5 T) and cobalt-chrome-molybdenum (SE, 1.51 at 1 T, 1.67 at 1.5 T; GRE, 2.13 at 1 T and 2.48 at 1.5 T); ceramic produced the smallest artefacts in all sequences (SE, 1.0 at 1 T and 1.18 at 1.5 T; GRE, 1.3 at 1 T and 1.22 at 1.5T). Increasing the magnetic field strength, titanium showed the greatest variations in artefact size, and ceramic the smallest ones.
  
  
  CONCLUSIONS
  The composition of prosthetic implants is decisive in determining the quality of MR imaging.
authors.affiliation: Scuola di Specializzazione in Radiodiagnostica, Università Politecnica delle Marche, Ancona, Italy, ellisbi83@gmail.com.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Panfili
authors.forename: Laura
authors.initials: L
authors.lastname: Pierdicca
authors.forename: Luca
authors.initials: L
authors.lastname: Salvolini
authors.forename: Luigi
authors.initials: L
authors.lastname: Imperiale
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Dubbini
authors.forename: Andrea
authors.initials: A
authors.lastname: Giovagnoni
mesh_terms: D016477:Artifacts; D002857:Chromium; D003035:Cobalt; D006622:Hip Prosthesis; D006801:Humans; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging; D008982:Molybdenum; D011474:Prosthesis Design; D014025:Titanium
chemical_list: D002857:Chromium; D003035:Cobalt; D008982:Molybdenum; D014025:Titanium