title: Real-time co-registration using novel ultrasound technology: ex vivo validation and in vivo applications.
abstract: OBJECTIVE
  The study objective was to evaluate whether a novel global position system (GPS)-like position-sensing technology will enable accurate co-registration of images between imaging modalities. Co-registration of images obtained by different imaging modalities will allow for comparison and fusion between imaging modalities, and therefore has significant clinical and research implications. We compared ultrasound (US) and magnetic resonance imaging (MRI) scans of carotid endarterectomy (CEA) specimens using a novel position-sensing technology that uses an electromagnetic (EM) transmitter and sensors mounted on a US transducer. We then evaluated in vivo US-US and US-MRI co-registration.
  
  
  METHODS
  Thirteen CEA specimens underwent 3.0 Tesla MRI, after which images were uploaded to a LOGIQ E9 3D (GE Healthcare, Wauwatosa, WI) US system and registered by identifying two to three common points. A similar method was used to evaluate US-MRI co-registration in patients with carotid atherosclerosis. For carotid intima-media thickness (C-IMT) measurements, 10 volunteers underwent bilateral carotid US scans co-registered to three-dimensional US maps created on the initial visit, with a repeat scan 2 days later.
  
  
  RESULTS
  For the CEA specimens, there was a mean of 20 (standard error [SE] 2.0) frames per MRI slice. The mean frame difference, over 33 registration markers, between MRI and US scans for readers 1 and 2 was -2.82 ± 19.32 and 2.09 ± 14.68 (mean ± 95% CI) frames, respectively. The US-MRI intraclass correlation coefficients (ICCs) for the first and second readers were 0.995 and 0.997, respectively. For patients with carotid atherosclerosis, the mean US frames per MRI slice (9 [SE 2.3]) was within range of that observed with CEA specimens. Inter-visit, intra-reader, and inter-reader reproducibility of C-IMT measurements were consistently high (side-averaged ICC >0.9).
  
  
  CONCLUSIONS
  Accurate co-registration between US and other modalities is feasible with a GPS-like technology, which has significant clinical and research applicability.
authors: Baylor College of Medicine, 6565 Fannin Street, Houston, TX 77030, USA.
authors: Eric Y
authors: EY
authors: Yang
authors: Venkateshwar R
authors: VR
authors: Polsani
authors: Michael J
authors: MJ
authors: Washburn
authors: William
authors: W
authors: Zang
authors: Anne L
authors: AL
authors: Hall
authors: Salim S
authors: SS
authors: Virani
authors: Megan D
authors: MD
authors: Hodge
authors: Dan
authors: D
authors: Parker
authors: William S
authors: WS
authors: Kerwin
authors: Gerald M
authors: GM
authors: Lawrie
authors: Zsolt
authors: Z
authors: Garami
authors: Christie M
authors: CM
authors: Ballantyne
authors: Joel D
authors: JD
authors: Morrisett
authors: Vijay
authors: V
authors: Nambi
mesh_terms: D002340:Carotid Artery Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D059168:Carotid Intima-Media Thickness; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D019047:Phantoms, Imaging; D058226:Plaque, Atherosclerotic / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D018608:Ultrasonography, Doppler / Q000379:methods*