title: Quantitative Comparison of Misregistration in Abdominal and Pelvic Organs Between PET/MRI and PET/CT: Effect of Mode of Acquisition and Type of Sequence on Different Organs.
abstract: OBJECTIVE
  The objective of our study was to quantitatively compare misregistration in selected abdominopelvic organs between PET/CT acquisitions and simultaneous and sequential PET/MRI acquisitions.
  
  
  METHODS
  PET/MR images of 15 healthy volunteers and seven patients with bladder cancer were acquired. Ten clinical PET/CT studies acquired during the same time frame of body mass index-matched control subjects were chosen. PET/MRI and PET/CT registration of selected abdominopelvic organs was measured and compared.
  
  
  RESULTS
  The overall mean misregistration with PET/MRI was significantly higher than that with PET/CT (p < 0.001). Sequential PET/MRI acquisition was significantly inferior to PET/CT (p = 0.02), whereas there was no significant difference between simultaneous PET/MRI acquisition and PET/CT (p = 0.38). Simultaneous PET/MRI acquisition was significantly better than sequential PET/MRI acquisition (p < 0.001). The mean misregistration for all organs with the T1-weighted volumetric interpolated breath-hold examination (VIBE) sequence (2.39 cm) was significantly inferior to PET/CT (p < 0.001). Although the T2-weighted HASTE breath-hold sequence was significantly inferior to PET/CT (p = 0.04), the T2 HASTE non-breath-hold sequence and T2 STIR sequence (0.18 cm) were significantly superior to both PET/CT and the T1 VIBE sequence (p < 0.001). Within the same sequence (T1 VIBE breath-hold sequence), the mean misregistrations with sequential and simultaneous PET/MRI acquisitions were both significantly greater than with PET/CT (p < 0.001), whereas simultaneous PET/MRI acquisition was superior to sequential PET/MRI acquisition (p < 0.001).
  
  
  CONCLUSIONS
  In the abdominopelvic organs, sequentially obtained PET/MRI data have significantly higher misregistration than both PET/CT data and simultaneously acquired PET/MRI data. Simultaneously obtained PET/MRI data are statistically noninferior to PET/CT. Nonradial T1 VIBE has the highest misregistration, whereas T2 STIR and T2 HASTE non-breath-hold are significantly better than both PET/CT and T1 VIBE.
authors.affiliation: 1 Department of Radiology, University of North Carolina, 101 Manning Dr, 2107 Old Clinic Bldg, CB 7510, Chapel Hill, NC 27599-7510.
authors.forename: Pinakpani
authors.initials: P
authors.lastname: Roy
authors.affiliation: 1 Department of Radiology, University of North Carolina, 101 Manning Dr, 2107 Old Clinic Bldg, CB 7510, Chapel Hill, NC 27599-7510.|2 Department of Diagnostic Imaging, National University of Singapore, Singapore.
authors.forename: Joseph K T
authors.initials: JK
authors.lastname: Lee
authors.affiliation: 1 Department of Radiology, University of North Carolina, 101 Manning Dr, 2107 Old Clinic Bldg, CB 7510, Chapel Hill, NC 27599-7510.|3 Department of Radiology, Columbia Presbyterian Hospital, New York, NY.
authors.forename: Arif
authors.initials: A
authors.lastname: Sheikh
authors.affiliation: 1 Department of Radiology, University of North Carolina, 101 Manning Dr, 2107 Old Clinic Bldg, CB 7510, Chapel Hill, NC 27599-7510.
authors.forename: Weili
authors.initials: W
authors.lastname: Lin
mesh_terms: D000005:Abdomen; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed; D001749:Urinary Bladder Neoplasms / Q000175:diagnosis*
keywords: MRI; PET; PET/MRI; abdomen; artifacts; misregistration; pelvis; quality control