title: Does positron emission tomography data acquisition impact simultaneous diffusion-weighted imaging in a whole-body PET/MRI system?
abstract: OBJECTIVE
  The purpose of this study was to test whether the acquisition of positron emission tomography (PET) does interfere with simultaneous diffusion weighted imaging (DWI) in an integrated whole-body PET/MRI system.
  
  
  METHODS
  Fourteen consecutive oncological patients (9 men, 5 women; age 54 ± 13 years ([mean ± standard deviation]) scheduled for routine [(18)F]-FDG PET/CT were prospectively enrolled. For DWI, an echo planar imaging (EPI) sequence (b=0-500-1000 s/mm(2)) was acquired twice on an integrated whole-body 3T PET/MRI system in each patient; first with simultaneous PET acquisition and a second time with the PET component switched off. The apparent diffusion coefficient (ADC) and the signal-to-noise ratio at b=1000 s/mm(2) (SNR) of the myocardium, paraspinal muscle, liver, spleen, renal cortex and tumor tissue (if present) were measured. In addition, the coefficient of variation (CV) of ADC values was calculated. Student's t-test for paired samples was performed to test for differences of the mean ADC, ADC CV and SNR between DWI with and without simultaneous PET acquisition.
  
  
  RESULTS
  There were no significant differences of the ADC [(mean ± standard deviation)] between the DWI acquisitions with and without simultaneous PET acquisition for the myocardium (2572 ± 441 × 10(-6)mm(2)/s and 2586 ± 376 × 10(-6)mm(2)/s, respectively) (P=0.817), paraspinal muscle (1279 ± 254 × 10(-6)mm(2)/s vs. 1219 ± 181 × 10(-6)mm(2)/s) (P=0.318), liver (1245 ± 158 × 10(-6)mm(2)/s vs. 1254 ± 171 × 10(-6)mm(2)/s) (P=0.848), spleen (980 ± 122 × 10(-6)mm(2)/s vs. 1000 ± 187 × 10(-6)mm(2)/s) (P=0.676) and renal cortex (1951 ± 226 × 10(-6)mm(2)/s vs. 1930 ± 273 × 10(-6)mm(2)/s) (P=0.730). Mean ADC of lymph node metastases (n=6) did not differ between with PET acquisition (853 ± 174 × 10(-6)mm(2)/s) and without simultaneous PET (865 ± 170 × 10(-6)mm(2)/s) (P=0.675). There were no significant differences between the CV of ADC values or the SNR values measured in DWI datasets that were acquired with or without simultaneous PET for any evaluated organ site.
  
  
  CONCLUSIONS
  The simultaneous acquisition of DWI and PET on an integrated PET/MRI system does not impact ADC quantification of normal and tumor tissue and does not alter SNR. This knowledge provides a basis for the use of simultaneous multiparametric PET/MRI comprising DWI in diagnostic imaging and quantitative tumor therapy monitoring using repeated ADC measurements.
authors.affiliation: Univ Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, D-40225 Dusseldorf, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Buchbender
authors.forename: Verena
authors.initials: V
authors.lastname: Hartung-Knemeyer
authors.forename: Philipp
authors.initials: P
authors.lastname: Heusch
authors.forename: Till A
authors.initials: TA
authors.lastname: Heusner
authors.forename: Karsten
authors.initials: K
authors.lastname: Beiderwellen
authors.forename: Hans-Joerg
authors.initials: HJ
authors.lastname: Wittsack
authors.forename: Hilmar
authors.initials: H
authors.lastname: Kühl
authors.forename: Michael
authors.initials: M
authors.lastname: Forsting
authors.forename: Andreas
authors.initials: A
authors.lastname: Bockisch
authors.forename: Gerald
authors.initials: G
authors.lastname: Antoch
authors.forename: Rotem S
authors.initials: RS
authors.lastname: Lanzman
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000175:diagnosis*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D051598:Whole Body Imaging / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18