title: Penile biometry on prenatal magnetic resonance imaging.
abstract: OBJECTIVE
  In view of the implementation of magnetic resonance imaging (MRI) as an adjunct to ultrasonography in prenatal diagnosis, this study sought to demonstrate normal penile growth on prenatal MRI.
  
  
  METHODS
  This was a retrospective study of MRI of 194 male fetuses (18-34 weeks' gestation) with normal anatomy or minor abnormalities. On sagittal T2-weighted MRI sequences, we measured penile length from the glans tip to the scrotal edge (outer length) and from the glans tip to the symphyseal border (total length). Descriptive statistics, as well as correlation and regression analysis, were used to evaluate penile length in relation to gestation. T-tests were calculated to compare mean outer/total length on MRI with published ultrasound data.
  
  
  RESULTS
  Mean length values, including 95% CIs and percentiles, were defined. Penile length as a function of gestational age was expressed by the following regression equations: outer mean length = - 5.514 + 0.622 × gestational age in weeks; total mean length = - 8.865 + 1.312× gestational age in weeks. The correlation coefficients, r = 0.532 and r = 0.751, respectively, were statistically significant (P < 0.001). Comparison of outer penile length on MRI with published ultrasound penile length data showed no significant differences, while total penile length on MRI was significantly greater than ultrasound penile length (P < 0.001).
  
  
  CONCLUSIONS
  Our MRI results provide a reference range of fetal penile length, which, in addition to ultrasonography, may be helpful in the identification of genital anomalies. Outer penile length on MRI is equivalent to penile length measured on ultrasound, whereas total length is significantly greater.
authors.affiliation: Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Vienna, Austria. stefan.nemec@meduniwien.ac.at
authors.forename: S F
authors.initials: SF
authors.lastname: Nemec
authors.forename: U
authors.initials: U
authors.lastname: Nemec
authors.forename: M
authors.initials: M
authors.lastname: Weber
authors.forename: P C
authors.initials: PC
authors.lastname: Brugger
authors.forename: D
authors.initials: D
authors.lastname: Bettelheim
authors.forename: S
authors.initials: S
authors.lastname: Rotmensch
authors.forename: C R
authors.initials: CR
authors.lastname: Krestan
authors.forename: D L
authors.initials: DL
authors.lastname: Rimoin
authors.forename: J M
authors.initials: JM
authors.lastname: Graham
authors.forename: D
authors.initials: D
authors.lastname: Prayer
mesh_terms: D001699:Biometry; D005260:Female; D005832:Genital Diseases, Male / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000196:embryology; D005865:Gestational Age; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010413:Penis / Q000000981:diagnostic imaging / Q000196:embryology / Q000254:growth & development*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012732:Sex Determination Analysis / Q000379:methods; D016216:Ultrasonography, Prenatal