title: Low-dose nonenhanced head CT protocol for follow-up evaluation of children with ventriculoperitoneal shunt: reduction of radiation and effect on image quality.
abstract: OBJECTIVE
  Children with a shunt for hydrocephalus often undergo multiple follow-up head CT scans, increasing the risk for long-term effects of ionizing radiation. The purpose of our study was to evaluate if an unenhanced low-dose head CT could consistently provide acceptable image quality and diagnostic information.
  
  
  METHODS
  Ninety-two children (mean age, 9 years; range, 8 months to 21 years; 45 boys and 47 girls) with a shunt for hydrocephalus and no clinical evidence of shunt malfunction who were referred for a follow-up nonenhanced head CT were included in the study. All studies were performed on a 4-section multidetector CT. Two CT studies were selected retrospectively for each patient, 1 performed at standard dose (220 mA) and 1 at low dose (80 mAs). Two radiologists independently evaluated and graded both standard-dose and low-dose studies for various image quality parameters. Attenuation and noise levels were measured, and gray-white differentiation and contrast-to-noise ratio (CNR) were calculated.
  
  
  RESULTS
  Low-dose CT resulted in 63% mean dose reduction. All low-dose CT scans were diagnostically acceptable. Image quality parameters were significantly lower at low dose (P = .0001) except for the parameters for streak artifacts (P = .46) and need for further imaging (P = .47), which were higher. Mean noise levels were significantly higher (P = .001) in low-dose studies, whereas CNR was significantly higher in standard dose CT (P = .001). A moderate to perfect agreement was noted between the 2 readers with regard to image quality assessment (65%-99%).
  
  
  CONCLUSIONS
  Low-dose nonenhanced head CT consistently provides diagnostically acceptable images with relevant diagnostic information in children with VP shunts resulting in substantial dose savings.
authors.affiliation: Emory University Hospital, Atlanta, GA, USA.
authors.forename: U K
authors.initials: UK
authors.lastname: Udayasankar
authors.forename: K
authors.initials: K
authors.lastname: Braithwaite
authors.forename: M
authors.initials: M
authors.lastname: Arvaniti
authors.forename: D
authors.initials: D
authors.lastname: Tudorascu
authors.forename: W C
authors.initials: WC
authors.lastname: Small
authors.forename: S
authors.initials: S
authors.lastname: Little
authors.forename: S
authors.initials: S
authors.lastname: Palasis
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D006849:Hydrocephalus / Q000000981:diagnostic imaging* / Q000601:surgery; D007223:Infant; D008297:Male; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed; D017287:Ventriculoperitoneal Shunt