title: Comparison of image quality between 70 kVp and 80 kVp: application to paediatric cardiac CT.
abstract: OBJECTIVE
  To evaluate noise level and contrast-to-noise ratio (CNR) with various kVp-mAs pairs producing the same computed tomography dose index (CTDI) value. The 80 kVp and new 70-kVp settings were compared.
  
  
  METHODS
  The noise was measured in 10 ovoid water phantoms with different diameters from 10 cm to 28 cm. Contrast was obtained from CTs of iodine-filled tubes. Spiral acquisition protocols at 70 kVp and 80 kVp, with the same CTDI, were applied. In the clinical study, two matched groups, each of 21 paediatric patients, underwent 70-kVp or 80-kVp ECG-gated iodinated-enhanced sequential CT.
  
  
  RESULTS
  Noise was significantly higher with 70 kVp than 80-kVp settings for all phantom sizes. Estimated CNR with phantoms was higher at 70 kVp than 80 kVp, and the difference decreased from 17% to 3% as phantom size increased. The mean CNR in paediatric patients was 15.2 at 70 kVp and 14.3 at 80 kVp (ns). The CNR difference was significantly larger in the small-child subgroup.
  
  
  CONCLUSIONS
  Noise level is slightly higher at the 70-kVp than the 80-kVp setting, but the CNR is higher, particularly for small children. Therefore, 70 kVp may be appropriate for contrast-enhanced CT examinations and 80 kVp for non-enhanced CT in small children.
  
  
  CONCLUSIONS
  70-kVp settings provide a slightly higher noise level compared to 80-kVp settings. The CNR is higher with 70-kVp than with 80-kVp settings. Without contrast, 80-kVp settings may be preferable over 70-kVp settings.
authors.affiliation: Radiology Department, Centre Chirurgical Marie Lannelongue, 133 Avenue de la Résistance, 92350, Le Plessis-Robinson, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Durand
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Paul
mesh_terms: D002648:Child; D002675:Child, Preschool; D003287:Contrast Media; D006330:Heart Defects, Congenital / Q000000981:diagnostic imaging*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007455:Iodine; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards*
chemical_list: D003287:Contrast Media; D007455:Iodine