title: Low tube voltage CT for improved detection of pancreatic cancer: detection threshold for small, simulated lesions.
abstract: BACKGROUND
  Pancreatic ductal adenocarcinoma is associated with dismal prognosis. The detection of small pancreatic tumors which are still resectable is still a challenging problem.The aim of this study was to investigate the effect of decreasing the tube voltage from 120 to 80 kV on the detection of pancreatic tumors.
  
  
  METHODS
  Three scanning protocols was used; one using the standard tube voltage (120 kV) and current (160 mA) and two using 80 kV but with different tube currents (500 and 675 mA) to achieve equivalent dose (15 mGy) and noise (15 HU) as that of the standard protocol.Tumors were simulated into collected CT phantom images. The attenuation in normal parenchyma at 120 kV was set at 130 HU, as measured previously in clinical examinations, and the tumor attenuation was assumed to differ 20 HU and was set at 110HU. By scanning and measuring of iodine solution with different concentrations the corresponding tumor and parenchyma attenuation at 80 kV was found to be 185 and 219 HU, respectively.To objectively evaluate the differences between the three protocols, a multi-reader multi-case receiver operating characteristic study was conducted, using three readers and 100 cases, each containing 0-3 lesions.
  
  
  RESULTS
  The highest reader averaged figure-of-merit (FOM) was achieved for 80 kV and 675 mA (FOM=0,850), and the lowest for 120 kV (FOM=0,709). There was a significant difference between the three protocols (p<0,0001), when making an analysis of variance (ANOVA). Post-hoc analysis (students t-test) shows that there was a significant difference between 120 and 80 kV, but not between the two levels of tube currents at 80 kV.
  
  
  CONCLUSIONS
  We conclude that when decreasing the tube voltage there is a significant improvement in tumor conspicuity.
authors: Division of Medical Physics, Karolinska University Hospital, Huddinge, Stockholm 14186, Sweden. jon.holm@gmail.com
authors: Jon
authors: J
authors: Holm
authors: Louiza
authors: L
authors: Loizou
authors: Nils
authors: N
authors: Albiin
authors: Nikolaos
authors: N
authors: Kartalis
authors: Bertil
authors: B
authors: Leidner
authors: Anders
authors: A
authors: Sundin
mesh_terms: D021441:Carcinoma, Pancreatic Ductal / Q000000981:diagnostic imaging*; D006801:Humans; D015588:Observer Variation; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*