title: How Much Is the Dose Varying between Follow-Up CT-Examinations Performed on the Same Scanner with the Same Imaging Protocol?
abstract: OBJECTIVE
  To investigate the dose variation between follow-up CT examinations, when a patient is examined several times on the same scanner with the identical scan protocol which comprised automated exposure control.
  
  
  METHODS
  This retrospective study was approved by the local ethics committee. The volume computed tomography dose index (CTDIvol) and the dose-length-product (DLP) were recorded for 60 cancer patients (29 male, 31 female, mean age 60.1 years), who received 3 follow-up CT examinations each composed of a non-enhanced scan of the liver (LI-CT) and a contrast-enhanced scan of chest (CH-CT) and abdomen (AB-CT). Each examination was performed on the same scanner (Siemens Definition FLASH) equipped with automated exposure control (CARE Dose 4D and CARE KV) using the identical scan protocol.
  
  
  RESULTS
  The median percentage difference in DLP between follow-up examinations was 9.6% for CH-CT, 10.3% for LI-CT, and 10.1% for AB-CT; the median percentage difference in CTDIvol 8.3% for CH-CT, 7.4% for LI-CT and 7.7% for AB-CT (p<0.0001 for all values). The maximum difference in DLP between follow-up examinations was 67.5% for CH-CT, 50.8% for LI-CT and 74.3% for AB-CT; the maximum difference in CTDIvol 62.9% for CH-CT, 47.2% for LI-CT, and 49% for AB-CT.
  
  
  CONCLUSIONS
  A significant variance in the radiation dose occurs between follow-up CT examinations when the same CT scanner and the identical imaging protocol are used in combination with automated exposure control.
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Saravanabavaan
authors.initials: S
authors.lastname: Suntharalingam
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Franz Ferdinand
authors.initials: FF
authors.lastname: Stecker
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Nika
authors.initials: N
authors.lastname: Guberina
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Adrian
authors.initials: A
authors.lastname: Ringelstein
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schlosser
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Jens Matthias
authors.initials: JM
authors.lastname: Theysohn
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Forsting
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Nassenstein
mesh_terms: D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods