title: Computer-aided pulmonary nodule detection - performance of two CAD systems at different CT dose levels.
abstract: OBJECTIVE
  To evaluate the impact of dose reduction on the performance of computer-aided lung nodule detection systems (CAD) of two manufacturers by comparing respective CAD results on ultra-low-dose computed tomography (ULD-CT) and standard dose CT (SD-CT).
  
  
  METHODS
  Multi-slice computed tomography (MSCT) data sets of 26 patients (13 male and 13 female, patients 31 - 74 years old) were retrospectively selected for CAD analysis. Indication for CT examination was staging of a known primary malignancy or suspected pulmonary malignancy. CT images were consecutively acquired at 5 mAs (ULD-CT) and 75 mAs (SD-CT) with 120 kV tube voltage (1 mm slice thickness). The standard of reference was determined by three experienced readers in consensus. CAD reading algorithms (pre-commercial CAD system, Philips, Netherlands: CAD-1; LungCARE, Siemens, Germany: CAD-2) were applied to the CT data sets.
  
  
  RESULTS
  Consensus reading identified 253 nodules on SD-CT and ULD-CT. Nodules ranged in diameter between 2 and 41 mm (mean diameter 4.8 mm). Detection rates were recorded with 72 % and 62 % (CAD-1 vs. CAD-2) for SD-CT and with 73 % and 56 % for ULD-CT. Median false positive rates per patient were calculated with 6 and 5 (CAD-1 vs. CAD-2) for SD-CT and with 8 and 3 for ULD-CT. After separate statistical analysis of nodules with diameters of 5 mm and greater, the detection rates increased to 83 % and 61 % for SD-CT and to 89 % and 67 % for ULD-CT (CAD-1 vs. CAD-2). For both CAD systems there were no significant differences between the detection rates for standard and ultra-low-dose data sets (p > 0.05).
  
  
  CONCLUSIONS
  Dose reduction of the underlying CT scan did not significantly influence nodule detection performance of the tested CAD systems.
authors.affiliation: Institut für Radiologie, Charité Campus Mitte, Charité-Universitätsmedizin Berlin. patrick.hein@charite.de
authors.forename: P A
authors.initials: PA
authors.lastname: Hein
authors.forename: P
authors.initials: P
authors.lastname: Rogalla
authors.forename: C
authors.initials: C
authors.lastname: Klessen
authors.forename: A
authors.initials: A
authors.lastname: Lembcke
authors.forename: V C
authors.initials: VC
authors.lastname: Romano
mesh_terms: D000328:Adult; D000368:Aged; D003287:Contrast Media; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007472:Iohexol / Q000031:analogs & derivatives; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000145:classification / Q000000981:diagnostic imaging*; D036542:Tomography, Spiral Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide