title: Impact of radiation dose and iterative reconstruction on pulmonary nodule measurements at chest CT: a phantom study.
abstract: OBJECTIVE
  We aimed to identify the impact of radiation dose and iterative reconstruction (IR) on measurement of pulmonary nodules by chest computed tomography (CT).
  
  
  METHODS
  CT scans were performed on a chest phantom containing various nodules (diameters of 3, 5, 8, 10, and 12 mm; +100, -630 and -800 HU for each diameter) at 80, 100, 120 kVp and 10, 20, 50, 100 mAs (a total of 12 radiation dose settings). Each CT was reconstructed using filtered back projection, iDose4, and iterative model reconstruction (IMR). Thereafter, two radiologists measured the diameter and attenuation of the nodules. Noise, contrast-to-noise ratio and signal-to-noise ratio of CT images were also obtained. Influence of radiation dose and reconstruction algorithm on measurement error and objective image quality metrics was analyzed using generalized estimating equations.
  
  
  RESULTS
  The 80 kVp, 10 mAs CT scan was not feasible for the measurement of 3 mm sized simulated ground-glass nodule (GGN); otherwise, diameter measurement error was not significantly influenced by radiation dose (P > 0.05). IR did not have a significant impact on diameter measurement error for simulated solid nodules (P > 0.05). However, for simulated GGNs, IMR was associated with significantly decreased relative diameter measurement error (P < 0.001). Attenuation measurement error was not significantly influenced by either radiation dose or reconstruction algorithm (P > 0.05). Objective image quality was significantly better with IMR (P < 0.05).
  
  
  CONCLUSIONS
  Nodule measurements were not affected by radiation dose except for 3 mm simulated GGN on 80 kVp, 10 mAs dose setting. However, for GGNs, IMR may help reduce diameter measurement error while improving image quality.
authors.affiliation: Department of Radiology, College of Medicine, and Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Korea; Aerospace Medical Group, Air Force Education and Training Command, Jinju, Korea. cmpark@radiol.snu.ac.kr.
authors.forename: Hyungjin
authors.initials: H
authors.lastname: Kim
authors.forename: Chang Min
authors.initials: CM
authors.lastname: Park
authors.forename: Hee Dong
authors.initials: HD
authors.lastname: Chae
authors.forename: Sang Min
authors.initials: SM
authors.lastname: Lee
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Goo
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008962:Models, Theoretical; D055613:Multiple Pulmonary Nodules / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000009:adverse effects; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*