title: Lesion detection performance: comparative analysis of low-dose CT data of the chest on two hybrid imaging systems.
abstract: Incidental findings on low-dose CT images obtained during hybrid imaging are an increasing phenomenon as CT technology advances. Understanding the diagnostic value of incidental findings along with the technical limitations is important when reporting image results and recommending follow-up, which may result in an additional radiation dose from further diagnostic imaging and an increase in patient anxiety. This study assessed lesions incidentally detected on CT images acquired for attenuation correction on two SPECT/CT systems.
  
  
  METHODS
  An anthropomorphic chest phantom containing simulated lesions of varying size and density was imaged on an Infinia Hawkeye 4 and a Symbia T6 using the low-dose CT settings applied for attenuation correction acquisitions in myocardial perfusion imaging. Twenty-two interpreters assessed 46 images from each SPECT/CT system (15 normal images and 31 abnormal images; 41 lesions). Data were evaluated using a jackknife alternative free-response receiver-operating-characteristic analysis (JAFROC).
  
  
  RESULTS
  JAFROC analysis showed a significant difference (P < 0.0001) in lesion detection, with the figures of merit being 0.599 (95% confidence interval, 0.568, 0.631) and 0.810 (95% confidence interval, 0.781, 0.839) for the Infinia Hawkeye 4 and Symbia T6, respectively. Lesion detection on the Infinia Hawkeye 4 was generally limited to larger, higher-density lesions. The Symbia T6 allowed improved detection rates for midsized lesions and some lower-density lesions. However, interpreters struggled to detect small (5 mm) lesions on both image sets, irrespective of density.
  
  
  CONCLUSIONS
  Lesion detection is more reliable on low-dose CT images from the Symbia T6 than from the Infinia Hawkeye 4. This phantom-based study gives an indication of potential lesion detection in the clinical context as shown by two commonly used SPECT/CT systems, which may assist the clinician in determining whether further diagnostic imaging is justified.
authors.affiliation: University of Salford, Manchester, United Kingdom Brighton and Sussex University Hospitals, NHS Trust, Brighton, United Kingdom maryam.jessop@bsuh.nhs.uk.
authors.forename: Maryam
authors.initials: M
authors.lastname: Jessop
authors.affiliation: University of Salford, Manchester, United Kingdom.
authors.forename: John D
authors.initials: JD
authors.lastname: Thompson
authors.affiliation: University of Salford, Manchester, United Kingdom.
authors.forename: Joanne
authors.initials: J
authors.lastname: Coward
authors.affiliation: Oslo and Akershus University College of Applied Sciences, Oslo, Norway.
authors.forename: Audun
authors.initials: A
authors.lastname: Sanderud
authors.affiliation: Haute École de Santé Vaud, HES-SO, Lausanne, Switzerland.
authors.forename: José
authors.initials: J
authors.lastname: Jorge
authors.affiliation: Hanze University of Applied Sciences, Groningen, The Netherlands; and.
authors.forename: Martijn
authors.initials: M
authors.lastname: de Groot
authors.affiliation: Escola Superior de Tecnologia da Saúde de Lisboa (ESTeSL), Lisbon, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Lança
authors.affiliation: University of Salford, Manchester, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Hogg
mesh_terms: D006801:Humans; D007091:Image Processing, Computer-Assisted; D033162:Incidental Findings; D055414:Myocardial Perfusion Imaging; D009369:Neoplasms / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging; D012372:ROC Curve; D011829:Radiation Dosage; D013902:Radiography, Thoracic; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed
keywords: CTAC; JAFROC; incidental findings; low-dose CT; observer performance