title: A multi-reader in vitro study using porcine kidneys to determine the impact of integrated circuit detectors and iterative reconstruction on the detection accuracy, size measurement, and radiation dose for small (<4 mm) renal stones.
abstract: Background Detection of small renal calculi has benefitted from recent advances in computed tomography (CT) scanner design. Information regarding observer performance when using state-of-the-art CT scanners for this application is needed. Purpose To assess observer performance and the impact of radiation dose for detection and size measurement of <4 mm renal stones using CT with integrated circuit detectors and iterative reconstruction. Material and Methods Twenty-nine <4 mm calcium oxalate stones were randomly placed in 20 porcine kidneys in an anthropomorphic phantom. Four radiologists used a workstation to record each calculus detection and size. JAFROC Figure of Merit (FOM), sensitivity, false positive detections, and calculus size were calculated. Results Mean calculus size was 2.2 ± 0.7 mm. The CTDIvolvalues corresponding to the automatic exposure control settings of 160, 80, 40, 25, and 10 Quality Reference mAs (QRM) were 15.2, 7.9, 4.2, 2.7, and 1.3 mGy, respectively. JAFROC FOM was ≥ 0.97 at ≥ 80 QRM, ≥ 0.89 at ≥ 25 QRM, and was inferior to routine dose (160 QRM) at 10 QRM (0.72, P < 0.05). Per-calculus sensitivity remained ≥ 85% for every reader at ≥ 25 QRM. Mean total false positive detections per reader were ≤ 3 at ≥ 80 QRM, but increased substantially for two readers ( ≥ 12) at ≤ 40 QRM. Measured calculus size significantly decreased at ≤ 25 QRM ( P ≤ 0.01). Conclusion Using low dose renal CT with iterative reconstruction and ≥ 25 QRM results in high sensitivity, but false positive detections increase for some readers at very low dose levels (≤ 40 QRM). At very low doses with iterative reconstruction, measured calculus size will artifactually decrease.
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Wells
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Adam T
authors.initials: AT
authors.lastname: Froemming
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Akira
authors.initials: A
authors.lastname: Kawashima
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Terri J
authors.initials: TJ
authors.lastname: Vrtiska
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Bohyun
authors.initials: B
authors.lastname: Kim
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Hartman
authors.affiliation: 2 Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Holmes
authors.affiliation: 3 Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA.
authors.forename: Rickey E
authors.initials: RE
authors.lastname: Carter
authors.affiliation: 3 Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Bartley
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Shuai
authors.initials: S
authors.lastname: Leng
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: McCollough
authors.affiliation: 1 Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Joel G
authors.initials: JG
authors.lastname: Fletcher
mesh_terms: D000818:Animals; D005189:False Positive Reactions; D066298:In Vitro Techniques; D007669:Kidney Calculi / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Nephrolithiasis; calculi; computed tomography (CT); detection; radiography; tomography