Impact of Patient Size and Radiation Dose on Accuracy and Precision of Iodine Quantification and Virtual Noncontrast Values in Dual-layer Detector CT—A Phantom Study

Steven Van Hedent*, Curtis Tatsuoka, Sarah Carr, Kai Roman Laukamp, Brendan Eck, Nils Große Hokamp, Rivka Kessner, Pablo Ros, David Jordan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Rationale and Objectives: Iodine quantification (IQ) and virtual noncontrast (VNC) images produced by dual-energy CT (DECT) can be used for various clinical applications. We investigate the performance of dual-layer DECT (DLDECT) in different phantom sizes and varying radiation doses and tube voltages, including a low-dose pediatric setting. Materials and Methods: Three phantom sizes (simulating a 10-year-old child, an average, and a large-sized adult) were scanned with iodine solution inserts with concentrations ranging 0-32 mg/ml, using the DLDECT. Each phantom size was scanned with CTDIvol 2-15 mGy at 120 and 140 kVp. The smallest phantom underwent additional scans with CTDIvol 0.9-1.8 mGy. All scans were repeated 3 times. Each iodine insert was analyzed using VNC and IQ images for accuracy and precision, by comparison to known values. Results: For scans from 2 to 15 mGy mean VNC attenuation and IQ error in the iodine inserts in the small, medium, and large phantoms was 1.2 HU ± 3.2, −1.2 HU ± 14.9, 2.6 HU ± 23.6; and +0.1 mg/cc ± 0.4, −0.9 mg/cc ± 0.9, and −1.8 mg/cc ± 1.8, respectively. In this dose range, there were no significant differences (p ≥ 0.05) in mean VNC attenuation or IQ accuracy in each phantom size, while IQ was significantly less precise in the small phantom at 2 mGy and 10 mGy (p < 0.05). Scans with CTDIvol 0.9-1.8 mGy in the small phantom showed a limited, but statistically significantly lower VNC attenuation precision and IQ accuracy (−0.5 HU ± 5.3 and −0.3 mg/cc ± 0.5, respectively) compared to higher dose scans in the same phantom size. Conclusion: Performance of iodine quantification and subtraction by VNC images in DLDECT is largely dose independent, with the primary factor being patient size. Low-dose pediatric scan protocols have a significant, but limited impact on IQ and VNC attenuation values.

Original languageEnglish
Pages (from-to)409-420
Number of pages12
JournalAcademic Radiology
Volume27
Issue number3
DOIs
StatePublished - Mar 2020
Externally publishedYes

Funding

FundersFunder number
University Hospitals Cleveland Medical Center
Case Western Reserve University
Philips Oral Healthcare

    Keywords

    • Dual-energy CT
    • Dual-layer detector
    • Lodine quantification
    • Material decomposition
    • Phantom study
    • Radiation dosage
    • Spectral detector computed tomography

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