Dataset Information

Automated tube voltage selection in pediatric non-contrast chest CT.

ABSTRACT:

Background

Modern CT scanners provide automatic dose adjustment systems, which are promising options for reducing radiation dose in pediatric CT scans. Their impact on patient dose, however, has not been investigated sufficiently thus far.

Objective

To evaluate automated tube voltage selection (ATVS) in combination with automated tube current modulation (ATCM) in non-contrast pediatric chest CT, with regard to the diagnostic image quality.

Materials and methods

There were 160 non-contrast pediatric chest CT scans (8.7±5.4 years) analyzed retrospectively without and with ATVS. Correlations of volume CT Dose Index (CTDIvol) and effective diameter, with and without ATVS, were compared using Fisher's z-transformation. Image quality was assessed by mean signal-difference-to-noise ratios (SDNR) in the aorta and in the left main bronchus using the independent samples t-test. Two pediatric radiologists and a general radiologist rated overall subjective Image quality. Readers' agreement was assessed using weighted kappa coefficients. A p value <0.05 was considered significant.

Results

CTDIvol correlation with the effective diameter was r = 0.62 without and r = 0.80 with ATVS (CI: -0.04 to -0.60; p = 0.025). Mean SDNR was 10.88 without and 10.03 with ATVS (p = 0.0089). Readers' agreement improved with ATVS (weighted kappa between pediatric radiologists from 0.1 (0.03-0.16) to 0.27 (0.09-0.45) with ATVS; between general and each pediatric radiologist from 0.1 (0.06-0.14) to 0.12 (0.05-0.20), and from 0.22 (0.11-0.34) to 0.36 (0.24-0.49)).

Conclusion

ATVS, combined with ATCM, results in a radiation dose reduction for pediatric non-contrast chest CT without a loss of diagnostic image quality and prevents errors in manual tube voltage setting, and thus protecting larger children against an unnecessarily high radiation exposure.

SUBMITTER: Hojreh A

PROVIDER: S-EPMC6169939 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Current methods for organ and effective dose estimations in pediatric CT are largely patient generic. Physical phantoms and computer models have only been developed for standard/limited patient sizes at discrete ages (e.g., 0, 1, 5, 10, 15 years old) and do not reflect the variability of patient anatomy and body habitus within the same size/age group. In this investigation, full-body computer models of seven pediatric patients in the same size/protocol group (weight: 11.9-18.2 kg) were created based on the patients' actual multi-detector array CT (MDCT) data. Organs and structures in the scan coverage were individually segmented. Other organs and structures were created by morphing existing adult models (developed from visible human data) to match the framework defined by the segmented organs, referencing the organ volume and anthropometry data in ICRP Publication 89. Organ and effective dose of these patients from a chest MDCT scan protocol (64 slice LightSpeed VCT scanner, 120 kVp, 70 or 75 mA, 0.4 s gantry rotation period, pitch of 1.375, 20 mm beam collimation, and small body scan field-of-view) was calculated using a Monte Carlo program previously developed and validated to simulate radiation transport in the same CT system. The seven patients had normalized effective dose of 3.7-5.3 mSv/100 mAs (coefficient of variation: 10.8%). Normalized lung dose and heart dose were 10.4-12.6 mGy/100 mAs and 11.2-13.3 mGy/100 mAs, respectively. Organ dose variations across the patients were generally small for large organs in the scan coverage (<7%), but large for small organs in the scan coverage (9%-18%) and for partially or indirectly exposed organs (11%-77%). Normalized effective dose correlated weakly with body weight (correlation coefficient: r=-0.80). Normalized lung dose and heart dose correlated strongly with mid-chest equivalent diameter (lung: r=-0.99, heart: r=-0.93); these strong correlation relationships can be used to estimate patient-specific organ dose for any other patient in the same size/protocol group who undergoes the chest scan. In summary, this work reported the first assessment of dose variations across pediatric CT patients in the same size/protocol group due to the variability of patient anatomy and body habitus and provided a previously unavailable method for patient-specific organ dose estimation, which will help in assessing patient risk and optimizing dose reduction strategies, including the development of scan protocols.