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Radiation dose reduction based on CNR index with low-tube voltage scan for pediatric CT scan: experimental study
Takanori Masuda1, Yoshinori Funama2, Masao Kiguchi3
1Department of Radiological Technology, Tsuchiya General Hospital, Nakajima-cho 3-30, Naka-ku, Hiroshima, 730-8655 Japan ; Department of Diagnostic Radiology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
Insights
Lowering tube voltage in pediatric CT scans can reduce radiation dose while maintaining image quality. This study found that contrast-to-noise ratio (CNR) is a key index for achieving dose reduction in pediatric CT examinations.
Area of Science:
- Medical Imaging
- Radiology
- Pediatric Imaging
Background:
- Investigating the relationship between image noise and contrast-to-noise ratio (CNR) at various tube voltages.
- Assessing the feasibility of radiation dose reduction in pediatric CT using CNR.
- Utilizing anthropomorphic newborn and 1-year-old phantoms for the study.
Purpose of the Study:
- To determine the correlation between image noise and CNR across different tube voltages.
- To evaluate the potential for radiation dose reduction in pediatric CT examinations.
- To establish CNR as a reliable index for optimizing CT parameters.
Main Methods:
- Performed helical CT scans on anthropomorphic newborn and 1-year-old phantoms.
- Measured CT numbers of simulated aorta and image noise in the mediastinum.
- Calculated CNR on 80, 100, and 120-kVp images reconstructed with filtered back projection (FBP) and iterative reconstruction (IR).
- Measured radiation dose using radio-photoluminescence glass dosimeters at a CNR of 14.
Main Results:
- CT numbers increased with decreasing tube voltage (80-120 kVp).
- Radiation dose reduction was observed at lower tube voltages (e.g., 56% reduction at 80 kVp for FBP with newborn phantom).
- Established a clear relationship between image noise and CNR at different tube voltages.
Conclusions:
- Utilizing CNR as an index at lower tube voltages can facilitate further radiation dose reduction in pediatric CT.
- Optimizing tube voltage based on CNR is crucial for balancing image quality and radiation safety in pediatric patients.
- The findings support the use of lower kVp settings in pediatric CT when CNR is maintained.
Background:
To figure out the relationship between image noise and contrast noise ratio (CNR) at different tube voltages, using anthropomorphic new-born and 1-year-old phantoms, and to discuss the feasibility of radiation dose reduction, based on the obtained CNR index from image noise. We performed helical scans of the anthropomorphic new-born and 1-year-old phantoms. The CT numbers of the simulated aorta and image noise of the simulated mediastinum were measured; then CNR was calculated on 80, 100, and 120-kVp images reconstructed with filtered back projection (FBP) and iterative reconstruction (IR). We also measured the center and surface dose in the case of CNR of 14 using radio-photoluminescence glass dosimeters.
Results:
The CT number of the simulated aorta was increased with decreasing tube voltage from 120 to 80 kVp (362.5-535.1 HU for the new-born, 358.9-532.6 HU for the 1-year-old). At CNR of 14, the center dose was 0.4, 0.6 and 0.9 mGy at FBP and 0.5, 0.6 and 0.9 mGy at IR and with the new-born phantom acquired at 80, 100 and 120 kVp, respectively. The center dose for FBP image was reduced by 56% at 80 kVp, 34% at 100 kVp for the new-born and 36% at 80 kVp, 22% at 100 kVp for the 1-year-old compared with that at 120 kVp. We obtained a relationship between image noise and CNR at different tube voltages using the anthropomorphic new-born and 1-year-old phantoms.
Conclusion:
The use of index of CNR with low-tube voltage may achieve further radiation dose reduction in pediatric CT examination.
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