Image quality evaluation for CARE kV technique combined with iterative reconstruction for chest computed tomography scanning

Optimizing image quality and minimizing radiation dose in pediatric abdominal multiphase contrast-enhanced computed tomography: a study on CARE kV and CARE Dose 4D

Background

Multiphase contrast-enhanced computed tomography (CECT) is a commonly used modality in pediatric computed tomography (CT) scans. However, the purposes and focus of each phase, such as CT angiography (CTA), and parenchymal phase, are different. In routine practice, the same scanning parameters are used for all phases, resulting in unnecessary radiation exposure for children. Accurately and rapidly adjusting the scanning parameters for each phase of CECT is challenging in clinical settings. This retrospective cross-sectional study was designed to investigate the feasibility of using both CARE kV and CARE Dose 4D to reduce the radiation dose while maintaining diagnostic quality in multiphase CECT scans of children.

Methods

Overall, 57 children (33 males and 24 females) who underwent multiphase abdominal CECT in Xinjiang Hospital of Beijing Children's Hospital with an average age of 6.52±4.30 years (range, 0.1-15 years), were enrolled. The tube voltage was automatically modulated using CARE kV. The tube current was automatically modulated using CARE Dose 4D. Different dose saving optimization indices (DI) were used for the three phases: a DI value of 3 was used for the unenhanced CT phase, a DI value of 12 was used for the CTA phase, and a DI value of 7 was used for the parenchymal phase. The tube voltage and volume CT dose index (CTDIvol) were recorded for each phase. Two reviewers subjectively evaluated the overall image quality and noise level of the three phases using a 5-point Likert scale (1-2 points: unqualified, 3 points: qualified, 4 points: better, 5 points: best). The CT and noise values of the descending aorta, liver, and back muscle were measured objectively. The voltage distribution and the image quality and CTDIvol in each phase were compared.

Results

The most selected tube voltage in the unenhanced CT, CTA, and parenchymal phases was 100 kV (49/57, 85.96%), 70 kV (36/57, 63.16%), and 80 kV (32/57, 56.14%), respectively. The differences between the three phases were statistically significant (P<0.001). The CTDIvol values of the three phases were 3.99±1.99, 2.02±1.71, and 3.18±2.10 mGy, respectively, with a significant difference between the three phases (P<0.001). The CTDIvol decreased linearly as the DI value increased. All images met the diagnostic requirements. The overall quality scores for the three phases were 4.24±0.42, 4.41±0.49, and 4.50±0.45, respectively, with no significant linear relationship with the change in the DI.

Conclusions

The combined use of CARE Dose 4D and CARE kV could effectively reduce the radiation dose in children during multiphase abdominal CECT without compromising the diagnostic image quality.

Benefits and considerations in using a novel computed tomography system optimized for radiotherapy planning

In this study, we evaluated a novel 16-bit computed tomography (CT) system optimized for radiotherapy planning. Over six months, using various protocols, we conducted 616 scans, with an average of four CT series per session imported into our treatment planning software (TPS). The direct density (DD) reconstruction enabled a single CT number calibration curve for multiple tube voltages. Metal artifacts could be effectively reduced. The 16-bit character permitted dose calculation in high-density regions, while TPS integration challenges remained. In conclusion, our findings emphasize the system's potential benefits and considerations in radiotherapy workflows.

Validation of CARE kV automated tube voltage selection for PET-CT: PET quantification and CT radiation dose reduction in phantoms

Background

Applied tube voltage (kilovolts, kV) and tube current (milliampere seconds, mAs) affect CT radiation dose and image quality and should be optimised for the individual patient. CARE kV determines the kV and mAs providing the lowest dose to the patient, whilst maintaining user-defined reference image quality. Given that kV changes affect CT values which are used to obtain attenuation maps, the aim was to evaluate the effect of kV changes on PET quantification and CT radiation dose using phantoms.

Method

Four phantoms (‘Lungman’, ‘Lungman plus fat’, ‘Esser’ and ‘NEMA image quality’ (NEMA IQ)) containing F-18 sources underwent 1 PET and 5 CT scans, with CARE kV on (automatic kV selection and mAs modulation) and in semi mode with specified tube voltages of 140, 120, 100 and 80 kV (mAs modulation only). A CARE kV image quality reference of 120 kV/50 mAs was used. Impact on PET quantification was determined by comparing measured activity concentrations for PET reconstructions from different CT scans with the reconstruction using the 120 kV reference, and dose (DLP, CTDI_vol) differences calculated by comparing doses from all kV settings with the 120 kV reference.

Results

CARE kV-determined optimal tube voltage and CARE kV ‘on’ dose (DLP) savings compared with the 120 kV reference were: Lungman, 100 kV, 2.0%; Lungman plus fat, 120 kV, 0%; Esser, 100 kV, 9.3%; NEMA IQ, 100 kV, 3.4%. Using tube voltages in CARE kV ‘semi’ mode which were not advised by CARE kV ‘on’ resulted in dose increases ≤ 65% compared with the 120 kV reference (greatest difference Lungman plus fat, 80 kV). Clinically insignificant differences in PET activity quantification of up to 0.7% (Lungman, 100 kV, mean measured activity concentration) were observed when using the optimal tube voltage advised by CARE kV. Differences in PET quantification of up to 4.0% (Lungman, 140 kV, maximum measured activity concentration) were found over the full selection of tube voltages in semi mode, with the greatest differences seen at the most suboptimal kV for each phantom. However, most differences were within 1%.

Conclusions

CARE kV on can provide CT radiation dose savings without concern over changes in PET quantification.

Trends in radiation dose and image quality for pediatric patients with a multidetector CT and a third-generation dual-source dual-energy CT

AIM

To provide an overview on dose reduction and image quality after the installation of a third-generation dual-source CT (dsCT) in a Pediatric Radiology Department.

MATERIALS AND METHODS

We included pediatric patients (< 20 years old) undergoing CT for oncological staging (neck, chest and abdomen) or low-dose chest CT for lung diseases. Each of these two groups were further divided in two age groups (≤ or > 10 years old) including patients scanned in the same period of two consecutive years, in 2017 with a 16-row LightSpeed CT (GE Healthcare) or in 2018 with a Somatom Force dsCT (Siemens Healthineers). Technical parameters such as kVp, mAs, slice thickness, exposure times and dose indicators were retrieved and compared. Image quality was evaluated in consensus by two radiologists on a five-point semiquantitative scale. Nonparametric tests were used.

RESULTS

In oncological patients, significantly lower kVp and tube current with better image quality were achieved with the dsCT. Radiation dose (total DLP) was 5-6 times lower with dsCT, thanks also to virtual non-contrast images. In low-dose chest CT, the frequent use of tin filter required higher tube current; a total DLP 3 times lower was achieved with dsCT in patients ≤ 10 years old. The image quality was better with the dsCT in low-dose chest CT protocols.

CONCLUSION

The third-generation dsCT provides high-quality images with reduced motion artifacts at lower dose.