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OBJECTIVES: In the present study, we introduced a practical approach to quantify organ-specific radiation doses and investigated whether low-dose head circumference (HC)-based protocols for non-enhanced head computed tomography (CT) could reduce organs-specific radiation dose in pediatric patients while maintaining high image quality. METHODS: A total of 83 pediatric patients were prospectively recruited. Without limits to the HC, 15 patients were selected as a convention group (CON group) and underwent non-enhanced head CT scan with standard-dose protocols (tube current-time products of 250mAs). Low-dose group (LD group), including remaining 68 pediatrics were divided into 3 subgroups based on the HC: 54.1-57.0 cm for LD200mAs group (HC-based protocols of 200mAs), 51.1-54.0 cm for LD150mAs group (HC-based protocols of 150mAs), 48.1-51.0 cm for LD100mAs group (HC-based protocols of 100mAs). Subjective and objective image quality was evaluated and measured by 2 experienced radiologists. Radimetrics was used to calculate organs-specific radiation dose, including the brain, eye lenses, and salivary glands. RESULTS: In CON250mAs group, radiation doses in the brain and salivary glands were conversely correlated with HC, and pediatric patients with smaller HC received higher organs-specific radiation dose. Reducing tube current-time product from 250 to 100mAs could significantly reduce the organ-specific radiation dose. The subjective image quality score ≥ 3.0 is acceptable for diagnosis purposes. The signal to noise ratio (SNR) and the contrast to noise ratio (CNR) of bilateral thalamus and centrum semiovale in 3 LD subgroups were not statistically different compared with the CON group. CONCLUSION: Our research indicated that low-dose HC-based protocols of non-enhanced head CT scan can evidently reduce the organ-specific radiation doses, while maintaining high image quality. HC can serve as a vital tool to guide personalized low-dose head CT scan for pediatric patients.
RESUMO
Objective To investigate the effect of adjusting tube current time product (mAs) according to head circumference index on head CT image quality and organ-specific-dose level based on Monte Carlo analysis platform.Methods A total of 92 patients including children and adolescents with different clinical symptoms undergoing head CT scan were prospectively selected between September 2017 and June 2018 in the First Hospital of Jilin University.Without limiting the size of the head circumference,there were 22 patients were selected as conventional group by random number table,whose head circumference was 48.1-59.2 cm.Low dose group was divided into following three subgroups according to different head circumferences:A group 54.1-57.0 cm (n=22);B group 51.1-54.0 cm (n=26) and C group 48.1-51.0 cm (n=22).Tube current time product was 250 mAs for conventional group,200 mAs for A group,150 mAs for B group and 100 mAs for C group,respectively.The organ-specific-radiation doses (brain,eye lens and salivary gland) were recorded by Monte Carlo analysis platform and the subjective and objective image quality score was evaluated.Analyses of the differences between four groups were compared with image quality score as well as organ-specific-radiation dose by single factor variance.Results Radiation dose to brain was conventional group (34.37±3.62),A group (25.91±0.99),B group (23.18±6.11) and C group (17.38 ± 3.23) mSv,respectively.The difference was of statistical significance in the four groups (F=54.51,P＜0.05).Dose to eye lens was conventional group (41.54± 1.04),A group (33.03±0.35),B group (26.18±2.72) and C group (20.88±4.45) mSv,with statistical significance in difference between the four groups (F=189.75,P＜0.05).Dose to salivary gland was conventional group (35.04 ± 4.94),A group (25.92 ± 0.99),B group (22.93 ± 6.54) and C (14.96±2.67) mSv,respectively,with statistical significance in difference between the four groups (F=65.74,P＜0.05).Image quality scores were respectively conventional group (4.97±0.13),A group (4.77 ± 0.49),B group (4.60 ± 0.49) and C group (3.98 ± 0.61),respectively,with statistical significance between them (F=3.89,P＜0.05),but without statistical significance in difference between the four groups (P ＞ 0.05).The signal-to-noise ratios of gray matter in A,B and C groups were conventional group (18.69 ± 3.55),A group (16.76 ± 2.87),B group (15.05 ± 2.80) and C group (13.65±2.53),respectively,without statistical significance in difference between the four groups (P＞ 0.05);The signal-to-noise ratios of white matter in conventional group (17.46±3.72),A group (15.54± 2.81),B group (13.71±2.43) and C group (11.77±2.18),respectively,without statistical significance in difference between the four groups (P＞0.05).Conclusions Adjusting the tube current time product (mAs) according to head circumference index of children and adolescents can make scanning program more personalized and reduce organ-specific-radiation doses to sensitive organs without compromise of image quality.
