Preliminary study on radiation dose optimization for patients with head CT / 中华放射医学与防护杂志

ABSTRACT

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 circumferencesA 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.