Organ Dose Evaluation For Multi-Slice Spiral CT Scans Based On Chinese Chest Anthropomorphic Phantom Measurements

Objective: To evaluate the clinical and research value of anthropomorphic chest phantom from CT sectional anatomy and tissue equivalence of X-ray attenuation by comparing with normal adults.Methods: Ten clinically healthy male volunteers, aged 20 to 50 years old, with an average height of 165 ~ 170 cm, and weight of 60 kg served as a control group. The GE Bright speed Elite 16-slice spiral CT scanner served as the choice for the study. The Chinese anthropomorphic chest phantom(CDP-1C) and the normal adults were scanned with the same scanning parameters, according to the Sectional image and the CT value of the various tissues and organs to evaluate the Similarity of Anatomy and the tissue equivalence of X-ray attenuation respectively.Results: On anatomic morphology, the Chinese anthropomorphic chest phantom was basically similar to the normal adult; on tissue equivalence of X-ray attenuation , no significant difference of CT value were shown between the lung,heart and spine of phantom and human(P >0.05). The maximum deviation on the liver was 4.49%. The CT value error of each tissue and organ was less than 5% between phantom and human, which is reaching the standard of experiment.Conclusion: The Chinese anthropomorphic chest phantom can be used to study of low-dose CT based on objective evaluation criteria.PART2 THE MEASUREMENT OF ORGANIC RADIATION DOSE WITH MULTI-SLICE CT BY USING THE CHINESE ANTHROPOMORPHIC CHEST PHANTOMObjective: Using the Chinese anthropomorphic chest phantom to measure absorbed dose of various tissues and organs under different noise index, calculation of the effective dose(ED) was used to evaluate the chest scanning with MSCT.Methods: To measure absorbed dose of various tissues and organs under different noise index by laying thermoluminescent dosimeters(TLD) inside the phantom, and the corresponding dose-length product(DLP) was recorded. Both of them were later converted into ED and comparative studies to analyze dose levels of chest CT scanning with automatic tube current modulation(ATCM) under different noise index.Statistical analysis is slected t test of single factor, using SPSS12.0 statistical software to analyze.Results: As the noise index increase from 8.5 to 22.5,The DLP decrease from 393.57mGy/cm to 78.75mGy/cm and the organs dose decline,for example,the average absorbed dose decrease from 22.38 mGy to 3.66mGy in lung. Compared with ED calculating by absorbed dose, The ED calculating by DLP was lower,and the ED are 6.69 mSv and 8.77 mSv respectly when the noise index is set 8.5.Conclusion: Application of the Chinese anthropomorphic chest phantom to carry out CT dose assessment is more accurate. The noise index should be set larger than 8.5 during the chest CT screening based on ATCM technique.