ABSTRACT
<p><b>BACKGROUND</b>Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography (CT) examination. This results from the concerns about radiation exposure from CT and the potential increase in the incidence of radiation induced carcinogenesis. This study aimed to investigate the lowest radiation dose for maintaining good image quality in adult chest scanning using GE CT equipment.</p><p><b>METHODS</b>Seventy-two adult patients were examined by Gemstone Spectral CT. They were randomly divided into six groups. We set up a different value of noise index (NI) when evaluating each group every other number from 13.0 to 23.0. The original images were acquired with a slice of 5 mm thickness. For each group, several image series were reconstructed using different levels of adaptive statistical iterative reconstruction (ASIR) (30%, 50%, and 70%). We got a total of 18 image sequences of different combinations of NI and ASIR percentage. On one hand, quantitative indicators, such as CT value and standard deviation (SD), were assessed at the region of interest. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The volume CT dose index (CTDI) and dose length product (DLP) were recorded. On the other hand, two radiologists with ≥ 5 years of experience blindly reviewed the subjective image quality using the standards we had previously set.</p><p><b>RESULTS</b>The different combinations of noise index and ASIR were assessed. There was no significant difference in CT values among the 18 image sequences. The SD value was reduced with the noise index's reduction or ASIR's increase. There was a trend towards gradually lower SNR and CNR with an NI increase. The CTDI and DLP were diminishing as the NI increased. The scores from subjective image quality evaluation were reduced in all groups as the ASIR increased.</p><p><b>CONCLUSIONS</b>Increasing NI can reduce radiation dose. With the premise of maintaining the same image quality, using a suitable percentage of ASIR can increase the value of NI. To assure image quality, we concluded that when the NI was set at 17.0 and ASIR was 50%, the image quality could be optimal for not only satisfying the requirements of clinical diagnosis, but also achieving the purpose of low-dose scanning.</p>
Subject(s)
Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Algorithms , Radiation Dosage , Radiography, Thoracic , Methods , Tomography, X-Ray Computed , MethodsABSTRACT
Objective To investigate the effects of repeated computed tomography (CT) scan on hematological and immunological index in mice,and to explore the related mechanism.Methods A total of 60 BALB/c mice were randomly divided into six groups as control,once,twice,4,6 and 8 times of CT scans,and administered with whole-body scan by 64-slice spiral CT with the pelvis scan mode.Thermoluminescence dosimeter was used to detect the absorbed doses of CT scan,while DNA damage (γ-H2AX),apoptosis,autophagy,cell cycle and percentages of CD4/CD8 in peripheral lymphocytes and bone marrow cells were analyzed by flow cytometry.γ-H2AX was detected 1 h after the last CT scan,and the other indexes were detected 24 h after the last CT scan.Results γ-H2AX increased after more than twice CT scans in peripheral lymphocytes and after than 4 times of CT scan in bone marrow cells (P ＜ 0.05).Apoptosis increased in peripheral blood lymphocytes and decreased in bone marrow cells after more than 4 times of CT scan (P ＜ 0.05),suggesting that lymphocytes were more sensitive while different cell subpopulation in bone marrow showed different sensitivity and response phase.No obvious changes of autophagy level were observed in peripheral blood lymphocytes,while autophagy increased in bone marrow cells after single CT scan (F =81.10,P ＜ 0.05).8 times of CT scan significantly increased the percentages of cells at G0/G1 phase and G2/M phase(x2 =11.29,28.57,P ＜0.05).The percentage of CD4 + T,CD8 + T cells decreased after CT scan,but no effects on the ratio of CD4 +/CD8 +.Conclusions Repeated CT scans could induce injury effects on hematopoietic system and immune system,and then the apoptosis.Apoptosis,autophagy and cell cycle arrest might be initiated to maintain genome stability but there is no influence on immune balance.
ABSTRACT
Objective To investigate the variation in the position of conus medullaris in Chinese adult population in order to avoid hitting conus during spinal puncture. Methods Eight hundred patients suffering from back pain, aged 18-91 yr, were enrolled in this study. The position of conus medullaris was determined using Siemens 1.5 T magnetic resonance imaging system. According to the method described by Reimann, the vertebral body was used as mark of reference to the level of the end of conus. Results There were 190 patients in whom the position of the end of conus medullaris was lower than L1,2 . The incidence of the position of the end of conus medullaris lower than L1,2 was higher in patients 30-60 or older than in those under 30, and in those over the age of 60 than in those 30-60 (P ＜ 0.05). Conclusion Spinal puncture should be performed cautiously at L2,3. CT or MRI is recommended before operation for the patients to locate the position of conus medullaris and avoid injury to the spinal cord.