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@#<b>Objective</b> To investigate dose parameters in computed tomography (CT) scanning of common body parts inall public medical institutions in Shanghai, China, and analyze the dose distribution of CT scanning among adult subjects in Shanghai, and to provide a basis for establishing the diagnostic reference levels of CT scanning in Shanghai. <b>Methods</b> We selected at least one medical institution with CT services each from all 16 districts of Shanghai. In each medical institution, a piece of CT equipment with qualified annual inspection was sampled to investigate the doses to subjects in head, chest, abdomen, and lumbar spine scanning. We collected the basic information of the subjects, CT scanning parameters, volumetric CT dose index (CTDI<sub>vol</sub>), and dose length product (DLP). <b>Results</b> The scanning data of 1475 subjects were obtained. The 75th percentiles of the CTDI<sub>vol</sub> of the head, chest, abdomen, and lumbar spine were 57 mGy, 11 mGy, 16 mGy, and 23 mGy, respectively. The 75th percentiles of the DLP were 862 mGy·cm, 361 mGy·cm, 593 mGy·cm, and 550 mGy·cm, respectively. <b>Conclusion</b> CTDI<sub>vol</sub> and DLP differed significantly at different body parts, and also differed greatly at the same body parts. The DLP of men was slightly higher than that of women.
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@#Introduction: Reducing radiation dose for CT examinations has been accompanied by an increase in image noise. Studies have highlighted the application of a higher matrix size for improving image quality when assessing the lungs. This study aims to evaluate the influence of a low kVp and higher matrix size on radiation dose and image quality for abdominopelvic CT. Methods: This experiment was done on a 32 cm body phantom and scanned using a 128 slice CT scanner. The study utilised various combinations of kVp settings (140, 120, 100, 80 & 70) and matrix sizes (1024, 768 & 512). The image obtained was analysed objectively and subjectively. For objective analysis, we calculated SNR, and CNR. For subjective analysis, two radiologists evaluated the image in a 3-point scoring scale. Results: The study reported an increase in SNR (0.8%) and CNR (46%) at 120 kVp when increasing the matrix size from 512 x 512 to 768 x 768. Similarly, there was an increase of 14.5 % and 56.4 % in CNR and SNR using 1024 matrix size. The DLP was reduced by 4.5%, 50% and 70.6 % using 100, 80 and 70 kVp respectively. However, there was no change in DLP with higher matrix sizes. Conclusion: The study reported a combination of 100 kVp and 768 matrix size resulted in an almost similar (↓0.9 %) SNR and improved CNR (↑46.4 %) compared to 120 kVp and 512 matrix size. Qualitative analysis also showed a similar image quality with decreased radiation dose for abdominopelvic CT.
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BACKGROUND: Computed Tomography plays a priceless role for diagnostic and therapeutic purpose; however,applying an optimized Computed Tomography Technique to produce qualified image while delivering minimum radiation dose to patients is the common challenge. The main objective of this study was to establish local diagnostic reference levels for adult patients who visited abdominopelvic Computed Tomography examination. METHODS: A total of 158 patients who had taken abdominopelvic Computed Tomography examination from three selectedAmhara region hospitals were investigated. Both prospective and retrospective techniques of data collection were used while collecting the data in the entire sample. Two GE - Optima Computed Tomography 540 (16 slices) and one Phillips Brilliance (64slices), were employed during data collections. Data for patient demographics scan protocols, Computed Tomography dose descriptors and machine specifications were collected and analyzed by using SPSS software version 26. RESULTS: The third quartile estimated computed tomography dose index volume and dose length product, which is the local Diagnostic Reference Levels, were 12 mGy and 1904 cm.mGy respectively. The investigated local Diagnostic Reference Levels of Computed Tomography Dose index volume (mGy) was comparable to other international Diagnostic Reference Levels. However, the third quartile value of dose length product (cm.mGy) was higher than other reported international Diagnostic Reference Levels. CONCLUSION: The values of local Diagnostic Reference Levels presented in this work can be used as a baseline upon which future dose measurements can be compared in Amhara region
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Humans , Patients , Four-Dimensional Computed Tomography , Tomography , Dosage , Patient Outcome AssessmentABSTRACT
Objective To investigate the CT scanning parameters in hospitals at different levels in 15 provinces and cities in China and the doses to patients undergoing CT examination,in order to provide the basis for establishing CT diagnostic reference level suitable for our country.Methods As required in the implementation program for Technical Study on Medical Radiation Hazard Assessment and Control,the information on the patients examined and the CT scanning parameters in clinical practices were investigated.The CT dose index (CTDI100,CTDIW,CTDIVOL) of CT scanner was measured by using the CT ionization chamber.The dose length product (DLP) was calculated on the basis of the scan length of the patients examined.Results A total of 6 524 CT scanning procedures and 483 different types of CT scanning equipment were surveyed in 166 hospitals in 15 provinces in China.For head,chest,abdomen,and lumbar vertebrae,the average weighted CTDIW were 43,15,19 and 25 mGy,respectively,and the third quartile of CTDIw were 50,19,23 and 32 mGy,respectively.The average DLP were 540,397,503 and 376 mGy· cm,respectively.The third quartile of DLP were 659,525,632 and 479 mGy· cm respectively.Conclusions Through this survey,the doses to CT-examined patients in some provinces were basicly ascertained.The third quartile of doses to four body parts of the examined patients are different from the diagnostic reference level given in publications in other countries and regions.It is important to establish the CT diagnostic reference level suitable for our CT-examined patients according to Chinese national physical characteristics and therefor to promote the optimization of medical radiation protection in CT examination.
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Background: The role of Computed Tomography (CT) in the medical diagnosis of diseases has greatly expanded, despite the potential risk of cancer following exposures to ionising radiation (X-Ray) from this modality. This risk is particularly of great concern in children, who are more radiosensitive and have many years to manifest radiation effect than adults. Aims: To estimate risk of cancer induction from Pediatric cranial CT. Materials and Methods: A total of 203 patients, who were referred from various pediatric clinics and wards for cranial CT in a teaching hospital in the South Western Nigeria between the year 2011 and 2013 were considered. All patients were grouped into four age (year) groups: less than 1, 1-5, 5-10 and 10-15. A mathematical method was used to estimate the risk of cancer from the effective dose(ED) calculated from volume computed tomography dose index (CTDIvol), dose length product (DLP) and standard conversion factor. Results: The range of CTDIvol (mGy) received by all patients was 10–250 mGy while majority of the patients received 50–100. The range of DLP (mGy.cm) received by all patients and majority of patients was 500–5000 and 2001–2500 respectively. The range of ED (mSv) received by all patients and majority of the patients was 1–25 and 5–10 respectively. The risk estimated with respect to patients’ age showed that patient in the age group 1–5 years have the highest risk of cancer induction while the risk based on gender showed no significant difference. Conclusion: Over 60% of pediatric patients received more than the recommended values of CTDIvol, DLP and ED from cranial CT. Urgent steps must be taken to ensure compliant with international recommended precautions for dose reduction in pediatric medical imaging.
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Objective To evaluate the patient dose from Hi-ART MV helical CT imaging in image-guided radiotherapy.Methods Weighted CT dose index (CTDI_W) was measured with PTW TM30009 CT ion chamber in head and body phantoms,respectively,for slice thicknesses of 2,4,6 mm with scanned range of 5 cm and 15 cm.Dose length products (DLP) were subsequently calculated.The CTDI_W and DLP were compared with XVI kV CBCT and ACQSim simulator CT for routine clinical protocols.Results An inverse relationship between CTDI and the slice thickness was found.The dose distribution was inhomogeneous owing to the attenuation of the couch.CTDI and DLP had close relationship with the slice thickness and the scanned range.Patient dose from MVCT was lower than XVI CBCT for head,but larger for body scan.Results CTDI_W can be used to assess the patient dose in MV helical CT due to its simplicity for measurement and reproducibility.Regular measurement should be performed in QA & QC program.Appropriate slice thickness and scan range should be chosen to reduce the patient dose.
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Objective To evaluate the variations of effective doges with the preset scanning parameters from linac-integrated kV cone beam CT( CBCT). Methods Weighted CT dose index(CTDIW) were measured with PTW TM30009 CT ion chamber in head phantom and body phantom, respectively, for different combinations of tube voltage, mAs, collimator and gantry rotation range. Dose length products(DLP) were derived from CTDIW and effective doses(E) were calculated by the DLP and EDLP. Results CTDIW and effective dose had the quadratical relationship with tube voltage, depending linearly on product of tube current and exposure time. Effective dose had close relationship with the collimator and the gantry rotation range. Both the DLP and ED for CBCT were lower than the reference dose level recommended for conventional CT. Conclusions Effective dose from CBCT has a close relationship with the scanning parameters. Optimal imaging parameters should be chosen according to the patient's anatomy to reduce patient dose.
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easurement should be performed in QA & QC program. Optimal image parameters should be chosen to reduce the scanning range and patient dose.