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OBJECTIVE: To assess the lesion conspicuity and image quality in CT evaluation of small (< or = 3 cm) hepatocellular carcinomas (HCCs) using automatic tube voltage selection (ATVS) and automatic tube current modulation (ATCM) with or without iterative reconstruction. MATERIALS AND METHODS: One hundred and five patients with 123 HCC lesions were included. Fifty-seven patients were scanned using both ATVS and ATCM and images were reconstructed using either filtered back-projection (FBP) (group A1) or sinogram-affirmed iterative reconstruction (SAFIRE) (group A2). Forty-eight patients were imaged using only ATCM, with a fixed tube potential of 120 kVp and FBP reconstruction (group B). Quantitative parameters (image noise in Hounsfield unit and contrast-to-noise ratio of the aorta, the liver, and the hepatic tumors) and qualitative visual parameters (image noise, overall image quality, and lesion conspicuity as graded on a 5-point scale) were compared among the groups. RESULTS: Group A2 scanned with the automatically chosen 80 kVp and 100 kVp tube voltages ranked the best in lesion conspicuity and subjective and objective image quality (p values ranging from < 0.001 to 0.004) among the three groups, except for overall image quality between group A2 and group B (p = 0.022). Group A1 showed higher image noise (p = 0.005) but similar lesion conspicuity and overall image quality as compared with group B. The radiation dose in group A was 19% lower than that in group B (p = 0.022). CONCLUSION: CT scanning with combined use of ATVS and ATCM and image reconstruction with SAFIRE algorithm provides higher lesion conspicuity and better image quality for evaluating small hepatic HCCs with radiation dose reduction.
Subject(s)
Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Young Adult , Algorithms , Carcinoma, Hepatocellular/diagnostic imaging , Contrast Media , Fluoroscopy , Image Enhancement/methods , Liver Neoplasms/diagnostic imaging , Prospective Studies , Radiation Dosage , Radiographic Image Interpretation, Computer-Assisted/methods , Tomography, X-Ray Computed/methodsABSTRACT
Objective To explore the feasibility and application value of low dose CT with automatic tube current modulation (ATCM) in the diagnosis of pneumoconiosis.Methods Forty-five patients with pneumoconiosis confirmed by the occupational agency underwent standard dose CT scanning with a fixed tube current of 150 mA and low dose CT scanning with ATCM (50-200 mA) with noise index (NI) of 14.The CT dose index volume (CTDIvol) and dose length product (DLP) under the different scanning condition were recorded.The image quality,specific image manifestations of pneumoconiosis (shadow size,shadow concentration,pneumoconiosis stages) were reviewed in double-blind methods by two radiologists,and the statistical analysis was performed.Results CT characteristics of pneumoconiosis could be detected efficiently with low dose CT scanning with ATCM.There were no significant differences in showing the shadow size,shadow concentration,pneumoconiosis stages and the image quality between the two groups (P＞0.05).The CTDIvol and DLP of standard dose CT scanning were 13.53 mGy and (337.13 ± 13.53) mGy/cm respectively,and CTDIvol and DLP of low dose CT scanning with ATCM were (7.39 ± 0.45) mGy and (188.78 ± 1.80) mGy/cm,there were statistical differences (P ＜ 0.05).Conclusions Low dose CT scanning with ATCM can reflect the characteristics of pneumoconiosis,and it also can significantly reduce the radiation dose with diagnostic acceptability of the image quality.So low dose CT scanning with ATCM can replace the standard dose CT scan in diagnosing and screening of the pneumoconiosis.
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Objective To assess the effectiveness of Z-axis automatic tube current modulation ( ATCM) technique with respect to dose reduction and image noise in the thyroid regional tissues during neck computed tomography angiography (CTA). Methods A total of 140 patients underwent neck CTA with 64-slice spiral CT, and were randomized into fixed-tube current group and ATCM group. Objective noise, CTDIw, DLP and mA of each group were recorded. Results The image qualities of all the patients were diagnostically acceptable, though the objective noise of neck in the ATCM group was higher than that in the group of fixed-tube current (P＜ 0.05 ). The radiation doses in the ATCM group [ CTDIw (35.99±1.31 ) mGy, DLP (11 121.39 ±5.51) mGy·cm] were significantly inferior to those in the group of fixed tube current [ CTDIw (43.22±1.42) mGy, DLP (1514.45±5.56) mGy·cm]. Conclusions Compared with fixedtube current technique, ATCM technique could significantly reduce the radiation dose in neck CT with diagnostic acceptability of the image quality.
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OBJECTIVE: To evaluate a quantitative method for individually adjusting the tube current to obtain images with consistent noise in electrocardiogram (ECG)-gated CT cardiac scans. MATERIALS AND METHODS: The image noise from timing bolus and cardiac CT scans of 80 patients (Group A) who underwent a 64-row multidetector (MD) CT cardiac examination with patient-independent scan parameters were analyzed. A formula was established using the noise correlation between the timing bolus and cardiac scans. This formula was used to predict the required tube current to obtain the desired cardiac CT image noise based on the timing bolus noise measurement. Subsequently, 80 additional cardiac patients (Group B) were scanned with individually adjusted tube currents using an established formula to evaluate its ability to obtain accurate and consistent image noise across the patient population. Image quality was evaluated using score scale of 1 to 5 with a score of 3 or higher being clinically acceptable. RESULTS: Using the formula, we obtained an average CT image noise of 28.55 Hounsfield unit (HU), with a standard deviation of only 1.7 HU, as opposed to a target value of 28 HU. Image quality scores were 4.03 and 4.27 for images in Groups A and B, respectively, and there was no statistical difference between the image quality scores between the two groups. However, the average CT dose index (CTDIvol) was 30% lower for Group B. CONCLUSION: Adjusting the tube current based on timing bolus scans may provide a consistent image quality and dose optimization for cardiac patients of various body mass index values.
Subject(s)
Female , Humans , Male , Middle Aged , Heart Diseases/diagnostic imaging , Mathematics , Radiation Dosage , Radiographic Image Interpretation, Computer-Assisted , Retrospective Studies , Tomography, X-Ray Computed/instrumentationABSTRACT
0.05),an effective mA seconds in the experimental group(296.74?19.15)mAs,than in the control group 350 mAs was reduced about 15.4%(P
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Objective To study the effect of image quality and radiation dose by using Z -axis automatic tube current modulation(ATCM),as well as the application of automatic tube current modulation technology.Methods A control group consisting of 25 patients underwent cervical MDCT with fixed-current technique(100-220mA).Of two study groups of 25 patients,one underwent cervical MDCT using z-axis ATCM with the noise index of NI10 and tube current intensity of 80-480 mA,and the other with the noise index of NI12.5 and tube current intensity of 80-369 mA.The noise and mean tube current-time products(mAs) were recorded.Two radiologists evaluated images for diagnostic acceptability.Results All CT examinations of study and control groups were diagnostically acceptable,though objective noise was different with z-axis ATCM than with fixed current.ATCM resulted in significant radiation dose reduction(NI10,94.8?17.9 mAs;NI12.5,74.8? 18.3 mAs),when compared with the fixed current(130.4?43.1 mAs).Conclusion Z-axis Automatic mA technique has no significant change in image quality when compared with the fixed mA technique,but the radiation dose is decreased by 27%(NI10) and 43%(NI12.5),for MDCT evaluation of neck.NI has to be selected on the basis of the tissue,lesion size and nature.