Tube Voltage Levels Research Articles

Evaluation of a Tube Voltage-Tailored Contrast Medium Injection Protocol for Coronary CT Angiography: Results From the Prospective VOLCANIC Study.

OBJECTIVE. The purpose of this study was to prospectively evaluate, using software support, the feasibility and the quantitative and qualitative image quality parameters of a tube voltage-tailored contrast medium (CM) application protocol for patient-specific injection during coronary CT angiography (CCTA). SUBJECTS AND METHODS. In the Voltage-Based Contrast Media Adaptation in Coronary Computed Tomography Angiography (VOLCANIC-CTA) study, a single-center trial, 120 patients referred for CCTA were prospectively assigned to a tube voltage-tailored CM injection protocol. Automated tube voltage levels were selected in 10-kV intervals and ranged from 70 to 130 kV, and the iodine delivery rate (IDR) was adapted to the tube voltage level using dedicated software. The administered CM volume (370 mg I/mL) ranged from 33 mL at 70 kV (IDR, 0.7 g I/s) to 65 mL at 130 kV (IDR, 1.7 g I/s). Attenuation was measured in the aorta and coronary arteries to calculate quantitative signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), and 5-point scales were used to evaluate overall image quality. Radiation metrics were also assessed and compared among the protocols. RESULTS. The mean age of the study patients was 62.5 ± 11.9 (SD) years. Image quality was rated as diagnostic in all patients. Contrast attenuation peaked at 70 kV (p < 0.001), whereas SNR and CNR parameters showed no significant differences between tube voltage levels (p ≥ 0.085). Additionally, no significant differences in subjective image quality parameters were found among the different protocols (p ≥ 0.139). The lowest radiation dose values were observed in the group assigned to the 70-kV protocol, which had a median radiation effective dose of 2.0 mSv (p < 0.001). CONCLUSION. The proposed tube voltage-tailored injection protocol allows individualized scanning of patients undergoing CCTA and significantly reduces CM and radiation dose while maintaining a high diagnostic image quality.

Detection and Diagnosis of Defect in GIS Based on X-ray Digital Imaging Technology

For better application of X-ray digital imaging technology in defect detection in Gas Insulated Switchgear (GIS), it is essential to investigate the typical defect and establish the defect database, which has not been adequately performed in previous work. Systematic experimental research is also needed to accumulate data and experience. In this research, an experimental platform, including Computed Radiography (CR) imaging system and a GIS model, is built, and extensive tests of different kinds of typical defects are studied. The influence X-ray irradiation on SF6 under different tube voltage levels is firstly examined, which proves that the withstand voltage of SF6 gas has not been affected and no dissociation has been found. Then, several kinds of defects are tested by X-ray digital imaging technology. The successful application examples of “visual” detection of defects further prove the practicability and validity of the X-ray digital imaging technique. Finally, the image database of typical defects inside of GIS is established and the defect risk is also analyzed in three levels, which would be useful for the defect severity diagnosis and risk assessment.

Channelized Hotelling observer assessing microcalcification detectability on 2D mammography: a first application to study the impact of tube voltage

This work was aimed to assess the detectability of microcalcifications as a function of tube voltage in 2D mammography using an in-house developed Channelized Hotelling Observer (CHO). The images of a 3D structured phantom, containing acrylic beads of different diameters in water and inserted signals (microcalcifications, spiculated and non-spiculated mass models) were assessed. Images had been acquired on a Siemens Mammomat Inspiration system at 5 different tube voltage levels (28-32 kVp) under AEC setting. The detectability of microcalcifications was analyzed in terms of percentage correctly detected signals (PC) as well as diameter threshold (dtr), using the CHO and human observers. Two Laguerre-Gauss and 8 Gabor channels were included in the two-layers CHO. The model and human observer results were retrieved from a 4-alternative forced choice (4-AFC) study. At 28 kVp and 32 kVp, the diameter thresholds dtr of microcalcifications together with their 95% confidence intervals (CI95) were 0.114 [0.110-0.118] mm and 0.119 [0.116-0.122] mm for the CHO, and 0.110 [0.093-0.127] mm and 0.123 [0.111-0.134] mm for the human observers. The Pearson correlation (r) between the PC values of model and human observer was more than 0.934. The in-house developed CHO and the human observer scores correlated very well for the application on 2D digital mammography acquired with different tube voltages. The overlapping range of CI95 of the dtr for the tested kVp shows that the tube voltage setting does not significantly affect the detectability of microcalcifications neither by the CHO nor by the human observers.

Identification of Bullets Based on Their Metallic Components and X-Ray Attenuation Characteristics at Different Energy Levels on CT.

OBJECTIVE. This study aimed to identify bullets on the basis of their metallic components and to distinguish between ferromagnetic and nonferromagnetic bullets using CT. MATERIALS AND METHODS. Eight ferromagnetic, steel-jacketed lead bullets, four nonferromagnetic, non-steel-jacketed lead bullets, and four nonferromagnetic solid bullets composed of copper or copper and zinc alloys which we refer to here as "Cu(Zn) bullets," were scanned by CT at 80, 100, 120, and 140 kVp. Attenuation values (in Hounsfield units) were measured on an extended CT scale (ECTS) in the core and at the edge of the bullets and were used to calculate the dual-energy index (DEI). RESULTS. Although all nonferromagnetic bullets significantly differed from ferromagnetic bullets, the significant differences were solely attributed to the higher DEI of solid Cu(Zn) bullets compared with that of all-lead bullets. The lead bullets with ferromagnetic, steel-containing jackets did not differ from the lead bullets with nonferromagnetic, non-steel-containing jackets on the basis of DEIs obtained from core and edge measurements. Solid Cu(Zn) bullets could be clearly distinguished from lead bullets regardless of the metallic components of the jackets using DEI calculations from CT numbers on an ECTS. The DEIs based on the dual-energy pair 120 and 140 kVp appear to be the most appropriate for distinguishing between these two types of bullets. CONCLUSION. This study provides new scientific knowledge regarding metals and their characteristics at different tube voltage levels. The abilities of clinically approved dual-energy CT allow differentiation of bullets composed of low-atomic-number (Z) metals from bullets composed of high-Z metals via DEI calculations from CT numbers on an ECTS.

Optimal beam quality for chest flat panel detector system: realistic phantom study.

To investigate optimal beam quality for chest flat panel detector (FPD) system by semi-quantitatively assessment using a realistic lung phantom. Chest FPD radiographs were obtained on a realistic lung phantom with simulated lung opacities using various X-ray tube voltage levels (90-140kV) with/without copper filter. Entrance skin dose was set to maintain identical for all images (0.1mGy). Three chest radiologists unaware of the exposure settings independently evaluated the image quality of each simulated opacity and normal structure using a 5-point scale (+ 2: clearly superior to the standard; + 1: slightly superior to the standard; 0: equal to the standard; - 1: slightly inferior to the standard; - 2: clearly inferior to the standard). The traditional FPD image obtained at a tube voltage of 120kV was used as the standard. The scores of image quality were statistically compared using the Wilcoxon rank test with Bonferroni correction. FPD images using 90-kV shot with copper filter were superior to the traditional 120-kV shot without filter with respect to the visibility of vertebra, pulmonary vessels, and nodules overlapping diaphragm and heart (p < 0.05). There was no significant difference with respect to the visibility of all other simulated lung opacities (lung nodules except for overlying diaphragm/heart and honeycomb opacity) between each tube voltage level with/without copper filter and the traditional 120-kV shot without filter. Image quality of FPD images using 90kV with copper filtration is superior to that using standard tube voltage when dose is identical. • FPD image quality using 90kV with filter is superior to that using traditional beam. • Ninety-kilovolt shot with copper filter may be suitable for chest FPD image. • Clinical study dealing with chest FPD beam optimization would be warranted.

Minimizing individual variations in arterial enhancement on coronary CT angiographs using "contrast enhancement optimizer": a prospective randomized single-center study.

To investigate the clinical utility of our newly developed contrast enhancement optimizer (CEO) software for coronary CT angiography (CCTA). We randomly assigned 295 patients (168 males, 127 females, median age 71years) undergoing CCTA to one of two contrast media injection protocols. Group A (n = 150) was injected with a CEO-selected iodine dose based on patient factors. In group B (n = 145), we used our standard protocol (245mg I/kg). We recorded the CT number in the ascending aorta and determined whether the CT number was equivalent in groups A and B. For the equivalence test, we adopted 75Hounsfield units (HU) as the equivalence margin. The standard deviation in the CT number and the rate of patients with an acceptable CT number were compared using the F test and the chi-square test, respectively. The iodine dose in group A was significantly smaller than that in group B (235.7 vs. 253.6mg I/kg, p<0.001). The CT number of the ascending aorta was 428.6 ± 55.5HU in group A and 436.1 ± 68.7HU in group B; the 95% confidence interval for the difference between the groups was -4.3 HU to 16.9HU and within the range of the predetermined equivalence margins. In group A, the variance was significantly smaller than that in group B (p= 0.009). The number of patients with an acceptable CT number was significantly higher in group A than in group B (84.7% vs. 71.7%, p= 0.007). The use of our CEO for CCTA studies yielded optimal aortic contrast enhancement in significantly more patients than the standard protocol based on the body weight. • With our contrast enhancement optimizer (CEO) software, optimal and stable aortic enhancement can be obtained on coronary CT angiography scans irrespective of patient factors. • Management of contrast media becomes more appropriate by the CEO software. • The CEO software can control contrast enhancement at different tube voltage levels.

Computed Tomography Angiography of Coronary Artery Bypass Grafts: Low Contrast Media Volume Protocols Adapted to Tube Voltage.

The aim of this study was to evaluate the potential of contrast media (CM) reduction in computed tomography angiography (CTA) of coronary artery bypass grafts (CABGs) when adapting CM volume to automatically selected tube voltages. Sixty consecutive patients (mean age, 71 ± 14.5 years) with a total of 176 CABGs (692 bypass segments) underwent contrast-enhanced prospectively electrocardiography-gated high-pitch CTA with automated, attenuation-based tube voltage selection (100 ref. peak kilovoltage [kVp], 200 ref. mAs, tube voltages from 70-150 kVp in 10-kVp steps) using a third-generation 192-slice dual-source computed tomography scanner. Volume and flow of CM (370 mg/mL iodine) was adapted according to the tube voltages using iodine attenuation-curves derived from a foregoing phantom study. In patients, CM volumes ranged from 80 mL (flow rate, 7 mL/s) at 120 kVp to 48 mL (flow rate, 4.2 mL/s) at 80 kVp. Two independent, blinded readers evaluated subjective image quality of the proximal anastomosis, bypass graft, distal anastomosis, and postanastomotic native coronary artery using a 3-point Likert scale. Objective image quality (attenuation of graft and noise) was determined and contrast-to-noise ratio (CNR) was calculated. Volume computed tomography dose index and dose-length product of each CTA examination were noted. Cohen κ was used to define interreader agreement of subjective image quality. Regression analysis was used to determine relationships between tube voltage and vascular attenuation, image noise, and CNR. Using attenuation-based tube voltage selection, 5 patients (8%) were scanned at 80 kVp, 22 (37%) at 90 kVp, 11 (18%) at 100 kVp, 10 (17%) at 110 kVp, and 12 (20%) at 120 kVp. Agreement in subjective image quality between readers was good (κ = 0.678). Diagnostic image quality was achieved in 679 of 692 (98%) bypass segments in 169 of 176 bypass grafts (96%). Thirteen of 692 bypass segments (2%) in 7 of 176 bypass grafts (4%) were rated as nondiagnostic because of severe artifacts caused by motion or beam hardening (2 proximal anastomoses of sequential bypasses, 3 graft bodies, 5 distal anastomoses, and 3 postanastomotic coronary artery segments). Regression analysis revealed no significant relationship between the automatically selected tube voltages and objective image quality parameters (bypass graft attenuation: P = 0.315; noise: P = 0.433; and CNR: P = 0.168), indicating homogenous attenuation, noise, and CNR across tube voltage levels. Mean volume computed tomography dose index was 4.0 ± 0.9 mGy, and mean dose length product was 135.0 ± 29.6 mGy*cm. Adapting CM protocols to automatically selected tube voltage levels allows for low-volume CM CTA examinations of CABG grafts with diagnostic image quality.

Advanced modelled iterative reconstruction for abdominal CT: Qualitative and quantitative evaluation

To determine qualitative and quantitative image-quality parameters in abdominal imaging using advanced modelled iterative reconstruction (ADMIRE) with third-generation dual-source 192 section CT. Forty patients undergoing abdominal portal-venous CT at different tube voltage levels (90, 100, 110, and 120 kVp, n = 10 each) and 10 consecutive patients undergoing abdominal non-enhanced low-dose CT (100 kVp, 60 mAs) using a third-generation dual-source 192 section CT machine in the single-source mode were included. Images were reconstructed with filtered back projection (FBP) and ADMIRE (strength levels 1-5). Two blinded, independent readers subjectively determined image noise, artefacts, visibility of small structures, and image contrast, and measured attenuation in the liver, spleen, kidney, muscle, fat, and urinary bladder, and objective image noise. Subjective noise was significantly lower and image contrast significantly higher for each increasing ADMIRE strength level and also for ADMIRE 1 compared to FBP (all, p < 0.001). No significant differences were found for artefact and visibility ratings among image sets (all, p > 0.05). Attenuation was similar across tube voltage-image datasets in all anatomical regions (all, p > 0.05). Objective noise was significantly lower for each increasing ADMIRE strength level, and for ADMIRE 1 compared to FBP (all, p < 0.001, maximal reduction 53%). Independent predictors of noise were tube voltage (p < 0.05) and current (p < 0.001), diameter (p < 0.05), and reconstruction algorithm (p<0.001); the amount of noise reduction was related only to the reconstruction algorithm (p < 0.001). Abdominal CT using ADMIRE results in an improved image quality with lower image noise as compared with FBP, while the attenuation of various anatomical regions remains constant among reconstruction algorithms.

Differentiation of cocaine from heroine body packs by computed tomography: Impact of different tube voltages and the dual-energy index

Abstract Objectives To investigate the computed tomography (CT) attenuation values and the dual-energy index (DEI) of cocaine and heroin at different tube voltage settings in a phantom study. Materials and methods Thirty-three hand-wrapped bodypacks prepared of heroin ( n =17) and cocaine ( n =16) at varying concentrations were submerged in a 28-cm water tank and imaged four times with a dual-source 64-detector row CT at peak tube voltage levels of 80kVp, 100kVp, 120kVp, and 140kVp. Tube current in each protocol was adjusted for a similar CT volume dose index of 8.0mGy. Image noise and the CT attenuation values were measured in each drug container three times at each tube voltage level by two independent observers, and the DEI was calculated from measurements at 80kVp and 140kVp. Results Image noise at the four tube voltage levels was similar ( p =0.32). Intra- and interobserver agreement was good ( r =0.89 to.93; p p r =−0.67; p r =−0.15; p =0.23). Conclusions CT attenuation values measured at low tube voltage level and using the DEI improve the differentiation of cocaine and heroin-containing bodypacks compared to measurements at higher tube voltage settings.