kV Tube Research Articles

P116] Transition of the patient dose by the diagnostic X-ray examinations in the area of the local-area survey by the novel patient dose calculation system

Purpose The diagnostic reference level (DRLs) was proposed to a patient dose as a tool for optimization by diagnostic X-ray examination. The purpose of this study was to estimate the entrance surface dose for the different types of X-ray examinations of the hospital. In this study, a novel calculation system was developed for estimating the entrance surface doses and the result of the local survey about the patient dose of the local area was reanalyzed. Methods The entrance surface dose by novel calculation system (call estimation patient dose calculation system: EPD) is calculated using the parameter of an X-ray output (tube voltage, current time product, filtration, focus-skin distance, field size, etc.). The coefficient which standardized the output in each conditions based on the measurement result of a standard air kerma is used for this calculation system. Although the standard body thickness according to types of X-ray examination, exposure field size, etc. are used in initial setting, modification is also possible respectively. The entrance surface dose by means of survey continuously conducted by the Ibaraki Association of Radiologic Technologists from 1988 to the hospital in Ibaraki Prefecture was re-analyzed using this calculation system. Results As for the calculation result, a maximum of +20% of difference was confirmed to the measurement result of an ionization chamber type dosimeter (DC300: Wellhofer). However, it is proper as an estimate to the survey for attaining rationalization of a dose. There is a limit in accurate dose estimate by the range of 40–150 kV tube voltage, the difference in filtration, etc. Although the dose was a decline tendency on the whole in the re-analysis result of the patient dose by the novel dose calculation system, transition is trifling in recent years. Conclusions A novel calculation system was developed for estimating the entrance surface dose and the result of the local survey about the patient dose of the area was reanalyzed. The accuracy of dose estimation was investigated and the usefulness was confirmed. The transition of the level of the patient doses in a local area has been grasped.

Clinical value of 70 kV combined with low contrast agent CT scan in the diagnosis of pediatric coronary artery disease

Objective DSA and/or surgery was used as a control to evaluate the image quality, radiation dose and diagnostic efficacy of 70 kV combined with low contrast agent dose and 80 kV dual-source CT scanning of coronary artery. Methods Between Apr, 2012 and Apr, 2017, a total of 150 consecutive pediatrics with suspected or confirmed coronary arterial diseases underwent DSCTCA, and the patients were randomly divided into 3 groups by different scanning protocols. Group A (n=50): 80 kV with 1.5 ml/kg contrast agent; Group B (n=50): 70 kV with 1.5 ml/kg contrast agent;Group C (n=50): 70 kV with 1.0 ml/kg contrast agent. ANOVA was used to compare the differences of subjective coronary arteries image quality between the three groups;The t-test was used to compare the difference in effective radiation dose between the 70 kV group and the 80 kV group; The surgery and/or angiography results were used as gold standard to evaluate the diagnostic efficacy of the three groups. Results All patients underwent DSCTCA successfully and satisfactory diagnostic images were gained. The mean scores of subjective image quality of coronary artery were 3.5±0.7, 3.4±0.6, 3.7±0.8, respectively. There was no significant difference between the3 groups (F=2.042, P=0.133). The diagnostic accuracy of the three groups for coronary artery disease was 100%, as the surgical and/or angiographic results were used as gold standard. The effective radiation doses in 80 kV group (A group) and the 70 kV group (B+C group) were (0.49±0.04) and (0.30±0.03) mSv, respectively, with a statistically significant difference (t=4.037, P=0.001). Conclusions DSCTCA can better display and diagnose pediatric coronary artery lesions with 70 kV tube voltage combined with low contrast agent, and has a high diagnostic accuracy. It is a reliable method for diagnosing pediatric coronary artery disease. Key words: Child; Coronary arterial disease; Tomography, X-ray computed; Radiation dosage

Automatic contrast medium extraction system using electron density data with dual-energy CT.

The purpose of the current study is to create a contrast medium extraction method using raw-data-based electron density (rED) and CT number from dual-energy CT (DECT) for automatic delineation of the contrast region. A CT-ED phantom containing tissue-equivalent inserts and an acrylic phantom with an iodinated contrast medium were scanned by DECT. The contrast medium extraction system was created using Python. The accuracy of the contrast medium extraction was evaluated by measuring the diameter in terms of the full width at half maximum (FWHM) and the ratio of the volume (ROV). Mean-2SD CT numbers and the difference of the CT numbers (DCT) of the contrast medium at 0-130mgml-1 contrast medium concentration and the bone materials were more than -33 and -20 HU, respectively. In the correlation of rED and CT number, the gradient with the contrast medium phantom was greater than that with the CT-ED phantom. The accuracy of the contrast medium at 80 kV/135 kV and 100 kV/135 kV tube voltages. The gradient of the CT-ED and contrast medium phantoms were different. The gradient in the CT-ED phantom and the contrast medium was 0.0012 and 0.0003 at 80 kV/135 kV, and 0.0015 and 0.0005 at 100 kV/135 kV tube voltages, respectively. The ratio of the measured to the actual diameter in FWHM and ROV was 0.98-1.00 at 2-130 mg ml-1. At a tube voltage of 100 kV/135 kV. The ratio of the measured to the actual diameter in ROV was 0.66 and FWHM was 0.90 at 2mgml-1 contrast medium concentration. The ratio of the measured to the actual diameter in FWHM and ROV was 0.98-1.00 at 3-130 mg ml-1. We created the contrast medium extraction method with rED and CT number images. The contrast medium extraction method could be used with DECT images at 80 kV/135 kV. The method is expected to only extract images from the region containing the contrast medium. We created the contrast medium extraction method using raw-data-based electron density and CT number from DECT and it is expected to only extract information from the region containing the contrast medium.

Improved Diagnosis of Detection of Late Enhancement in Left Ventricular Myocardium Using 2nd Generation 320-Slice CT Reconstructed with FIRST in Non-Ischemic Cardiomyopathy.

Forward Projected Model-based Iterative Reconstruction SoluTion (FIRST) is a new reconstruction technique using CT, which provides successful reconstruction of high-quality CT images, especially in low contrast imaging. To evaluate improvements in the diagnostic accuracy of the detection of abnormal late enhancement (LE) in left-ventricular myocardium (LVM) using 320-slice CT with FIRST, we compared this modality with previous CT methods in patients with non-ischemic cardiomyopathy or a cardiac tumor.This was a retrospective study of 88 patients (56 males; 57 ± 15 years) suspected of having non-ischemic myocardial disease or a cardiac tumor. The first 52 consecutive patients (Group 1) underwent 16-slice CT at 140 kV tube voltage and an average tube current of 337 ± 20 mA, and 1.5 T MRI. The next 18 patients (Group 2) underwent 1st generation 320-slice CT at 120 kV tube voltage and an average tube current of 255 ± 106 mA, and 1.5T MRI; the remaining 18 patients (Group 3) underwent 2nd generation 320-slice CT with FIRST, at 80 kV tube voltage and a tube current of 800 mA, and 1.5T or 3T MRI.On patient-based analysis, no significant differences were observed between the 3 groups. For segment-based analysis, the specificity and overall accuracy were significantly higher (both P < 0.05) in Group 3 than in Group 1. Positive predictive value (PPV) was significantly higher in Group 3 than in Groups 1 and 2.The diagnostic accuracy of LE on CT for detecting myocardial fibrosis determined by late gadolinium-enhanced MRI was improved with the use of 2nd generation 320-slice CT with FIRST, in particular regarding specificity, PPV, and overall accuracy.

Study of Image Quality, Radiation Dose and Low Contrast Resolution from MSCT Head by Using Low Tube Voltage

Effect of low tube voltage (80 kV) on image quality, radiation dose, and low contrast (LCD) detection capability on CT Scan head was studied by using a solid phantom contains four modules with scanning CT at 80 and 120 kV tube voltages, with tube current timing at 200, 250 and 300 mAs. The difference between image noise, noise to ratio contrast and LCD values obtained with 80 and 120 kV at 200, 250 and 300 mAs were then compared. Substantially the image noise increases with the use of low tube voltage. However, with the same dose, the LCD values are between 120 kV at 300 mAs and 80 kV at 200, 250 and 300 mAs (P> 0.05). The relative dose given at 80 kV against 200, 250 and 300 mAs is equal to 68%. By reducing the tube voltage from 120 kV to 80 kV at head CT, the radiation dose can be reduced by 32% without CNR and LCD degradation.

Исследование влияния факторов кондиционной среды, полученной при культивировании мезенхимальных стволовых клеток костного мозга, на течение тяжелых местных лучевых поражений кожи у крыс

Purpose: Study of the effect of paracrine factors, produced by MMSC of bone marrow during the cultivation, on the severity of local radiation injuries in the conditions of application in the early periods after irradiation. Material and methods: Experiments were performed on rats of the breed Wistar weighing 280 g. Rats were exposed locally in iliolumbar region of the back using X-ray machine LNC-268 (RAP 100-10) at a dose of 110 Gy (30 kV tube voltage, current 6.1 mA, filter Al 0.1 mm thick), dose rate is 21.4 Gy/min. Area of the irradiation field was 8.2–8.5 cm2. The conditioned medium obtained by culturing MMSC of rats’ bone marrow was administered in dose 1.0 ml (total protein 8 mg/ml) at 1, 3, 6, 8 and 10 days after irradiation. The severity of radiation damage to the skin and the effects of therapy were evaluated in dynamics by clinical manifestations, using planimetry and histological methods. Results: It was shown that in control animals and in rats, with the introduction of the conditioned medium, the values of the skin lesion area in the period up to the 29th day after irradiation practically did not differ, gradually decreasing in control animals from 5.9 ± 0.6 cm2 to 2.2 ± 0.3 cm2 at the 15th and 29th days after irradiation, respectively. Then, in the control group, the lesion area ranged from 1.4 ± 0.6 cm2 on the 50th day to 1.9 ± 0.8 cm2 on the 71st day. In the experimental group of animals, with the introduction of factors of the conditioning medium, a decrease in the area of the lesion and a stable dynamics of healing of radiation ulcers, beginning from the 36th day, there was a gradual decrease in the area of the lesion, which reached 0.2 ± 0.1 cm2 by the 71st day after irradiation. On the 64–71th day after irradiation, the difference between the areas of skin lesion in the experimental and control groups was statistically significant, p &lt;0.05. The histological analysis showed that the use of paracrine factors obtained from MMSC in the process of cultivation significantly reduces the severity of the inflammatory reaction and accelerates the regeneration processes. Conclusion: Thus, the introduction of conditioned medium factors obtained during the cultivation of mesenchymal stem cells of the bone marrow facilitates a more easy flow of the pathological process and the healing of radiation ulcers after local radiation damage to the skin of rats. Apparently, the favorable effect of paracrine factors introduced in the early periods after irradiation, with severe local radiation injuries, is associated with their effect on pathological processes in the inflammatory-destructive stage.

Applicability of a clinical cardiac CT protocol in post mortem studies

Abstract Objective Confirmation whether an optimized clinical cardiac CT scan protocol is also optimal for post mortem cardiac CT scans without iodine contrast or the reconstruction parameters should be changed. Materials and methods 27 CT volumes (three cases for three recon- struction kernel with three different iterative reconstruction settings) were graded by six readers in order to find the optimal reconstruction parame- ters. The scans were performed on a Siemens Definition Flash CT scanner using 120 kV tube potentials. Results The study has shown that from the investigated options the softest cardiac kernel with the strongest iterative reconstruction were pre- ferred by the readers (I26 Safire 3). Conclusion The results indicate that the scan protocol which was adopted from clinical practice is applicable in forensic radiology too even though iodine contrast agent was not administered.

Improved imaging of colorectal liver metastases using single-source, fast kVp-switching, dual-energy CT: preliminary results.

PurposeComputed tomography remains the first-choice modality for assessment of colorectal cancer liver metastases (CRLM). Dual-energy computed tomography (DECT) is a relatively new technique that is becoming increasingly available. One of the advantages of DECT is the ability to maximise iodine detection. Our aim was to test whether single-source, fast kVp-switching DECT can improve imaging quality of CRLM compared to conventional (polychromatic) CT.Material and methodsTwenty consecutive patients were enrolled into a preliminary prospective study. The scanning protocol consisted of four phases: non-contrast with standard 120 kV tube voltage and three post-contrast phases with rapid voltage switching. As a result, three sets of images were reconstructed: pre- and postcontrast polychromatic (PR), monochromatic (MR), and iodine concentration map (IM). To compare the sensitivity of the tested reconstructions, the number of CRLMs and the maximum diameter of the largest lesion were calculated. Objective image quality was measured as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The radiation dose was expressed as CTDIvol.ResultsImaging was successfully performed in all patients. The number of detected lesions was significantly lower on PR images than on IM and MR 50-70 keV (mean number: 4.20 and 4.45, respectively). IM and MR at 70 keV presented the highest quality. SNR was significantly higher for IM and 70 keV images than for other reconstructions. The mean radiation dose was 14.61 mGy for non-contrast 120 kV scan and 17.89 mGy for single DECT scan (p < 0.05).ConclusionsDECT is a promising tool for CRLM imaging. IM and low-photon energy MR present the highest differences in contrast between metastases and the normal liver parenchyma.

Evaluation of a Reconstruction Algorithm in Clinically Low-Dose Computed Tomography: Comparison of Phantom Images at various Contrast Media Concentrations

To evaluate the feasibility of using clinically low-dose computed tomography (CT) with an iterative reconstruction (IR) algorithm in CT angiography (CTA) with various contrast media (CM) concentrations. We performed a phantom study using 128-channel MDCT with 270, 300, and 350 mg iodine/ml, first at 120 kV tube voltage combined with a conventional algorithm (standard protocol), and then at clinically low dose (80 kV), combined with conventional (filtered back-projection; FBP) and IR (ASIR-V) algorithms. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the tube centre and background were measured and the clinical radiation dose (CTDIVoL) determined.

Image quality and radiation dose of low-tube-voltage CT with reduced contrast media for right adrenal vein imaging

ObjectivesTo compare image quality and radiation dose of right adrenal vein (RAV) imaging computed tomography (CT) among conventional, low kV, and low kV with reduced contrast medium protocols. MethodsOne-hundred-and-twenty patients undergoing adrenal CT were randomly assigned to one of three protocols: contrast dose of 600mgI/kg at 120-kV tube voltage setting (600-120 group), 600mgI/kg at 80kV (600-80 group), and 360mgI/kg at 80kV (360-80 group). Iterative reconstruction was used for 80-kV groups. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the RAV and size-specific dose estimates (SSDE) were measured. Three radiologists evaluated 4-point visualisation scores of RAV by consensus reading. ResultsThe RAV detectability was 95%, 97.2%, and 97.3% for 600-120, 600-80, and 360-80 groups, respectively (p=1.000). Visualisation scores were not significantly different among the groups (p=0.152). There were no significant differences in CNR or SNR between the 600-120 and 360-80 groups. SSDE of the 360-80 group was significantly lower than that of the 600-120 group (5.86mGy±1.44 vs. 7.27mGy±1.81, p<0.001). Conclusions80-kV scans with 360 mgI/kg contrast media showed comparable detectability of RAV to conventional scans, while reducing 19% of SSDE.

Improving CT quality with optimized image parameters for radiation treatment planning and delivery guidance

Abstract Background and purpose CT scan protocols are often created with imaging parameters set to minimize imaging dose with acceptable image quality for diagnostic purpose. This study aimed to optimize CT imaging parameters to help accurately delineate structures for radiation therapy planning and delivery guidance. Materials and methods Imaging parameters were optimized with CT data acquired for a phantom to create image quality enhancement (IQE) protocols, which were subsequently used to scan a prostate and a pancreatic cancer patient who underwent image-guided radiotherapy (IGRT). The patient images were compared with those scanned with standard clinical protocols, the quality of these images was assessed with various methods (survey, inter- and intra-observer variations, and dice coefficient analysis) for the two patient cases. Results An effective tube current–time product of ∼1000 mAs was found to be a reasonable choice to balance CT quality and CT dose. With increased dose and penetration taken into account, 100 and 120 kV tube voltages were found appropriate for the IQE protocols. The inter- and intra-observer variations for the IQE data were smaller than those with the standard protocols. Dice coefficient analysis indicated that the IQE protocols lead to improved dice coefficient by as much as 8 percentage points for the two cases studied. Conclusion CT image quality can be improved with the IQE protocols created in this study, to provide better soft tissue contrast, which would be beneficial for use in radiation therapy, e.g., for planning data acquisition or for IGRT for hypo-fractionated treatments.

Low Tube Voltage Liver MDCT with Sinogram-Affirmed Iterative Reconstructions for the Detection of Hepatocellular Carcinoma

Aim of this study was to compare low tube voltage computed tomography (80 kV) of the liver using iterative image reconstruction (SAFIRE) with standard computed tomography (120 kV) using filtered back-projection (FBP) for the detection of hepatocellular carcinoma (HCC). 46 patients (43 men) with 93 HCC confirmed by 3 T MRI with Gd-EOB-DPTA, in inconclusive cases combined with contrast-enhanced ultrasound, underwent dual-energy CT. The raw data of the 80 kV tube was reconstructed using the iterative reconstruction algorithm SAFIRE with two strengths (I3 and I5). The virtual 120 kV image data set was reconstructed using FBP. The CT images were reviewed to determine the lesion-to-liver contrast (LLC), the lesion contrast-to-noise ratio (CNR) and the sensitivity. The LLC (57.1/54.3 [I3/I5] vs. 34.9 [FBP]; p ≤ 0.01), CNR (3.67/4.45 [I3/I5] vs. 2.48 [FBP]; p < 0.01) and sensitivity (91.4%/88.2% [I3/I5] vs. 72.0% [FBP]; p ≤ 0.01) were significantly higher in the low-voltage protocol using SAFIRE. Therefore, low tube voltage CT using SAFIRE results in an increased lesion-to-liver contrast as well as an improved lesion contrast-to-noise ratio compared to FBP at 120 kV which results in a higher sensitivity for the detection of HCC.

Cardiac-Specific Conversion Factors to Estimate Radiation Effective Dose From Dose-Length Product in Computed Tomography

ObjectivesThis study sought to determine updated conversion factors (k-factors) that would enable accurate estimation of radiation effective dose (ED) for coronary computed tomography angiography (CTA) and calcium scoring performed on 12 contemporary scanner models and current clinical cardiac protocols and to compare these methods to the standard chest k-factor of 0.014 mSv·mGy−1cm−1. BackgroundAccurate estimation of ED from cardiac CT scans is essential to meaningfully compare the benefits and risks of different cardiac imaging strategies and optimize test and protocol selection. Presently, ED from cardiac CT is generally estimated by multiplying a scanner-reported parameter, the dose-length product, by a k-factor which was determined for noncardiac chest CT, using single-slice scanners and a superseded definition of ED. MethodsMetal-oxide-semiconductor field-effect transistor radiation detectors were positioned in organs of anthropomorphic phantoms, which were scanned using all cardiac protocols, 120 clinical protocols in total, on 12 CT scanners representing the spectrum of scanners from 5 manufacturers (GE, Hitachi, Philips, Siemens, Toshiba). Organ doses were determined for each protocol, and ED was calculated as defined in International Commission on Radiological Protection Publication 103. Effective doses and scanner-reported dose-length products were used to determine k-factors for each scanner model and protocol. Resultsk-Factors averaged 0.026 mSv·mGy−1cm−1 (95% confidence interval: 0.0258 to 0.0266) and ranged between 0.020 and 0.035 mSv·mGy−1cm−1. The standard chest k-factor underestimates ED by an average of 46%, ranging from 30% to 60%, depending on scanner, mode, and tube potential. Factors were higher for prospective axial versus retrospective helical scan modes, calcium scoring versus coronary CTA, and higher (100 to 120 kV) versus lower (80 kV) tube potential and varied among scanner models (range of average k-factors: 0.0229 to 0.0277 mSv·mGy−1cm−1). ConclusionsCardiac k-factors for all scanners and protocols are considerably higher than the k-factor currently used to estimate ED of cardiac CT studies, suggesting that radiation doses from cardiac CT have been significantly and systematically underestimated. Using cardiac-specific factors can more accurately inform the benefit-risk calculus of cardiac-imaging strategies.

Response of optically stimulated luminescence dosimeters subjected to X-rays in diagnostic energy range

The use of optically stimulated luminescence (OSL) for dosimetry applications has recently increased considerably due to availability of commercial OSL dosimeters (nanoDots) for clinical use. The OSL dosimeter has a great potential to be used in clinical dosimetry because of its prevailing advantages in both handling and application. However, utilising nanoDot OSLDs for dose measurement in diagnostic radiology can only be guaranteed when the performance and characteristics of the dosimeters are apposite. In the present work, we examined the response of commercially available nanoDot OSLD (Al2O3:C) subjected to X-rays in general radiography. The nanoDots response with respect to reproducibility, dose linearity and signal depletion were analysed using microStar reader (Landauer, Inc., Glenwood, IL). Irradiations were performed free-in-air using 70, 80 and 120 kV tube voltages and tube currents ranging from 10 – 100 mAs. The results showed that the nanoDots exhibit good linearity and reproducibility when subjected to diagnostic X-rays, with coefficient of variations (CV) ranging between 2.3% to 3.5% representing a good reproducibility. The results also indicated average of 1% signal reduction per readout. Hence, the nanoDots showed a promising potential for dose measurement in general X-ray procedure.

Трансплантация аутологичных клеток стромально-васкулярной фракции жировой ткани при тяжелых местных лучевых поражениях кожи, вызванных действием рентгеновского излучения

Purpose: To investigate the effectiveness of autologous cells of stromal vascular fraction of adipose tissue in severe local radiation skin injuries after the&#x0D; exposure of rats to X-rays.&#x0D; Material and methods: Experiments were performed on Wistar rats, weighing 200–230 g. Rats were exposed locally in iliolumbar region using X-ray&#x0D; machine LNC-268 (RAP 100-10) at a dose of 110 Gy (30 kV tube voltage, current 6.1 mA, thick Al filter 0.1 mm), dose rate: 17.34 Gy/min. Area of the&#x0D; irradiation field was 8.2–8.5 cm2. Transplantation of autologous cells of stromal vascular fraction (SVFC) of adipose tissue was carried out on 21st or 35th&#x0D; days after irradiation. SVFC isolation was performed by means of enzymatic treatment of adipose tissue. SVFC suspension was administered subcutaneously&#x0D; at a dose of 1×106 cells per injection around the radiation ulcers.The severity of radiation damage to the skin and the effects of cellular therapy were evaluated&#x0D; in the dynamics of clinical manifestations, with the help of plane geometry and pathomorphometry.&#x0D; Results: It was found that by the 17–25th day after irradiation radiation ulcers were formedon rat skin. In the control group of animalsulcers persisted&#x0D; throughout the observation period of more than 3 months. The area of ulcers was 1,87 ± 0,35 cm2 and 1.52 ± 0.24 cm2 at 83th and 90th days after irradiation,&#x0D; respectively. In animals of the experimental group, with autologous stromal vascular fraction of adipose tissue, was significant decrease in ulceration the&#x0D; area in comparison to control animals. In 80 % of the rats treated with SVFC on 21st day after exposure, to the 90th day after irradiation complete healing&#x0D; of ulcers occurred with the formation of atrophic scar at the site of radiation injuries. These clinical observations and planimetric were correlated with the&#x0D; results of histomorphometry.&#x0D; Conclusion: Transplantation autologous SVFC of adipose tissue contributes to accelerate the healing of radiation ulcers after local x-ray exposure in the&#x0D; experiment, indicating that the prospects of using adipose tissue cell products for the treatment of severe local radiation injuries.

Application of Low Tube Voltage 70 kV and Advanced Modeled Iterative Reconstruction in the Third-generation Dual-source CT to CT Colonography.

Objective To explore the feasibility of reducing radiation dose of CT colonography (CTC) while preserving image quality using the third-generation dual-source CT at 70 kV tube voltage with advanced modeled iterative reconstruction (ADMIRE). Methods This prospective study consecutively included 53 patients. All patients underwent CTC at 120 kV in supine position with filtered back projection reconstruction and at 70 kV in prone position with ADMIRE with the same scan range. Radiation dose and image quality were compared between these two protocols. Results CT dose index volume,dose-length product,and effective dose of 70 kV were (1.47±0.23)mGy,(68.85±13.82)mGy·cm,and (1.03±0.21)mSv,respectively,which were significantly lower than 120 kV mode [(2.96±0.61)mGy (t=25.356,P=0.000),(136.97±32.77)mGy·cm (t=22.246,P=0.000),and (2.05±0.49)mSv (t=22.293,P=0.000)]. Signal to noise ratio of 70 kV with ADMIRE was 3.60±0.58,which was obviously higher than that of 120 kV as 2.34±0.47 (t=-18.036,P=0.000). Noise of 70 kV with ADMIRE was (11.81±1.93)HU,which was obviously lower than that of 120 kV as (14.39±2.57)HU (t=7.856,P=0.000). The κ value of two radiologists' overall subjective image score was 0.843 (P=0.000). For 2D images,the noise score of 70 kV with ADMIRE was significantly lower (Z=325.000,P=0.000) and the overall image quality was significantly higher (Z=78.000,P=0.001) compared with 120 kV;however,the sharpness had no significant difference. All scores ranged from 4 to 5. For 3D virtual endoscopy,the overall image quality of 70 kV with ADMIRE and 120 kV was not significantly different (Z=4.000,P=0.059),and all scores ranged from 4 to 5. Conclusion CTC at 70 kV tube voltage combined with ADMIRE can remarkably reduce the radiation dose while maintaining imaging quality than 120 kV at third-generation dual-source CT.

Feasibility of Peripheral Artery CT Angiography under 70 kV with 50 ml Contrast Medium on the Third-generation Dual-source CT.

Objective To evaluate the feasibility of peripheral artery CT angiography (CTA)under 70 kV with 50 ml contrast medium on the third-generation dual-source CT. Methods Totally 82 patients who were equally randomized into two groups:70 kV group:the scan was performed under 70 kV tube voltage+50 ml iopromide on the third-generation dual-source CT;and 100 kV group:the scan was performed under 100 kV tube voltage+90 ml iopromide on the second-generation dual-source CT. The CT number of abdominal aorta,bilateral common iliac arteries,common femoral arteries,superficial femoral arteries,popliteal arteries and arteries of the calf were measured and contrast to noise ratio(CNR),signal to noise ratio(SNR)were calculated. The image quality was compared between these two groups. Results The dose-length product was (195.8±46.9)mGy·cm in 70 kV group,which was significantly lower than that in 100 kV group (461.6±57.9)mGy·cm,and was decreased by 57% (t=-22.848,P=0.000). Compared with the 100 kV group,the CT number of the proximal abdominal aorta in 70 kV group was significantly lower(t=-2.502,P=0.014),while the CT number of superficial femoral arteries (t=3.053,P=0.003)and popliteal arteries (t=4.013,P=0.000)was much higher in 70 kV group. SNR and CNR of proximal abdominal aorta,distal abdominal aorta,bilateral common iliac arteries,common femoral arteries,superficial femoral arteries,popliteal arteries and arteries of the calf were significantly lower in 70 kV group than those in 100 kV group (all P<0.05). The artifacts in abdominal aorta (t=2.893,P=0.000)and feet arteries (t=3.776,P=0.000)were higher in 70 kV group than those in 100 kV group,the enhancement of abdominal aorta (t=-1.000,P=0.002)and feet arteries (t=2.893,P=0.010)were lower in 70 kV group,the enhancement of femoral-popliteal arteries (t=-1.000,P=0.000)and arteries of calf (t=4.261,P=0.000)were higher in 70 kV group. Compared with the 100 kV group,the image noise in aorta (t=2.048,P=0.044),femoral-popliteal arteries (t=8.370,P=0.000),arteries of the calf (t=8.315,P=0.000)and feet arteries (t=7.202,P=0.000)were higher in 70 kV group. Conclusion Compared to conventional scan protocol,using 70 kV tube voltage with 50 ml contrast medium to perform peripheral artery CTA can assure the image quality and meanwhile remarkably reduce the radiation dose and the use of contrast medium.

Third-generation Dual-source CT for Head and Neck CT Angiography with 70 kV Tube Voltage and 20-25 ml Contrast Medium in Patients With Body Weight Lower than 75 kg.

Objective To investigate the image quality of head and neck CT angiography (CTA)using the third-generation dual-source CT combined with 70 kV tube voltage and 20-25 ml contrast medium (CM),and evaluate the effects of venous artifacts arising from the CM on the ipsilateral side of injection. Methods Totally 40 consecutive patients with suspected vascular diseases and body weight lower than 75 kg prospectively underwent head and neck CTA examination using the third-generation dual-source CT. CTA was performed with a third-generation dual-source CT system. Patients were randomly divived into 70 kV group (n=20)and 100 kV group (n=20). The 70 kV group used 20-25 ml CM and advanced modeled iterative reconstruction technique,and the 100 kV group used 40 ml CM and filtered back projection. Venous artifacts and CM residues were evaluated by a 3-point scale (1=excellent,3=poor),respectively. Results The effective dose of 70 kV group decreased 58% compared to 100 kV group (t=-18.14,P<0.001).In the 70 kV group,16 patients (80.0%)presented with venous artifacts and six of them (37.5%,6/16)affected the adjacent arteries. In the 100 kV group,19 patients (95.0%)presented with venous artifacts,and seven of them (36.8%,7/19)affected the adjacent arteries (Z=-0.878,P=0.380). In the 70 kV group,13 patients (65.0%)presented with obvious CM residues and two of them (15.3%,2/13)prolonged into the superior vena cava (SVC). In the 100 kV group,19 patients(95.0%)presented with obvious CM residues,and thirteen of them(68.4%,13/19)prolonged into the SVC (Z=-3.654,P<0.001). Conclusion Compared with the 100 kV,the third-generation dual-source CT for head and neck CTA,combined with 70 kV and 20-25 ml CM,can remarkably decrease the radiation dose,along with reduced CM residues and comparable venous artifacts.

Application of High-pitch CT Pulmonary Angiography at 70 kV Tube Voltage with 15 ml Contrast Medium Using Third-generation Dual-source CT.

Objective To assess the application of high-pitch CT pulmonary angiography (CTPA) at 70 kV tube voltage with 15 ml contrast medium using third-generation dual-source CT. Methods A total of 70 patients with clinically suspected pulmonary embolism were randomly divided into two groups: group A (n=35) underwent CTPA on conventional scanning mode (120 kV,80 ml contrast medium);and group B (n=35) underwent CTPA on high-pitch scanning mode at 70 kV tube voltage with 15 ml contrast medium. The CT values and standard deviations of the main pulmonary artery,apical segment of right upper pulmonary lobe (S1),and posterior basal segment of the right lower pulmonary lobe (S10),anterior thoracic air,and back muscles were measured. The signal to noise ratio (SNR),contrast to noise ratio (CNR),and effective dose (ED) were calculated. The overall image quality was evaluated by two blinded radiologists. The quality image was compared using non-parametric test on two independent samples. The potential differences in CT value,SNR,CNR,and ED were analyzed using the independent sample t-test. Results The CT values of main pulmonary artery [(300.62±77.54)HU vs.(332.80±102.80)HU;t=-1.53,P=0.13],S1 [(361.72±84.92)HU vs. (325.37±87.86)HU;t=1.81,P=0.08],and S10 [(359.54±89.61)HU vs. (318.26±87.19)HU;t=2.00,P=0.05] of right lung were not significantly different between group A and group B. The CNR of S1 (22.81±6.05 vs. 19.80±6.60;t=2.05,P=0.04) and S10 (22.65±6.37 vs. 19.28±6.63;t=2.23,P=0.03) of right lung in group A was significantly higher than in group B. The SNR of main pulmonary artery,S1,and S10 of right lung were not significantly different between group A and B. The subjective diagnostic quality values of group A and B were 1 (1,1) and 1 (1,1),respectively (Z=-0.08,P=0.93). The subjective diagnostic quality values evaluated by two radiologists showed excellent consistency(κ=0.87,P=0.01). The mean ED was 79% lower in group B [(0.92±0.23)mSv] than in group A [(4.33±1.80) mSv] (t=11.72,P=0.00).Conclusion Application of high-pitch mode in CTPA at 70 kV with 15 ml contrast medium using third-generation dual-source CT can remarkably reduce radiation dose without affecting image quality.

Dose Optimization for Computed Tomography Localizer Radiographs for Low-Dose Lung Computed Tomography Examinations.

Recent studies have shown a substantial reduction of radiation dose from computed tomography (CT) scans down to 0.1 mSv for lung cancer screening and cardiac examinations, when applying optimization techniques. Hence, CT localizer radiographs (LRs) might now be considered a significant contributor to the total dose of the CT examination. We investigated in our study the potential for reducing dose of the LRs by adapting the patient-specific acquisition parameters of the LR. Localizer radiographs covering the lungs were acquired on 2 clinical scanners (64 slices, conventional detector [CD]; 96 slices, fully integrated detector [ID]) for 3 semianthropomorphic phantoms, representing a slim, a normal, and an obese adult. Starting at 120-kV tube voltage and 250-mA current were reduced until the image quality of the LR, and thereby the accuracy of the automatic exposure control was compromised; this was defined as a deviation of measured attenuation values in the center of the LR of more than 5% from the reference values measured at the highest tube voltage and current. Subsequent Monte Carlo calculations on anthropomorphic phantoms were performed to calculate organ and effective dose values for the respective optimal settings. In addition, effective dose values normalized to CTDIvol for tube voltages ranging from 60 to 160 kV were determined for the different combinations of phantom sizes, sexes, and LR views to evaluate dose efficiency. For the CD scanner, the optimal LR settings depended strongly on phantom size. Higher tube voltage and current were necessary for the larger phantoms. The ID scanner showed uncompromised LR quality for all phantoms using the lowest possible tube voltage-tube current combination of 80 kV and 20 mA. Depending on patient size and LR direction, effective dose values for the optimal settings ranged from 6 to 53 μSv and 3 to 11 μSv for the CD and ID scanner, respectively. For the example of an anterior-posterior LR on a normal patient, using the optimal settings instead of the standard settings on the ID scanner reduced LR dose from 53 μSv (120 kV, 30 mA) to 10 μSv (80 kV, 20 mA). The simulations for the different tube voltages show that effective dose and CTDIvol behave similarly for different views and patient sizes. However, the tube voltage level itself impacts the relationship between CTDIvol and effective dose, by up to a factor of 2. Dose from LRs may contribute significantly to the total effective dose of low-dose CT examinations such as lung cancer screening. Optimal LR settings can reduce LR dose substantially, but adaptations have to consider scanner characteristics, detector technology, and patient size. Thus, for low-dose CT examinations, such as cardiac examinations and lung cancer screening, LR optimization may result in a significant dose reduction and thereby in a substantial reduction of total dose.