Pepper mild mottle virus intended for use as a process indicator for drinking water treatment: Present forms and quantitative relations to norovirus and rotavirus in surface water.

Pepper mild mottle virus (PMMoV) has been proposed as a potential indicator of human enteric viruses in environmental water and for viral removal during drinking water treatment. To investigate the occurrence and present forms of PMMoV and quantitative relations to norovirus GII and rotavirus A (RVA) in surface waters, 147 source water samples were collected from 21 drinking water treatment plants (DWTPs) in Japan between January 2018 and January 2021, and the concentrations of viruses in suspended and dissolved fractions were measured using real-time RT-PCR. PMMoV was detected in 81-100 % of samples in each sample month and observed concentrations ranged from 3.0 to 7.0 log10 copies/L. The concentrations of PMMoV were higher in dissolved fraction compared to suspended fractions, while different partitioning was observed for NoV GII depending on seasons. The concentrations of PMMoV were basically higher than those of norovirus GII (1.9-5.3 log10 copies/L) and RVA (1.9-6.6 log10 copies/L), while in 18 samples, RVA presented higher concentrations than PMMoV. Partial regions of VP7, VP4, and VP6 of the RVA in the 18 samples were amplified using nested PCR, and the genotypes were determined using an amplicon-based next-generation sequencing approach. We found that these source water samples included not only human RVA but also various animal RVA and high genetic diversity due to the existence of animal RVA was associated with a higher RVA concentration than PMMoV. Our findings suggest that PMMoV can be used as an indicator of norovirus GII and human RVA in drinking water sources and that the indicator performance should be evaluated by comparing to zoonotic viruses as well as human viruses.

Comparison of pediatric lens scattered dose measurements between axial 40-mm and helical 160-mm detector width computed tomography scan modes.

BACKGROUND: Reports comparing field lens doses between helical scans with a 40-mm detector width and axial scans with a 160-mm detector width using different computed tomography (CT) scanners are currently scarce. OBJECTIVE: To compare scatter doses for lenses between a helical scan with a 40-mm detector width and an axial scan with a 160-mm detector width when using different CT scanners in the context of pediatric chest examinations. MATERIALS AND METHODS: Two different CT machines were used: Revolution CT (GE Healthcare, Waukesha, WI) with a 256-row, 0.625-mm multidetector; and Aquilion ONE GENESIS Edition (Canon Medical Systems, Otawara, Japan) with a 320-row, 0.5-mm multidetector. Three pediatric anthropomorphic phantoms were used, with optically stimulated luminescence dosimeters (OSLDs) placed on the left and right lenses. The scatter dose values measured by the OSLDs were compared between a helical scan with a 40-mm detector width and an axial scan with a 160-mm detector width during pediatric chest CT examinations. RESULTS: Median equivalent doses for the helical and axial scans were 0.12 and 0.12 mSv/mGy for the newborn, 0.17 and 0.16 mSv/mGy for the 1-year-old, and 0.18 and 0.15 mSv/mGy for the 5-year-old, respectively, when using the Revolution CT. With the Revolution CT, no significant differences were observed in the scatter doses between helical and axial scans in the newborn and 1-year-old phantoms. However, the lens scatter dose for the helical scan was approximately 20-35% higher than that for the axial scan in the 5-year-old phantom (P<0.01). The median equivalent doses of eye lenses for the helical and axial scans were 0.12 and 0.07 mSv/mGy for the newborn, 0.07 and 0.05 mSv/mGy for the 1-year-old, and 0.14 and 0.12 mSv/mGy for the 5-year-old, respectively, when using the Aquilion ONE. With the Aquilion ONE, lens scatter doses for the helical scan were approximately 70%, 40%, and 30% higher in the newborn, 1-year-old, and 5-year-old phantoms, respectively, than those for the axial scan (P<0.01). CONCLUSIONS: When using the Aquilion ONE, lens scatter doses for the helical scan were significantly higher in all three phantoms than those for the axial scan. In contrast, when using the Revolution CT, the lens scatter dose for the helical scan was significantly higher in the 5-year-old phantom than that for the axial scan. These results suggest that although scattered doses may vary with respect to the CT scanner and body size, they are generally lower in the case of axial scans.

Prediction of endovascular leaks after thoracic endovascular aneurysm repair though machine learning applied to pre-procedural computed tomography angiographs.

To predict endoleaks after thoracic endovascular aneurysm repair (TEVAR) we submitted patient characteristics and vessel features observed on pre- operative computed tomography angiography (CTA) to machine-learning. We evaluated 1-year follow-up CT scans (arterial and delayed phases) in patients who underwent TEVAR for the presence or absence of an endoleak. We evaluated the effect of machine learning of the patient age, sex, weight, and height, plus 22 vascular features on the ability to predict post-TEVAR endoleaks. The extreme Gradient Boosting (XGBoost) for ML system was trained on 14 patients with- and 131 without endoleaks. We calculated their importance by applying XGBoost to machine learning and compared our findings between with those of conventional vessel measurement-based methods such as the 22 vascular features by using the Pearson correlation coefficients. Pearson correlation coefficient and 95% confidence interval (CI) were r = 0.86 and 0.75 to 0.92 for the machine learning, r = - 0.44 and - 0.56 to - 0.29 for the vascular angle, and r = - 0.19 and - 0.34 to - 0.02 for the diameter between the subclavian artery and the aneurysm (Fig. 3a-c, all: p < 0.05). With machine-learning, the univariate analysis was significant higher compared with the vascular angle and in the diameter between the subclavian artery and the aneurysm such as the conventional methods (p < 0.05). To predict the risk for post-TEVAR endoleaks, machine learning was superior to the conventional vessel measurement method when factors such as patient characteristics, and vascular features (vessel length, diameter, and angle) were evaluated on pre-TEVAR thoracic CTA images.

Using Patient-Specific Contrast Enhancement Optimizer Simulation Software During the Transcatheter Aortic Valve Implantation-Computed Tomography Angiography in Patients With Aortic Stenosis.

OBJECTIVES: This study assessed whether patient-specific contrast enhancement optimizer simulation software (p-COP) can reduce the contrast material (CM) dose compared with the conventional body weight (BW)-tailored scan protocol during transcatheter aortic valve implantation-computed tomography angiography (TAVI-CTA) in patients with aortic stenosis. METHODS: We used the CM injection protocol selected by the p-COP in group A (n = 30). p-COP uses an algorithm that concerns data on an individual patient's cardiac output. Group B (n = 30) was assigned to the conventional BW-tailored CM injection protocol group. We compared the CM dose, CM amount, injection rate, and computed tomography (CT) values in the abdominal aorta between the 2 groups and classified them as acceptable (>280 Hounsfield units (HU)) or unacceptable (<279 HU) based on the optimal CT value and visualization scores for TAVI-CTA. We used the Mann-Whitney U test to compare patient characteristics and assess the interpatient variability of subjects in both groups. RESULTS: Group A received 56.2 mL CM and 2.6 mL/s of injection, whereas group B received 76.9 mL CM and 3.4 mL/s of injection (P < 0.01). The CT value for the abdominal aorta at the celiac level was 287.0 HU in group A and 301.7HU in group B (P = 0.46). The acceptable (>280 HU) and unacceptable (<280 HU) CT value rates were 22 and 8 patients in group A and 24 and 6 patients in group B, respectively (P = 0.76). We observed no significant differences in the visualization scores between groups A and B (visualization score = 3, P = 0.71). CONCLUSION: The utilization of p-COP may decrease the CM dosage and injection rate by approximately 30% in individuals with aortic stenosis compared with the body-weight-tailored scan protocol during TAVI-CTA.

Evaluation of overexposure risk when there is a space between the subject and the couch in computed tomography: a phantom study.

The purpose of this study was to investigate the risk of overexposure associated with automatic tube current modulation (ATCM) and automatic couch height positioning compensation mechanism (AHC) in computed tomography (CT) systems, particularly in scenarios involving a gap between the subject and the couch. Results revealed that when AHC was enabled, CT dose index volume (CTDIvol) increased by approximately 10% at 2.5 cm, 20% at 5.0 cm, and 40% at 10.0 cm gaps compared to close contact conditions. While the AHC function ensures consistent exposure doses and image quality regardless of subject positioning relative to the CT gantry isocenter, the study highlights a potential risk of overexposure when a gap exists between the subject and the couch. These findings offer valuable insights for optimizing CT imaging protocols and underscore the importance of carefully considering subject positioning in clinical practice.

Impact of beam collimation of z-overscanning on dose to the lens and thyroid gland in paediatric thoracic computed tomography imaging.

BACKGROUND: Adaptive collimation reduces the dose deposited outside the imaged volume along the z-axis. An increase in the dose deposited outside the imaged volume (to the lens and thyroid) in the z-axis direction is a concern in paediatric computed tomography (CT). OBJECTIVE: To compare the dose deposited outside the imaged volume (to the lens and thyroid) between 40-mm and 80-mm collimation during thoracic paediatric helical CT. MATERIALS AND METHODS: We used anthropomorphic phantoms of newborns and 5-year-olds with 40-mm and 80-mm collimation during helical CT. We compared the measured dose deposited outside the imaged volume using optically stimulated luminescence dosimeters (OSLD) at the surfaces of the lens and thyroid and the image noise between the 40-mm and 80-mm collimations. RESULTS: There were significant differences in the dose deposited outside the imaged volume (to the lens and thyroid) between the 40-mm and 80-mm collimations for both phantoms (P < 0.01). CONCLUSION: Compared with that observed for 80-mm collimation in helical CT scans of the paediatric thorax, the dose deposited outside the imaged volume (to the lens and thyroid) was significantly lower in newborns and 5-year-olds with 40-mm collimation.

Cardiac computed tomography angiography with and without bolus tracking methods in infants with congenital heart disease.

The study investigated radiation dose, vascular computed tomography (CT) enhancement and image quality of cardiac computed tomography angiography (CCTA) with and without bolus tracking (BT) methods in infants with congenital heart disease (CHD). The volume CT dose index (CTDIvol) and dose length product (DLP) were recorded for all CT scans, and the effective dose was obtained using a conversion factors. The CT number for the ascending aorta (AO) and pulmonary artery (PA), image noise of muscle tissue and contrast-to-noise ratio (CNR) were measured and calculated. The median values in the groups with and without BT were 2.20 mGy versus 0.44 mGy for CTDIvol, 8.10 mGy·cm versus 6.20 mGy·cm for DLP, and 0.66 mSv versus 0.51 mSv for effective dose (p < 0.001). There were no statistical differences in vascular CT enhancement, image noise, and CNR. CCTA without BT methods can reduce the radiation dose while maintaining vascular CT enhancement and image quality compared to CCTA with BT methods.

The Feasibility of Using a Deep Learning-Based Model to Determine Cardiac Computed Tomographic Contrast Dose.

PURPOSE: This study aimed to predict contrast effects in cardiac computed tomography (CT) from CT localizer radiographs using a deep learning (DL) model and to compare the prediction performance of the DL model with that of conventional models based on patients' physical size. METHODS: This retrospective study included 473 (256 men and 217 women) cardiac CT scans between May 2014 and August 2017. We developed and evaluated DL models that predict milligrams of iodine per enhancement of the aorta from CT localizer radiographs. To assess the model performance, we calculated and compared Pearson correlation coefficient ( r ) between the actual iodine dose that was necessary to obtain a contrast effect of 1 HU (iodine dose per contrast effect [IDCE]) and IDCE predicted by DL, body weight, lean body weight, and body surface area of patients. RESULTS: The model was tested on 52 cases for the male group (mean [SD] age, 63.7 ± 11.4) and 44 cases for the female group (mean [SD] age, 69.8 ± 11.6). Correlation coefficients between the actual and predicted IDCE were 0.607 for the male group and 0.412 for the female group, which were higher than the correlation coefficients between the actual IDCE and body weight (0.539 for male, 0.290 for female), lean body weight (0.563 for male, 0.352 for female), and body surface area (0.587 for male, 0.349 for female). CONCLUSIONS: The performance for predicting contrast effects by analyzing CT localizer radiographs with the DL model was at least comparable with conventional methods using the patient's body size, notwithstanding that no additional measurements other than CT localizer radiographs were required.

Effectiveness of low tube voltage scan in the exposure dose for lenses during paediatric thoracic CT examination: anthropomorphic phantoms study.

To determine whether using lower-tube voltage reduces the scattered dose for the lens during paediatric thoracic computed tomography (CT). Two paediatric anthropomorphic phantoms (ATOM Phantom, CIRS, Norfolk, Virginia, USA) representing a newborn and 5-year-old were placed on the gantry of CT scanner, and optically stimulated luminescence dosemeters were placed on the left and right lenses, in front of the left and right thyroid glands, in front of the left and right mammary glands, and in front of and behind the mammary gland level and we measured scattered dose of the optically stimulated luminescence dosemeter was compared for each phantom between 80 and 120 kVp. Significant differences were observed in the scatter doses for the lens between 80 and 120 kVp (p < 0.01). Compared with the 120 kVp scan, the scatter doses for the lens were ~15-40% lower in newborn and 5-year-olds using the 80 kVp scan during paediatric CT.

[Investigation of the Correlation between Patient Characteristics and Contrast Enhancement during Hepatic Dynamic CT Scan: Comparison by the Sex].

The purpose of this study was to investigate the correlation between patient characteristics and contrast enhancement during the hepatic arterial phase (HAP) and portal venous phase (PVP) CT scanning. All were examined using a hepatic dynamic CT protocol; the scanning parameters were tube voltage 120 kVp, tube current 50 to 600 mA (noise index 8.0 HU), 0.5-s rotation, 5-mm detector row width, 0.813 or 0.825 beam pitch, and the contrast material 600 mg/kg iodine. We calculated contrast enhancement (per gram of iodine: ΔHU/gI) of the abdominal aorta during the HAP and that of the hepatic parenchyma during the PVP. There was a significant difference in the contrast enhancement of the abdominal aorta during the HAP (8.6±2.7 ΔHU/gI) and (9.5±1.7 ΔHU/gI) and that of the hepatic parenchyma during the PVP (1.4±0.5 ΔHU/gI) and (2.9±0.5 ΔHU/gI) between male and female patients (p<0.05). A significant positive correlation was seen between the ΔHU/gI of aortic enhancement and age in male and female patients (r=-0.382 and 0.213) (p<0.05). A significant inverse correlation was observed between the ΔHU/gI of aortic enhancement and the height (HT; r=-0.466 and -0.251), total body weight (TBW; r=-0.609 and -0.535), body mass index (BMI; r=-0.505 and -0.465), lean body weight (LBW; r=-0.642 and -0.576), and body surface area (BSA; r=-0.644 and -0.557) (p<0.05 for all) in male and female patients. A significant positive correlation was seen between the ΔHU/gI of hepatic parenchymal enhancement and the patient age in male and female patients (r=0.258 and 0.150) (p<0.05). A significant inverse correlation was observed between the ΔHU/gI of hepatic parenchymal enhancement and the HT (r=-0.487 and -0.321), TBW (r=-0.580 and -0.525), BMI (r=-0.473 and -0.413), LBW (r=-0.615 and -0.576) (p<0.05 for all), and BSA (r=-0.617 and -0.558) in male and female patients. The BSA was significantly correlated with the ΔHU/gI of aortic and hepatic parenchymal enhancement of the hepatic dynamic CT in male patients. However, LBW was significantly correlated with the ΔHU/gI of aortic and hepatic parenchymal enhancement of the hepatic dynamic CT in female patients. Since the patient factors that affect the contrast enhancement of the abdominal aorta and hepatic parenchyma may differ from facility to facility, we should therefore consider reassessing at each facility.

Utility of lower tube voltage scans in reducing exposure of healthcare workers within computed tomography room to scattered radiation.

The aim of this study was to estimate the effect of tube voltage on the scattered dose in a computed tomography (CT) room. To this end, we conducted experiments using anthropomorphic phantoms and a CT scanner at different tube voltages during CT. The scattered dose was measured using an electronic pocket dosemeter at 50-cm intervals from the centre of the gantry. The structure of the CT room was measured at 57 points (28 points in the front of the gantry (on the bed side), 6 points on the side of the gantry and 23 points behind the gantry) to be up to 200 cm. We compared the scattered dose distributions between 80 and 120 kVp at heights of 50, 100 and 150 cm above the floor surface. The scattered dose was reduced by ~30% when the tube voltage was reduced from 120 to 80 kVp.

Optimization of wrist tendon detection in virtual monochromatic images using dual energy-computed tomography.

OBJECTIVES: To evaluate the depiction of wrist tendons in virtual monochromatic images (VMIs) during a dual-energy CT (DE-CT) with the VMI image of conventional equivalent to 120 kVp. MATERIALS AND METHODS: Using Catphan600 and phantom analysis software for CT evaluation, measurements of VMI in a DE-CT were performed corresponding to the tube voltages of single-energy CT at 120 kVp. Using a Discovery CT750 HD CT scanner (GE Healthcare) with DE-CT technology, 73 patients were scanned. We calculated the CT number, image noise, visual score, and contrast noise ratio (CNR) at the extensor pollicis tendon, extensor digitorum tendon, and flexor tendon in 11 VMIs from the DE-CT and VMI image of conventional equivalent to 120 kVp. The results from the optimal VMIs were then compared with that of the VMI image of the conventional equivalent to 120 kVp. RESULTS: The highest CT number and CNR for the tendon were for the 140 keV VMI in the DE-CT compared to the other energy levels. There were significantly higher CT numbers, CNR values, and visual scores for each tendon at 140 keV VMI with the DE-CT (p < 0.01) compared with a VMI image of conventional equivalent to 120 kVp. CONCLUSION: Energy level of the VMIs during DE-CT for the best wrist tendon delineation was 140 keV. This value of 140 keV for the DE-CT was significantly higher than the CT number and CNR for the extensor pollicis, extensor digitorum, and flexor tendon compared with a VMI image of conventional equivalent to 120 kVp.

Usefulness of electrocardiogram mA modulation during the electrocardiogram-gated CT scan in paediatrics with high heart rate for different helical pitch: a phantom-based assessment study.

We investigated the effect of electrocardiographic (ECG) mA-modulation of ECG-gated scans of computed tomography (CTA) on radiation dose and image noise at high heart rates (HR) above 100 bpm between helical pitches (HP) 0.16 and 0.24. ECG mA-modulation range during ECG-gated CTA is 50-100 mA, the phase setting is 40-60% and the scan range is 90 mm for clinical data during HR for 90, 120 and 150 bpm. Radiation dose and image noise in Housfield units are measured for CT equipment during HR for 90, 120 and 150 bpm between HP 0.16 and 0.24. ECG mA-modulation, dose reduction ratio for HR 90, 120 and 150 bpm are 19.1, 13.4 and 8.7% at HP 0.16 and 17.1, 13.3 and 7.7% at HP 0.24, respectively. No significant differences were observed in image noise between both HP. Dose reductions of 8-24% are achieved with ECG mA-modulation during ECG-gated CCTA scan, which is beneficial even in high HR more than 100 bpm.

Can Machine Learning Identify the Intravenous Contrast Dose and Injection Rate Needed for Optimal Enhancement on Dynamic Liver Computed Tomography?

OBJECTIVES: This study aimed to investigate whether machine learning (ML) is useful for predicting the contrast material (CM) dose required to obtain a clinically optimal contrast enhancement in hepatic dynamic computed tomography (CT). METHODS: We trained and evaluated ensemble ML regressors to predict the CM doses needed for optimal enhancement in hepatic dynamic CT using 236 patients for a training data set and 94 patients for a test data set. After the ML training, we randomly divided using the ML-based (n = 100) and the body weight (BW)-based protocols (n = 100) by the prospective trial. The BW protocol was performed using routine protocol (600 mg/kg of iodine) by the prospective trial. The CT numbers of the abdominal aorta and hepatic parenchyma, CM dose, and injection rate were compared between each protocol using the paired t test. Equivalence tests were performed with equivalent margins of 100 and 20 Hounsfield units for the aorta and liver, respectively. RESULTS: The CM dose and injection rate for the ML and BW protocols were 112.3 mL and 3.7 mL/s, and 118.0 mL and 3.9 mL/s ( P < 0.05). There were no significant differences in the CT numbers of the abdominal aorta and hepatic parenchyma between the 2 protocols ( P = 0.20 and 0.45). The 95% confidence interval for the difference in the CT number of the abdominal aorta and hepatic parenchyma between 2 protocols was within the range of predetermined equivalence margins. CONCLUSIONS: Machine learning is useful for predicting the CM dose and injection rate required to obtain the optimal clinical contrast enhancement for hepatic dynamic CT without reducing the CT number of the abdominal aorta and hepatic parenchyma.

PATIENT DOSIMETRY SURVEY OF PEDIATRIC DIAGNOSTIC AND THERAPEUTIC CARDIAC CATHETERISATION IN JAPAN.

To propose reference values for air-kerma at the reference point (Ka,r), air-kerma area product (PKA), fluoroscopy time (FT) and number of cine images (CI) for four age groups in Japan, a nationwide questionnaire was posted to 132 pediatric catheterisation of certified facility in Japan, using the conventional post system, to which 43 facilities responded. For diagnostic cardiac angiography, reference values were as follows: Ka,r: 86, 102, 165 and 264 mGy; PKA: 9.3, 9.5, 16 and 34 Gy.cm2; FT: 33, 29, 26 and 30 min and CI: 1904, 1966, 2405 and 1871 images. For therapeutic cardiac angiography, reference values were as follows: Ka,r: 107, 163, 103 and 202 mGy; PKA: 7.5, 18, 7 and 24 Gy.cm2; FT: 56, 52, 42 and 30 min and CI: 3886, 3232, 2212 and 4316 images for less than 1, 1-5, 6-10 and 11-15 y, respectively. To optimal patient exposure from diagnostic and therapeutic cardiac catheterisation, it is therefore necessary to establish reference values for pediatric cardiac catheterisation examinations for four age groups.

RADIATION DOSE REDUCTION AT LOW TUBE VOLTAGE WITH CORONARY ARTERY BYPASS GRAFT COMPUTED TOMOGRAPHY ANGIOGRAPHY BASED ON THE CONTRAST NOISE RATIO INDEX.

To compare the radiation dose and diagnostic ability of the 100-kVp protocol, based on the contrast noise ratio (CNR) index, during coronary artery bypass graft (CABG) vessels with those of the 120-kVp protocol. For the 120-kVp scans (150 patients), the targeted image level was set at 25 Hounsfield units (HU) (CNR120 = iodine contrast/25 HU). For the 100-kVp scans (150 patients), the targeted noise level was set at 30 HU to obtain the same CNR as in the 120-kVp scans (i.e. using 1.2-fold higher iodine contrast, CNR100 = 1.2 × iodine contrast/(1.2 × 25 HU) = CNR120). We compared the CNRs, radiation doses, detection of CABG vessels and visualisation scores of the scans acquired at 120 and 100 kVp, respectively. At the same CNR, the 100-kVp protocol may help reduce the radiation dose by ⁓30% compared with the 120-kVp protocol, without degradation of diagnostic ability during CABG.

[Comparison of Lower Extremity Computed Tomography Angiography by Using Different Subtraction Techniques].

PURPOSE: To compare the diagnostic capabilities of orbital synchronized helical scanning at lower extremity computed tomography angiography between the Add/Sub software and the deformable image registration. METHODS: From March 2015 to December 2016, 100 dialysis patients underwent orbital synchronized lower limb CT subtraction angiography and lower limb endovascular treatment within 4 months. For the visual evaluation of blood vessels in the lower extremities, a stenosis rate of 50% or more was considered to be stenosis. It was classified into two areas: above-knee (AK) region (superficial femoral artery and popliteal artery) and below-knee (BK) region (anterior tibial artery, posterior tibial artery, and fibula artery). Considering angiography for the lower limb endovascular treatment as the golden standard, we calculated the sensitivity, specificity, positive-predictive value, negative-predictive value, and diagnostic capabilities. Receiver operating characteristic curve (ROC) analysis was performed to calculate the area under curve (AUC). RESULTS: Calcification subtraction failure was observed to be 11% in the AK region and 2% in the BK region using the Add/Sub software. The specificity, positive-predictive value, diagnostic capabilities, and AUC of the deformable image registration were lower than those of the Add/Sub software. CONCLUSIONS: Add/Sub software and deformable image registration have high diagnostic capability to remove calcification. On the other hand, the specificity and AUC of the deformable image registration were lower than those of the Add/Sub software. Also, even if the same deformable image registration is used, caution is required because the diagnostic performance varies depending on the site.

Effect of patient characteristics on vessel enhancement on arterio-venous fistula CT angiography in a retrospective cohort study.

To evaluate the effects of various patient characteristics on vessel enhancement on arterio-venous fistula (AVF) computed tomography (CT) angiography (AVF-CT angiography). A total of 127 patients with suspected or confirmed shunt stenosis and internal AVF complications were considered for inclusion in a retrospective cohort study. The tube voltage was 120 kVp, and the tube current was changed from 300 to 770 mA to maintain the image quality (noise index: 14) using automatic tube current modulation. To evaluate the effects of age, sex, body size, and scan delay on the CT number of the brachial artery or vein, we used correlation coefficients and multivariate regression analyses. There was a significant positive correlation between the CT number of the brachial artery or vein and age (R = 0.21 or 0.23, P < .01). The correlations were inverse with the height (r = -0.45 or -0.42), total body weight (r = -0.52 or -0.50), body mass index (r = -0.21 or -0.23), body surface area (body surface area [BSA]; r = -0.56 or -0.54), and lean body weight (r = -0.55 or -0.53) in linear regression analysis (P < .01 for all). There was a significant correlation between the CT number of the brachial artery or vein and scan delay (R = 0.19 or 01.9, P < .01). Only the BSA had significant effects on the CT number in multivariate regression analysis (P < .01). The BSA was significantly correlated with the CT number of the brachial artery or vein on AVF-CT angiography.

Usefulness of large beam-shaping filters at different tube voltages of newborn chest CT.

BACKGROUND: To investigate optimizing the use of different beam shaping filters (viz. small, medium and large) when using different tube voltages during the newborn chest computed tomography (CT) on a GE Lightspeed VCT scanner. METHODS: We used pediatric anthropomorphic phantoms with a 64 detector-row CT scanner while scanning the chest. A real-time skin dosimeter (RD - 1000; Trek Corporation, Kanagawa, Japan) was positioned into the phantom center of the body, the surface of the body back, and the right and left mammary glands. We performed and compared six scan protocols using small, medium, and large beam shaping filters at 80 and 120 kVp protocols. RESULT: There were no significant differences in the image noise for the chest scan among the different beam shaping filters. By using the large beam shaping filter at 80 kVp, it was possible to reduce the exposure dose by 5% in comparison with the small beam shaping filter, and by 10% in comparison with the medium beam shaping filter. By using the large beam shaping filter at 120 kVp, it was possible to reduce the exposure dose by 15% in comparison with the small beam shaping filter and by 20% in comparison with the medium beam shaping filter (p < 0.01). CONCLUSION: The large beam shaping filter had the most dose reduction effect during newborn chest CT on a GE Lightspeed VCT scanner. The additional copper filtration being present in the large bowtie filter of the GE Lightspeed CT scanner when using different tube voltages is more effective in reducing radiation exposure in children.

COMPARISON OF THE 64- AND 80-DETECTOR ROW COMPUTED TOMOGRAPHY AMONG THE CT NUMBER AND RADIATION DOSE DURING LOWER EXTREMITY COMPUTED TOMOGRAPHY ANGIOGRAPHY.

To compare the computed tomography (CT) number and the radiation dose between the 64 (group A) and 80-detector row (group B) during lower extremity computed tomography angiography (LE-CTA). We enrolled 144 patients underwent LE-CTA and compared the CT number for the popliteal arteries, radiation dose and the rate of the optimal CT number during the LE-CTA exceeding 200 HU between the two groups. The CT number for the popliteal arteries and mean dose-length product was significantly higher in Group A than in Group B (P < 0.01). The rate of the optimal CT number for the popliteal arteries was 23.6% with Group B scanner and 56.9% with Group A (P < 0.05). The 64-detector row CT was significantly higher in the CT number for the popliteal arteries, radiation dose and rate of the optimal CT number during the LE-CTA than the 80-detector row. Depiction ability did not improve by using a high CT scanner with a wider detector during LE-CTA.