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.

[Validation of Optimal Imaging Conditions for Coronary Computed Tomography Angiography Using High-definition Mode and Deep Learning Image Reconstruction Algorithm].

PURPOSE: To verify the optimal imaging conditions for coronary computed tomography angiography (CCTA) examinations when using high-definition (HD) mode and deep learning image reconstruction (DLIR) in combination. METHOD: A chest phantom and an in-house phantom using 3D printer were scanned with a 256-row detector CT scanner. The scan parameters were as follows - acquisition mode: ON (HD mode) and OFF (normal resolution [NR] mode), rotation time: 0.28 s/rotation, beam coverage width: 160 mm, and the radiation dose was adjusted based on CT-AEC. Image reconstruction was performed using ASiR-V (Hybrid-IR), TrueFidelity Image (DLIR), and HD-Standard (HD mode) and Standard (NR mode) reconstruction kernels. The task-based transfer function (TTF) and noise power spectrum (NPS) were measured for image evaluation, and the detectability index (d') was calculated. Visual evaluation was also performed on an in-house coronary phantom. RESULT: The in-plane TTF was better for the HD mode than for the NR mode, while the z-axis TTF was lower for DLIR than for Hybrid-IR. The NPS values in the high-frequency region were higher for the HD mode compared to those for the NR mode, and the NPS was lower for DLIR than for Hybrid-IR. The combination of HD mode and DLIR showed the best value for in-plane d', whereas the combination of NR mode and DLIR showed the best value for z-axis d'. In the visual evaluation, the combination of NR mode and DLIR showed the best values from a noise index of 45 HU. CONCLUSION: The optimal combination of HD mode and DLIR depends on the image noise level, and the combination of NR mode and DLIR was the best imaging condition under noisy conditions.

Age estimation using post-mortem computed tomography and fetal dental radiographic findings in an early to mid-pregnancy fetus: A case report.

Parameters for body size growth are essential to evaluate the relationship between fetal growth and accurate age estimation in forensics. Size values measured postmortem are also affected by the postmortem environment. On the contrary, when using hard tissue maturation criteria, age estimation remains unaffected by the degree of fetal preservation. In Japan, a fetus dying 12 weeks after pregnancy must be reported as a stillbirth. A Japanese stillborn infant buried without reporting to the authorities underwent a forensic autopsy. The gestational age was 4-5 months, based on the mother's description. The body was not fixed, and it was macerated and flattened along the sagittal plane; therefore it was difficult to correctly measure indicators involving soft tissue. The bone size and tooth development were evaluated using postmortem computed tomography (CT) images and intraoral radiography to estimate the age. Considering all the information, including age estimation based on bone sizes referenced in a Japanese study, calcified upper central incisors, we estimated fetal gestational age for our sample as 14-17 gestational weeks finally. However, there were discrepancies between age estimations based on bone size (20-25 gestational weeks, bone radiographic imaging standards; or 4-6 gestational months, an average of the extremity-bones by a Japanese study) and tooth development (14-17 gestational weeks). Deep discussions based on multiple indices with professionals should be applied to forensic age estimation since existing methods may be based on data for different races, use other measurement tools, or apply different sample conditions even if the targets are the same.

Evaluation of the second-generation whole-heart motion correction algorithm (SSF2) used to demonstrate the aortic annulus on cardiac CT.

The main purpose of pre-transcatheter aortic valve implantation (TAVI) cardiac computed tomography (CT) for patients with severe aortic stenosis is aortic annulus measurements. However, motion artifacts present a technical challenge because they can reduce the measurement accuracy of the aortic annulus. Therefore, we applied the recently developed second-generation whole-heart motion correction algorithm (SnapShot Freeze 2.0, SSF2) to pre-TAVI cardiac CT and investigated its clinical utility by stratified analysis of the patient's heart rate during scanning. We found that SSF2 reconstruction significantly reduced aortic annulus motion artifacts and improved the image quality and measurement accuracy compared to standard reconstruction, especially in patients with high heart rate or a 40% R-R interval (systolic phase). SSF2 may contribute to improving the measurement accuracy of the aortic annulus.

Dental radiographic information of term newborn babies within the first month: Analyzing five radiographic cases along with physical attributes in Japan.

BACKGROUND: Although dental radiography is a valuable tool for age estimation in forensic anthropology and odontology, very limited radiological data are available regarding tooth development in healthy newborn babies during the first month of life. AIM: This study aimed to describe the radiological findings of tooth development in babies aged 0 days to 1 month. DESIGN: We analyzed the postmortem findings of five newborn babies with no known natural cause of death who had undergone autopsy, computed tomography (CT), and dental radiography. We estimated the gestational age for the babies aged 0 days and analyzed the condition of mandibular symphysis, existence of tooth germs, and presence or absence of calcification of the first permanent molars of all the babies. RESULTS: The calcified form of 20 deciduous teeth, tooth germs of the permanent upper and lower first molars, and non-calcified mandibular symphysis were observed in each case. However, calcification of the first permanent molar was observed in only two 1-month-old babies. CONCLUSION: The dental radiographic findings and anthropometric measurements of non-skeletonized, non-mummified term babies confirmed calcification of all the deciduous teeth and the first permanent molar at the age of 0 days and 1 month, respectively.

Usefulness of the patient-specific contrast enhancement optimizer simulation software during the whole-body computed tomography angiography.

To evaluate whether the patient-specific contrast enhancement optimizer simulation software (p-COP) is useful for predicting contrast enhancement during whole-body computed tomography angiography (WBCTA). We randomly divided the patients into two groups using a random number table. We used the contrast material (CM) injection protocol selected by p-COP in group A (n = 52). The p-COP used an algorithm including data on the individual patient's cardiac output. Group B (n = 50) was assigned to the conventional CM injection protocol based on body weight. We compared the CT number in the abdominal aorta at the celiac artery level between the two groups and classified them as acceptable (> 280 HU) and unacceptable (< 279 HU) based on the optimal CT number for the WBCTA scans. To evaluate the difference in both injection protocols, we compared the visual inspection of the images of the artery of Adamkiewicz in both protocols. The CM dosage and injection rate in group A were significantly lower than those in group B (480.8 vs. 501.1 mg I/kg and 3.1 vs. 3.3 ml/s, p < 0.05). The CT number of the abdominal aorta at the celiac level was 382.4 ± 62.3 HU in group A and 363.8 ± 71.3 HU in group B (p = 0.23). CM dosage and injection rate were positively correlated to cardiac output for group A (r = 0.80, p < 0.05) and group B (r = 0.16, p < 0.05). The number of patients with an acceptable CT number was higher in group A [46/6 (86.7%)] than in group B [43/7 (71.4%)], but not significant (p = 0.71). The visualization rate for the Adamkiewicz artery was not significantly different between groups A and B (p = 0.89). The p-COP was useful for predicting contrast enhancement during WBCTA with a lower CM dosage and a lower contrast injection rate than that based on the body weight protocol. In patients with lower cardiac output a reduction in contrast injection rate and CM dosage did not lead to a reduced imaging quality, thus particularly in this group CM dosage can be reduced by p-COP.

[New Potential Method for Optimizing the ATCM Technique in Pediatric CT Examination].

PURPOSE: To compare the radiation dose and image quality using the conventional method for performing the front and side scout view and a new method for performing the side scout view, and then correct the table height at the scan isocenter and perform the front scout view. METHODS: We retrospectively analyzed fifty-six children who had underwent computed tomography (CT) examination between June 2014 and August 2018. We divided them into two groups. The conventional method was performed in 3 steps: 1. obtain the front scout view, 2. obtain the side scout view, and 3. main scan. Without table position correction, the new method was performed in 4 steps: 1. obtain the side scout view with table position correction, 2. patient correction at the scan isocenter, 3. obtain the front scout view, and 4. main scan. We used a 64-row CT scanner (LightSpeed VCT; GE Healthcare). Scan parameters were tube voltage 80 kV, automatic tube current modulation, noise index 16, slice thickness 5 mm, rotation time 0.4 s/rot, helical pitch 1.375, and reconstruction kernel standard. We recorded the volume dose index (CTDIvol) and dose length product (DLP) on the CT console and compared the radiation dose in both groups. To evaluate the image quality in both groups, the mean standard deviation of CT number (SD value) was measured within an approximately 5-10 mm2  circular region of interest. We measured the scan length of the pediatric patient and accuracy of pediatric positioning at the CT examination. A grid was displayed on the CT axial image, taken to evaluate the error from the scan isocenter during alignment, and the error between the height of half the body thickness and the scan isocenter was recorded. RESULTS: Scan lengths were median (minimum-maximum) values of 16.2 cm (10.8-21.5 cm) and 16.8 cm (11.5-23.0 cm). There were no significant differences in the scan length between both groups (p=0.47). In the group with table position correction, median (minimum-maximum) values for CTDIvol, DLP and SD value were 0.40 mGy (0.3-0.7 mGy), 7.6 mGyï½¥cm (4.4-11.5 mGyï½¥cm), and 24.0 HU (18.3-37.5 HU), respectively. In the group without the table position correction, median (minimum-maximum) values for CTDIvol, DLP and SD value were 0.40 mGy (0.3-0.6 mGy), 7.1 mGyï½¥cm (4.2-13.8 mGyï½¥cm), and 20.3 HU (11.3-28.8 HU), respectively. There were no significant differences in the CTDIvol and DLP values between both groups (p=0.42 and p=0.44, respectively); however, there were significant differences in the SD value in both groups (p<0.01). The error for the accuracy of pediatric positioning was 0 mm (0 to 0 mm) and 10 mm (-16 to+59 mm) using the conventional and new methods (p<0.01), respectively. CONCLUSIONS: It was suggested that the optimum image could be obtained during CT scan with automatic tube current modulation by using this potential new method (1. obtain the side scout view, 2. patient correction at the scan isocenter, 3. obtain the side scout view, and 4. main scan).

[Comparison of Contrast Enhancement between Bolus-tracking and Test-bolus Methods on Coronary CT Angiography].

PURPOSE: To compare the contrast enhancement between bolus-tracking (BT) and test-bolus (TB) methods in coronary computed tomography angiography (CCTA). METHOD: We enrolled 300 patients who underwent CCTA by BT (245 mg I/kg main bolus) or TB (77.4 mg I/kg test bolus with 245 mg I/kg main bolus) methods. In group BT (n=150), scanning was started automatically 5-second after contrast enhancement exceeded a predefined threshold of 150 Hounsfield units (HU). In group TB (n=150), TB peak attenuation plus 2-second was used as a delay. We recorded the CT number in the ascending aorta and determined whether the CT number was equivalent in two groups. For the equivalence test, we adopted 70 HU as the equivalence margin. The standard deviation (SD) in the CT number and the rate of patients with an acceptable CT number were compared. We also compared total iodine dose and total dose length product (DLP). RESULT: The CT number of the ascending aorta was 437.6±68.9 HU in group BT and 438.9±69.7 HU in group TB; the 95% confidence interval for the difference between the groups was from -11.6 to 20.2 HU and within the range of the equivalence margins. The SD of the CT number and the rate of patients with acceptable CT number did not differ significantly between the two groups (p=0.857 and p=0.614, respectively). Total iodine dose in group TB was significantly higher than in group BT (p<0.001), and total DLP was not statistically significant (p=0.197). CONCLUSION: The contrast enhancement between BT and TB methods in CCTA was equivalent, and the distribution was not significantly different between the two groups.

Individual Optimization of Contrast Media Injection Protocol at Hepatic Dynamic Computed Tomography Using Patient-Specific Contrast Enhancement Optimizer.

OBJECTIVE: We developed a patient-specific contrast enhancement optimizer (p-COP) that can exploratorily calculate the contrast injection protocol required to obtain optimal enhancement at target organs using a computer simulator. Appropriate contrast media dose calculated by the p-COP may minimize interpatient enhancement variability. Our study sought to investigate the clinical utility of p-COP in hepatic dynamic computed tomography (CT). METHODS: One hundred thirty patients (74 men, 56 women; median age, 65 years) undergoing hepatic dynamic CT were randomly assigned to 1 of 2 contrast media injection protocols using a random number table. Group A (n = 65) was injected with a p-COP-determined iodine dose (developed by Higaki and Awai, Hiroshima University, Japan). In group B (n = 65), a standard protocol was used. The variability of measured CT number (SD) between the 2 groups of aortic and hepatic enhancement was compared using the F test. In the equivalence test, the equivalence margins for aortic and hepatic enhancement were set at 50 and 10 Hounsfield units (HU), respectively. The rate of patients with an acceptable aortic enhancement (250-350 HU) for the diagnosis of hypervascular liver tumors was compared using the χ test. RESULTS: The mean ± SD values of aortic and hepatic enhancement were 311.0 ± 39.9 versus 318.7 ± 56.5 and 59.0 ± 11.5 versus 58.6 ± 11.8 HU in groups A and B, respectively. Although the SD for aortic enhancement was significantly lower in group A (P = 0.006), the SD for hepatic enhancement was not significantly different (P = 0.871). The 95% confidence interval for the difference in aortic and hepatic enhancement between the 2 groups was within the range of the equivalence margins. The number of patients with acceptable aortic enhancement was significantly greater in group A than in group B (P < 0.01). CONCLUSIONS: The p-COP software reduced interpatient variability in aortic enhancement and obtained acceptable aortic enhancement at a significantly higher rate compared with the standard injection protocol for hepatic dynamic CT.

Contrast enhancement on 100- and 120 kVp hepatic CT scans at thin adults in a retrospective cohort study: Bayesian inference of the optimal enhancement probability.

PURPOSE: To assess the probability of achieving optimal contrast enhancement in 100 kVp and 120 kVp-protocol on hepatic computed tomography (CT) scans. MATERIALS AND METHODS: We enrolled 200 patients in a retrospective cohort study. Hundred patients were scanned with 120 kVp setting, and other 100 patients were scanned with 100 kVp setting. We measured the CT number in the abdominal aorta and hepatic parenchyma on unenhanced scans and hepatic arterial phase (HAP)-, and portal venous phase (PVP). The aortic enhancement at HAP and the hepatic parenchymal enhancement at PVP were compared between the two scanning protocols. Bayesian inference was used to assess the probability of achieving optimal contrast enhancement in each protocol. RESULTS: The Bayesian analysis indicated that when 100 kVp-rotocol was used, the probability of achieving optimal aortic enhancement (>280 HU) was 98.8% ±â€Š0.6%, whereas it was 88.7% ±â€Š2.5% when 120 kVp-protocol was used. Also, the probability of achieving optimal hepatic parenchymal enhancement (>50 HU) was 95.3% ±â€Š1.5%, whereas it was 64.7% ±â€Š3.8% when 120 kVp-protocol was used. CONCLUSION: Bayesian inference suggested that the post-test probability of optimal contrast enhancement at hepatic dynamic CT was lower under the 120 kVp than the 100 kVp-protocol.

Contrast Material Injection Protocol With the Dose Determined According to Lean Body Weight at Hepatic Dynamic Computed Tomography: Comparison Among Patients With Different Body Mass Indices.

OBJECTIVE: The objective of this study was to compare enhancement of the aorta and liver on hepatic dynamic computed tomography scans acquired with contrast material doses based on the lean body weight (LBW) or the total body weight (TBW). METHODS: We randomly divided 529 patients (279 men, 250 women; median age, 66 years) scheduled for hepatic dynamic computed tomography into 2 groups. The LBW patients (n = 278) were injected with 679 mg iodine/kg (men) or 762 mg iodine/kg (women). The TBW group (n = 251) was injected with 600 mg iodine/kg TBW. Each group was subdivided into the 3 classes based on the body mass index (BMI; low, normal, high). Aortic enhancement during the hepatic arterial phase and hepatic enhancement during the portal venous phase was compared. The aortic and hepatic equivalence margins were 100 and 20 Hounsfield units, respectively. RESULTS: Comparison of the median iodine dose in patients with a normal or high BMI showed that it was significantly lower under the LBW protocol than the TBW protocol (558.2 and 507.0 mg iodine/kg, P < 0.001, respectively). However, in patients with a low BMI, the LBW protocol delivered a significantly higher dose than the TBW protocol (620.7 vs 600.0 mg iodine/kg, P < 0.001). The 95% confidence interval for the difference in aortic and hepatic enhancement between the 2 protocols was within the range of the predetermined equivalence margins in all BMI subgroups. CONCLUSIONS: Contrast enhancement was equivalent under both protocols. The LBW protocol can avoid iodine overdosing, especially in patients with a high BMI.

[Usefulness of Fenestrated Catheters for i.v. Contrast Infusion Cardiac CT Angiography for Newborn Patients during the Congenital Heart Disease].

PURPOSE: A three-dimensional (3D) image from computed tomography (CT) angiography is a useful method for evaluation of complex anatomy such as congenital heart disease. However, 3D imaging requires high contrast enhancement for distinguishing between blood vessels and soft tissue. To improve the contrast enhancement, many are increasing the injection rate. However, one method is the use of fenestrated catheters, it allows use of a smaller gauge catheter for high-flow protocols. The purpose of this study was to compare the pressure of injection rate and CT number of a 24-gauge fenestrated catheter with an 22-gauge non-fenestrated catheter for i.v. contrast infusion during CT. METHODS: Between December 2014 and March 2015, 50 newborn patients were randomly divided into two protocols; 22-gauge conventional non-fenestrated catheter (24 newborn; age range 0.25-8 months, body weight 3.6±1.2 kg) and 24-gauge new fenestrated catheter (22 newborn; age range 0.25-12 months, body weight 3.3±0.9 kg). Helical scan of the heart was performed using a 64-detector CT (LightSpeed VCT, GE Healthcare) (tube voltage 80 kV; detector configuration 64×0.625 mm, rotation time 0.4 s/rot, helical pitch 1.375, preset noise index for automatic tube current modulation 40 at 0.625 mm slice thickness). RESULTS: We compared the maximum pressure of injection rate, CT number of aortic enhancement, and CT number of pulmonary artery enhancement between both protocols. The median injection rate, CT number of aortic enhancement, and CT number of pulmonary artery enhancement were 0.9 (0.5-3.4) ml/s, 455.5 (398-659) HU, and 500.0 (437-701) HU in 22-gauge conventional non-fenestrated catheter and 0.9 (0.5-2.0) ml/s, 436.5 (406-632) HU, and 479.5 (445-695) HU in the 24-gauge fenestrated catheter, respectively. There are no significantly different between a 24-gauge fenestrated catheter and 22-gauge non-fenestrated catheters at injection rate and CT number. Maximum pressure of injection rate was lower with 24-gauge non-fenestrated catheters (0.33 kg/cm2) than 22-gauge non-fenestrated catheters (0.55 kg/cm2) (p<0.01Conclusion: A 24-gauge fenestrated catheter performs similarly to an 22-gauge non-fenestrated catheter with respect to i.v. contrast infusion and aortic enhancement levels and can be placed in most subjects whose veins are deemed insufficient for an 22-gauge catheter.

Does the Tube Voltage Affect the Characterization of Coronary Plaques on 100- and 120-kVp Computed Tomography Scans.

OBJECTIVE: The aim of this study was to compare the diagnostic performance of 100- and 120-kVp coronary computed tomography (CT) angiography (CCTA) scans for the identification of coronary plaque components. METHODS: We included 116 patients with coronary plaques who underwent CCTA and integrated backscatter intravascular ultrasound studies. On 100-kVp scans, we observed 24 fibrous and 24 fatty/fibrofatty plaques; on 120-kVp scans, we noted 27 fibrous and 41 fatty/fibrofatty plaques. We compared the fibrous and the fatty/fibrofatty plaques, the CT number of the coronary lumen, and the radiation dose on scans obtained at 100 and 120 kVp. We also compared the area under the receiver operating characteristic (ROC) curve of the coronary plaques on 100- and 120-kVp scans with their ROC curves on integrated backscatter intravascular ultrasound images. RESULTS: The mean CT numbers of fatty and fatty/fibrofatty plaques were 5.71 ± 36.5 and 76.6 ± 33.7 Hounsfield units (HU), respectively, on 100-kVp scans; on 120-kVp scans, they were 13.9 ± 29.4 and 54.5 ± 22.3 HU, respectively. The CT number of the coronary lumen was 323.1 ± 81.2 HU, and the radiation dose was 563.7 ± 81.2 mGy-cm on 100-kVp scans; these values were 279.3 ± 61.8 HU and 819.1 ± 115.1 mGy-cm on 120-kVp scans. The results of ROC curve analysis identified 30.5 HU as the optimal diagnostic cutoff value for 100-kVp scans (area under the curve = 0.93, 95% confidence interval = 0.87-0.99, sensitivity = 95.8%, specificity = 78.9%); for 120-kVp plaque images, the optimal cutoff was 37.4 HU (area under the curve = 0.87, 95% confidence interval = 0.79-0.96, sensitivity = 82.1%, specificity = 85.7%). CONCLUSIONS: For the discrimination of coronary plaque components, the diagnostic performance of 100- and 120-kVp CCTA scans is comparable.

Effect of Patient Characteristics on Vessel Enhancement in Pediatric Chest Computed Tomography Angiography.

INTRODUCTION: To evaluate the effect of sex, age, height, cardiac output (CO), total body weight (TBW), body surface area (BSA), and lean body weight (LBW) on vessel enhancement of the ascending aorta in pediatric chest computed tomography angiography (c-CTA). MATERIALS AND METHODS: This retrospective study received institutional review board approval; parental prior informed consent for inclusion was obtained for all patients. All 50 patients were examined using our routine protocol; iodine (600 mg/kg) was the contrast medium (CM). Unenhanced and contrast-enhanced scans were obtained. We calculated the CM volume per vessel enhancement and performed univariate and multivariate linear regression analysis of the relationship between CM volume per vessel enhancement and each of the body parameters. RESULTS: All patient characteristics were significantly related to CM volume per vessel enhancement (P < .05). Multivariate linear regression analysis revealed a significant correlation between CM volume per vessel enhancement and TBW, BSA, and LBW, but not the patient sex, age, CO, and height. The LBW model for CM volume per vessel enhancement yielded the highest determination coefficient (R2 = .913) and the lowest Akaike Information Criterion (400.324). CONCLUSIONS: Our findings support the delivery of an iodine dose adjusted to the LBW at c-CTA.

Usefulness of diluted contrast medium for test-scanning of infants scheduled for contrast-enhanced cardiovascular computed tomography angiography.

OBJECTIVE:: To compare the ability of test scans with undiluted and diluted contrast medium (CM) to predict contrast enhancement (CE) on cardiovascular CT angiography (CCTA) images of infants. METHODS:: We divided 120 consecutive infants who had undergone CCTA on a 64-MDCT scanner into two equal groups. In one group, the test bolus consisted of undiluted CM [protocol 1 (P1): injection volume = total body weight × 1.2 ml, injection time 5 s], in the other (P2) it was total body weight × 4.0 ml (CM 15%, saline 85%, injection time 16 s). CE on the test scans was recorded on a 3-point visual scale. We investigated the relation for CE in the pulmonary artery and ascending aorta between the P1 or P2 test scans and CCTA images. RESULTS:: While peak CE was observed on all test scans performed with P2, in approximately 10 % of test scans obtained under P1, peak CE was not visualized. There was a strong positive linear correlation for CE of the pulmonary artery and ascending aorta on P2 images (r = 0.61 and r = 0.63, p < 0.01); under P1 the correlation was weak (r = 0.26 and r = 0.33, p < 0.01). CONCLUSION:: Test-scanning with diluted CM revealed the optimal CE peak time and was useful for predicting CE on CCTA scans of the pulmonary artery and ascending aorta in infants with congenital heart disease. ADVANCES IN KNOWLEDGE:: Diluted test scans help to select the optimal scan parameters for the CCTA study of infants by using contrast-to-noise-based scanning.

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

OBJECTIVES: To investigate the clinical utility of our newly developed contrast enhancement optimizer (CEO) software for coronary CT angiography (CCTA). METHODS: We randomly assigned 295 patients (168 males, 127 females, median age 71 years) 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 (245 mg 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 75 Hounsfield 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. RESULTS: The iodine dose in group A was significantly smaller than that in group B (235.7 vs. 253.6 mg I/kg, p < 0.001). The CT number of the ascending aorta was 428.6 ± 55.5 HU in group A and 436.1 ± 68.7 HU in group B; the 95% confidence interval for the difference between the groups was -4.3 HU to 16.9 HU 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). CONCLUSIONS: 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. KEY POINTS: • 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.

Analysis of the anatomical features of pulmonary veins on pre-procedural cardiac CT images resulting in incomplete cryoballoon ablation for atrial fibrillation.

BACKGROUND: To investigate the anatomical features related to the failure of cryoballoon (CB) ablation for atrial fibrillation (AF) on pre-procedural CT images. METHODS: We retrospectively analyzed CT images of 100 patients with AF who had undergone a first CB ablation at our institution between June 2016 and April 2017. We measured the angle, short- and long axis length, and the area and ovality of 4 major pulmonary vein (PV) ostium on CT images. We performed logistic regression analysis to analyze the anatomical features related to the failure (incomplete CB ablation) of PV isolation. We also performed a receiver-operating characteristic (ROC) curve analysis to identify an appropriate cut-off value for anatomical features significantly associated with incomplete CB ablation. RESULTS: We analyzed 400 PVs in 100 patients [aged 64 (range, 27-82) years, 59% male]. The rate of incomplete CB ablation was significantly higher for right-than left-sided PVs (p < 0.001). The anatomical feature significantly associated with incomplete CB ablation was the angle at the right inferior PV (RIPV) (AOR: 1.17; 95% CI: 1.09-1.27, p < 0.001) and the right superior PV (RSPV) (AOR: 1.12; 95% CI: 1.01-1.23; p = 0.014). In the ROC analysis, the optimal cut-off value for RIPV and RSPV angle to discriminate an incomplete CB ablation were 40.1° and 79.7°, respectively. CONCLUSION: Our findings may help to select the appropriate ablation strategy to treat patients with AF. We show that the angle is an anatomical feature significantly related to failed CB ablation.

Development and Validation of Generalized Linear Regression Models to Predict Vessel Enhancement on Coronary CT Angiography.

Objective: We evaluated the effect of various patient characteristics and time-density curve (TDC)-factors on the test bolus-affected vessel enhancement on coronary computed tomography angiography (CCTA). We also assessed the value of generalized linear regression models (GLMs) for predicting enhancement on CCTA. Materials and Methods: We performed univariate and multivariate regression analysis to evaluate the effect of patient characteristics and to compare contrast enhancement per gram of iodine on test bolus (ΔHUTEST) and CCTA (ΔHUCCTA). We developed GLMs to predict ΔHUCCTA. GLMs including independent variables were validated with 6-fold cross-validation using the correlation coefficient and Bland-Altman analysis. Results: In multivariate analysis, only total body weight (TBW) and ΔHUTEST maintained their independent predictive value (p < 0.001). In validation analysis, the highest correlation coefficient between ΔHUCCTA and the prediction values was seen in the GLM (r = 0.75), followed by TDC (r = 0.69) and TBW (r = 0.62). The lowest Bland-Altman limit of agreement was observed with GLM-3 (mean difference, -0.0 ± 5.1 Hounsfield units/grams of iodine [HU/gI]; 95% confidence interval [CI], -10.1, 10.1), followed by ΔHUCCTA (-0.0 ± 5.9 HU/gI; 95% CI, -11.9, 11.9) and TBW (1.1 ± 6.2 HU/gI; 95% CI, -11.2, 13.4). Conclusion: We demonstrated that the patient's TBW and ΔHUTEST significantly affected contrast enhancement on CCTA images and that the combined use of clinical information and test bolus results is useful for predicting aortic enhancement.

Vessel Visibility Assessment of Low Tube Voltage Coronary Computed Tomography Angiography Determined with Contrast-to-Noise Ratio.

PURPOSE: The purpose of this study was to investigate the association of vessel visibility and radiation dose using contrast-to-noise ratio (CNR) method with low tube voltage in coronary computed tomography angiography (c-CTA). METHODS: We performed electrocardiogram-gated scan of 2.0-mm diameter simulated vessel in the center of the cardiac phantom by the use of a 64-detector CT scanner. Reference CNR was calculated from the target coronary CT number (CTnumberA; 350 Hounsfield units [HU]), epicardial fat CT number (CTnumberB; -100 HU), and target epicardial fat standard deviation (SD) number (SDB; 25 HU) at the 120 kV. We obtained the tube current at low tube voltage (100 and 80 kV) to perform the similar reference CNR at 120 kV. The full widths at half maximum from axial images were evaluated with quantitative evaluation and three types of visualizations of the vessel phantom were evaluated with the qualitative evaluations. RESULTS: CTnumberA of 100 and 80 kV were increased by 26% and 50%, respectively, compared with 120 kV (P<0.01). SDB was also increased by a similar ratio (P<0.01). CTDIvol of 100 and 80 kV were decreased by 39% and 51%, respectively, compared with 120 kV (P<0.05). There were no significant voltage differences among three tubes in quantitative and qualitative evaluations at the same CNR (P> 0.05). CONCLUSION: In this phantom study, these results show that the CNR method with low tube voltage achieves radiation dose reduction without decreasing the image quality.

[Usefulness of subtraction computed tomography angiography employing orbital synchronized helical scanning for diagnosis of lower extremity arteries with vessel wall calcification].

PURPOSE: Massive calcification complicates the diagnosis of the blood vessel lumen in computed tomography angiography (CTA) of the arteries of the lower extremities. The purpose of this study was to evaluate subtraction CTA with the use of orbital synchronized helical scanning (OS-SCTA). METHOD: Phantom study: We performed OS-SCTA and non-OSCTA of a calcified vessel phantom (ψ2.5 mm), and compared them with a non-calcified vessel phantom as the reference by full width at half maximum (FWHM) and full width at tenth maximum (FWTM) of maximum intensity projection (MIP) images. Clinical study: 58 patients with peripheral artery disease who were referred for angiography also underwent OS-SCTA. OS-SCTA was produced using MIP images. Findings were graded according to three categories: (1) stenosis greater than 50% or occluded; (2) stenosis less than 50%; (3) not detected due to insufficient image quality. OS-SCTA findings were compared with the angiographic findings for each arterial segment. RESULTS: In the phantom study, FWHM showed no significant difference between OS-SCTA and the reference (P=0.135), whereas FWTM showed a significant difference (P<0.001). FWHM and FWTM showed a significant difference between non-OS-SCTA and the reference (P<0.001), due to misregistration with helical artifacts. In a clinical study comparing OS-SCTA with angiography, the sensitivity and specificity were 93.3% and 95.1% in calcified segments, 91.8% and 93.9% in non-calcified segments, and 92.2% and 94.6% in all segments. There was no significant difference between calcified segments and non-calcified segments (sensitivity: P=0.568, specificity: P=0.549). CONCLUSION: OS-SCTA is beneficial for the diagnosis of lower extremity arteries with vessel wall calcification, since it shows detection accuracy comparable to that of angiography.