The Feasibility of a Model-Based Iterative Reconstruction Technique Tuned for the Myocardium on Myocardial Computed Tomography Late Enhancement.

OBJECTIVES: This study evaluated the feasibility of a model-based iterative reconstruction technique (MBIR) tuned for the myocardium on myocardial computed tomography late enhancement (CT-LE). METHODS: Twenty-eight patients who underwent myocardial CT-LE and late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) within 1 year were retrospectively enrolled. Myocardial CT-LE was performed using a 320-row CT with low tube voltage (80 kVp). Myocardial CT-LE images were scanned 7 min after CT angiography (CTA) without additional contrast medium. All myocardial CT-LE images were reconstructed with hybrid iterative reconstruction (HIR), conventional MBIR (MBIR_cardiac), and new MBIR tuned for the myocardium (MBIR_myo). Qualitative (5-grade scale) scores and quantitative parameters (signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]) were assessed as image quality. The sensitivity, specificity, and accuracy of myocardial CT-LE were evaluated at the segment level using an American Heart Association (AHA) 16-segment model, with LGE-MRI as a reference standard. These results were compared among the different CT image reconstructions. RESULTS: In 28 patients with 448 segments, 160 segments were diagnosed with positive by LGE-MRI. In the qualitative assessment of myocardial CT-LE, the mean image quality scores were 2.9 ± 1.2 for HIR, 3.0 ± 1.1 for MBIR_cardiac, and 4.0 ± 1.0 for MBIR_myo. MBIR_myo showed a significantly higher score than HIR (P < 0.001) and MBIR_cardiac (P = 0.018). In the quantitative image quality assessment of myocardial CT-LE, the median image SNR was 10.3 (9.1-11.1) for HIR, 10.8 (9.8-12.1) for MBIR_cardiac, and 16.8 (15.7-18.4) for MBIR_myo. The median image CNR was 3.7 (3.0-4.6) for HIR, 3.8 (3.2-5.1) for MBIR_cardiac, and 6.4 (5.0-7.7) for MBIR_myo. MBIR_myo significantly improved the SNR and CNR of CT-LE compared to HIR and MBIR_cardiac (P < 0.001). The sensitivity, specificity, and accuracy for the detection of myocardial CT-LE were 70%, 92%, and 84% for HIR; 71%, 92%, and 85% for MBIR_cardiac; and 84%, 92%, and 89% for MBIR_myo, respectively. MBIR_myo showed significantly higher image quality, sensitivity, and accuracy than the others (P < 0.05). CONCLUSIONS: MBIR tuned for myocardium improved image quality and diagnostic performance for myocardial CT-LE assessment.

Feasibility of left atrial strain assessment using cardiac computed tomography in patients with paroxysmal atrial fibrillation.

PURPOSE: To evaluate the feasibility of left atrial strain (LAS) assessment using cardiac computed tomography (CT) in patients with paroxysmal atrial fibrillation (PAF). METHODS: This retrospective single-center study included 98 patients with PAF who underwent cardiac CT and echocardiography before the first catheter ablation. LAS was analyzed using cardiac CT (CT-LAS) and speckle-tracking echocardiography (STE; STE-LAS). LA reservoir (LASr), conduit (LASc), and pump strain (LASp) were calculated by averaging LAS measured in 4- and 2-chamber views. The results were compared using Pearson's correlation coefficients, paired t-tests, and Bland-Altman analysis. Intraclass correlation coefficients (ICCs) were used to evaluate reproducibility. RESULTS: CT-LAS could be analyzed in all patients, while STE-LAS could be analyzed in 53 (54%) patients. LASr, LASc, and LASp showed significant correlations between CT- and STE-LAS: LASr, r = 0.68, p < 0.001; LASc, r = 0.47, p < 0.001; LASp, r = 0.67, p < 0.001. LASr, LASc, and LASp of CT- and STE-LAS were 23.7 ± 6.0% and 22.1 ± 6.7%, 11.1 ± 3.6% and 11.1 ± 4.1%, and 12.6 ± 4.6% and 11.0 ± 4.1%, respectively. LASr and LASp were significantly higher in CT-LAS than that in STE-LAS (p = 0.023 for LASr and p = 0.001 for LASp). CT-LAS showed excellent reproducibility. The intra- and interobserver ICCs were 0.96 to 0.99 and 0.89 to 0.90, respectively. CONCLUSION: CT-LAS was successfully analyzed in more patients than STE-LAS and was highly reproducible. The findings suggest that CT-LAS is feasible for patients with PAF.

Feasibility of Bone Mineral Density and Bone Microarchitecture Assessment Using Deep Learning With a Convolutional Neural Network.

OBJECTIVES: We evaluated the feasibility of using deep learning with a convolutional neural network for predicting bone mineral density (BMD) and bone microarchitecture from conventional computed tomography (CT) images acquired by multivendor scanners. METHODS: We enrolled 402 patients who underwent noncontrast CT examinations, including L1-L4 vertebrae, and dual-energy x-ray absorptiometry (DXA) examination. Among these, 280 patients (3360 sagittal vertebral images), 70 patients (280 sagittal vertebral images), and 52 patients (208 sagittal vertebral images) were assigned to the training data set for deep learning model development, the validation, and the test data set, respectively. Bone mineral density and the trabecular bone score (TBS), an index of bone microarchitecture, were assessed by DXA. BMDDL and TBSDL were predicted by deep learning with a convolutional neural network (ResNet50). Pearson correlation tests assessed the correlation between BMDDL and BMD, and TBSDL and TBS. The diagnostic performance of BMDDL for osteopenia/osteoporosis and that of TBSDL for bone microarchitecture impairment were evaluated using receiver operating characteristic curve analysis. RESULTS: BMDDL and BMD correlated strongly (r = 0.81, P < 0.01), whereas TBSDL and TBS correlated moderately (r = 0.54, P < 0.01). The sensitivity and specificity of BMDDL for identifying osteopenia or osteoporosis were 93% and 90%, and 100% and 94%, respectively. The sensitivity and specificity of TBSDL for identifying patients with bone microarchitecture impairment were 73% for all values. CONCLUSIONS: The BMDDL and TBSDL derived from conventional CT images could identify patients who should undergo DXA, which could be a gatekeeper tool for detecting latent osteoporosis/osteopenia or bone microarchitecture impairment.

Influence of Pitch on Surface Dose Distribution and Image Noise of Computed Tomography Scans.

This study evaluated the effect of pitch on 256-slice helical computed tomography (CT) scans. Cylindrical water phantoms (CWP) were measured using axial and helical scans with various pitch values. The surface dose distributions of CWP were measured, and reconstructed images were obtained using filtered back-projection (FBP) and iterative model reconstruction (IMR). The image noise in each reconstructed image was decomposed into a baseline component and another component that varied along the z-axis. The baseline component of the image noise was highest at the center of the reconstructed image and decreased toward the edges. The normalized 2D power spectra for each pitch were almost identically distributed. Furthermore, the ratios of the 2D power spectra for IMR and FBP at different pitch values were obtained. The magnitudes of the components varying along the z-axis were smallest at the center of the reconstructed image and increased toward the edge. The ratios of the 3D power spectra on the fx axis for IMR and FBP at different pitch values were obtained. The results showed that the effect of the pitch was related to the component that varied along the z-axis. Furthermore, the pitch had a smaller effect on IMR than on FBP.

Visualization of pulmonary artery intimal sarcoma by color-coded iodine map using dual-energy computed tomography.

Pulmonary artery intimal sarcomas (PAIS) are often misdiagnosed as pulmonary embolisms (PE) as their clinical findings and imaging findings are similar. However, given the clinical outcome of both diseases is different in its prognosis, accurate and rapid diagnosis is mandatory. This is a case report of a histologically-proven PAIS which was initially treated as a PE. The color-coded iodine map using dual-energy computed tomography (dual-energy CT iodine map) well reflected the distribution of the tumor consistent with 18fluoro-2-deoxyglucose-uptake region using positron emission tomography/CT. This case demonstrates the potential of using dual-energy CT iodine map to differentiate PAIS from PE. Learning objective: Use of a dual-energy computed tomography iodine map to visualize a pulmonary artery intimal sarcoma may provide useful diagnostic information.

Transvenous pacing approach for atrioventricular block in fontan - Possibility of transvenous approach by electrophysiological assessment.

In extracardiac Fontan, an epicardial pacemaker implantation has many limitations, especially given that it is highly invasive and a high-risk procedure due to repeat thoracotomy. Herein we illustrate a case with the possibility of transvenous pacing in extracardiac Fontan being less invasive and lower risk transvenous dual-chamber pacemaker implantation by electrophysiological assessment. .

Analysis of volatile nuclides' behavior in the atmosphere released due to the FDNPP accident.

The volatile nuclides, 131I, 132I, and 132Te, which were released in large quantities during the early stage of the Fukushima Dai-ichi Nuclear Power Plant accident, are the most dominant ones in determining the impact on the public and the environment. Since the behavior of these nuclides in the environment and their effects on human health differ depending on their physicochemical forms, it is necessary to understand more about the release fraction and the deposition process of each form. In this study, a behavior model was developed to calculate physical and chemical processes of organic, inorganic, and particulate 131I and 132I, and gaseous and particulate 132Te. This behavior model was used to estimate the physicochemical composition of iodine at the time of release, the 132Te/132I activity ratio at the time of release, and the dry deposition velocity of 132Te. The estimation was performed for five plumes transported during the period from March 14 to 21, 2011, and the estimated values were obtained by comparing with the values measured in previous studies. As a result of the estimation, the organic iodine fraction at the time of release was estimated to be 0.1 or less for most plumes, while a significantly higher value of 0.3 was estimated for the plume released in the night of March 14. This result implied that the possibility of formation and release of organic iodine in the liquid phase in Unit 3, which was considered to be the source of this plume. As for the 132Te/132I ratio at the time of release, it was estimated to be about 0.3-0.4 for most plumes, while it was about 1 in the plume released in the early morning of March 15, which is consistent with the release process in Unit 2 on the night of 14 and early morning of the 15. In addition, a remarkably high dry deposition velocity of 132Te was estimated in this plume, which was consistent with the existence of radiocaesium-bearing microparticles (CsMP) with a particle size of a few micrometers that had been found to be specific to this plume.

A Novel Quantitative Parameter for Static Myocardial Computed Tomography: Myocardial Perfusion Ratio to the Aorta.

We evaluated the feasibility of myocardial perfusion ratio to the aorta (MPR) in static computed tomography perfusion (CTP) for detecting myocardial perfusion abnormalities assessed by single-photon emission computed tomography (SPECT). Twenty-five patients with suspected coronary artery disease who underwent dynamic CTP and SPECT were retrospectively evaluated. CTP images scanned at a sub-optimal phase for detecting myocardial perfusion abnormalities were selected from dynamic CTP images and used as static CTP images in the present study. The diagnostic accuracy of MPR derived from static CTP was compared to those of visual assessment and conventional quantitative parameters such as myocardial CT attenuation (HU) and transmural perfusion ratio (TPR). The area under the curve of MPR (0.84; 95% confidence interval [CI], 0.76−0.90) was significantly higher than those of myocardial CT attenuation (0.73; 95% CI, 0.65−0.79) and TPR (0.76; 95% CI, 0.67−0.83) (p < 0.05). Sensitivity and specificity were 67% (95% CI, 54−77%) and 90% (95% CI, 86−92%) for visual assessment, 51% (95% CI, 39−63%) and 86% (95% CI, 82−89%) for myocardial CT attenuation, 63% (95% CI, 51−74%) and 84% (95% CI, 80−88%) for TPR, and 78% (95% CI, 66−86%) and 84% (95% CI, 80−88%) for MPR, respectively. MPR showed higher diagnostic accuracy for detecting myocardial perfusion abnormality compared with myocardial CT attenuation and TPR.

Active aneurysm thrombosis after Kawasaki disease in an adult: Insight into anticoagulation therapy.

The management of systemic artery aneurysms secondary to Kawasaki disease (KD) in adults remains a therapeutic challenge. KD guidelines recommend the use of anticoagulation therapy with warfarin in addition to antiplatelet therapy when a giant coronary aneurysm or a history of thrombosis is documented. However, long-term use of warfarin presents several concerns. This case reports acute thrombotic occlusion due to the giant arterial aneurysm in an adult KD. A surgical resection of the aneurysm was performed because of recurrent thrombotic events, despite anticoagulant therapy with warfarin. Pathological examinations revealed a layered thrombus with inflammation in the aneurysm and Factor Xa expression mainly in newly formed thrombus. This study provides an insight into the anticoagulation therapy for cardiovascular sequelae after KD. .

Clinical application of four-dimensional noise reduction filtering with a similarity algorithm in dynamic myocardial computed tomography perfusion imaging.

We aimed to evaluate the effects of four-dimensional noise reduction filtering using a similarity algorithm (4D-SF) on the image quality and hemodynamic parameter of dynamic myocardial computed tomography perfusion (CTP). Sixty-eight patients who underwent dynamic myocardial CTP for the assessment of coronary artery disease were enrolled. Dynamic CTP was performed using a 320-row CT with low tube voltage scan (80 kVp). Two different datasets of dynamic CTP were reconstructed using iterative reconstruction (IR) alone and a combination of IR and 4D-SF. Qualitative (5-grade scale) and quantitative image quality scores were assessed, and the CT-derived myocardial blood flow (CT-MBF) was quantified. These results were compared between the two different CTP images. The qualitative image quality in CTP images reconstructed with IR and 4D-SF was significantly higher than that with IR alone (noise score: 4.7 vs. 3.4, p < 0.05). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in CTP images reconstructed with IR and 4D-SF were significantly higher than those with IR alone (SNR: 20.6 vs. 9.7; CNR: 7.9 vs. 3.9, respectively; p < 0.05). There was no significant difference in mean CT-MBF between the two sets of CTP images (3.01 vs. 3.03 mL/g/min, p = 0.1081). 4D-SF showed incremental value in improving image quality in combination with IR without altering CT-MBF quantification in dynamic myocardial CTP imaging with a low tube potential.

Dual-energy computed tomography for evaluation of breast cancer: value of virtual monoenergetic images reconstructed with a noise-reduced monoenergetic reconstruction algorithm.

PURPOSE: To evaluate the image quality and lesion visibility of virtual monoenergetic images (VMIs) reconstructed using a new monoenergetic reconstruction algorithm (nMERA) for evaluation of breast cancer. MATERIALS AND METHODS: Forty-two patients with 46 breast cancers who underwent 4-phasic breast contrast-enhanced computed tomography (CT) using dual-energy CT (DECT) were enrolled. We selected the peak enhancement phase of the lesion in each patient. The selected phase images were generated by 120-kVp-equivalent linear blended (M120) and monoenergetic reconstructions from 40 to 80 keV using the standard reconstruction algorithm (sMERA: 40, 50, 60, 70, 80) and nMERA (40 +, 50 +, 60 +, 70 +, 80 +). The contrast-to-noise ratio (CNR) was calculated and objectively analyzed. Two independent readers subjectively scored tumor visibility and image quality each on a 5-point scale. RESULTS: The CNR at 40 + and tumor visibility scores at 40 + and 50 + were significantly higher than those on M120. The CNR at 50 + was not significantly different from that on M120. However, the overall image quality score at 40 + was significantly lower than that at 50 + and on M120 (40 + vs M120, P < 0.0001 and 40 + vs 50 +, P = 0.0001). CONCLUSIONS: VMI reconstructed with nMERA at 50 keV is preferable for evaluation of patients with breast cancer.

Impact of Knowledge-Based Iterative Model Reconstruction on Image Quality and Hemodynamic Parameters in Dynamic Myocardial Computed Tomography Perfusion Using Low-Tube-Voltage Scan: A Feasibility Study.

OBJECTIVE: Knowledge-based iterative model reconstruction (IMR) yields diagnostically acceptable image quality in low-dose static computed tomography (CT). We aimed to evaluate the feasibility of IMR in dynamic myocardial computed tomography perfusion (CTP). METHODS: We enrolled 24 patients who underwent stress dynamic CTP using a 256-slice CT. Images were reconstructed using filtered back projection (FBP), hybrid IR, and IMR. Image quality and hemodynamic parameters were compared among three algorithms. RESULTS: Qualitative image quality and contrast-to-noise ratio were significantly higher by IMR than by FBP or hybrid IR (visual score: 4.1 vs. 3.0 and 3.5; contrast-to-noise ratio: 12.4 vs. 6.6 and 8.4; P < 0.05). No significant difference was observed among algorithms in CTP-derived myocardial blood flow (1.68 vs. 1.73 and 1.70 mL/g/min). CONCLUSIONS: The use of knowledge-based iterative model reconstruction improves image quality without altering hemodynamic parameters in low-dose dynamic CTP, compared with FBP or hybrid IR.

Incremental diagnostic value of whole-heart dynamic computed tomography perfusion imaging for detecting obstructive coronary artery disease.

BACKGROUND: This study aimed to evaluate the incremental diagnostic value of dynamic myocardial computed tomography (CT) perfusion (CTP) imaging for detecting obstructive coronary artery disease (CAD) in comparison with coronary CT angiography (CTA). METHODS: Thirty-eight patients who had undergone coronary CTA and pharmacological stress dynamic CTP before invasive coronary angiography (ICA) were selected retrospectively. Using ICA, obstructive CAD was defined as the presence of severe (≥70%) or moderate (50-69%) stenosis with fractional flow reserve (FFR) <0.75. For CT evaluations, coronary vessels with any stenosis ≥50%, ≥70% or unassessable lesions were considered significantly stenotic. Dynamic CTP was assessed quantitatively using CT-derived myocardial blood flow (CT-MBF). Receiver operating characteristic (ROC) curve analysis determined the cut-off value of CT-MBF for identifying obstructive CAD. The diagnostic performances of CTA alone and integrated CTA and CTP assessments for detecting obstructive CAD were compared. RESULTS: Using ICA and FFR, 24 of 114 vessels had obstructive CAD. The cut-off value of CT-MBF for detecting obstructive CAD was 1.26mL/g/min. The sensitivity, specificity, and positive and negative predictive values (PPV and NPV) at the vessel level were 96%, 57%, 37%, and 98% for CTA, and 83%, 93%, 77%, and 95% for integrated CTA and CTP assessment using cut-off 50% stenosis on CTA, respectively. The sensitivity, specificity, and PPV and NPV at the vessel level were 79%, 69%, 40%, and 93% for CTA, and 71%, 97%, 85%, and 93% for integrated CTA and CTP assessment using cut-off 70% stenosis on CTA, respectively. The area under the ROC curve for CTA and CTP was significantly higher than that for CTA alone (0.96 vs. 0.84, p<0.05). CONCLUSIONS: Stress dynamic myocardial CTP is feasible to detect hemodynamically obstructive CAD in patients with high pre-test likelihood and helps for improving diagnostic performance in comparison with coronary CTA alone.

Dual-Energy Computed Tomography in Patients With Small Hepatocellular Carcinoma: Utility of Noise-Reduced Monoenergetic Images for the Evaluation of Washout and Image Quality in the Equilibrium Phase.

PURPOSE: This study aimed to evaluate the utility of virtual monoenergetic images for detecting washout of small (≤2 cm) hepatocellular carcinoma (HCC) in the equilibrium phase. METHODS: We performed 120-kVp-equivalent linear-blended (M120) and monoenergetic reconstructions from 40 to 90 keV by standard (40, 50, 60, 70, 80, 90) and novel noise-reduced (nMERA: 40+, 50+, 60+, 70+, 80+, 90+) monoenergetic reconstruction algorithms. Image quality and tumor visibility of delayed washout of HCCs in the equilibrium phase were compared between standard monoenergetic reconstruction algorithm and nMERA by objective and subjective analyses. RESULTS: Contrast-to-noise ratio of the tumor at 40+ was the highest, whereas the score of tumor visibility peaked at 50+. The score of overall image quality at 40+ was significantly lower than those on all other image series, and the image quality among other image series were not significantly different. CONCLUSIONS: Virtual monoenergetic image reconstructed with nMERA 50+ was most appropriate to detect washout of small HCCs.

Two-Phase Contrast Injection Protocol for Pediatric Cardiac Computed Tomography in Children with Congenital Heart Disease.

To assess a two-phase contrast injection protocol for contrast enhancement during cardiac computed tomography (CT) in children with congenital heart disease. Forty-three children (20 boys, 23 girls) of median age 13 months (range 3 days-8.3 years) and weighing ≤ 20 kg who underwent cardiac CT using a two-phase contrast injection protocol at our institution were retrospectively identified. High-pitch spiral third-generation dual-source cardiac CT (tube voltage 70 kV) was performed with a fixed delay of 60 s after contrast injection in the order of 10 mgI/kg/s (30 s), 15 mgI/kg/s (20 s), and a saline chaser (10 s). Attenuation in the inferior vena cava (IVC), superior vena cava (SVC), right atrium (RA), right ventricle (RV), pulmonary artery (PA), left atrium (LA), left ventricle (LV), and descending aorta (AO) was compared using the Steel-Dwass and Fisher's exact tests. The median (interquartile range) attenuation in the IVC, SVC, RA, RV, PA, LA, LV, and AO was 285 (264-347) Hounsfield units (HU), 416 (370-445) HU, 368 (320-388) HU, 373 (322-417) HU, 397 (330-432) HU, 425 (373-469) HU, 435 (385-468) HU, and 437 (392-491) HU, respectively (p < 0.05, IVC vs. the other anatomic sites). There was no significant difference in diagnostic success rate for attenuation > 250 HU between the IVC (41 children, 95.3%) and the other sites (43 children, 100%). A two-phase contrast injection protocol is useful for effective contrast enhancement in pediatric cardiac CT.