Jiuhong Chen

Dose performance and image quality: Dual source CT versus single source CT in cardiac CT angiography

OBJECTIVE To evaluate dose performance and image quality of 64-slice dual source CT (DSCT) in comparison to 64-slice single source CT (SSCT) in cardiac CT angiography (CTA). METHODS 100 patients examined by DSCT and 60 patients scanned by SSCT were included in this study. Objective indices such as image noise, contrast-to-noise ratio and signal-to-noise ratio were analyzed. Subjective image quality was assessed by two cardiovascular radiologists in consensus using a four-point scale (1=excellent to 4=not acceptable). Estimation of effective dose was performed on the basis of dose length product (DLP). RESULTS At low heart rates (<70 bpm), image quality of SSCT was equivalent to that of DSCT (P>0.05), but, at high heart rates (>70 bpm), DSCT provided robust image quality (P<0.05). The average effective dose of SSCT was 9.3+/-0.9 mSv at low heart rates (<70 bpm) while, the average estimated effective doses of DSCT were 9.1+/-1.3 mSv, 8.3+/-1.1 mSv, 7.9+/-1.1 mSv, 6.9+/-0.7 mSv, and 5.9+/-1.3 mSv, corresponding to heart rates of 50-59 bpm, 60-69 bpm, 70-79 bpm, 80-89 bpm, and 90-100 bpm. CONCLUSION For cardiac CTA, both DSCT and SSCT can get good image quality at low heart rates (<70 bpm) with a similar radiation dose, but, at high heart rates (>70 bpm), DSCT is able to provide robust diagnostic image quality at doses far below that of SSCT.

Impact of Sinogram Affirmed Iterative Reconstruction (SAFIRE) Algorithm on Image Quality with 70 kVp-Tube-Voltage Dual-Source CT Angiography in Children with Congenital Heart Disease

Purpose To compare the image quality and diagnostic accuracy between sinogram affirmed iterative reconstruction (SAFIRE) algorithm and filtered back projection (FBP) reconstruction algorithm at 70 kVp-tube-voltage DSCT angiography in children with congenital heart disease (CHD). Materials and Methods Twenty-eight patients (mean age: 13 months; range: 2–48 months; male: 16; female: 12; mean weight: 8 kg) with CHD underwent 70 kVp DSCT angiography. Imaging data were reconstructed with both FBP and SAFIRE algorithms. Subjective image quality was evaluated on a five-point scale. The parameters of image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) on the objective image quality were compared for the two reconstruction algorithms. Surgery was performed in 20 patients, whereas conventional cardiac angiography (CCA) was performed in 8 patients. The diagnostic accuracy was evaluated on the surgical and/or CCA findings. The effective radiation doses were calculated. Results Compared to FBP algorithm, SAFIRE algorithm had significantly higher scores for subjective image quality (P<0.05), and lower image noise (P<0.05) as well as higher SNR &CNR values (P<0.05). There was no significant difference in the diagnostic accuracy between the FBP and SAFIRE algorithm (χ2 = 1.793, P>0.05). The mean effective dose for 70 kVp DSCT angiography was 0.30±0.13 mSv. Conclusions The SAFIRE algorithm can significantly reduce image noise and improve the image quality at 70 kVp DSCT angiography for the assessment of CHD in children.

Myocardial bridging on dual-source computed tomography: degree of systolic compression of mural coronary artery correlating with length and depth of the myocardial bridge

OBJECTIVE To investigate the correlation between the degree of systolic compression of mural coronary artery (MCA) and the length and depth of myocardial bridging (MB) with dual-source computed tomography (DSCT). METHODS The length and depth of MB were measured from diastolic phase. All datasets were reconstructed in 5% steps of R-R interval. The optimum phases were chosen where the maximal and minimal diameters were shown. The degree of systolic compression of MCA was calculated. The correlation between length and depth of MB and the degree of systolic compression of MCA were analyzed by Pearson test. RESULTS The minimal diameters were found in 27 sites (90.0%) from 30% to 35% R-R interval, and the maximal diameters were found in 27 sites (90.0%) from 70% to 80% R-R interval. The correlation between systolic compression of MCA and length of MB was not significant (r=0.096, P=.613); however, the correlation between systolic compression of MCA and the depth of MB was significant (r=0.675, P<.01). CONCLUSION The minimal and maximal diameters of MCA are usually demonstrated in 30-35% and 70-80% R-R reconstruction interval, respectively. The degree of systolic compression of MCA correlates well with the depth of MB.

Ultralow-Radiation-Dose Chest CT: Accuracy for Lung Densitometry and Emphysema Detection

OBJECTIVE The purpose of this study was to determine whether ultralow-radiation-dose chest CT can be used for quantification of lung density and for emphysema detection in participants undergoing lung cancer screening. SUBJECTS AND METHODS Fifty-two patients were prospectively enrolled and underwent scanning twice with low-dose CT (reference parameters, 120 kV, 50 effective mAs) and ultralow-dose CT (reference parameters, 80 kV, 4-5 effective mAs). Images were reconstructed by filtered back projection (FBP) for low-dose CT and FBP and iterative reconstruction (IR) for ultralow-dose CT. Radiation dose was recorded. Image noise, mean lung attenuation, 15th percentile of lung attenuation, and emphysema index were measured in each image series and compared. Test characteristics of ultralow-dose CT in detecting more than subtle emphysema (emphysema index≥3%) were calculated. RESULTS The effective dose of low-dose CT was 2.1±0.5 mSv, and that of ultralow-dose CT was 0.13±0.04 mSv. Compared with the findings for low-dose CT, absolute overestimation of emphysema index was 7% on ultralow-dose CT images reconstructed with FBP and 2% on those processed with IR. The 15th percentile of lung attenuation was underestimated by 21.3 HU on ultralow-dose FBP images and by 5.8 HU on IR images. No relevant bias was observed for mean lung attenuation. Four patients (8%) had more than subtle emphysema. The emphysema index measured at ultralow-dose CT with FBP and IR had 100% and 100% sensitivity and 92% and 96% specificity in identifying patients with more than subtle emphysema at a cutoff of greater than 12.1% for FBP and greater than 6.7% for IR. CONCLUSION Ultralow-dose chest CT performed for lung cancer screening can be used for quantification of lung density and for emphysema detection. IR improves the accuracy of ultralow-dose CT in this setting.

Assessment of thoracic aortic elasticity: a preliminary study using electrocardiographically gated dual-source CT

ObjectivesTo gain a new insight into the elastic properties of the thoracic aorta in patients without aortic diseases using electrocardiographically (ECG)-gated dual-source (DS) CT.Methods56 subjects with no cardiovascular disease, selected from 2,700 people undergoing ECG-gated DSCT examination, were divided into three groups according to their age. CT data were reconstructed in 5% step throughout the RR interval. Diameter and area were measured at the curve of the ascending aorta (AA) and at the same level of the descending aorta (DA). The pulsation and elasticity of the aorta were evaluated.ResultsAortic diameter changes were noted throughout the cardiac cycle. The maximum average diameter was seen at an RR interval of 24.02 ± 4.99% for the AA and 25.63 ± 4.77% for the DA. The minimum was at 93.5 ± 4.04% for the AA and 96.6 ± 4.58% for the DA. There was an age-dependent decrease in elasticity, while different correlation coefficients were found between various age groups and different elastic parameters.ConclusionThe properties of aortic pulsation and wall elasticity could be well shown by ECG-gated DSCT. The new findings regarding segment difference and age relevance were significant and should be taken into account in clinical trials and treatments for the elasticity related cardiovascular diseases.

Abdominal aortic intimal flap motion characterization in acute aortic dissection: assessed with retrospective ECG-gated thoracoabdominal aorta dual-source CT angiography.

Objectives To evaluate the feasibility of dose-modulated retrospective ECG-gated thoracoabdominal aorta CT angiography (CTA) assessing abdominal aortic intimal flap motion and investigate the motion characteristics of intimal flap in acute aortic dissection (AAD). Materials and Methods 49 patients who had thoracoabdominal aorta retrospective ECG-gated CTA scan were enrolled. 20 datasets were reconstructed in 5% steps between 0 and 95% of the R-R interval in each case. The aortic intimal flap motion was assessed by measuring the short axis diameters of the true lumen and false lumen 2 cm above of celiac trunk ostium in different R-R intervals. Intimal flap motion and configuration was assessed by two independent observers. Results In these 49 patients, 37 had AAD, 7 had intramural hematoma, and 5 had negative result for acute aortic disorder. 620 datasets of 31 patients who showed double lumens in abdominal aorta were enrolled in evaluating intimal flap motion. The maximum and minimum true lumen diameter were 12.2±4.1 mm (range 2.6∼17.4) and 6.7±4.1 mm (range 0∼15.3) respectively. The range of intimal flap motion in all patients was 5.5±2.6 mm (range 1.8∼10.2). The extent of maximum true lumen diameter decreased during a cardiac cycle was 49.5%±23.5% (range 12%∼100%). The maximum motion phase of true lumen diameter was in systolic phase (5%∼40% of R-R interval). Maximum and minimum intimal flap motion was at 15% and 75% of the R-R interval respectively. Intimal flap configuration had correlation with the phase of cardiac cycle. Conclusions Abdominal intimal flap position and configuration varied greatly during a cardiac cycle. Retrospective ECG-gated thoracoabdominal aorta CTA can reflect the actual status of the true lumen and provide more information about true lumen collapse. This information may be helpful to diagnosis and differential diagnosis of dynamic abstraction.

Detection and size measurements of pulmonary nodules in ultra-low-dose CT with iterative reconstruction compared to low dose CT.

BACKGROUND In this study, the accuracy of ultra-low-dose computed tomography (CT) with iterative reconstruction (IR) for detection and measurement of pulmonary nodules was evaluated. METHODS Eighty-four individuals referred for lung cancer screening (mean age: 54.5±10.8 years) underwent low-dose computed tomography (LDCT) and ultra-low-dose CT. CT examinations were performed with attenuation-based tube current modulation. Reference tube voltage and current were set to 120kV/25mÅs for LDCT and 80kV/4mÅs for ultra-low-dose CT. CT images were reconstructed with filtered back projection (FBP) for LDCT, and with FBP and IR for ultra-low-dose CT datasets. A reference standard was established by a consensus panel of 2 different radiologists on LDCT. Volume and diameter of the solid nodules were measured on LDCT with FBP and ultra-low dose CT with FBP and IR. Interobserver and interscan variability were analyzed and compared by the Bland-Altman method. RESULTS A total of 127 nodules were identified, including 105 solid nodules, 15 part solid nodules, 7 ground glass nodules. On ultra-low-dose CT scans, the effective radiation dose was 0.13±0.11mSv. A total of 113 (88.9%) and 110 (86.6%) true-positive nodules with FBP versus 117 (92.1%) and 118(92.9%) with IR were detected by two observers, respectively. The volume and size of the 105 solid nodules were measured, with mean volume/diameter of 46.5±46.6 mm(3)/5.1±1.6mm. There was no significant difference in nodule volume or diameter measurements between ultra-low-dose CT and LDCT protocols for solid nodules. CONCLUSIONS Ultra-low-dose CT with iterative reconstruction has high sensitivity for lung nodule detection without significant difference in nodule size and volume measurement compared to LDCT.

The value of low-dose prospective ECG-gated dual-source CT angiography in the diagnosis of coarctation of the aorta in infants and children

AIM To investigate the value of prospective electrocardiogram (ECG)-gated dual-source computed tomography (DSCT) in the diagnosis of coarctation of the aorta (CoA). MATERIALS AND METHODS Seventeen patients clinically suspected of having CoA underwent prospective ECG-gated DSCT angiography and transthoracic echocardiography (TTE). Surgery was performed in all patients. The diagnostic accuracy of DSCT angiography and TTE was compared with the surgical findings as the reference standard. Image quality was evaluated using a five-point scale. Effective radiation dose was calculated from the dose-length product (DLP). RESULTS CoA was diagnosed in 17 patients by DSCT angiography and in 16 patients by TTE. A total of 46 separate cardiovascular abnormalities were confirmed by surgical findings. The diagnostic accuracy of DSCT angiography and TTE was 96.32% and 97.06%, respectively. There was no significant difference in the diagnostic accuracy between DSCT angiography and TTE (χ(2) = 0, p > 0.05). The mean score of image quality was 4.2 ± 0.8. The mean effective dose was 0.69 ± 0.09 mSv. CONCLUSION Prospective ECG-gated DSCT with a low radiation dose is a valuable technique in the diagnosis of CoA in infants and children.

On simulating subjective evaluation using combined objective metrics for validation of 3D tumor segmentation

In this paper, we present a new segmentation evaluation method that can simulate radiologists subjective assessment of 3D tumor segmentation in CT images. The method uses a new metric defined as a linear combination of a set of commonly used objective metrics. The weighing parameters of the linear combination are determined by maximizing the rank correlation between radiologists subjective rating and objective measurements. Experimental results on 93 lesions demonstrate that the new composite metric shows better performance in segmentation evaluation than each individual objective metric. Also, segmentation rating using the composite metric compares well with radiologists subjective evaluation. Our method has the potential to facilitate the development of new tumor segmentation algorithms and assist large scale segmentation evaluation studies.

Functional CT in a rabbit model: Evaluation of the perfusion characteristics before and after Ar-He cryoablation therapy

The objective of this study was to investigate the perfusion characteristics of rabbit liver tumours before and after Ar‐He (argon–helium) cryoablation using functional CT and to evaluate the therapeutic effect of Ar‐He cryoablation. VX‐2 tumour was implanted into the livers of 30 New Zealand white rabbits. Two weeks after tumour implantation, Ar‐He cryoablation was performed on these rabbits. Functional CT was performed on the rabbits before and after treatment on days 1, 5, 14, 21 and 35. In the meantime, five rabbits were killed, and the livers were removed for histopathological examination at each of the time points mentioned above. Perfusion characteristics of the tumour and hot spot, such as blood flow (BF), blood volume (BV) and permeability, were analysed based on multislice CT. Histopathological studies corresponding to functional CT were observed, and the therapeutic effects (whether the tumour disappeared completely or still remained) were judged. The two‐tailed student’s t‐test was used to compare the differences between the effect of pre‐ and post‐Ar‐He cryoablation treatment on tumour perfusion parameters. After cryoablation treatment, the number of tumours exhibiting complete necrosis was 13 (52%), and their perfusion parameters, such as BF, BV and permeability values, were significantly lower than those before treatment (P < 0.05, P < 0.01 and P < 0.05, respectively). After treatment, the number of incomplete necrotic tumours was 12 (48%). In the earlier stage (within 14 days of treatment), the whole tumour perfusion parameters of BF, BV and permeability were significantly lower than those before treatment (P < 0.05). In the late stage (more than 14 days of treatment), the whole tumour perfusion parameters of BF, BV and permeability were not significantly different compared with the pretreatment results (P > 0.05). The hot spot perfusion parameters of incomplete necrotic tumours, such as BF, BV and permeability values, showed no significant differences compared with pretreatment (P > 0.05). Functional CT can measure the perfusion characteristics of hepatic tumours and is consistent with histopathological changes in the tumour after Ar‐He cryoablation. Functional CT might also be accurate in judging the therapeutic effect of Ar‐He cryoablation.