Qiyong Guo

Comparisons of Image Quality and Radiation Dose Between Iterative Reconstruction and Filtered Back Projection Reconstruction Algorithms in 256-MDCT Coronary Angiography

OBJECTIVE The purpose of this study is to compare image quality and radiation dose between iterative reconstruction and filtered back projection (FBP) reconstruction algorithms in 256-MDCT coronary angiography. SUBJECTS AND METHODS One hundred nine consecutive patients were scanned with an ECG-gated helical technique using a 256-MDCT scanner. The patients in group A were scanned using the conventional tube output (120 kVp and 1000 mAs), and images were reconstructed using FBP. The other three groups were scanned with the same peak kilovoltage but with successively reduced tube current-time product, as follows: group B, 600 mAs; group C, 500 mAs; and group D, 400 mAs. Images were reconstructed using different levels of a new iterative reconstruction technique (iDose(4), Philips Healthcare). Noise, contrast-to-noise ratio, effective radiation dose, and scores of sharpness, contrast, and acceptability (where 1 indicates the worst, and 4 indicates the best) were compared between the four groups. RESULTS Noise in group A (mean [± SD], 16 ± 2 HU) was significantly higher than that in groups B (12 ± 2 HU), C (14 ± 2 HU), and D (13 ± 2 HU; p < 0.001). The contrast-to-noise ratio in groups B, C, and D was significantly higher than that in group A (p = 0.03). There were no differences in contrast, sharpness, and acceptability of images between group A and groups B and C. Using the criterion of image quality (score, 4), the receiver operating characteristic curve of dose levels and image quality acceptability established a reduction of 50% of tube output (group C) as the optimum cutoff point (area under the curve, 0.70; 95% CI, 0.57-0.82). The effective dose of group C was 55% lower than that of group A (5.5 ± 0.6 vs 12.0 ± 1.5 mSv). CONCLUSION Iterative reconstruction can provide equivalent or improved coronary image quality on coronary CT angiography, compared to routine-dose FBP reconstruction, while enabling radiation dose reductions of 55%.

The optimal dose reduction level using iterative reconstruction with prospective ECG-triggered coronary CTA using 256-slice MDCT

AIM To assess the image quality (IQ) of an iterative reconstruction (IR) technique (iDose(4)) from prospective electrocardiography (ECG)-triggered coronary computed tomography angiography (coronary CTA) on a 256-slice multi-detector CT (MDCT) scanner and determine the optimal dose reduction using IR that can provide IQ comparable to filtered back projection (FBP). METHOD AND MATERIALS 110 consecutive patients (69 men, 41 women; age: 54 ± 10 years) underwent coronary CTA on a 256-slice MDCT (Brilliance iCT, Philips Healthcare). The control group (Group A, n=21) were scanned using the conventional tube output (120 kVp, 210 mAs) and reconstructed using FBP. The other 4 groups were scanned with the same kVp but successively reduced tube output as follows: B[n=15]: 125 mAs; C[n=22]: 105 mAs; D[n=36]: 84 mAs: E[n=16]: 65 mAs) and reconstructed using IR levels of L3 (Group B), L4 (Group C) and L5 (Groups D and E), to compensate for the noise increase. All images were reconstructed using the same kernel (XCB). Two radiologists graded IQ in a blinded fashion on a 4-point scale (4 - excellent, 3 - good, 2 - fair and 1 - poor). Quantitative measurements of CT values, image noise and contrast-to-noise (CNR) were measured in each group. A receiver-operating characteristic (ROC) analysis was performed to determine a radiation reduction threshold up to which excellent IQ was maintained. RESULTS There were no significant differences in objective noise, SNR and CNR values among Groups A, B, C, D, and E (P=0.14, 0.09, 0.17, respectively). There were no significant differences in the scores of the subjective IQ between Group A, and Groups B, C, D, E (P=0.23-0.97). Significant differences in image sharpness and study acceptability were observed between groups A and E (P<0.05). Using the criterion of excellent IQ (score 4), the ROC curve of dose levels and IQ acceptability established a reduction of 60% of tube output (Group D) as optimum cutoff point (AUC: 0.72, 95% CI: 0.59-0.86). Group D (84 mAs with L5) provided equivalent subjective image ranking (with lumen sharpness taken into account) and objective IQ measurements (noise: 36.5 ± 10.7; SNR: 13.6 ± 4.9; CNR: 16.28 ± 5.4) compared with FBP images in Group A (noise: 35.5 ± 9.4; SNR: 12.4 ± 2.5; CNR: 15.4 ± 3.2) (P=0.14, 0.09, 0.17, respectively). The effective dose (ED) of Group D was 63% lower than that of Group A (1.2 ± 0.1 mSv versus 3.2 ± 0.6 mSv). CONCLUSION Iterative reconstruction techniques can provide 63% ED reduction in prospectively-triggered coronary CTA using 256-slice MDCT while maintaining excellent image quality.

Retinotopic mapping of the peripheral visual field to human visual cortex by functional magnetic resonance imaging.

Retinotopic mapping is a key property of organization in the human occipital cortex. The retinotopic organization of the central visual field of visual areas V1, V2, and V3 has been well established. We used fMRI to measure the retinotopic map of the peripheral visual field (eccentricity up to 60°). We estimated the sizes of the visual areas between 0° and 60° and obtained results consistent with anatomical studies. We also estimated the cortical distances and magnification factors for reconstruction of the retinotopic map using the peripheral wedge dipole model. By comparing the retinotopic map with the flattened surface, we analyzed the datasets used to reconstruct the map. We found that: (1) the percentage of the striate cortex devoted to peripheral vision in humans is significantly larger than that in the macaque, (2) the estimate of the scaling factor in linear magnification is larger than that found in previous studies focusing on central vision, and (3) the estimate of the peripheral factor in the dipolar model is too large to make the curve direction of the dipolar map in the periphery equivalent to that in the center. On the basis of our results, we revised the dipolar map to fit our conditions. The revised map in humans has a similar elliptical shape to that of macaques, and the central parts of the two species are the same. The different parts of the map are the peripheral regions, for which the peripheral wedge dipole model in humans is reversed compared to that of macaques. Hum Brain Mapp, 2012.

Optimizing Radiation Dose Levels in Prospectively Electrocardiogram-Triggered Coronary Computed Tomography Angiography Using Iterative Reconstruction Techniques: A Phantom and Patient Study

Aim To investigate the potential of reducing the radiation dose in prospectively electrocardiogram-triggered coronary computed tomography angiography (CCTA) while maintaining diagnostic image quality using an iterative reconstruction technique (IRT). Methods and Materials Prospectively-gated CCTA were first performed on a phantom using 256-slice multi-detector CT scanner at 120 kVp, with the tube output gradually reduced from 210 mAs (Group A) to 125, 105, 84, and 63 mAs (Group B–E). All scans were reconstructed using filtered back projection (FBP) algorithm and five IRT levels (L2-6), image quality (IQ) assessment was performed. Based on the IQ assessment, Group D(120 kVp, 84 mAs) reconstructed with L5 was found to provide IQ comparable to that of Group A with FBP. In the patient study, 21 patients underwent CCTA using 120 kV, 210 mAs with FBP reconstruction (Group 1) followed by 36 patients scanned with 120 kV, 84 mAs with IRT L5 (Group 2). Subjective and objective IQ and effective radiation dose were compared between two groups. Results In the phantom scans, there were no significant differences in image noise, contrast-to-noise ratio (CNR) and modulation transfer function (MTF) curves between Group A and the 84 mAs, 63 mAs groups (Groups D and E). Group D (120 kV, 84 mAs and L5) provided an optimum balance, producing equivalent image quality to Group A, at the lowest possible radiation dose. In the patient study, there were no significant difference in image noise, signal-to-noise ratio (SNR) and CNR between Group 1 and Group 2 (p = 0.71, 0.31, 0.5, respectively). The effective radiation dose in Group 2 was 1.21±0.14 mSv compared to 3.20±0.58 mSv (Group 1), reflecting dose savings of 62.5% (p<0.05). Conclusion iterative reconstruction technique used in prospectively ECG-triggered 256-slice coronary CTA can provide radiation dose reductions of up to 62.5% with acceptable image quality.

Comparison of tumor volume between PET and MRI in cervical cancer with hybrid PET/MR.

Objective This study aimed to compare the tumor volume between magnetic resonance imaging–defined gross tumor volume (MR-GTV) and positron emission tomography–defined GTV (PET-GTV) in cervical cancer with hybrid PET/MR. Materials and Methods Twenty-seven patients with cervical cancer underwent PET/MR pelvic examination before radiotherapy. The MR-GTV was manually outlined on T2-weighted MR images. The PET-GTV was autocontoured on PET images using a 40% maximum standardized uptake value threshold. Results were analyzed by Pearson analysis, Bland-Altman plot, and 1-way analysis of variance. Results Magnetic resonance imaging–GTV significantly correlated with PET-GTV (r2 = 0.797, P < 0.001). The Bland-Altman plot showed a bad agreement between MR-GTV and PET-GTV. The PET-GTV underestimated the MR-GTV in 23 of 27 tumors. Patients were divided into the following 3 groups according to MR-GTV: less than 14 mL (n = 6), 14 to 62 mL (n = 12), and 62 mL or more (n = 9). The mean (SD) MR-GTV, PET-GTV, ratio, and overlap between MR-GTV and PET-GTV for the less than 14 mL cohort were 9.6 (2.6) mL, 16.7 (10.1) mL, 0.77 (0.40), and 0.47 (0.20), respectively. The PET-GTV overestimated MR-GTV in 4 of the 6 lesions by a mean (SD) of 11.1 (9.4) mL. Among the 14 to 62 mL cohort, the mean (SD) MR-GTV, PET-GTV, ratio, and overlap were 38.6 (14.5) mL, 24.9 (8.6 mL), 1.54 (0.25), and 0.87 (0.08), respectively. The PET-GTV underestimated MR-GTV for 12 tumors by a mean (SD) of 13.7 (8.4) mL. In the 62 mL or more cohort, the mean (SD) MR-GTV, PET-GTV, ratio, and overlap were 85.9 (25.8) mL, 54.3 (14.1) mL, 1.61 (0.35), and 0.87 (0.09), respectively. The PET-GTV underestimated MR-GTV 9 tumors by a mean (SD) of 31.6 (19.5) mL. The ratio and overlap differences were statistically significant among groups (F = 14.619, P < 0.001; F = 25.134, P < 0.001). Conclusions Tumor volume discrepancies were observed between MR-GTV and PET-GTV for cervical cancer. With an increasing tumor volume, there was an increase in the difference between MR-GTV and PET-GTV. In addition, larger tumors had a higher degree of overlap compared with small tumors.

Value of 18F-FDG PET/CT in the diagnosis of primary gastric cancer via stomach distension

OBJECTIVE To clarify the usefulness of (18)F-FDG PET/CT for detecting primary gastric cancer via gastric distention using a mixture of milk and Diatrizoate Meglumine. MATERIALS AND METHODS A total of 68 patients (male: 47, female: 21; age: 41-87 years) suspected of gastric carcinoma underwent (18)F-FDG PET/CT imaging. After whole-body PET/CT imaging in a fasting state, the patients drank a measured amount of milk with Diatrizoate Meglumine. Local gastric district PET/CT imaging was performed 30 min later. The imaging was analyzed by semi-quantitative analysis, standardized uptake value (SUV) of the primary tumor was measured in a region of interest. The diagnosis results were confirmed by gastroscopy, pathology, and follow-up results. RESULTS Of the 68 patients, 56 malignant gastric neoplasm patients (male: 37, female: 19) were conformed. The sensitivity, specificity, positive predictive value and negative predictive value of fasting whole-body PET/CT imaging for a primary malignant tumor were 92.9%, 75.0%, 94.5%, and 69.0%, respectively. The values for distension with a mixture of milk and Diatrizoate Meglumine were 91.1%, 91.7%, 98.1%, and 68.8%, respectively. The area under the curve was 0.919 ± 0.033 and 0.883 ± 0.066 for the diagnosis of gastric cancer with SUVmax in a fasting state and after intake of mixture respectively, the differences were not statistically significant (P=0.359). Using gastric distension with a mixture of milk and Diatrizoate Meglumine, the mean ratio of the lesions SUVmax to the adjacent gastric wall SUVmax increased significantly from 3.30 ± 3.05 to 13.50 ± 15.05, which was statistically significant (P<0.001). CONCLUSIONS (18)F-FDG PET/CT imaging is highly accurate for the diagnosis of primary gastric carcinoma. Gastric distention can display the lesions more clearly, however, it cannot significantly improve diagnostic accuracy.

Assessment of memory/attention impairment in children with primary nocturnal enuresis: a voxel-based morphometry study.

AIM Assessment of memory/attention impairment and related exploration of the gray matter differential MR density variations between children with and without primary nocturnal enuresis (PNE) using voxel-based morphometry (VBM) methodology is the aim of the present study. METHODS A total of 75 right-handed PNE children (M/F=39:36, average age 10.4±1.3 years) and 72 age-matched, right-handed, healthy controls (M/F=40:32, 10.0 ± 1.2 years) were recruited for the study. First, intelligence tests were performed using the China-Wechsler Intelligence Scale for Children (C-WISC) in both PNE and control children. The full intelligence quotient (FIQ), verbal IQ (VIQ), performance IQ (PIQ), and memory/caution (M/C) factor were measured. Voxel-based morphometry (VBM) was performed using high resolution 3 Tesla T1-weighted MR images, processed using VBM5 in the PNE and control children. Students t-test or Mann-Whitney U test were performed to analyze the difference in the gray matter density (GMD) between the PNE and control children. RESULTS The FIQ, VIQ, and PIQ in the PNE group were within the normal range and did not significantly differ from the control group, though the M/C factor was statistically lower in the PNE group. Compared with normal controls, PNE children exhibited lower GMD in the right dorsolateral prefrontal cortex (DLPFC) and the left cerebellum (P<0.001). CONCLUSION Impairment in memory/attention was detected in PNE children, and the structural abnormalities of the right DLPFC and left cerebellum are likely to be implicated in these deficits.

PET/MRI with diagnostic MR sequences vs PET/CT in the detection of abdominal and pelvic cancer

OBJECTIVE Integrated positron emission tomography/magnetic resonance imaging (PET/MRI) scanners provide combined MR-based anatomic and metabolic image information. The aim of this study was to evaluate qualitative and quantitative diagnostic performance of PET/MR with (18)fluoro-2-deoxyglucose ((18)F-FDG) using a diagnostic MR sequence in patients with abdominal and pelvic tumors, compared to positron emission tomography/computed tomography (PET/CT). MATERIALS AND METHODS Forty five patients underwent a single-injection ((18)F-FDG), dual-imaging protocol including whole-body PET/CT and subsequent regional PET/MR hybrid imaging. A regional PET/MR scan followed the PET/CT. Images from both modalities were analyzed using a 3-point scale for PET/CT and PET/MR image quality, image alignment, and lesion visibility on PET images. PET-CT/PET-MR functional and anatomical correlation was analyzed. RESULTS A total of 66 lesions were studied, from which 63 were identified using PET/CT and 59 were identified using PET/MR. The (18)F-FDG PET images had good diagnostic quality (P<0.001); alignment was found to be excellent in PET/MR data as well as PET/CT data (P=0.102), and there was no difference in lesion visibility (P=0.18). The average rating score regarding anatomical correlation for PET-positive lesions was 2.75 for combined MR sequence images and 2.04 for CT, with a significant difference (P=0.317), Standard uptake value (SUV) for focal lesions had excellent correlation (SUVmax/mean: R=0.948/0.948); furthermore, the SUVmean of background organs combined, bone marrow and the muscle tissue showed good correlation (R=0.329/0.398/0.298). No correlations were found in the liver and spleen. CONCLUSIONS PET/MR with diagnostic MR sequence was able to detect abdominal and pelvic lesions and had good image quality compared to PET/CT. SUVmax and SUVmean values in focal lesions, and the SUVmean of background organs generally correlated well in abdominal and pelvic oncology patients examined using PET/CT and PET/MRI.

Aberrant Whole-Brain Functional Connectivity and Intelligence Structure in Children with Primary Nocturnal Enuresis

Aim To assess the potential relationship between intelligence structure abnormalities and whole-brain functional connectivity in children with primary nocturnal enuresis (PNE) with resting-state functional magnetic resonance imaging (fMRI) to provide insights into the association between these two seemingly unrelated conditions. Methods Intelligence testing and fMRI data were obtained from 133 right-handed children, including 67 PNE children (M/F, 39∶28; age, 10.5±1.2 y) and 66 age-matched healthy controls (M/F, 37∶29; age, 10.1±1.1 y). All intelligence tests were performed using the China-Wechsler Intelligence Scale for Children (C-WISC). Each subject’s full intelligence quotient (FIQ), verbal IQ (VIQ), performance IQ (PIQ), and memory/caution (M/C) factor was measured and recorded. Resting state fMRI scans were performed on a 3.0-T MR scanner and post-processed using REST software. Comparisons of z-score correlation coefficients between distinct cerebral regions were used to identify altered functional connectivity in PNE children. Results The PNE group had normal FIQ, VIQ, and PIQ values, indicating no significant variation from the control group. However, the M/C factor was significantly lower in the PNE group. Compared to the control group, PNE children exhibited overall lower levels of functional connectivity that were most apparent in the cerebello-thalamo-frontal pathway. The M/C factor significantly correlated with z-scores representing connectivity between Cerebellum_Crus1_L and Frontal_Mid_R. Conclusion PNE children exhibit intelligence structure imbalance and attention deficits. Our findings suggest that cerebello-thalamo-frontal circuit abnormalities are likely to be involved in the onset and progression of attention impairment in PNE children.

Potential Molecular Mechanisms for Improved Prognosis and Outcome with Neoadjuvant Chemotherapy Prior to Laparoscopical Radical Hysterectomy for Patients with Cervical Cancer

Background: The p53:miR-34a:E2F positive feed-forward loop and the p53:miR-605:Mdm2 positive feed-back loop have been identified to be crucial oncogenesis/tumor suppressor-regulating signaling pathways. In this study, we sought to examine the hypothesis that neoadjuvant chemotherapy (NAC) is a better approach with improved prognosis and outcomes after laparoscopical radical hysterectomy (LRH) on patients with cervical cancer and to elucidate the potential roles of the p53:miR-34a:E2F1 and the p53:miR-605:Mdm2 signaling pathways in this therapy. Methods: Twenty-one patients with stage IIB cervical cancer were recruited to this study and they were randomly divided into two groups: LRH (n=10) and NAC+LRH (n=11) groups. The NAC+LRH group consisted of 4 cycles of cisplatin, paclitaxel and carboplatin. Complication rates and NAC outcomes (tumor size changes, 2-year disease-free survival rate, and 2-year overall survival rate) were compared between the two groups. Expression of p53, Mdm2, E2F1, miR-34a, and miR-605 at mRNA and protein levels from the tumor tissues was analyzed. Results: We observed that the diameter of tumors following chemotherapy was substantially smaller in the NAC+LRH patients than in LRH patients. No recurrence or metastasis after surgery was observed in the NAC+LRH patients, whereas 2 out of 10 LRH patients had recurrences and 1 had metastasis. The 2-year disease-free and overall survival rates were apparently higher in the NAC+LRH group than in the LRH group. Furthermore, molecular biology analyses revealed that the protein and mRNA levels of p53 were both markedly increased in patients who received NAC than those who did not, and oppositely, the levels of E2F1 and Mdm2 were significantly lower in the NAC+LRH patients than in the LRH patients. The levels of miR-34a and miR-605 were considerably higher with NAC relative to without NAC. Among the three anti-cancer drugs included in NAC, cisplatin was found to be the main component that caused increases in p53 protein levels, miR-34a and miR-605 miRNA levels, and decreases in Mdm2 and E2F1 protein levels. Furthermore, ERK1/2 inhibitor U0126 or TAB1 siRNA mitigated these changes induced by cisplatin. Conclusion: These findings not only indicate NAC as a rational approach for better treatment of cervical cancer with improved therapeutic outcomes, due partly to the ability of cisplatin to promote the p53:miR-34a:E2F1 positive feed-forward loop and the p53:miR-605:Mdm2 positive feedback loop.