The Effects of Different Adaptive Statistical Iterative Reconstruction-V and Convolution Kernel Parameters on Auto-Segmentation Stability in CT Images / 中国医疗器械杂志

Objective The study aims to investigate the effects of different adaptive statistical iterative reconstruction-V（ ASiR-V） and convolution kernel parameters on stability of CT auto-segmentation which is based on deep learning. Method Twenty patients who have received pelvic radiotherapy were selected and different reconstruction parameters were used to establish CT images dataset. Then structures including three soft tissue organs (bladder, bowelbag, small intestine) and five bone organs (left and right femoral head, left and right femur, pelvic) were segmented automatically by deep learning neural network. Performance was evaluated by dice similarity coefficient（ DSC） and Hausdorff distance, using filter back projection(FBP) as the reference. Results Auto-segmentation of deep learning is greatly affected by ASIR-V, but less affected by convolution kernel, especially in soft tissues. Conclusion The stability of auto-segmentation is affected by parameter selection of reconstruction algorithm. In practical application, it is necessary to find a balance between image quality and segmentation quality, or improve segmentation network to enhance the stability of auto-segmentation.

Feasibility of optimizing acquisition time of 18F-FDG PET with BSREM reconstruction algorithm / 中国辐射卫生

Objective To compare the impact on 18F fluorodeoxyglucose （18F-FDG） positron emission tomography （PET） image quality when block sequential regularized expectation maximization （BSREM） algorithm and ordered subset expectation maximization （OSEM） algorithm were used at various acquisition times （ATs）, and to discuss the feasibility of AT optimization with BSREM algorithm. Methods In the phantom experiment, the NEMA/IEC PET phantom was adopted. In the clinical study, 66 pulmonary nodules with high uptake values from 61 patients who underwent a 18F-FDG PET-CT examination for pulmonary nodules from March to September 2020 were included. PET images were reconstructed according to BSREM algorithm and OSEM algorithm at various ATs in both the phantom experiment and the clinical study. Coefficient of variation, signal-to-noise ratio, contrast-to-noise ratio, and activity values （uptake value in the phantom experiment; standardized uptake value in the clinical study） were compared between the above sequence images for quality evaluation. Results The phantom experiment showed that the image quality of 120 s BSREM sequence was superior to that of 120 s OSEM sequence, and the image quality of 75 s BSREM sequence was similar to that of 120 s OSEM sequence. The clinical study showed that the image quality of 120 s BSREM sequence was superior to that of 120 s OSEM sequence, and the image quality of 75 s BSREM sequence was slightly better than that of 120 s OSEM sequence. Conclusion In the PET phantom experiment and the clinical study of pulmonary nodules with high uptake values, BSREM algorithm can significantly improve the image quality as compared to OSEM algorithm, and the image quality of 75 s BSREM sequence is slightly better than that of 120 s OSEM sequence.

Deep learning reconstruction algorithm in improving portal vein CT image quality / 西安交通大学学报(医学版)

【Objective】 To explore the value of deep learning reconstruction algorithm (DLIR) in improving image quality of portal vein. 【Methods】 We retrospectively enrolled 32 patients who underwent double-phasic enhanced abdominal CT scanning. Images at the portal venous phase were reconstructed using the 50% adaptive statistical iterative reconstruction (ASIR-V), DLIR at medium (DLIR-M) and high strength (DLIR-H). The CT value and image noise (standard deviation) of the main portal vein, the right portal vein branch, the left portal vein branch, and the paravertebral muscle were measured, and the contrast-noise-ratio (CNR) for vessels were calculated. Moreover, the edge-rising-slope (ERS) of the main portal vein edge was measured to evaluate image spatial resolution. The overall image noise, image contrast, and portal vein branch display were evaluated using a 5-point grading scale and image artifacts using a 4-point grading scare by two experienced radiologists. In addition, we calculated the display rate of small branches of the portal vein in the three reconstruction algorithms. 【Results】 Image noise of the DLIR images in the main portal vein, right branch and left branch was significantly lower than that of ASIR-V 50% images, of which the DLIR-H images had the lowest noise and highest CNR. The ERS of the DLIR images in the main portal vein was significantly higher than that of the ASIR-V 50% images. For qualitative analyses, the DLIR images were significantly better than the ASIR-V 50% ones (P<0.01). In addition, the display rates of small branches of the portal vein in DLIR images were (DLIR-M: 93.75%; DLIR-H: 100%), significantly higher than that of ASIR-V 50% (68.75%). 【Conclusion】 Compared with ASIR-V 50% images, DLIR images can significantly reduce the image noise and improve the spatial resolution of the portal vein and the display rate of small branches of the portal vein.

The application value of deep learning reconstruction algorithm in improving quality of low dose pancreatic CT images / 中华放射学杂志

Objective:To explore application value of improving quality of the low dose pancreatic CT images by using deep learning reconstruction (DLR).Methods:From August to December 2020, 68 patients who underwent contrast-enhanced pancreatic CT were prospectively collected in Peking Union Medical College Hospital. All patients were randomly divided into routine dose group (34 patients, with tube voltage of 120 kV) and low dose group (34 patients, with tube voltage of 100 kV). All patients underwent non-contrast, arterial phase, parenchymal phase and delay phase scans. The four-phase images of low dose group were reconstructed by using filtered back projection (FBP), hybrid iterative reconstruction (AIDR) and DLR which were marked with LD-FBP, LD-AIDR and LD-DLR, respectively. The four-phase images of routine dose group were reconstructed by using AIDR algorithm which were marked with RD-AIDR. The CT value, image noise (SD), signal to noise ratio (SNR) and contrast to noise ratio (CNR) of pancreas were measured. The ANOVA test was performed in comparison with objective parameters of different reconstruction algorithms, and LSD test was performed in pairwise comparison. The subjective image scores were obtained and were compared using Kruskal-Wallis test.Results:CT value, SD, SNR and CNR of non-contrast, arterial phase, parenchymal phase and delay phase had significant difference among different reconstruction images of routine dose group and low dose group (all P<0.05). The CT value of LD-FBP, LD-AIDR, and LD-DLR images were significantly higher than those of RD-AIDR images in parenchymal phase and delay phase (all P<0.05). There were statistically significant differences in each pairwise comparison of SD and SNR of four phase images (all P<0.05). There were statistically significant differences of CNR among LD-FBP, LD-DLR and RD-AIDR in four phase images (all P<0.05). The CNR of RD-AIDR was better than that of LD-FBP, and CNR of LD-DLR was better than that of RD-AIDR. DLR algorithm improved the SD, SNR and CNR of four phases of pancreatic images. The improvement of SNR was more significant after contrast enhancement, and the improvement of CNR was more significant in the non-contrast and delay phases. Subjective image scores of different reconstruction images were statistically different in four phase images (all P<0.001). Overall image scores of LD-DLR and RD-AIDR had no significant differences in four phase ( Z value of four phases were 1.00, 2.24, 0.45 and 1.34, respectively; P value of four phases were 0.317, 0.025, 0.655 and 0.180, respectively). Conclusion:The DLR technology can decrease radiation dose of pancreatic CT, improve image quality and satisfy diagnostic requirement. The DLR technology can also reduce image noise, improve the SNR and CNR in low dose contrast-enhanced pancreatic CT.

A multifrequency time-difference electrical impedance tomography algorithm using spectral constraints / 生物医学工程学杂志

This study aims to propose a multifrequency time-difference algorithm using spectral constraints. Based on the knowledge of tissue spectrum in the imaging domain, the fraction model was used in conjunction with the finite element method (FEM) to approximate a conductivity distribution. Then a frequency independent parameter (volume or area fraction change) was reconstructed which made it possible to simultaneously employ multifrequency time-difference boundary voltage data and then reduce the degrees of freedom of the reconstruction problem. Furthermore, this will alleviate the illness of the EIT inverse problem and lead to a better reconstruction result. The numerical validation results suggested that the proposed time-difference fraction reconstruction algorithm behaved better than traditional damped least squares algorithm (DLS) especially in the noise suppression capability. Moreover, under the condition of low signal-to-noise ratio, the proposed algorithm had a more obvious advantage in reconstructions of targets shape and position. This algorithm provides an efficient way to simultaneously utilize multifrequency measurement data for time-difference EIT, and leads to a more accurate reconstruction result. It may show us a new direction for the development of time-difference EIT algorithms in the case that the tissue spectrums are known.

Effect of CT image reconstruction methods on performance of pulmonary nodules detection algorithm based on deep learning / 中国医学影像技术

Objective: To explore the impact of CT image reconstruction methods on the performance of pulmonary nodule detection algorithm based on deep learning (DL). Methods: Lung CT images of 298 cases were labeled by 2 attending doctors, and the inconsistent results between them were checked by a senior doctor. The final labels were regarded as the gold standards of this experiment. Pulmonary nodule detection algorithm was constructed based on a deep neural network and tested on these 298 cases. Comparing the output of the detection algorithm with the doctor's labeling, the sensitivity, accuracy and F1-score of the algorithm were calculated, especially those under different CT image reconstruction methods. Afterwards, the false-positive detections of the algorithm were checked, and the detailed distribution of these false positives was presented. Diagnostic effects of the model were analyzed among different CT image reconstruction algorithms. Results: The sensitivity of pulmonary nodule detection algorithm under mediastinum, lung, and bone CT reconstruction methods was 92.33% (313/339), 86.97% (287/330) and 92.73% (319/344), while the precision was 23.55% (313/1 329), 37.91% (287/757) and 27.84% (319/1 146), respectively. Taken sensitivity and precision into account, F1-socre of these 3 reconstruction methods was 0.38, 0.53 and 0.43, respectively (all P>0.05). Conclusion: Pulmonary nodule detection algorithm based on DL achieves excellent performance under pulmonary window reconstruction, mediastinum window reconstruction and bone window reconstruction, which can help doctors to improve work efficiency and diagnose quality.

How Do the More Recent Reconstruction Algorithms Affect the Interpretation Criteria of PET/CT Images? / 대한핵의학회잡지

PURPOSE: Recently, a new Bayesian Penalized Likelihood (BPL) Reconstruction Algorithm was introduced by GE Healthcare, Q.Clear; it promises to provide better PET image resolution compared to the widely used Ordered Subset Expectation Maximization (OSEM). The aimof this study is to compare the performance of these two algorithms on several types of findings, in terms of image quality, lesion detectability, sensitivity, and specificity.METHODS: Between September 6th 2017 and July 31st 2018, 663 whole body 18F-FDG PET/CT scans were performed at the Nuclear Medicine Department of S. Martino Hospital (Belluno, Italy). Based on the availability of clinical/radiological follow-up data, 240 scans were retrospectively reviewed. For each scan, a hypermetabolic finding was selected, reporting both for OSEM and Q.Clear: SUVmax and SUVmean values of the finding, the liver and the background close to the finding; size of the finding; percentage variations of SUVmax and SUVmean. Each finding was subsequently correlated with clinical and radiological follow-up, to define its benign/malignant nature.RESULTS: Overall, Q.Clear improved the SUVvalues in each scan, especially in small findings (< 10mm), high SUVmax values (≥ 10), and medium/low backgrounds. Furthermore, Q.Clear amplifies the signal of hypermetabolic findings without modifying the background signal, which leads to an increase in signal-to-noise ratio, improving overall image quality. Finally, Q.Clear did not affect PET sensitivity or specificity, in terms of number of reported findings and characterization of their nature.CONCLUSIONS: Q.Clear is an iterative algorithm that improves significantly the quality of PET images compared to OSEM, increasing the SUVmax of findings (in particular for small findings) and the signal-to-noise ratio. However, due to the intrinsic characteristics of this algorithm, it will be necessary to adapt and/or modify the current interpretative criteria based of quantitative evaluation, to avoid an overestimation of the disease burden.

Feasibility of chest limit low dose CT in children / 中华放射医学与防护杂志

Objective To evaluate the feasibility of chest limit low dose CT in children using Philips iCT scanner as an example.Methods A total of 28 consecutive children aged between 1 month and 7 years(median age 8 months)who were claimed CT exam by clinicians and received limit low dose CT scans were enrolled.The limit low dose CT were undertaken on a 256-slice CT scanner(Brilliance iCT,Philips)with parameters as 80 kV,10 mAs,0.625 mm×128,and pitch＝1.Firstly,lung algorithm group and standard algorithm group 4 mm slice-thickness image series were reconstructed with lung and standard algorithm respectively using iterative reconstruction(IR)algorithm(iDose44).Then a series of 0.67 mm slice-thickness images were reconstructed with IR(iDose44)and smooth A algorithm,and was transformed into transverse 4 mm images(image transformation group)and coronal multiple planar reformatted(MPR)and volume-rendered(VR)images along the central airway.The transverse images in above three groups were displayed in the same lung window for SD measurement and subjective image quality evaluation on a 5-point scale.The dose length product(DLP)was recorded and the effective dose(E)was calculated.Results The SD values of lung algorithm group,standard algorithm group and image transformation group were 26.7 ±7.6,15.1 ±5.5 and 16.7 ±4.9,respectively,which showed statistically significant difference(F＝29.6,P＜0.05).The noise of lung algorithm group was higher than those of standard algorithm group and image transformation group(mean difference values were 11.6 and 9.6,respectively,P＜0.05),but there were no significant difference between standard algorithm group and image transformation group(P ＞0.05).All images had enough diagnostic image quality.The coronal MPR and VR images were helpful for interpretation of axial images.The mean DLP and E were(8.65 ± 2.97)mGy· cm and(0.21 ±0.10)mSv,respectively.The lowest DLP and E were 4.40 mGy· cm and 0.08 mSv,respectively.Conclusions Using Philips iCT scanner as an example,chest limit low dose CT scanning was feasible for children.Combining with IR and image transformation,the image quality was fully guaranteed and 3D images increased diagnostic confidence.

Influence on image quality in low-dose colonography with adaptive statistical iterative reconstruction algorithm / 中华放射医学与防护杂志

Objective To evaluate the feasibility of adaptive statistical iterative reconstruction-V (ASIR-V) to improve image quality in low-dose CT colonography.Methods A series of thirty artificial polyps were established by ligation in an isolated segment of porcine colon.Volume data was acquired on Revolution CT scanner (GE,USA) with High Definition scan mode and different scan parameter combinations:120 kVp with different mAs (10,30,50,70,90,100,120,140,160,180,200,220,240,260,respectively).Images were reconstructed with six different ASIR-V levels of 0 (filtered back projection,FBP),10％,30％,50％,70％ and 90％.Two radiologists were blinded to measure and analyze the objective data independently,including image noise (SD),signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).The kappa test was used to assess interobserver agreement in subjective image quality score.ICC test was used to examine the consistency of the measurements between two observers.SD,SNR,CNR were performed for statistical analysis in different tube current and different levels of ASIR-V using variance analysis (ANOVA).Results Interobserver agreement for subjective image quality score was good with a kappa value of 0.683.The variation of the tube current(r =0.734,P =0.000) and ASIR-V level(r =0.220,P =0.044) is related to the subjective score of image quality.Under the condition of the same tube current,image quality score of 50％ ASIR-V reconstruction was the highest.Two objective data consistency is good.The differences of image noise (F =423.58,P ＜ 0.05),SNRs(F =124.26,P ＜ 0.05) and CNRs (F =1 030.17,P ＜ 0.05) of different tube current and different levels of ASIR-V reconstruction were statistically significant.In the same tube current,with increased levels of ASIR-V,image noise reduced,CNRs increased.Only in 10,120,140,160,220,240,260 mA,the differences of SNRs were statistically significant(F =8.75-31.36,P ＜ 0.05).For the same level of ASIR-V reconstruction,with the increase of tube current,the image noise decreased,SNR and CNR increased gradually.Conclusions In the CT colonography,the application of ASIR-V algorithm can significantly reduce the noise and enhance the image contrast noise ratio and improve image quality.ASIR-V algorithm with 50％ has better performance in reducing CT image noise.

Setting of Noise Index in Low-dose Chest CT Examination / 中国医学影像学杂志

Purpose To explore the optimal value of noise index (NI) of adaptive statistical iterative reconstruction (ASIR) in low-dose chest examination,so as to reduce the radiation dose of patients.Materials and Methods 1200 mid-age and elderly healthy individuals were randomly divided into 4 groups according to the NI difference,with 300 in each group,group A:NI=20;group B:NI=25;group C:NI=30;group D (the normal control group):NI=14.Combined with AS IR technology,the quality of the axial image was reviewed and evaluated,and the score of each subject was given and recorded based on the quality of the image and the matching degree with the disease it indicated.Results The subjective scores of images in each group were:group A (3.53±0.43),group B (3.28±0.32),group C (3.12±0.18) and group D (5.00±0),respectively.The scores of these 4 groups were all above 3,which could be used for diagnosis.The body mass index was (24.39 ± 3.09) kg/m2,(25.49 ± 2.45) kg/m2,(25.53 ± 3.21) kg/m2 and (25.55 ± 2.28) kg/m2,respectively.The number of layers was 60.64 ± 6.38,64.42 ± 5.71,61.77 ± 6.45 and 62.32±6.15,respectively,and there was no statistically significant difference between these 4 groups (P＞0.05).The effective dose (ED) was (1.66± 0.84) mSv,(1.11 ± 0.34) mSv,(0.88±0.30) mSv and (5.99± 1.37) mSv,respectively,and the differences between any two groups were all statistically significant (P＜0.05).ED of group C was the lowest,85％ lower than group D,47％ lower than group A,and 21％ lower than group B.Conclusion Using ASIR technology,setting NI=30 can ensure that the image quality meet the needs of diagnosis,and also effectively reduce the radiation dose,which is a preferable scanning scheme.

Study on isotropic elasticity reconstruction algorithms for magnetic resonance elastography / 医疗卫生装备

Objective To analyze the advantages and disadvantages of various harmonic magnetic resonance elasticity reconstruction algorithms.Methods Different reconstruction algorithms were categorized according to their mathematical hypotheses.The influence of different assumptions on elasticity reconstruction was investigated with experiments and from mathematical fundamentals.Results The finite element full inversion method had higher precision while more computational time.The algorithms with local homogeneity and incompressibility assumptions were faster while less accurate.The algorithms considering the local change of elastic moduli could effectively reduce boundary artifacts.Conclnsion Different assumptions of algorithms may cause levels of errors between the estimated and real elastic moduli.The selection of elasticity reconstruction algorithms in practical experiment requires a comprehensive tradeoff.

Impact of reconstruction techniques on low dose chest CT image quality：comparison of FBP,iDose4 and IMR / 实用放射学杂志

Objective To investigate the impact of different reconstruction algorithms ,including filtered back projection (FBP) , hybrid iterative reconstruction technique (iDose4 ,Philips Healthcare) and iterative model reconstruction (IMR ,Philips Healthcare) on image quality of the low dose chest CT .Methods 30 consecutive patients underwent chest CT on a 256‐slice CT (80 kVp ,80 mAs) were enrolled .Raw data were reconstructed with FBP ,iDose4 ,IMR_soft (L1_Body_Soft_Tissue) and IMR_routine(L1_Body_Routine) algorithms respectively ,and reconstructed thickness was 1 mm ,increment 0 .5 mm .SD ,SNR and CNR were measured and recor‐ded .Image quality was assessed using 4‐point scale (poor to excellent) with lung and mediastinum window ,respectively .We com‐pared quantitative and qualitative parameters among three reconstructions .Results SD of four groups were 55 .7 ± 20 .7 ,37 .0 ± 13 .0 , 13 .4 ± 4 .9 and 19 .5 ± 7 .0 ,repectively .Compared with FBP group ,SD reduced by 33 .5% ,75 .9% ,65% (all ,P0 .05) .The image quality score of lung window in IMR_routine group was the highest in groups ,but was no significantly different with IMR_soft group ,and was significantly different with FBP group and iDose4 group ,respectively .The image quality score of mediastinum window in IMR_soft group was the highest in groups , but was no significantly different with IMR_routine group and was significantly different with FBP group and iDose4 group ,respec‐tively .Conclusion Compared with FBP technique ,iDose4 and IMR techniques can distinctly reduce image noise and improve image quality on low dose CT ,especially IMR algorithm .

Application of CT Scan with Iterative Reconstruction and Low Radiating Dose in Craniocerebral Trauma / 中国医学影像学杂志

PurposeTo evaluate the feasibility and clinical values of CT scan with iterative reconstruction and low radiating dose in craniocerebral trauma.Material and Methods 120 patients suffered from craniocerebral trauma were randomly assigned. All the subjects underwent CT scan using route dose of filtered back projection (FBP) and low dose of iDose (? dose and ? dose), respectively. The quartering were used to subjectively evaluate noise of imaging, skull base artifact, contrast of gyrus-white matter and lesion display in each group. Imaging noise, signal and noise rate (SNR), contrast and noise rate (CNR) of gyrus-white matter and dose length product (DLP) were compared.Results The image quality of both? iDose and ? iDose groups were lower than that of FBP group, but still met the requirement of diagnosis. The image noise of both? iDose and ? iDose groups were higher than that of FBP group (P<0.05). The SNR and CNR of both? iDose and ? iDose groups were lower than those of FBP group (P<0.05). The DLP of both? iDose and ? iDose groups were lower than that of FBP group. There was statistical difference between iDose groups and FBP group (F=2751.46,P<0.05).Conclusion Application of iDose could effectively decrease radiation dose in craniocerebral trauma. Although iDose technique has higher noise level and lower SNR and CNR, the imaging qualities and capability of displaying abnormity meet diagnosis requirement. So that iDose has clinical significance.

Image Quality of Contrast-enhanced Hepatic CT Using Iterative Reconstruction Technique at Different Radiation Doses / 中国医学影像学杂志

Purpose To compare the image quality of contrast-enhanced hepatic CT using iterative reconstruction technique (IMR) at different radiation doses, and to explore the value of IMR in contrast-enhanced hepatic CT under different radiation doses. Materials and Methods Fifty-four cases undergoing contrast-enhanced hepatic CT were divided into two groups using different portal-venous phase protocols:29 cases in group A (120 kV, 250 mAs), 25 cases in group B (80 kV, 500 mAs). Portal venous phase CT images were reconstructed using IMR and filtered back projection to obtain 4 data sets:group A1 (120 kV, FBP), group A2 (120 kV, IMR), group B1 (80 kV, FBP) and group B2 (80 kV, IMR). Images were evaluated for noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) as well as low contrast detectability (LCD), image distortion (ID) and diagnostic confidence (DC). Effective radiation dose was recorded. Results The effective radiation dose in group B was 42.7%, lower than that in group A (t=15.27, PB2>A1>B1 (χ2=58.21, PB1>A2>B2 (χ2=12.94, PA1>B2>B1 (χ2=34.06, P0.05). Conclusion Compared with FBP, IMR technique can reduce image noise and improve image quality at low and high radiation doses, with better effect on low dose (80 kV, 500 mAs) hepatic CT.

Application of Gemstone CT with Low Tube Voltage and Low Dosage Contrast Medium in Evaluating Preoperative Living Donor Renal Artery / 中国医学影像学杂志

PurposeTo explore the gemstone CT with low tube voltage and low concentration contrast medium in evaluating renal artery imaging of preoperative living renal transplantation donor.Materials and Methods Fifty cases of living kidney donor underwent spiral CT angiography of renal artery before operation. The patients were randomly divided into double-low group (25 patients) with 100 kV and Visipaque (270 mg/ml), and control group (25 patients) with 120 kV and Iopromide (370 mg/ml). Image reconstruction of 40% ASiR was used in both groups. The image quality score, CT values of renal arteries, contrast-to-noise ratio (CNR), noise, radiation dose and the amount of contrast agent of the two groups were recorded and compared.ResultsKappa coefifcient analysis showed that the consistency in evaluating image quality between two radiologists was excellent (Kappa=0.82). The CT value of the renal arteries and image quality did not show signiifcant difference between the two groups (t=1.05, 0.07 and 1.62,P>0.05). The CNR, noise and average radiation dose were statistical different between the two groups (t=2.92,-6.95 and-2.21,P<0.05). The contrast medium dosage of double-low group was decreased by 27% when compared with that of the control group.Conclusion Satisfied image quality of renal artery CTA can be obtained with low tube voltage (100 kV) and low concentration contrast medium (270 mg/ml) combined with iterative reconstruction algorithm. It can be used as a routine method in preoperative examination of living renal donors.

Application of Sinogram-afifrmed Iterative Reconstruction in Routine Dose Temporal Bone High Resolution CT / 中国医学影像学杂志

PurposeTo evaluate the impact of filtered back-projection (FBP) and sinogram-affirmed iterative reconstruction (SAFIRE) technique on the image quality of routine dose temporal bone high resolution CT (HRCT) scan, and to provide reference for the realization of low dose scanning.Materials and Methods Sixty patients underwent routine dose temporal bone HRCT scan, 6 groups of images were reconstructed with FBP and SAFIRE (strength grade 1-5), average CT value, noise (SD), signal to noise ratio (SNR), contrast to noise ratio (CNR), subjective score and lesion detection were compared between different groups.Results There was no significant difference of average CT value among the 6 groups (P>0.05); compared with FBP, SD of SAFIRE (strength 1-5) reconstruction decreased gradually (F=1.78,P<0.01), which was 23.1%, 39.2%, 42.4%, 54.1% and 61.2% respectively; SNR and CNR increased gradually (F=1.42 and 3.15, P<0.05), SNR increased 26.6%, 40%, 71.1%, 117.7% and 153.3% respectively, while CNR increased 17.4%, 33.1%, 63.2%, 104.1% and 147.2% respectively. The differences among the 6 groups were statistically significant (P<0.05), subjective scores of SAFIRE 2-4 were higher than those of FBP, SAFIRE 1 and SAFIRE 5 group, while the difference among SAFIRE 2-4 group was statistically insignificant, reconstruction smoothness and edge sharpness of SAFIRE 3 group was better, with highest objective score.Conclusion Routine dose temporal bone HRCT scan combined with SAFIRE reconstruction can increase the image quality of temporal bone high resolution scan effectively, with the potential for radiation dose reduction.

Feasibility of Dual Source CT Low Tube Voltage Combined with Iterative Reconstruction in Evaluating Coronary Artery Stents / 中国医学影像学杂志

Purpose To investigate the second generation dual source CT low tube voltage (100 kV) combined with sonogram-affirmed iterative reconstruction (SAFIRE) in assessing coronary artery stents. Materials and Methods One hundred and fifty-six patients underwent CT coronary angiography after implanted coronary artery stents. Among all the patients, 86 cases were performed with 100 kV combined with SAFIRE, and 70 cases with 120 kV combined with filtered back projection reconstruction (FBP). Mean CT values, image noise, SNR, SAIR, image quality scores, stents detecting and radiation dose of aortic root, inner-stent, and the coronary artery proximal to the stent were compared. Results The mean CT value of aortic root, inner-stent, and the coronary artery proximal to the stent of 100 kV group was higher than that of 120 kV group (t=2.75, 11.77 and 3.19, P0.05). There was no statistic difference of image quality score between the two groups (t= -0.203, P>0.05). Totally there were 243 stents detected, including 67 of right coronary artery, 123 of left anterior descending, 36 of left circumflex, and 17 of other branches. Stent length ranged 3.8 to 98.7 mm and averaged (27.5±16.4) mm. The CTDIvol, DLP and ED of 100 kV group were lower than those of 120 kV group (t= -11.03, -9.41 and -9.41, P<0.05). The effective dosage reduced about 51.5% in 100 kV group when compared with that of 120 kV group. Conclusion The second generation dual source CT low tube voltage (100 kV) combined with SAFIRE in assessing coronary artery stent could meet the diagnostic requirement and reduce the radiation dosage, without increasing image noise and beam hardening artifacts.

Iterative Reconstruction Algorithm CT Perfusion and Angiography in the Diagnosis of Ischemic Cerebrovascular Disease / 中国医学影像学杂志

Purpose To reconstruct perfusion computerized tomography angiography (PCTA) images from the volume data of low-dose brain CT perfusion scan with iterative reconstruction algorithm, to analyze the capability of PCTA on the display of brain arteries, and to explore the methods to reduce the radiation dose for stroke CT examinations. Materials and Methods This was a prospective study, 55 patients (605 arterial segments) with clinical diagnosis of ischemic cerebrovascular disease underwent cranial CT scan, iterative algorithm low-dose brain CT perfusion scan and conventional cranial CTA examinations using a 256-slice spiral CT. 11 segments of the cerebral artery in each case were analyzed using conventional CTA results as the reference standard to assess the display of brain arteries in PCTA. Results Effective dose of CT perfusion scan was 2.12 mSv. Among the 580 vessel segments which CTA showed no stenosis or stenosis0.75 for the consistency test between PCTA and CTA on the display of brain arteries. Conclusion Radiation dose of iterative algorithm cranial CT perfusion scan is significantly lower, and the images reconstructed from the volume data of perfusion CT are highly consistent with the CTA results, thus are able to meet the needs of the clinical diagnosis.

A phantom study of dose reduction potential in pelvic CT with advanced iterative reconstruction algorithms / 中华放射医学与防护杂志

Objective To assess the dose reduction potential of adaptive statistical iterative reconstruction(ASiR)and model-based iterative reconstruction(MBIR)in pelvic CT with a standard male phantom.Methods A Fluke Biomedical RANDO standard male phantom was scanned with discovery CT750 HD using different tube currents.CT images were reconstructed with FBP,50％ASiR and MBIR.The CT value,the image noise and the contrast-to-noise ratio(CNR)for the sacral vertebra relative to muscle were measured.The volume CT dose indexes(CTDIvo1)and dose-length product(DLP)were recorded.Results Compared with FBP,using 50％ASiR and MBIR had significant reduced image noise and greater CNR.The effective minimal tube currents for displaying sacral vertebra were 250 mA(FBP),180 mA(50％ASiR),and 100 mA(MBIR).With the similar image quality using FBP,the dose was reduced by 28.0％ and 59.9％ using 50％ASiR and MBIR,respectively.Conclusions Using advanced iterative algorithms can reduce image noise,improve CNR,and reduce the radiation dose in pelvic CT examination.

Reconstruction Algorithms Influence the Follow-Up Variability in the Longitudinal CT Emphysema Index Measurements

OBJECTIVE: We wanted to compare the variability in the longitudinal emphysema index (EI) measurements that were computed with standard and high resolution (HR) reconstruction algorithms (RAs). MATERIALS AND METHODS: We performed a retrospective review of 475 patients who underwent CT for surveillance of lung nodules. From this cohort, 50 patients (28 male) were included in the study. For these patients, the baseline and follow-up scans were acquired on the same multidetector CT scanner and using the same acquisition protocol. The CT scans were reconstructed with HR and standard RAs. We determined the difference in the EI between CT1 and CT2 for the HR and standard RAs, and we compared the variance of these differences. RESULTS: The mean of the variation of the total lung volume was 0.14 L (standard deviation [SD] = 0.13 L) for the standard RA and 0.16 L (SD = 0.15 L) for the HR RA. These differences were not significant. For the standard RA, the mean variation was 0.13% (SD = 0.44%) for EI -970 and 0.4% (SD = 0.88%) for EI -950; for the HR RA, the mean variation was 1.9% (SD = 2.2%) for EI -970 and 3.6% (SD = 3.7%) for EI -950. These differences were significant. CONCLUSION: Using an HR RA appears to increase the variability of the CT measurements of the EI.