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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.
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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.
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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.
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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 .
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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.
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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.
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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.
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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.
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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.
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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.