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Objective: To explore the feasibility of iterative model reconstruction (IMR) combined with 256-slice iCT low-dose scan in assessment of chronic sinusitis. Methods: Twenty patients with clinically diagnosed chronic sinusitis were examined with conventional dose CT scan and low-dose CT scan. According to dose right index (DRI) and reconstruction algorithms, CT data were divided into SD-FBP group, LD-IMR-L1 group, LD-IMR-L2 group and LD-IMR-L3 group. The volume CT dose index (CTDIvol), dose-length product (DLP) and the effective dose (ED) were recorded under different scanning schemes. The objective noise value of images were measured. The differences of image noise, artifacts and displaying of anatomical structures of ostiomeatal complex and lesions were analyzed. Results: SD-FBP group, LD-IMR-L3 group, LD-IMR-L2 group and LD-IMR-L1 group were in a descending order of image noise values. No significant difference of average noise value between LD-IMR-L3 group and SD-FBP group was found(P>0.05). The noise value of LD-IMR-L2 group and LD-IMR-L1 group were higher than that of SD-FBP group (both P0.05), which would both satisfy diagnostic requirements. The displaying of anatomical details was better in SD-FBP group groups than that in LD-IMR, but the scores in LD-IMR groups were all above 3 points and able to satisfy diagnostic requirements. CTDIvol, DLP and ED in LD-IMR groups reduced by 89.20%, 89.37% and 89.36% compared with those in SD-FBP group, respectively. Conclusion: IMR low-dose sinus CT can satisfy the requirements of displaying important bone structures of ostiomeatal complex and diagnosing chronic sinusitis with reduced ED.
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Objective To investigate the feasibility of low-dose CT perfusion imaging(CTPI)examination combined with iterative model reconstruction (IMR) in the brain.Methods 80 patients with clinical suspicion of acute cerebral infarction underwent the cerebral CTPI were enrolled in this study.30 normal hemispheres on group A [35 cases,80 kV,150 mAs, filtered back projection(FBP)] and group B(45 cases,80 kV,30 mAs, IMR) were selected to evaluate respectively.The pictures' subjective scores, effective radiation dose (ED),CT value,SD,signal to noise ratio(SNR), contrast to noise ratio(CNR) and the perfusion parameters of the grey matter (GM) and white matter(WM) in each hemisphere of the middle cerebral artery(MCA) territory were respectively compared at ASPECTS level 2 for the two groups.Results The ED were 2.52,0.50 mSv for group A,B.There were no statistical significances in the perfusion parameters,CT value, SD, CNR of the ROIs of the GM and WM,the SNR of the ROIs of the GM and the pictures' subjective scores between group A, B (P>0.05).There was statistical significance in the SNR of the ROIs of the WM between group A,B (P<0.05).Conclusion IMR combined with 30 mAs of the CTPI can reduce the radiation dose apparently while maintain the stability of the image quality and perfusion parameters.
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Objective To evaluate the application value of combination of low kV,low mAs,and iterative model reconstruction (IMR) in carotid CT angiography.Methods Forty patients (BMI 20-25 kg/m2) were enrolled and randomly divided into routine dose group(20) and low dose group(20),The parameters in routine dose group were 120 kV,automatic mAs,and filter back projection(FBP);and that in low dose group were 80 kV,automatic mAs but upper limit 150 mAs,and FBP or IMR.All patients received the injection of 32 ml of iopamidol(370 mg I/100 ml) at a flow rate of 4 ml/s,followed by 50 ml normal saline at the same rate.The CT value and image noise(SD)of the aortic arch,left carotid artery bifurcation,and right carotid artery of rock bone were measured with region of interest(ROI) method,and then signal to noise ratios (SNR) and contrast to noise ratio (CNR)of image were calculated.The image quality was evaluated by two radiologists using a subjective four points scale on multiplanar reformated (MPR),maximum density projected (MIP) and volume rendered (VR) images.Volume CT dose index (CTDIvol),dose length product (DLP),and the effective dose (E) of each patient were recorded.Results CT values of carotid artery[(479.87 ± 70.28),(514.78 ± 82.69),(436.50 ± 89.87) HU] in low dose group were significantly higher than those in routine dose group [(295.63 ± 34.75),(325.09 ± 37.81),(286.93±36.46)HU](t =-6.47,-5.76,-3.66,P＜0.05).The SNR and CNR of IMR reconstructed image in low dose group were significantly higher than those of FBP reconstructed image in routine dose group (t =-7.54,-3.55,-5.31,-7.13,-5.28,-8.35,P＜0.05).The image quality of FBP reconstructed images in routine dose group and IMR reconstructed images in low dose group were all enough for diagnosis.The image quality of FBP reconstructed images in low dose group was significantly poorer than that in routine dose group and IMR reconstructed images in low dose group (Z =-2.87,-3.69,P ＜0.05).The effective dose in low dose group (0.57 ±0.13) mSv was 73％ less than that in routine dose group (2.22 ± 0.36) mSv.Conclusions Using low kV,low mAs,and IMR would help to obtain good carotid CT angiographic images and low radiation dose.
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Objective To investigate the feasibility of low dose dual phase contrast-enhanced chest CT with iterative mod el reconstruction (IMR) technique.Methods Totally 130 patients with suspected pulmonary occupying lesions underwent dual phase contrast-enhanced chest CT,who were randomly assigned into 2 groups (group A and group B,each n=65).Patients in group A were scanned with 100 kV,DoseRight technique with dose right index 10,and images were reconstructed with the hybrid iterative reconstruction (iDose4).While patients in group B were scanned with 80 kV,DoseRight technique with dose right index 8,and images were reconstructed with iterative model reconstruction (IMR).The objective image quality,subjective image scores and the excellence rate of vascular visualization were compared in both pulmonary artery (PA) and bronchial artery (BA) phases.The radiation dose was also calculated.Results The effective dose was (3.30 ±0.89)mSv in group A and (1.27 ±0.19)mSv in group B.Compared to group A,the effective dose reduced 61.52％ in group B (P＜0.001).Lower image noise and greater CNR were obtained in group B compared to group A in both PA and BA phases (all P＜0.001).No significant difference was found in subjective image scores of lung and mediastinal setting and the excellence rate of vascular visualization in both groups (all P＞0.05).Conclusion Using IMR,dual phase contrast-enhanced chest CT allows for a radiation dose reduction up to 61.52％,meanwhile,ensures the image quality and meets the diagnostic requirements.
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Objective To investigate the impact of quantitative measurement for lung volume using iterative model reconstruction (IMR),hybrid iterative reconstruction (iDose4 )and filtered back projection (FBP),and to compare the image noise between different reconstruction methods.Methods 70 subjects were performed with low-dose chest CT scan (Philips Brilliance 256 iCT),and the original data were reconstructed with IMR (algorithm:Routine,SharpPlus,Soft Tissue,level:1 - 3 ),iDose4 and FBP respectively.We set less than -950 HU as emphysema threshold,calculated the total lung volume (TLV),total emphysema volume (TEV),emphysema index (EI)and objective image noise (OIN),and then compared the quantitative parameters and OIN between different groups.Results All parameters showed a significantly statistical difference (P =0.000)except TLV (P =1.000).The TEV and EI are significant higher in IMR-S group than in other groups.The OIN in IMR-S-L1 group was the highest,and the FBP group was the second-highest.OIN in iDose4 group was lower than that in IMR-S groups but higher than that in IMR-R and IMR-ST group.Conclusion SharpPlus algorithm of IMR will affect the quantitative measurement of lung volume under low-radiation-dose condition,and the OIN in IMR-S groups is obvious.Therefore SharpPlus algorithm is not recommended for quantitative analysis of lung volume.The Routine and Soft Tissue algorithm will not affect the quantitative measurement,and can distinctly reduce the OIN compared with idose4 and FBP.
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Objective To investigate the impact of quantitative measurement for lung volume using iterative model reconstruction (IMR),hybrid iterative reconstruction (iDose4 )and filtered back projection (FBP),and to compare the image noise between different reconstruction methods.Methods 70 subjects were performed with low-dose chest CT scan (Philips Brilliance 256 iCT),and the original data were reconstructed with IMR (algorithm:Routine,SharpPlus,Soft Tissue,level:1 - 3 ),iDose4 and FBP respectively.We set less than -950 HU as emphysema threshold,calculated the total lung volume (TLV),total emphysema volume (TEV),emphysema index (EI)and objective image noise (OIN),and then compared the quantitative parameters and OIN between different groups.Results All parameters showed a significantly statistical difference (P =0.000)except TLV (P =1.000).The TEV and EI are significant higher in IMR-S group than in other groups.The OIN in IMR-S-L1 group was the highest,and the FBP group was the second-highest.OIN in iDose4 group was lower than that in IMR-S groups but higher than that in IMR-R and IMR-ST group.Conclusion SharpPlus algorithm of IMR will affect the quantitative measurement of lung volume under low-radiation-dose condition,and the OIN in IMR-S groups is obvious.Therefore SharpPlus algorithm is not recommended for quantitative analysis of lung volume.The Routine and Soft Tissue algorithm will not affect the quantitative measurement,and can distinctly reduce the OIN compared with idose4 and FBP.
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Objective To investigate the feasibility of contrast-enhanced CT with low tube voltage using iterative model reconstruction (IMR) technique.Methods Sixty patients were randomly assigned into 2 groups (group A and group B, 30 each) according to random number table.All patients underwent contrast-enhanced hepatic CT.Group A was scanned with 100 kV at arterial phase(AP) and 120 kV at portal vein phase (PVP), while group B was scanned with 120 kV at AP and 100 kV at PVP.All protocols were performed at the same tube current of 250 mAs.Raw data were reconstructed with IMR for AP images in group A and PVP images in group B;and reconstructed with FBP for AP images in group B and PVP images in group A.Images of 4 different groups were obtained: A1(AP,100 kV,IMR) , B1(AP,120 kV, FBP), A2(PVP, 120 kV,FBP) and B2(PVP, 100 kV, IMR).Subjective evaluation indexes for image quality including low-contrast detectability, lesion edge sharpness, image distortion and diagnostic confidence.Objective evaluation indexes included CT attenuation of hepatic parenchyma, image noise, SNR and CNR, which were assessed and compared between groups A1 and B1, groups A2 and B2.Effective radiation doses were calculated.Results Effective dose in group A1 was reduced 35.1％ compared toB1 (t=ll.05, P＜0.01), while a reduction of 37.7％ in group B2 compared to A2 (t=11.64,P ＜ 0.01).Subjective image quality score of low-contrast detectability and lesion edge sharpness were significantly higher in group A1 compared to B1 (Z =6.391, 3.200, P ＜ 0.01), as well as in group B2 compared to A2 (Z =6.559, 3.409, P ＜ 0.01).No differences were found in image distortion and diagnostic confidence between groups A1 and B1, groups A2 and B2, respectively (P ＞ 0.05).Significantly lower image noise and higher SNR/CNR were found in group A1 compared to group B1 (t =12.889, 15.458, 1.325, P ＜ 0.01) , as well as in group B2 compared to group A2(t =15.163, 15.308, 3.136, P ＜0.01).Conclusions Significant radiation dose reduction and image quality improvement in contrast-enhanced hepatic CT can be reached by using low tube voltage protocol combining with IMR technique.