AIM To compare radiation dose and image quality of lowdose computed tomography(CT) protocol combined with hybrid-iterative reconstruction algorithm with standarddose CT examinations for follow-up of oncologic patients...AIM To compare radiation dose and image quality of lowdose computed tomography(CT) protocol combined with hybrid-iterative reconstruction algorithm with standarddose CT examinations for follow-up of oncologic patients. METHODS Fifty-one patients with known malignant diseases which underwent, during clinical follow-up, both standarddose and low-dose whole-body CT scans were enrolled. Low-dose CT was performed on 256-row scanner, with 120 kV and automated m A modulation, and iterative reconstruction algorithm. Standard-dose CT was performed on 16-rows scanner, with 120 kV, 200-400 m As(depending on patient weight). We evaluated density values and signal-to-noise ratio, along with image noise(SD), sharpness and diagnostic quality with 4-point scale.RESULTS Density values in liver, spleen and aorta were higher in lowdose images(liver 112.55 HU vs 103.90 HU, P < 0.001), as SD values in liver and spleen(liver 16.81 vs 14.41). Volumetric-Computed-Tomographic-Dose-Index(CTDIvol) and Dose-Length-Product(DLP) were significantly lower in low-dose CT as compared to standard-dose(DLP 1025.6 m Gy*cm vs 1429.2 m Gy*cm, P < 0.001) with overall dose reduction of 28.9%. Qualitative analysis did not reveal significant differences in image noise and diagnostic quality.CONCLUSION Automatic tube-current modulation combined with hybriditerative algorithm allows radiation dose reduction of 28.9% without loss of diagnostic quality, being useful in reducing dose exposure in oncologic patients.展开更多
To minimize radiation risk,dose reduction is important in the diagnostic and therapeutic applications of computed tomography(CT).However,image noise degrades image quality owing to the reduced X-ray dose and a possibl...To minimize radiation risk,dose reduction is important in the diagnostic and therapeutic applications of computed tomography(CT).However,image noise degrades image quality owing to the reduced X-ray dose and a possible unacceptably reduced diagnostic performance.Deep learning approaches with convolutional neural networks(CNNs)have been proposed for natural image denoising;however,these approaches might introduce image blurring or loss of original gradients.The aim of this study was to compare the dose-dependent properties of a CNN-based denoising method for low-dose CT with those of other noise-reduction methods on unique CT noise-simulation images.To simulate a low-dose CT image,a Poisson noise distribution was introduced to normal-dose images while convoluting the CT unit-specific modulation transfer function.An abdominal CT of 100 images obtained from a public database was adopted,and simulated dose-reduction images were created from the original dose at equal 10-step dose-reduction intervals with a final dose of 1/100.These images were denoised using the denoising network structure of CNN(DnCNN)as the general CNN model and for transfer learning.To evaluate the image quality,image similarities determined by the structural similarity index(SSIM)and peak signal-to-noise ratio(PSNR)were calculated for the denoised images.Significantly better denoising,in terms of SSIM and PSNR,was achieved by the DnCNN than by other image denoising methods,especially at the ultra-low-dose levels used to generate the 10%and 5%dose-equivalent images.Moreover,the developed CNN model can eliminate noise and maintain image sharpness at these dose levels and improve SSIM by approximately 10%from that of the original method.In contrast,under small dose-reduction conditions,this model also led to excessive smoothing of the images.In quantitative evaluations,the CNN denoising method improved the low-dose CT and prevented over-smoothing by tailoring the CNN model.展开更多
Background:Screening using low-dose computed tomography(LDCT)is a more effective approach and has the potential to detect lung cancer more accurately.We aimed to conduct a meta-analysis to estimate the accuracy of pop...Background:Screening using low-dose computed tomography(LDCT)is a more effective approach and has the potential to detect lung cancer more accurately.We aimed to conduct a meta-analysis to estimate the accuracy of population-based screening studies primarily assessing baseline LDCT screening for lung cancer.Methods:MEDLINE,Excerpta Medica Database,and Web of Science were searched for articles published up to April 10,2022.According to the inclusion and exclusion criteria,the data of true positives,false-positives,false negatives,and true negatives in the screening test were extracted.Quality Assessment of Diagnostic Accuracy Studies-2 was used to evaluate the quality of the literature.A bivariate random effects model was used to estimate pooled sensitivity and specificity.The area under the curve(AUC)was calculated by using hierarchical summary receiver-operating characteristics analysis.Heterogeneity between studies was measured using the Higgins I 2 statistic,and publication bias was evaluated using a Deeks’funnel plot and linear regression test.Results:A total of 49 studies with 157,762 individuals were identified for the final qualitative synthesis;most of them were from Europe and America(38 studies),ten were from Asia,and one was from Oceania.The recruitment period was 1992 to 2018,and most of the subjects were 40 to 75 years old.The analysis showed that the AUC of lung cancer screening by LDCT was 0.98(95%CI:0.96-0.99),and the overall sensitivity and specificity were 0.97(95%CI:0.94-0.98)and 0.87(95%CI:0.82-0.91),respectively.The funnel plot and test results showed that there was no significant publication bias among the included studies.Conclusions:Baseline LDCT has high sensitivity and specificity as a screening technique for lung cancer.However,long-term follow-up of the whole study population(including those with a negative baseline screening result)should be performed to enhance the accuracy of LDCT screening.展开更多
Displacement of a cardiac pacemaker lead or myocardial perforation by a lead is an infrequent complication of pacemaker implantation. While standard cardiac CT is useful for diagnosing such complications when routine ...Displacement of a cardiac pacemaker lead or myocardial perforation by a lead is an infrequent complication of pacemaker implantation. While standard cardiac CT is useful for diagnosing such complications when routine examinations can not, the potential risks associated with exposure to the high doses of radiation used in CT are of concern. Here, we report three cases </span><span style="font-family:"white-space:normal;">in which pacemaker lead displacement or myocardial perforation was definitively diagnosed by l</span><span style="font-family:"white-space:normal;">ow-dose cardiac CT used in the high-pitch spiral mode, when other more routine examinations failed to suggest their occurrence.</span><span style="font-family:"white-space:normal;"> </span><span style="font-family:"white-space:normal;">The mean dose of radiation used for definitively diagnosing the three patients was relatively low (2.19 mSv).展开更多
Background:According to the World Health Organization,China is one of 22 countries with serious tuberculosis(TB)infections and one of the 27 countries with serious multidrug-resistant TB strains.Despite the decline of...Background:According to the World Health Organization,China is one of 22 countries with serious tuberculosis(TB)infections and one of the 27 countries with serious multidrug-resistant TB strains.Despite the decline of tuberculosis in the overall population,healthcare workers(HCWs)are still at a high risk of infection.Compared with high-income countries,the TB prevalence among HCWs is higher in low-and middle-income countries.Low-dose computed tomography(LDCT)is becoming more popular due to its superior sensitivity and lower radiation dose.However,there have been no reports about active pulmonary tuberculosis(PTB)among HCWs as assessed with LDCT.The purposes of this study were to examine PTB statuses in HCWs in hospitals specializing in TB treatment and explore the significance of the application of LDCT to these workers.Methods:This study retrospectively analysed the physical examination data of healthcare workers in the Beijing Chest Hospital from September 2012 to December 2015.Low-dose lung CT examinations were performed in all cases.The comparisons between active and inactive PTB according to the CT findings were made using the Pearson chi-square test or the Fisher’s exact test.Comparisons between the incidences of active PTB in high-risk areas and non-high-risk areas were performed using the Pearson chi-square test.Analyses of active PTB were performed according to different ages,numbers of years on the job,and the risks of the working areas.Active PTB as diagnosed by the LDCT examinations alone was compared with the final comprehensive diagnoses,and the sensitivity and positive predictive value were calculated.Results:A total of 1012 participants were included in this study.During the 4-year period of medical examinations,active PTB was found in 19 cases,and inactive PTB was found in 109 cases.The prevalence of active PTB in the participants was 1.24%,0.67%,0.81%,and 0.53%for years 2012 to 2015.The corresponding incidences of active PTB among the tuberculosis hospital participants were 0.86%,0.41%,0.54%,and 0.26%.Most HCWs with active TB(78.9%,15/19)worked in the high-risk areas of the hospital.There was a significant difference in the incidences of active PTB between the HCWs who worked in the high-risk and non-high-risk areas(odds ratio[OR],14.415;95%confidence interval(CI):4.733-43.896).Comparisons of the CT signs between the active and inactive groups via chi-square tests revealed that the tree-in-bud,cavity,fibrous shadow,and calcification signs exhibited significant differences(P=0.000,0.021,0.001,and 0.024,respectively).Tree-in-bud and cavity opacities suggest active pulmonary tuberculosis,whereas fibrous shadow and calcification opacities are the main features of inactive pulmonary tuberculosis.Comparison with the final comprehensive diagnoses revealed that the sensitivity and positive predictive value of the diagnoses of active PTB based on LDCT alone were 100%and 86.4%,respectively.Conclusions:Healthcare workers in tuberculosis hospitals are a high-risk group for active PTB.Yearly LDCT examinations of such high-risk groups are feasible and necessary.展开更多
Background The incidence of thyroid cancer has been increasing.Our aim was to evaluate the efficacy of low-dose dualphase helical computed tomography （CT） in the characterization of thyroid lesions,and to discuss th...Background The incidence of thyroid cancer has been increasing.Our aim was to evaluate the efficacy of low-dose dualphase helical computed tomography （CT） in the characterization of thyroid lesions,and to discuss the relationship between image characteristics and their pathology.Methods One hundred and six patients with thyroid lesions underwent low-dose dual-phase helical CT after the injection of contrast material.CT scans were obtained at arterial and venous phase with delays of 25 and 65 seconds,and tube current of 60 and 120 mA,respectively.The attenuation change in the lesion between the arterial and venous phase was analyzed and categorized as ＂increased,＂ ＂decreased,＂ ＂mixed＂ or ＂no change.＂ Results Histopathologic diagnosis was obtained by surgery in 106 patients （115 lesions）.Of the 106 patients,45 had nodular goiter,5 thyroid adenoma,6 thyroiditis,and 50 papillary thyroid carcinoma （PTC） （59 lesions）.The attenuation value showed a significant difference （P ＜0.05） between the arterial and venous phase for the high attenuation area.There was statistical significant difference in terms of attenuation value in high attenuation areas at both phases and in low attenuation areas on arterial phase between nodular goiter and PTC （P ＜0.05）.However,there was no significant difference in attenuation value between adenoma and PTC.Twenty-nine cases （76.3％） of goiter manifested mixed type,3 cases （3/5） of adenoma showed decreased type,6 cases （6/6） of thyroiditis showed increased type,and 55 cases （93.2％） of PTC showed decreased type attenuation.The sensitivity,specificity for thyroid carcinoma by dual-phase CT were 94.9％ and 80.4％ respectively.The overall diagnostic accuracy for thyroid lesions by dual-phase CT was 87.8％.Conclusions The performance of dual-phase helical CT is related to the pathological structure of the lesions.The analysis of enhancement patterns by using dual-phase helical CT will be helpful in the differential diagnosis of thyroid lesions.展开更多
A linear denoising filter is usually of lowpass type,and the main parameter in a lowpass filter is the cutoff frequency.The lowpass filters are normally shift invariant and can be implemented as convolution in the spa...A linear denoising filter is usually of lowpass type,and the main parameter in a lowpass filter is the cutoff frequency.The lowpass filters are normally shift invariant and can be implemented as convolution in the spatial domain or as multiplication in the Fourier domain.This paper presents a linear filter that is not characterized by its cutoff frequency but is characterized by the noise model.An example of such a linear filter is presented for lowdose X-ray computed tomography(CT).展开更多
Two novel ultrasound imaging techniques with imaging contrast mechanisms are in the works:X-ray-induced acoustic computed tomography(XACT),and nanoscale photoacoustic tomogra-phy(nPAT).XACT has incredible potential in...Two novel ultrasound imaging techniques with imaging contrast mechanisms are in the works:X-ray-induced acoustic computed tomography(XACT),and nanoscale photoacoustic tomogra-phy(nPAT).XACT has incredible potential in:(1)biomedical imaging,through which a 3D image can be generated using only a single X-ray projection,and(2)radiation dosimetry.nPATas a new alternative of super-resolution microscopy can break through the optical difraction limitand is capable of exploring sub-celular structures without reliance on fuorescence labeling.We expect these new imaging techniques to find widespread applications in both pre-clinical andclinical biomedical research.展开更多
文摘AIM To compare radiation dose and image quality of lowdose computed tomography(CT) protocol combined with hybrid-iterative reconstruction algorithm with standarddose CT examinations for follow-up of oncologic patients. METHODS Fifty-one patients with known malignant diseases which underwent, during clinical follow-up, both standarddose and low-dose whole-body CT scans were enrolled. Low-dose CT was performed on 256-row scanner, with 120 kV and automated m A modulation, and iterative reconstruction algorithm. Standard-dose CT was performed on 16-rows scanner, with 120 kV, 200-400 m As(depending on patient weight). We evaluated density values and signal-to-noise ratio, along with image noise(SD), sharpness and diagnostic quality with 4-point scale.RESULTS Density values in liver, spleen and aorta were higher in lowdose images(liver 112.55 HU vs 103.90 HU, P < 0.001), as SD values in liver and spleen(liver 16.81 vs 14.41). Volumetric-Computed-Tomographic-Dose-Index(CTDIvol) and Dose-Length-Product(DLP) were significantly lower in low-dose CT as compared to standard-dose(DLP 1025.6 m Gy*cm vs 1429.2 m Gy*cm, P < 0.001) with overall dose reduction of 28.9%. Qualitative analysis did not reveal significant differences in image noise and diagnostic quality.CONCLUSION Automatic tube-current modulation combined with hybriditerative algorithm allows radiation dose reduction of 28.9% without loss of diagnostic quality, being useful in reducing dose exposure in oncologic patients.
基金This work was supported by JSPS KAKENHI,No.18 K15563.
文摘To minimize radiation risk,dose reduction is important in the diagnostic and therapeutic applications of computed tomography(CT).However,image noise degrades image quality owing to the reduced X-ray dose and a possible unacceptably reduced diagnostic performance.Deep learning approaches with convolutional neural networks(CNNs)have been proposed for natural image denoising;however,these approaches might introduce image blurring or loss of original gradients.The aim of this study was to compare the dose-dependent properties of a CNN-based denoising method for low-dose CT with those of other noise-reduction methods on unique CT noise-simulation images.To simulate a low-dose CT image,a Poisson noise distribution was introduced to normal-dose images while convoluting the CT unit-specific modulation transfer function.An abdominal CT of 100 images obtained from a public database was adopted,and simulated dose-reduction images were created from the original dose at equal 10-step dose-reduction intervals with a final dose of 1/100.These images were denoised using the denoising network structure of CNN(DnCNN)as the general CNN model and for transfer learning.To evaluate the image quality,image similarities determined by the structural similarity index(SSIM)and peak signal-to-noise ratio(PSNR)were calculated for the denoised images.Significantly better denoising,in terms of SSIM and PSNR,was achieved by the DnCNN than by other image denoising methods,especially at the ultra-low-dose levels used to generate the 10%and 5%dose-equivalent images.Moreover,the developed CNN model can eliminate noise and maintain image sharpness at these dose levels and improve SSIM by approximately 10%from that of the original method.In contrast,under small dose-reduction conditions,this model also led to excessive smoothing of the images.In quantitative evaluations,the CNN denoising method improved the low-dose CT and prevented over-smoothing by tailoring the CNN model.
基金a grant from the Natural Science Foundation of Henan Province(No.212300410261).
文摘Background:Screening using low-dose computed tomography(LDCT)is a more effective approach and has the potential to detect lung cancer more accurately.We aimed to conduct a meta-analysis to estimate the accuracy of population-based screening studies primarily assessing baseline LDCT screening for lung cancer.Methods:MEDLINE,Excerpta Medica Database,and Web of Science were searched for articles published up to April 10,2022.According to the inclusion and exclusion criteria,the data of true positives,false-positives,false negatives,and true negatives in the screening test were extracted.Quality Assessment of Diagnostic Accuracy Studies-2 was used to evaluate the quality of the literature.A bivariate random effects model was used to estimate pooled sensitivity and specificity.The area under the curve(AUC)was calculated by using hierarchical summary receiver-operating characteristics analysis.Heterogeneity between studies was measured using the Higgins I 2 statistic,and publication bias was evaluated using a Deeks’funnel plot and linear regression test.Results:A total of 49 studies with 157,762 individuals were identified for the final qualitative synthesis;most of them were from Europe and America(38 studies),ten were from Asia,and one was from Oceania.The recruitment period was 1992 to 2018,and most of the subjects were 40 to 75 years old.The analysis showed that the AUC of lung cancer screening by LDCT was 0.98(95%CI:0.96-0.99),and the overall sensitivity and specificity were 0.97(95%CI:0.94-0.98)and 0.87(95%CI:0.82-0.91),respectively.The funnel plot and test results showed that there was no significant publication bias among the included studies.Conclusions:Baseline LDCT has high sensitivity and specificity as a screening technique for lung cancer.However,long-term follow-up of the whole study population(including those with a negative baseline screening result)should be performed to enhance the accuracy of LDCT screening.
文摘Displacement of a cardiac pacemaker lead or myocardial perforation by a lead is an infrequent complication of pacemaker implantation. While standard cardiac CT is useful for diagnosing such complications when routine examinations can not, the potential risks associated with exposure to the high doses of radiation used in CT are of concern. Here, we report three cases </span><span style="font-family:"white-space:normal;">in which pacemaker lead displacement or myocardial perforation was definitively diagnosed by l</span><span style="font-family:"white-space:normal;">ow-dose cardiac CT used in the high-pitch spiral mode, when other more routine examinations failed to suggest their occurrence.</span><span style="font-family:"white-space:normal;"> </span><span style="font-family:"white-space:normal;">The mean dose of radiation used for definitively diagnosing the three patients was relatively low (2.19 mSv).
文摘Background:According to the World Health Organization,China is one of 22 countries with serious tuberculosis(TB)infections and one of the 27 countries with serious multidrug-resistant TB strains.Despite the decline of tuberculosis in the overall population,healthcare workers(HCWs)are still at a high risk of infection.Compared with high-income countries,the TB prevalence among HCWs is higher in low-and middle-income countries.Low-dose computed tomography(LDCT)is becoming more popular due to its superior sensitivity and lower radiation dose.However,there have been no reports about active pulmonary tuberculosis(PTB)among HCWs as assessed with LDCT.The purposes of this study were to examine PTB statuses in HCWs in hospitals specializing in TB treatment and explore the significance of the application of LDCT to these workers.Methods:This study retrospectively analysed the physical examination data of healthcare workers in the Beijing Chest Hospital from September 2012 to December 2015.Low-dose lung CT examinations were performed in all cases.The comparisons between active and inactive PTB according to the CT findings were made using the Pearson chi-square test or the Fisher’s exact test.Comparisons between the incidences of active PTB in high-risk areas and non-high-risk areas were performed using the Pearson chi-square test.Analyses of active PTB were performed according to different ages,numbers of years on the job,and the risks of the working areas.Active PTB as diagnosed by the LDCT examinations alone was compared with the final comprehensive diagnoses,and the sensitivity and positive predictive value were calculated.Results:A total of 1012 participants were included in this study.During the 4-year period of medical examinations,active PTB was found in 19 cases,and inactive PTB was found in 109 cases.The prevalence of active PTB in the participants was 1.24%,0.67%,0.81%,and 0.53%for years 2012 to 2015.The corresponding incidences of active PTB among the tuberculosis hospital participants were 0.86%,0.41%,0.54%,and 0.26%.Most HCWs with active TB(78.9%,15/19)worked in the high-risk areas of the hospital.There was a significant difference in the incidences of active PTB between the HCWs who worked in the high-risk and non-high-risk areas(odds ratio[OR],14.415;95%confidence interval(CI):4.733-43.896).Comparisons of the CT signs between the active and inactive groups via chi-square tests revealed that the tree-in-bud,cavity,fibrous shadow,and calcification signs exhibited significant differences(P=0.000,0.021,0.001,and 0.024,respectively).Tree-in-bud and cavity opacities suggest active pulmonary tuberculosis,whereas fibrous shadow and calcification opacities are the main features of inactive pulmonary tuberculosis.Comparison with the final comprehensive diagnoses revealed that the sensitivity and positive predictive value of the diagnoses of active PTB based on LDCT alone were 100%and 86.4%,respectively.Conclusions:Healthcare workers in tuberculosis hospitals are a high-risk group for active PTB.Yearly LDCT examinations of such high-risk groups are feasible and necessary.
文摘Background The incidence of thyroid cancer has been increasing.Our aim was to evaluate the efficacy of low-dose dualphase helical computed tomography （CT） in the characterization of thyroid lesions,and to discuss the relationship between image characteristics and their pathology.Methods One hundred and six patients with thyroid lesions underwent low-dose dual-phase helical CT after the injection of contrast material.CT scans were obtained at arterial and venous phase with delays of 25 and 65 seconds,and tube current of 60 and 120 mA,respectively.The attenuation change in the lesion between the arterial and venous phase was analyzed and categorized as ＂increased,＂ ＂decreased,＂ ＂mixed＂ or ＂no change.＂ Results Histopathologic diagnosis was obtained by surgery in 106 patients （115 lesions）.Of the 106 patients,45 had nodular goiter,5 thyroid adenoma,6 thyroiditis,and 50 papillary thyroid carcinoma （PTC） （59 lesions）.The attenuation value showed a significant difference （P ＜0.05） between the arterial and venous phase for the high attenuation area.There was statistical significant difference in terms of attenuation value in high attenuation areas at both phases and in low attenuation areas on arterial phase between nodular goiter and PTC （P ＜0.05）.However,there was no significant difference in attenuation value between adenoma and PTC.Twenty-nine cases （76.3％） of goiter manifested mixed type,3 cases （3/5） of adenoma showed decreased type,6 cases （6/6） of thyroiditis showed increased type,and 55 cases （93.2％） of PTC showed decreased type attenuation.The sensitivity,specificity for thyroid carcinoma by dual-phase CT were 94.9％ and 80.4％ respectively.The overall diagnostic accuracy for thyroid lesions by dual-phase CT was 87.8％.Conclusions The performance of dual-phase helical CT is related to the pathological structure of the lesions.The analysis of enhancement patterns by using dual-phase helical CT will be helpful in the differential diagnosis of thyroid lesions.
文摘A linear denoising filter is usually of lowpass type,and the main parameter in a lowpass filter is the cutoff frequency.The lowpass filters are normally shift invariant and can be implemented as convolution in the spatial domain or as multiplication in the Fourier domain.This paper presents a linear filter that is not characterized by its cutoff frequency but is characterized by the noise model.An example of such a linear filter is presented for lowdose X-ray computed tomography(CT).
文摘Two novel ultrasound imaging techniques with imaging contrast mechanisms are in the works:X-ray-induced acoustic computed tomography(XACT),and nanoscale photoacoustic tomogra-phy(nPAT).XACT has incredible potential in:(1)biomedical imaging,through which a 3D image can be generated using only a single X-ray projection,and(2)radiation dosimetry.nPATas a new alternative of super-resolution microscopy can break through the optical difraction limitand is capable of exploring sub-celular structures without reliance on fuorescence labeling.We expect these new imaging techniques to find widespread applications in both pre-clinical andclinical biomedical research.
