Effect of chest low-dose spiral CT scan for lung cancer screening among asymptomatic adults / 中国辐射卫生

@#<b>Objective</b> To evaluate the effect of chest low-dose spiral computed tomography (LDCT) scan for lung cancer screening among asymptomatic adults. <b>Methods</b> Asymptomatic adults at the age of 18 years and older receiving LDCT scans for lung cancer screening in Shanghai Pudong New Area People’s Hospital from January 2019 to December 2021 were recruited, and those with positive pulmonary nodules underwent percutaneous needle biopsy or bronchoscopic biopsy for pathological examination of pulmonary nodules. The effect of LDCT scan for lung cancer screening was compared between never-smokers and ever-smokers. <b>Results</b> A total of 9359 eligible individuals meeting inclusion and exclusion criteria were enrolled, including 4492 never-smokers and 4867 ever-smokers, and the overall detection rate of positive pulmonary nodules was 16.2%. There were significant differences between never-smokers and ever-smokers in terms of age at the first LDCT screening, gender composition, body mass index, and cumulative follow-up period (<i>P</i> < 0.05), and no significant differences were seen in terms of types of pulmonary nodules at the first LDCT screening and proportion of subjects with positive pulmonary nodules (<i>P</i> > 0.05). There were no significant differences between never-smokers and ever-smokers with positive pulmonary nodules in terms of proportion of subjects with positive pulmonary nodules at the first LDCT screening, proportion of subjects with positive pulmonary nodules during the follow-up, types of pulmonary nodules at the first LDCT screening, proportion of subjects with multiple pulmonary nodules, and mean size of pulmonary nodules at the first LDCT screening (<i>P</i> > 0.05); however, there was a significant difference in the nature of pulmonary nodules (<i>χ</i>² = 47.23, <i>P</i> < 0.01). In addition, the incidence rate of lung cancer was significantly lower among never-smokers with positive pulmonary nodules than among ever-smokers with positive pulmonary nodules (<i>χ</i>²=6.42, <i>P</i> < 0.01). <b>Conclusion</b> Chest LDCT scan may significantly improve the detection rate of pulmonary nodules among never-smokers. Although the detection rate of lung cancer is significantly lower among never-smokers with positive pulmonary nodules than among ever-smokers with positive pulmonary nodules, there is no significant difference between never-smokers and ever-smokers in the false-positive rate of lung cancer screening with chest LDCT scan. Chest LDCT scan is recommended for lung cancer screening among asymptomatic adults.

Noise reduction in low-dose computed tomography with noise equivalent image and deep learning / 中华放射医学与防护杂志

Objective:To investigate the method of simulating low-dose CT (LDCT) images using routine dose level scanning mode to generate LDCT images with correspondence to the routine dose CT (RDCT) images in the training sets for deep learning model, which would be used for LDCT noise reduction.Methods:The CT images reconstructed by different algorithms in Philips CT Big Core had different noise levels, where the noise was larger with iDose 4 algorithm and lower with IMR(knowledge-based iterative model reconstruction)algorithm. A new method of replacing LDCT image with noise equivalent reconstructed image was proposed. The uniform module of CTP712 was scanned with the exposure of 250 mAs for RDCT, 35 mAs for LDCT. The images were reconstructed using IMR algorithm for LDCT images and iDose 4 algorithm at multiple noise reduction levels for RDCT images, respectively. The noise distribution of each image set was analyzed to find the noise equivalent images of LDCT. Then, RDCT images, those selected images were used for training cycle-consistent adversarial networks (CycleGAN)model, and the noise reduction ability of the proposed method on real LDCT images of phantom was tested. Results:The RDCT images generated with iDose 4 level 1 could substitute the LDCT images reconstructed with IMR algorithm. The radiation dose was reduced by 86% in low dose scanning. Using CycleGAN model, the noise reduction degree was 45% for uniform module, and 50%, 13%, 7% for CIRS-SBRT 038 phantom in the specific regions of brain, spinal cord, bone, respectively. Conclusions:Equivalent noise level reconstructed images could potentially serve as the alternative of LDCT images for deep learning network training to avoid additional radiation dose. The generated CT images had substantially reduced noise relative to that of LDCT.

Eeffect of ultra-low dose CT scanning on the diagnosis of ankle fracture and the quality of a three-dimensional printing model / 中华放射医学与防护杂志

Objective:To investigate the effect of ultra-low dose (ULD) computed tomography (CT) scanning on the diagnosis of ankle fractures and the quality of a three-dimensional printing (3DP) model.Methods:This study was a prospective study. A total of 61 patients with clinical ankle fractures treated conservatively in Zhuhai Hospital of Guangdong Hospital of Traditional Chinese Medicine from November 2019 to January 2022 were included in this study. Patients underwent standard dose (SD) CT scan and ultra-low dose (ULD) CT scan, respectively. The tube voltage/tube current of SD and ULD were 120 kV/100 mAs and 80 kV/10 mAs, respectively. Two senior radiologists evaluated the presence of ankle fractures. The effective radiation dose ( E), noise, signal-to-noise ratio (SNR), contrast signal-to-noise ratio (CNR), and CT value of bone cortex minus CT value of peripheral fat (CTc) were compared. The radiologists also evaluated the discoverability, diagnosability, and overall image quality of the fracture line according to Likert′s 5-point scoring method. Two senior orthopedists subjectively evaluated the quality of each 3DP model (model clarity and operation guidance). A score ≥ 3 indicated that the quality of the CT diagnostic image and 3DP model were acceptable. Results:The interval between the two CT scans was (9.23 ± 1.92) d. A total of 94 fracture sites were found. There were no missed diagnosis or misdiagnosis based on the SD and ULD scans.Noise, SNR, and CNR were better on the SD CT scanning ( F=5.92, 9.70, 8.32, P=0.00), however, CTc was higher on the ULD scans ( F=27.55, P<0.01). The image scores of the SD and ULD scans were (4.97 ± 0.18) and (4.21 ± 0.71), and the quality scores of the 3DP model (4.99 ± 0.01) and (4.87 ± 0.34), respectively. The SD scans were better than the ULD scans with respect to CT image quality and 3DP model quality ( Z=-6.88, -2.91, P<0.01), but both were considered suitable to meet clinical needs (all ≥ 3 points). The E associated with SD and ULD scannings were (34.68 ± 4.96) μSV and (1.04 ± 0.10) μSV, respectively. The latter was thus significantly better than the former ( F=38.77, P =0.00). Conclusions:The E value of ULD scanning is about 3.00% of SD scanning E, which can meet the needs of clinical diagnosis of ankle fracture and 3DP model printing diagnosis.

Performance of low-dose CT image reconstruction for detecting intracerebral hemorrhage: selection of dose, algorithms and their combinations / 南方医科大学学报

OBJECTIVE@#To investigate the performance of different low-dose CT image reconstruction algorithms for detecting intracerebral hemorrhage.@*METHODS@#Low-dose CT imaging simulation was performed on CT images of intracerebral hemorrhage at 30%, 25% and 20% of normal dose level (defined as 100% dose). Seven algorithms were tested to reconstruct low-dose CT images for noise suppression, including filtered back projection algorithm (FBP), penalized weighted least squares-total variation (PWLS-TV), non-local mean filter (NLM), block matching 3D (BM3D), residual encoding-decoding convolutional neural network (REDCNN), the FBP convolutional neural network (FBPConvNet) and image restoration iterative residual convolutional network (IRLNet). A deep learning-based model (CNN-LSTM) was used to detect intracerebral hemorrhage on normal dose CT images and low-dose CT images reconstructed using the 7 algorithms. The performance of different reconstruction algorithms for detecting intracerebral hemorrhage was evaluated by comparing the results between normal dose CT images and low-dose CT images.@*RESULTS@#At different dose levels, the low-dose CT images reconstructed by FBP had accuracies of detecting intracerebral hemorrhage of 82.21%, 74.61% and 65.55% at 30%, 25% and 20% dose levels, respectively. At the same dose level (30% dose), the images reconstructed by FBP, PWLS-TV, NLM, BM3D, REDCNN, FBPConvNet and IRLNet algorithms had accuracies for detecting intracerebral hemorrhage of 82.21%, 86.80%, 89.37%, 81.43%, 90.05%, 90.72% and 93.51%, respectively. The images reconstructed by IRLNet at 30%, 25% and 20% dose levels had accuracies for detecting intracerebral hemorrhage of 93.51%, 93.51% and 93.06%, respectively.@*CONCLUSION@#The performance of reconstructed low-dose CT images for detecting intracerebral hemorrhage is significantly affected by both dose and reconstruction algorithms. In clinical practice, choosing appropriate dose level and reconstruction algorithm can greatly reduce the radiation dose and ensure the detection performance of CT imaging for intracerebral hemorrhage.

Computed tomography with low-dose radiation versus standard-dose radiation for diagnosing fractures: systematic review and meta-analysis

BACKGROUND: Computed tomography (CT) accounts for 13% of all radiological examinations in the United States and 40-70% of the radiation that patients receive. Even with the advent of magnetic resonance imaging (MRI), CT continues to be the gold standard for diagnosing bone fractures. There is uncertainty as to whether CT with a low radiation dose has a fracture detection rate similar to that of standard-dose CT. OBJECTIVE: To determine the detection rate of low-dose radiation CT and standard-dose radiation CT for fractures, in patients with suspected fractures. DESIGN AND SETTING: Systematic review of comparative studies on diagnostic accuracy within the evidence-based health program at a federal university in São Paulo (SP), Brazil. METHODS: We searched the electronic databases Cochrane Library, MEDLINE, EMBASE and LILACS up to June 29, 2020, for studies evaluating the detection rates of low-dose CT and standard-dose CT for diagnosing bone fractures. The Research Triangle Institute (RTI) item bank tool was used for methodological quality evaluation. RESULTS: The fracture detection rate according to the number of bones evaluated, using CT with low-dose radiation was 20.3%, while with standard-dose radiation it was 19.2%, and the difference between the methods was not significant. The fracture detection rate according to the number of patients, using CT with low-dose radiation was 56.0%, while with standard-dose radiation it was 58.7%, and this difference between the methods was not significant, either. CONCLUSION: CT with low-dose radiation presented detection rates similar to those of CT with standard-dose radiation, regardless of the bones evaluated. REGISTRATION NUMBER: CRD42019148491 at the PROSPERO database.

Size-Specific Dose Estimation In the Korean Lung Cancer Screening Project: Does a 32-cm Diameter Phantom Represent a Standard-Sized Patient in Korean Population?

OBJECTIVE: The purposes of this study were to evaluate size-specific dose estimate (SSDE) of low-dose CT (LDCT) in the Korean Lung Cancer Screening (K-LUCAS) project and to determine whether CT protocols from Western countries are appropriate for lung cancer screening in Korea. MATERIALS AND METHODS: For participants (n = 256, four institutions) of K-LUCAS pilot study, volume CT dose index (CTDI(vol)) using a 32-cm diameter reference phantom was compared with SSDE, which was recalculated from CTDI(vol) using size-dependent conversion factor (f-size) based on the body size, as described in the American Association of Physicists in Medicine Report 204. This comparison was subsequently assessed by body mass index (BMI) levels (underweight/normal vs. overweight/obese), and automatic exposure control (AEC) adaptation (yes/no). RESULTS: Size-specific dose estimate was higher than CTDI(vol) (2.22 ± 0.75 mGy vs. 1.67 ± 0.60 mGy, p < 0.001), since the f-size was larger than 1.0 for all participants. The ratio of SSDE to CTDI(vol) was higher in lower BMI groups; 1.26, 1.37, 1.43, and 1.53 in the obese (n = 103), overweight (n = 70), normal (n = 75), and underweight (n = 4), respectively. The ratio of SSDE to CTDI(vol) was greater in standard-sized participants than in large-sized participants independent of AEC adaptation; with AEC, SSDE/CTDI(vol) in large- vs. standard-sized participants: 1.30 ± 0.08 vs. 1.44 ± 0.08 (p < 0.001) and without AEC, 1.32 ± 0.08 vs. 1.42 ± 0.06 (p < 0.001). CONCLUSION: Volume CT dose index based on a reference phantom underestimates radiation exposure of LDCT in standard-sized Korean participants. The optimal radiation dose limit needs to be verified for standard-sized Korean participants.

Effect of Hybrid Kernel and Iterative Reconstruction on Objective and Subjective Analysis of Lung Nodule Calcification in Low-Dose Chest CT

OBJECTIVE: To evaluate the differences in subjective calcification detection rates and objective calcium volumes in lung nodules according to different reconstruction methods using hybrid kernel (FC13-H) and iterative reconstruction (IR). MATERIALS AND METHODS: Overall, 35 patients with small (< 4 mm) calcified pulmonary nodules on chest CT were included. Raw data were reconstructed using filtered back projection (FBP) or IR algorithm (AIDR-3D; Canon Medical Systems Corporation), with three types of reconstruction kernel: conventional lung kernel (FC55), FC13-H and conventional soft tissue kernel (FC13). The calcium volumes of pulmonary nodules were quantified using the modified Agatston scoring method. Two radiologists independently interpreted the role of each nodule calcification on the six types of reconstructed images (FC55/FBP, FC55/AIDR-3D, FC13-H/FBP, FC13-H/AIDR-3D, FC13/FBP, and FC13/AIDR-3D). RESULTS: Seventy-eight calcified nodules detected on FC55/FBP images were regarded as reference standards. The calcium detection rates of FC55/AIDR-3D, FC13-H/FBP, FC13-H/AIDR-3D, FC13/FBP, and FC13/AIDR-3D protocols were 80.7%, 15.4%, 6.4%, 52.6%, and 28.2%, respectively, and FC13-H/AIDR-3D showed the smallest calcium detection rate. The calcium volume varied significantly with reconstruction protocols and FC13/AIDR-3D showed the smallest calcium volume (0.04 ± 0.22 mm³), followed by FC13-H/AIDR-3D. CONCLUSION: Hybrid kernel and IR influence subjective detection and objective measurement of calcium in lung nodules, particularly when both techniques (FC13-H/AIDR-3D) are combined.

Diameter of the Solid Component in Subsolid Nodules on Low-Dose Unenhanced Chest Computed Tomography: Measurement Accuracy for the Prediction of Invasive Component in Lung Adenocarcinoma

OBJECTIVE: To determine if measurement of the diameter of the solid component in subsolid nodules (SSNs) on low-dose unenhanced chest computed tomography (CT) is as accurate as on standard-dose enhanced CT in prediction of pathological size of invasive component of lung adenocarcinoma. MATERIALS AND METHODS: From February 2012 to October 2015, 114 SSNs were identified in 105 patients that underwent low-dose unenhanced and standard-dose enhanced CT pre-operatively. Three radiologists independently measured the largest diameter of the solid component. Intraclass correlation coefficients (ICCs) were used to assess inter-reader agreement. We estimated measurement differences between the size of solid component and that of invasive component. We measured diagnostic accuracy of the prediction of invasive adenocarcinoma using a size criterion of a solid component ≥ 6 mm, and compared them using a generalized linear mixed model. RESULTS: Inter-reader agreement was excellent (ICC, 0.84.0.89). The mean ± standard deviation of absolute measurement differences between the solid component and invasive component was 4 ± 4 mm in low-dose unenhanced CT and 5 ± 4 mm in standard-dose enhanced CT. Diagnostic accuracy was 81.3% (95% confidence interval, 76.7.85.3%) in low-dose unenhanced CT and 76.6% (71.8.81.0%) in standard-dose enhanced CT, with no statistically significant difference (p = 0.130). CONCLUSION: Measurement of the diameter of the solid component of SSNs on low-dose unenhanced chest CT was as accurate as on standard-dose enhanced CT for predicting the invasive component. Thus, low-dose unenhanced CT may be used safely in the evaluation of patients with SSNs.

Nodule Classification on Low-Dose Unenhanced CT and Standard-Dose Enhanced CT: Inter-Protocol Agreement and Analysis of Interchangeability

OBJECTIVE: To measure inter-protocol agreement and analyze interchangeability on nodule classification between low-dose unenhanced CT and standard-dose enhanced CT. MATERIALS AND METHODS: From nodule libraries containing both low-dose unenhanced and standard-dose enhanced CT, 80 solid and 80 subsolid (40 part-solid, 40 non-solid) nodules of 135 patients were selected. Five thoracic radiologists categorized each nodule into solid, part-solid or non-solid. Inter-protocol agreement between low-dose unenhanced and standard-dose enhanced images was measured by pooling κ values for classification into two (solid, subsolid) and three (solid, part-solid, non-solid) categories. Interchangeability between low-dose unenhanced and standard-dose enhanced CT for the classification into two categories was assessed using a pre-defined equivalence limit of 8 percent. RESULTS: Inter-protocol agreement for the classification into two categories {κ, 0.96 (95% confidence interval [CI], 0.94–0.98)} and that into three categories (κ, 0.88 [95% CI, 0.85–0.92]) was considerably high. The probability of agreement between readers with standard-dose enhanced CT was 95.6% (95% CI, 94.5–96.6%), and that between low-dose unenhanced and standard–dose enhanced CT was 95.4% (95% CI, 94.7–96.0%). The difference between the two proportions was 0.25% (95% CI, −0.85–1.5%), wherein the upper bound CI was markedly below 8 percent. CONCLUSION: Inter-protocol agreement for nodule classification was considerably high. Low-dose unenhanced CT can be used interchangeably with standard-dose enhanced CT for nodule classification.

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.

Clinical significance of low-dose CT performed for three consecutive years in diagnosis of lung nodules in coal mine workers with 20 working years / 中华劳动卫生职业病杂志

Objective@#To investigate the clinical significance of low-dose CT (LDCT) in coal mine workers with relatively long working years.@*Methods@#A total of 907 coal mine workers with ≥20 working years were enrolled, among whom there were 863 male and 44 female workers with a mean age of 49.5 years. Digital radiography (DR) was performed for these workers in 2013, and LDCT was performed for three consecutive years from 2014 to 2016.@*Results@#A total of 32 workers were found to have lung nodules by DR in 2013, while in 2014, 269 workers were found to have non-calcified lung nodules by LDCT, and there was a significant difference in the number of workers with lung nodules (χ2=233.73, P<0.005) . There was also a significant difference in the detection rate of nodules between the workers with different working years of dust exposure (χ2=6.648, P=0.00) . The male workers had a significantly higher detection rate of nodules than the female workers (χ2=5.690, P=0.017) . There was no significant difference in the number of nodules between workers with different types of work (χ2=16.985, P=0.05) . There were 443 lung nodules in total, among which 71.56% were solid nodules and 55.75% had a size of ≤4mm; malignant nodules were confirmed by surgery in 6 (0.66%) of the 907 workers after baseline LDCT. LDCT reexamination in 2015 and 2016 found new nodules in 8 workers and enlarged nodules in 3 workers, and there was no significant change in the number of nodules with a size of ≤4 mm.@*Conclusions@#It is necessary to perform high-risk population screening for coal mine workers by LDCT. The follow-up strategies for nodules with a size of ≤4mm are the same as those for negative results; annual reexamination is recommended for nodules with a size of >4-8 mm, and clinical treatment should be considered for nodules with a size of >8 mm.

The feasibility study of low-dose CT scanning in chest tumor with 125I radioactive seed implantation / 中华放射医学与防护杂志

Objective To investigate the feasibility of reducing CT scanning dose in the process of 125I radioactive seed implantation.Methods GEMS phantom and 062 M phantom were scanned using GE Lightspeed RT large hole CT with 120 kV,100 kV and 80 kV separately,and 150-10 mA (20 mA decreased progressively).The scanning dose,CT value and noise of the region of interest were recorded and the image quality was evaluated.Image signal-to-noise ratio (SNR) and contrast to noise ratio (CNR) values were calculated.Results With the decreasing of tube voltage and current,the SNR values were reduced accorgingly.The values had significant difference with those of standard images except the images acquired with 120 kV,150-70 mA and 100 kV,150-90 mA (t =-9.294-3.717,P ＜0.05).With the decreasing of the tube voltage and current,the CNR decreased significantly.The image quality was too low to evaluate while CNR lower than 2.The high contrast resolution of the CT images were not affected obviously with the tube voltage and current lowering.Conclusions In the process of 125I radioactive seed implantation,it is feasible to choose lower tube voltage and tube current(100 kV,70 mA) to scan the same area repeatedly except for the first scan with standard chest scanning parameters.The patient radiation dose has fallen dramatically.

Low-dose computed tomography screening for lung cancer in Tianjin: a preliminary clinical analysis of baseline screening and follow-up results / 中国肿瘤临床

Objective:To explore the efficacy of low-dose computed tomography (LDCT) baseline and follow-up scans of lung cancer screening and to analyze lung nodules and other thoracic lesions detected from baseline and follow-up. Methods:A total of 650 sub-jects were enrolled in the LDCT lung cancer screening program, and investigators mainly focused on the analysis of 548 subjects who participated in the follow-up scan. The investigators recorded the nodules and other lesions of baseline screening, compared them with the follow-up images, and recorded their progress. Results:A total of 101 subjects were positive in the baseline screening, with a positivity rate of 18.4%. Six cases of lung cancer were confirmed by pathology, with a detection rate of 0.92%(6/650). The detection rate of lung cancer in female non-smokers (1.59%) was higher than that in male smokers (1.04%) without significant difference (P=0.624). Detected in the follow-up scan were 19 cases of new nodule-positive subjects. The positive rate for new nodules was 3.5%(19/548). The difference between the three-and two-dimensional levels was statistically significant. Conclusion:The effect of LDCT screen-ing for early lung cancer is significant. The detection rate in female non-smokers was not significantly higher than that in male smok-ers. Thus, LDCT lung cancer screening is equally significant for both sexes. The computer-aided detection (CAD) volume measurement technique is better to evaluate the progress of nodules during the follow-up interval.

Performance of Half-dose Chest Computed Tomography in Lung Malignancy Using an Iterative Reconstruction Technique / 고신대학교의과대학학술지

OBJECTIVES: The purpose of this study was to evaluate the performance of half-dose chest CT using an iterative reconstruction technique in patients with lung malignancies. METHODS: The Dual-source CT scans were obtained and half-dose datasets were reconstructed with 5 different strengths in 38 adults with lung malignancies. Two radiologists graded subjective image quality; noise, contrast and sharpness at the central/peripheral lung, mediastinum and chest wall of the reconstructed half-dose images, compared with those of standard-dose images, using a three-point scale. A lesion assessment; lesion conspicuity and diagnostic confidence, was also performed. The quantitative image noises; contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were measured and compared with those of standard-dose images. RESULTS: The subjective image noise in the half-dose images was less than that of the standard-dose images. The contrast in strengths 2 to 5 was superior, the sharpness of the lung parenchyma in strengths 3 to 5 was inferior, and the CNR/SNR in all strengths were higher than those of standard-dose images (P < 0.05). The improvement of subjective image noise and contrast, the decrease in sharpness, were correlated with strength level (P < 0.05). The lesion conspicuity in half-dose images of strengths 4 and 5 was decreased. The diagnostic confidence of the half-dose images of all strengths was comparable to that of the standard-dose images (P < 0.05). CONCLUSIONS: Half-dose chest CT images using an iterative reconstruction technique show decreased image noise, increased contrast, and diagnostic confidence comparable to standard-dose images. Images reconstructed with strength 2 and 3 appear to be the optimal choice in clinical practice.

The role of low dose CT as part of the same 18F-NaF PET/CT in detecting bone metastases in lung cancer / 实用医学杂志

Objective Retrospectively evaluate low dose computed tomography (CT) as part of a combined 18F-NaF positron emission tomography (18F-NaFPET/CT) examination in lung cancer patients suspected of bone metastases. Methods 118 of 122 lesions with increased uptake of 18F-NaF were assessed. Characteristics of bone metastases on CT images were reviewed by radiologists. Results 27 of 47 metastases presented as sites of increased uptake with corresponding lytic or sclerotic changes on low dose CT. Other 20 show normal or non-specific appearing bone on CT. Most benign lesions (67 of 71,94%)have a benign appearance on low-dose CT. Conclusions Low dose CT images were useful in precisely diagnosing bone metastasis. Negative low dose CT appearance to the abnormal foci on PET may be a reliable sign of metastases.

Unenhanced low-dose versus standard-dose CT localization in patients with upper urinary calculi for minimally invasive percutaneous nephrolithotomy (MPCNL.

Background & objectives: With the ethical concern about the dose of CT scan and wide use of CT in protocol of suspected renal colic, more attention has been paid to low dose CT. The aim of the present study was to make a comparison of unenhanced low-dose spiral CT localization with unenhanced standard-dose spiral CT in patients with upper urinary tract calculi for minimally invasive percutaneous nephrolithotomy (MPCNL) treatment. Methods: Twenty eight patients with ureter and renal calculus, preparing to take MPCNL, underwent both abdominal low-dose CT (25 mAs) and standard-dose CT (100 mAs). Low-dose CT and standard-dose CT were independently evaluated for the characterization of renal/ureteral calculi, perirenal adjacent organs, blood vessels, indirect signs of renal or ureteral calculus (renal enlargement, pyeloureteral dilatation), and the indices of localization (percutaneous puncture angulation and depth) used in the MPCNL procedure. Results: In all 28 patients, low-dose CT was 100 per cent coincidence 100 per cent sensitive and 100 per cent specific for depicting the location of the renal and ureteral calculus, renal enlargement, pyeloureteral dilatation, adjacent organs, and the presumptive puncture point and a 96.3 per cent coincidence 96 per cent sensitivity and 93 per cent specificity for blood vessel signs within the renal sinus, and with an obvious lower radiation exposure for patients when compared to standard-dose CT (P<0.05). The indices of puncture depth, puncture angulation, and maximum calculus transverse diameter on the axial surface showed no significant difference between the two doses of CT scans, with a significant variation in calculus visualization slice numbers (P<0.05). Interpretation & conclusions: Our findings show that unenhanced low-dose CT achieves a sensitivity and accuracy similar to that of standard-dose CT in assessing the localization of renal ureteral calculus and adjacent organs conditions and identifying the maximum calculus transverse diameter on the axial surface, percutaneous puncture depth, and angulation in patients, with a significant lower radiation exposure, who are to be treated by MPCNL, and can be used as an alternative localization method.

Reconstruction of 3D model of the maxillofacial hard and soft tissues with low-dose CT / 实用口腔医学杂志

Objective:To evaluate of the feasibility of low-dose CT(LDCT)in the reconstruction of three-dimensional(3D)model of maxillofacial hard and soft tissues.Methods:Lightspeed 16-slice spiral CT scanner was used to scan one adult cadaveric head specimens with conventional parameters(280 mA)and low dose parameters(200,150,100,50,35,25,15 and 5 mA)respectively;the 3D model of the hard and soft tissues were reconstructed with Mimics 10.01 software,and 3D comparison were carried on with Geomagic 11.0 software.A comparison of the surface morphology of the hard and soft tissues of the 3D models with different scanning parameters was made.Results:With the reduction of the tube current,the model surface became rough gradually.Compared with the 280 mA scan results,the model surface produced by 35 mA scanning was still fairing,when the dose fell to less than 25 mA,the model surface became rough and the exact shape of the model could not be recognized.The same results of model surface were pro-duced after registration.Conclusion:The low-dose (35 mA)CT can be used to reconstruct 3D model of the maxillofacial hard and soft tissues.

Ultra-Low-Dose Chest CT in Patients with Neutropenic Fever and Hematologic Malignancy: Image Quality and Its Diagnostic Performance / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The aim of this study was to evaluate the image quality of ultra-low-dose computed tomography (ULDCT) and its diagnostic performance in making a specific diagnosis of pneumonia in febrile neutropenic patients with hematological malignancy. MATERIALS AND METHODS: ULDCT was performed prospectively in 207 febrile neutropenic patients with hematological malignancy. Three observers independently recorded the presence of lung parenchymal abnormality, and also indicated the cause of the lung parenchymal abnormality between infectious and noninfectious causes. If infectious pneumonia was considered the cause of lung abnormalities, they noted the two most appropriate diagnoses among four infectious conditions, including fungal, bacterial, viral, and Pneumocystis pneumonia. Sensitivity for correct diagnoses and receiver operating characteristic (ROC) curve analysis for evaluation of diagnostic accuracy were calculated. Interobserver agreements were determined using intraclass correlation coefficient. RESULTS: Of 207 patients, 139 (67%) had pneumonia, 12 had noninfectious lung disease, and 56 had no remarkable chest computed tomography (CT) (20 with extrathoracic fever focus and 36 with no specific disease). Mean radiation expose dose of ULDCT was 0.60+/-0.15 mSv. Each observer regarded low-dose CT scans as unacceptable in only four (1.9%), one (0.5%), and three (1.5%) cases of ULDCTs. Sensitivity and area under the ROC curve in making a specific pneumonia diagnosis were 63.0%, 0.65 for reader 1; 63.0%, 0.61 for reader 2; and 65.0%, 0.62 for reader 3; respectively CONCLUSION: ULDCT, with a sub-mSv radiation dose and acceptable image quality, provides ready and reasonably acceptable diagnostic information for pulmonary infection in febrile neutropenic patients with hematologic malignancy

Evaluation of Ultra-Low Dose CT in the Diagnosis of Pediatric-Like Fractures Using an Experimental Animal Study

OBJECTIVE: The aim of this prospective study was to evaluate the performance of ultra-low dose CT for the diagnosis of pediatric-like fractures and ascertain the lowest dose level sufficient for diagnostics. MATERIALS AND METHODS: Fifty-one bones of young pig cadavers were artificially fractured and subsequently examined by using a 64 multi-detector CT with 36 various dose levels down to a dose comparable with that of X-rays. Two pediatric radiologists analysed the CT scans according to the presence or absence of a fracture, determination of the fracture type and the displacement as well as the diagnostic certainty. For each dose protocol, a success rate for the correct determination of the above-mentioned CT analyses was calculated. A success rate of at least 95% was considered sufficient for diagnostics. RESULTS: All but the lowest dose levels were sufficient to identify the fracture. Only the two lowest dose levels were insufficient to detect the fracture type. All dose levels were adequate for the identification of the displacement. The lowest dose level sufficient for diagnostics was 120 kVp, 11 mAs, and pitch 1.5, with a CTDIvol of 10% of a standard dose and an effective dose three times as large as that of X-rays. CONCLUSION: Ultra-low dose CT provides the feasibility of a significant dose reduction, still allowing sufficient diagnostics of pediatric-like fractures.

CT Radiation Dose Optimization and Estimation: an Update for Radiologists

In keeping with the increasing utilization of CT examinations, the greater concern about radiation hazards from examinations has been addressed. In this regard, CT radiation dose optimization has been given a great deal of attention by radiologists, referring physicians, technologists, and physicists. Dose-saving strategies are continuously evolving in terms of imaging techniques as well as dose management. Consequently, regular updates of this issue are necessary especially for radiologists who play a pivotal role in this activity. This review article will provide an update on how we can optimize CT dose in order to maximize the benefit-to-risk ratio of this clinically useful diagnostic imaging method.