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Objective To evaluate the impact of deep learning reconstruction algorithm on the image quality of head and neck CT angiography (CTA) at 100 kVp. Methods CT scanning was performed at 100 kVp for the 37 patients who underwent head and neck CTA in PUMC Hospital from March to April in 2021.Four sets of images were reconstructed by three-dimensional adaptive iterative dose reduction (AIDR 3D) and advanced intelligent Clear-IQ engine (AiCE) (low,medium,and high intensity algorithms),respectively.The average CT value,standard deviation (SD),signal-to-noise ratio (SNR),and contrast-to-noise ratio (CNR) of the region of interest in the transverse section image were calculated.Furthermore,the four sets of sagittal maximum intensity projection images of the anterior cerebral artery were scored (1 point:poor,5 points:excellent). Results The SNR and CNR showed differences in the images reconstructed by AiCE (low,medium,and high intensity) and AIDR 3D (all P<0.01).The quality scores of the image reconstructed by AiCE (low,medium,and high intensity) and AIDR 3D were 4.78±0.41,4.92±0.27,4.97±0.16,and 3.92±0.27,respectively,which showed statistically significant differences (all P<0.001). Conclusion AiCE outperformed AIDR 3D in reconstructing the images of head and neck CTA at 100 kVp,being capable of improving image quality and applicable in clinical examinations.
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Humans , Computed Tomography Angiography/methods , Radiation Dosage , Deep Learning , Radiographic Image Interpretation, Computer-Assisted/methods , Signal-To-Noise Ratio , AlgorithmsABSTRACT
Objective:To evaluate the effects of split-filter dual-energy CT (SF-DECT) in improving image quality at low doses in the process of abdominal examinations for children.Methods:A preliminary study was conducted using child phantoms. Furthermore, 20 children aged 4-6 years were recruited prospectively for clinical validation from June 2020 to December 2020. Conventional single-energy CT (SECT) and SF-DECT were employed to scan the abdominal areas of the phantoms and children. Then, the CT values, image noise, contrast to noise ratios (CNRs), and image subjective scores of SF-DECT and SECT were compared under various doses (1, 2, 3, and 4 mGy).Results:For the phantoms under doses of 3 and 4 mGy, SF-DECT decreased the image noise by 18.9% and 23.6%, respectively, and increased the liver and kidney CNRs (CNR liv and CNR kid) by 12.8% and 31.9% at most, respectively, compared to SECT ( Z = 3.00, 5.17, P < 0.001). For children, SF-DECT decreased image noise ( Z = 4.64, P < 0.001) and increased CNR liv and CNR kid ( Z = 3.78, 3.39, P < 0.001). For both the phantoms and the children, the subjective scores of images scanned using the SF-DECT were higher than those scanned using the SECT ( Z = 1.96-3.80, P < 0.05). Conclusions:Compared with SECT, SF-DECT can improve the quality of children′s abdominal images. This technique has a certain prospect of optimizing abdominal CT for children. However, it is necessary to conduct in-depth clinical research to verify the result.
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Objective:To compare the differences in radiation dose and image quality between cone-beam CT (CBCT) and multi-slice spiral CT (MSCT) applied to atlantoaxial spine imaging.Methods:Head and neck phantom was scanned at 30 exposure parameter combinations using Pramerica CBCT scanner and 15 parameter combinations using Toshiba 320-row MSCT. The effective dose ( E) of CBCT was calculated based on the Monte Carlo dose estimation software PCXMC, the E value of MSCT was obtained by multiplying the dose length product (DLP) by the related factor. t-test for two independent samples or Wilcoxon rank sum test were used for comparison of radiation dose and subjective and objective image quality between two modalities. The subjective evaluation was a 5-point subjective scale using double-blind method for edge sharpness, contrast, soft tissue level, and artifacts of the images. The signal and noise in the region of interest (ROI) were measured and the contrast signal-to-noise ratio (CNR) was calculated. Results:For radiation dose, the volumetric dose index and E values of 2.9 mGy and 27.61 μSv for CBCT were lower than those of 8.8 mGy and 433.16 μSv for MSCT, and the differences were statistically significant( z=-3.05, -5.25, P<0.05). For objective evaluation of image quality, the noise and CNR were 27.74 HU and 3.69 in CBCT group, 7.84 HU and 27.1 in MSCT group. The difference between them were statistically significant( z=-5.39, -5.42, P<0.05). The overall image quality, contrast and artifact scores of the CBCT group were 3.5, 3.0 and 5 were higher than those of the MSCT group at 2.0, 2.0, and 4.0, respectively ( z=-2.32, -2.46, -3.31, P<0.05). Conclusions:Both atlantoaxial CBCT and MSCT scans provide image quality that meets diagnostic requirements. Compared to MSCT, CBCT atlantoaxial scans can effectively reduce radiation dose according to the principle of optimization of radiation protection.
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Objective:To synthesize non-contrast-enhanced CT images from enhanced CT images using deep learning method based on convolutional neural network, and to evaluate the similarity between synthesized non-contrast-enhanced CT images by deep learning(DL-SNCT) and plain CT images considered as gold standard subjectively and objectively, as well as to explore their potential clinical value.Methods:Thirty-four patients who underwent conventional plain scan and enhanced CT scan at the same time were enrolled. Using deep learning model, DL-SNCT images were generated from the enhanced CT images for each patient. With plain CT images as gold standard, the image quality of DL-SNCT images was evaluated subjectively. The evaluation indices included anatomical structure clarity, artifacts, noise level, image structure integrity and image deformation using a 4-point system). Paired t-test was used to compare the difference in CT values of different anatomical parts with different hemodynamics (aorta, kidney, liver parenchyma, gluteus maximus) and different liver diseases with distinct enhancement patterns (liver cancer, liver hemangioma, liver metastasis and liver cyst) between DL-SNCT images and plain CT images. Results:In subjective evaluation, the average scores of DL-SNCT images in artifact, noise, image structure integrity and image distortion were all 4 points, which were consistent with those of plain CT images ( P>0.05). However, the average score of anatomical clarity was slightly lower than that of plain CT images (3.59±0.70 vs. 4) with significant difference ( Z = -2.89, P<0.05). For different anatomical parts, the CT values of aorta and kidney in DL-SNCT images were significantly higher than those in plain CT images ( t=-12.89, -9.58, P<0.05). There was no statistical difference in the CT values of liver parenchyma and gluteus maximus between DL-SNCT images and plain CT images ( P>0.05). For liver lesions with different enhancement patterns, the CT values of liver cancer, liver hemangioma and liver metastasis in DL-SNCT images were significantly higher than those in plain CT images( t=-10.84, -3.42, -3.98, P<0.05). There was no statistical difference in the CT values of liver cysts between DL-SNCT iamges and plain CT images ( P>0.05). Conclusions:The DL-SNCT image quality as well as the CT values of some anatomical structures with simple enhancement patterns is comparable to those of plain CT images considered as gold-standard. For those anatomical structures with variable enhancement and those liver lesions with complex enhancement patterns, there is still vast space for DL-SNCT images to be improved before it can be readily used in clinical practice.
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Objective:To analyze the conventional quality control result of Leksell Icon Gamma Knife cone-beam CT and evaluate long-term stability of cone-bem CT.Methods:QA TOOL Plus was used to verify the accuracy of cone-beam CT. The phantom Catphan 503 was scanned, and the image spatial resolution, contrast to noise ratio and homogeneity were analyzed.Results:The maximum deviation in image volume of cone-beam CT was 0.09-0.17 mm, which passed the accuracy test. At the scanning patterns with CT dose index of 2.5 and 6.3 mGy, the spatial resolution was very stable at 7 and 8 lp/cm respectively. The contrast noise ratio and uniformity meet the reference requirements.Conclusions:The conventional quality control results of Leksell Icon Gamma Knife cone-beam CT are stable in 12 months. In addition to referring to the manufacturer′s baseline value, the unified analysis and evaluation standard for Gamma Knife need to be further improved for the quality control of cone-beam CT.
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Objective:To evaluate the influence of different detector widths and signal acquisition positions of wide-detector CT in different scanning modes on CT number and noise, and to provide a basis for reasonable selection of scanning modes and related parameters in clinical practice.Methods:The body dose phantom was scanned by GE Revolution CT. The scan was performed with detector widths of 40, 80 and 160 mm in sequential scanning mode and with detector width/pitch combinations of 40 mm/0.516, 40 mm/0.984, 80 mm/0.508 and 80 mm/0.992 in spiral scanning mode. The phantom was placed at the central and peripheral of the selected detector widths, and the adjacent positions between two axial scans. The images of the phantom were evaluated subjectively and the CT numbers and SDs were measured. The differences between the measured values at different imaging parameters were compared. The multi-group Friedman test was used to compare CT numbers and SD under different scanning parameters in sequential scanning mode, and the Wilcoxon test was used to compare CT numbers and SD in spiral scanning mode.Results:There was no statistically significant difference in the geometric shapes of the phantom images obtained at any combination of parameters. In sequential scanning mode, the differences at different detector widths were statistically significant (χ 2=14.00, P=0.001) with CT numbers at 40 mm and 160 mm greater than CT numbers at 80 mm ( P<0.05). The differences at different signal acquisition positions were statistically significant (χ 2=12.04, P=0.002) with CT numbers at peripheral and adjacent greater than CT numbers at central ( P<0.05). In spiral scanning mode CT numbers at detector width at 80 mm were greater than CT numbers at 40 mm ( Z=-2.10, P=0.036). For SD, the differences at different detector widths were statistically significant in sequential scanning modes (χ 2=8.17, P=0.017) with SD at 160 mm greater than SD at 80 mm ( P<0.05). The differences at different signal acquisition positions were statistically significant (χ 2=13.50, P=0.001) with SD at peripheral greater than SD at central ( P<0.05). In spiral scanning mode SDs at pitches 0.984 and 0.992 were greater than SDs at 0.516 and 0.508 ( Z=-2.66, P=0.008). There were no significant differences among other groups. Conclusion:The selection of scanning mode, detector width and signal acquisition position of wide-detector CT will affect the image CT numbers and SDs.
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Objective:To explore the value of echo-planar imaging correction (EPIC) for improving image quality of diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI) of cervical cord.Methods:A total of 33 subjects (20 males, 13 females) were scanned on a 3.0 T MR scanner from January to March 2022, and the sequences included T 1WI, DWI and DTI (with and without corrections). Two observers delineated the regions of interest (ROIs) on the fused images of DWI and DTI with T 1WI before and after correction, and measured the average diffusion coefficient (ADC), fractional anisotropy (FA), and offset distance of ROIs between images with and without corrections. The subjective scores of image quality were also evaluated. The ICC or Kappa was used to test the consistency of the quantitative measurement and subjective scores by the two observers. The average values by the two observers would be used for subsequent analysis. The independent pair t-test and Wilcoxon test were used for comparison of objective measurements and Mann-Whitney U test was used for subjective image assessments between images with and without corrections. Results:The measurement data and the subjective scores of the two observers were in good agreement (ICC 0.912-0.999, Kappa 0.778-0.816). The independent sample t-test showed the subjective scores were significantly different for the DWI and DTI images between before and after geometry and/or ADC corrections. The ADC values of C6, the offset distances measured by DWI before and after correction of C4, C5, and C6 and subjective scores were significantly different ( P<0.05); The FA values of C1 and C3, ADC values of C1 and C3, offset distance of C4, C5 and C6 measured by DTI before and after correction and subjective scores were statistically significant ( P<0.001). Conclusion:EPI geometry correction and ADC value correction can significantly reduce geometric distortion, increase image quality, and thus improve the diagnosis accuracy of essential diseases.
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Objective:To explore the image quality and its evaluation method using virtual grid under different tube voltages in the clinical chest X-ray exam.Methods:According to the conditions of chest X-ray photography commonly used in clinical practice, the corresponding thickness of plexiglass (20 cm, including CDRAD phantom) was determined as the experimental object. With a fixed tube loading of 4 mAs and the tube voltage from 60 to 125 kV, the experimental object was imaged in three ways: physical grid, none grid and virtual grid. The common physical parameters (CNR, σ, C, SNR), texture analysis (Angular second moment, texture Contrast, Correlation, Inverse difference moment, Entropy) and CDRAD phantom score (IQF inv) were evaluated. Two-way ANOVA test was used for each group of common physical parameters, and further pairwise comparisons were made. At the same time, applying virtual grids on the obtained images with chest anthropomorphic model and texture indexing the images with and without virtual grids, then rank sum test of paired sample can be conducted. Results:There were differences in image quality among the three groups of grid mode( P<0.05), and the physical grid delivered the best image quality. The tube voltage had an impact on all image quality evaluation indexes ( P<0.05). The tube voltage was positively correlated with CNR, SNR, angular second moment, inverse difference moment and IQF inv ( P<0.05), and negatively correlated with σ, C, texture contrast and entropy ( P<0.05). There was no significant correlation between the tube voltage and Correlation ( P>0.05). The chest anthropomorphic model images were used to evaluate the virtual grids, and the texture indexes (Angle second moment, Contrast, Correlation, Inverse difference moment, Entropy) were statistically significant (P<0.05). Conclusions:The virtual grid can improve the image quality of chest X-ray photography, and the image texture analysis method can be a useful supplement to the image quality evaluation parameters.
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Objective:To investigate the effect of adjusting density exposure steps on image quality and radiation dose in digital mammography.Methods:Using the automatic exposure control (AEC) mode of the digital mammography machine, five different gland thicknesses of 4.3, 5.3, 6.3, 7.3, and 8.3 cm were simulated by attaching 0, 1, 2, 3, and 4 PMMA plexiglass plates under the RMI-156 modal body, and the density exposure steps were adjusted to -3, -2, -1, 0, 1, 2, 3, and 4 for each thickness. The target/filter combination, tube voltage, tube current, incident body surface dose (ESD), incident surface air kerma (ESAK), half-value layer (HVL) and the average glandular dose displayed by the device (displayed AGD) were recorded at each step and thickness, and the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), figure of merit (FOM) and the calculated average glandular dose (calculated AGD) were calculated. Then, the display effects of simulated fibers, simulated calcifications and simulated masses within the modal body were scored subjectively, and the changes in image quality and radiation dose at different steps were analyzed, and the relationships between ESD and ESAK, displayed AGD and calculated AGD, and displayed AGD/ESD and calculated AGD/ESAK were analyzed. A linear fit was used for the steps with SNR, CNR, and FOM, and an exponential function curve fit was used for the steps with mAs, ESAK, and calculated AGD. The differences between ESD and ESAK, displayed AGD and calculated AGD, and displayed AGD/ESD and calculated AGD/ESAK were analyzed by paired-samples t test. Results:The CNR and SNR of mammographic images rose and fell by about 8% with each increase or decrease of one step. The scores of image simulated fibers, simulated calcifications, and simulated masses showed an overall upward trend with increasing steps, but there were still cases where the scores decreased with increasing grades. FOM varied from 97% to 104% at each grade with little variability. ESD, ESAK, displayed AGD, and calculated AGD, which could measure radiation dose, showed an exponential trend of increasing function with increasing steps, with a variation of about 63% to 165%. There were statistically significant differences ( t=-9.61, P=0.001) between ESD (15.14±10.08) and ESAK (16.66±11.07). However, there were no statistically significant differences ( t=1.20, P=0.240) between displayed AGD and calculated AGD, which were 3.66±2.18 and 3.61±1.99, respectively. Conclusions:The adjustment of density exposure steps can make the image quality change linearly and the radiation dose change exponentially with increasing speed, and the mode and magnitude of the adjustment are appropriately stable with high application value.
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Objective:To explore the impact of coronary CT angiography (CCTA) image quality and related factors on the diagnostic performance of CT-derived fractional flow reserve (CT-FFR).Methods:Based on the CT-FFR CHINA trial, the prospective multicenter trial enrolled patients with suspected coronary artery disease who underwent CCTA, CT-FFR and FFR measurement. The subjective and objective assessments of CCTA image were performed on a per-vessel level. The objective assessments included the enhancement degree of coronary artery, the signal-to-noise ratio (SNR) of the aortic root. We used χ 2 test and DeLong test to compare the diagnostic performance of CT-FFR with FFR as the reference standard in different subjective groups (non-artifact vs. artifact), enhancement degree of coronary artery groups (≤400 vs. 401-500 vs.>500 HU), SNR of the aortic root groups (≤16.9 vs.>16.9), body mass index (BMI) groups (<25 kg/m 2 vs.≥25 kg/m 2) and heart rate groups (<75 bpm vs.≥75 bpm). FFR and CT-FFR values≤0.80 was identified as myocardial ischemia. Results:The study enrolled 317 patients with 366 vessels. All target vessels in CCTA images were successfully analyzed by CT-FFR. The accuracy, sensitivity, specificity, positive predictive value, negative predictive value and AUC of the non-artifact group were 90.45%, 86.75%, 93.10%, 90.00%, 90.76% and 0.928, respectively, and those of the artifact group were 83.23%, 87.21%, 79.01%, 81.52%, 85.33% and 0.869, respectively. The differences in accuracy and specificity were statistically significant (χ 2=4.23, P=0.040; χ 2=8.55, P=0.003). The diagnostic efficacy of CT-FFR had no statistically significant differences among different objective groups (all P>0.05). Conclusions:The artifact of CCTA image has an effect on CT-FFR in the diagnosis of myocardial ischemia. The degree of vascular enhancement, SNR, BMI, and heart rate have no significant effect on the diagnostic performance of CT-FFR.
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Objective:To investigate the value of the 8-channel eye surface phased array coil in improving image quality and demonstrating ocular masses on 3.0 T MR scanner.Methods:From July 2018 to January 2020, the data of orbital MRI in 692 patients with ocular masses on 6 medical centers were prospectively collected. The patients were simple randomly assigned into 8-channel eye surface phased array coil group (413 patients) or 8-channel head phased array coil group (279 patients), with the same MRI sequences. The signal to noise ratio (SNR) and contrast to noise ratio (CNR) were calculated in orbital anatomy structures and masses (eyelid mass, intraocular mass, lacrimal mass and orbital mass). The image quality scores including motion artifact, mass margin, the relationship between the mass and adjacent structures, and overall image quality were recorded. The differences of image quality between the two groups were compared by two independent sample t-test or Wilcoxon rank test. Results:The SNR and CNR were higher in eye surface coil group than those in head coil group ( P<0.05). The scores of ocular movement artifacts were higher in head coil group than those in surface coil group ( P<0.05). The scores of intraocular mass margin, the relationship between the mass and adjacent structures, and overall image quality were higher in surface coil group than those in head coil group ( P<0.001). There were no significant differences in mass margin, the relationship between the mass and adjacent structures, and overall image quality scores of eyelid, lacrimal gland, and orbital mass between the two groups ( P>0.05). Conclusion:3.0 T MR scanner combined with the 8-channel eye surface phased array coil can improve the SNR and CNR of orbital MR images, the demonstration of the intraocular mass margin and the relationship between the mass and adjacent structures.
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【Objective】 To evaluate the effect of one-beat acquisition with wide detector CT on the image quality and diagnostic efficiency of coronary CT angiography (CCTA) in patients with atrial fibrillation. 【Methods】 A total of 52 consecutive patients with atrial fibrillation, including 31 males, (67.32±11.45) years old, who underwent CCTA from July 2022 to February 2023, were analyzed retrospectively. All patients underwent one-beat acquisition CCTA. The subjective and objective image quality of the coronary arteries was evaluated, and using invasive coronary catheter angiography as the gold standard, the diagnostic efficacy of stenosis degrees above moderate and severe degrees was calculated, respectively. 【Results】 Subjective evaluation results: 92.31% (384/416) of the vascular segments were rated as excellent or good, and the diagnosable rate reached 98.08% (408/416, subjective score ≥3 points). Objective evaluation results: The CT value of the right coronary artery, anterior descending branch, and circumflex branch was (433.41±95.17)HU, (422.69±92.81)HU and (420.27±95.43)HU, respectively; the contrast-to-noise ratio was 38.46±7.54, 32.46±13.78 and 37.74±8.89, respectively. The total diagnostic accuracy, sensitivity, and specificity was 94.71%, 87.9% and 96.62%, respectively, for moderate stenosis and 96.15%, 83.64% and 98.06% for severe stenosis. 【Conclusion】 One-beat acquisition with wide detector CT can obtain high-quality coronary artery images and high diagnostic accuracy for patients with atrial fibrillation without radiation dose increase to patients. It has good clinical application value for patients with atrial fibrillation.
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Three different preclinical evaluation methods of MTF through-frequency response, MTF through-focus-response and expected visual acuity were used to compare and analyze the imaging differences of IOLs with four different optical designs. The research work could be used in the simultaneous vision IOLs in the optical design stage and verify the optical quality of the IOLs, the results can predict the visual representation of the patients better. The evaluation results can provide reference for IOL manufacturers and users in product design, development, validation and application selection.
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Humans , Prosthesis Design , Lenses, Intraocular , Vision, Ocular , Visual AcuityABSTRACT
Background@#Myocardial perfusion scintigraphy images with iterative reconstruction showed higher qualitative and quantitative estimates. @*Objective@#This study was conducted to compare image quality, diagnostic accuracy, and LV parameters with standard FBP versus OSEM as baseline quality assurance for the choice of reconstruction algorithm most applicable in the local setting. @*Methods@#This was a retrospective cross-sectional study of 55 Thallium-201 (Tl-201) scans and 14 Techentium-99m sestamibi (Tc-99m) images that were reprocessed with filtered backprojection (FBP) and with ordered subset expectation maximization (OSEM). The image quality, diagnostic accuracy, and LV parameters of both SPECT reconstructions were compared.@*Results@#OSEM reconstruction resulted in a significantly smooth background tracer activity as opposed to the standard FBP in both Tl-201 (p<0.01) and Tc-99m (p=0.01) scans. Distinct LV border was superiorly seen in OSEM. There was no significant difference in the diagnostic accuracy between the two reconstruction parameters despite 2 cases of interpretation discrepancies. End-diastolic volume generated by OSEM was significantly higher (117.60+55.14 vs 118.51+55.11, p<0.01 in Tl-201 and 101.07+75.58 vs 104.29+80.39, p =0.01 in Tc-99m). With Tc-99m scans the end-systolic volume and ejection fraction in OSEM were likewise significantly different from FBP (p=0.04 and p<0.01, respectively).@*Conclusion@#OSEM reconstruction offers smooth background tracer activity with comparable diagnostic accuracy to FBP. All the LV parameters in OSEM were significantly different from FBP in Tc-99m scans and only the EDV in thallium images.
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@#Introduction: Reducing radiation dose for CT examinations has been accompanied by an increase in image noise. Studies have highlighted the application of a higher matrix size for improving image quality when assessing the lungs. This study aims to evaluate the influence of a low kVp and higher matrix size on radiation dose and image quality for abdominopelvic CT. Methods: This experiment was done on a 32 cm body phantom and scanned using a 128 slice CT scanner. The study utilised various combinations of kVp settings (140, 120, 100, 80 & 70) and matrix sizes (1024, 768 & 512). The image obtained was analysed objectively and subjectively. For objective analysis, we calculated SNR, and CNR. For subjective analysis, two radiologists evaluated the image in a 3-point scoring scale. Results: The study reported an increase in SNR (0.8%) and CNR (46%) at 120 kVp when increasing the matrix size from 512 x 512 to 768 x 768. Similarly, there was an increase of 14.5 % and 56.4 % in CNR and SNR using 1024 matrix size. The DLP was reduced by 4.5%, 50% and 70.6 % using 100, 80 and 70 kVp respectively. However, there was no change in DLP with higher matrix sizes. Conclusion: The study reported a combination of 100 kVp and 768 matrix size resulted in an almost similar (↓0.9 %) SNR and improved CNR (↑46.4 %) compared to 120 kVp and 512 matrix size. Qualitative analysis also showed a similar image quality with decreased radiation dose for abdominopelvic CT.
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Objective To compare the impact on 18F fluorodeoxyglucose （18F-FDG） positron emission tomography （PET） image quality when block sequential regularized expectation maximization （BSREM） algorithm and ordered subset expectation maximization （OSEM） algorithm were used at various acquisition times （ATs）, and to discuss the feasibility of AT optimization with BSREM algorithm. Methods In the phantom experiment, the NEMA/IEC PET phantom was adopted. In the clinical study, 66 pulmonary nodules with high uptake values from 61 patients who underwent a 18F-FDG PET-CT examination for pulmonary nodules from March to September 2020 were included. PET images were reconstructed according to BSREM algorithm and OSEM algorithm at various ATs in both the phantom experiment and the clinical study. Coefficient of variation, signal-to-noise ratio, contrast-to-noise ratio, and activity values （uptake value in the phantom experiment; standardized uptake value in the clinical study） were compared between the above sequence images for quality evaluation. Results The phantom experiment showed that the image quality of 120 s BSREM sequence was superior to that of 120 s OSEM sequence, and the image quality of 75 s BSREM sequence was similar to that of 120 s OSEM sequence. The clinical study showed that the image quality of 120 s BSREM sequence was superior to that of 120 s OSEM sequence, and the image quality of 75 s BSREM sequence was slightly better than that of 120 s OSEM sequence. Conclusion In the PET phantom experiment and the clinical study of pulmonary nodules with high uptake values, BSREM algorithm can significantly improve the image quality as compared to OSEM algorithm, and the image quality of 75 s BSREM sequence is slightly better than that of 120 s OSEM sequence.
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Objective:To analyze the effects of two decomposition algorithms of dual-energy cone beam CT (DECBCT) (direct decomposition and iterative decomposition) on the image quality and material decomposition accuracy of different sizes of phantoms.Methods:Different sizes of imaging parts of patients were simulated using the combination of CatPhan604 phantoms and customized annuluses. CBCT with high energy of 140 kVp and low energy of 100 kVp were acquired using the Varian Edge CBCT system. Then the material decomposition of DECBCT images was performed using the two algorithms. The electron density (ED) and contrast-to-noise ratio (CNR) of each material in the CTP682 module were calculated. They were used to assess the decomposition accuracy and image quality of the two algorithms.Results:Based on the values in the Catphan604 manual, both algorithms have high ED accuracy. Only the ED accuracy of four materials of the smallest sized phantom showed statistical difference ( z = -4.21, 4.30, 2.87, 5.45, P < 0.05), but the average relative error was less than 1%. The CNR of the iterative decomposition algorithm was significantly higher than that of the direct decomposition, increasing by 51.8%-703.47%. The increase in the phantom size significantly reduced the accuracy of ED, and the increased amplitude of the relative error was up to a maximum of 2.52%. The large phantom size also reduced the image quality of iterative decomposition, and the decreased amplitude of CNR was up to a maximum of 39.71. Conclusions:Compared with the direct decomposition, the iterative decomposition algorithm can significantly reduce the image noise and improve the contrast without losing the accuracy of electron density in the DECBCT construction of different sizes of phantoms.
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Objective:To investigate the effects of organ dose modulation (ODM) on image quality and radiation dose to lens during sinus CT scanning.Methods:The GE Revolution EVO CT was used to scan the anthropomorphic head with ODM turned off as the control group and ODM turned on as the observation group. With different parameter combinations of tube voltage (140, 120, 100 kV), noise index (N17, N18), pitch (0.531, 0.969 at 20 cm collimation width, 0.516, 0.984 at 40 mm collination width), 24 series of images were acquired respectively. The tube current (mA) valuesat the anterior (A), left (L), posterior (P) and right (R) positions, volume CT dose index (CTDI vol) and dose length product (DLP) were recorded. Average CT values (AV), standard deviation (SD), signal-to-noise ratio (SNR), contrast to noise ratio (CNR) and image quality factor (FOM) of ROI were calculated. Double blind method was used to evaluate the edge sharpness, soft tissue level, noise and artifact on a subjective scale of 3 points. Results:For the combinations of different scanning parameters, the radiation dose of the observation group was lower than that of the control group. The tube current attheposition A for the observation group was lower than that of the control group, and the difference was statistically significant ( t=2.28, P<0.05). The differences oftube currentsatposotions of L, P and R, CTDI vol and DLP values in twogroupswere not statistically significant ( P>0.05). There were no significant differences in SD, SNR, CNR and FOM between the two groups of images ( P>0.05). There were no significant differences in the subjective scores of edge sharpness, soft tissue gradation, noise and artifacts between the two groups ( P>0.05). Conclusions:ODM technique can effectively reduce the radiation dose of eye lens without decompromising the image quality, which could meet the requirements of diagnosis, and accord with the principle of radiological protection optimization.
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Objective:To investigate the feasibility of chest ultra-low dose CT (ULDCT) using deep learning reconstruction (DLR) for lung cancer screening, and to compare its image quality and nodule detection rate with ULDCT iterative reconstruction (Hybrid IR) and conventional dose CT (RDCT) Hybrid IR.Methods:The patients who underwent chest CT examination for pulmonary nodules in Peking Union Medical College Hospital from October 2020 to March 2021 were prospectively included and underwent chest RDCT (120 kVp, automatic tube current), followed by ULDCT (100 kVp, 20 mA). The RDCT images were reconstructed with Hybrid IR (adaptive iterative dose reduction 3D,AIDR 3D), and ULDCT was reconstructed with AIDR3D and DLR. Radiation dose parameters and nodule numbers were recorded. Image quality was assessed using objective noise, signal-to-noise ratio (SNR) of the main trachea and left upper lobe, subjective image scores of the lung and nodules. Subjective scores were scored by 2 experienced radiologists on a Likert 5-point scale. The difference of radiation dose was compared with paired t-test between ULDCT and RDCT.The differences of quantitative indexes, objective image noise and subjective scores of the three reconstruction methods were compared with one-way analysis of variance or Friedman test. Results:Forty-five patients were enrolled, including 17 males and 28 females, aged from 32 to 74 (55±11) years. The radiation dose of ULDCT was (0.17±0.01) mSv, which was significantly lower than that of RDCT [(1.35±0.41) mSv, t=15.46, P<0.001]. There were significant differences in the image noise and SNR in the trachea and lung parenchyma and in the CT value of the trachea among ULDCT-AICE, ULDCT-AIDR 3D and RDCT-AIDR 3D images ( P<0.05). Image noise in the trachea and lung parenchyma and CT value in the trachea of ULDCT-AICE were significantly lower than those of ULDCT-AIDR 3D ( P<0.05) and comparable to RDCT-AIDR 3D ( P>0.05). There were significant differences in subjective image scores of the lung and nodules among ULDCT-AICE, ULDCT-AIDR 3D and RDCT-AIDR 3D images (χ2=50.57,117.20, P<0.001). Subjective image scores of the lung and nodules for ULDCT-AICE were significantly higher than those of ULDCT-AIDR 3D ( P<0.05), and non-inferior to RDCT-ADIR 3D ( P>0.05). All 72 clinically significant nodules detected on RDCT-ADIR 3D were also noted on ULDCT-AICE and ULDCT-AIDR 3D images. Conclusions:Chest ULDCT using DLR can significantly reduce the radiation dose, and compared with Hybrid IR, it can effectively reduce the image noise and improve SNR, and display the pulmonary nodules well. The image quality and nodule detection are not inferior to RDCT Hybrid IR routinely used in clinical practice.
ABSTRACT
Objective:To explore the effect of deep learning reconstruction (DLR) on radiation dosage reduction and image quality of CTPA compared with hybrid iterative reconstruction (HIR).Methods:A total of 100 patients with suspected pulmonary embolism (APE) or indications for CTPA due to other pulmonary artery diseases in Peking Union Medical College Hospital from December 2020 to April 2021 were prospectively enrolled and divided into HIR group and DLR group according to block randomization, with 50 cases in each group. The patient′s gender, age and body mass index (BMI) were recorded. HIR group and DLR group underwent standard deviation (SD)=8.8 and SD=15 CTPA protocols in combination with HIR and DLR algorithm respectively. Other scanning parameters and contrast medium injection plan were the same. The effective dose (ED) and size-specific dose estimate (SSDE) were calculated. Regions of interest (ROIs) were drawn in the lumen of Grade 1-3 pulmonary arteries and bilateral paravertebral muscles. The corresponding CT and SD values were recorded to acquire signal to noise ratio (SNR) and contrast noise ratio (CNR). Based on a double-blind method, two radiologists evaluated the subjective noise, visualization of pulmonary arteries, and diagnostic confidence of the two groups by 5-point Likert scales. The inconsistent results were judged comprehensively by the third radiologist. Independent samples t-test was used to compare the demographic data, radiation dosage and quantitative image quality of the two groups. Mann-Whitney U test was used to compare the subjective noise, visualization of pulmonary arteries and diagnostic confidence between the two groups. Linear weighted Kappa coefficient was calculated to analyze the consistency of the qualitative scores between the two radiologists. Results:There were no significant differences in gender, age and BMI between the two groups ( P>0.05). The CT values of Grade1-3 pulmonary arteries and paravertebral muscle had no significant differences ( P>0.05). Compared with HIR group, the ED and SSDE in DLR group decreased by about 35% to 1.3 mSv and 4.20 mGy respectively, while the SNR (30±5) and CNR (26±5) of CTPA images were higher in DLR group than those in HIR group (23±5 and 20±5, with t=-6.60 and -5.90, respectively, both P<0.001). The subjective noise score was higher in DLR group than that in HIR group ( Z=-7.34, P<0.001). In addition, two radiologists showed excellent interobserver agreement in DLR group (Kappa=0.847, 95%CI 0.553-1.000). No significant differences were found in visualization of pulmonary arteries and diagnostic confidence between the two groups ( P>0.05). Conclusion:DLR further reduced the radiation dosage and improved the image quality of CTPA, with no detriment to diagnostic confidence. Thus DLR is worthy of clinical promotion.