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1.
    
The aim of this work was to research and evaluate the performance of three different digital breast tomosynthesis (DBT) systems in the clinical environment (Siemens Mammomat Inspiration, Hologic Selenia Dimensions, and Fujifilm Amulet Innovality). The characterization included the study of the detector, the automatic exposure control, and the resolution of DBT projections and reconstructed planes.The modulation transfer function (MTF) of the DBT projections was measured with a 1 mm thick steel edge, showing a strong anisotropy (30–40% lower MTF0.5 frequencies in the tube travel direction). The in-plane MTF0.5, measured with a 25 μm tungsten wire, ranges from 1.3 to 1.8 lp/mm in the tube-travel direction and between 2.4 and 3.7 lp/mm in the chest wall–nipple. In the latter direction, the MTF peak shift is more emphasized for large angular range systems (2.0 versus 1.0 lp/mm). In-depth resolution of the planes, via the full width at half maximum (FWHM) from the point spread function of a 25 μm tungsten wire, is not only influenced by angular range and yields 1.3–4.6 mm among systems. The artifact spread function from 1 mm diameter tungsten beads depends mainly on angular range, yielding two tendencies whether large (FWHM is 4.5 mm) or small (FWHM is 10 mm) angular range is used. DBT delivers per scan a mean glandular dose between 1.4 and 2.7 mGy for a 45 mm thick polymethyl methacrylate (PMMA) block.In conclusion, we have identified and analysed specific metrics that can be used for quality assurance of DBT systems.  相似文献   

2.
    
A comparison, in terms of the optimal energy that maximizes the image quality between digital breast tomosynthesis (DBT) and digital mammography (DM) was performed in a MAMMOMAT Inspiration system (Siemens) based on amorphous selenium flat panel detector. In this paper we measured the image quality by the signal difference-to-noise ratio (SDNR), and the patient risk by the mean glandular dose (MGD). Using these quantities we compared the optimal voltage that maximizes the image quality both in breast tomosynthesis and standard mammography acquisition mode. The comparison for the two acquisition modes was performed for a W/Rh anode filter combinations by using a 4.5 cm tissue equivalent mammography phantom. Moreover, in order to check if the used equipment was quantum noise limited, the relation of the relative noise with respect to the detector dose was evaluated. Results showed that in the tomosynthesis acquisition mode the optimal voltage is 28 kV, whereas in standard mammography the optimal voltage is 30 kV. The automatic exposure control (AEC) of the system selects 28 kV as optimal voltage both for DBT and DM. Monte Carlo simulations showed a qualitative agreement with the AEC selection system, since an optimal monochromatic energy of 20 keV was found both for DBT and DM. Moreover, the check about the noise showed that the system is not completely quantum noise limited, and this issue could explain the experimental slight difference in terms of optimal voltage between DBT and DM. According to these results, the use of higher voltage settings is not justified for the improvement of the image quality during a DBT examination.  相似文献   

3.
    
A tracking and reporting system was developed to monitor radiation dose in X-ray breast imaging. We used our tracking system to characterize and compare the mammographic practices of five breast imaging centers located in the United States and Brazil. Clinical data were acquired using eight mammography systems comprising three modalities: computed radiography (CR), full-field digital mammography (FFDM), and digital breast tomosynthesis (DBT). Our database consists of metadata extracted from 334,234 images. We analyzed distributions and correlations of compressed breast thickness (CBT), compression force, target-filter combinations, X-ray tube voltage, and average glandular dose (AGD). AGD reference curves were calculated based on AGD distributions as a function of CBT. These curves represent an AGD reference for a particular population and system. Differences in AGD and imaging settings were attributed to a combination of factors, such as improvements in technology, imaging protocol, and patient demographics. The tracking system allows the comparison of various imaging settings used in screening mammography, as well as the tracking of patient- and population-specific breast data collected from different populations.  相似文献   

4.
摘要 目的:探讨乳腺三维断层技术(DBT)结合乳腺超声(BUS)对致密型乳腺病变的诊断价值。方法:回顾分析2018年6月至2019年4月在我院就诊且有完整病理结果的149例致密型乳腺病变患者的影像资料,对比DBT、BUS两种检查方法的检出率;以病理结果为金标准,分析DBT、BUS、DBT联合BUS三种检查模式的诊断效能。结果:BUS对良性病变的检出率(97.87%)高于DBT(89.36%),差异有统计学意义(x2=5.697,P<0.05);DBT与BUS对恶性病变的检出率分别为98.44%、95.31%,差异无统计学意义(x2=1.032,P>0.05)。DBT诊断致密型乳腺病变的敏感度为90.61%、特异度为93.55%、准确率为91.77%,BUS诊断致密型乳腺病变的敏感度为78.13%、特异度为89.36%、准确率为84.81%,DBT联合BUS诊断致密型乳腺病变的敏感度为95.31%、特异度为95.74%、准确率为95.57%。DBT联合BUS诊断致密型乳腺恶性病变的受试者工作特征曲线(ROC)的曲线下面积(AUC)为0.977,稍高于DBT的AUC(0.951),明显高于BUS的AUC(0.885)。结论:BUS对良性病变的检出率显著高于DBT,DBT对致密型乳腺病变的诊断效能高于BUS,二者结合能提高病变的检出率与诊断效能。  相似文献   

5.
    
This study proposes digital breast tomosynthesis (DBT) as a low-tube-voltage method for imaging wood artifacts treated with polyethylene glycol (PEG). In case of general clinical X-ray Computed Tomography (X-CT), PEG-impregnated wood images typically suffer from low contrast between the PEG and the tree-ring. Because X-CT uses high-tube-voltage X-rays that have high energy, they are transmitted regardless of the X-ray absorption difference of the substance, and therefore, it is not suitable for imaging PEG-impregnated wood. Mammography uses low-tube-voltage X-rays, and therefore, it is suitable for delineating substances with small X-ray absorption differences. However, although mammography can produce high-contrast images of wood, it cannot distinguish three-dimensional (3D) structures such as tree rings, because those are projection images. DBT is a type of mammography used to enhance contrast using low-tube voltage, and it enables imaging 3D structures by exposure X-rays to objects several times changing the exposure angle, and it can obtain quasi-computed tomography. Therefore, we believe that by applying DBT to dendroarchaeology, it would be possible to obtain high-contrast, high-resolution images in the visualization of the internal structure of wood.In this study, we used clinical X-CT, mammography, and DBT to obtain images of wood after PEG impregnation, and we evaluated the internal structure of the wood and the visibility of annual rings. We obtained DBT images as a tomogram with a thickness of 1 mm, which eliminated the distortion of tree rings in the sagittal direction and duplication of the PEG and the tree-ring. Further, tree-rings were easily visualized without a noticeable blur, and the DBT contrast was improved compared to clinical X-CT contrast because DBT was performed at low voltage. Important wooden artifacts excavated from ruins were preserved by PEG. Therefore, this method can be expected to become a very useful tool for dendroarchaeology when used as a complementary tool for microfocus X-CT.  相似文献   

6.
    
PurposeOptimization studies in digital mammography aid to assure the image quality and radiological protection of the patient. The aim of this work is to test effectiveness and applicability of a method based on a Figure of Merit (FOM = (IQFinv)2/AGD) to improve all the exposure parameters (Target/Filter combination, kVp and mAs) in order to improve the image acquisition technique that will provide the best compromise between image quality and the average glandular dose (AGD).MethodsA contrast-detail analysis, employing the test object CDMAM, was carried out for the digital mammography unit manufactured by Lorad Hologic – model Selenia. We simulated two breast thicknesses using phantoms and a Figure of Merit as optimization tool, which includes an indicator of image quality, the IQFinv and the average glandular dose. Images of the ACR and TORMAM phantoms were obtained with both, automatic and optimized exposure parameters. In order to compare the image quality, the SNR (Signal to Noise Ratio) was measured in each image.ResultsIn the two phantoms, for both 4.5 and 7.5 cm thicknesses, the AGDs obtained with the optimized parameters show a reduction. In addition, the images obtained with the optimized exposure parameters, had the same or a better image quality when compared to the images obtained using the automatic mode.ConclusionsThe proposed optimization methodology proved to be an effective tool to improve the digital mammography unit, due to the use of objective metrics for evaluation and validation of the results.  相似文献   

7.
    
This study compared the detectability of simulated tumors using a high-energy X-ray inline phase sensitive digital breast tomosynthesis (DBT) prototype and a commercial attenuation-based DBT system. Each system imaged a 5-cm thick modular breast phantom with 50–50 adipose-glandular percentage density containing contrast-detail (CD) test objects to simulate different tumor sizes. A commercial DBT system acquired 15 projection views over 15 degrees (15d-15p) was used to acquire the attenuation-based projection views and to reconstruct the conventional DBT slices. Attenuation-based projection views were acquired at 32 kV, 46 mAs with a mean glandular dose (Dg) of 1.6 mGy. For acquiring phase sensitive projection views, the prototype utilized two acquisition geometries: 11 projection views were acquired over 15 degrees (15d-11p), and 17 projection views were acquired over 16 degrees (16d-17p) at 120 kV, 5.27 mAs with 1.51 mGy under the magnification (M) of 2. A phase retrieval algorithm based on the phase-attenuation duality (PAD) was applied to each projection view, and a modified Feldkamp-Davis-Kress (FDK) algorithm was used to reconstruct the phase sensitive DBT slices. Simulated tumor margins were rated as more conspicuous and better visualized for both phase sensitive acquisition geometries versus conventional DBT imaging. The CD curves confirmed the improvement in both contrast and spatial resolutions with the phase sensitive DBT imaging. The superiority of the phase sensitive DBT imaging was further endorsed by higher contrast to noise ratio (CNR) and figure-of-merit (FOM) values. The CNR improvements provided by the phase sensitive DBT prototype were sufficient to offset the noise reduction provided by the attenuation-based DBT imaging.  相似文献   

8.
    
PurposeDetector uniformity is an important parameter in digital mammography to guarantee a level of image quality adequate for early detection of breast cancer.Many problems with digital systems have been determined through the uniformity measurement, primarily as a result of incorrect flat-field calibration and artifacts caused by image receptor defects.The European guidelines suggest a method for the image uniformity assessment based on measurement of Signal-to-Noise ratio (SNR) and Pixel Value (PV) across a uniform image.Nineteen mammography systems from the same manufacturer installed in our organization incorporate an a-Se direct conversion detector. Since their installation, instability and inconsistency of image uniformity has attracted medical physicist attention.A number of different tests have been carried out in order to understand and establish reasons for this instability.MethodsThree different tests have been performed to evaluate the impact of the heel effect, detector temperature and ghosting on the uniformity images. All the tests are based on the acquisition of uniform images as suggested by the European Guidelines for Quality Assurance in Breast Cancer Screening and Diagnosis.ResultsResults show that an increase in detector temperature produces an increase of SNR and decrease of uniformity. A further decrease of uniformity ranging between 20% and 30% is due to the ghosting while a decrease of about 10% is due the heel effect.ConclusionsX-ray tube, system geometry and detector have an impact on the system uniformity and an understanding of the contribution of each is necessary in order to obtain comparable image quality among all the systems.  相似文献   

9.
    
PurposeThis study aimed to determine whether the SiPM-PET/CT, Discovery MI (DMI) performs better than the PMT-PET/CT system, Discovery 710 (D710).MethodsThe physical performance of both systems was evaluated using NEMA NU 2 standards. Contrast (%), uniformity and image noise (%) are criteria proposed by the Japanese Society of Nuclear Medicine (JSNM) for phantom tests and were determined in images acquired from Hoffman and uniform phantoms using the DMI and D710. Brain and whole-body [18F]FDG images were also acquired from a healthy male using the DMI and D710.ResultsThe spatial resolution at 1.0 cm off-center in the DMI and D710 was 3.91 and 4.52 mm, respectively. The sensitivity of the DMI and D710 was 12.62 and 7.50 cps/kBq, respectively. The observed peak noise-equivalent count rates were 185.6 kcps at 22.5 kBq/mL and 137.0 kcps at 29.0 kBq/mL, and the scatter fractions were 42.1% and 37.9% in the DMI and D710, respectively. The D710 had better contrast recovery and lower background variability. Contrast, uniformity and image noise in the DMI were 61.0%, 0.0225, and 7.85%, respectively. These outcomes were better than those derived from the D710 and satisfied the JSNM criteria. Brain images acquired by the DMI had better grey-to-white matter contrast and lower image noise at the edge of axial field of view.ConclusionsThe DMI offers better sensitivity, performance under conditions of high count rates and image quality than the conventional PMT-PET/CT system, D710.  相似文献   

10.
G0, G1, and mammalian cells and nuclei were shortly digested with either micrococcal nuclease or DNAse I, both before and after mild fixation, either before (G0) or after (G1) partial hepatectomy. Cells were Feulgen stained and examined by high resolution light microscopy. In metabolically active G1 nuclei, intranuclear DNA appears organized at least in two distinct domains, whereby, the highly dispersed one is large enough to be detected at the resolution of the light microscope and appears preferentially attacked by limited DNAse I digestion. The action of the enzyme is readily apparent only in the nuclei that are first digested and then fixed. Spectroscopic characterization of the same nuclei reveals that the fixation causes a sizeable removal of proteins, mostly in the soluble chromatin subfraction. Results are discussed in terms of two control levels for gene expression and for higher order DNA structure.  相似文献   

11.
目的对比研究平板探测器和影像板两种数字化影像信息检测系统图像质量与辐射剂量的关系。方法应用DR和CR系统分别对对比度-细节体模(CDRAD2.0)进行不同辐射剂量的曝光成像。记录每次曝光的模体表面辐射剂量,将所获取的影像用CDRAD 2.0评估软件分析计算图像质量因子反数值IQFinv,并应用Spearman相关性检验和Wilcoxon秩和检验进行分析,比较两种数字化影像信息检测系统图像质量与辐射剂量的差异。结果在管电流量不同mAs时,DR系统的IQFinv值与CR的IQFinv值差异有统计学意义(P〈0.05)。结论辐射剂量相同时,平板探测器对于低对比度细节的检测能力优于影像板;在获得相同的图像质量时,与CR相比应用DR大大降低了被检者辐射剂量。  相似文献   

12.
    
PurposeThis study aimed to determine a low-dose protocol for digital chest tomosynthesis (DTS).MethodsFive simulated nodules with a CT number of approximately 100 HU with size diameter of 3, 5, 8, 10, and 12 mm were inserted into an anthropomorphic chest phantom (N1 Lungman model), and then scanned by DTS system (Definium 8000) with varying tube voltage, copper filter thickness, and dose ratio. Three radiophotoluminescent (RPL) glass dosimeters, type GD-352 M with a dimension of 1.5 × 12 mm, were used to measure the entrance surface air kerma (ESAK) in each protocol. The effective dose (ED) was calculated using the recorded total dose-area-product (DAP). The signal-to-noise ratio (SNR) was determined for qualitative image quality evaluation. The image criteria and nodule detection capability were scored by two experienced radiologists. The selected low-dose protocol was further applied in a clinical study with 30 pulmonary nodule follow-up patients.ResultsThe average ESAK obtained from the standard default protocol was 1.68 ± 0.15 mGy, while an ESAK of 0.47 ± 0.02 mGy was found for a low-dose protocol. The EDs for the default and low-dose protocols were 313.98 ± 0.72 µSv and 100.55 ± 0.28 µSv, respectively. There were small non-significant differences in the image criteria and nodule detection scoring between the low-dose and default protocols interpreted by two radiologists. The effective dose of 98.87 ± 0.08 µSv was obtained in clinical study after applying the low-dose protocol.ConclusionsThe low-dose protocol obtained in this study can substantially reduce radiation dose while preserving an acceptable image quality compared to the standard protocol.  相似文献   

13.
    
PurposeThe goal of this study was to investigate the performance of a pre-clinical SPECT/PET/CT system for 188Re imaging.MethodsPhantom experiments were performed aiming to assess the characteristics of two multi-pinhole collimators: ultra-high resolution collimator (UHRC) and high-energy ultra high resolution collimator (HE-URHC) for imaging 188Re. The spatial resolution, image contrast and contrast-to-noise ratio (CNR) were investigated using micro-Jaszczak phantoms. Additionally, the quantification accuracy of 188Re images was evaluated using two custom-designed phantoms. The 188Re images were compared to those obtained with 99mTc (gold standard); the acquired energy spectra were analyzed and Monte-Carlo simulations of the UHRC were performed. To verify our findings, a C57BL/6-mouse was injected with 188Re-microspheres and scanned with both collimators.ResultsThe spatial resolution achieved in 188Re images was comparable to that of 99mTc. Acquisitions using HE-UHRC yielded 188Re images with higher contrast and CNR than UHRC. Studies of quantitative accuracy of 188Re images resulted in <10% errors for both collimators when the activity was calculated within a small VOI around the object of interest. Similar quantification accuracy was achieved for 99mTc. However, 188Re images showed much higher levels of noise in the background. Monte-Carlo simulations showed that 188Re imaging with UHRC is severely affected by down-scattered photons from high-energy emissions. The mouse images showed similar biodistribution of 188Re-microspheres for both collimators.ConclusionsVECTor/CT provided 188Re images quantitatively accurate and with quality comparable to 99mTc. However, due to large penetration of UHRC by high-energy photons, the use of the HE-UHRC for imaging 188Re in VECTor/CT is recommended.  相似文献   

14.
介绍了一种数字乳房X片图像的预处理算法。利用时域处理和形态学处理相结合的方法,对数字乳房X片图像进行预处理,去除无用背景像素点,有效减少后期增强、分割处理的数据量。  相似文献   

15.
Summary Attempts to study endothelial-epithelial interactions in the human breast have been hampered by lack of protocols for long-term cultivation of breast endothelial cells (BRENCs). The aim of this study was to establish long-term cultures of BRENCs and to compare their phenotypic traits with the tissue of origin. Microvasculature was localized in situ by immunohistochemitry in breast samples. From this tissue, collagen-rich stroma and adipose tissue were dissected mechanically and further disaggregated to release microvessel organoids BRENCs were cultured from these organoids in endothelial specific medium and characterized by staining for endothelial markers. Microvessels were a prominent feature of intralobular tissue as evidenced by immunostaining against endothelial specific markers such as CD31, VE-cadherin, and von Willebrand factor (VWF). Double staining against VE-cadherin and lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1) showed that blood and lymphatic vessels could be distinguished. An antibody against CD31 was used to refine protocols for isolation of microvasculature from reduction mammoplasties. BRENCs retained critical traits even at high passage, including uptake of low-density lipoprotein, and had E-selectin induced upon treatment with tumor necrosis factor-α. The first signs of senescence in passage 14 were accompained by gain of trisomy 11. At passage 18 cells showed chromosomal aberrations and growth arrest as revealed by β-galactosidase staining. We demonstrate here that breast microvasculature may serve as a large-scale source for expansion of BRENCs with molecular and functional traits preserved. These cells will form the basis for studies on the role of endothelial cells in breast morphogenesis.  相似文献   

16.
    
In suspended culture, most relevant for biotechnological application, plant cells form aggregates. This phenomenon is of importance as it is related to productivity, leads to local heterogeneities, and might be a reason for the considerable shear sensitivity of these cultures. The valid measurement of plant cell aggregates, however, is not trivial, due to a rather large size distribution and measurement artifacts implied by the measuring method. In this study, laser diffraction was used as a novel method for characterization of Taxus chinensis cells, a major source for the antitumor agent paclitaxel. Aggregate size measured in shaking flask cultivations over 10 days revealed an increase during the growth phase of a batch cycle and a decrease during the stationary phase. During growth, the increase in bio dry weight was proportional to aggregate size. Laser diffraction was found superior to microscopy and image analysis, which had a tendency to underestimate aggregate size up to 20%. This novel approach provides a practicable, rapid, robust, and reproducible way to analyze a 100‐fold more samples in considerably less time than image analysis and is therefore of especial value for quality control in industrial plant cell cultivation.  相似文献   

17.
    
The validity of material flow analyses (MFAs) depends on the available information base, that is, the quality and quantity of available data. MFA data are cross‐disciplinary, can have varying formats and qualities, and originate from heterogeneous sources, such as official statistics, scientific models, or expert estimations. Statistical methods for data evaluation are most often inadequate, because MFA data are typically isolated values rather than extensive data sets. In consideration of the properties of MFA data, a data characterization framework for MFA is presented. It consists of an MFA data terminology, a data characterization matrix, and a procedure for database analysis. The framework facilitates systematic data characterization by cell‐level tagging of data with data attributes. Data attributes represent data characteristics and metainformation regarding statistical properties, meaning, origination, and application of the data. The data characterization framework is illustrated in a case study of a national phosphorus budget. This work furthers understanding of the information basis of material flow systems, promotes the transparent documentation and precise communication of MFA input data, and can be the foundation for better data interpretation and comprehensive data quality evaluation.  相似文献   

18.
摘要 目的:探讨基于图像重建的电子计算机断层扫描仪器(Computed Tomography,CT)三维成像提升腹部增强扫描图像质量的价值。方法:2019年11月到2020年10月选择在本院进行腹部CT增强扫描的患者76例作为研究对象,采用电脑随机数字法将研究对象分为对照组和重建组各38例,对照组给予常规扫描成像,重建组给予基于自适应统计迭代重建(adaptive statistical iterative reconstruction,ASIR)的CT三维成像,记录两组成像质量与噪声情况。结果:两名医师对重建组的图像主观质量评分都高于对照组(P<0.05)。重建组的图像相对细腻柔和,能清晰显示图像细小血管断面,末梢血管显示良好,血管壁光滑柔和。重建组的动脉期、门静脉期、平衡期的肝脏CT值高于对照组(P<0.05),动脉期、门静脉期、平衡期的肝脏、胰腺对比噪声比(contrast to noise ratio,CNR)值低于对照组(P<0.05)。重建组的容积剂量指数(volume CT dose index,CTDIvol)和剂量长度乘积(Dose-Length product,DLP)、有效剂量(effective dose,ED)值都低于对照组(P<0.05)。结论:基于图像重建的CT三维成像能提升腹部增强扫描主客观图像质量,降低图像噪声,更利于腹部疾病的显示,从而提高正确诊断率。  相似文献   

19.
This study was designed to develop a new method based on fluorescence microscopy and image analysis for the automatic assessment of sperm morphometry and to study separately the effect of drying and fixation on the parameters of head sperm morphometry in the ram. The study was divided into two experiments. In the first experiment, ejaculates from 25 adult males were collected using an artificial vagina, diluted and divided into four sample aliquots. The first was labeled directly with Hoechst 33342 (FRESH), and the others were processed as smears. Between smears, one group was directly labeled with Hoechst after air drying (DRIED), and the other were fixed either with glutaraldehyde (GLUT), or with methanol (MET), and labeled with Hoechst afterward. Digital images of the fluorescence-labeled sperm were recorded with a digital camera, and sperm heads were automatically captured and analyzed using the ImageJ program. The method used allowed a fast and automatic selection of most sperm heads for a given image with high precision. There was a general trend toward significant decrease in head length, width, area and perimeter of air-dried sperm compared with fresh sperm. On average, this decrease was of 4.1% in length, 4.3% in width, 9.1% in area, and 2.8% in perimeter. Between semen smears, fixation with glutaraldehyde significantly increased head sperm dimensions. The smears fixed with glutaraldehyde method is recommended for a more practical use than with fresh samples, providing better quality images than the other methods, and because the morphometric results obtained were more similar to the FRESH group than those of the DRIED and MET. In the second experiment, ejaculates from adult males were used to compare the sperm head morphometric results obtained with the new method developed (using the GLUT treatment as reference) with a more conventional CASMA method (semen smears stained with Hemacolor and processed with the ISAS commercial software, HEM). The GLUT method allowed the analysis of 100% of sperm, whereas only 93% of sperm could be analyzed using HEM. Spermatozoa displayed a bigger size when processed with HEM than with GLUT method in all primary sperm head morphometric parameters. A significant correlation was observed between the two methods used in this experiment for all morphometric size parameters. The new method developed allows automatic determination of sperm head morphometry in a reduced time, which facilitates its use in routine semen analysis. It was concluded that the automation of sperm morphometry is feasible using fluorescence microscopy and image analysis and that the effect of drying and fixation was less important than previously stated.  相似文献   

20.
    
ObjectiveThis study aims to assess low-contrast image quality using a low-contrast object specific contrast-to-noise ratio (CNRLO) analysis for iterative reconstruction (IR) computed tomography (CT) images.MethodsA phantom composed of low-contrast rods placed in a uniform material was used in this study. Images were reconstructed using filtered back projection (FBP) and IR (Adaptive Iterative Dose Reduction 3D). Scans were performed at six dose levels: 1.0, 1.8, 3.1, 4.6, 7.1 and 13.3 mGy. Objective image quality was assessed by comparing CNRLO with CNR using a human observer test.ResultsCompared with FBP, IR yielded increased CNR at the same dose levels. The results of CNRLO and observer tests showed similarities or only marginal differences between FBP and IR at the same dose levels. The coefficient of determination for CNRLO was significantly better (R2 = 0.86) than that of CNR (R2 = 0.47).ConclusionFor IR, CNRLO could potentially serve as an objective index reflective of a human observer assessment. The results of CNRLO test indicated that the IR algorithm was not superior to FBP in terms of low-contrast detectability at the same radiation doses.  相似文献   

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