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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
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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
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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
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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
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The aim of this work was to evaluate how different acquisition geometries and reconstruction parameters affect the performance of four digital breast tomosynthesis (DBT) systems (Senographe Essential – GE, Mammomat Inspiration – Siemens, Selenia Dimensions – Hologic and Amulet Innovality – Fujifilm) on the basis of a physical characterization.Average Glandular Dose (AGD) and image quality parameters such as in-plane/in-depth resolution, signal difference to noise ratio (SDNR) and artefact spread function (ASF) were examined.Measured AGD values resulted below EUREF limits for 2D imaging. A large variability was recorded among the investigated systems: the mean dose ratio DBT/2D ranged between 1.1 and 1.9.In-plane resolution was in the range: 2.2 mm−1–3.8 mm−1 in chest wall-nipple direction. A worse resolution was found for all devices in tube travel direction.In-depth resolution improved with increasing scan angle but was also affected by the choice of reconstruction and post-processing algorithms. The highest z-resolution was provided by Siemens (50°, FWHM = 2.3 mm) followed by GE (25°, FWHM = 2.8 mm), while the Fujifilm HR showed the lowest one, despite its wide scan angle (40°, FWHM = 4.1 mm).The ASF was dependent on scan angle: smaller range systems showed wider ASF curves; however a clear relationship was not found between scan angle and ASF, due to the different post processing and reconstruction algorithms.SDNR analysis, performed on Fujifilm system, demonstrated that pixel binning improves detectability for a fixed dose/projection.In conclusion, we provide a performance comparison among four DBT systems under a clinical acquisition mode. 相似文献
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This article aims to present the protocol on Quality Controls in Digital Mammography published online in 2015 by the European Federation of Organisations for Medical Physics (EFOMP) which was developed by a Task Force under the Mammo Working Group. The main objective of this protocol was to define a minimum set of easily implemented quality control tests on digital mammography systems that can be used to assure the performance of a system within a set and acceptable range. Detailed step-by-step instructions have been provided, limiting as much as possible any misinterpretations or variations by the person performing. It is intended that these tests be implemented as part of the daily routine of medical physicists and system users throughout Europe in a harmonised way so allowing results to be compared. In this paper the main characteristics of the protocol are illustrated, including examples, together with a brief summary of the contents of each chapter. Finally, instructions for the download of the full protocol and of the related software tools are provided. 相似文献
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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
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目的评价DR摄影系统在新生儿检查中的应用价值。方法利用CR系统和DR系统（使用剂量为前者的1／4）分别得到新生儿30幅图像。由6位医生来评价以上两者的影像系统对于导尿管末端的显影的清晰程度。结果二者的图像在诊断质量上没有统计学差异。结论DR有较好的分辨率和低噪声特性,高DQE有助于减少新生儿患者的接受剂量,图像传输速度快,使得临床诊断更为及时。 相似文献
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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
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Foster JM Degroeve S Gatto L Visser M Wang R Griss J Apweiler R Martens L 《Proteomics》2011,11(11):2182-2194
Proteomics is a rapidly expanding field encompassing a multitude of complex techniques and data types. To date much effort has been devoted to achieving the highest possible coverage of proteomes with the aim to inform future developments in basic biology as well as in clinical settings. As a result, growing amounts of data have been deposited in publicly available proteomics databases. These data are in turn increasingly reused for orthogonal downstream purposes such as data mining and machine learning. These downstream uses however, need ways to a posteriori validate whether a particular data set is suitable for the envisioned purpose. Furthermore, the (semi-)automatic curation of repository data is dependent on analyses that can highlight misannotation and edge conditions for data sets. Such curation is an important prerequisite for efficient proteomics data reuse in the life sciences in general. We therefore present here a selection of quality control metrics and approaches for the a posteriori detection of potential issues encountered in typical proteomics data sets. We illustrate our metrics by relying on publicly available data from the Proteomics Identifications Database (PRIDE), and simultaneously show the usefulness of the large body of PRIDE data as a means to derive empirical background distributions for relevant metrics. 相似文献
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PurposeQuality assurance (QA) phantoms for testing different image quality parameters in computed tomography (CT) are commercially available. Such phantoms are also used as reference for acceptance in the specifications of CT-scanners. The aim of this study was to analyze the characteristics of the most commonly used QA phantom in CT: Catphan 500/504/600.MethodsNine different phantoms were scanned on the same day, on one CT-scanner with the same parameter settings. Interphantom variations in CT-number values, image uniformity and low contrast resolution were evaluated for the phantoms. Comparisons between manual image analysis and results obtained from the automatic evaluation software QAlite were performed.ResultsSome interphantom variations were observed in the low contrast resolution and the CT-number modules of the phantoms. Depending on the chosen regulatory framework, the variations in CT-numbers can be interpreted as substantial. The homogenous modules were found more invariable. However, the automatic image analysis software QAlite measures image uniformity differently than recommended in international standards, and will not necessarily give results in agreement with these standards.ConclusionsIt is important to consider the interphantom variations in relation to ones framework, and to be aware of which phantom is used to study CT-numbers and low contrast resolution for a specific scanner. Comparisons with predicted values from manual and acceptance values should be performed with care and consideration. If automatic software-based evaluations are to be used, users should be aware that large differences can exist for the image uniformity testing. 相似文献
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PurposeA simple “paperclip test” for the function of individual elements in a diagnostic ultrasound transducer array is widely performed and has been adapted for phased arrays. The aim of this study was to adapt the test further for multi-row transducer arrays.MethodsAn embossing tool was used in place of the usual paperclip or metal rod and was slowly moved along the transducer array, attempting to isolate the signal from each row in turn. Phased array transducers were operated in M-mode. Non-functioning elements were identified by a reduction in amplitude of the reverberation line. The test was repeated several times for each transducer, ensuring that all non-functioning elements were identified and looking for consistency of results. 28 phased arrays and 5 linear/curvi-linear arrays in clinical use and 1 phased array and 1 linear array already identified as faulty by electronic transducer testing, and not in clinical service, were available for testing.Results8 of the clinical phased arrays were found to have 1 or more faulty elements; 3 had only minor defects and 5 were replaced under warranty or service contract. The linear/curvi-linear arrays showed no fault. The adapted test showed the failed elements in the known faulty phased array, except at the end of the array, but weak elements were not detected. The faulty linear array had a block of failed outer elements which was identified by the test.ConclusionsThe adapted test is capable of detecting non-functioning elements in multi-row arrays, but weak elements were not detected. 相似文献
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PurposeA number of guidelines for ultrasound quality assurance recommend the use of the in air reverberation depth as a proxy measure for sensitivity. The test is quantised, i.e. it depends on the brightness of the deepest in air reverberation. The aim of this study was to investigate a possible enhancement to the test, where the gain is reduced to determine the “reverberation threshold”.MethodsThe test was introduced in several ultrasound departments. Results were audited to determine agreement with annual tests of sensitivity using a tissue mimicking test object.ResultsThe new test was performed on 100 probes. A change in reverberation threshold was demonstrated in 9 probes; 8 of these also had changes in penetration and/or grey level in a tissue mimicking test object. Reduced penetration but no change in reverberation threshold was seen in 2 probes.ConclusionsThe reverberation threshold provides a simple enhancement to the in air sensitivity test. Periodic sensitivity testing with a tissue mimicking test object remains important. 相似文献
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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
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In this study the generalized Modulation Transfer Function (GMTF) and the geometric sharpness (Sgeo) were used (i) to study the effects of various focal spot sizes (0.04 mm–0.3 mm), x-ray intensity distributions (Gaussian and double Gaussian), breast thicknesses (2–7 cm) and magnifications M (1.0–2.0) on the spatial resolution of an a-Se digital mammography system, (ii) to identify suitable focal spots for magnification mammography and (iii) derive optimum magnifications. For the calculation of GMTF the required components were: focal spot MTF, obtained from theory, detector MTF, scatter MTF and scatter fraction obtained from Monte Carlo simulations. The results showed that focal spots with sizes up to 0.18 mm are suitable for magnification mammography offering a GMTF which is >50% and >20% at the respective object frequencies of 6.5 mm−1 and 9 mm−1. Focal spots with sizes < 0.16 mm and Gaussian. intensity distribution, or sizes ≤ 0.1 mm and double Gaussian, offer a system resolution which improves or does not deteriorate with magnification for most object frequencies. For larger focal spots, i.e. 0.16–0.18 mm for a Gaussian and 0.12–0.18 mm for a double Gaussian. intensity distribution, optimum magnifications exist which depend on the object frequency and breast thickness. System resolution (in terms of Sgeo) is maximized at M = 1.8–2.0 (all breast thicknesses) for Gaussian intensity distribution, and at M = 1.4–1.6 (breast thicknesses ≤ 4 cm) and M = 1.6–1.8 (thicker breasts) for double Gaussian. 相似文献
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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
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Computer-assisted sperm analysis (CASA) systems have evolved over approximately 40 years, through advances in devices to capture the image from a microscope, huge increases in computational power concurrent with amazing reduction in size of computers, new computer languages, and updated/expanded software algorithms. Remarkably, basic concepts for identifying sperm and their motion patterns are little changed. Older and slower systems remain in use. Most major spermatology laboratories and semen processing facilities have a CASA system, but the extent of reliance thereon ranges widely. This review describes capabilities and limitations of present CASA technology used with boar, bull, and stallion sperm, followed by possible future developments. Each marketed system is different. Modern CASA systems can automatically view multiple fields in a shallow specimen chamber to capture strobe-like images of 500 to >2000 sperm, at 50 or 60 frames per second, in clear or complex extenders, and in <2 minutes, store information for ≥30 frames and provide summary data for each spermatozoon and the population. A few systems evaluate sperm morphology concurrent with motion. CASA cannot accurately predict ‘fertility’ that will be obtained with a semen sample or subject. However, when carefully validated, current CASA systems provide information important for quality assurance of semen planned for marketing, and for the understanding of the diversity of sperm responses to changes in the microenvironment in research. The four take-home messages from this review are: (1) animal species, extender or medium, specimen chamber, intensity of illumination, imaging hardware and software, instrument settings, technician, etc., all affect accuracy and precision of output values; (2) semen production facilities probably do not need a substantially different CASA system whereas biology laboratories would benefit from systems capable of imaging and tracking sperm in deep chambers for a flexible period of time; (3) software should enable grouping of individual sperm based on one or more attributes so outputs reflect subpopulations or clusters of similar sperm with unique properties; means or medians for the total population are insufficient; and (4) a field-use, portable CASA system for measuring one motion and two or three morphology attributes of individual sperm is needed for field theriogenologists or andrologists working with human sperm outside urban centers; appropriate hardware to capture images and process data apparently are available. 相似文献