Dryview 8900与Dryview 8700干式激光相机的胶片特性和图像质量比较

目的比较Dryview8900和Dryview8700干式激光相机的胶片特性和图像质量。方法选择10例乳腺数字影像经同一网络分别打印在两种激光相机上,3位放射医师从4个方面诸如对比度,细节显示,诊断性能以及总体印象对图像质量进行主观比较。两种相机以标准设置打印校正梯形灰阶测试片,绘制感光曲线,客观比较胶片特性。结果Dryview8900较Dryview8700打印的胶片对比度、细节显示和总体印象更好,但两者的诊断效果相同。结论两种激光相机均能满足诊断要求,由于Dryview8900在细节显示上有优势,因此在数字乳腺摄影中应用效果更佳。     

Quality analysis of DSA equipment

Summary In the framework of a quality analysis project for the improvement of digital subtraction angiography (DSA) equipment, an inventory was made of the image quality and radiation dose of DSA equipments in six hospitals in the Netherlands. The image quality was investigated with a contrast detail (CD) phantom. The entrance dose of the radiation on this phantom and the skin dose at the level of the eye lenses and the thyroid gland were measured in these hospitals using a human phantom during a standardised simulated DSA examination of the aortic arch and brachiocephalic arteries, by means of thermo-luminescence dosimeters (TLD). To establish the relation of these measurements on the human phantom and real patient examinations, the same measurements were carried out in our own hospital on 16 patients during a comparable DSA examination. To find the difference from the dose in conventional angiography (CA) the same measurements were carried out in our hospital on 11 patients during a comparable examination. These dose measurements were also carried out on the human phantom with the use of the same CA equipment. We vound large differences in image quality in the various hospitals. Within one hospital, monitor images were better than hard copy images. These differences were strongly related to the amount of radiation used, to the technique of storing the images (digital or analogue) and to the quality of the equipment used to make hard copies (the imager). Recommendations are made for improvement and quality control.     

Image quality and breast dose of 24 screen-film combinations for mammography

In this study the effect of different mammographic screen-film combinations on image quality and breast dose, and the correlation between the various image quality parameters, breast dose and the sensitometric parameters of a film were investigated. Three Agfa (MR5-II, HDR, HT), two Kodak (Min-R M, Min-R 2000), one Fuji (AD-M), one Konica (CM-H) and one Ferrania (HM plus) single emulsion mammographic films were combined with three intensifying screens (Agfa HDS, Kodak Min-R 2190 and Fuji AD-MA). The film characteristics were determined by sensitometry, while the image quality and the dose to the breast of the resulting 24 screen-film combinations were assessed using a mammography quality control phantom. For each combination, three images of the phantom were acquired with optical density within three different ranges. Two observers assessed the quality of the 72 phantom images obtained, while the breast dose was calculated from the exposure data required for each image. Large differences among screen-film combinations in terms of image quality and breast dose were identified however, that, could not be correlated with the film's sensitometric characteristics. All films presented the best resolution when combined with the HDS screen at the expense of speed, and the largest speed when combined with the AD-MA screen, without degradation of the overall image quality. However, an ideal screen-film combination presenting the best image quality with the least dose was not identified. It is also worth mentioning that the best performance for a film was not necessarily obtained when this was combined with the screen provided by the same manufacturer. The results of this study clearly demonstrate that comparison of films based on their sensitometric characteristics are of limited value for clinical practice, as their performance is strongly affected by the screens with which they are combined.     

Four multidetector-row helical CT: image quality and volume coverage speed

PURPOSE: To evaluate the imaging performance characteristics of four multidetector-row helical computed tomography (CT) and assess improvement in volume coverage speed over that with single multidetector-row helical CT. MATERIALS AND METHODS: The section-sensitivity profile and image noise of a four multidetector-row scanner were measured with phantom scans and compared with predictions from theoretic models. Nominal section thickness ranged from 1.25 to 10.00 mm, beam collimation from 1.25 to 5.00 mm, and table speed from 3.75 to 30.00 mm per rotation. Image artifacts with four and single multidetector-row helical CT were compared in both a phantom study and a subjective rating analysis of clinical images. RESULTS: Compared with single multidetector-row helical CT, the volume coverage speed of four multidetector-row helical CT (range, 3.75-30.00 mm per rotation) is at least twice as fast as that with single multidetector-row helical CT (1.0-10.0 mm per rotation) with fully comparable image quality or, in many cases, three times as fast with diagnostically comparable image quality. CONCLUSION: Compared with single multidetector-row helical CT, four multidetector-row helical CT provides a two- to threefold improvement in volume coverage speed with comparable diagnostic image quality.     

Description and implementation of a quality control program in an imaging-based clinical trial

RATIONALE AND OBJECTIVES: The American College of Radiology Imaging Network is participating in the National Lung Screening Trial, a large, multicenter, randomized controlled trial, comparing multidetector helical computed tomography (MDCT) versus chest radiography (CXR) in screening for lung cancer. Because the threshold for detection of disease is an inherent function of image quality, and consistent image quality is necessary to track changes in suspicious findings, our purpose was to develop an image quality control (QC) program across all clinical sites for both modalities. MATERIALS AND METHODS: The primary goals of the QC program include standardization of imaging protocols, certification of imaging equipment, and ongoing, periodic evaluation of the equipment calibration and image quality. Minimum standards for equipment and standardized cross-platform acquisition protocols are achieved via radiologist and physicist attestation forms and web-distributed technique charts, respectively. Imaging equipment performance standards are implemented through an initial machine certification process that includes equipment calibration. Ongoing assessment of equipment performance and calibration, as well as adherence to established imaging protocols. is accomplished via periodic submission of calibration records and phantom images. Participant-specific image acquisition parameters are entered into a web-based centralized database and variations from established protocols are automatically flagged for review. Participant radiation dose can be estimated from the image acquisition parameters applied to the imaging equipment calibration measurements. A radiologist visual review committee also evaluates participant images for diagnostic quality. Data are collected from 23 independent centers, representing 14 models of MDCT scanners from four manufacturers, and CXR systems that include film-screen, computed radiography, and direct digital radiography systems. RESULTS: Widespread imaging protocol variation in extant clinical practice-as well as variability in equipment technology, image acquisition parameters, manufacturer terminology, and user interface-have required careful standardization as a prerequisite to trial participation and ongoing image QC. Acceptable ranges for image acquisition parameters have been refined to accommodate continuously evolving equipment platforms and the scope of participant size and body habitus. CONCLUSION: Standardization of imaging protocols is a critical component of image-based clinical trials, predicated on ongoing dialogue between sites and a centralized review committee.     

Optimization of the chest exposure condition with a contrast-detail phantom: evaluation of the flat-panel versus computed radiography systems

In this study, we evaluated the performance of a digital chest imaging system using a contrast-detail (C-D) phantom. In the initial step, 76 sample images of the C-D phantom were produced by changing the doses from 0.5, 0.75, 1.0, 1.25, 1.5, to 2.0 times the dose for a screen-film (S/F) system. The sample images were analyzed by five radiological technologists and two medical physicists, and the image quality figure (IQF) was determined. The quality of each image was examined, and appropriate doses were determined from the calculated IQF to obtain the same image quality for other digital chest imaging systems. The method of determining IQF from C-D phantom analysis was very useful for comparing image quality and determining radiographic techniques.     

External quality control of gamma cameras--results of an inter-laboratory comparison study in Austria

Some 28 nuclear medicine departments out of a total of 40 participated in a nationwide Austrian interlaboratory comparison of the imaging quality of gamma cameras. The participation was voluntary, and confidentiality of the individual results was guaranteed. The survey was completed within 2 months, employing instructors to administrate the tests. An emission phantom simulating a flood field with non-uniformities was imaged by 43 cameras, and 54 images were evaluated. The test images were read by the participants using a graded rating scale to indicate the probability of the presence of a non-uniformity in the various parts of the image. The rating data were used to construct individual ROC curves for each image. The area under the ROC curve was used as the ranking parameter for image quality. The results show a spread of the ROC areas between 0.6 and 0.99, with a median of 0.81. A correlation was found between the year of installation and the ROC area obtained from the gamma camera, indicating improvements of performance in more recent cameras, which accounts for part of the variation of the ROC areas. The remaining variations are due to differences in the performance of the gamma cameras. Feedback was provided to the participants by describing individual performance with respect to the true structure of the phantom and by comparing this performance with that of the group. A questionnaire accompanying the test phantom yielded information about the practice of routine quality control and about details of the acquisition and analysis of images.(ABSTRACT TRUNCATED AT 250 WORDS)     

Balancing image quality and dose in diagnostic radiology

The formation of images in diagnostic radiology involves a complex interplay of many factors and the ideal balance is to obtain an image, which is adequate for the clinical purpose with the minimum radiation dose. Some factors are classified as physical parameters and can be measured objectively in physical test phantoms, but the diagnostic images must still be interpreted by human observers which does not always mean an ideal observer. This subjective nature of image interpretation makes the objective approach to a full assessment difficult. The ideal method for evaluation of imaging techniques is through clinical trials. Scoring of image quality criteria relating to features observed in a normal clinical radiograph gives a simple method through which image quality can be assessed and related to the radiation dose used. But if optimal performance is to be achieved, it is necessary to understand both the influence of the physical factors in the image formation on dose and image quality and to apply the correct methodology in these analyses of optimisation of the imaging process.     

External quality control of gamma cameras —results of an inter-laboratory comparison study in Austria

Some 28 nuclear medicine departments out of a total of 40 participated in a nationwide Austrian interlaboratory comparison of the imaging quality of gamma cameras. The participation was voluntary, and confidentiality of the individual results was guaranteed. The survey was completed within 2 months, employing instructors to administrate the tests. An emission phantom simulating a flood field with non-uniformities was imaged by 43 cameras, and 54 images were evaluated. The test images were read by the participants using a graded rating scale to indicate the probability of the presence of a non-uniformity in the various parts of the image. The rating data were used to construct individual ROC curves for each image. The area under the ROC curve was used as the ranking parameter for image quality. The results show a spread of the ROC areas between 0.6 and 0.99, with a median of 0.81. A correlation was found between the year of installation and the ROC area obtained from the gamma camera, indicating improvements of performance in more recent cameras, which accounts for part of the variation of the ROC areas. The remaining variations are due to differences in the performance of the gamma cameras. Feedback was provided to the participants by describing individual performance with respect to the true structure of the phantom and by comparing this performance with that of the group. A questionnaire accompanying the test phantom yielded information about the practice of routine quality control and about details of the acquisition and analysis of images. The survey demonstrated the feasibility and usefulness of interlaboratory comparisons of this type even for a small number of participants. The feedback was found by the participants to be helpful and stimulated awareness of the importance of quality control.     

CT机应用质量检测与临床照片图像质量关系

目的：分析CT设备应用质量检测结果与临床照片图像质量之间的关系，探讨检测方法的改进措施。方法：采用Catphan500体模和标准剂量组合头模，依照军队CT机应用质量检测与评审规范，对118台CT设备实施检测；同时随机抽取近期从本各部位临床照片共七张，由专家组评审分级。以图像质量等级为关键字，对各参数进行归类统计。结果：临床照片图像质量与剂量指数、噪声水平、密度分辨经和空间分辨率关系密切。结论：实际检测中，要根据参数之间的相互关系合理安排先后顺序：先测量层厚，并校准直至合格；然后进行照射剂量水平的控制；再继续其它参数的检测。     

柯达Direct View DR500成像系统与柯尼卡REGINS 350 CR成像系统技术与性能对比分析

目的:研究相同工作模式下的CR与DR的技术与性能的差异。方法:柯尼卡REGINGS35 0CR(直接数字转换器35 0型)、柯达DirectViewDR5 0 0 0 ;西门子 MultixX光机;体模:QCPhantomforDigitalandConventionalChestRadiography ;EBM 上海岱嘉公司PACS系统 医学图像诊断工作站软件:(UniSight) ;BARLO 1K显示器。采集不同参数的体模图像2 0幅,采集不同参数及胖、中、瘦体型男女志愿者11人。结果:柯尼卡REGINS 35 0具有更广泛的实用性。总体性能评价;柯尼卡ERGINGS 35 0型除胸部摄影的影像质量比柯达DirectViewDR5 0 0 0稍有不足,但在其它部位摄取的影像质量要高于柯达DirecViewDR5 0 0 0 ,原因在于柯达DirectViewDR5 0 0 0的摄影距离固定为183cm ,其本身的成像性能与后处理功能无法弥补。结论:柯尼卡REGINGS 35 0型成像系统整体性能优于柯达DirectViewDR5 0 0 0成像系统。     

Quality assurance for MRI: practical experience

The aim of this study is to propose guidelines for quality assurance (QA) in MRI, based on a comprehensive assessment of QA parameters undertaken on a busy clinical MRI scanner over the course of 1 year. QA phantoms supplied by the scanner manufacturer were used together with the Eurospin MRI phantom set. Signal-to-noise ratio (SNR) and image uniformity were measured daily from spin echo images acquired using a quadrature send-receive head coil and from a gradient echo sequence using the Helmholtz body coil. The voltage of the transmit radiofrequency (RF) amplifier was noted. Monthly measurements of slice thickness, geometric distortion, slice position, image resolution and image ghosting were acquired using the head coil. In addition, SNR was measured monthly on a selection of commonly used coils. Apart from some drift of the RF amplifier voltage, all measurements were within acceptable limits and were stable over the course of 1 year. Satisfactory measurements of SNR were possible using the simple phantom supplied with the scanner. The SNR, geometric distortion and RF amplifier voltage are simple to determine and can be measured in less than 15 min by the scanner operator, using the scanner software. Weekly recording of these parameters is recommended for busy clinical MRI scanners, as this should allow deviations from acceptable limits to be identified early. Such in-house checks can usefully be compared with the less frequent estimations performed by the service engineer. Comprehensive QA routines are discussed for systems used for quantitative measurements.     

Reducing dose in urography while maintaining image quality—a comparison of storage phosphor plates and a flat-panel detector

The introduction of new flat-panel detector technology often forces us to accept too high dose levels as proposed by the manufacturers. We need a tool to compare the image quality of a new system with the accepted standard. The aim of this study was to obtain a comparable image quality for two systems—storage phosphor plates and a flat-panel system using intravenous urography (IVU) as a clinical model. The image quality figure was calculated using a contrast–detail phantom (CDRAD) for the two evaluated systems. This allowed us to set a dose for the flat-panel system that gave equivalent image quality to the storage phosphor plates. This reduced detector dose was used in an evaluation of clinical images to find out if the dose reduction from the phantom study indeed resulted in images of equal clinical image quality. The image quality was assessed using image criteria of the European guidelines for IVU with visual grading analysis. Equivalent image quality in image pairs was achieved at 30% of the dose. The CDRAD contrast–detail phantom makes it possible to find dose levels that give equal image quality using different imaging systems.     

Sensitivity, resolution and image quality with a multi-head SPECT camera.

This investigation sought to determine which collimation factors were most important in providing superior image quality with a three-headed SPECT device. The relationship between sensitivity, resolution and SPECT image quality was studied. Two different sets of parallel-hole collimators were used. The ultrahigh-resolution collimators have higher spatial resolution (8.9 versus 11.0 mm), but only 55% of the sensitivity of the high-resolution collimators. A phantom with hot rods was imaged with both collimator sets. Observers compared images with the ultrahigh-resolution collimators to images of varying counts with the high-resolution collimators and determined which high-resolution images matched the ultrahigh-resolution images in image quality. Eleven patient studies were acquired with both collimator sets for equal time, and observers chose which image set they preferred. Transverse images of brain and liver studies were simulated with varying resolution and counts and subjectively compared. The phantom study indicated that the improvement in resolution led to image quality comparable to increasing the number of counts by a factor of 2.5 to 3.4. The clinical studies showed that the ultrahigh-resolution collimators were preferred in a large majority of the cases. These trends were also seen in the simulation study. These results confirm that higher resolution collimators should be used with multihead SPECT devices. The improvement in resolution more than compensates for the loss in sensitivity, leading to an overall improvement in image quality.     

Measurement of image quality in diagnostic radiology.

The aim in radiology is to obtain images which are adequate for the clinical purpose with the minimum radiation dose to the patient. If optimum performance is to be achieved, assessments of image quality must be made to balance against patient dose. The subjective nature of image interpretation makes an objective approach to such assessment difficult. Methods widely applied involve the use of test objects, which although providing a measure of imaging performance may be difficult to link to clinical image formation. The ideal method for evaluation of imaging techniques is through clinical trials and this should be used to address major questions. Scoring of quality criteria, relating to features observed in a normal clinical radiograph, provides a simple method through which image quality can be assessed in every hospital department.     

不同摄影源像距对小儿胸部数字X线技术辐射剂量图像质量的影响

目的不同摄影源像距对小儿胸部数字X线技术(DR)辐射剂量、图像质量的影响。方法选取我院2017至2018年收治的60例行胸部X线(DR)检查的患儿为研究对象开展回顾性分析,首先进行体模预实验曝光,采用同一管电压和不同摄影源像距(SID)(80~150 cm),其中10 cm为1组,记录每次曝光的毫安秒和入射体表剂量(ESD)。选取体模预实验中ESD相对低剂量和剂量适中的2组(90 cm和110 cm)开展临床试验。所有患儿住院期间采用同一X线机对同一患儿进行胸部DR的初查和复查,并分为初查组和复查组,初查组采用SID=110 cm,复查组采用SID=90 cm,由3位影像学专家采用5分法对图像质量进行打分。结果通过影像学专家评判,80~150 cm的DR曝光图像质量无差异,且不同的SID下实施胸部体模DR,得到的毫安秒与辐射剂量不相同,同一体模在相同曝光指数下,随着SID的增大,毫安秒与辐射剂量均逐渐增大;初查组的图像质量评分为(4.9±1.0)分,复查组的图像质量评分为(4.9±1.0),2组的图像质量评分比较差异无统计学意义(P>0.05)。结论患儿DR胸部摄影中不同SID,其体表辐射剂量具有明显差异,SID为90 cm时能够大幅度地降低X线管的输出剂量,减少体表辐射剂量,延长X线管的使用寿命。     

数字X射线摄影中散射线滤除模板成像质量与辐射剂量学评价

目的比较散射线滤除模板及常规滤线栅对数字X射线影像进行散射线校正所成影像质量与辐射剂量差异。方法 以对比度-细节体模(CDRAD 2.0)及ROC统计学体模(ALVIM TRS)为成像对象,分别使用散射线滤除模板技术和常规滤线栅技术,获取经散射线校正的体模数字X射线影像,比较两种散射线滤除方法所得的体模影像图像质量因子(IQF)和信号检出概率,分析两种方法图像质量及体模表面入射剂量差别。结果 在不同体模表面照射剂量条件下,应用散射线滤除模板技术和常规滤线栅技术,消除散射线后的数字影像其图像质量因子(IQF)和信号检出概率(P_det)差异均有统计学意义(P<0.05)。结论 数字X射线摄影时,应用散射线滤除模板技术(SFTT)可以有效滤除散射线。与滤线栅相比,相同照射条件下SFTT能够明显改善图像质量;在获得相同图像质量前提下,应用SFTT,体模表面入射剂量比使用滤线栅降低30%;SFTT为数字X射线摄影中有效滤除散射线、提高X射线图像质量、降低患者剂量的可选择方法。     

Dry versus conventional laser imagers: film properties and image quality

The authors compared image quality and stability with a dry laser imager versus a conventional wet laser imager. Hard copies of 56 magnetic resonance imaging and computed tomographic studies were analyzed for gray-scale distribution and temperature stability. Results with the dry laser imager did not reach the quality of results with a wet laser imager, but the performance and ecologic criteria were sufficient to make use of this technique advantageous.     

Image quality of a wet laser printer versus a paper printer for full-field digital mammograms

OBJECTIVE: The purpose of our study was to compare the image quality of a wet laser printer with that of a paper printer for full-field digital mammography (FFDM). MATERIALS AND METHODS: For both a wet laser printer and a paper printer connected to an FFDM system, image quality parameters were evaluated using a standardized printer test image (luminance density, dynamic range). The detectability of standardized objects on a phantom was also evaluated. Furthermore, 640 mammograms of 80 patients with different breast tissue composition patterns were imaged with both printers. Subjective image quality parameters (brightness, contrast, and detection of details of anatomic structures-that is, skin, subcutis, musculature, glandular tissue, and fat), the detectability of breast lesions (mass, calcifications), and the diagnostic performance according to the BI-RADS classification were evaluated. RESULTS: Both the luminance density and the dynamic range were superior for the wet laser printer. More standardized objects were visible on the phantom imaged with the wet laser printer than with the paper printer (13/16 vs 11/16). Each subjective image quality parameter of the mammograms from the wet laser printer was rated superior to those of the paper printer. Significantly more breast lesions were detected on the wet laser printer images than on the paper printer images (masses, 13 vs 10; calcifications, 65 vs 48; p < 0.05). With the paper printer images, BI-RADS 4 and 5 categories were underestimated for 10 (43.5%) of 23 patients. CONCLUSION: For FFDM, images obtained from a wet laser printer show superior objective and subjective image quality compared with a paper printer. As a consequence, the paper printer should not be used for FFDM.     

Average glandular tissue dose and image quality in screen-film mammography

We investigated the relationship between average glandular tissue dose and imaging properties such as image density, contrast, and visual image quality, varying the tube voltage and subject parameters (glandular fraction and breast thickness) The wax inserts of 156 phantom and disk of polymethyl methacrylate (PMMA) were arranged between the BR-12 breast-equivalent phantoms. These phantoms were radiographed using automatic exposure control (AEC) for the various combinations of tube voltage and subject parameters. In addition, exposures were measured at the same time. The results showed that the average glandular tissue dose increased when the high glandular fraction and/or thick phantom were being radiographed with the low tube voltage. We found that the criteria of the Japanese Mammography Screening Accreditation Program for image quality were not satisfied when breast thickness was greater than 6 cm.