两种根尖片数字化成像系统的临床应用评价

目的探讨根尖片数字化间接成像系统(CR)和直接成像系统(DR)临床应用的优缺点。方法对两种数字化成像系统的曝光剂量、成像时间和图像质量进行比较分析。结果直接成像系统具有曝光剂量小、图像质量佳等饰点,其甲级片率达到91.3%。结论根尖片数字化直接成像系统DR的优势明显,是未来根尖片数字化技术的主要发展方向。     

数字x线摄影在放射科应用优势的探讨

目的将数字x线摄影（Digital Radiography, DR） 与普通x线摄影进行比较,探讨DR在放射科应用的优势。方法采用线对测试板分别测量DR和普通X线片的空间分辨率,并通过对1000例DR和1000例普通x线摄取的正位胸片中,在图像质量、照射剂量、废片率方面进行对比,分析DR系统的优势。结果与普通x线摄影相比,DR具有高灵敏度、高DQE（量子检测效率）、高空间分辨率的特点;它的采集速度快,x线转换效率快,后处理功能强大,病变检出率高。结论DR在各方面明显优于普通x线摄影,具有广阔的应用前景。     

Pre-processed image reconstruction applied to breast and brain MR imaging

Magnetic resonance imaging (MRI) has emerged as a powerful tool in medical diagnosis and research. Although high spatial resolution images are essential in medical diagnosis and image analysis, high temporal resolution is equally important in applications of dynamic contrast-enhanced MRI or functional brain MRI. In particular, in breast MRI the ability to differentiate between benign and malignant lesions depends, in part, on the temporal resolution of the dynamic image acquisition. New applications of MRI such as multi-feature analysis of image time series data and full 3D functional MRI or event-related functional MRI require high spatial and high temporal resolution for accurate image analysis on a voxel-by-voxel basis. Currently available partial Fourier reconstruction techniques. which effectively improve the time resolution, suffer from a reduced signal to noise ratio in the reconstructed image, a decrease in spatial resolution or reconstruction artefacts, making numerical image analysis difficult. In this work we present an image reconstruction algorithm based on image recovery theory which effectively doubles the temporal resolution and results in an image quality sufficient for further numerical analysis. The developed algorithm requires a full Fourier space acquisition of a pre-contrast or baseline image prior to the reconstruction procedure of the time series partial Fourier data.     

Performance Evaluation of Stationary and Semi-Stationary Acquisition with a Non-Stationary Small Animal Multi-Pinhole SPECT System

Purpose

Step-and-shoot mode with many angular steps results in long frame duration limiting the capability of single-photon emission computed tomography (SPECT) for fast dynamic scans. The present study evaluates acquisition with reduced angular sampling for fast imaging in preclinical research with the nanoSPECT/CTplus four-head multi-pinhole system.

Procedures

Measurements with line sources, homogeneity phantoms and a Jaszczak phantom filled with ^99mTc or ¹²³I were performed to evaluate the ‘stationary’ and ‘semi-stationary’ acquisition mode (one or two detector positions, respectively) with respect to spatial resolution, quantification, noise properties and image artefacts. An in vivo mouse study was performed with ^99mTc-MAG3.

Results

The fast acquisition modes resulted in only minor degradation of spatial resolution and quantification accuracy. Statistical noise in reconstructed images was significantly reduced compared to conventional SPECT, particularly at low count statistics. Stationary acquisition resulted in streak artefacts and spatial distortion.

Conclusions

The semi-stationary acquisition mode of the nanoSPECT/CTplus allows fast dynamic SPECT with tolerable loss of image quality.     

Video-rate full-ring ultrasound and photoacoustic computed tomography with real-time sound speed optimization

Full-ring dual-modal ultrasound and photoacoustic imaging provide complementary contrasts, high spatial resolution, full view angle and are more desirable in pre-clinical and clinical applications. However, two long-standing challenges exist in achieving high-quality video-rate dual-modal imaging. One is the increased data processing burden from the dense acquisition. Another one is the object-dependent speed of sound variation, which may cause blurry, splitting artifacts, and low imaging contrast. Here, we develop a video-rate full-ring ultrasound and photoacoustic computed tomography (VF-USPACT) with real-time optimization of the speed of sound. We improve the imaging speed by selective and parallel image reconstruction. We determine the optimal sound speed via co-registered ultrasound imaging. Equipped with a 256-channel ultrasound array, the dual-modal system can optimize the sound speed and reconstruct dual-modal images at 10 Hz in real-time. The optimized sound speed can effectively enhance the imaging quality under various sample sizes, types, or physiological states. In animal and human imaging, the system shows co-registered dual contrasts, high spatial resolution (140 µm), single-pulse photoacoustic imaging (< 50 µs), deep penetration (> 20 mm), full view, and adaptive sound speed correction. We believe VF-USPACT can advance many real-time biomedical imaging applications, such as vascular disease diagnosing, cancer screening, or neuroimaging.     

CR下肢全长图像拼接摄影参数的探讨

目的探讨数字化X线成像系统（CR）在下肢全长图像拼接的摄影参数。方法以FCR一5000CR成像系统的应用及CR在骨骼系统摄影条件的成像特性,来选择合适的下肢全长骨骼数字化X线的摄影条件。结果根据不同摄影参数下的空间分辨率分布情况,获取优化的CR下肢全长摄影的管电压和毫安量参数。结论CR下肢全长图像拼接的摄影条件,应根据CR成像系统的特性,以实验结果为依据,在保证影像质量和患者受辐射剂量上选择最为适宜的摄影参数。     

Digital subtraction angiography of the coronary arteries

The application of digital coronary arteriography in the evaluation of patients with known or suspected coronary artery disease is considered. Digital imaging of coronary arteries and bypass grafts can augment 35-mm cineangiography and may eventually replace film for coronary arteriography. The clinical efficacy of both selective and nonselective digital coronary arteriography is not yet established, however, a number of advantages over 35 mm cine have now been delineated including high contrast sensitivity image subtraction and digital image processing. One particular advantage of digital coronary arteriography is the ability to perform an immediate quantitative analysis of coronary images providing a reliable and consistent measure of the significance of a stenotic lesion. Technical requirements for digital coronary arteriography include a high output X-ray generator, low noise television chain, a 512 X 512 digital image matrix, frame rates of at least 15 fps, and high data storage capacity of c500 megabytes. The utilization of digital coronary imaging as a supplement or in place of 35-mm cine angiography will provide improved coronary imaging and enable quantification for more accurate and clinically significant coronary artery imaging.     

Impact of image spatial, temporal, and velocity resolutions on cardiovascular indices derived from color-Doppler echocardiography

Quantitative processing of color-Doppler echocardiographic images has substantially improved noninvasive assessment of cardiac physiology. Many indices are computed from the velocity fields derived either from color-Doppler tissue imaging (DTI), such as acceleration, strain and strain-rate, or from blood-flow color-Doppler, such as intracardiac pressure gradients (ICPG). All of these indices are dependent on the finite resolution of the ultrasound scanner. Therefore, we developed an image-dependent method for assessing the influence of temporal, spatial, and velocity resolutions, on cardiovascular parameters derived from velocity images. In order to focus our study on the spatial, temporal, and velocity resolutions of the digital image, we did not consider the effect of other sources of noise such as the interaction between ultrasound and tissue. A simple first-order Taylor's expansion was used to establish the functional relationship between the acquired image velocity and the calculated cardiac index. Resolutions were studied on: (a) myocardial acceleration, strain, and strain-rate from DTI, and (b) ICPG from blood-flow color-Doppler. The performance of Taylor's-based error bounds (TBEB) was demonstrated on simulated models and illustrated on clinical images. Velocity and temporal resolution were highly relevant for the accuracy of DTI-derived parameters and ICPGs. TBEB allow to assess the effects of ideal digital image resolution on quantitative cardiovascular indices derived from velocity measurements obtained by cardiac imaging techniques.     

婴幼儿胸部低剂量dr摄影的探讨

目的:探讨婴幼儿胸部低剂量DR( Digital Radiography)摄影的合理曝光技术条件,降低被检者的曝光量(mAs)及辐射剂量并保证影像质量.材料与方法:随机选取2011年7月-9月来我院进行胸部DR摄影的2岁以下婴幼儿60例作为研究对象,年龄3天-21个月,平均年龄5.5个月,性别随机;30例常规剂量组,采用系统设定的固定婴幼儿胸部摄影条件(65kV、4mAs、4.44 ms),30例低剂量组,采用90kV、AEC自动曝光模式进行自动曝光,自动曝光控制灵敏度均选择400.记录两组曝光参数并进行统计学处理.结果:90kV比65kV摄影曝光量最高降低5.37倍,最低降低2.61倍,平均降低3.69倍;剂量面积值(DAP)最高降低4.04倍,最低降低1.38倍,平均降低1.98倍;对两组mAs进行配对t检验,t=70.5,p＜0.0005,有显著统计学意义,对两组DAP进行配对t检验,t =52,p＜0.0005,有显著统计学意义;对两组影像质量进行x2检验,x2=0.6,p＞0.05,无统计学意义.结论:2岁以下婴幼儿胸部DR摄影千伏宜选用90kV,能降低被检者的mAs及辐射剂量,且影像质量和常规剂量组比较无明显差异.     

Comparison of physiological noise at 1.5 T, 3 T and 7 T and optimization of fMRI acquisition parameters

Previous studies have shown that under some conditions, noise fluctuations in an fMRI time-course are dominated by physiological modulations of the image intensity with secondary contributions from thermal image noise and that these two sources scale differently with signal intensity, susceptibility weighting (TE) and field strength. The SNR of the fMRI time-course was found to be near its asymptotic limit for moderate spatial resolution measurements at 3 T with only marginal gains expected from acquisition at higher field strengths. In this study, we investigate the amplitude of image intensity fluctuations in the fMRI time-course at magnetic field strengths of 1.5 T, 3 T, and 7 T as a function of image resolution, flip angle and TE. The time-course SNR was a similar function of the image SNR regardless of whether the image SNR was modulated by flip angle, image resolution, or field strength. For spatial resolutions typical of those currently used in fMRI (e.g., 3 x 3 x 3 mm(3)), increases in image SNR obtained from 7 T acquisition produced only modest increases in time-course SNR. At this spatial resolution, the ratio of physiological noise to thermal image noise was 0.61, 0.89, and 2.23 for 1.5 T, 3 T, and 7 T. At a resolution of 1 x 1 x 3 mm(3), however, the physiological to thermal noise ratio was 0.34, 0.57, and 0.91 for 1.5 T, 3 T and 7 T for TE near T2*. Thus, by reducing the signal strength using higher image resolution, the ratio of physiologic to image noise could be reduced to a regime where increased sensitivity afforded by higher field strength still translated to improved SNR in the fMRI time-series.     

Performance characteristics of a laser scanner and laser printer system for radiological imaging

This paper describes the performance characteristics of a laser scanner and laser printer system for radiological imaging. The laser scanner can digitize a 14″ × 17″ X-ray film to 2000 × 2400 x 10 bit in about 100 s. The laser printer can format 16 images on a 8″ × 10″ or 14″ × 17″ film with up to 2300 × 3050 × 8 bit resolution in about 50 s. Our experiments show that the laser scanner and the laser printer have a spatial resolution of 3 cycles/mm with excellent spatial linearity and flat field response. This system is a major component of a picture archiving and communication system in a digital-based radiology department. As a stand-alone system, it has certain clinical applications such as a contrast enhancement of radiographs and potential dose reduction to the patient.     

The Acceptability of Iterative Reconstruction Algorithms in Head CT: An Assessment of Sinogram Affirmed Iterative Reconstruction (SAFIRE) vs. Filtered Back Projection (FBP) Using Phantoms

BackgroundComputed tomography (CT) is the primary imaging investigation for many neurologic conditions with a proportion of patients incurring cumulative doses. Iterative reconstruction (IR) allows dose optimization, but head CT presents unique image quality complexities and may lead to strong reader preferences.ObjectivesThis study evaluates the relationships between image quality metrics, image texture, and applied radiation dose within the context of IR head CT protocol optimization in the simulated patient setting. A secondary objective was to determine the influence of optimized protocols on diagnostic confidence using a custom phantom.Methods and SettingA three-phase phantom study was performed to characterize reconstruction methods at the local reference standard and a range of exposures. CT numbers and pixel noise were quantified supplemented by noise uniformity, noise power spectrum, contrast-to-noise ratio (CNR), high- and low-contrast resolution. Reviewers scored optimized protocol images based on established reporting criteria.ResultsIncreasing strengths of IR resulted in lower pixel noise, lower noise variance, and increased CNR. At the reference standard, the image noise was reduced by 1.5 standard deviation and CNR increased by 2.0. Image quality was maintained at ≤24% relative dose reduction. With the exception of image sharpness, there were no significant differences between grading for IR and filtered back projection reconstructions.ConclusionsIR has the potential to influence pixel noise, CNR, and noise variance (image texture); however, systematically optimized IR protocols can maintain the image quality of filtered back projection. This work has guided local application and acceptance of lower dose head CT protocols.     

Comparison of linear array B-mode scanning and computed synthetic aperture ultrasonographic imaging.

The current trend in ultrasonography is toward digital systems that allow more freedom in beam formation and produce improved images. In this paper, conventional linear array B-mode sonograms of a tissue-mimicking phantom are compared to sonograms obtained with a synthetic aperture technique employing numerical image focusing. Sonograms in both cases were obtained using the same equipment to ensure identical imaging conditions. The computed synthetic aperture approach produced uniform spatial resolution of about 1 mm, which could not be achieved with the B-scan technique. In addition, the contrast resolution of the computed synthetic aperture method was found to be superior. We conclude that the computed synthetic aperture method is feasible for real-time clinical applications.     

Phantom-based comparison of conventional versus phase-contrast mammography for LCD soft-copy diagnosis

Purpose

Liquid crystal display (LCD) of mammograms provides soft-copy results that differ in conventional and phase contrast mammography (PCM). PCM potentially offers the highest quality of sharpness and graininess, an edge emphasis effect on the object, and the highest image resolution. However, when the image is displayed on an LCD, the resolution depends on the pixel pitch and the PCM image data must be diminished. We investigated the observed effect on spatial resolution and contrast when conventional or phase contrast mammograms are viewed on an LCD.

Methods

Using the tissue-equivalent phantom (Model 1011A), a conventional mammogram and a magnification radiography image were obtained with a PCM system. This phantom contains simulated fibers, microcalcifications, and masses. The PCM image was reduced 1/1.75 to render it consistent with life size mammography using the nearest neighbor, bilinear, and bicubic interpolation methods. The images were displayed on a five million (5M)-pixel LCD with 100 % magnification. Ten mammography technicians observed the reduction images displayed on LCDs and reported their results.

Results

In the detectability of the microcalcifications, there was no significant difference between conventional mammograms and reduced PCM images. Regarding fibers and masses, detectability using reduced images was higher than those of conventional images. The detectability using images reduced by the nearest-neighbor method was lower than those of images reduced by two other interpolation methods. Bilinear interpolation was affected by the smoothing effect, while CNR was increased. In addition, since the noise of PCM image was reduced by an air gap effect, high detectability of key image features was found.

Conclusions

Soft-copy display of phase-contrast mammograms is feasible with LCDs, while detectability of fibers and masses was best with bilinear interpolation and use of an air gap.     

0.5 gigapixel microscopy using a flatbed scanner

The capability to perform high-resolution, wide field-of-view (FOV) microscopy imaging is highly sought after in biomedical applications. In this paper, we report a wide FOV microscopy system that uses a closed-circuit-television (CCTV) lens for image relay and a flatbed scanner for data acquisition. We show that such an imaging system is capable of capturing a 10 mm × 7.5 mm FOV image with 0.78 µm resolution, resulting in more than 0.5 billion pixels across the entire image. The resolution and field curve of the proposed system were characterized by imaging a USAF resolution target and a hole-array target. To demonstrate its application, 0.5 gigapixel images of histology slides were acquired using this system.OCIS codes: (120.4820) Optical systems, (170.0180) Microscopy, (170.4730) Optical pathology     

深度学习CT图像迭代重建及其用于儿童CT进展

人工智能在分割、重建医学及图像处理等方面均发挥重要作用。儿童CT检查应遵循尽可能低辐射剂量原则，即在低辐射剂量下最大限度保持或获得更高图像质量。本文对基于人工智能的深度学习CT图像迭代重建技术及其用于儿童CT进展进行综述。     

DR在胸部肋骨骨折诊断技术中的应用

目的探讨数字化摄影在胸部肋骨骨折诊断的应用价值及摄影方法。方法选取50例临床高度怀疑肋骨骨折的病例,采用3种成像方式：①AEc高千伏摄影直接传送;②高千伏摄影图像经肋骨化后处理传送;③检查时采用低千伏肋骨摄影。3种方法所成图像进行评价并对辐射剂量的比较。结果3种方式所成图像对骨折的检出率不同,AEC高千伏摄影对肋骨的显示及骨折的诊断准确性低,而辐射剂量较低,经过后处理的图像对肋骨的显示相对较好,辐射剂量较低;低千伏肋骨摄影对肋骨显示效果好,诊断准确性高,辐射剂量较大。结论直接数字化摄影图像经适当的后处理能提高骨折诊断的准确性而不增加辐射剂量,必要时增加辐射剂量能达到比较理想的效果。     

Spatially variable Rician noise in magnetic resonance imaging

Magnetic resonance images tend to be influenced by various random factors usually referred to as "noise". The principal sources of noise and related artefacts can be divided into two types: arising from hardware (acquisition coil arrays, gradient coils, field inhomogeneity); and arising from the subject (physiological noise including body motion, cardiac pulsation or respiratory motion). These factors negatively affect the resolution and reproducibility of the images. Therefore, a proper noise treatment is important for improving the performance of clinical and research investigations. Noise reduction becomes especially critical for the images with a low signal-to-noise ratio, such as those typically acquired in diffusion tensor imaging at high diffusion weightings. The standard methods of signal correction usually assume a uniform distribution of the standard deviation of the noise across the image and evaluate a single correction parameter for the whole image. We pursue a more advanced approach based on the assumption of an inhomogeneous distribution of noise in space and evaluate correction factors for each voxel individually. The Rician nature of the underlying noise is considered for low and high signal-to-noise ratios. The approach developed here has been examined using numerical simulations and in vivo brain diffusion tensor imaging experiments. The efficacy and usefulness of this approach is demonstrated here and the resultant effective tool is described.