A radiomics pipeline dedicated to Breast MRI: validation on a multi-scanner phantom study

Magnetic Resonance Materials in Physics, Biology and Medicine - Quantitative analysis in MRI is challenging due to variabilities in intensity distributions across patients, acquisitions and...     

Effects of bolus injection duration on perfusion estimates in dynamic CT and dynamic susceptibility contrast MRI

Estimates of cerebral blood flow (CBF) and tissue mean transit time (MTT) have been shown to differ between dynamic CT perfusion (CTP) and dynamic susceptibility contrast MRI (DSC-MRI). This study investigates whether these discrepancies regarding CBF and MTT between CTP and DSC-MRI can be attributed to the different injection durations of these techniques. Five subjects were scanned using CTP and DSC-MRI. Region-wise estimates of CBF, MTT, and cerebral blood volume (CBV) were derived based on oscillatory index regularized singular value decomposition. A parametric model that reproduced the shape of measured time curves and characteristics of resulting perfusion parameter estimates was developed and used to simulate data with injection durations typical for CTP and DSC-MRI for a clinically relevant set of perfusion scenarios and noise levels. In simulations, estimates of CBF/MTT showed larger negative/positive bias and increasing variability for CTP when compared to DSC-MRI, especially for high CBF levels. While noise also affected estimates, at clinically relevant levels, the injection duration effect was larger. There are several methodological differences between CTP and DSC-MRI. The results of this study suggest that the injection duration is among those that can explain differences in estimates of CBF and MTT between these bolus tracking techniques.

     

A study on the accuracy of surface charge measurement

The measurement of accumulated surface charge for thick specimens requires multipoint probe outputs to establish the inverse calculation for the determination of an unknown charge distribution. Until now, studies on the various errors associated with the measurement have been conducted only for simplified arrangements mainly in axisymmetric geometry where the charged surface is parallel to the ground. We have numerically analyzed a model measurement set-up more comparable to practical conditions by a highly efficient surface charge method. We have studied the effect of probe position, the induction from charge existing not directly beneath the (probe) sensor and the difference in matrix components computed by two numerical methods. In particular, we have studied the accuracy of the reconstructed charge distributions by numerical simulations of the inverse calculation. It has been shown that the assumed measurement errors make much larger differences in the reconstructed charge distributions, although the influence depends considerably on the assumed charge distribution. Reducing the condition number of the matrix improves the accuracy of the inverse calculation for uniform and linearly changing charge distributions     

A novel framework for evaluating the image accuracy of dynamic MRI and the application on accelerated breast DCE MRI

Objective

To develop a novel framework for evaluating the accuracy of quantitative analysis on dynamic contrast-enhanced (DCE) MRI with a specific combination of imaging technique, scanning parameters, and scanner and software performance and to test this framework with breast DCE MRI with Time-resolved angiography WIth Stochastic Trajectories (TWIST).

Materials and methods

Realistic breast tumor phantoms were 3D printed as cavities and filled with solutions of MR contrast agent. Full k-space raw data of individual tumor phantoms and a uniform background phantom were acquired. DCE raw data were simulated by sorting the raw data according to TWIST view order and scaling the raw data according to the enhancement based on pharmaco-kinetic (PK) models. The measured spatial and temporal characteristics from the images reconstructed using the scanner software were compared with the original PK model (ground truth).

Results

Images could be reconstructed using the manufacturer’s platform with the modified ‘raw data.’ Compared with the ‘ground truth,’ the RMS error in all images was <10% in most cases. With increasing view-sharing acceleration, the error of the initial uptake slope decreased while the error of peak enhancement increased. Deviations of PK parameters varied with the type of enhancement.

Conclusion

A new framework has been developed and tested to more realistically evaluate the quantitative measurement errors caused by a combination of the imaging technique, parameters and scanner and software performance in DCE-MRI.

     

Quantitative T 2 measurement of a single voxel with arbitrary shape using pinwheel excitation and CPMG acquisition

Objective The aim of this study is to present a new approach for making quantitative single-voxel T ₂ measurements from an arbitrarily shaped region of interest (ROI), where the advantage of the signal-to-noise ratio (SNR) per unit time of the single-voxel approach over conventional imaging approach can be achieved. Materials and methods Two-dimensional (2D) spatially selective radiofrequency (RF) pulses are proposed in this work for T ₂ measurements based on using interleaved spiral trajectories in excitation k-space (pinwheel excitation pulses), combined with a summed Carr–Purcell Meiboom–Gill (CPMG) echo acquisition. The technique is described and compared to standard multi-echo imaging methods, on a two-compartment water phantom and an excised brain tissue. Results The studies show good agreement between imaging and our method. The measured improvement factors of SNR per unit time of our single-voxel approach over imaging approach are close to the predicted values. Conclusion Measuring T ₂ relaxation times from a selected ROI of arbitrary shape using a single-voxel rather than an imaging approach can increase the SNR per unit time, which is critical for dynamic T ₂ or multi-component T ₂ measurements.     

基于LabVIEW的振动测试数据采集分析软件平台设计与实现

详细介绍了具有较强拓展性的振动测试数据采集分析的软件平台设计。该软件平台主要通过基于多任务操作的软件架构、活动窗口设计、预留API接口以及硬件通用性设计等方面的设计,保证了软件平台强大的拓展性,从而实现软件平台的通用。基于该平台设计的高层次振动数据分析软件,如模态参数识别和动载荷识别软件,利用该平台已有的功能和软件架构,可以方便地进行二次开发,拓展软件功能,实现更复杂振动数据分析处理,减少重复劳动,加快软件开发进程。设计完成后,通过试验对比和软件开发案例,验证了软件的可行性和可用性。     

Effects of restricted diffusion in a biological phantom: a q-space diffusion MRI study of asparagus stems at a 3T clinical scanner

Introduction The aim of this work was to study the effects of restricted diffusion in a biological phantom consisting of green asparagus stems using q-space MRI at a clinical scanner. Method Measurements of the full width at half maximum (FWHM) of the displacement distribution were performed with varied diffusion time (T _d). The accuracy of the measurements was investigated with respect to the degree of violation of the short gradient pulse (SGP) condition, partial volume effects and a FWHM-based tensor model. Results The measurements showed a reasonably constant FWHM perpendicular to the capillaries in the vascular bundles and an increased FWHM parallel with the bundles when the T _d was increased. A 15% decrease in FWHM perpendicular to the bundles was observed when the diffusion encoding duration was prolonged from 24 to 74 ms, owing to the violation of the SGP condition. For a population of different confinement sizes, simulations indicated that the FWHM reflects the smaller sizes rather then the mean size of the confinements. Conclusion A new method allowing tensor analysis of FWHM was derived and yielded accurate results. In conclusion, we found it possible to measure the effects of restricted diffusion with q-space MRI using a clinical MRI scanner.     

基于DSP的高速数据采集系统设计与实现

设计了一种基于TMS320LF2407 DSP 芯片和14 位A/D芯片MAX125的高速数据采集系统.详细设计了硬件电路的核心部分:交流信号处理电路和AD 转换控制电路,并利用74LVC4245芯片解决了DSP和MAX125的电平匹配问题.本系统还采用了实时操作系统μC/OS-II,并详细设计了系统应用程序的任务模块.实践证明,该系统在采集速度、精度方面具有良好的性能,且结构简单、可靠,成本低廉,将得到广泛的应用.     

测量准确度评估讲座(9)

Appraisingandjudgmentthedegreeofaccuracyonmeasurement(9)QianZhongtai;TongGuangqiu;WangXuewei;MaHuaijian;SongMingsun;GuLongfang(NationalInstituteofMetrology,Beijing100013,China;HarbinUniversityofScienceandTechnology,Harbin150040,China;ChinaInstituteofMetrology,Hangzhou310034,China)8．3“GUM93”附录H例H．l：端度规校准“＊本例分析曾得到中国计量科学研究院蒋勋高级工程师的指导。“GUM93”附录H例H．1的内容如下：用比长仪比较标称值同为SOmm的被校和标准两端度规块的长度,可直接确定其长度差d…     

测量准确度评估讲座(7)

６．３不等精度测量列的数据处理 对被测量Ｙ进行ｍ次不等精度测量,所得结果为Ｙｉ　＋Ｕ（　Ｙｉ）（ｉ＝１－ｍ）,所有ｉ值的误差估计值Ｕ（Ｙｉ）的覆盖因子均相等。对这种测量列应用最小二乘方法可得出下列计权平均值的处理方法。 对数据Ｙｉ取权Ｐｉ为 注意在这样取权的情况下有： 则处理结果表示式将为 这方法同样是应用最小二乘方法的处理结果,因此对任何分布的误差的数据都有效,这就是ＪＪＧ１０２７－９１“规范”４．７条的内容。６．４相关等精度测量列的数据处理 对Ｙ及　Ｑ同时进行ｍ次等精度测量,得到测量列Ｙｉ;,Ｑｉ…     

测量准确度评估讲座(8)

８有关实例８．１概况技术文件的执行者通常非常注意技术规范中的实例。因为实例中的分析和处理很能说明文件某些规定的理由和真实的意图，并表明执行中的难点应该如何解决。本节将通过某些实例来说明本文误差评估方法的实际执行情况。为了便于比较，实例将在“ＧＵＭ９３”的实例中选择。汇总“ＧＵＭ９３”中主要实例，共找到９个实例：包括其正文中３个实例和其附录Ｈ中６个实例。用本文误差评估方法对这些实例重新作评估，结果和“ＧＵＭ９３”结果相符的仅有附录Ｈ中Ｈ．３和Ｈ．５两例，这是两个纯数据处理的实例，而并非完整准确度评…     

测量准确度评估讲座(6)

４．２误差项ＡＹ。极限值的覆盖因子值（续）文献８文章７对本文定义的“极限值”及其直接综合方法的可靠性进行了全面的研究。它延用“一般异常”及“高度异常”两个“可靠性水平”以与目前的统计学标准相兼容。但指出了由于没有反映异常值大小的影响，“显著性水平ａ”...     

VXI总线高速高精度数据采集模块的设计与实现

介绍了一种基于VXI总线C尺寸，高速、高精度数据采集模块的软硬件设计与实现。该模块建立在一种新的模块化VXI仪器平台VVP（VXI，Versatile Plug-in)上，中央处理器采用SHARC DSP进行实时数字信号处理，基板使用FPGA实现VXI总线与DSP的桥接，数据以DMA方式传输，时序和逻辑电路由CPLD实现，上位机软件采用了虚拟内存技术，用户程序可以灵活方便地从上位机下载。     

High-resolution 3D whole-heart coronary MRA: a study on the combination of data acquisition in multiple breath-holds and 1D residual respiratory motion compensation

Object

To study a scan protocol for coronary magnetic resonance angiography based on multiple breath-holds featuring 1D motion compensation and to compare the resulting image quality to a navigator-gated free-breathing acquisition. Image reconstruction was performed using L1 regularized iterative SENSE.

Materials and methods

The effects of respiratory motion on the Cartesian sampling scheme were minimized by performing data acquisition in multiple breath-holds. During the scan, repetitive readouts through a k-space center were used to detect and correct the respiratory displacement of the heart by exploiting the self-navigation principle in image reconstruction. In vivo experiments were performed in nine healthy volunteers and the resulting image quality was compared to a navigator-gated reference in terms of vessel length and sharpness.

Results

Acquisition in breath-hold is an effective method to reduce the scan time by more than 30 % compared to the navigator-gated reference. Although an equivalent mean image quality with respect to the reference was achieved with the proposed method, the 1D motion compensation did not work equally well in all cases.

Conclusion

In general, the image quality scaled with the robustness of the motion compensation. Nevertheless, the featured setup provides a positive basis for future extension with more advanced motion compensation methods.     

基于ISA总线的数据采集卡的设计及应用

本文介绍了基于ISA总线的数据采集卡的硬件电路和软件设计。针对传统数据采集卡中电压测量电路的零点校正和满刻度校正是用滑动变阻器来实现的,设计了一种新的采用D/A转换芯片、存储器和集成运算放大器的电路,代替了传统的滑动变阻器校正方法,实现了自动校正,提高了调整精度。采用新的校正电路的另一个优点是可以采用各种非线性校准技术,对电压测量电路的非线性进行自动校准。     

基于DSP和FPGA的高速数据采集系统的设计及实现

本文设计了一种基于DSP和FPGA的双通道通用数据采集系统,每个通道的采样率为10 MSps,采样精度为14 b.设计中采用了FPGA实现2个异步FIFD作为模数转换器AD9240和数字信号处理器TMS320C6416的缓存器,并且FPGA内部可方便地实现各种逻辑电路与外围进行通信.数据的传输采用EDMA,实现了大容量数据的传输.实验结果表明,该数据采集系统有较高的采样精度,具有接口电路简单、可靠性高、调试方便等特点,可广泛应用于通信和图形采集中.     

基于TMS320LF2407的高速数据采集系统设计与实现

设计了一种基于TI公司生产的TMS320LF2407 DSP芯片和14位A/D芯片MAX 125的实时数据采集系统.设计了硬件电路的核心部分:电流电压的信号处理电路和AD转换控制电路.详细介绍了AD转换的控制和实现过程的软件实现方法.最后对该数据采集系统进行了测试,结果表明该系统在精度、采集速度和同步采样方面具有良好的性能,且结构简单,成本低廉.该系统将得到广泛的使用.     

VME数据采集模块设计与校准方法研究

数据采集模块是自动化测试系统的重要组成部分,其采集数据是否准确直接影响到整个测试系统的性能.主要介绍了基于VME总线的数据采集模块的设计和采用FPGA实现数据采集控制与校准.为了提高数据采集模块的转换精度和校准速度,用最小二乘线性拟合的方法设计模块的校准参数并且在FPGA内部实现校准模型.实验表明该校准方法能快速有效地...