Evaluation of the usefulness of color digital summation radiography in temporally sequential digital radiographs: a phantom study

Purpose The purpose of this study was to assess the usefulness of color digital summation radiography (CDSR) for detection of nodules on chest radiographs by observers with different levels of experience. Materials and methods A total of 30 radiographs of chest phantoms with abnormalities and 30 normal ones were arranged at random. Set A was conventional radiographs only. Set B consisted of both conventional radiographs and CDSR images, which were colored with magenta. Five chest radiologists and five residents evaluated both image sets on a TFT monitor. The observers were asked to rate each image set using a continuous rating scale. The reading time for each set was also recorded. Results In set A, the performance of chest radiologists was significantly superior to that of the residents (P < 0.05). However, in set B, there was no significant difference in the performance of the chest radiologists and the residents. In both observer groups, the mean reading time per case in set B was significantly shorter than that in set A (P < 0.01). Conclusion By using CDSR, the detection capability of observers with little experience improves and is comparable to that of experienced observers. Moreover, the reading time becomes much shorter using CDSR.     

3.0 T磁共振多体素质子波谱脂质在胶质瘤恶性程度分级的应用

目的研究多体素质子波谱对幕上胶质瘤术前分级的临床应用价值。资料与方法35例经手术及病理证实的幕上胶质瘤采用3.0T超导型磁共振成像/波谱一体化扫描系统,常规MR及多体素波谱检查后利用Functool软件进行分析。结果35例胶质瘤,按WHO标准分类Ⅱ级14例,Ⅲ级11例,Ⅳ级10例。Ⅱ级组、Ⅲ级组、Ⅳ级组肿瘤实体区(Lac Lip)/Cr平均值分别为0.15±0.16,1.14±1.50,2.61±2.75,NAA/nCr平均值1.29±0.96,0.74±0.56,0.53±0.36和(Lac Lip)/nCr平均值0.22±0.23,0.70±0.63,1.01±0.80,Ⅱ级组与Ⅳ级组间(Lac Lip)/Cr、(Lac Lip)/nCr、NAA/nCr有统计学差异(P<0.05)。若将Ⅱ级组列为低度恶性肿瘤组,Ⅲ级组、Ⅳ级组合并为高度恶性肿瘤组,Cho/NAA、Cho/Cr、(Lac Lip)/Cr、(Lac Lip)/nCr平均值在组间有显著性差异。结论MR多体素质子波谱脂质的出现对肿瘤组织学分级有较高的临床应用价值。     

The sorptivity and durability of gelling fibre dressings tested in a simulated sacral pressure ulcer system

Wound‐dressing performances are affected by exudate viscosity, resistance to flow because of gravity, and bodyweight loads, the level of which is related to the body position. Here, we focussed on two dressing properties: (a) Sorptivity—the ability of dressings to transfer exudate away from the wound bed by capillary action—and (b) Durability—the capacity of dressings to maintain their integrity over time and during their removal. Both properties are critically important for avoiding further tissue damage but require the development of new laboratory tests for their measurement. A computer‐controlled phantom of an exuding sacral pressure ulcer has therefore been developed and used to compare the performances of Exufiber (Mölnlycke Health Care) vs an alternative market‐leading dressing. Sorptivity was determined using weight tests, and durability was measured through tensile tests of the used dressings. For a supine configuration, the Exufiber dressing demonstrated ~three times higher sorptivity and better durability, withstanding ~five times greater strain energy than the other product before failure occurred. This work paves the way for quantitative, standardised testing of dressings in all aspects of exudate management. The reported tests are further suitable for testing dressing combinations or how dressings interact with negative pressure wound therapy.     

Assessment of calcium scoring performance in cardiac computed tomography

Electron beam tomography (EBT) has been used for cardiac diagnosis and the quantitative assessment of coronary calcium since the late 1980s. The introduction of mechanical multi-slice spiral CT (MSCT) scanners with shorter rotation times opened new possibilities of cardiac imaging with conventional CT scanners. The purpose of this work was to qualitatively and quantitatively evaluate the performance for EBT and MSCT for the task of coronary artery calcium imaging as a function of acquisition protocol, heart rate, spiral reconstruction algorithm (where applicable) and calcium scoring method. A cardiac CT semi-anthropomorphic phantom was designed and manufactured for the investigation of all relevant image quality parameters in cardiac CT. This phantom includes various test objects, some of which can be moved within the anthropomorphic phantom in a manner that mimics realistic heart motion. These tools were used to qualitatively and quantitatively demonstrate the accuracy of coronary calcium imaging using typical protocols for an electron beam (Evolution C-150XP, Imatron, South San Francisco, Calif.) and a 0.5-s four-slice spiral CT scanner (Sensation 4, Siemens, Erlangen, Germany). A special focus was put on the method of quantifying coronary calcium, and three scoring systems were evaluated (Agatston, volume, and mass scoring). Good reproducibility in coronary calcium scoring is always the result of a combination of high temporal and spatial resolution; consequently, thin-slice protocols in combination with retrospective gating on MSCT scanners yielded the best results. The Agatston score was found to be the least reproducible scoring method. The hydroxyapatite mass, being better reproducible and comparable on different scanners and being a physical quantitative measure, appears to be the method of choice for future clinical studies. The hydroxyapatite mass is highly correlated to the Agatston score. The introduced phantoms can be used to quantitatively assess the performance characteristics of, for example, different scanners, reconstruction algorithms, and quantification methods in cardiac CT. This is especially important for quantitative tasks, such as the determination of the amount of calcium in the coronary arteries, to achieve high and constant quality in this field. Electronic Publication     

Evaluation of accuracy in MS lesion volumetry using realistic lesion phantoms

RATIONALE AND OBJECTIVES: Quantitative analysis of such small structures as focal lesions in patients with multiple sclerosis (MS) is an important issue in both diagnosis and therapy monitoring. To reach clinical relevance, the reproducibility and accuracy of a proposed method have to be validated. We propose a framework for the generation of realistic digital phantoms of MS lesions of known volumes and their incorporation into a magnetic resonance (MR) data set of a healthy volunteer. MATERIALS AND METHODS: We generated 54 data sets from a multispectral brain scan of a healthy volunteer with incorporated MS lesion phantoms. Lesion phantoms were created using different shapes (three), sizes (six), and orientations (three). An evaluation is carried out from a manual analysis of three human experts and two different semiautomatic approaches, with and without explicit modeling of partial volume effects (PVEs). RESULTS: Intraobserver and interobserver studies were performed for the phantom data sets. All experts overestimated the true lesion volume for any phantom data set (median overestimation between 42.9% and 63.2%). Relative error and variability increased with decreasing lesion size. Similar results were obtained for the semiautomatic approach without PVE modeling. Only the approach with explicit PVE modeling was capable of generating accurate volumetric results with low systematic error. CONCLUSION: The proposed framework based on realistic lesion phantoms incorporated into an MR scan allows for quantitative assessment of the accuracy of manual and automated lesion volumetry. Results clearly show the importance of an improved gold standard in lesion volumetry beyond voxel counting.     

Calculation of MRI-induced heating of an implanted medical lead wire with an electric field transfer function

PURPOSE: To develop and demonstrate a method to calculate the temperature rise that is induced by the radio frequency (RF) field in MRI at the electrode of an implanted medical lead. MATERIALS AND METHODS: The electric field near the electrode is calculated by integrating the product of the tangential electric field and a transfer function along the length of the lead. The transfer function is numerically calculated with the method of moments. Transfer functions were calculated at 64 MHz for different lengths of model implants in the form of bare wires and insulated wires with 1 cm of wire exposed at one or both ends. RESULTS: Heating at the electrode depends on the magnitude and the phase distribution of the transfer function and the incident electric field along the length of the lead. For a uniform electric field, the electrode heating is maximized for a lead length of approximately one-half a wavelength when the lead is terminated open. The heating can be greater for a worst-case phase distribution of the incident field. CONCLUSION: The transfer function is proposed as an efficient method to calculate MRI-induced heating at an electrode of a medical lead. Measured temperature rises of a model implant in a phantom were in good agreement with the rises predicted by the transfer function. The transfer function could be numerically or experimentally determined.     

医学体视化的三维旋转绘制法

目的 实现三维医学图像数据场的快速旋转体绘制。方法 由源一衰减模型、朗伯漫反射余弦定律和Phong镜面反射模型，推导出计算数据场中每一点的不透明度和明暗度的计算公式,通过旋转光源和视点,来自不同观察方向的感兴趣结构的体绘图被满意地生成。结果 通过对人体头部CT图像数据场进行三维旋转绘制，结果比较理想。结论 由于不需要对整个数据场进行分类和旋转，该方法具有速度快、所需内存少和绘制质量高的特点，是一种较好的医学体视化方法。     

A new flood phantom to measure homogeneity of gamma cameras and to correct SPECT studies

A new flood phantom is presented. It combines patient like emission spectra, homogeneous activity distribution, and mechanical stability.Its properties and easy handling makes it the flood phantom of choice for measuring the homogeneity of a gamma camera or for correcting SPECT studies.     

低场磁共振FLAIR序列对脑脊液内钆剂浓度检出的实验研究

 目的 探讨低场磁共振液体衰减反转恢复序列T2WI对人工脑脊液(cerebral spinal fluid,CSF)内钆浓度的识别水平,为临床应用提供依据.方法 采用浓度0～8 mmol/L的Gd-DTPA人工CSF溶液模拟CSF内不同的强化水平,新鲜熟蛋清模拟正常脑实质.使用0.35T机型,对样本分别行SE序列T1WI和快速FLAIR序列T2WI扫描,测算出各被检样本与参照样本间的对比噪声比(contrast-to-noise ratios,CNR),比较两种成像序列所能检出的最低钆剂浓度.结果 FLAIR序列T2WI所能识别的最低钆剂浓度为0.0078 mmol/L,比SE序列T1WI约低10倍;当样本内钆剂浓度超过0. 8 mmol/L时,FLAIR序列T2WI的检出能力不及SE序列T1WI.结论 低场磁共振FLAIR序列T2WI对人工CSF内低浓度钆剂的检出能力明显优于其SE序列T1WI.     

Radionuclide left ventricular volume determination. Influence of scattered radiation and surrounding activity

Summary. Radionuclide measurements of left ventricular volumes, ejection fractions and stroke volumes were performed by an equilibrium technique in nine patients using left anterior oblique projection and individual depth correction. Phantom studies were made in order to evaluate attenuation and scattering of the radiation. It was found that a simple depth correction factor, k(d)= e^μd, can be used under certain conditions. However, the determination of left ventricular volume by radionuclide techniques is not a truly absolute method. The depth correction factor to be used is dependent on the condition of measuring and evaluation, for instance how the region of interest for the left ventricle is selected. Therefore, this method should be carefully standardized, evaluated and compared to other techniques. Stroke volume measured by radionuclide and dye-dilution technique showed a correlation coefficient of 0·76 (nine patients) at rest and 0·77 (seven patients) at work. This method can be easily performed during routine ejection fraction determination and can thus be useful in clinical studies.