Influence of the mediastinum on the measurement of esophageal pressure and lung compliance in man

Summary The influence of mediastinal organs on esophageal pressure was estimated in man from the variations of esophageal elastance and amplitude of the cardiac oscillations. From the simultaneous measurements of both parameters and of esophageal pressure at different lung volumes and levels in the esophagus, in the sitting and supine positions, using a 3 and 10 cm long ballon, at rest and during exercise, it was concluded: 1. The difference in measured pulmonary compliance with posture is mainly due to a mediastinal artifact, acting primarily at high lung volumes in the sitting position. In the supine position mediastinal loading is more pronounced but does not vary with lung volume (between 10 and 90% of vital capacity). 2. The vertical esophageal pressure gradient is more pronounced in the lower half of the esophagus. It is probably estimated correctly at that level but underestimated at higher levels. Pressure irregularities observed along the esophagus in the supine position are due to local actions of mediastinal organs. 3. The difference in pressure obtained with balloons of different size can be attributed to the influence of the elastic properties of the esophageal wall, provided one takes into account the vertical pressure gradient, and to shifts in the site of pressure recording in the longer balloon. 4. The increase in pressure without change of pulmonary compliance observed during exercise is also a mediastinal artifact. 5. Extrapolation of esophageal pressure towards zero balloon volume successfully corrects for the influence of posture on pulmonary compliance. However, this procedure does not allow for an estimation of intrathoracic pressure in the presence of a marked mediastinal compression effect.This work was supported by a grant of the High Authority of the European Community for Coal and Steel.     

能谱CT的MONO成像联合MARs技术在颅内弹簧圈植入物伪影的应用研究

目的 评价能谱CT单能量成像(MONO)联合金属伪影去除软件(MARs)技术在去除颅内弹簧圈植入物伪影的临床应用价值.方法 选取15例头部弹簧圈介入术后患者,对其头部进行能谱成像(GSI)扫描,得到1组120 kVp混合能量(QC)图像、40 ～140 keV以10 keV为间隔的共11组MONO图像和11组MONO联合MARs图像.每组图像随机选择1个伪影较严重和1个无伪影的感兴趣区域(ROI),并测量出各自的SD值,并计算出各自伪影指数(AI),对SD值进行配对t检验,并对各自图像进行主观评分(0～3分).结果 120 kVp的QC图像、40～ 140 keV的11组MONO图像和11组MONO联合MARs图像,在60 ～140 keV范围内AI值表现为MONO联合MARs图像低于MONO图像,MONO图像低于QC图像,且MONO图像和MONO联合MARs图像在70 keV达到最低,往后AI值趋于平缓;三组图像的SD值配对t检验中,MONO图像中60 ～ 140 keV与QC图像无显著性差异(P＞0.05),在MONO联合MARs图像中50 keV与QC无显著性差异(P=0.985,＞0.05),而60 ～140 keV存在显著性差异且SD值均值小于QC均值,即MONO联合MARs图像中的60～140 keV组图像噪声明显低于其他组;在主观评价三组图像的配对t检验中,均存在显著性差异(P＜0.05),并且MONO联合MARs图像的70 ～ 90 keV能量范围分别获得(2.85±0.15)、(2.78±0.18)和(2.75 ±0.20)分,远高于其他组.结论 在能谱CT中,MONO联合MARs在70 ～90 keV范围内去除颅内弹簧圈植入物伪影效果最为显著,其中70 keV是临床应用的最佳能量图像.     

The value of paraxial slices in MR-imaging of spinal cord disease

Summary Paraxial slices in MRI of the spinal cord reveal information about anatomical structures and pathological processes not available from orthogonal plane images or other diagnostic methods. They also yield a profit in diminishing the artifacts that occur from heart movement and respiration when triggering is not employed.Supported by the Deutsche Forschungsgemeinschaft     

Utilidad de la tomografía computarizada de energía dual en la reducción del artefacto metálico generado por clips y coils intracraneales

Objective

To assess the ability of dual-energy CT (DECT) to reduce metal-related artifacts in patients with clips and coils in head CT angiography, and to analyze the differences in this reduction between both type of devices.

Utilidad del artefacto Doppler de centelleo de color (twinkle) en la detección ecográfica de microcalcificaciones mamarias

Objective

To determine whether the twinkling artifact on Doppler ultrasound imaging corresponds to microcalcifications previously seen on mammograms and to evaluate the usefulness of this finding in the ultrasound management of suspicious microcalcifications.

“Black Hole Artifacts”—A New Potential Pitfall for DXA Accuracy?

Certain types of metallic objects apparently have high attenuation (a white image) on dual-energy X-ray absorptiometry (DXA) scan images, but instead show up as black (black hole artifacts). When small, these artifacts may easily be missed on visual inspection. We hypothesized that such “black hole” artifacts could have a significant effect on bone mineral density (BMD) results. Human use approval (Institutional Review Board [IRB]) was obtained to publish patient scans and an IRB waiver was obtained for nonhuman research. We placed individual surgical clips and cassettes of clips of tantalum, stainless steel and titanium, and a bullet over the third lumbar vertebra (L3) of a Hologic spine phantom. In addition, 4 or 8 individual tantalum or stainless steel clips and tantalum squares were placed over L3 of cadaveric spines (high-density spine L1–L4 BMD = 1.049 g/cm²) and low-density spine BMD (L1–L4 BMD = 0.669 g/cm²) with attached soft tissues. Stainless steel and titanium clips scanned as white objects with DXA. A bullet and tantalum clips scanned black (black holes). All clip types were visible on single-energy scans as white objects. Eight tantalum clips significantly lowered L3 BMD compared to 4 or 0 clips in the high-density spine. There were no significant differences in BMD L1–L4 between 0, 4, and 8 tantalum clips in the high-density spine. In the low-density spine, 8 tantalum clips over L3 had significantly lower BMD compared to 4 tantalum clips overlying L3 and 4 clips lateral to L3 and 4 clips over L3. All of these scenarios had lower L3 BMD than no tantalum clips overlying L3. The BMD of L1–L4 was lowest with 8 clips at L3, but was not significantly different than no clips overlying L3. Eight tantalum clips lateral to L3 was significantly higher than no clips over L3. Black hole artifacts can occur in DXA scans containing certain metals like tantalum surgical clips. Although these surgical clips could decrease BMD at a localized area, they do not significantly decrease the L1–L4 spine BMD in a high-density spine specimen. In a low-density spine specimen, tantalum clips do have the potential to alter BMD of a single vertebral body and L1–L4. Attention should be paid to the possibility of black hole artifacts on DXA scans and the effect they may have on spine results. Viewing scans in the single-energy mode can be used to verify the presence of tantalum clips.     

Update on multidetector coronary CT angiography of coronary stents: in vitro evaluation of 29 different stent types with dual-source CT

The aim of this study was to test a large sample of the latest coronary artery stents using four image reconstruction approaches with respect to lumen visualization, lumen attenuation, and image noise in dual-source multidetector row CT (DSCT) in vitro and to provide a CT catalogue of currently used coronary artery stents. Twenty-nine different coronary artery stents (19 steel, 6 cobalt-chromium, 2 tantalum, 1 iron, 1 magnesium) were examined in a coronary artery phantom (vessel diameter 3 mm, intravascular attenuation 250 HU, extravascular density −70 HU). Stents were imaged in axial orientation with standard parameters: 32 × 0.6 collimation, pitch 0.24, 400 mAs, 120 kV, rotation time 0.33 s. Image reconstructions were obtained with four different convolution kernels (soft, medium-soft, standard high-resolution, stent-dedicated). To evaluate visualization characteristics of the stent, the lumen diameter, intraluminal density, and noise were measured. The stent-dedicated kernel offered best average lumen visualization (54 ± 8.3%) and most realistic lumen attenuation (222  ± 44 HU) at the expense of increased noise (23.9 ± 1.9 HU) compared with standard CTA protocols (p < 0.001 for all). The magnesium stent showed the least artifacts with a lumen visibility of 90%. The majority of stents (79%) exhibited a lumen visibility of 50–59%. Less than half of the stent lumen was visible in only six stents. Stent lumen visibility largely varies depending on the stent type. Magnesium is by far more favorable a stent material with regard to CT imaging when compared with the more common materials steel, cobalt-chromium, or tantalum. The magnesium stent exhibits a lumen visibility of 90%, whereas the majority of the other stents exhibit a lumen visibility of 50–59%. David Maintz and Matthias Burg contributed equally to this publication.     

First ESHO educational symposium on hyperthermia: Rationale,indications and translational research

A two-parameter method for the estimation of ultrasound-induced temperature artifacts was evaluated and compared with other commonly applied methods using analytical solutions to the bioheat equation. The two parameters are the exponent of the assumed temperature decay curve after power is turned off and the baseline temperature. These parameters are found by optimizing the fit of the temperature data from 30 to 60s after power is turned off. The artifact is modelled as a point source at the centre of a Gaussian temperature distribution. The blood flow, baseline temperature, and variance of the Gaussian temperature distribution were varied to simulate different clinical situations. Noise was added to the model to investigate the effects of thermometry resolution and sampling intervals. It was found that for artifacts of &;lt; 2oC the two-parameter method had errors of less than 0.25oC, whereas other methods generally had greater errors depending on the conduction rate and blood flow rate. The effects of the temperature sampling interval and resolution on the ability of the methods to estimate the artifact were also investigated, and it was found that the two-parameter method was much more sensitive to these parameters than other commonly applied methods.     

CT机时间分辨力的体模测试方法

目的 设计用于测量CT机时间分辨力的方法和相应体模。方法 根据环形伪影产生原理,使含有高密度衰减物的自制时间分辨力均匀体模与CT机架以同样的速度旋转,产生环形伪影,根据环形伪影的角度测量CT机的时间分辨力。结果 当CT机架以0.5 s/240°的扫描速度采集数据时,用自制体模测得CT机的时间分辨力为(0.5002±0.0014)s。结论 实验设计的方法和自制体模可用于测量CT机的时间分辨力。     

计算机断层扫描图像金属伪影校正方法研究现状

临床越来越多的患者接受金属植入手术。由金属植入物产生的金属伪影对利用CT图像进行术后评估与肿瘤诊断造成极大困难,易导致误漏诊。在滤波反投影重建算法、迭代重建算法基础上改进的校正方法近几十年来不断取得新的进展。本文对去除金属伪影技术的发展现状进行综述。