^99mTc—NOEt心肌显像的最佳显像时间的研究

目的:研究~(99m)Tc-NOEt(NOEt:N—乙氧基—N—乙基氨荒酸钠)的最佳负荷显像时间及再分布显像时间,方法:32例CAD患者及8例正常对照者进行~(99m)Tc-NOEt动态心肌断层SPECT显像研究,分析心肌显像质量及心肌显像结果 结果:~(99m)Tc-NOEt心肌显像质量随时间的递增而明显改善,但再分布显像时间过长反而造成部分心肌显像质量下降;~(99m)Tc-NOEt再分布现象可能发生较早.结论:建议负荷心肌显像时间直在15分钟进行,再分布显像在2小时进行,最好不超过4小时.     

Interleaved snapshot echo planar imaging of mouse brain at 7.0 T

Single-shot echo planar imaging (EPI) of a mouse brain at high field is very challenging. Large susceptibility-induced gradients affect much of the brain volume, causing severe image deformations and signal loss. Segmented EPI and other conventional multi-shot approaches alleviate these problems but suffer from lower temporal resolution and motion artifacts. We demonstrate that interleaved snapshot EPI represents a simple and robust alternative approach and one that is particularly suitable for high-field T2*-weighted functional imaging of a mouse brain. Similarly to segmented multi-shot techniques, it significantly reduces the susceptibility-related artifacts. At the same time, it preserves the high temporal resolution and the snapshot capability of a conventional EPI by acquiring entire image within a single TR period. We discuss implementation details of the interleaved snapshot EPI sequence and the trade-offs involved between the imaging efficiency, the number of interleaved excitation-acquisition blocks and the artifact reduction. To document the sequence utility, murine brain in vivo imaging with the interleaved snapshot EPI method was compared with a conventional EPI. We found that at least five interleaved blocks were necessary to restore the signal in most cortical areas. We also show that a standard global shimming procedure provides sufficient homogeneity for multi-slice interleaved snapshot EPI acquisition. In contrast, the conventional EPI of comparable image quality would be limited to a single slice with highly optimized local shim. Finally, an in vitro comparison with turbo FLASH acquisition shows the interleaved snapshot EPI to have superior time resolution and signal-to-noise ratio.     

Polymers as Probes for Multimodal Imaging with MRI

Multimodal imaging agents provide unique opportunities to probe disease states in vivo. The development of polymeric molecular imaging agents that combine the high‐resolution capabilities of MRI with other more sensitive techniques leads to significant possibilities for increasing our understanding of biological processes in live animals. To fully utilise this capability, advanced architectural polymers are being developed in which the material properties of the multimodal imaging agent are underpinned by a strong understanding of the underlying synthetic and physical chemistry of the macromolecules. In this report, the development of new polymers as multimodal imaging agents utilising MRI for preclinical in vivo studies is described.     

一种新的磁共振扩散成像实验参数控制方法

扩散敏感梯度磁度的方向及强度是磁共振扩散成像实验的重要参数，但这二个参数不能由用户通过设备自带的软件设定。本文介绍一种新的方法，通过修改MRI扫描机内部的数据文件，用户可以方便与精确地设定扩散加权成像DWI及扩散张景成像DTI的实验参数，而且可以为MRI扫描机增加新的功能。     

星形细胞肿瘤磁敏感成像与动态对比剂MR灌注加权成像的相关性研究

目的：探讨星形细胞肿瘤磁敏感加权成像（ SWI)半量化与动态对比剂增强MR灌注加权成像（ PI)的相关性。方法回顾性分析98例经手术病理证实星形细胞肿瘤患者的术前SWI及PI检查资料。测量SWI中肿瘤内磁敏感低信号区（ ITSHIA)半量化数据,以及PI中肿瘤内实性部分最大相对脑血流量值（ rrCBV瘤内max )和瘤周区最大相对CBV值（ rrCBV瘤周max )。应用Kruskal-Wallis H检验比较不同病理分级星形细胞肿瘤间rrCBV瘤内max与rrCBV瘤周max的差异,比较不同级别肿瘤间灌注热点区与ITSHIA形态的对应情况;应用Spearman相关性检验比较不同级别肿瘤间SWI中各半量化指标与PI中rrCBV瘤内max与rrCBV瘤周max的相关性。结果星形细胞肿瘤rrCBV瘤内max值（ rs =0．662,P<0．01)及rrCBV瘤周max值（rs =0．794,P<0．01)与其分级显著相关。毛细胞型星形细胞瘤rrCBV瘤内max高于Ⅱ级星形细胞瘤,与Ⅲ级肿瘤类似;而 rrCBV瘤周max与Ⅱ级星形细胞瘤差异无统计学意义（ P >0．05),却低于高级别肿瘤。星形细胞肿瘤的ITSHIA半量化指标与rrCBV瘤内max与rrCBV瘤周max值呈显著线性正相关。星形细胞肿瘤内灌注热点区与ITSHIA不完全对应。结论星形细胞肿瘤SWI指标与PI指标密切相关,二者对于术前评估星形细胞肿瘤的病理分级同样具有较高价值。灌注热点区与ITSHIA并不完全相同,可能与二者显示肿瘤内血管生成的机制不同有关。     

Shades of gray matter: Noninvasive optical images of human brain reponses during visual stimulation

Recent theories about human brain function emphasize the need for imaging methods that allow the study of dynamic interactions among different structures. In this paper, we report on a new technique, based on the measurement of parameters of migration of near-infrared photons, that yields functional images of the human occipital cortex, combining a spatial resolution of 0.5 cm and a temporal resolution of 50 ms. This technique appears to be suitable for studying the dynamics of cortical activation.     

A facile synthesis of versatile Cu2−xS nanoprobe for enhanced MRI and infrared thermal/photoacoustic multimodal imaging

A novel type of intelligent nanoprobe by using single component of Cu_2−xS for multimodal imaging has been facilely and rapidly synthesized in scale via thermal decomposition followed by biomimetic phospholipid modification, which endows them with uniform and small nanoparticle size (ca.15 nm), well phosphate buffer saline (PBS) dispersity, high stability, and excellent biocompatibility. The as-synthesized Cu_2−xS nanoprobes (Cu_2−xS NPs) are capable of providing contrast enhancement for T1-weighted magnetic resonance imaging (MRI), as demonstrated by the both in vitro and in vivo imaging investigations for the first time. In addition, due to their strong near infrared (NIR) optical absorption, they can also serve as a candidate contrast agent for enhanced infrared thermal/photoacoustic imaging, to meet the shortfalls of MRI. Hence, complementary and potentially more comprehensive information can be acquired for the early detection and accurate diagnosis of cancer. Furthermore, negligible systematic side effects to the blood and tissue were observed in a relatively long period of 3 months. The distinctive multimodal imaging capability with excellent hemo/histocompatibility of the Cu_2−xS NPs could open up a new molecular imaging possibility for detecting and diagnosing cancer or other diseases in the future.     

核磁共振弥散峰度成像在脑中风诊断中的应用

目的 研究弥散峰度成像(DKI)对脑组织灰质和白质的描述以及在脑中风诊断中的应用.方法 采用2例正常人以及15例脑中风患者(包含9例脑梗死,急性、亚急性和陈旧性各占3例)的脑部核磁共振图像作为试验数据.针对每例数据各个像素位置,分别对9个不同弥散梯度场下各个信号强度进行非线性拟合得到弥散系数(D值)和弥散峰度(K值),进而做出ADC图和DKI图.观察比较分析各例在ADC图和DKI图的表现.结果 DKI成像具有更多的纹理细节,包含更丰富的组织特征.急性、亚急性脑梗死病灶在DKI图呈现高信号,陈旧性脑梗死病灶在DKI图呈现低信号,平均峰度相对值(rMK)分别为2.193±0.166,1.789±0.162,0.564±0.069.结论 DKI对脑组织尤其是灰质以及一些脑中风病灶的描述相对于ADC图包含更多的组织信息.脑梗死病灶的rMK值具有特征性演变规律.     

Seeing right through you: applications of optical imaging to the study of the human brain

A new set of techniques allows for the study of brain function by near-infrared light, exploiting two optical phenomena: Changes in light absorption are determined by changes in the concentration of substances like oxy- and deoxyhemoglobin, and changes in light scattering occur as a consequence of variations of properties of membranes and corpuscles in the neural tissue. Methods based on light absorption can be used to study hemodynamic changes in the brain, whereas those based on light scattering can be used to study neuronal activity and to provide anatomical information at a cellular and subcellular level. Three optical imaging approaches can be used to study living tissue: reflection, optical coherence tomography (OCT), and photon migration. These three approaches vary in their penetration (from less than a millimeter for reflection to up to 3-5 cm for photon migration) and spatial resolution (from a micron level for reflection and OCT to a millimeter and centimeter level for photon migration). This issue includes a collection of articles reviewing applications of these technologies to the study of brain and other bodily functions in humans.     

Prostate cancer: added value of subtraction dynamic imaging in 3T magnetic resonance imaging with a phased-array body coil

Purpose

To determine the added value of dynamic subtraction magnetic resonance (MR) imaging for the localization of prostate cancer.

Materials and Methods

We examined 21 consecutive patients who underwent MR imaging in 3T unit with a phased-array body coil and then had radical prostatectomy. After T2-weighted fast spin-echo imaging, we performed a contrast-enhanced dynamic 3D gradient-echo imaging consisting of pre-contrast, 2 successive early-phased (first imaging was started just after the appearance of contrast material in the aortic bifurcation followed by second imaging 35 seconds after the initiation of first imaging) and one 5-minute delayed post-contrast series. Subtraction of pre-contrast images from corresponding post-contrast images of each phase was performed on the console.

Results

On ROC analysis, the overall accuracy (A_z value) of dynamic imaging combined with subtraction imaging was higher than T2-weighted imaging (p = 0.001) or conventional dynamic imaging alone (p = 0.074) for localization of cancer foci regardless of their zonal locations. Among pathologically verified 81 lesions, the mean volume of detected lesions with the subtraction images (n = 49, 0.69 cm³) was smaller than with T2-weighted images (n = 14, 1.05 cm³) or conventional dynamic images (n = 43, 0.71 cm³).

Conclusion

For localization of small prostate cancer, additional subtraction for the dynamic imaging could be superior to both T2-weighted imaging and un-subtracted dynamic imaging.     

BaHoF5 nanoprobes as high-performance contrast agents for multi-modal CT imaging of ischemic stroke

CT angiography (CTA) and CT perfusion (CTP) imaging can play important roles in the workup of acute ischemic stroke. However, these techniques are hindered by the large amounts of contrast agents (CAs) required, high doses of X-ray radiation exposure, and nephrotoxicity of the clinical used iodinated CAs. To address these problems, we synthesized and validated a novel class of CT CAs, PEGylated BaHoF₅ nanoparticles (NPs), for CTA and CTP imaging, which can greatly enhance the diagnostic sensitivity and accuracy of ischemic stroke. These agents have unique advantages over conventional iodinated CT agents, including much lower dosage required, major metabolism through liver and better imaging efficiency at different voltages. Once translated, these PEGylated BaHoF₅ NPs can replace iodine-based CAs for diagnostic contrast-enhanced imaging of patients with kidney/heart diseases and improve the overall diagnostic index with negligible side effects.     

The value of diffusion-weighted and dynamic contrast-enhanced imaging in the diagnosis of thymic epithelial tumors

Background: Thymic epithelial tumors (TETs) are clinically the most frequently encountered neoplasm of the prevascular mediastinum in adults. The role of chest magnetic resonance (MR) imaging has been increasingly stressed thanks to its excellent contrast resolution, freedom from ionizing radiation, and capability to provide additional information regarding tumors'' cellular structure and vascularity.Methods: This study aimed to establish the relationship between the MR findings and pathological classification of TETs, focusing on diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) imaging. This retrospective cross-sectional study included 44 TET patients who underwent chest MR scanning. The tumors were classified into three groups according to the WHO classification: low-risk thymoma (LRT), high-risk thymoma (HRT), and non-thymoma (NT). Along with morphological characteristics, the apparent diffusion coefficient (ADC) value, time-intensity curve (TIC) pattern, and time to peak enhancement (TTP) of the tumors were recorded and compared between the three groups.Results: A smooth contour and complete or almost complete capsule were suggestive of LRTs. The median ADC value of the 44 tumors was 0.95 × 10^-3 mm²/sec. Among the three groups, LRTs had the highest ADC values, while NTs had the lowest. The differences between the ADC values of the three groups were statistically significant (p = 0.006). Using an ADC cutoff of 0.82 × 10^-3 mm²/sec to differentiate between LRTs and tumors of the two remaining groups, the area under the curve was 0.775, sensitivity was 100%, specificity was 50%, and accuracy was 65.91%. The washout (type 3) TIC pattern was the most prevalent, accounting for 45.45% of the population; this pattern was also predominantly observed in LRTs (71.43%). Although the median TTP of LRTs was lower than that of HRTs or NTs, no statistically significant differences were found between the TTPs of the three groups (p = 0.170).Conclusions: MR is a good imaging modality to preoperatively assess TETs. Morphological features, ADC value, TIC pattern, and TTP are helpful in preoperatively predicting TET pathology.     

肿瘤新生血管检测的研究进展

肿瘤新生血管是肿瘤营养物质以及代谢产物与机体交换的通路,肿瘤新生血管的生长对肿瘤的生长、恶化、转移、分期等有着重要的影响.以肿瘤血管的概念及其检测为出发点,介绍了肿瘤新生血管的形成、特点和检测意义;着重从肿瘤微血管密度、超声成像、光学成像及核磁共振成像等4个方面综述了肿瘤新生血管检测的研究进展.     

医学影像物理学（医学影像成像理论）教学与实验改革的探讨

目的：根据影像技术的发展，改革医学影像物理学教学和实验内容。简化X线物理及核物理等内容，扩充新成像技术，并与相关课程联合互补，以使课程内容适应新技术和新的教学要求。方法：根据我校实际课程体系，结合学生就业方向。从教学内容、课程设置、实验等三方面进行教学内容改革，调整教学内容；更新实验项目：并同医学图像处理相结合，交换和整合相关联的课程内容。最终制定出合理完善的理论与实验教学架构，并在实际教学过程中实践验证。结果：获得较为适合学科发展和教学实际的教学计划，并在教学实践中获得良好效果。结论：医学影像物理学教学与实验大纲应根据学科发展及时调整，适应新的技术需求和方向。细化医学影像物理学内容，强调医学图像处理技术，更新医学物理学实验，并与知识关联性强的课程进行统一整合和建设，以适应技术发展和教育要求。     

Application of functional peptides for biomedical diagnosis北大核心

BACKGROUND: As a class of biomaterials with excellent biocompatibility and biodegradability, functional peptides are becoming a research hotspot in the field of biomedicine. OBJECTIVE: To review the current development and future prospects of functional peptides in the field of biomedical diagnosis. METHODS: Search words were “peptides, self-assembly force, medicine imaging, biomaterials, medical diagnosis” in English and Chinese. Computer was used to retrieve relevant articles on self-assembled peptide medical diagnosis in VIP, Wanfang, CNKI, Web of Science, and PubMed databases from 2000 to 2020, and systematic induction, summary and analysis were conducted. RESULTS AND CONCLUSION: (1) The bonding forces for constructing self-assembled structures include van der Waals forces, hydrophobic interactions, electrostatic interactions, as well as the biological recognition of peptides. (2) The application of functional peptides in the field of biomedical diagnosis includes optical imaging, photoacoustic imaging, magnetic resonance imaging, computer tomography, and radionuclide imaging. (3) Functional peptides specifically target tumor sites in vivo for tumor imaging and treatment, with good targeting, high specificity, and strong binding affinity to receptors. (4) The functional peptides can be activated in situ by temperature and light to activate aggregation, complete multifunctional diagnosis of specific parts, good imaging effect, no toxic side effects, and fast metabolism in the body. (5) Functional peptides are labeled to enhance the detection signal in the body, monitor small changes, and perform disease diagnosis and preventive treatment. (6) It can be found that functional peptides have very broad application prospects in biomedical diagnosis, such as tumor detection and treatment, imaging of specific parts, and enhancement of detection signals. © 2023, Chinese Journal of Tissue Engineering Research. All rights reserved.     

Radiography of soft tissue of the foot and ankle with diffraction enhanced imaging

Non-calcified tissues, including tendons, ligaments, adipose tissue and cartilage, are not visible, for any practical purposes, with conventional X-ray imaging. Therefore, any pathological changes in these tissues generally necessitate detection through magnetic resonance imaging or ultrasound technology. Until recently the development of an X-ray imaging technique that could detect both bone and soft tissues seemed unrealistic. However, the introduction of diffraction enhanced X-ray imaging (DEI) which is capable of rendering images with absorption, refraction and scatter rejection qualities has allowed detection of specific soft tissues based on small differences in tissue densities. Here we show for the first time that DEI allows high contrast imaging of soft tissues, including ligaments, tendons and adipose tissue, of the human foot and ankle.     

Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs

The single photon emission microscope (SPEM) is an instrument developed to obtain high spatial resolution single photon emission computed tomography (SPECT) images of small structures inside the mouse brain. SPEM consists of two independent imaging devices, which combine a multipinhole collimator, a high-resolution, thallium-doped cesium iodide [CsI(Tl)] columnar scintillator, a demagnifying/intensifier tube, and an electron-multiplying charge-coupling device (CCD). Collimators have 300- and 450-µm diameter pinholes on tungsten slabs, in hexagonal arrays of 19 and 7 holes. Projection data are acquired in a photon-counting strategy, where CCD frames are stored at 50 frames per second, with a radius of rotation of 35 mm and magnification factor of one. The image reconstruction software tool is based on the maximum likelihood algorithm. Our aim was to evaluate the spatial resolution and sensitivity attainable with the seven-pinhole imaging device, together with the linearity for quantification on the tomographic images, and to test the instrument in obtaining tomographic images of different mouse organs. A spatial resolution better than 500 µm and a sensitivity of 21.6 counts·s^-1·MBq^-1 were reached, as well as a correlation coefficient between activity and intensity better than 0.99, when imaging ^99mTc sources. Images of the thyroid, heart, lungs, and bones of mice were registered using ^99mTc-labeled radiopharmaceuticals in times appropriate for routine preclinical experimentation of <1 h per projection data set. Detailed experimental protocols and images of the aforementioned organs are shown. We plan to extend the instrument''s field of view to fix larger animals and to combine data from both detectors to reduce the acquisition time or applied activity.     

Assessment of factors affecting the detectability of thermal radiations from the neural system of the brain

The paper describes a technique by which it may be possible to locate and analyse neural activity within the brain by a non-invasive and non-contact method with (in principle) an unlimited bandwidth. The method detects the rapid temperature fluctuations which are believed to accompany individual action potentials and other neural phenomena, and which should be detectable as a noise-like fluctuation of thermal infra-red radiation, with components up to several hundred Hz. It differs from conventional surface thermography in that it ignores changes of mean temperature in blood vessels etc. and transfer of heat to the skull surface by conduction or blood flow. Energy is assumed to travel only as infra-red radiation directly from the neural material to the detector, and as such the signal is very heavily attenuated by the water content of the skull and other intervening material. Available data suggest that the viability of the method is considerably reduced by this factor. None the less, the scarcity of reliable data on the temperature fluctuations themselves and the immense advantages of the technique, should it be successfully developed, suggest that it warrants detailed theoretical and experimental study.