Computed tomography and magnetic resonance imaging studies of Latimeria chalumnae

Synopsis Recent radiologic imaging techniques (CT[Computed Tomography] and MRI[Magnetic Resonance Imaging]) were used to investigate the cranial anatomy of the coelacanth Latimeria chalumnae. The non-invasive CT and MRI techniques were performed successfully on a 1.45 m female specimen. This specimen had been frozen a year earlier for future research; the CT was conducted on the frozen animal, whereas the MRI method was performed immediately after thawing. The CT technique provides information about differential density of the organism (especially informative with respect to hard tissues, bone and cartilage), whereas three different types of MRI (proton resonance T₁, T₂ and flash) distinguish cartilage, muscles, and different connective tissues. A total of 381 CT cross sections (2 mm thick with 1 mm of overlap) through the head region were used in a computerized three-dimensional reconstruction program to address questions concerning cranial morphology. The results obtained from these radiologic imaging techniques confirmed most of the basic anatomy known from traditional dissections. However, the morphology of complex structures. such as the cartilaginous processes of the neurocranium, and the integration of the branchial arches and palate can only now be described more accurately.     

A new method in computer-assisted imaging in neuroanatomy

A procedure is described yielding computed images of postmortem brains with high topographic accuracy. Structures of the brain are traced and registered by means of a digitizer capable of measuring coordinates three-dimensionally. The information corresponding to one brain model is stored on a flexible disk with a capacity of 256 Kbytes. According to the output desired, the resulting brain images are either completely or partially displayed on the computer screen as stereo pairs. The brain models possess a local fidelity of about 1 mm. The images are useful in simultaneously studying superficial and central parts of the brain, spatial relationships of the various structures and the projection of deep structures onto the surface of the brain. A RAM of about 100 Kbytes is necessary for a program enabling the user to perform stereo projections, three-dimensional transformations and other image manipulations. The special features of anatomical computer imaging as compared to computed tomography (CT) and nuclear magnetic resonance imaging (NMR) are outlined. A combination of these different techniques seems to improve clinical diagnosis.     

Computer-aided stereographic representation of an object reconstructed from micrographs of serial thin sections

A method is described which allows a three-dimensional object to be reconstructed from micrographs of serial thin sections using computer graphic techniques. The reconstructed object, which can be rotated three- dimensionally, is displayed on a colour visual display unit and the surface of the object is shaded in order that it can be observed to provide an illusion of a three-dimensional structure. Moreover, the technique makes it possible to represent an inner structure when seen through an outer one, also to observe other sectioned face views. The method as described here allows rapid visual evaluation of the results of three-dimensional reconstruction from serial thin sections when recorded with the aid of a light or an electron microscope.     

Imaging lung perfusion

From the first measurements of the distribution of pulmonary blood flow using radioactive tracers by West and colleagues (J Clin Invest 40: 1-12, 1961) allowing gravitational differences in pulmonary blood flow to be described, the imaging of pulmonary blood flow has made considerable progress. The researcher employing modern imaging techniques now has the choice of several techniques, including magnetic resonance imaging (MRI), computerized tomography (CT), positron emission tomography (PET), and single photon emission computed tomography (SPECT). These techniques differ in several important ways: the resolution of the measurement, the type of contrast or tag used to image flow, and the amount of ionizing radiation associated with each measurement. In addition, the techniques vary in what is actually measured, whether it is capillary perfusion such as with PET and SPECT, or larger vessel information in addition to capillary perfusion such as with MRI and CT. Combined, these issues affect quantification and interpretation of data as well as the type of experiments possible using different techniques. The goal of this review is to give an overview of the techniques most commonly in use for physiological experiments along with the issues unique to each technique.     

Hominin brain evolution--new century, new directions

The study of hominin brain evolution focuses on the interiors of fossilized braincases. Applications of recent three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI) techniques for visualizing and measuring >virtual endocasts< from braincases in combination with advances in computer graphics and software for acquiring relevant data are transforming the way in which fossil skulls are analyzed, and improving the quality of paleoneurological investigations. Although CT imaging is preferred for fossil skulls, a novel method that combines high-resolution MRI of physical endocasts, electronic reconstruction of their missing parts, and warping of the resulting virtual endocasts is currently being developed and has great potential for future studies of hominin brain evolution. Applications of CT and MR techniques have already resulted in surprising new findings, which are briefly outlined. Exciting revelations about hominin brain evolution are expected as the 21st century unfolds.     

Advanced 3D-Sonographic Imaging as a Precise Technique to Evaluate Tumor Volume

Determination of tumor volume in subcutaneously inoculated xenograft models is a standard procedure for clinical and preclinical evaluation of tumor response to treatment. Practitioners frequently use a hands-on caliper method in conjunction with a simplified formula to assess tumor volume. Non-invasive and more precise techniques as investigation by MR or (μ)CT exist but come with various adverse effects in terms of radiation, complex setup or elevated cost of investigations. Therefore, we propose an advanced three-dimensional sonographic imaging technique to determine small tumor volumes in xenografts with high precision and minimized observer variability. We present a study on xenograft carcinoma tumors from which volumes and shapes were calculated with the standard caliper method as well as with a clinically available three-dimensional ultrasound scanner and subsequent processing software. Statistical analysis reveals the suitability of this non-invasive approach for the purpose of a quick and precise calculation of tumor volume in small rodents.     

A realistic utilization of nanotechnology in molecular imaging and targeted radiotherapy of solid tumors

Precise dose delivery to malignant tissue in radiotherapy is of paramount importance for treatment efficacy while minimizing morbidity of surrounding normal tissues. Current conventional imaging techniques, such as magnetic resonance imaging (MRI) and computerized tomography (CT), are used to define the three-dimensional shape and volume of the tumor for radiation therapy. In many cases, these radiographic imaging (RI) techniques are ambiguous or provide limited information with regard to tumor margins and histopathology. Molecular imaging (MI) modalities, such as positron emission tomography (PET) and single photon-emission computed-tomography (SPECT) that can characterize tumor tissue, are rapidly becoming routine in radiation therapy. However, their inherent low spatial resolution impedes tumor delineation for the purposes of radiation treatment planning. This review will focus on applications of nanotechnology to synergize imaging modalities in order to accurately highlight, as well as subsequently target, tumor cells. Furthermore, using such nano-agents for imaging, simultaneous coupling of novel therapeutics including radiosensitizers can be delivered specifically to the tumor to maximize tumor cell killing while sparing normal tissue.     

Retrograde perfusion and filling of mouse coronary vasculature as preparation for micro computed tomography imaging

Visualization of the vasculature is becoming increasingly important for understanding many different disease states. While several techniques exist for imaging vasculature, few are able to visualize the vascular network as a whole while extending to a resolution that includes the smaller vessels. Additionally, many vascular casting techniques destroy the surrounding tissue, preventing further analysis of the sample. One method which circumvents these issues is micro-Computed Tomography (μCT). μCT imaging can scan at resolutions <10 microns, is capable of producing 3D reconstructions of the vascular network, and leaves the tissue intact for subsequent analysis (e.g., histology and morphometry). However, imaging vessels by ex vivo μCT methods requires that the vessels be filled with a radiopaque compound. As such, the accurate representation of vasculature produced by μCT imaging is contingent upon reliable and complete filling of the vessels. In this protocol, we describe a technique for filling mouse coronary vessels in preparation for μCT imaging. Two predominate techniques exist for filling the coronary vasculature: in vivo via cannulation and retrograde perfusion of the aorta (or a branch off the aortic arch), or ex vivo via a Langendorff perfusion system. Here we describe an in vivo aortic cannulation method which has been specifically designed to ensure filling of all vessels. We use a low viscosity radiopaque compound called Microfil which can perfuse through the smallest vessels to fill all the capillaries, as well as both the arterial and venous sides of the vascular network. Vessels are perfused with buffer using a pressurized perfusion system, and then filled with Microfil. To ensure that Microfil fills the small higher resistance vessels, we ligate the large branches emanating from the aorta, which diverts the Microfil into the coronaries. Once filling is complete, to prevent the elastic nature of cardiac tissue from squeezing Microfil out of some vessels, we ligate accessible major vascular exit points immediately after filling. Therefore, our technique is optimized for complete filling and maximum retention of the filling agent, enabling visualization of the complete coronary vascular network--arteries, capillaries, and veins alike.     

Low-dose CT imaging of radio-opaque markers for assessing human rotator cuff repair: accuracy, repeatability and the effect of arm position

Previous studies have used radiostereometric analysis (RSA) to assess the integrity and mechanical properties of repaired tendons and ligament grafts. A conceptually similar approach is to use CT imaging to measure the 3D position and distance between implanted markers. The purpose of this study was to quantify the accuracy and repeatability of measuring the position and distance between metallic markers placed in the rotator cuff using low-dose CT imaging. We also investigated the effect of repeated or variable positions of the arm on position and distance measures. Six human patients had undergone rotator cuff repair and placement of tantalum beads in the rotator cuff at least one year prior to participating in this study. On a single day each patient underwent nine low-dose CT scans in seven unique arm positions. CT scans were analyzed to assess bias, precision and RMS error of the measurement technique. The effect of repeated or variable positions of the arm on the 3D position of the beads and the distance between these beads and suture anchors in the humeral head were also assessed. Results showed the CT imaging method is accurate and repeatable to within 0.7 mm. Further, measures of bead position and anchor-to-bead distance are influenced by arm position and location of the bead within the rotator cuff. Beads located in the posterior rotator cuff moved medially as much as 20 mm in abduction or external rotation. When clinically relevant CT arm positions such as the hand on umbilicus or at side were repeated, bead position varied less than 4 mm in any anatomic direction and anchor-to-bead distance varied +2.8 to -1.6 mm (RMS 1.3 mm). We conclude that a range of ± 3 mm is a conservative estimate of the uncertainty in anchor-to-bead distance for patients repeatedly scanned in clinically-relevant arm positions.     

Computed tomographies and cancer risk in children: a literature overview of CT practices,risk estimations and an epidemiologic cohort study proposal

Radiation protection is a topic of great public concern and of many scientific investigations, because ionizing radiation is an established risk factor for leukaemia and many solid tumours. Exposure of the public to ionizing radiation includes exposure to background radiation, as well as medical and occupational exposures. A large fraction of the exposure from diagnostic procedures comes from medical imaging. Computed tomography (CT) is the major single contributor of diagnostic radiation exposure. An increase in the use of CTs has been reported over the last decades in many countries. Children have smaller bodies and lower shielding capacities, factors that affect the individual organ doses due to medical imaging. Several risk models have been applied to estimate the cancer burden caused by ionizing radiation from CT. All models predict higher risks for cancer among children exposed to CT as compared to adults. However, the cancer risk associated with CT has not been assessed directly in epidemiological studies. Here, plans are described to conduct an historical cohort study to investigate the cancer incidence in paediatric patients exposed to CT before the age of 15 in Germany. Patients will be recruited from radiology departments of several hospitals. Their individual exposure will be recorded, and time-dependent cumulative organ doses will be calculated. Follow-up for cancer incidence via the German Childhood Cancer Registry will allow computation of standardized incidence ratios using population-based incidence rates for childhood cancer. Dose–response modelling and analyses for subgroups of children based on the indication for and the result of the CT will be performed.     

Live dynamic imaging of caveolae pumping targeted antibody rapidly and specifically across endothelium in the lung

How effectively and quickly endothelial caveolae can transcytose in vivo is unknown, yet critical for understanding their function and potential clinical utility. Here we use quantitative proteomics to identify aminopeptidase P (APP) concentrated in caveolae of lung endothelium. Electron microscopy confirms this and shows that APP antibody targets nanoparticles to caveolae. Dynamic intravital fluorescence microscopy reveals that targeted caveolae operate effectively as pumps, moving antibody within seconds from blood across endothelium into lung tissue, even against a concentration gradient. This active transcytosis requires normal caveolin-1 expression. Whole body gamma-scintigraphic imaging shows rapid, specific delivery into lung well beyond that achieved by standard vascular targeting. This caveolar trafficking in vivo may underscore a key physiological mechanism for selective transvascular exchange and may provide an enhanced delivery system for imaging agents, drugs, gene-therapy vectors and nanomedicines. 'In vivo proteomic imaging' as described here integrates organellar proteomics with multiple imaging techniques to identify an accessible target space that includes the transvascular pumping space of the caveola.     

运用CT三维重建测量重度先天性脊柱侧凸Cobb角的临床应用

目的:评价在CT三维重建上测量重度先天性脊柱侧凸Cobb角度的可重复性和可靠性。方法:收集在我院诊治的重度先天性脊柱侧凸病人的CT三维重建和脊柱全长X线片,共计67例。由五名不同测量者对CT三维重建脊柱畸形冠状面主弯Cobb角测量两次,两次间隔在三周以上,并测量脊柱全长X线片脊柱畸形冠状面主弯Cobb角一次,运用组内相关系数分析测量结果之间的可重复性和可靠性。结果:同一测量者两次测量结果之间的差值平均为4.5°。同一测量者两次测量结果之间的组内相关系数为0.969,不同测量者之间测量结果的组内相关系数为0.913。取五名测量者在CT三维重建上第一次测量的Cobb角度,其平均值为(110.5±23.5)°,五名测量者在X线片上测量结果的平均值为(103.1±22.0)°,对两组数据进行Mann-Whitney非参数检验差异有统计学意义(Z=-2.86,P=0.004)。结论:在CT三维重建上测量重度先天性脊柱侧凸的Cobb角,可以减小测量的误差,提高测量的可重复性和可靠性,是一种相对准确的测量方法。     

In vivo respiratory-gated micro-CT imaging in small-animal oncology models

Micro-computed tomography(micro-CT) is becoming an accepted research tool for the noninvasive examination of laboratory animals such as mice and rats, but to date, in vivo scanning has largely been limited to the evaluation of skeletal tissues. We use a commercially available micro-CT device to perform respiratory gated in vivo acquisitions suitable for thoracic imaging. The instrument is described, along with the scan protocol and animal preparation techniques. Preliminary results confirm that lung tumors as small as 1 mm in diameter are visible in vivo with these methods. Radiation dose was evaluated using several approaches, and was found to be approximately 0.15 Gy for this respiratory-gated micro-CT imaging protocol. The combination of high-resolution CT imaging and respiratory-gated acquisitions appears well-suited to serial in vivo scanning.     

Inside out: modern imaging techniques to reveal animal anatomy

Animal anatomy has traditionally relied on detailed dissections to produce anatomical illustrations, but modern imaging modalities, such as MRI and CT, now represent an enormous resource that allows for fast non-invasive visualizations of animal anatomy in living animals. These modalities also allow for creation of three-dimensional representations that can be of considerable value in the dissemination of anatomical studies. In this methodological review, we present our experiences using MRI, CT and μCT to create advanced representation of animal anatomy, including bones, inner organs and blood vessels in a variety of animals, including fish, amphibians, reptiles, mammals, and spiders. The images have a similar quality to most traditional anatomical drawings and are presented together with interactive movies of the anatomical structures, where the object can be viewed from different angles. Given that clinical scanners found in the majority of larger hospitals are fully suitable for these purposes, we encourage biologists to take advantage of these imaging techniques in creation of three-dimensional graphical representations of internal structures.     

Image-guided simulation of tissue deformation using a mechanical model on a surgical application

This paper presents a method for localizing the position of a liver and a tumor within the tissue during a minimally invasive liver operation. From pre-operative CT scans, the liver volume and its internal structures are segmented using image-processing techniques. Based on these segmentations, a three-dimensional mechanical model is built to compute the liver volume and internal structure displacement under boundary conditions such as external forces from the surgical instrument. This can help the surgeon understand the motion of internal structures when manipulating the liver. To validate our method, an experiment on a porcine liver explant was performed to assess the difference between actual tissue motion and the mechanical model.     

Functional morphology and homology in the odontocete nasal complex: Implications for sound generation

The site and physiologic mechanism(s) responsible for the generation of odontocete biosonar signals have eluded investigators for decades. To address these issues we subjected postmortem toothed whale heads to interrogation using medical imaging techniques. Most of the 40 specimens (from 19 species) were examined using X-ray computed tomography (CT) and/or magnetic resonance imaging (MR). Interpretation of scan images was aided by subsequent dissection of the specimens or, in one case, by cryosectioning. In all specimens we described a similar tissue complex and identified it as the hypothetical biosonar signal generator. This complex includes a small pair of fatty bursae embedded in a pair of connective tissue lips, a cartilaginous blade, a stout ligament, and an array of soft tissue air sacs. Comparing and contrasting the morphologic patterns of nasal structures across species representing every extant odontocete superfamily reveals probable homologous relationships, which suggests that all toothed whales may be making their biosonar signals by a similar mechanism. © 1996 Wiley-Liss, Inc.     

Development and validation of a computed tomography-based methodology to measure carpal kinematics

Motion of the wrist bones is complicated and difficult to measure. Noninvasive measurement of carpal kinematics using medical images has become popular This technique is difficult and most investigators employ custom software. The objective of this paper is to describe a validated methodology for measuring carpal kinematics from computed tomography (CT) scans using commercial software. Four cadaveric wrists were CT imaged in neutral, full flexion, and full extension. A registration block was attached to the distal radius and used to align the data sets from each position. From the CT data, triangulated surface models of the radius, lunate, and capitate bones were generated using commercial software. The surface models from each wrist position were read into engineering design software that was used to calculate the centroid (position) and principal mass moments of inertia (orientation) of (1) the capitate and lunate relative to the fixed radius and (2) the capitate relative to the lunate. These data were used to calculate the helical axis kinematics for the motions from neutral to extension and neutral to flexion. The kinematics were plotted in three dimensions using a data visualization software package. The accuracy of the method was quantified in a separate set of experiments in which an isolated capitate bone was subjected to two different known rotation/translation motions for ten trials each. For comparison to in vivo techniques, the error in distal radius surface matching was determined using the block technique as a gold standard. The motion that the lunate and capitate underwent was half that of the overall wrist flexion-extension range of motion. Individually, the capitate relative to the lunate and the lunate relative to the radius generally flexed or extended about 30 deg, while the entire wrist (capitate relative to radius) typically flexed or extended about 60 deg. Helical axis translations were small, ranging from 0.6 mm to 1.8 mm across all motions. The accuracy of the method was found to be within 1.4 mm and 0.5 deg (95% confidence intervals). The mean error in distal radius surface matching was 2.4 mm and 1.2 deg compared to the use of a registration block. Carpal kinematics measured using the described methodology were accurate, reproducible, and similar to findings of previous investigators. The use of commercially available software should broaden the access of researchers interested in measuring carpal kinematics using medical imaging.     

基于图像重建的CT三维重建提升腹部增强扫描图像质量的价值

摘要 目的：探讨基于图像重建的电子计算机断层扫描仪器(Computed Tomography,CT)三维成像提升腹部增强扫描图像质量的价值。方法：2019年11月到2020年10月选择在本院进行腹部CT增强扫描的患者76例作为研究对象,采用电脑随机数字法将研究对象分为对照组和重建组各38例,对照组给予常规扫描成像,重建组给予基于自适应统计迭代重建(adaptive statistical iterative reconstruction,ASIR)的CT三维成像,记录两组成像质量与噪声情况。结果：两名医师对重建组的图像主观质量评分都高于对照组(P<0.05)。重建组的图像相对细腻柔和,能清晰显示图像细小血管断面,末梢血管显示良好,血管壁光滑柔和。重建组的动脉期、门静脉期、平衡期的肝脏CT值高于对照组(P<0.05),动脉期、门静脉期、平衡期的肝脏、胰腺对比噪声比(contrast to noise ratio,CNR)值低于对照组(P<0.05)。重建组的容积剂量指数(volume CT dose index,CTDIvol)和剂量长度乘积(Dose-Length product,DLP)、有效剂量(effective dose,ED)值都低于对照组(P<0.05)。结论：基于图像重建的CT三维成像能提升腹部增强扫描主客观图像质量,降低图像噪声,更利于腹部疾病的显示,从而提高正确诊断率。     

A study to determine the impact of IMPT optimization techniques on prostate synthetic CT image sets dose comparison against CT image sets

BackgroundThe objective of this study is to determine the impact of intensity modulated proton therapty (IMPT) optimization techniques on the proton dose comparison of commercially available magnetic resonance for calculating attenuation (MRCA T) images, a synthetic computed tomography CT (sCT) based on magnetic resonance imaging (MRI) scan against the CT images and find out the optimization technique which creates plans with the least dose differences against the regular CT image sets.Material and methodsRegular CT data sets and sCT image sets were obtained for 10 prostate patients for the study. Six plans were created using six distinct IMPT optimization techniques including multi-field optimization (MFO), single field uniform dose (SFUD) optimization, and robust optimization (RO) in CT image sets. These plans were copied to MRCA T, sCT datasets and doses were computed. Doses from CT and MRCA T data sets were compared for each patient using 2D dose distribution display, dose volume histograms (DVH), homogeneity index (HI), conformation number (CN) and 3D gamma analysis. A two tailed t-test was conducted on HI and CN with 5% significance level with a null hypothesis for CT and sCT image sets.ResultsAnalysis of ten CT and sCT image sets with different IMPT optimization techniques shows that a few of the techniques show significant differences between plans for a few evaluation parameters. Isodose lines, DVH, HI, CN and t-test analysis shows that robust optimizations with 2% range error incorporated results in plans, when re-computed in sCT image sets results in the least dose differences against CT plans compared to other optimization techniques. The second best optimization technique with the least dose differences was robust optimization with 5% range error.ConclusionThis study affirmatively demonstrates the impact of IMPT optimization techniques on synthetic CT image sets dose comparison against CT images and determines the robust optimization with 2% range error as the optimization technique which gives the least dose difference when compared to CT plans.