Computer-based anthropometrical system for total body irradiation

For total body irradiation (TBI) dose calculation requirements, anatomical information about the whole body is needed. Despite the fact that video image grabbing techniques are used by some treatment planning systems for standard radiotherapy, there are no such systems designed to generate anatomical parameters for TBI planning. The paper describes an anthropometrical computerised system based on video image grabbing which was purpose-built to provide anatomical data for a PC-based TBI planning system. Using software, the system controls the acquisition and digitalisation of the images (external images of the patient in treatment position) and the measurement procedure itself (on the external images or the digital CT information). An ASCII file, readable by the TBI planning system, is generated to store the required parameters of the dose calculation points, i.e. depth, backscatter tissue thickness, thickness of inhomogeneity, off-axis distance (OAD) and source to skin distance (SSD).     

Automated image analysis of digital colposcopy for the detection of cervical neoplasia

Digital colposcopy is a promising technology for the detection of cervical intraepithelial neoplasia. Automated analysis of colposcopic images could provide an inexpensive alternative to existing screening tools. Our goal is to develop a diagnostic tool that can automatically identify neoplastic tissue from digital images. A multispectral digital colposcope (MDC) is used to acquire reflectance images of the cervix with white light before and after acetic-acid application in 29 patients. A diagnostic image analysis tool is developed to identify neoplasia in the digital images. The digital image analysis is performed in two steps. First, similar optical patterns are clustered together. Second, classification algorithms are used to determine the probability that these regions contain neoplastic tissue. The classification results of each patient's images are assessed relative to the gold standard of histopathology. Acetic acid induces changes in the intensity of reflected light as well as the ratio of green to red reflected light. These changes are used to differentiate high-grade squamous intraepithelial (HGSIL) and cancerous lesions from normal or low-grade squamous intraepithelial (LGSIL) tissue. We report diagnostic performance with a sensitivity of 79% and a specificity of 88%. We show that diagnostically useful digital images of the cervix can be obtained using a simple and inexpensive device, and that automated image analysis algorithms show a potential to identify histologically neoplastic tissue areas.     

基于视频图像边缘检测的人体下肢运动步态

背景：步态规律主要应用人体行走的运动学、动力学等参数进行描述。目前在运动医学、康复工程和仿生学等领域,步态分析可为确定疾病诊断、康复和治疗方案提供重要依据。 目的：应用基于人体运动图像的测量装置系统,采集人体在跑步机上行走的下肢运动步态视频,分析人体步态运动规律。 方法：采用基于双摄影机的人体运动图像捕捉系统,在人体的左右髋关节、膝关节、踝关节及脚板设置标识点,对人体在跑步机上行走的下肢运动步态视频进行采集。应用图像边缘检测的原理,对测量数据进行了图像处理和分析,得到人体正常步速行走时,左右大腿与竖直方向夹角、小腿与竖直方向夹角、脚板与竖直方向夹角及膝关节、踝关节标识点的关节角度变化规律。 结果与结论：基于视频图像边缘检测人体下肢的运动步态,成本相对低廉,数据误差较小,精度与进口设备较接近。应用该测量结果初步构建了人体步态行走数据库,为建立步态评定标准、异常步态判别以及进一步的康复治疗提供了依据。     

How to improve microscopic images obtained with consumer-type digital cameras

AIM: Digital imaging is useful in conventional photography because it immediately provides images, and the image quality can be improved afterwards by the use of computer programs. The major disadvantages of consumer-type digital cameras mounted on microscopes are (i) unequal illumination through the image, and (ii) a coloured background. A computer program was specifically adapted and refined to improve images obtained with consumer-type digital cameras mounted on microscopes. METHODS AND RESULTS: An approach using a division operation between the specimen image and a background image leads to homogeneous illumination throughout the image, with automatically corrected brightness and white background. The correct colour spectrum is preserved by correction of the histogram. This approach was obtained from the freeware computer program 'Image Arithmetic'. In a test, three different consumer-type digital cameras (Sony, Nikon, Olympus) on different microscopes were used to obtain images of different types of histological specimens (cervical smear, bone marrow biopsy, and colonic biopsy). The computer program dramatically improved the quality of images obtained with all tested cameras. CONCLUSION: Using this approach, even low-cost digital cameras mounted on microscopes produce brilliant images with homogeneous illumination and a white background, the image quality being comparable with expensive cameras especially designed for microscopes.     

Methods in laboratory investigation. Digital reversal and enhancement of negatives in video-based interactive morphometry

We describe a system for the digital reversal of negatives in interactive morphometry. Minimum requirements, in addition to a high-resolution black and white video camera and monitor, are a readily available digital video frame store and a computer system as simple as a microprocessor-based personal computer. In a video-based analysis system, the addition of a digital image memory device and computer obviates the time and expense of photographic processing of the large number of negatives to positive prints required for an appropriate sampling size in morphometry. Additionally, the enhancement of digital images to recover details in the negative is feasible. This study represents a part of a continuing effort to develop an efficient, interactive morphometry system that encourages the use of a large number of random samples by simplifying processing.     

数字化全牙列下颌骨三维解剖建模

目的探讨建立具有高质量牙列的下颌骨三维数字化解剖模型。方法用激光扫描获取1套标准下颌牙列解剖标本的精确三维模型,用CT扫描数据重建下颌骨三维模型,使用基于几何和图像解剖标志的配准变形方法将每颗牙齿模型对齐融合到下颌骨模型,进一步生成牙齿的牙釉质、牙本质、牙周膜。结果成功建立了具有高质量牙列的下颌骨三维数字化解剖模型,每颗牙齿具有牙冠细节和完整的牙根,区分牙釉质、牙本质、牙周膜,可以对任意解剖区域放大和旋转观察,显示解剖标志。结论高质量牙列的下颌骨三维数字化解剖模型具有逼真的三维显象和方便的教学学习功能,可用于口腔、颌面、解剖等多个学科。     

Wavelet-based resolution recovery using an anatomical prior provides quantitative recovery for human population phantom PET [¹¹C]raclopride data

The objective of this study was to evaluate a resolution recovery (RR) method using a variety of simulated human brain [11C]raclopride positron emission tomography (PET) images. Simulated datasets of 15 numerical human phantoms were processed by a wavelet-based RR method using an anatomical prior. The anatomical prior was in the form of a hybrid segmented atlas, which combined an atlas for anatomical labelling and a PET image for functional labelling of each anatomical structure. We applied RR to both 60 min static and dynamic PET images. Recovery was quantified in 84 regions, comparing the typical 'true' value for the simulation, as obtained in normal subjects, simulated and RR PET images. The radioactivity concentration in the white matter, striatum and other cortical regions was successfully recovered for the 60 min static image of all 15 human phantoms; the dependence of the solution on accurate anatomical information was demonstrated by the difficulty of the technique to retrieve the subthalamic nuclei due to mismatch between the two atlases used for data simulation and recovery. Structural and functional synergy for resolution recovery (SFS-RR) improved quantification in the caudate and putamen, the main regions of interest, from?-30.1% and?-26.2% to?-17.6% and?-15.1%, respectively, for the 60 min static image and from?-51.4% and?-38.3% to?-27.6% and?-20.3% for the binding potential (BP(ND)) image, respectively. The proposed methodology proved effective in the RR of small structures from brain [11C]raclopride PET images. The improvement is consistent across the anatomical variability of a simulated population as long as accurate anatomical segmentations are provided.     

Digital chest imaging using a 57-cm image intensifier: A receiver-operating characteristic study of user performance

Chest radiography provides one of the great challenges to digital diagnostic imaging because of (1) the relatively large size of the chest field, (2) the contrast range required to resolve subtle pathological changes in soft tissue density, and (3) the high degree of spatial resolution required to discriminate pathological detail. The field size problem was resolved by using a 57-cm image intensifier whose video output of the chest could be digitized. The issue of contrast resolution was addressed in a recently completed receiver-operating characteristic study of the detectability of low-contrast densities in a humanoid chest phantom. The latter indicated that, despite the smaller size of the digital image, they were adequate for resolving clinically significant soft-tissue densities. The question of spatial resolution in digital diagnostic images is addressed in the study presented. A set of 41 clinical cases were selected to provide the typical range of diagnostic type experienced in routine diagnostic radiology. The images were each presented as conventional film, digital laser-printer, and digital video images. The results of an ROC analysis of five readers' performance in each of the viewing modes is presented.     

Automatic endotracheal tube position confirmation system based on image classification--a preliminary assessment

Endotracheal intubation is a complex medical procedure in which a ventilating tube is inserted into the human trachea. Improper positioning carries potentially fatal consequences and therefore confirmation of correct positioning is mandatory. This paper introduces a novel system for endotracheal tube position confirmation. The proposed system comprises a miniature complementary metal oxide silicon sensor (CMOS) attached to the tip of a semi rigid stylet and connected to a digital signal processor (DSP) with an integrated video acquisition component. Video signals are acquired and processed by a confirmation algorithm implemented on the processor. The confirmation approach is based on video image classification, i.e., identifying desired expected anatomical structures (upper trachea and main bifurcation of the trachea) and undesired structures (esophagus). The desired and undesired images are indicators of correct or incorrect endotracheal tube positioning. The proposed methodology is comprised of a continuous and probabilistic image representation scheme using Gaussian mixture models (GMMs), estimated using a greedy algorithm. A multi-dimensional feature space, which consists of several textural-based features, is utilized to represent the images. The performance of the proposed algorithm was evaluated using two datasets: a dataset of 1600 images extracted from 10 videos recorded during intubations on dead cows, and a dataset of 358 images extracted from 8 videos recorded during intubations performed on human subjects. Each one of the video images was classified by a medical expert into one of three categories: upper tracheal intubation, correct (carina) intubation and esophageal intubation. The results, obtained using a leave-one-case-out method, show that the system correctly classified 1530 out of 1600 (95.6%) of the cow intubations images, and 351 out of the 358 human images (98.0%). Misclassification of an image of the esophagus as carina or upper-trachea, which is potentially fatal, was extremely rare (only one case when in the animal dataset and no cases when in the human intubation dataset). The classification results of the cow intubations dataset compare favorably with a state-of-the-art classification method tested on the same dataset.     

Multispectral optical imaging device for in vivo detection of oral neoplasia

A multispectral digital microscope (MDM) is designed and constructed as a tool to improve detection of oral neoplasia. The MDM acquires in vivo images of oral tissue in fluorescence, narrow-band (NB) reflectance, and orthogonal polarized reflectance (OPR) modes, to enable evaluation of lesions that may not exhibit high contrast under standard white light illumination. The device rapidly captures image sequences so that the diagnostic value of each modality can be qualitatively and quantitatively evaluated alone and in combination. As part of a pilot clinical trial, images are acquired from normal volunteers and patients with precancerous and cancerous lesions. In normal subjects, the visibility of vasculature can be enhanced by tuning the reflectance illumination wavelength and polarization. In patients with histologically confirmed neoplasia, we observe decreased blue/green autofluorescence and increased red autofluorescence in lesions, and increased visibility of vasculature using NB and OPR imaging. The perceived lesion borders change with imaging modality, suggesting that multimodal imaging has the potential to provide additional diagnostic information not available using standard white light illumination or by using a single imaging mode alone.     

Slippage of a spinous process hook during flexion in a flexible fixation system for the lumbar spine.

This study was undertaken to measure the amount of slippage of a spinous process hook (that forms part of a flexible fixation system) during flexion. Human cadaveric lumbar spines (10) were fitted with the device. A rig was designed to apply flexural displacements to a spine using a materials testing machine. Spherical markers were attached to the spine and hook. As a spine was flexed a digital video camera was used to record the positions of the markers. The movements of the markers were measured using interactive computer software to assess any slippage of the spinous process hook. During flexion the overall mean hook slippage was measured to be 0.10mm (standard deviation 0.04mm). The mean hook slippage, for each of the 10 specimens, was in the range of 0.05-0.14mm. The results imply that slippage of a spinous process hook during flexion is small.     

Three-dimensional volume rendering of the ankle based on magnetic resonance images enables the generation of images comparable to real anatomy

We have applied high-quality medical imaging techniques to study the structure of the human ankle. Direct volume rendering, using specific algorithms, transforms conventional two-dimensional (2D) magnetic resonance image (MRI) series into 3D volume datasets. This tool allows high-definition visualization of single or multiple structures for diagnostic, research, and teaching purposes. No other image reformatting technique so accurately highlights each anatomic relationship and preserves soft tissue definition. Here, we used this method to study the structure of the human ankle to analyze tendon–bone–muscle relationships. We compared ankle MRI and computerized tomography (CT) images from 17 healthy volunteers, aged 18–30 years (mean 23 years). An additional subject had a partial rupture of the Achilles tendon. The MRI images demonstrated superiority in overall quality of detail compared to the CT images. The MRI series accurately rendered soft tissue and bone in simultaneous image acquisition, whereas CT required several window-reformatting algorithms, with loss of image data quality. We obtained high-quality digital images of the human ankle that were sufficiently accurate for surgical and clinical intervention planning, as well as for teaching human anatomy. Our approach demonstrates that complex anatomical structures such as the ankle, which is rich in articular facets and ligaments, can be easily studied non-invasively using MRI data.     

Multiple template-based fluoroscopic tracking of lung tumor mass without implanted fiducial markers

Precise lung tumor localization in real time is particularly important for some motion management techniques, such as respiratory gating or beam tracking with a dynamic multi-leaf collimator, due to the reduced clinical tumor volume (CTV) to planning target volume (PTV) margin and/or the escalated dose. There might be large uncertainties in deriving tumor position from external respiratory surrogates. While tracking implanted fiducial markers has sufficient accuracy, this procedure may not be widely accepted due to the risk of pneumothorax. Previously, we have developed a technique to generate gating signals from fluoroscopic images without implanted fiducial markers using a template matching method (Berbeco et al 2005 Phys. Med. Biol. 50 4481-90, Cui et al 2007 Phys. Med. Biol. 52 741-55). In this paper, we present an extension of this method to multiple-template matching for directly tracking the lung tumor mass in fluoroscopy video. The basic idea is as follows: (i) during the patient setup session, a pair of orthogonal fluoroscopic image sequences are taken and processed off-line to generate a set of reference templates that correspond to different breathing phases and tumor positions; (ii) during treatment delivery, fluoroscopic images are continuously acquired and processed; (iii) the similarity between each reference template and the processed incoming image is calculated; (iv) the tumor position in the incoming image is then estimated by combining the tumor centroid coordinates in reference templates with proper weights based on the measured similarities. With different handling of image processing and similarity calculation, two such multiple-template tracking techniques have been developed: one based on motion-enhanced templates and Pearson's correlation score while the other based on eigen templates and mean-squared error. The developed techniques have been tested on six sequences of fluoroscopic images from six lung cancer patients against the reference tumor positions manually determined by a radiation oncologist. The tumor centroid coordinates automatically detected using both methods agree well with the manually marked reference locations. The eigenspace tracking method performs slightly better than the motion-enhanced method, with average localization errors less than 2 pixels (1 mm) and the error at a 95% confidence level of about 2-4 pixels (1-2 mm). This work demonstrates the feasibility of direct tracking of a lung tumor mass in fluoroscopic images without implanted fiducial markers using multiple reference templates.     

Automatic detection of fiducial markers in fluoroscopy images for on-line calibration

Calibrated C-arm fluoroscopy is used for a variety of medical procedures where objects and anatomical structures need to be located in space. Calibration is often based on imaging a grid of fiducial markers and using the C-arm image's geometrical measurements (radius and center) together with the positions of the markers. An on-line technique is developed to automatically locate the fiducial markers and validated on 97 images. The success rate of the detection algorithm is 96.28% with an average error of 0.46 mm and a standard deviation of 0.32 mm.     

JPEG2000 for automated quantification of immunohistochemically stained cell nuclei: a comparative study with standard JPEG format

The Joint Photographic Experts Group (JPEG) standard format is one of the most widely used in image compression technologies. More recently, JPEG2000 format has emerged as a state-of-the-art technology that provides substantial improvements in picture quality at higher compression ratios. However, there has been no attempt to date to determine which of the two compression formats produces less variability in the automated evaluation of immunohistochemically stained digital images in agreement with their compression rates and complexity degrees. The evaluation of Ki67 and FOXP3 immunohistochemical nuclear markers was performed in a total of 329 digital images: 47 were captured in uncompressed Tagged Image File Format (TIFF), 141 were converted to three JPEG compressed formats (47 each with 1:3, 1:23 and 1:46 compression) and 141 were converted to three JPEG2000 compressed formats (47 each with 1:3, 1:23 and 1:46 compression). The count differences between images in TIFF versus JPEG formats were compared with those obtained between images in TIFF versus JPEG2000 formats at the three levels of compression. It was found that, using JPEG2000 compression, the results of the stained nuclei count are close enough to the results obtained with uncompressed images, especially in highly complex images at minimum and medium compression. Otherwise, in images of low complexity, JPEG and JPEG2000 had similar count efficiency to that of the original TIFF images at all compression levels. These data suggest that JPEG2000 could give rise to an efficient means of storage, reducing file size and storage capacity, without compromise on the immunohistochemical analytical quality.     

三种X线管电压下的胸部DDR影像质量评价

目的 探讨胸部DDR系统在不同管电压下成像与影像质量的关系。方法 使用E－com DR2000摄影系统对33例受检者拍摄胸部数字影像。设毫安秒不变，管电压分别为125K，100KV，80KV。每个受检者同时获取3种电压的胸部影像。以通用的影像质量评价指标评价不同电压组别的影像质量。结果 ①125KV、100KV、80KV管电压条件下，3组胸部后前位影像质量差异有显著性意义。②3组不同管电压的胸部前后位影像的质量以125KV最优。结论 DDR如传统X线屏胶系统胸部前后位一样，高千伏摄影的影像质量优于低千状摄影。     

Improvement of precision in spatial localization of radio-opaque markers using the two-film technique.

Radio-opaque markers implanted inside or placed on the skin of patients can be used to detect set-up errors and patient motion. The effects of imaging geometry accuracy for standard radiotherapy equipment on the precision of calculating the positions of radio-opaque spherical markers using two orthogonal radiographic film projections is investigated. Inaccuracies in the imaging geometry are computed from the manually digitized positions of the marker images on each film pair. Actual marker locations are calculated with a precision limited only by the variance in manual digitization by incorporating those imaging geometry inaccuracies into their computation. Results of a phantom study using a grid of markers in a plastic block indicate that submillimeter precision can be obtained for the spatial coordinates of individual markers, and that the precision is not sensitive to the small inaccuracies in imaging geometry present within the mechanical tolerances of modern radiotherapy treatment machines and simulators.     

Integration of digital fluoroscopy with CT-based radiation therapy planning of lung tumors

Radiation dose escalation may be a means to increase the local control rate of inoperable lung tumors. Treatment plans involve the creation of a uniform planning target volume (PTV) to ensure proper coverage despite patient breathing and setup error. This may lead to unnecessary radiation of normal tissue in shallow breathers or target underdosing for patients with excess internal motion. Therefore, the nature of tumor motion for each patient should be measured in 3D, something that cannot be done with CT alone. We have developed a method that acquires 2D real-time fluoroscopic images (loops) and coregisters them with 2D digitally reconstructed radiographs (DRR) formed from the CT scan. The limitations of CT to encompass motion can be overcome by merging the two modalities together. The accuracy of the coregistration method is tested with a stationary grid of radio-opaque markers at various spatial positions. The in-plane (at-depth) displacement between markers on the fluoroscopic image versus the DRR varies with position across the image due to slight misalignments between the x-ray source used in fluoroscopy and the virtual source used for the DRR relative to the test object. At clinically relevant positions, the maximum, measured in-plane displacement, is 1.1 mm. The method is applied to the thorax of an anthropomorphic phantom and a good fit is observed between the appearances of the bony anatomical structures on the coregistered image. Finally, a series of motion measurements are carried out on two oscillating cylindrical objects. The degree of motion as measured by fluoroscopy is accurate to within 1.0 mm, whereas the DRR is inconsistent in predicting motion. The coregistration of fluoroscopic loops with the DRR shows at what point within the oscillation the DRR fails to encompass motion. For any treatment site involving target motion, this real-time imaging is a useful asset in the planning stage.     

Signal detection in digital chest-phantom images acquired with an image intensifier

Signal detection performance was evaluated on the basis of ROC analysis using both digital and conventional images of a humanoid chest phantom. Simulated focal (coin) lesions were the target pathology. Digital images were acquired using a 57-cm image intensifier, digitized to 1024 x 1024 x 10 bits, and compared, in both video and laser-printed film formats, with conventional 14 x 17-inch chest films. Signal detection using digital video and laser printed images, of the same image polarity as conventional images, was found not to differ significantly from that achieved using conventional images, despite the smaller size of the digital images.     

Automated curved planar reformation of 3D spine images

Traditional techniques for visualizing anatomical structures are based on planar cross-sections from volume images, such as images obtained by computed tomography (CT) or magnetic resonance imaging (MRI). However, planar cross-sections taken in the coordinate system of the 3D image often do not provide sufficient or qualitative enough diagnostic information, because planar cross-sections cannot follow curved anatomical structures (e.g. arteries, colon, spine, etc). Therefore, not all of the important details can be shown simultaneously in any planar cross-section. To overcome this problem, reformatted images in the coordinate system of the inspected structure must be created. This operation is usually referred to as curved planar reformation (CPR). In this paper we propose an automated method for CPR of 3D spine images, which is based on the image transformation from the standard image-based to a novel spine-based coordinate system. The axes of the proposed spine-based coordinate system are determined on the curve that represents the vertebral column, and the rotation of the vertebrae around the spine curve, both of which are described by polynomial models. The optimal polynomial parameters are obtained in an image analysis based optimization framework. The proposed method was qualitatively and quantitatively evaluated on five CT spine images. The method performed well on both normal and pathological cases and was consistent with manually obtained ground truth data. The proposed spine-based CPR benefits from reduced structural complexity in favour of improved feature perception of the spine. The reformatted images are diagnostically valuable and enable easier navigation, manipulation and orientation in 3D space. Moreover, reformatted images may prove useful for segmentation and other image analysis tasks.