Digital image processing

Digital image processing is now commonplace in radiology, nuclear medicine and sonography. This article outlines underlying principles and concepts of digital image processing. After completing this article, readers should be able to: List the limitations of film-based imaging. Identify major components of a digital imaging system. Describe the history and application areas of digital image processing. Discuss image representation and the fundamentals of digital image processing. Outline digital image processing techniques and processing operations used in selected imaging modalities. Explain the basic concepts and visualization tools used in 3-D and virtual reality imaging. Recognize medical imaging informatics as a new area of specialization for radiologic technologists.     

Three-dimensional reconstitution of bullet trajectory in gunshot wounds: A case report

In the medico-legal assessment of cases of aggression with firearms, imaging techniques have a particularly important role, especially in the study of a bullet’s path through the victim’s body. The analysis of these trajectories can be performed by the use of three-dimensional reconstitution techniques, namely Three-Dimensional Multi-Slice Computed Tomography (3D-MSCT). This imaging technique has been widely used in fatal cases, as a very important complement of the classical autopsy procedures, becoming known as “virtual autopsy” or “Virtopsy”. To our knowledge, no reports describing the use of 3D-MSCT in non-fatal cases have been described in the medico-legal literature. The authors present a case of a man with a gunshot injury, in the context of a multiple aggressor situation, in which it was not possible to extract the bullet. To accurately determine the bullet’s trajectory, 3D-MSCT was performed, thus contributing to a more reliable reconstruction of the crime scene in which the victim and the suspects were located.     

Post-mortem computed tomography angiography: past, present and future

The role of imaging has been long established in forensic practice as an adjunct to the conventional autopsy. Recently with the development of MDCT, there has been a large international push towards the development of the so called “near virtual autopsy.” Currently a large obstacle to the acceptance of “near virtual autopsies” is the failure of post-mortem imaging to yield detailed information about the coronary arteries. This is a major deficiency of post-mortem MDCT and MRI compared to conventional autopsy as standard clinical angiography relies on circulation. One possible way to overcome this is by the use of post-mortem MDCT angiography. This review paper considers the past, current and future advances in cadaver cardiac imaging which, if successful, will take radiological imaging one step closer to the widespread introduction of near virtual autopsies.     

Augmented and Mixed Reality: Technologies for Enhancing the Future of IR

Augmented and mixed reality are emerging interactive and display technologies. These technologies are able to merge virtual objects, in either 2 or 3 dimensions, with the real world. Image guidance is the cornerstone of interventional radiology. With augmented or mixed reality, medical imaging can be more readily accessible or displayed in actual 3-dimensional space during procedures to enhance guidance, at times when this information is most needed. In this review, the current state of these technologies is addressed followed by a fundamental overview of their inner workings and challenges with 3-dimensional visualization. Finally, current and potential future applications in interventional radiology are highlighted.     

A state-of-the-art pipeline for postmortem CT and MRI visualization: from data acquisition to interactive image interpretation at autopsy

The importance of autopsy procedures leading to the establishment of the cause of death is well-known. A recent addition to the autopsy work flow is the possibility of conducting postmortem imaging, in its 3D version also called virtual autopsy (VA), using multidetector computed tomography (MDCT) or magnetic resonance imagining (MRI) data from scans of cadavers displayed with direct volume rendering (DVR) 3D techniques. The use of the data and their workflow are presented. Data acquisition was performed and high quality data-sets with submillimeter precision were acquired. New data acquisition techniques such as dual-energy CT (DECT) and quantitative MRI, then were implemented and provided additional information. Particular findings hardly visualized in conventional autopsy can rather easy be seen at the full body CT, such as air distribution, e.g. pneumothorax, pneumopericardium, air embolism, and wound channels. MRI shows natural deaths such as myocardial infarctions. Interactive visualization of these 3D data-sets can provide valuable insight into the corpses and enables non-invasive diagnostic procedures. In postmortem CT imaging, not being limited by a patient depending radiation dose limit the data-sets can, however, be generated with such a high resolution that they become difficult to handle in today's archive retrieval and interactive visualization systems, specifically in the case of full body scans. To take full advantage of these new technologies the postmortem workflow needs to be tailored to the demands and opportunities that the new technologies allow.     

Targeted post-mortem computed tomography cardiac angiography: proof of concept

With the increasing use and availability of multi-detector computed tomography and magnetic resonance imaging in autopsy practice, there has been an international push towards the development of the so-called near virtual autopsy. However, currently, a significant obstacle to the consideration as to whether or not near virtual autopsies could one day replace the conventional invasive autopsy is the failure of post-mortem imaging to yield detailed information concerning the coronary arteries. To date, a cost-effective, practical solution to allow high throughput imaging has not been presented within the forensic literature. We present a proof of concept paper describing a simple, quick, cost-effective, manual, targeted in situ post-mortem cardiac angiography method using a minimally invasive approach, to be used with multi-detector computed tomography for high throughput cadaveric imaging which can be used in permanent or temporary mortuaries.     

Do medical examiners determine elder mistreatment as a cause of death?

This study examines the decision-making process of medical examiners in determining elder mistreatment in cases that present to the county morgue. Harris County Medical Examiners were surveyed about factors that influence the determination whether elder abuse or neglect was a contributor to the cause of death. At the time of the survey, all 11 Harris County Medical Examiners participated. Of these, 8 did not determine elder abuse or neglect as contributing to the cause of death in the 12 months prior to the survey, 6 reported that medical records were helpful “all the time”, 3 reported “most of the time”, and 2, indicated that the records were “some-times helpful”. The survey also indicated that information that assists medical examiners in identifying the potential for abuse or neglect ranged from “present most of the time” to “never present”. Multiple factors including autopsy findings, medical compliance, inconsistency in injury findings, and malnutrition were reported as helpful in determining elder abuse or neglect. Further studies are needed to determine additional factors that would provide medical examiners with the ability to more readily identify signs of elder abuse or neglect.     

Whole-body MRI in children: current status and future applications

Whole-body MRI (WBMRI) is a novel technique that makes imaging of the whole patient in a manner similar to scintigraphy or positron emission tomography (PET) possible. Unlike the latter two methods, it is without exposure to radiation and thus gaining increasing importance and application in pediatrics. With the introduction of a moving tabletop, sequential movement of the patient through the magnet has become possible with automatic direct realignment of the images after acquisition. The common scan plane is coronal with additional planes being added depending on the indication. WBMRI is targeted for maximum coverage of the body within the shortest possible time using the minimum number of sequences. The evaluation of the bone marrow has been the primary indication thus inversion recovery sequences like STIR or TIRM are mostly used with the T1-weighted sequence being added variably. For correct evaluation of the bone marrow in the pediatric age group understanding normal pattern of marrow transformation is essential. The primary role of WBMRI has been in oncology for the detection of tumor spread and also for the follow-up and evaluation of complications. The initial comparative studies of WBMRI with scintigraphy and PET in children have shown the high diagnostic potential of WBMRI. Emerging potential applications of WBMRI include the evaluation for osteonecrosis, chronic multifocal recurrent osteomyelitis, myopathies, and generalized vascular malformations. Future use of WBMRI may incorporate non-accidental trauma, virtual autopsy, body fat mapping and diffusion-weighted imaging.     

Homicide victims concealed in a freezer

Freezing as a method for hiding a body is rare. We report here a homicide case in which three bodies were concealed in a freezer. This presented the pathologist with the problem of how to thaw the bodies and simultaneously avoid decomposition of the uppermost body. The problem was solved by slow thawing in a refrigerated morgue and by removing the bodies one after the other from top to bottom. The victims were a 27-year old mother and her two daughters, 7 and 9 years of age. The perpetrator was the 34-year old now-divorced husband and father. All were refugees from Syria. The perpetrator fled back to Syria. He was later arrested in Syria, confessed the crime and was sentenced to life imprisonment. The autopsy findings is discussed and compared to finding reported in the scientific literature.     

Virtual medicine: Utilization of the advanced cardiac imaging patient avatar for procedural planning and facilitation

Advances in imaging technology have led to a paradigm shift from planning of cardiovascular procedures and surgeries requiring the actual patient in a “brick and mortar” hospital to utilization of the digitalized patient in the virtual hospital. Cardiovascular computed tomographic angiography (CCTA) and cardiovascular magnetic resonance (CMR) digitalized 3-D patient representation of individual patient anatomy and physiology serves as an avatar allowing for virtual delineation of the most optimal approaches to cardiovascular procedures and surgeries prior to actual hospitalization. Pre-hospitalization reconstruction and analysis of anatomy and pathophysiology previously only accessible during the actual procedure could potentially limit the intrinsic risks related to time in the operating room, cardiac procedural laboratory and overall hospital environment. Although applications are specific to areas of cardiovascular specialty focus, there are unifying themes related to the utilization of technologies.The virtual patient avatar computer can also be used for procedural planning, computational modeling of anatomy, simulation of predicted therapeutic result, printing of 3-D models, and augmentation of real time procedural performance. Examples of the above techniques are at various stages of development for application to the spectrum of cardiovascular disease processes, including percutaneous, surgical and hybrid minimally invasive interventions. A multidisciplinary approach within medicine and engineering is necessary for creation of robust algorithms for maximal utilization of the virtual patient avatar in the digital medical center. Utilization of the virtual advanced cardiac imaging patient avatar will play an important role in the virtual health care system. Although there has been a rapid proliferation of early data, advanced imaging applications require further assessment and validation of accuracy, reproducibility, standardization, safety, efficacy, quality, cost effectiveness, and overall value to medical care.     

基于MRI虚拟现实技术的盆底器官脱垂患者阴道形态的研究

目的采用MRI虚拟现实技术重建阴道并探讨盆底器官脱垂患者阴道的形态特征变化。方法 POP组20例,对照组20例。研究对象均行盆腔MR I检查。将采集的二维图像数据通过虚拟现实软件进行三维重建,并对特定横截面的阴道壁厚度、面积和阴道模型体积、形态进行观测。结果对比POP组和对照组阴道横截面正中矢状线距离,两组差异无统计学意义(均P>0.05)。POP组阴道横截面面积均大于对照组,且差异有统计学意义(均P<0.05)。POP组阴道体积大于对照组,经比较差异有统计学意义(P<0.05)。POP组有60%患者阴道形态不规则,呈不对称性。阴道轴向未见明显变化。结论 MRI虚拟现实技术是观察阴道形态的有效方法。POP患者未发现阴道本身结构的薄弱缺损,但存在形态改变,MR I表现的阴道形态变化可以间接地反映盆底支持组织的功能状态。     

Advances in ultrasound: from microscanning to telerobotics

This paper is in memory of W V Mayneord (1902-1988). Experiments conducted in Mayneord's laboratory were amongst the first to show that ultrasound had diagnostic potential. Now, one in every four imaging studies uses ultrasound. Amongst numerous contemporary advances, microscanning is concerned with imaging subcentimetre size volumes of tissue in three dimensions with 10-100 microns resolution. The traditional approach is by pulse echo imaging, with a focused ultrasonic beam in the frequency range 20-100 MHz. This approach may be complemented by ultrasonic CT (to correct for attenuation and speed variations), reflex transmission imaging (to provide attenuation data) and synthetic aperture scanning (to decrease imaging time). Harmonic microscanning may reduce artefacts, and elasticity imaging may also be possible. Microscanning is likely to have applications in pathology and in the operating room, for trackless microintervention, in molecular biology and drug studies, and in experimental imaging of small mammals including, in particular, the mouse. Robotics is the engineering science concerned with devices that are able to execute tasks usually performed by humans. Two procedures, ultrasonically guided biopsy and ultrasonic laparoscopy, are being used to demonstrate the feasibility of telerobotics. The approach is that of telepresence, as distinct from supervisory control or virtual reality. Problems associated with image compression and communications latency are identified. Although incremental developments in medical ultrasound have resulted from clinical pull, major advances have, in general, been due to technical push.     

Tales from the grave: Opposing autopsy reports from a body exhumed

We report an autopsy case of a 42-year-old woman who, when discovered, had been dead in her apartment for approximately 1 week under circumstances involving treachery, assault and possible drug overdose. This case is unique as it involved two autopsies of the deceased by two different medical examiners who reached opposing conclusions. The first autopsy was performed about 10 days after death. The second autopsy was performed after an exhumation approximately 2 years after burial. Evidence collected at the crime scene included blood samples from which DNA was extracted and analysed, fingerprints and clothing containing dried body fluids. The conclusion of the first autopsy was accidental death due to cocaine toxicity; the conclusion of the second autopsy was death due to homicide given the totality of evidence. Suspects 1 and 2 were linked to the death of the victim by physical evidence and suspect 3 was linked by testimony. Suspect 1 received life in prison, and suspects 2 and 3 received 45 and 20 years in prison, respectively. This case indicates that cocaine toxicity is difficult to determine in putrefied tissue and that exhumations can be important in collecting forensic information. It further reveals that the combined findings of medical examiners, even though contradictory, are useful in determining the circumstances leading to death in criminal justice. Thus, this report demonstrates that such criminal circumstances require comparative forensic review and, in such cases, scientific conclusions can be difficult.     

Differentiation of antemortem pulmonary thromboembolism and postmortem clot with unenhanced MRI: a case report

We report a case of a 39-year-old woman who died of fulminant pulmonary thromboembolism (PE). Autopsy showed classical findings of fulminant PE with occlusion of the bilateral main stem pulmonary arteries. Ancillary testing revealed inherited thrombophilia (Prothrombin 20,210 G?>?A and MTHFR 677 C?>?T mutation). Pre-autopsy postmortem computed tomography was used to test whether virtual imaging studies alone (virtual autopsy) would be sufficient to detect PE. Our studies show that computed tomography (CT) can differentiate antemortem clots from a postmortem clot in certain cases, particularly when combined with magnetic resonance imaging (MRI), which is superior in the assessment of soft tissue. We show that postmortem CT and MRI can aid in the diagnosis of pulmonary embolism by virtual autopsy, especially when used in conjunction.     

3D modeling and virtual endoscopy of the small bowel based on magnetic resonance imaging in patients with inflammatory bowel disease

RATIONALE AND OBJECTIVES: Small bowel MRI (MR imaging) is a new imaging modality that excellently depicts small intestine pathology in patients with inflammatory bowel disease. Virtual endoscopy based on sectional imaging is a recently introduced technique to create endoscopy like views. The aim of this study was to evaluate the feasibility of virtual small bowel endoscopy based on MR imaging in patients with Crohn disease. MATERIALS AND METHODS: Thirty consecutive patients with Crohn disease were scanned after oral application of pineapple juice for contrasting the small bowel. Dedicated high resolution T1 weighted 3D-FLASH sequences with fat suppression were used for volume scanning. Volume-rendered 3D models of the small bowel were created and virtual endoscopy was performed. The feasibility and quality of this new visualization method was assessed. RESULTS: In nine of 30 patients virtual endoscopy was considered as good quality (flight through the entire small bowel was possible, typical folds were revealed). In 18 patients fair quality (at least 4/5 of the small bowel were depicted adequately) was assessed. In three of 30 patients virtual endoscopy was not sufficiently possible because of inadequate bowel filling or breathing artifacts. Three fistulae diagnosed on 2D MRI were visualized on the virtual endoscopic view. CONCLUSION: Virtual endoscopy of the small bowel is feasible based on high resolution MR imaging. Vivid insight views and 3D models provide an interesting addition to sectional MR findings.     

High-dimensional medical imaging and virtual reality techniques

The development of real-time imaging techniques with 3D and 4D technologies has led to the possibility of virtual reality procedures. Autopsies can now be carried out with non-invasive procedures and globally transmitted via the internet to virtually any place in the world.     

Feasibility and validation of virtual autopsy for dental identification using the Interpol dental codes

Virtual autopsy is a medical imaging technique, using full body computed tomography (CT), allowing for a noninvasive and permanent observation of all body parts. For dental identification clinically and radiologically observed ante-mortem (AM) and post-mortem (PM) oral identifiers are compared. The study aimed to verify if a PM dental charting can be performed on virtual reconstructions of full-body CT’s using the Interpol dental codes. A sample of 103 PM full-body CT’s was collected from the forensic autopsy files of the Department of Forensic Medicine University Hospitals, KU Leuven, Belgium. For validation purposes, 3 of these bodies underwent a complete dental autopsy, a dental radiological and a full-body CT examination. The bodies were scanned in a Siemens Definition Flash CT Scanner (Siemens Medical Solutions, Germany). The images were examined on 8- and 12-bit screen resolution as three-dimensional (3D) reconstructions and as axial, coronal and sagittal slices. InSpace^® (Siemens Medical Solutions, Germany) software was used for 3D reconstruction. The dental identifiers were charted on pink PM Interpol forms (F1, F2), using the related dental codes. Optimal dental charting was obtained by combining observations on 3D reconstructions and CT slices. It was not feasible to differentiate between different kinds of dental restoration materials. The 12-bit resolution enabled to collect more detailed evidences, mainly related to positions within a tooth. Oral identifiers, not implemented in the Interpol dental coding were observed. Amongst these, the observed (3D) morphological features of dental and maxillofacial structures are important identifiers. The latter can become particularly more relevant towards the future, not only because of the inherent spatial features, yet also because of the increasing preventive dental treatment, and the decreasing application of dental restorations. In conclusion, PM full-body CT examinations need to be implemented in the PM dental charting protocols and the Interpol dental codes should be adapted accordingly.     

VRATS – Virtual-Reality-Arthroskopie-Trainingssimulator

The subject of this paper is a highly interactive medical training system for arthroscopic surgery; this is based on computer graphics and virtual reality (VR) techniques and offers an alternative to conventional training methods. To provide the virtual environment, a realistic 3D representation of the knee joint is derived from 2D medical image data. The use of tracking techniques guarantees an intuitive handling of the surgical instruments. The system allows navigation via a virtual camera and interaction with the virtual anatomical structures. First approaches for the simulation of tissue deformation caused by collisions with the instruments are implemented. One important advantage over conventional training systems is the possibility of verifying the training progress. Work is in progress on the realization of tactile feedback with the aim of providing a higher degree of interactive realism.     

Marked ventilation impairment due to progression of diffuse pleural thickening after cardiac surgery

A 64-year-old Japanese man presented with dyspnea and shortness of breath during exertion. Chest computed tomography revealed bilateral pleural effusion. He was drowsy because of CO₂ storage and died due to ventilatory impairment. His past medical history included a thymectomy and adjuvant radiotherapy with thymoma. He had undergone cardiac surgery and permanent pacemaker implantation. The autopsy examination revealed extensive bilateral pleural adhesions and diffuse visceral pleural thickening. An inspection of multiple lung sections failed to detect any asbestos body formation or mesothelioma. The patient''s pleural effusion and diffuse pleural thickening may have exacerbated after cardiac surgery. In this case, the progression and pathophysiology of the pleural thickening could be traced by imaging and an autopsy, and we were able to estimate the factors that exacerbated the pleural thickening and ventilation impairment.