Diagnosis of aortic dissection: value of helical CT with multiplanar reformation and three-dimensional rendering

Incorrect Diagnosis of Type A Aortic Dissection Attributed to Motion Artifact During Computed Tomographic Angiography: A Case Report

Early diagnosis of aortic dissection is important to reduce mortality, with surgical management representing standard treatment. Current methods of diagnosing type A aortic dissection include computed tomography angiography (CTA), magnetic resonance imaging, catheter-based arteriography, and transesophageal echocardiography. While each method has merits, there exists potential for false-positive findings. We present a case of a patient who was diagnosed with type A aortic dissection by CTA, but was found to not have an aortic dissection by transesophageal echocardiography under general anesthesia, preventing an unnecessary sternotomy. The echocardiographic findings suggested CTA artifact.

A fatal outcome of thoracic aortic aneurysm in a male patient with bicuspid aortic valve

Thoracic aortic aneurysm is often an asymptomatic but potentially lethal disease if its most catastrophic complication – aortic dissection – occurs. Thoracic aortic dissection is associated with a high mortality rate despite ongoing improvement in its management. We report a fatal outcome of thoracic aortic aneurysm in a male patient with bicuspid aortic valve. The patient was qualified for elective surgery of the ascending aorta and aortic valve at the age of 39 but he did not agree to undergo the proposed procedure. Three years later, he experienced acute aortic dissection and died despite a prompt diagnosis and complex management.

Missed rib fractures on evaluation of initial chest CT for trauma patients: pattern analysis and diagnostic value of coronal multiplanar reconstruction images with multidetector row CT

OBJECTIVE

The objective of this study was to review the prevalence and radiological features of rib fractures missed on initial chest CT evaluation, and to examine the diagnostic value of additional coronal images in a large series of trauma patients.

METHODS

130 patients who presented to an emergency room for blunt chest trauma underwent multidetector row CT of the thorax within the first hour during their stay, and had follow-up CT or bone scans as diagnostic gold standards. Images were evaluated on two separate occasions: once with axial images and once with both axial and coronal images. The detection rates of missed rib fractures were compared between readings using a non-parametric method of clustered data. In the cases of missed rib fractures, the shapes, locations and associated fractures were evaluated.

RESULTS

58 rib fractures were missed with axial images only and 52 were missed with both axial and coronal images (p=0.088). The most common shape of missed rib fractures was buckled (56.9%), and the anterior arc (55.2%) was most commonly involved. 21 (36.2%) missed rib fractures had combined fractures on the same ribs, and 38 (65.5%) were accompanied by fracture on neighbouring ribs.

CONCLUSION

Missed rib fractures are not uncommon, and radiologists should be familiar with buckle fractures, which are frequently missed. Additional coronal imagescan be helpful in the diagnosis of rib fractures that are not seen on axial images.

Clinical pathologic conference: A 65-year-old male with left-sided chest pain. A case of an unexpected occupational hazard

The authors present a case of a 65-year-old male who presented four times to the emergency department (ED) with left-sided chest pain. On the first three visits, the patient was admitted with a different diagnosis related to his chest pain. On the final visit, an abnormality on an imaging study performed in the ED led to the ultimate diagnostic test revealing the cause of the patient's symptoms. The patient's clinical presentation and ultimate clinical course are summarized, and a discussion of the differential diagnoses of his condition is presented.

Data management solution for large-volume computed tomography in an existing picture archiving and communication system (PACS)

Multidetector row computed tomography (MDCT) creates massive amounts of data, which can overload a picture archiving and communication system (PACS). To solve this problem, we designed a new data storage and image interpretation system in an existing PACS. Two MDCT image datasets, a thick- and a thin-section dataset, and a single-detector CT thick-section dataset were reconstructed. The thin-section dataset was archived in existing PACS disk space reserved for temporary storage, and the system overwrote the source data to preserve available disk space. The thick-section datasets were archived permanently. Multiplanar reformation (MPR) images were reconstructed from the stored thin-section datasets on the PACS workstation. In regular interpretations by eight radiologists during the same week, the volume of images and the times taken for interpretation of thick-section images with (246 CT examinations) or without (170 CT examinations) thin-section images were recorded, and the diagnostic usefulness of the thin-section images was evaluated. Thin-section datasets and MPR images were used in 79% and 18% of cases, respectively. The radiologists' assessments of this system were useful, though the volume of images and times taken to archive, retrieve, and interpret thick-section images together with thin-section images were significantly greater than the times taken without thin-section images. The limitations were compensated for by the usefulness of thin-section images. This data storage and image interpretation system improves the storage and availability of the thin-section datasets of MDCT and can prevent overloading problems in an existing PACS for the moment.

Are multiplanar reconstructions necessary in routine body computed tomography practice?: what is the published evidence?

OBJECTIVE

During computed tomography interpretation, some anatomical regions are optimally displayed in planes other than axial. The purpose of this review was to define best interpretative practice, by demonstrating through literature review and case demonstration the computed tomography applications that should routinely include multiplanar viewing of the volume.

CONCLUSIONS

Owing to multidetector-row computed tomography technology, multiplanar reconstructions not only have become realistic and reliable but also, in some clinical settings, have been shown to improve diagnostic accuracy and interpretation speed.

Diagnostic potential of combined transthoracic echocardiography and x-ray computed tomography in suspected aortic dissection

BACKGROUND

Transesophageal echocardiography (TEE) and magnetic resonance imaging (MRI) are considered optimal diagnostic methods in the setting of suspected aortic dissection. However, although less sensitive as single modalities, transthoracic echocardiography (TTE) and contrast-enhanced computed tomography (x-ray CT) are more widely available and less costly.

HYPOTHESIS

This study was undertaken to compare the diagnostic performance and reliability of the combined use of TTE and x-ray CT with TEE and/or MRI findings in the setting of suspected aortic dissection.

METHODS

The diagnostic power of combined TTE and x-ray CT was compared with both single use of TTE and x-ray CT and with TEE and/or MRI in a series of 168 consecutive patients with suspected aortic dissection (AD). Of these, 28 women and 58 men (mean age 53 +/- 16 years) underwent TTE and x-ray CT prior to TEE (n = 52) and/or MRI (n = 69). Diagnostic results of combined TTE/x-ray CT were retrospectively but independently reevaluated in blinded fashion; diagnostic findings were validated by angiography (n = 63), surgery (n = 52), or autopsy (n = 7).

RESULTS

Type A dissection was found in 29 patients (34%), type B dissection in 10 (12%), whereas aortic dissection was excluded in 47 (55%). With 95%, the sensitivity of TTE and x-ray CT was significantly enhanced when used in a combined access compared with 67 and 79%, respectively, when used as single methods (95%; p < 0.05). Sensitivity and specificity (95 and 91%, respectively) of combined TTE/x-ray CT evaluation were not different from TEE and/or MRI (100 and 96%, respectively; NS). Thrombus formation, side-branch involvement, aortic regurgitation, pericardial effusion or mediastinal hematoma were also detected with similar sensitivities and specificities both by combined TTE/x-ray CT and TEE and/or MRI.

CONCLUSION

This first controlled study comparing the combined information of TTE and x-ray CT with TEE and/or MRI revealed a similar diagnostic potential of both diagnostic strategies in the setting of suspected aortic dissection. Thus, in an environment with access to color Doppler TTE and x-ray CT only, the information from both tests should be combined to decide on diagnostic management of these patients.

Visualization of congenital thoracic vascular anomalies using multi-detector row computed tomography and two- and three-dimensional post-processing

Anomalies of the vascular system are caused by false embryogenesis and are therefore present from birth. Single-detector row spiral computed tomography angiography (CTA) and multi-detector row computed tomography angiography (MDCTA) have gained increasing importance in the non-invasive assessment of vascular pathologies and replace conventional angiography in many cases. High-resolution volumetric datasets that are acquired during a single breath-hold give the possibility of two- (2D) and three-dimensional (3D)-post-processing. Due to post-processing, even complex vascular malformations are visualized in an understandable way. Furthermore, CTA, in contrast to conventional angiography, depicts not only the vascular structures but also allows assessment of the surrounding anatomical structures. We present cases of rare congenital anomalies of the thoracic vessels using MDCT with special respect to 2D- and 3D-post-processing.

Multidetector CT of the thoracic aorta

Recent advancement of MDCT provides high-resolution axial images with optimal contrast enhancement and 3D reformatted images of the thoracic aorta. MDCT is now playing a dominant and critical role in the evaluation of thoracic aortic disease. This article will focus on procedural considerations of MDCT: acquisition parameters, contrast injection and post-processing techniques and imaging findings of thoracic aortic diseases including, aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, aneurysm, and traumatic injury.

Comment, quand et pourquoi réaliser une imagerie de l’aorte thoracique chez l’adulte ?

CT, MRI and transesophageal echocardiography have become the standard of reference for evaluation of the thoracic aorta. Angiography is mainly performed as a presurgical procedure. Congenital pathologies observed during adulthood include coarctation, patent ductus arteriosus, and aberrant retroesophageal subclavian arteries. Imaging plays a major role for diagnosis and management of patients with acute aortic syndromes: intramural hematoma, dissection, penetrating ulcer and nondissecting aneurysms. Cross sectional imaging of the thoracic aortic wall allows evaluation of inflammatory diseases of the aorta or aortitis.

Multidetector row computed tomography of the aorta and peripheral arteries

MDCT represents a significant advance on SDCT and the advantages it brings are particularly clear in CTA applications. It allows cost effective assessment of longer segments of vascular territories to be imaged with higher spatial, contrast, and temporal resolution. It has replaced SDCT as the new CT standard and its technical abilities are rapidly approaching the temporal resolution of EBCT. With 3-D post processing tools its main benefit is in imaging studies customized to the patient's pathology, with greater measurement accuracy and reliable longitudinal assessment. MDCTA is increasingly applied not to individual vascular territories but to a complete assessment dictated by the pathology, such as the entire aorta and branch vessels in aneurysm evaluation and the aorta and the coronary arteries in dissection cases or the vascular and non-vascular chest in acute chest pain. Greater accuracy of vessel assessment will lead to a refinement of interventional and surgical techniques for an individual patient and facilitates conservative management of conditions that can be reliably monitored non-invasively and the development of intervention criteria. MDCTA will continue to increase its major role in peripheral vascular evaluation in the future though its reliability in assessing small vessels below the knee and in the foot remains to be conclusively proven to obviate the need for diagnostic catheter angiography.

Multiplanar and three-dimensional multi-detector row CT of thoracic vessels and airways in the pediatric population

Multi-detector row computed tomography (CT) has changed the approach to imaging of thoracic anatomy and disease in the pediatric population. At the author's institution, multi-detector row CT with multiplanar and three-dimensional reconstruction has become an important examination in the evaluation of systemic and pulmonary vasculature and the tracheobronchial tree. In some clinical situations, multi-detector row CT with reformatted images is obviating conventional angiography, which is associated with higher radiation doses and longer sedation times. Although multi-detector row CT with multiplanar and three-dimensional reconstruction is expanding the applications of CT of the thorax, its role as a diagnostic tool still needs to be better defined. The purposes of this article are to describe how to perform multi-detector row CT with multiplanar and three-dimensional reconstruction in young patients, to discuss various reconstruction techniques available, and to discuss applications in the evaluation of vascular and airways diseases.

Thoracic involvement of type A aortic dissection and intramural hematoma: diagnostic accuracy--comparison of emergency helical CT and surgical findings

PURPOSE

To assess the accuracy of various findings at emergency helical computed tomography (CT) for the evaluation of thoracic involvement of type A aortic dissection (AD) and type A intramural hematoma (IMH) and to compare these findings with those at surgical confirmation.

MATERIALS AND METHODS

Fifty-seven patients with acute chest pain underwent emergency helical CT and subsequent surgery for type A AD or IMH. Patients in whom AD or IMH was detected in three segments of the thoracic aorta or those in whom there was a site of any entry tear, arch branch vessel involvement, pericardial effusion, or aortic arch anomaly were examined at helical CT. Sensitivity, specificity, and accuracy of helical CT, along with 95% CIs, were calculated by using surgical confirmation as the reference standard.

RESULTS

For the detection of AD or IMH of the thoracic aorta, the accuracy of helical CT was 100%. The sensitivity, specificity, and accuracy, respectively, were 82%, 100%, and 84% for an entry tear; 95%, 100%, and 98% for arch branch vessel involvement; and 83%, 100%, and 91% for pericardial effusion. These values were all 100% for aortic arch anomalies.

CONCLUSION

Emergency helical CT of the thorax depicts findings that are highly accurate in the evaluation of acute type A AD and IMH.

Semitransparent volume-rendering CT angiography for lesion display in aortoiliac arteriosclerotic disease

PURPOSE

The potential of semitransparent volume-rendering (STVR) computed tomographic (CT) angiography was evaluated for the assessment of hemodynamically significant stenoses in aortoiliac arteriosclerotic disease.

MATERIALS AND METHODS

In a prospective study, 76 patients (57 men, 19 women; mean age, 70 years) underwent single-detector (n = 26) or multidetector (n = 50) CT angiography of the aortoiliac region. Intraarterial digital subtraction angiography (DSA) was performed in each patient. STVR images with semitransparent display of arterial lumen (opacity, 50%) and vascular calcifications (opacity, 20%), as well as maximum-intensity projection (MIP), frontal/sagittal curved planar reformation (CPR), and MIP/axial studies were independently reviewed for hemodynamically significant lesions (> or =70% cross-sectional area reduction). DSA combined with invasive pressure measurement was used as the standard of reference. Vessel wall calcifications were classified according to a four-point scale (0, not calcified; 1, mildly calcified; 2, moderately calcified; 3, severely calcified).

RESULTS

Of the 380 reviewed vessel sections, 28 represented 70%-99% stenoses and 14 represented occlusions. For detecting >/==" BORDER="0">70% lesions, STVR as well as CPR and MIP/axial studies revealed significantly higher specificity (91%-94%), positive predictive value (PPV; 0.62-0.72), and accuracy (90%-94%) than MIP (specificity, 59%; PPV, 0.27; accuracy, 64%; P <.001) in moderately or severely calcified vessel sections. In noncalcified or mildly calcified sections, the specificity of MIP was comparable with the other rendering techniques (96%-98%; P values ranging from.34 to.77). No significant sensitivity differences were noticed among the CT angiography modalities: STVR, 79%; MIP, 88%; CPR, 83%; and MIP/axial, 93% (P values ranging from.12 to.78). Negative predictive values ranged from 0.97 to 0.99 (P values ranging from.14 to 1). Median calcification scores in sections with overestimated lumen narrowings were significantly higher (3, severely calcified) than in sections with correctly graded lumen width (1, mildly calcified) with all CT angiography modalities (P <.05).

CONCLUSION

With use of STVR, visualization of vascular lumen can be improved by rendering highly transparent mural calcifications. Hence, for three-dimensional presentation of aortoiliac arteriosclerotic disease, STVR studies should be preferred to MIPs as supplements to review of axial-source images.

Multiplanar and three-dimensional imaging of the thorax

Although axial images are sufficient for diagnosis in most instances, knowledge of multiplanar imaging techniques is essential to apply them in appropriate circumstances. In particular, appropriately applied multiplanar imaging adds confidence to interpretations and assists surgeons and bronchoscopists in planning procedures. The need for multiplanar imaging must be assessed before performing any study so that the image acquisition parameters allow for suitable reformations.

MDCT imaging of the aorta and peripheral vessels

Since its clinical introduction in 1991, volumetric CT scanning using spiral or helical scanners has resulted in a revolution for diagnostic imaging. Helical CT has improved over the past 8 years with faster gantry rotation, more powerful X-ray tubes, and improved interpolation algorithms, but the greatest advance has been the recent introduction of multi detector-row CT (MDCT) scanners [J. Comput. Assist. Tomogr. 23 (1999) S83]. Currently capable of acquiring four channels of helical data simultaneously, MDCT scanners have achieved the greatest incremental gain in scan speed since the development of helical CT and have profound implications for clinical CT scanning. Fundamental advantages of MDCT include substantially shorter acquisition times, retrospective creation of thinner or thicker sections from the same raw data, and improved three-dimensional (3-D) rendering with diminished helical artifacts. While these features will likely be important to many applications of CT scanning, including the characterization of focal lung and liver lesions through the creation of thin sections retrospectively, the greatest impact has been on CT angiography. The implication for CT angiography is that scans can be performed approximately three-times faster than is possible with the fastest single-detector CT scanner. For example a 1.25 mm nominal thick section (1.6 mm effective section thickness) can be acquired with a table speed of 9.4 mm/s, and a 2.5 mm nominal thick section (3.2 mm effective section thickness) can be acquired with an 18.8 mm/s table speed. The advantages of MDCT for imaging the vascular system can be broken down into three fundamental improvements over single detector-row CT scanners speed (faster), distance (longer), and section thickness (better). The focus of this article will be how multidetector-row CT technology has substantially improved aortoiliac and lower extremity arterial imaging.

3-D imaging with MDCT

Without doubt, the greatest challenge of multidetector-row CT is dealing with 'data explosion'. For our carotid/intracranial CT angiograms, we routinely have 375 images to review (300 mm coverage reconstructed every 0.8 mm); for aortic studies we have 450-500 images ( approximately 600 mm coverage reconstructed every 1.3 mm); and for a study of the lower extremity inflow and run-off, we may generate 900-1000 transverse reconstructions. While we could reconstruct fewer images for these data, experience with single-detector row CT scanners indicates that longitudinal resolution and disease detection is improved when at least 50% overlap of cross-sections is generated [Radiology 200 (1996) 312]. If we are to optimize our clinical protocols and take full advantage of these CT scanners, we will need to change the way that we interpret, transfer, and store CT data. Film is no longer a viable option. Workstation based review of transverse reconstructions for interpretation is a necessity, but the workstations must improve to provide efficient access to these data, and we must have a way of providing our clinicians with images that can be transported to clinics and the operating room. Alternative visualization and analysis using volumetric tools, including 3-D visualization must evolve from luxury to necessity. We cannot rest on historical precedent to interpret these near isotropically sampled volumetric data using transverse reconstructions alone [Radiology 173 (1989) 527]. Although the tools for volumetric analysis on 3-D workstations have evolved over recent years, they have probably not yet evolved to a level that routine interpretation can be performed as efficiently and accurately as transverse section review. Both hardware and software developments must occur. While current computer workstations and visualization software are certainly adequate for assessing these MDCT data volumetrically, the process is very time consuming. What follows are a description of current workstation capabilities and a brief discussion of where development needs to go to facilitate the complete integration of volumetric analysis into the interpretive process of CT data.

CT angiography of the arterial system

CTA has become an important diagnostic tool in the evaluation of vascular diseases in virtually all parts of the body. Whereas CTA is able to provide images depicting exquisite anatomic detail, careful scanning technique and selection of scan parameters are critical for high quality studies. The choices to be made when prescribing a scan can seem daunting at first, but if one applies the principles outlined previously, CTA can be a relatively easy, fast, and safe diagnostic technique that is effective in the majority of patients with vascular disease.

Multidimensional imaging of the thorax: practical applications

Over the past decade, faster CT scan times, thinner collimation, and the development of multirow detectors, coupled with the increasing capability of computers to process large amounts of data in short periods of time, have lead to an expansion in the ability to create diagnostically useful two-dimensional (2D) and three-dimensional (3D) images within the thorax. Applications within the thorax include, but are not limited to, evaluation of pulmonary and systemic vasculature, evaluation of the tracheobronchial tree, and delineation of diffuse lung disease. Pulmonary nodule volume and growth can be more accurately predicted, and represents an improvement in the evaluation of the solitary pulmonary nodule. Multiplanar images increase our understanding of thoracic anatomy and can help to guide bronchoscopic procedures. Because there are strengths and weaknesses to all the reconstruction algorithms, the utility of any given technique is dependent on the clinical question to be answered. For instance, although maximum intensity projection imaging (MIP) is helpful in the evaluation of micronodular lung disease, it is of little value in the diagnosis of aortic dissection. As the ability to generate faster and more precise multidimensional images grow, the demand for such imaging is likely to increase. In this review, the authors discuss the various reconstruction techniques available, followed by a discussion of the clinical applications.

Medial axis reformation: a new visualization method for CT angiography

RATIONALE AND OBJECTIVES

The authors performed this study to evaluate a new method (medial axis reformation [MAR]) for visualizing three-dimensional vascular data at electron-beam computed tomographic (CT) angiography.

MATERIALS AND METHODS

MAR was performed automatically with a personal computer-based workstation. After the region of interest was edited, voxels were divided into groups according to their path lengths. Centroids of groups were connected to form the medial axis. Then, the medial axis was refined with multiscale medial response. Bifurcations were also detected and refined. Finally, curved sections were generated through the branches and laid out onto a single image by using a splitting method. The authors performed MAR during electron-beam CT angiography of coronary arteries, common carotid arteries, and iliac arteries.

RESULTS

MAR displayed curved sections of branched vessels on one image, cut through the axis of vessels to show the vessel diameter objectively, and allowed the viewing direction to be altered arbitrarily.

CONCLUSION

Results of preliminary applications demonstrate that MAR is a valuable new visualization method for CT angiography.

Data explosion: the challenge of multidetector-row CT

The development of multi detector-row CT has brought many exciting advancements to clinical CT scanning. While multi detector-row CT offers unparalleled speed of acquisition, spatial resolution, and anatomic coverage, a challenge presented by these advantages is the substantial increase on the number of reconstructed cross-sections that are rapidly created and in need of analysis. This manuscript discusses currently available alternative visualization tecvhniques for the assessment of volumetric data acquired with multi detector-row CT. Although the current capabilities of 3-D workstations offer many possibilities for alternative analysis of MCDT data, substantial improvements both in automated processing, processing speed and user interface will be necessary to realize the vision of replacing the primary analysis of transverse reconstruction's with alternative analyses. The direction that some of these future developments might take are discussed.

Accuracy of helical computed tomographic angiography for the diagnosis of colonic angiodysplasia

BACKGROUND & AIMS

The diagnosis of colonic angiodysplasia is often challenging and relies on endoscopy or catheter angiography. We investigated whether computed tomographic angiography (CTA) contributes to the diagnosis of colonic angiodysplasia.

METHODS

Twenty-eight patients with suspected bleeding from colonic angiodysplasia were prospectively evaluated. Gastrointestinal bleeding was investigated by colonoscopy plus visceral angiography and by CTA. The level of agreement between CTA and the former procedures was determined.

RESULTS

CTA images of diagnostic quality were obtained in 26 patients. Eighteen patients were diagnosed with colonic angiodysplasia by colonoscopy plus visceral angiography, and 14 by CTA (kappa = 0.68; P < 0.001). Sensitivity, specificity, and positive predictive values of CTA for detection of colonic angiodysplasia were 70%, 100%, and 100%, respectively. CTA signs including accumulation of vessels in the colonic wall, early filling vein, and supplying enlarged artery were present in 55%, 50%, and 22% of cases, respectively. None of these signs were present in the 8 patients with obscure gastrointestinal bleeding and negative diagnostic investigation of the digestive tract.

CONCLUSIONS

CTA is a sensitive, specific, well-tolerated, and minimally invasive tool for the diagnosis of colonic angiodysplasia.

Raysum reconstruction algorithm in MR cholangiopancreatography

Magnetic resonance cholangiopancreatography (MRCP) is a new, non-invasive imaging technique for the visualization of the biliary ducts. The presence of stones within the choledocus is easily detectable in source images. However, three-dimensional reconstructions using the maximum intensity pixel (or projection) algorithm (MIP) fail to reproduce accurately the eventual presence of filling defects or parietal irregularities due to biliary stones. We used the Raysum algorithm in addition to the MIP in evaluating MRCPs of twelve patients with known choledocolithiasis. A visualization of the stones was obtained in nine (75%) patients by using the Raysum while visualization was obtained in one patient by using MIP. No additional sequences are required, and the post-processing time takes only a few seconds. The Raysum reconstruction can be successfully associated to the MIP in the three-dimensional evaluation of biliary stones in MRCP.

Helical CT in emergency radiology

Today, a wide range of traumatic and nontraumatic emergency conditions are quickly and accurately diagnosed with helical computed tomography (CT). Many traditional emergency imaging procedures have been replaced with newer helical CT techniques that can be performed in less time and with greater accuracy, less patient discomfort, and decreased cost. The speed of helical technology permits CT examination of seriously ill patients in the emergency department, as well as patients who might not have been taken to CT previously because of the length of the examinations of the past. Also, helical technology permits multiple, sequential CT scans to be quickly obtained in the same patient, a great advance for the multiple-trauma patient. Higher quality CT examinations result from decreased respiratory misregistration, enhanced intravenous contrast material opacification of vascular structures and parenchymal organs, greater flexibility in image reconstruction, and improved multiplanar and three-dimensional reformations. This report summarizes the role and recommended protocols for the helical CT diagnosis of thoracic aortic trauma; aortic dissection; pulmonary embolism; acute conditions of the neck soft tissues; abdominal trauma; urinary tract stones; appendicitis; diverticulitis; abdominal aortic aneurysm; fractures of the face, spine, and extremities; and acute stroke.

Aortic dissection

The presentation of aortic dissection in the emergency department may be more subtle than the classic description of a shocked patient with "ripping" chest pain. The epidemiology, variation in presentation, investigation, and management of aortic dissection are reviewed.

Pitfalls in image reconstruction of helical CT angiography: an experimental study

This study was undertaken to evaluate the effects of the object related factors: background tissue and the direction of vessels on the morphological reproducibility of helical CT angiography. Cylindrical tubes filled with a diluted contrast medium were prepared to obtain vascular phantoms. The scan was performed within various background tissues. For the evaluation of the direction of the vessels, two types of vascular phantoms were prepared. The phantoms were scanned by varying beam collimations and scan pitches. Reconstructed CT images were markedly affected by the background tissue. The reconstructed images were also affected by the direction of vessels.

CT angiography of the abdominal and thoracic aorta

Evaluation of the abdominal and thoracic aorta is one of the most common indications for CT angiography (CTA). CTA largely has replaced conventional angiography in the assessment of aortic aneurysms and dissections because it provides all the relevant anatomic information at reduced cost, morbidity, and radiation exposure. This article will focus on the technique, interpretation, and pitfalls in the CTA evaluation of the abdominal and thoracic aorta.

Three-dimensional CT angiography of the thorax: clinical applications

Spiral CT with three-dimensional (3D) display can provide a rapid noninvasive examination of the vascular system and has been shown to have a wide range of clinical applications in the thorax, including imaging of the aorta, pulmonary vasculature, and venous abnormalities. Three-dimensional images can provide views of the imaging volume from innumerable viewing angles for both the radiologist and referring clinician, and potentially obviate invasive procedures such as angiography. In this article, we will review many of these applications of spiral CT angiography with 3D displays. Emphasis is placed on study design, protocol selection, and display of pathology.

Recent Advances in Echocardiography of Aortic Disorders

Pathological processes affecting the thoracic aorta are a source of significant morbidity and mortality. It is not surprising therefore that many imaging modalities have evolved for comprehensive assessment of this vital structure. Currently available techniques include chest radiography, computed tomography, magnetic resonance imaging, echocardiography, and aortography. Compared with other modalities, echocardiography is the most attractive because of its advantages of speed, portability, immediate availability of results, and low cost. With recent advances in echocardiographic instrumentation, technology, and newer approaches such as multiplane transesophageal echocardiography it has evolved as the most promising imaging technique for diagnosis of aortic disorders, providing comprehensive information of the site and extent of aortic pathology and associated complications.

Spiral CT: vascular applications

Recent technical advances in CT have renewed interest in the development of CT angiography (CTA). CT angiography is a minimally invasive method of visualising the vascular system and is becoming an alternative to conventional arteriography in some situations. Spiral technology allows a volume of data to be obtained on a single breath-hold with no respiratory misregistration. Fast machines with second or subsecond acquisition times mean the images are obtained while there are high circulating levels of contrast medium giving peak vascular opacification from a peripheral intravenous injection. Accurate timing will ensure either the arterial or venous phase is imaged. Multiple overlapping axial images can be obtained from the data set with no increase in radiation dose to the patient and from these scans computer generated multiplanar and 3D images are obtained which can be viewed from numerous angles. CT angiography can be performed more quickly, less invasively and at reduced cost compared to conventional angiography.

Research-oriented image registry for multimodal image integration

To provide multimodal biomedical images automatically, we constructed the research-oriented image registry, Data Delivery System (DDS). DDS was constructed on the campus local area network. Machines which generate images (imagers: DSA, ultrasound, PET, MRI, SPECT and CT) were connected to the campus LAN. Once a patient is registered, all his images are automatically picked up by DDS as they are generated, transferred through the gateway server to the intermediate server, and copied into the directory of the user who registered the patient. DDS informs the user through e-mail that new data have been generated and transferred. Data format is automatically converted into one which is chosen by the user. Data inactive for a certain period in the intermediate server are automatically achieved into the final and permanent data server based on compact disk. As a soft link is automatically generated through this step, a user has access to all (old or new) image data of the patient of his interest. As DDS runs with minimal maintenance, cost and time for data transfer are significantly saved. By making the complex process of data transfer and conversion invisible, DDS has made it easy for naive-to-computer researchers to concentrate on their biomedical interest.

The clinical usefulness of routine stacked multiplanar reconstruction in helical abdominal computed tomography

RATIONALE AND OBJECTIVES

The authors evaluate the usefulness of stacked multiplanar reconstructions in routine, thick-section abdominal computed tomography.

MATERIALS AND METHODS

Twenty-five routine, thick-section contrast abdominal CTs performed with equivalent technique were reformatted by multiplanar reconstructions in sagittal and coronal planes sequentially from side-to-side and front-to-back. The image sets were submitted, first axial images only followed by axial plus multiplanar reconstructions (MPRs), to 5 separate physician readers including 2 radiologists and 3 nonradiologists. These readers graded the visualization of a variety of normal and up to 5 pathologic lesions per patient on a scale of 1 to 5 (5 = best).

RESULTS

The addition of sagittal and coronal multiplanar reconstructions significantly improved the visualization of all normal anatomic structures (mean axial only, 3.8; mean axial plus MPR, 4.1; P < 0.0001). In addition, most pathologic lesions were statistically better visualized with the addition of multiplanar reconstructions (mean axial images only, 3.9; mean axial plus MPR, 4.1; P < 0.0001). All five readers found improved visualization in nearly every category with the addition of the multiplanar reconstructions. However, in only 7% of cases, did a reviewer find new diagnostic information with the addition of MPR images.

CONCLUSIONS

Stacked multiplanar reconstructions of routine, thick-section abdominal CT has clinical value in both the display of normal anatomic and pathologic lesions. Further studies, however, are required to confirm these findings before it is commonly used.

Fast CT for aortic dissection

Results were evaluated in 81 patients with suspected acute aortic dissection who were examined on a fast CT system capable of a 1 s data acquisition time. 17 patients had Type A and nine had Type B dissections. Radiological assessment provided 78 confident reports and expressed some uncertainty about the diagnosis in three patients. Overall sensitivity for aortic dissection was 96.2% and specificity was 96.4%. When 78 confident reports alone were considered, both sensitivity and specificity reached 100%. Reconstruction of data at 100 ms intervals allowed discrimination between artefacts in the ascending aorta and Type A dissections. CT can often be used as the single investigation prior to surgery for acute Type A dissections.

Spiral CT angiography of the aorta

Imaging of the aorta and its branches has benefitted greatly from the development of spiral CT techniques, which are relatively fast and noninvasive. The volumetric acquisition of spatial information has permitted the computer to reformat images for inspection of the vessels by several methods from an infinite number of viewing angles. Most aortic diseases-including congenital anomalies, dissection, aneurysm, trauma, inflammation, infection, and thromboembolic disease-can be depicted with this technology. In selected cases, spiral CT may be the only imaging modality needed for the surgical planning of aortic repair. This report discusses the CT angiography technique, its application to a variety of disease states, its role relative to other imaging modalities, and guidelines for patient selection.