CT virtual endoscopy of the auditory ossicular chain: clinical applications.
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OBJECTIVE: To evaluate the clinical applications and limitations of CT virtual endoscopy (CTVE) in the auditory ossicular chain. METHODS: CTVE of the auditory ossicular chain was performed with 1.0 mm collimation at pitch 1.0, bone algorithm, 9.6 cm field of view, and 0.1-0.2 mm reconstruction interval in 40 patients with middle ear diseases. 30 cases were confirmed by surgery. Results were compared with the findings of axial high resolution CT (HRCT) and multiplanar reformation (MPR) images and surgery. RESULTS: The accuracy of CTVE images in detecting ossicular destruction was 92.6%, significantly higher than that of axial HRCT (83.9%) and multiplanar reformation (76.5%) images. CTVE could also clearly reveal the postoperative condition and congenital dysplasia of the auditory ossicular chain. CONCLUSIONS: CTVE can clearly demonstrate a three-dimensional image of the auditory ossicular chain and is useful in evaluating diseases of the ear, especially the auditory ossicles. CTVE could not clearly demonstrate abnormal soft tissue within the tympanic cavity, abnormal changes of the tympanic membrane and tympanic walls, and could be easily influenced by artificial factors. (+info)
Evaluation of cross-sectional luminal morphology in carotid atherosclerotic disease by use of spiral CT angiography.
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BACKGROUND AND PURPOSE: This study sought to determine the frequency of noncircular lumens in patients with significant carotid atherosclerotic disease and to evaluate the effect of noncircular lumens on stenosis measurement derived from angiographic projections. METHODS: One hundred consecutive patients presenting with an internal carotid artery stenosis of at least 50% were imaged with spiral CT angiography. The transverse morphology of the diseased lumen was assessed on axial images, and the frequency of noncircular lumens was determined. In these cases, maximum intensity projection angiograms were reconstructed in standardized angiographic planes and in a plane selected according to the luminal obliquity, which was chosen to optimize the angiographic representation of the maximal stenosis. North American Symptomatic Carotid Endarterectomy Trial (NASCET) measurements were calculated from the maximum intensity projection images, and differences between values obtained from standard and optimized projections were recorded. RESULTS: Noncircular lumens were observed in 18 of 100 patients and consisted of elliptical and linear transverse profiles. The transverse orientation of the lumen in these cases ranged from +90 degrees to -87 degrees relative to the anteroposterior plane. An increase in the calculated NASCET stenosis was demonstrated when measurements were obtained from angiographic reconstructions obtained in the exact plane of the luminal obliquity compared with standard angiographic projections. As a result, the stenosis severity was upgraded from moderate to severe in 2 patients. CONCLUSIONS: Noncircular transverse luminal profiles are not uncommon and may introduce error into NASCET calculations obtained from standard angiographic projections. (+info)
Spiral computed tomography of pulmonary embolism.
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Within the last several years, spiral computed tomography angiography (SCTA) of the pulmonary arteries has emerged as a noninvasive angiographic modality for the evaluation of patients with suspected pulmonary embolism (PE). SCTA is based on continuous computed tomography (CT) data acquisition during patient transport through the rotating X-ray tube and detector system, where scanning is performed in the time period in which the injected contrast material passes through the pulmonary arteries. Single detector spiral CT has a sensitivity of approximately 85-90% and a specificity between 88-95%. Sensitivity and specificity are very likely to increase with the use of multidetector spiral CT scanners that allow scanning of large lung volumes with a scan collimation as narrow as 1 mm. Currently, SCTA is most commonly used as a primary imaging method in patients with suspected PE, and as a second-line method in cases with inconclusive ventilation/ perfusion scintigraphy results. SCTA has proven to be cost-effective, especially in combination with ultrasound of the lower extremities. Limitations of the method include a decreased sensitivity for the detection of small isolated clots in the peripheral pulmonary arterial bed, and a potentially reduced image quality in patients with coexistent cardiopulmonary disorders. Despite these limitations, several studies have now documented that, in patients with suspected pulmonary embolism, it is safe to withhold anticoagulation therapy if a spiral computed tomography exam of the pulmonary arteries is negative and no lower extremity venous thrombosis is present. In the future, multislice computed tomography scanning of the pulmonary arteries with multiplanar reformation and one-stop shopping, i.e. scanning of the pulmonary arteries and the lower extremity veins in a single session, will further enhance the role of computed tomography angiography in the examination of patients with suspected pulmonary embolism. (+info)
Imaging techniques in treatment algorithms of pulmonary embolism.
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Pulmonary embolism (PE) is more often diagnosed post mortem by pathologists than in vivo by clinicians. The identification of practical diagnostic algorithms could reduce the rate of diagnoses first made at autopsy. The literature was reviewed for evidence-based approaches to PE diagnosis. Since the PE mortality rate greatly exceeds that of deep vein thrombosis (DVT), more emphasis was given to reports specifically dealing with PE diagnosis by objective pulmonary vascular imaging techniques than to those aimed at DVT detection. Several studies have shown that standardized clinical estimates can be effectively used to give a pretest probability to calculate, after appropriate objective testing, the post-test probability of PE. A prospective trial has shown that perfusion scanning, rather than ventilation/perfusion scanning, should be the imaging technique of first choice for the management of patients suspected of having PE. The clinical usefulness of spiral computed tomography has not as yet been firmly established. However, ongoing technological developments would probably render the technique accurate enough to replace conventional angiography. The authors propose a noninvasive diagnostic algorithm with high predictive accuracy (positive predictive value 96%; negative predictive value 98%) starting with a standardized assessment of clinical likelihood, followed by a perfusion scan and, eventually, spiral computed tomography in only a minority of patients (< 20%) with discordant clinical and scintigraphic findings. (+info)
Computed tomography and magnetic resonance imaging: past, present and future.
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The aims of this paper are to summarize the current recommendations for the use of computed tomography (CT) and magnetic resonance imaging (MRI) in the chest and to suggest some possible future developments. The main developments of CT in the chest have been the introduction of high-resolution CT (HRCT), spiral CT and, more recently, multidetector spiral CT. HRCT is defined as thin-section CT (1- to 2-mm collimation scans), optimized by using a high-spatial resolution (edge-enhancing) algorithm. Several studies have shown that HRCT closely reflects macroscopic (gross) pathological findings. HRCT currently has the best sensitivity and specificity of any imaging method used for the assessment of focal and diffuse lung diseases. The advent of spiral CT and, more recently, multidetector CT scanners, has allowed for major improvements in the imaging of airways, pulmonary and systemic vessels, and lung nodules. Spiral CT facilitates multiplanar and three-dimensional display of structures and visualization of pulmonary and systemic vessels, with a level of detail that is comparable to that of conventional angiography. With the use of graphics-based software programs, spiral CT enables depiction of the luminal surface of the airways with images that resemble those of bronchoscopy (virtual bronchoscopy) or bronchography (virtual bronchography). Several studies have shown a high sensitivity and specificity for spiral CT in the diagnosis of acute pulmonary embolism. Therefore, spiral CT is rapidly becoming the imaging modality of choice in the diagnosis of pulmonary embolism. Like the radiograph, signal intensity on computed tomography is mainly due to a single parameter: electron density. The signal intensity of the magnetic resonance image depends on four parameters: nuclear density, two relaxation times called T1 and T2, and motion of the nuclei within the imaged lung volume. Abnormal soft tissue can be identified more easily through measurement of these four parameters than through use of computed tomography. Furthermore, because the spatial orientation of the image is determined by manipulation of magnetic fields, scans can be performed in any plane. The main indications for magnetic resonance in the chest have been in the evaluation of the heart, major vessels, mediastinum, and hilar structures because of the natural contrast provided by flowing blood. Of particular interest for the respirologist has been the recent development of magnetic resonance angiography. This technique consists of three-dimensional single breath-hold images obtained using gadolinium-based contrast agents. This is a promising technique for the diagnosis of acute and chronic pulmonary embolism. (+info)
New imaging techniques in the treatment guidelines for lung cancer.
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Computed tomography (CT) remains the main imaging technique for the preoperative staging and post-therapeutic evaluation of bronchogenic carcinoma. Spiral CT has already overcome some of the problems encountered with central or more extensive tumours. Multislice CT offers further improvement and allows for scanning of the whole chest within a single breath-hold using a thin-section high-resolution technique. Problem-adapted sections in arbitrary directions become available and provide an excellent spatial resolution. One can expect improved accuracy for the evaluation of transfissural tumour growth, chest wall involvement, mediastinal infiltration and lymph node staging. Despite recent advances in magnetic resonance (MR) techniques for imaging the chest, the role of MR for staging of bronchogenic carcinoma remains limited. It offers advantages such as the assessment of chest-wall involvement or mediastinal involvement in patients in whom CT remains equivocal. Lymph-node-specific MR contrast agents offer new diagnostic potential for the assessment of metastatic disease. New techniques for the display of three-dimensional data sets include volume rendering and virtual bronchoscopy. These techniques represent new tools for the evaluation and demonstration of pathology within the central tracheobronchial tree. Their most important application is the guidance of bronchoscopic biopsies. The assessment of an indeterminate pulmonary nodule is frequently based on positron emission tomography imaging. As an alternative, nodule vascularization (contrast enhancement patterns on CT or magnetic resonance imaging (MRI)), calcifications (absorption characteristics at various X-ray energies on CT or dual energy radiography), and morphological features (high resolution imaging at CT) can be used as the basis for nodule differentiation. The dynamics of contrast enhancement in CT or MRI can also be used for the assessment of tumour viability after chemotherapy. Lung cancer screening programmes are still controversial. Low-dose computed tomography scanning and computed assisted detection algorithms based on chest radiographs or computed tomography scans form the technical basis for such projects. (+info)
Pulmonary emboli caused by iliac compression syndrome without leg symptoms.
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Iliac compression syndrome is a clinical condition that occurs as a result of compression of the left common iliac vein by the overlying right common iliac artery. This syndrome most often affects young to middle-aged women, and patients usually have left leg symptoms. We report the unusual case of an 18-year-old male who had pulmonary emboli caused by iliac compression syndrome without leg symptoms. Combined venography and aortography confirmed the diagnosis. The patient was successfully treated with anticoagulants and vena cava filter insertion. Iliac compression syndrome should be considered when pulmonary embolism appears without obvious cause. (+info)
Contrast-enhanced sonography of small pancreatic mass lesions.
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OBJECTIVE: To evaluate the usefulness of contrast-enhanced wideband harmonic gray scale sonography in assessing the vascularity of small pancreatic mass lesions. METHODS: Twenty-five patients with 25 pancreatic mass lesions (20 pancreatic carcinomas, 1 islet cell tumor, 1 malignant lymphoma, and 3 focal inflammatory pancreatic masses due to chronic pancreatitis) were examined. All patients held their breath for 20 to 50 seconds after injection of a contrast agent while the vascularity of the tumor was observed on contrast-enhanced wideband harmonic gray scale sonography (early phase). We then monitored the tumor enhancement 60 to 120 seconds after the injection while the patients held their breath for a few seconds (delayed phase). RESULTS: All 20 (100%) of the pancreatic carcinomas showed no contrast enhancement in the early phase. Fifteen (75%) of the 20 pancreatic carcinomas also showed no contrast enhancement in the delayed phase. The remaining 5 (25%) pancreatic carcinomas showed mild enhancement in the peripheral regions of the tumor in the delayed phase. The other pancreatic masses showed mild or pronounced enhancement throughout the entire lesions in both the early and delayed phases. CONCLUSIONS: Contrast-enhanced wideband harmonic gray scale sonography is a useful tool for differentiating pancreatic carcinomas from focal inflammatory pancreatic masses or hypervascular pancreatic tumors. (+info)