Ultrafast computed tomography techniques in cardiac disease

Ultrafast computed tomography (UFCT) with scan times in milliseconds has matured as an important diagnostic instrument since it was first introduced. Dynamic scanning can be performed virtually anywhere and the short scan times give cross-sectional images free of artifacts. These factors allow one to obtain CT studies in many different heart disorders, even in the postoperative period while the patient is on cardiopulmonary assist devices. The evaluation of coronary artery bypass graft patency remains an important use of the modality.     

Ultrafast computed tomography in assessing coronary bypass grafts

The evaluation of chest pain in the postoperative coronary artery bypass graft patient is an important part of the cardiologist's and cardiothoracic surgeon's practice. Ultrafast computed tomography, by virtue of its speed and 0.75- to 1.5-mm spatial resolution, can detect graft patency with sensitivities of 93% to 96% and specificities of 86% to 100% in 94.2% of patients studied. Although image resolution is insufficient to demonstrate graft stenosis or sequential anastomoses, ultrafast computed tomography is becoming an increasingly important, minimally invasive imaging modality for the evaluation of coronary artery bypass graft patency.     

Ultrafast computed tomography in the diagnosis of cardiac disease

Ultrafast computer tomography (CT) is one of the major new imaging modalities that has become available for the evaluation of patients with heart disease. With cine CT it is possible to obtain high resolution images of the heart at 58-ms intervals. The inplane resolution is 0.7 to 1.5 mm, and the slice thickness is 3 to 9 mm. Images require the intravenous injection of nonionic contrast agents to obtain quantitative information about cardiac function. Cine CT has thus far been used in 3 general areas that relate to the evaluation of patients with heart disease: evaluation of cardiac structure and function, evaluation of vein bypass graft patency and flow reserve, and measurements of regional myocardial perfusion. Because of the outstanding spatial resolution of the images, it is possible to obtain very precise information about cardiac structure and function. The weight of the left ventricle and right ventricular walls can be measured to +/- 5%, and the stroke volumes and end-diastolic volumes of all 4 cardiac chambers can also be measured with an accuracy of +/- 5%. With this technology it is possible to determine the magnitude of aortic regurgitation within +/- 5 to 8%. This modality has also proved useful in the diagnosis of surgically resectable left ventricular aneurysm and a multitude of other cardiac disorders that involve abnormalities in cardiac structure, including congenital heart defects, aortic aneurysms and constrictive pericarditis. These diagnostic procedures use the peripheral injection of usually about 100 ml of contrast media and can ordinarily be completed in less than 15 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrafast computed tomography in the diagnosis of diseases of great vessels

Rapid and accurate detection of great vessel disease is of enormous importance in clinical practice. The search continues for the best technique to evaluate critically ill patients with acute aortic dissection and/or acute pulmonary embolism. Because of its speed and excellent spatial resolution, ultrafast computed tomography (CT) is a very useful tool and may alter the management of patients with aortic disease. Other techniques, such as magnetic resonance imaging (MRI) and transesophageal echocardiography (TEE) are also used in the diagnosis of aortic dissection. Each technique has advantages and pitfalls. At this time it is likely that one technique will complement the other. With further technical improvements, both MRI and ultrafast CT are likely to emerge as the diagnostic tests of choice. In the future, further validation and comparative studies in the acute setting may help to identify the most accurate and useful technique.     

Ultrafast computed tomography in the diagnosis of aortic aneurysms and dissections

UFCT, by virtue of its 50 to 400 millisecond acquisition times, 0.75 to 1.5 mm resolution, and excellent vascular opacification, provides a rapid, minimally invasive method for assessing aortic aneurysms and dissections. During a 3.5-year period, 50 patients with suspected thoracic, thoracoabdominal, and abdominal aortic aneurysms or dissections were evaluated using the Imatron C-100 UFCT scanner. Eighteen patients had thoracic or thoracoabdominal aneurysms. 17 had thoracic or thoracoabdominal dissections, 7 had abdominal aneurysms, and in 8 no aneurysms or dissections were found. In 23 of the 35 patients with thoracic or thoracoabdominal aneurysms or dissections, the UFCT findings accurately reflected the findings at aortography, surgery, or autopsy. There was one false-positive examination. The remaining 11 patients with UFCT findings of aneurysm or dissection were followed clinically. In the 7 patients with abdominal aneurysms, 4 were confirmed by angiography or surgery, and 3 were followed clinically. Of the 8 patients with negative UFCT examinations, 2 had subsequent angiography that failed to show an aneurysm, and 6 were followed from 6 to 30 months without developing findings suggestive of aneurysm. UFCT appears to be a useful, minimally invasive technique for detecting and following aortic aneurysms and dissections.     

Ultrafast computed tomography in management of post-bentall aortic root pseudoaneurysm repair

A giant pseudoaneurysm adjacent to the sternum was diagnosed in a patient who had undergone aortic root replacement with use of the Bentall operation 10 years earlier. Electron-beam computed tomography showed that the right coronary artery, which could not be seen on angiography, originated from the pseudoaneurysm itself. At reoperation, we found that both coronary ostia were detached and that the right coronary ostium was totally detached. The source of the right coronary artery blood flow was the pseudoaneurysm itself The defect at the left coronary artery attachment site was repaired primarily. A vein graft was interposed between the ostium of the right coronary artery and the native aorta, distal to the graft anastomosis.     

Ultrafast computed tomography analysis of regional radius-to-wall thickness ratios in normal and volume-overloaded human left ventricle.

BACKGROUND. This study tested two hypotheses: 1) regional left ventricular radius-to-wall thickness ratios (R/T) are uniform in normal subjects, and 2) patients with left ventricular hypertrophy secondary to compensated volume overload normalize global and regional R/T. METHODS AND RESULTS. Ultrafast computed tomography was used to measure regional short-axis ventricular R/T in 11 normal subjects and 13 patients with compensated aortic insufficiency (AI) of moderate severity (regurgitant fraction, greater than or equal to 25%). Radius and wall thickness dimensions were calculated by two different methods. In method 1, the average radius and wall thickness were determined for each planimetric transaxial tomographic image. In method 2, the left ventricle was three-dimensionally reconstructed; then, new radii and wall thickness were recalculated as if all the images were acquired orthogonal to the endocardial surface at each tomographic level. In normals, the mean R/T ratio was 1.75 +/- 0.11 (SEM) with method 1 and 1.80 +/- 0.07 with method 2. The R/T ratios varied as a function of the relative apex-to-base position. R/T ratios at the basal four levels were relatively uniform, whereas R/T at the lower three tomographic levels were significantly less than those at the base (p less than 0.01). Patients with AI had a mean regurgitant fraction of 44 +/- 3.8% (range, 25-63%). The mean R/T ratio was 2.18 +/- 0.16 with method 1 and 2.55 +/- 0.18 with method 2. Similar to the pattern observed in normals, the regional R/T ratios at the lower three or four levels were significantly less than the basal R/T ratios (p less than 0.01). Regional comparison of the normal to the volume-overloaded ventricles demonstrated that R/T ratios in the AI patients were significantly greater at the upper five levels with method 1 and at all eight levels with method 2 (p less than 0.01-0.001, AI versus normal). CONCLUSIONS. These findings demonstrate that regional R/T ratios are heterogeneous in both normals and patients with left ventricular hypertrophy secondary to compensated aortic insufficiency. Furthermore, these findings challenge the accepted hypothesis that global and regional R/T ratios normalize in patients with compensated volume-overload hypertrophy.     

Rings, slings and other vascular abnormalities. Ultrafast computed tomography and magnetic resonance angiography in pediatric cardiology

Ultrafast CT and MR angiography are noninvasive, accurate and robust techniques for preoperative diagnosis and planning of congenital heart disease and vascular abnormalities in pediatric patients. While they seem to be equivalent to conventional catheter angiocardiography for detecting vascular abnormalities, they are more accurate for the diagnosis of potentially life-threatening complications, such as tracheal, bronchial or esophageal compression. The value of ultrafast CT and MR angiography is demonstrated in 22 pediatric patients with vascular rings, slings and other vascular abnormalities.     

Positron emission tomography and computed tomography versus positron emission tomography computed tomography: tools for imaging the lung

This article reviews the potential use of positron emission tomography (PET), alone and in combination with computed tomography, for evaluating the severity of disease in cystic fibrosis. PET scanning using injected 18F-fluorodeoxyglucose provides visual and quantitative information for the rate at which glucose is taken up by the lung, a process that should relate to the presence of inflammation and reflect the extent of the disease. The computed tomography scan gives highly accurate density and anatomic information to locate areas of inflammation seen on the PET scan, increasing the accuracy of the interpretation. Until recently, the scanners have been single systems, often located in separate hospital departments. Combined systems are now commercially available, with major advantages for patients and in the quality of analytical information obtained for interpretation by the physician. The use of 18F-fluorodeoxyglucose uptake and PET scanning has been suggested as a biomarker of progressive pulmonary inflammation in cystic fibrosis. Although promising, the data so far are limited. Further studies will be needed to validate this measurement for this purpose.     

Colonography by computed tomography

Computed tomographic colonography ('virtual colonoscopy') has shown promising results in the detection of large (> or = 10 mm) polyps in populations with a high prevalence of polyps. Recent studies in low prevalence populations, however, show variable results in sensitivity, ranging from 55% to 94% for the detection of patients with polyps measuring 10 mm or longer. Therefore questions have been raised about computed tomographic colonography as a screening method, probably the most valuable use of this technique. This article describes possible causes of these remarkable differences as well as advances in computed tomographic colonography.     

Imaging of myocardial microvasculature using fast computed tomography and three-dimensional microscopic computed tomography

In the past, much attention in imaging research was focused on the macroscopic morphology and patency of arteries. Only recently, research and clinical interest have shifted to the microcirculation and its impact on the long-term prognosis in patients with vascular diseases. This focus and newly developed therapeutic strategies require high-resolution imaging modalities, which do not focus exclusively on the macroscopic aspects of the arterial tree. Provided here is a comprehensive perspective of using computed tomography technology to image and quantify the function and morphology of myocardial and vascular adventitial microvessels in normal and disease states.     

Eight-channel multidetector computed tomography: unique potential for pediatric chest computed tomography angiography

This case report of a possible aortic pseudoaneurysm after coarctectomy in a 12-month-old boy illustrates the unique considerations when performing pediatric cardiovascular CT angiography in young children. With newer (8-channel) multidetector technology, many of the complexities of performing diagnostic angiography, including sedation, breathing artifact, and intravenous contrast material administration, can be reduced or eliminated.