Large GISTs
As the tumor grows it may project outside the bowel (exophytic growth) and/or inside the bowel (intraluminal growth), but they most commonly grow exophytically such that the bulk of the tumor projects into the abdominal cavity. If the tumor outstrips its blood supply, it can necrose internally, creating a central fluid-filled cavity with bleeding and cavitations that can eventually ulcerate and communicate into the lumen of the bowel. In that case, barium swallow may show an air, air-fluid levels or oral contrast media accumulation within these areas. Mucosal ulcerations may also be present. In contrast-enhanced CT images, large GISTs appear as heterogeneous masses due to areas of living tumor cells surrounding bleeding, necrosis or cysts, which is radiographically seen as a peripheral enhancement pattern with a low attenuation center. In MRI studies, the degree of necrosis and bleeding affects the signal intensity pattern. Areas of bleeding within the tumor will vary its signal intensity depending on how long ago the bleeding occurred. The solid portions of the tumor are typically low signal intensity on T1-weighted images, are high signal intensity on T2-weighted images and enhanced after administration of gadolinium. Signal-intensity voids are present if there is gas within areas of necrotic tumor. Features of malignancy
Malignancy is characterized by local invasion and metastases, usually to the liver, omentum and peritoneum. However, cases of metastases to bone, pleura, lungs and retroperitoneum have been seen.
Typically, these devices are placed in the left upper chest and enter the left subclavian vein and electrodes are placed in the right atrium, right ventricle, and coronary sinus (for the left ventricle stimulation). Valve assessment
Echocardiography is a non-invasive method to evaluate the heart valves. However, sometimes the valve pressure gradients need to be measured directly because echo is equivocal for the severity of valve disease. Invasive assessment of the valve can be done with catheterization by placing a catheter across the valve and measuring the pressures simultaneously on each side of the valve to obtain the pressure gradient. In conjunction with a right heart catheterization, the valve area can be estimated. For example, in aortic valve area calculation the Gorlin equation can be used to calculate the area if the cardiac output, pressure gradient, systolic period, and heart rate are known. Pulmonary angiography
Evaluation of the blood flow to the lungs can be done invasively through catheterization. Contrast is injected into the pulmonary trunk, left or right pulmonary artery, or segment of the pulmonary artery. Shunt evaluation
Cardiac shunts can be evaluated through catheterization. Using oxygen as a marker, the oxygen saturation of blood can be sampled at various locations in and around the heart. For example, a left-to-right atrial septal defect will show a marked increase in oxygen saturation in the right atrium, ventricle, and pulmonary artery as compared to the mixed venous oxygen saturation from the oxygenated blood from the lungs mixing into the venous return to the heart.