Based on these observations, we thus estimate that diagnostically adequate coronary artery enhancement may be obtained for a 70-kg patient with 1 45 gI injected at 1. A set of aortic and hepatic contrast enhancement curves was generated by reducing the baseline cardiac output, i. Oblique reformats are constructed similarly to axial or coronal images, except for the orientation of the images. Nippon Shokakibyo Gakkai Zasshi 99:1317-1325 47. The collateral circulation in cases of portal hypertension is also seen more clearly and with prominent paraumbilical collaterals, esophageal varices, and periportal circulation.
Thomsen, an international expert on contrast-media use in medical imaging, reflects on the concepts and risks associated with the use of contrast medium in pregnancy. As previously mentioned, the superior border of the region to be imaged is set at the top of the carina. A more recent study by Moon et al. It not only provides noninvasive assessment of the bowel wall but also yields valuable information on the extra-luminal manifestations of the disease not available with other conventional imaging methods. Determination of scan area of interest or scan length which also depends upon patient length or height can help to determine scanning parameters, scan duration, and contrast administration protocol. The increasing spatial and temporal resolutions have allowed major improvements to be made in differentiating and characterizing normal and abnormal structures and processes.
This results in a stretched out display of the b vessels. Microscopically, these cancers are classified according to the Lauren system as being of the intestinal type or diffuse type. Early stage gastric carcinoma has a relatively good prognosis, but unfortunately, patients usually present late, with advanced disease. . Hiroshige S, Nishizaki T, Soejima Y et al 2001 Beneficial effects of 3-dimensional visualization on hepatic vein reconstruction in living donor liver transplantation using right lobe graft. Int J Cardiovasc Imaging 20:535-540 52.
For a patient with a body weight of 60—80 kg, an injection rate of 1. A horizontal position may be a problem in obese patients, who often have associated sleep apnea, respiratory problems, or claustrophobia. According to Hong et al. Examples are hepatocellular carcinomas, metastases from melanoma, breast cancer, carcinoid, thyroid medullary carcinoma, islet cell tumors, and renal cell carcinoma. Differential color schemes again allow assessment of the position and depth of the metallic implants within the spine ment of vascular anatomy and disease. Whereas the magnitude of peak aortic enhancement increases substantially in patients with reduced cardiac output, the magnitude of peak hepatic enhancement increases only slightly. We thank those from the previous edition for their invaluable contributions, without which neither the previous nor the present edition would have been complete.
Menias School of Medicine Washington University St. Restaging sensitivity and specificity rates for local disease were 82% and 97%, respec- 198 M. The result is a largely unaltered contrast medium circulation time that is independent of patient weight. J Comput Assist Tomogra 22:288-294 28. The flyers are meant to be placed next to the scanner so that you and your staff always have expert advice on dose reduction at the fingertips. Of the 344 studies performed, only one 0. Since gallbladder carcinoma may show radiological features similar to chronic cholecystitis, to ensure adequate therapeutic management, it is important to differentiate between neoplasia and a chronic inflammatory process.
The most common findings include calculi and mild to moderate thickening of the gallbladder wall. The two most important factors that influence the detection of lesions is lesion size and its intrinsic vascularity. If peripheral intravenous access is not possible and intravenous contrast is needed, a cen- c tral access via a femoral or subclavian approach may be attempted by the radiologist. For these studies, multiplanar reconstructions can be performed at the scanner console from thinner reconstructions or directly from the volumetric raw data. This is partly due to the development of better volume-rendering techniques, which, in addition to showing anatomic surfaces, produce excellent visualization of details beneath the surface. Second, the test injection tests the quality of the intravenous access. Note better lesion-to-parenchymal contrast in the arterial-dominant phase in comparison with the portal venous phase image b where the lesion is not appreciated Table 1.
Accessed 17 Jan 2006 2. Although recurrent metastatic disease may occur without local nodal involvement, it is 196 M. The most common applications are evaluation of coronary bypass grafts and of chest pain. A common criticism of surface rendering is that it is not adequate for identifying structures that do not have naturally well-differentiated surfaces. The only factor that is of vital importance to consider is the pattern of enhancement following administration of contrast.
After administration of intravenous contrast material, the tumor demonstrates variable but heterogeneous enhancement Figs. Blake tively, with rates of 100% and 90% reported for distant disease. The result is a reduced magnitude of contrast enhancement. Based on our previous work, there is cause for optimism that the increased availability of emerging technologies, such as automatic tube-current modulation, will achieve significant dose reductions at least in the initial unenhanced phase. However, for venous phase imaging, delays of 65—70 s, 60 s or less from the start of injection, are Reduced volumes of contrast injection are not favored for liver imaging due to concerns about image quality. Implementation of 3-D Techniques A dedicated 3-D imaging laboratory and trained personnel substantially improve the overall workflow of modern radiology departments.
The E-mail message field is required. Time-to-peak and magnitude of enhancement peak increases with contrast medium volume. However, false-positive results may occur with primary 184 M. In: Radiological Society of North America scientific assembly and annual meeting program. In: Radiological Society of North America scientific assembly and annual meeting program. A right-arm injection is preferred since contrast material injected into the left arm often fills the left brachiocephalic vein at the time of image acquisition, and dense opacification of the brachiocephalic vein can be the source of artifact in the anterior mediastinum.
Kalra Sanjay Saini Geoffrey D. Faster scanning technology allows for increased scan coverage within a single breath-hold. One way of achieving this is by increasing the injection speed. Oblique reformats are particularly useful in cardiac, hepatic, and pancreatic imaging. Radiol Clin N Am 45:231-246 3.