Abdomen CT scanning protocol notes.
Here is a one paragragh introduction to abdominal CT scanning. In a breast cancer patient for example, the CT scan is performed immediately after the injection of an X-ray dye. This helps show liver metastases.
Scanning is performed in the superior-to-inferior direction, starting one or two slices above the top of the liver.
These protocols are designed for oncologic imaging. Scanning during the portal venous phase is the most important in oncology. With only a few exceptions, most types of liver metastases can be diagnosed with portal venous phase imaging. The need for pre-contrast images and arterial phase images is not routinely warranted for metastatic screening. Since portal venous phase imaging is so important for abdomen imaging, it should be optimized in quality.
The radiology literature already indicates that scan delays should be between 60-70 seconds. The current protocols simply look closer at that recommendation, and identify specific optimum scan delay timing, based on the patient's weight. See the analysis of scan Delay timing, for additional info.
The dose of iodinated intravenous contrast agents is commonly prescribed as 100ml per patient, but some institutions use 150ml per patient. The current weight based protocol is able to produce uniformly excellent results in all patients, with a median dose of 100ml per patient, equaling the performance of fixed dose protocols using higher doses. Therefore these protocols save money. See the discussion of Doses, for additional info.
Kidney enhancement has uniform pattern across all patient weight categories. That is a significant indicator that large and small patients are benefiting equally from the timing of circulation of the contrast agent.
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