Many parents are surprised at how little time is needed for the actual data acquisition of a CT scan (i.e., when the images are actually taken). While the entire process of positioning the patient, setting up the scanner, and injecting the intravenous contrast (if needed) can take a few minutes, the actual time of radiation exposure to create the CT images is only a few seconds, at most.
Once that data is obtained, the scanner processes it in a variety of ways depending on the type of study performed and the clinical concerns of the ordering physician. For example, a patient getting an abdominal CT after a car accident may have the images processed differently than an abdominal CT performed for appendicitis. The technologist requires several minutes to process these images in specific ways before sending them to the viewing computer for interpretation by the radiologist.
Once all the images are processed and sent, the case is ready for review and dictation by the radiologist. But the amount of data received by the radiologist is tremendous—anywhere from a few hundred to several thousand images! The careful examination of all those images for any disease process or injury requires a bit of time. For a normal non-contrast head CT, it takes perhaps ten minutes. For a very abnormal and complex abdominal CT, perhaps 30-45 minutes, depending on a number of issues (particularly if there are prior studies of a long-standing disease requiring careful comparisons).
Another complicating factor is interruptions. As there are often multiple patients requiring evaluation and care within the Radiology department at any given time, more urgent matters may take precedence over a nonemergent study. A clinically unstable patient’s head CT scan after a car wreck may require interpretation before a routine follow-up tumor evaluation in a different patient, even though the latter was scanned earlier. Additionally, if there are multiple critical patients being imaged at once, it may mildly delay the technologist in completing the entire batch. In this situation, however, there is typically enough data available for the radiologist to quickly identify critical findings and notify the clinical team, even though the final report may not be dictated until 30 minutes later (at which time all the patient’s images are reviewed).
Of utmost importance is that our department provides your child with the best care possible. With this in mind, the radiologist may also review other relevant components of your child’s medical record (such as laboratory values or clinical notes) or ask for a second opinion from another radiologist if there is an unusual finding. Both of these processes can add time to the interpretation but will ultimately provide better care for the patient and family.
Dr. Carl Merrow, author; Glenn Miñano, BFA, editor; Meredith Towbin, copy editor