Introduction
A CAT scan, also known as a CT (computed tomography) scan, is a medical imaging technique that uses X-rays and computers to generate cross-sectional images of the body (WebMD, 2023). The scan allows doctors to see detailed images of the bones, organs, soft tissues and blood vessels inside the body.
The main purpose of a CAT scan is to help physicians diagnose and monitor health conditions. It can detect abnormalities, diseases, tumors, fractures and internal injuries. CAT scans provide more detailed images than regular X-rays and are often used to get additional diagnostic information when something suspicious shows up on an X-ray or MRI.
How a CAT Scan Works
CAT scans use a combination of x-rays and specialized computers to generate detailed images of your body. The acronym CAT stands for Computerized Axial Tomography. During the scan, you lie on a table that passes through a donut-shaped scanner. The scanner uses a rotating x-ray beam to take multiple images of your body in cross-section slices from various angles (University of Rochester Medical Center, 2022).
The computer then takes these 2D x-ray slices and stacks them together to generate a 3D model of your internal structures. The images highlight differences in density of various body tissues, allowing radiologists to distinguish between things like fat, muscle, bone, organs, and blood vessels (Johns Hopkins Medicine, 2022).
Compared to standard x-rays, CAT scans provide much more detail on the inside of your body without requiring invasive surgery. However, you are exposed to higher levels of radiation compared to regular x-rays because of the multiple images required (Cleveland Clinic, 2022).
Image Acquisition Time
The actual scan itself only takes a few minutes to complete. During the scan, the CT machine rotates around your body and takes multiple X-ray images from different angles. The entire imaging process typically lasts between 5-10 minutes if scanning one area of the body (American College of Radiology, 2022). For longer scans covering a larger area, such as a scan of the whole abdomen and pelvis, the imaging time may be up to 30 minutes.
You simply have to lie still on the scanning table while the machine rotates around you. No radiation remains in your body after the scan. The advanced technology of modern CT scanners allows them to capture hundreds of cross-sectional images in just seconds (Cleveland Clinic, 2023). So you can expect the actual image acquisition portion of your CT scan to be over in a matter of minutes.
Image Processing Time
After the scan is complete, complex computations are required to generate the final images from the raw data. This raw data essentially represents hundreds of individual X-ray measurements taken around the body from multiple angles. Sophisticated software and algorithms process this information to reconstruct cross-sectional images of internal organs and tissues (CT-scan Image Production Procedures). The time required depends on the computing power available, but often takes 5-10 minutes for a scan of the abdomen/pelvis and up to 30 minutes for a high-resolution scan of the whole body.
The latest iterative reconstruction techniques can significantly speed up image processing by reducing noise and enhancing image quality. However, iterative reconstruction may take 2-3 times longer than conventional filtered back projection methods. So there is a trade-off between faster scan times and optimal image quality.
Radiologist Review
Once the scan is complete, a specialist radiologist analyzes the images and generates a report. This is an important step, as the radiologist is trained to identify any abnormalities or concerning findings in the images. According to Mount Sinai Hospital, it takes approximately 48 hours for the radiologist to interpret the scan and relay the results to your doctor [1]. The time required depends on the complexity of the images and how busy the radiology department is.
For non-urgent cases, it may take a few days to over a week for the radiologist to review the images, as they have to prioritize more acute cases first [2]. However, for emergency situations, the radiologist will often provide a preliminary read of the images within minutes to hours so that doctors can make quick treatment decisions if needed.
Report Generation
After the radiologist reviews and interprets the images, they will generate a written report summarizing their findings. This is a key part of the process, as the report communicates the results to the doctor who ordered the scan.
According to Ganesh Diagnostics, it usually takes 1-2 hours for the radiologist to analyze the images, dictate findings, and finalize the report. The report is a detailed, technical document describing any abnormalities seen on the scan. It will note the location, size, shape and other characteristics of any concerning findings. The radiologist may also provide an impression or diagnosis based on the imaging findings.
The report aims to provide the referring physician clear information to aid in diagnosing or treating the patient. Once finalized, the report is sent to the doctor who ordered the scan. At this point, the radiologist’s role is complete. The ordering doctor then takes responsibility for reviewing the report, interpreting the results, and discussing findings with the patient.
Sharing Results
Once the radiologist has reviewed the images and written up the report, the results need to be communicated to the ordering physician and patient. There are a few ways this can happen:
For emergency scans like in the ER, the radiologist will often directly communicate the results to the ER doctor verbally right away if they show any acute findings. The radiologist’s full report will also be sent electronically to the hospital’s records system, where the ER doctor can review it in more detail.1
For outpatient scans, the radiologist will finalize the written report and send it to the ordering doctor, usually via fax or electronically through a health records system. The doctor reviews the radiologist’s report when available and then contacts the patient to discuss the results, either by phone or at the next appointment.2 This can take at least a few days up to a week or more, depending on schedules.
Patients may also request a copy of the radiology report be sent directly to them after the scan is completed. However, the report contains highly technical medical terminology and the findings often require explanation from the ordering doctor.
Total Time for Results
The total time it takes to get results from a CAT scan can vary depending on several factors. Here is an overview of the full timeline from start to finish:
The CAT scan itself only takes a few minutes to complete. The scanning process involves taking multiple X-ray images as the machine rotates around the body (Source 1). The actual image acquisition typically takes 5-10 minutes.
After the scan is complete, the images must be processed by a computer to create cross-sectional slices that can be viewed by the radiologist. This image processing step usually takes around 15-20 minutes once the scan itself is finished (Source 2).
The radiologist then reviews the images, analyzes them, and dictates a report. This is the step that takes the longest in the process. Radiologists are often reading and analyzing images from multiple patients at a time. It typically takes a few hours at minimum for the radiologist to get to your images and dictate the findings, but it can take up to 24-48 hours in some cases, especially if the images require consultation with other specialists (Source 1).
After the radiologist dictates the report, it must be transcribed and sent to your doctor. This administrative step adds another few hours. Your doctor will then review the report and contact you to discuss the results. From the time of your scan to getting the results from your doctor usually takes at least 24 hours, and often 48 hours or more (Source 3).
Perceived Wait Time
Even though a CAT scan may only take a few minutes to acquire images, patients often perceive the wait time to be much longer. This is especially true when there is no instant feedback or results provided right away (Chu, 2019). Without knowing what is happening during the scan and processing time, the wait can feel subjectively longer and lead to frustration or anxiety.
Research shows that longer waits negatively impact patients’ perception of care and satisfaction (Bleustein et al., 2014). Patients who are left waiting with no updates or explanation tend to perceive doctors as less capable and have less confidence in the care they receive. Even if the actual wait time is reasonable, the lack of communication makes it seem excessive.
Healthcare providers can improve patients’ experience by setting reasonable wait time expectations upfront and providing updates during any extended processing or review periods. Small gestures like offering reading material, TV, or snacks can also make the wait more bearable.
Conclusion
While the results of a CAT scan are not instantaneous, the entire process is designed to deliver them to patients reasonably quickly. The image acquisition itself only takes a few minutes. After that, there is some necessary image processing and review by a radiologist before the final report can be generated. However, this full process from start to finish for a typical CAT scan is often completed within 24 hours. The perceived wait time can feel longer to anxious patients awaiting results, but modern medical imaging delivers these results with impressive speed compared to older techniques. In summary, although final CAT scan results are not instant, patients can expect to receive them promptly in most cases.
