What is a 4D CT Scan?
Image generated from lung 4D CT.
Click on the image to enlarge.
Four-dimensional computed tomography (4D CT) represents the next step in imaging.
New technology makes CT scans much faster and more accurate than before. 4D CT uses this technology to take images that not only capture the location of your tumor, but also capture its movement and the movement of your body’s organs over time.
This is very valuable for accurately treating tumors located on or near organs that move, such as those in the chest and abdomen.
What can I expect during my 4D CT scan?
Taking a 4D CT image is similar to traditional CT scanning.
- During the procedure, you lie on your back.
- The scanner spins around you in a corkscrew path, taking constant images.
- It takes approximately 30 seconds to complete its path around your body.
The scanner makes a 4D image showing:
- Your body’s breathing.
- How the tumor moves.
- How movement of nearby organs affects the position of the tumor.
What are the benefits of 4D CT scans?
The information from your 4D CT scan allows the radiation oncologist to:
- Design more accurate treatments for moving tumors.
- Better target these moving tumors and deliver radiation within a certain interval in the breathing cycle.
- Reduce your risk of treatment-related side effects.
For instance, a tumor on the lung will move along with each breath, as the lung inflates and deflates. With traditional imaging, the oncologist can only know the position of the tumor at one point in the breath.
As a result, the oncologist aims radiation at the tumor, but the beam only hits the tumor during the one point of the breath matching the image. At other times, the beam may miss the tumor, or damage healthy tissue.
To compensate for this possibility, the oncologist may use lower, less effective levels of radiation, reducing the effectiveness of the entire treatment.
Through 4D CT, the radiation oncologist can deliver radiation within a certain interval in the breathing cycle.
This is done using gated intensity-modulated radiation therapy (IMRT), where the radiation is stopped when the tumor is not in the correct position.
This allows the use of higher, more effective levels of radiation, while minimizing the impact on healthy tissue.