I was recently asked the question: “How low is low enough for CT?” With the risks of CT scans, the answer is: as low as you can go without significantly compromising diagnostic power.
Sometimes we do very noisy CT exams at extremely low doses, knowing that we may miss a 1 mm ureteral stone. However, we accept that possibility since such a small stone may not be clinically relevant.
Our routine abdominal/ pelvic exam is noisier than most of the CT exams we see referred in – but we deliberately chose to become accustomed to the higher noise levels (even when using iterative reconstruction) in order to minimize CT radiation dose. Thus, our doses are 40 percent lower than those on some of the CT scans we see being administered at many other places. There is no evidence we have compromised diagnostic power with our reduced dosage CT scans.
In today’s world, the 1-3 mSv cardiac CT is commonplace. In the near future, a CT of the abdomen and pelvis (40 cm of Z axis) using 0.6 mSv will soon be commonplace with the arrival of model based iterative reconstruction. With MBIR recently becoming available in the United States we will soon see dose reductions of up to 80 percent!