Tips on how to reduce radiation dosage while performing abdominal CT scan

Tips on how to reduce radiation dosage while performing abdominal CT scan

   Fig 1.  shows a NECT Scan done on an old generation single source CT Scanner manufactured in 2008, at 120 kVp. The same patient CECT has done in a 2015 manufactured 3rd generation dual-source CT scanner, at 80 kVp

1.  Omit non-contrast CT scan if possible. For eg. Follow up in oncology patients.

2.  Limit the number of post-contrast run. For eg. Doing a single-phase CT scan during the venous Phase instead of multiphase studies. 

3. Limit the area of interest. For eg. In a renal stone protocol study, the liver need not be covered completely.        
                                                                              
4. Reduce peak kVP. If the patient weight is below 70 kg

  (Reduced resolution can be offset by increasing mAS if required)

   Fig 2.  shows a CECT Scan done on the same patient at two different kVp in different phases. The image on left is at 100 kV and the image on right is at 120 kVp. the reference mAs was not changed. There is approx. 40 % reduction in the radiation dosage. 

5.  Increase the reconstruction thickness (instead of scanning at 0.65 mm scan at 2.5 mm)

6.  Automatic Dose modulation (along the Z axis). A reference mAs is set and thereafter, based on the body size, the exposure keeps changing, as the body width/diameter changes. 

7.  Increase the pitch. For eg. Most of the scans it can be kept above 1. 

8.  Iterative reconstruction and noise reduction software available with current generation CT  scanners and a few third-party software. 

9. Some of the current generation scanners provide auto kV selection

10. Creating a virtual non-contrast CT scans on a dual energy scan. The iodine component is extracted from the contrast study. 

  Fig 3.  shows a CT Urography (iodine image) done on a dual source dual energy CT scanner (left) and the creation of a virtual non-contrast CT scan (right).

       
11. Dual-energy scan, can itself reduce the radiation dosage as compared to a standard CT Scan at 120 kVp. The two tube work at different kVp & mAs. The end product has a lower radiation dosage with mildly increased noise. 

     Fig 4

Prepared by

Dr. Sharad Maheshwari
11.08.2014

Updated: 02.01.2023