Varying mAs in Relation to Patient Habitus to Maintain CT Image Quality
Hybrid cameras are becoming commonplace in Nuclear Medicine. Since the first installation of the PET/CT camera, the CT component has increasingly become a standard accessory to new PET and gamma cameras.
The Centre for PET at Austin Health operates the CT scanner in a non-diagnostic mode with a default tube current of 30 milliamperes (mAs). The CT scan is primarily used for attenuation correction and image fusion purposes.
It is widely known that the low dose CT scan provides critical information to the FDG-PET scan and has allowed the physician to confidently localise FDG avid lesions, but at what point does the low dose CT of 30mAs become ineffective due to the patient’s size or positioning of their arms due to CT attenuation artifacts?
We have investigated the use of varying mAs (30, 50 & 100 mAs) with consideration of the patient’s size and the position of the patient’s arms - up or by their sides.
Our results suggest that an increase in mAs for large patients and for patients scanned with their arms by sides, the quality of the CT is improved, maintaining its effectiveness for anatomical correlation and warrants the increased radiation exposure to the patient.