Purpose: We created a CT protocol creation procedure. It ensures the protocol should not hit tube limits over the range of patients it is designed for.
Methods: Our protocol creation procedure: (1) Input scanner specific tube limits, kV, pitch, rotation time, and collimation (2) using your reference manual or measurements, calculate the minimum and maximum CTDIvol (3) determine the indication specific minimum and maximum AP+Lat of patients corresponding to this dose range (4) determine the maximum scan length (5) calculate the scan duration. We provide tables of CTDIvol and scan length as a function of patient size using 210 pediatric abdomen exams (newborn-18 years). From these cases, we determined kV, rotation time, pitch, mAs, AP+Lat patient dimensions, scan length, and CTDIvol per slice. The data did not have tube limit constraint issues and each case was radiologist validated. We used this data to connect CTDIvol needs with patient size. We also discuss how to alter the provided data if your institution has different image quality and or dose requirements. We apply our method to two different scanners and acquisition parameter option sets.
Results: A dual-source: 70kV, 0.25s rotation time, 3.2 pitch protocol allowed for a maximum dose corresponding to 345mm AP+Lat (i.e. 2 y.o.) and a scan length of 348 mm in 0.47 s. A single tube: 80kV, 0.4s rotation time, 1.375 pitch protocol allowed for a maximum dose corresponding to a 426mm AP+Lat (i.e. 12 y.o.) and a scan length of 411mm in 3.0 s.
Conclusion: We present a physics framework for ensuring proper image quality via: 1. ensuring proper AEC function and 2. providing accurate scan duration information so clinical decisions can be made related to breath holds and contrast administration.
Funding Support, Disclosures, and Conflict of Interest: TPS supplies CT protocols to GE Healthcare under a licensing agreement. TPS is also a consultant for GE and iMALOGIX and is on the CAB of iMALOGIX. He is also the founder of protocolshare.org.
Not Applicable / None Entered.