Recommended Reading about Dual Source CT and reducing radiation exposure
The following question has been sent by Patrick, CT Tech:
Our facilty is currently operating a siemens Definition Scanner. I was hoping you could recommend some reading material on Dual Source CT. Also some info on how to reduce radiation exposure.
Ralf Bauer, MD, Clinic of the Goethe University, Frankfurt, Germany:
Dear Definition user,
there is acutally not much literature on dual source ct in general.
There are a lot of published scientific papers on DCST of the heart (search www.pubmed.org for that). There is further a book on MDCT and DSCT cardiac imaging edited by Bernd Ohnesorge (Springer). Further, there is a short guideline to DSCT and dual energy CT edited by Peter Seidensticker. Usually the latter book comes with the purchase of a Siemens Dual Source Scanner. It contains plenty of protocol suggestions for dual source, single source, and dual energy mode. The protocols recommended there are robust, but very basic. If you don´t have that book, ask Siemens, if they would provide it.
In terms of dose reduction: this a very wide field and very complex to answer. Do you have a special field of interest? Lung? Abdomen? Cardiac?
In general, I recommend using CAREdose 4D for all except head scans.
Some radiologists also like to turn caredose off for imaging extremities (fractures, deformations etc). This may appear very simple for you, if you are already familiar with that technique. However, I know, that even in 2010 the routine use of online tube current modulation is not standard in every facility.
For lung scans, reducing tube potential from 120 to 100 kV is a good way to reduce dose. However, if the patient exceeds 85-90 kg, you may find images too noisy and go with 120 kV. In the same fashion, you may try to stick with 120 kV and reduce mAs from the default 110 mAs down to 50 mAs or less and increase pitch to 1.5, if you do follow-up scans of pneumonia or the like.
For abdominal: if you do multiphase scans like for liver or kidney imaging, you may lower tube current in the native phase down to 180 mAs or the like. For contrast-enhanced phases, especially venous phase, you may want to stick with 240-260 mAs for better deliniation of pathologies.
Cardiac: even if Siemens advertises the scanner with the slogan “no betablocker required”, I highly recommend the use of betablockers when ever possible. I try to lower the heart rate in every patient down to 65 bpm or less (the lower the better!). If you can generate a slow and regular heart beat, you can choose the adaptive sequence scan mode, which is a prospectively triggered scan mode. This will allow for huge dose savings. However, with adaptive sequence, you won´t get any functional information, as you limit image aquisition to a very small window during enddiastole. If you wanna stick with the spiral mode: try to lower kV from 120 to 100 in slim patients, increase tube current from 320 to 370 mAs.
I hope, I could help you a little bit! However, if you wanna come up with more detailed questions, feel free to ask!
Regards,
Dr. Ralf Bauer
