Which scanner: GE CT750 or the Siemens Flash?
The following question has been sent by John Phillips:
Which scanner: Which is the more advanced and best all around scanner….the GE CT750 or the Siemens Flash? If you could only buy one as your only scanner which would you buy? Are there any “must have” options?
Savvas Nicolaou, MD, Vancouver General Hospital, University of British Columbia:
Both are great scanners however overall I would purchase the Siemens Flash scanner because of its great versatility. It allows you many more options on scanning many different types of clinical scenarios.
Cardiac: The Flash scanner allows you to scan with and without b blockers given the 75 msec temporal resolution that can be advantageous in patients that you cannot use b blockers ie asthmatics, COPD, extremely high heart rates.
You have the possibility in scanning prospectively without b blockers thus lowering the dose, you can scan in Flash mode if the heart rate is below 65 beats per minute at doses less than 1 msv
You still can scan spiral for unpredictable heart rates
You also now have the possibility in doing perfusion dynamically or utilizing dual energy for assessing ischemia
You can do a Flash triple rule out around 4 to 5 msv where most scanners require 15 to 20 msv
Thorax: You can dual energy imaging for pulmonary embolism assessing for perfusion defects, or you can sue the flash mode that allows you to also visualize the coronary arteries at the same time and limits motion that is useful for critical ill patients that cannot hold there breaths, this mode is also useful for pediatric patients as you do not need to use sedation to limit motion. By using dual energy you can better see aortic leaks for aortic stent graft assessment given the increased sensitivity at the 80 or 100 kv setting in dual energy mode.
Neuro: You can do whole brain perfusion under 5 msv
You can do dual energy imaging that allows you to quickly subtract the bones from the vessels allowing you to expedite your workflow in CTA’s of the head and neck and also this is very useful for arteries that have lots of calcified plaques as it allows you to subtract the calcium from the vessel wall.
Vascular: you quickly do whole body run offs in a matter of seconds with dual energy that allows you to see distal calcified vessels more clearly due to the pure bone vessel subtraction
Abdomen: You can use dual energy to better assess renal , liver pancreatic lesions and you can save dose from the virtual non contrast scan as you do not need a seperate non contrast scan. You can use dual energy to characterize renal stones separate uric acid from calcium stones.
MSK: You can use dual energy to asses for gout arthropathy also can use the Z sharp ultra high resolution mode to better analyze the bony anatomy at a resolution of 0.24 mm.
Bariatric patients: given the 100 kwatts dual generators and dual tubes you can increase your photon flux to obtain high quality images in these type of patients.
DOSE: Dose is always an issue you have 4D care dose to modulate the tube current adaptive collimation to decrease the dose form spiral scans, but you can also use X care dose to limit the amount of radiation anteriorly particularly to the breast and thyroid tissue. And now you have IRIS that can save dose up to 40 percent.
I think based on all of these advantages that have been tested clinically, the Flash scanner is the most versatile scanner on the market at the present time.
thank you
Dr Savvas Nicolaou






Some colleagues and I have actually just concluded a study on a Siemens SOMATOM Definition Flash scanner with our focus being the possible advantages of using the X-Care function and we found that with X-Care being a kind of x/y mA-modulation, it is not possible to run CareDose x/y-modulation simultaneously, which ends up increasing the dose (CTDI) by an average of 30%. I do agree with everything else being stated about the scanner in this reply though.
Regards
Ali F. Corap
If X-CARE is used, CARE Dose 4D is modulating along the z-axis of the object only. However this does not mean that X-CARE increases dose compared to the x/y profile of the tube current.
By adjusting the Q.ref.mAs in your x-CARE protocol to a level that the eff.mAs of this protocol correspond to the reference level of your non X-CARE protocol, you can make sure that your X-CARE protocols are consistently CTDIvol neutral. While decreasing direct surface entrant exposure anteriorly.
Please let me know the best protocol of coronary CTA using DSCT Flash mode when bolus tracking method is preferred. How long is the duration should we keep above the expected CT value of contrast? We are certain to install Somatom Definition Flash in this April.
On Our FLASH coronary protocols we do not use bolus tracking, but test bolus.
We use 20cc of Isovue 370 at 6 cc/sec for the test injection at the ascending aorta.
For the main bolus we use 60 cc of Isovue 370, followed by 55cc of a 40/60 split of Isovue/saline followed by 40cc of saline, all at 6cc/sec.
For timing of the bolus, we add 5 sec to the peak injection time at the ascending aorta.
This summer I concluded on yet another paper on X-Care finally showing that X-Care is not recommendable for use in regards to the ALARA principle. By modifying your Q.ref.mAs you might end up with an equally low mAs but due to the lack of proper x/y-modulation your signal will be unevenly distributed in the x/y plane resulting in an overall increase in noise at the same dose level.
Our findings still show an average dose increase of 30% to the entire scan field and up to a staggering 50% increase for the red bone marrow in the spinal column while maintaining the same noise level for p<0.05.
Thank you for your question
Based on our own research presented at the RSNA 2011 in and other papers listed below, in our hands at our institution performed with our physicist, we achieved a reduction in dose to the lenz anteriorly close to 40 percent while still maintaining good image quality and did not observe an increase in dose overall .
I have listed some of the papers
sincerely Dr Savvas Nicolaou
1. Dose Reduction to Anterior Surfaces With Organ-Based Tube- Current Modulation: Evaluation of Performance in a Phantom Study
Xinhui Duan1
Jia Wang1
Jodie A. Christner1 Shuai Leng1
Katharine L. Grant2 Cynthia H. McCollough1
AJR:197, September 2011
2. Bismuth Shielding, Organ Based TCM , and global reduction of tube current for dose reduction to the eye at Head CT.
Jia Wang
Xinhui Duan
Jodie A. Christner1 Shuai Leng1
Katharine L. Grant2 Cynthia H. McCollough1
Radiology january 2012 vol 262 number 1