1. Dose Reduction with
SAFIRE
Scott Plowman
CT Supervisor,
Knox Private Hospital

2. Knox Private Hospital
• 350 bed private hospital
• outer eastern suburbs of Melbourne
• A&E, ICU, CCU, Midwifery, surgical etc

3. Our Department
• MRI, DR, CR, US, Fluoro, CT
• Siemens Definition AS 128
o 18months old, coming from GE Lightspeed Plus
(64slice).
o ~40 scans per day. Most during 9-5.
o casemix: 33% Outpatients, 33% A&E, 33% Inpatients
o All facets of CT- incl. high end vascular, cardiac,
intervention, oncology, etc
o Syngo Via

4. • At Knox we try to be a very low dose site
• ARPANSA DRL Survey:
 Brain DLP = 1000mGy.cm Knox = 660mGy.cm
 Chest DLP = 450mGy.cm Knox = 297mGy.cm
 AbdoPel DLP = 700mGy.cm Knox = 526mGy.cm
 LSV DLP = 900mGy.cm Knox = 500mGy.cm

5. • How do we achieve low dose:
 All the usual principles
• Limit to area required
• Low kV where possible
• CAREDose 4D
• SAFIRE
 Others:
• Bismuth breast and eye shields

8. Filtered Back Projection
• Been used for CT images since its inception.
• multiple projectrions run though a filter
• assumes a perfect scanner/system/physics
• fast, less computer intensive
• This type of image is what doctors are used
to looking at

9. Iterative Reconstruction
• has been used in NM for ~10yrs but due to
the processing power required it has not
been used in CT
• IRIS/SAFIRE, ASIR/VEO, iDose, AIDR
• FBP- higher spatial resolution --> higher
image noise
• IR allows decoupling of these 2 parameters
o correction loop introduced to decrease image noise

10. •
• Potential for:
o Noise reduction
o Artefact reduction
o Increased spatial resolution
• Downsides:
o Huge computational cost: ?practicality
o Non-linearity

11. IRIS
• Image Reconstruction in Image Space - 2009
• Incorporates a "correction loop" in the
image domain to correct for the noise (3-5
iterations)
• All iteration done in image space
• "30% Less noise c.f. FBP"
• Images look different, "plasticky"
• Radiologists aren't used to looking at this
type of image

12. IRIS (cont.)
• Benefits:
o lower radiation dose required to produce similar
image to LFBP
o less noise in images
• more noise reduction in sharper kernel
• effect greater at large DFOV
o Enhance spatial resolution in areas of high contrast
• Disadvantages
o time consuming reconstruction
o "plasticky" images

13. SAFIRE
• Sinogram Affirmed Iterative Reconstruction
- 2010
• ALSO u ses the raw data during its iteration
loop
• Potential for artefact reduction
• Gives us the option of 5 strengths of
iterative reconstruction

14. SAFIRE (cont.)
• advantages:
o even lower radiation dose required to produce
similar image to LFBP
o less noise in images
• more noise reduction in sharper kernel
• effect greater at large DFOV
• less noise for higher SAFIRE strength
• achieved without loss of spatial resolution

15. Uses
• Basically everything except most lungs and
some bone recons
o All abdomens - ST axials, axial fines, and coronals
performed using 4D workstream
o Chest - ST axials, axial fines, HRCT
o Brain - everything
o Sinuses - everything (lower dose)
o Spines - all ST recons
o Extremities - fine recons- eg. wrist, feet, hands

16. 80Kv
H41
9.8
J40_S1
8.1 J40_S3
6.6
J40_S5
5.2

17. 100kv
H41
6.9
J40_S1
5.8
J40_S3
4.7
J40_S5
3.7

18. 140kv
H41
4.4
J40_S1
3.7
J40_S3
3.0
J40_S5
2.4

19. H70
86.3
J70_S1
74.5
J70_S3
52.0
J70_S5
23.6

20. • Medium kernel: from H41 J41S3 = ~32%
noise reduction
• Medium kernel: from H41  J41S5 = ~45%
noise reduction
• Sharp kernel: from H70  J70S3 = 40% noise
reduction
• Sharp kernel: from H70  J70S5 = 73% noise
reduction

21. H40

22. H40

30. So what to apply SAFIRE to?
• Anything you want
• We apply it to everything except thick lung
axials
• What strength?
o Whatever your radiologist(s) are happy with
o SAFIRE “look” does take a while to get used to
o Higher the strength, the lower the radiation dose
required

31. What SAFIRE has meant to us
• Better quality images at a lower dose (30%)