This document discusses the risks of low-level radiation exposure from medical imaging procedures like CT scans. It notes that while there is no scientific consensus on radiation risks, international organizations assume the linear no-threshold model which states that any increase in radiation dose, no matter how small, results in an incremental increase in risk. The document outlines strategies that radiologists can employ to optimize CT protocols and reduce radiation doses for patients, such as using automatic exposure control, iterative reconstruction techniques, indication-based protocols, and monitoring doses at the patient and department levels. Radiologists are urged to take the lead in minimizing radiation exposures from medical imaging when it is clinically appropriate.

1. Rathachai Kaewlai, MD
Division of Emergency Radiology, Department of Radiology
Ramathibodi Hospital, Mahidol University, Bangkok
RCRT 2015 at Centara Grand @CentralPlaza Ladprao

2. ! Lack of scientific consensus
! Assumption of risk from atomic bomb survivors
! How to act? Two possible errors…
! Assume risks are real and to then discover that
they do not exist
! Assume risks are nonexistent and to
subsequently discover that they are real
Huda W. Radiation risks: what is to be done? AJR 2015 January

3. ! Lack of scientific consensus
! Assumption of risk from atomic bomb survivors
! How to act? Two possible errors…
! Assume risks are real and to then discover that
they do not exist
! Assume risks are nonexistent and to
subsequently discover that they are real
Huda W. Radiation risks: what is to be done? AJR 2015 January

4. ! Low-level radiation
(up to 100 mSv)
! 30-40X annual natural
background
! 10X a usual CT scan
! Linear no-threshold
hypothesis
! 12 cancers with significant lifetime excessive
risks: lung, liver, breast, prostate, stomach, colon,
thyroid and leukemia
Committee on the Biological Effects of Ionizing radiation of the US National Academy of Sciences (2005)
Figure from web.princeton.edu

5. ! At low doses, the risk = one
excess cancer in 100
exposed persons (100 mSv)
during their lifetime. Mortality
is about one-half.
! Higher risk in female and
children
Committee on the Biological Effects of Ionizing radiation of the US National Academy of Sciences (2005)

6. ! “Most recent data for the
survivors of the atomic
bombings are largely
consistent with linear or
linear-quadratic dose trends
over a wide range of doses”
United Nations Scientific Committee on the Effects of Atomic Radiation (2006)

7. ! “….the practical system of
radiation protection
recommended by the
Commission will continue to be
based on the assumption that, at
doses below about 100 mSv, a
given increment in dose will
produce a directly proportionate
increment in the probability of
incurring cancer.”
International Commission on Radiological Protection (2007)

8. ! Do we agree on the risk of radiation?
! Do we agree on our role in it?
Radiologists’
professional role

9. Today: IMAGING 2.0 Tomorrow: IMAGING 3.0TM
Volume-based Value-based
Transactional Consultative
Radiologist centered Patient centered
Interpretation focused Outcomes focused
Commoditized Integral
Invisible Accountable
IMAGING 3.0TM is a trademark of the American College of Radiology

10. Today: IMAGING 2.0 Tomorrow: IMAGING 3.0TM
Volume-based Value-based
Transactional Consultative
Radiologist centered Patient centered
Interpretation focused Outcomes focused
Commoditized Integral
Invisible Accountable
IMAGING 3.0TM is a trademark of the American College of Radiology

11. IMAGING 3.0TM is a trademark of the American College of Radiology

12. Image © Alex Saurel on flickr
! Examination vetting
! Selecting appropriate protocol
! Optimize scanning protocols
! Mindset “lowest dose possible to achieve
diagnostic purposes”
! No more “good-looking images”
! Monitoring doses at level of patients,
divisions, groups, departments

13. ! Low-level radiation is a
health hazard – LNT
hypothesis
! Radiologists have a critical
role in optimizing CT
radiation exposure (should
be a leader of the team)

14. ! Why CT?
! CT parameters and radiation units
! Ramathibodi Emergency Radiology
experience
! Case examples (acute abdomen)
! Step-by-step guide to manage CT
radiation

15. ! Medical radiation is now the majority of
radiation exposure in human
! CT accounts for most of this
! CT volume on the rise
! No dose penalty in CT
! CT radiation dose is intrinsically high
! No binding regulations on CT doses
! CT radiation errors made into headlines

18. ! Case volume
! Many sensitive
organs
! Patient population
who gets scanned
! It’s frequently where
the Unnecessaries
occur
Brenner DJ, Hall EJ. N Engl J Med 2007

19. ! Assuming radiation risks are real
! Doing CT is weighing this risk with benefit
! If benefit > risk means a justified examination
! Providing other diagnostic options
! Using as low radiation as possible to
obtain needed diagnostic information
(ALARA)

20. Imaging exam ordered
by referring physician
Vetting/protocoling by
radiologist
Scanning
Post-processing
Monitoring of quality
Assetprotectionlawjournal.com
Massgeneralimaging.org
Medicineworld.orgJenkinsclinic.org
Blog.vpi-corp.com

21. " Educate physicians about radiation
risks
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

22. " Implement clinical prediction rules,
expert recommendation guidelines
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

23. " Import exams from outside hospitals
to PACS
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
! Patients transferred to trauma
center 38/137 (28%) received
duplicated scans in 24 hours
! Most common reason for
duplication = lack thin-
section data on CD (37%)
! Additional radiation 10.2 mSv
! Additional charge $409

24. Can we use radiation-free imaging
(US, MRI) instead of CT for this
clinical scenario?
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
Make ultrasound
(by radiologist) available
and easily accessible 24/7

25. Can we use radiation-free imaging
(US, MRI) instead of CT for this
clinical scenario?
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

26. If CT needed, design protocols
specific to answer questions
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

27. “Routine” protocol with minimum scanning
phases. Nonroutine done by add-ons
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

28. " Avoid Z-creep (unnecessary coverage
and scan phases)
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
! Radiation dose is directly
proportional to scan volume
! Kalra et al, Radiology 2004
! 106 abdomen/pelvic CTs
! 97% had extra images
! 12 extra images/CT

29. Make standard protocols available in CT
workstations for every techs to use
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
iacionline.com

30. " Reduce mAsCT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
! mA: effects
noise only
0
10
20
30
40
50
60
0 200 400 600
Changes in Dose (CTDIw) as a
Function of mAs
CTDIw Head (mGy) CTDIw Body (mGy)
Fixed kVp
Dose(mGy)
mAs

31. Use automatic tube current modulationCT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

32. " Reduce kVP
(esp for CTA,
stone protocol)
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
! Effect on both
noise and
attenuation
0
10
20
30
40
50
60
0 50 100 150
Changes in CTDIw as a Function
of kVp
CTDIw Head (mGy)
CTDIw Body (mGy)
Fixed mAs

33. Reduce kVPCT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

34. Reduce kVPCT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
120 kV, 300 mAs, 100 mL contrast
Aorta = 237 HU, noise = 13.1 HU
90 kV, 300 mAs, 80 mL contrast
Aorta = 334 HU, noise = 19.4 HU
Dose reduction of up to 57%
120 kV 90 kV
Nakayama Y, et al. Radiology 2005

35. Incorporate patient size, age and
indication into making a protocol (work
with your physicists)
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
! Image noise
increases with
less kVp but noise
is less in smaller
phantoms
Seigel MJ, et al. Radiology 2004

36. Incorporate patient
size, age and
indication into
making a protocol
(work with your
physicists)
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
Partnersradiology.org

37. CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
Use smooth kernels (algorithms)

38. CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
5 mm3 mm
View thicker slices

39. " Send “Dose Report” into PACSCT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

40. " Educate radiologists and trainees
about dose parameters and standards
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

41. " Regular updates of CT protocolsCT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
libraries.psu.edu

42. o Use decision support tools
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
Sanjay Saini, MD. MGH
Sistrom CL et al. Radiology 2009

43. Systemwide tackle of defensive medicine
and self referral
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
Texler.deviantart.com

44. Streamlined vetting and protocoling
processes
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
Claimruler.com
Managingamericans.com

45. CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring
Color zones:
- Pink = routine, R/O situation
- Green = F/U CT with one prior
- Red = bone evaluation or
multiple priors
- Yellow = kidney stone
- Blue = subtle or small lesions
suspected or identified with other
imaging
- Gray = vascular assessment
with CTA
kVp mA Noise Index
Singh S, et al. Radiology 2009

46. Use iterative
reconstruction
(IR)
CT order
Vetting/
protocoling
Scanning
Post-
processing
Monitoring

47. Take the lead
Decide to change
Form a team
Do it!
Monitor the results
It’s radiologists’ professional role.
Our job, nobody else…
o Tell technologists to send dose
report to PACS
o Check 10-20 reports of all organ
systems
o Compare your doses with
standard DRLs
o Convince your Superior/Head

48. Take the lead
Decide to change
Form a team
Do it!
Monitor the results
It’s radiologists’ professional role.
Our job, nobody else…
o Form a team (you + other
radiologists + techs + (physicist)
o Select the target exam type (high
doses, high volume)
o Invite referring physician to join
the team
o Set your goal

49. Take the lead
Decide to change
Form a team
Do it!
Monitor the results
It’s radiologists’ professional role.
Our job, nobody else…
o Clinical guidelines
o Technical parameters
o Scan coverage, phases
o Indication-based, size-based
protocols
o Additional techniques (IR)

50. Take the lead
Decide to change
Form a team
Do it!
Monitor the results
It’s radiologists’ professional role.
Our job, nobody else…
o Team monitoring of dose
o Repeat the processes

51. Exams CTDI vol per
phase (mGy)
DLP (mGycm)
Brain CT 75 1050
Chest CT 21 650
Upper abdomen CT 25 900
Lower abdomen CT 25 570
Whole abdomen CT 25 780
ACR/AAPM 2014
European Commission 2004

52. ! Estimated dose x conversion
factor = SSDE
! Closer to “real” dose
! Thinner patients get more dose
compared with obese patients
of the same DLP
! Based on our own unpublished
data, SSDE is 30%+ that of
estimated dose

53. ! New techniques for further dose reduction
MGH Radiology Rounds, mghradrounds.org

54. ! New techniques for further dose reduction
MGH Radiology Rounds, mghradrounds.org
120 kVp, FBP 100 kVp, advanced IR

55. ! 1- and sub-mSv scan
MGH Radiology Rounds, mghradrounds.org

56. ! It is not a “choice” to reduce CT radiation. As
a radiologist, it is a responsibility to our
patients
! No more best-looking images. Images
should be “enough for diagnostic purpose”
! Multiphase CT should not be “routine”.
! CT dose is manageable: take a lead, make
a decision, form a team and “just do it”.