1. State of Michigan Computed Tomography Regulations
Radiation Safety Section
State of Michigan Computed Tomography Regulations
Intro, background, explain that presentation is informal, was put together quickly, feel free to ask questions as I go
Don Parry, CHP

2. Radiation Safety Section
Scope of Authority – Regulates use of machine produced ionizing radiation.
Ionizing Radiation Rules of the State of Michigan
Part 15. Computed Tomography Installations
Effective June 8, 2011
Rules, Guidance Document, and FAQs available at:
Explain that the state only regulates machine produce Ionizing Radiation; other states are agreement states,
We are going to discuss the requirements in Part 15 of the Ionizing radiation rules

3. Why all of the regulatory scrutiny of Computed Tomography?
Two things have contributed to the increased attention to CT.
1. The utilization of computed tomography has increased over the years
II. Publication of Recent CT Medical Events
A common question is all of this attention given to computed tomography. (Review slide)

4. Patient dose from CT was 3 % of all medical exposure in 1980s
When I started in the 80s, most patient dose was delivered by conventional rad fluoro. Only 3% was from CT

5. It increased to 49% in 2006
The increase was due to better detectors, better computing power and more robust x-ray tubes.
(Review slide)

6. CT is 17% of the studies, but contributes to 49% of patient dose
It isn’t that CT is done more often than R/F, but it is a higher dose procedure. It is less than 1/5 of the studies but contributes ~ half the dose.

7. II. Recent Medical Errors
Starting around 2009, there were several news stories where people were injured by overdoses from CT.
These were mostly from brain perfusion studies. Unclear whether Rad, tech or manufacturer modified technique to create better image. Dose not well monitored or understood. In the past it was impossible to get non stochastic effects from diagnostic imaging.

8. Topics of the New CT Rules
Medical Physicist Requirements
CT Operator Requirements
Conditions of Operation
Enclosures
Report and notification of a CT medical events
Quality control program
New CT rules were in general based on the ACR CT requirements. I tried to pick out the sections that are the most applicable to the operators.
Guidance on the entire rule set is available on our website.

9. Rule 705 – CT Operators
Initial qualifications. Before beginning to perform CT examinations independently, a technologist shall meet both of the following:
Be currently registered by the American registry of radiologic technologists (ARRT) or by the Canadian association of medical radiation technologists (CAMRT). 
Review slide

10. Rule 705 – CT Operators
Document at least 20 hours of training and experience in operating CT equipment, radiation physics, and radiation protection or have the advanced certification in computed tomography from the ARRT.
we suggest at least 10 hours be didactic training.

11. Rule 705 – CT Operators
Continuing education. A technologist shall be in compliance with the ARRT requirements for continuing education for the imaging modality in which he or she performs services. The continuing education shall include credits pertinent to CT.
– Must keep up your ARRT, some CEU have to be in CT (we say 2)

12. Rule 713 – Conditions of Operation
(1) Six months after the effective date of these rules, the CT facility shall establish scanning protocols in consultation with a medical physicist.
largest change was probably the requirement for protocol reviews.

13. Rule 713 – Conditions of Operation
(2) The CT operator shall check the display panel before and after performing each scan to make sure the amount of radiation delivered is appropriate for the technique and individual patient. This may be accomplished by reviewing dose indicator devices if available or dose indices such as the technique factors. Dose indicators or indices outside of expected values shall be documented and reviewed by an interpreting physician or medical physicist.
MP should give techs some idea about when a dose is too high. Rule came from the perfusion studies where tech should have noticed CTDIwas very high

14. AAPM provides physicist with some default values, but facility MP can suggest their own – point out that some of the brain perfusion studies that caused harm will well over 2000 mGy

15. Notification Values
New scanners have software that monitors this, these are called notification values. There could be good reasons you need more… such as large patient size.

16. Computed Tomography Dose Index (CTDI)
What is CTDI…. (Explain till their eyes glaze over)

17. CT Dosimetry Phantoms
. We measure with two standard phantoms and an ion chamber

18. Dose Indices CTDI100 -CTDI with integration limits of +/- 50 mm
CTDI w = (1/3 CTDI100 )center + (2/3 CTDI100 )periphery
CTDI vol = CTDIw / Pitch
Explain capturing all of the tails… how CTDI 100 uses 100 mm probe, how CTDI weighted is calculated, and finally adjusted by the Pitch to get CTDI volume reported by scanner

19. Dose Length Product
Scanners often report the CTDI (think of as tube output… doesn’t change with scan length) and

20. Dose Length Product
DLP… more length more DLP… more proportional to actual risk

21. ACR CTDI Reference Values
CTDIvol is NOT patient dose
CTDIvol is reported in units of mGy for either a 16-cm (for head exams) or 32-cm (for body exams) diameter acrylic phantom
For the same technique settings, the CTDIvol reported for the 16-cm phantom is about twice that of the 32-cm phantom
ACR has reference values. Pay particular attention to CTDI reported for ped body. Some scanners assume the 32 cm phantom for all body… (go back to picture of phantom) ask them to guess what happens if I measure ped dose in small phantom versus big phantom. Which is higher?

22. Rule 713 – Conditions of Operation
(6) Only individuals whose presence is necessary are allowed in a fixed CT scanner room during exposure. Each individual, except the patient, shall be protected by at least a 0.5 millimeter lead equivalent apron or a whole body protective barrier.

23. Rule 711(4) Enclosures
The control panel for a fixed CT scanner shall be shielded by a protective barrier that cannot be removed from a protective position between the operator and the radiation source during machine operation.
Don’t be in the room unless you have to.. then wear apron

24. Good example
You have to have an operator’s barrier that is fixed (discuss diagrams 24,25 and picture 26)

25. Bad example
You have to have an operator’s barrier that is fixed (discuss diagrams 24,25 and picture 26)

26. You have to have an operator’s barrier that is fixed (discuss diagrams 24,25 and picture 26)

27. Rule 715 Report and notification of a CT medical event
Rule 715. (1) A CT facility shall report any CT medical event.
Facilities now need to report to State and patient when deterministic effects occur
(c) “CT medical event” means an unintended event where a physician determines that actual damage has occurred to an organ or a physiological system of an individual due to or suspected to be due to exposure to diagnostic radiation from a CT scanner

28. Alert Values Alert Threshold - CTDIvol = 1 Gy (half skin injury dose)
scanners have software that warn operator when it is set at about half that value. Called Alert levels.. (usually at 1 Gy (100 rads)
Alert Threshold
- CTDIvol = 1 Gy (half skin injury dose)
- FDA suggested

29. Rule 717 Quality control program
(2) Evaluations and tests shall be performed following written procedures and methods. Corrective action shall be taken and documented according to instructions provided by the medical physicist if the results of an evaluation or test fall outside the control limits.
Need to have and follow written QC procedures. Also need to take corrective action for failures.

30. The ACR has suggested procedures

31. Example of Corrective Action
If either the mean CT number or the noise (standard deviation) is not within the criteria limit for 3 days in a row or 3 times within a 7-day period, corrective action should be taken by reporting the problem to service representatives.
– Corrective action can be set by the MP, but must be followed and documented.

32. Rule 717 Quality control program
(3)…. An on-site CT radiologic technologist shall be identified to be responsible for the ongoing quality control testing. The tests shall be performed by this technologist or by other personnel qualified by training and experience following written procedures and methods under subrule(2) of this rule.
There is a requirement for an on-site QC technologist that makes sure QC is performed and documented

33. FAQs
Question 8: To become certified with the ARRT in Radiography, the radiography education program I completed included training in radiation physics and radiation protection. Will this training cover the radiation physics and radiation protection portion of the required 20 hours of training?
Slide 33 – 36 Go over FAQs

34. FAQs
If you are ARRT registered in Radiography, ARRT(R), and do not have the advanced certificate in CT, we will assume that you have had training in radiation physics and radiation protection but you will still need to document 20 hours of training and experience in operating CT equipment.
Slide 33 – 36 Go over FAQs

35. FAQs
Question 9: We use a team of two technologists to perform CT scans. Do both technologists need to be qualified under the CT rules?
Slide 33 – 36 Go over FAQs

36. FAQs
No. Only one technologist needs to be qualified. If a team approach is used where only one operator meets the qualifications under the rules, the qualified operator must be in the CT room during the examination. This is to provide reasonable assurance that any mistakes made by any technologist who does not meet the qualification requirements are corrected before patients are irradiated or harm is done to the patient.
Slide 33 – 36 Go over FAQs

37. Quiz
Q1:What percentage of medical exposures were from computed tomography in 2006?
A: 49%
Q2:A patient undergoes a CT scan at a technique of 120 mAs, pitch of 0.7 and 120 kVp for a scan length of 10 cm and the patient dose is 10 mGy. What is the dose for a 20 cm scan length at the same technique?
A: 10 mGy

38. Quiz
Q3:The displayed CTDIvol for a pediatric abdomen was 15 mGy using a pitch of What would the CTDIvol be at a pitch of 1.5?
A: 10 mGy
The displayed CTDIvol for a pediatric abdomen was 5 mGy for a 32 cm phantom. Approx. what would it be for the 16 cm phantom used to set reference levels by the ACR?
A: ~10 mGy

39. QUESTIONS?
Contact Information
Donald E. Parry, MHP, CHP
Region Physicist-Radiation Safety Section
MIOSHA
Phone: