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State of Michigan Computed Tomography Regulations Don Parry, CHP Radiation Safety Section.

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Presentation on theme: "State of Michigan Computed Tomography Regulations Don Parry, CHP Radiation Safety Section."— Presentation transcript:

1 State of Michigan Computed Tomography Regulations Don Parry, CHP Radiation Safety Section

2  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:

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

4 Patient dose from CT was 3 % of all medical exposure in 1980s

5 It increased to 49% in 2006

6 CT is 17% of the studies, but contributes to 49% of patient dose

7 II. Recent Medical Errors

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

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).

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.

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.

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.

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.


15 Notification Values

16 Computed Tomography Dose Index (CTDI)

17 CT Dosimetry Phantoms

18 Dose Indices  CTDI 100 -CTDI with integration limits of +/- 50 mm  CTDI w = (1/3 CTDI 100 ) center + (2/3 CTDI 100 )periphery  CTDI vol = CTDI w / Pitch

19 Dose Length Product


21 ACR CTDI Reference Values  CTDI vol is NOT patient dose  CTDI vol 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 CTDI vol reported for the 16-cm phantom is about twice that of the 32-cm phantom

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.

24 Good example

25 Bad example


27 Rule 715 Report and notification of a CT medical event  Rule 715. (1) A CT facility shall report any CT medical event. (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 - CTDI vol = 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.


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.

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. 

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?

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.

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?

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.

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 CTDI vol for a pediatric abdomen was 15 mGy using a pitch of 1.0. What would the CTDI vol be at a pitch of 1.5?  A: 10 mGy  The displayed CTDI vol 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: 517-636-6797 e-mail:

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