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State of MichiganComputed Tomography Regulations
Don Parry, CHP
Radiation Safety Section
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:www.michigan.gov/rss
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
Patient dose from CT was 3 % of all medical exposure in 1980s
It increased to 49% in 2006
CT is 17% of the studies, but contributes to 49% of patient dose
II. Recent Medical Errors
Topics of the New CT Rules
Medical Physicist RequirementsCT Operator RequirementsConditions of OperationEnclosuresReport and notification of a CT medical events
Quality control program
Rule 705 – CT OperatorsInitial 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).
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.
Rule 705 – CT OperatorsContinuing 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.
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.
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.
Notification Values
Computed Tomography Dose Index (CTDI)
CT Dosimetry Phantoms
Dose Indices CTDI100 -CTDI with integration limits of +/- 50
mm CTDI w = (1/3 CTDI100 )center + (2/3
CTDI100 )periphery
CTDI vol = CTDIw / Pitch
Dose Length Product
Dose Length Product
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
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.
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.
Good example
Bad example
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
Alert Values
Alert Threshold - CTDIvol = 1 Gy (half skin injury dose) - FDA suggested
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.
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.
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.
FAQsQuestion 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?
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.
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?
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.
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
Quiz Q3:The displayed CTDIvol for a pediatric
abdomen was 15 mGy using a pitch of 1.0. 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
QUESTIONS? Contact Information
Donald E. Parry, MHP, CHPRegion Physicist-Radiation Safety SectionMIOSHAPhone: 517-636-6797e-mail: [email protected]
