Section R12-1-612. Computed Tomography Systems

A.      Definitions:

1.        “CT” means computed tomography.

2.        “CT conditions of operation” means all selectable param- eters governing the operation of a CT including nominal tomographic section thickness, and technique factors.

3.        “CTDI” means computed tomography dose index, the integral of the dose profile along a line perpendicular to the tomographic plane divided by the product of the nom- inal tomographic thickness and the number of tomogram produced in a single scan.

4.        “CTDI vol” means a value of a volume-weighted tomog- raphy dose index. The unit of the CTDI vol is Gray or

subunits of the Gray. The value of the CTDI vol for patient scan is used to trigger a notification when the value exceeds or will exceed a threshold value.

5.        “CTN” means CT number, the number used to represent the x-ray attenuation associated with each elemental area of the CT image.

6.        “Dose profile” means the dose as a function of position along a line.

7.        “DLP” means the dose-length product. The DLP is the mathematical product of the CTDI vol and the length of the scan. The unit DLP is the Gray-cm of subunits of the Gray-cm. The DLP is used to trigger a notification when the value exceeds or will exceed a threshold value.

8.        “Elemental area” means the smallest area within a tomo- gram for which the x-ray attenuation properties of a body are depicted.

9.        “Multiple tomogram system” means a CT system that obtains x-ray transmissions data simultaneously during a single scan to produce more than one tomogram.

10.     “Nominal tomographic section thickness” means the full width at half-maximum of the sensitivity profile taken at the center of the cross section volume over which x-ray transmission data are collected.

11.     “Reference plane” means a plane that is displaced from and parallel to the tomographic plane.

12.     “Scan” means the complete process of collecting x-ray transmission data for the production of a tomogram. Data can be collected simultaneously during a single scan for the production of one or more tomograms.

B.       Facility: A registrant shall ensure that a CT facility has:

1.        An operable two-way communication system between the patient and the operator in each CT room.

2.        A viewing system that will allow the operator to continu- ously view the patient from the control panel during each examination. If the viewing system malfunctions the CT shall not be used until the viewing system is repaired.

C.      Equipment. A registrant shall ensure that:

1.        There is a means to terminate x-ray exposure automati- cally in the event of equipment failure by:

a.         De-energizing the x-ray source, or

b.        Shuttering the x-ray beam.

2.        The equipment shall provide the operator the ability to terminate the x-ray exposure at any time during the exam- ination, provided the scan or series of scans is greater than one-half second duration.

a.         If an operator terminates an x-ray exposure, the operator shall reset the CT conditions of operation before the initiation of another scan.

b.        A visible signal shall indicate when an x-ray expo- sure has been terminated because of equipment fail- ure.

3.        A means is provided to permit visual determination of the tomographic plane for a single tomogram system, or the location of a reference plane offset from a single tomo- graph or multiple tomogram system.

a.         If a light source is used to satisfy this requirement, it shall provide illumination of the tomographic plane or reference plane under ambient light conditions.

b.        The difference between the actual plane location and the indicated location of a tomographic plane or ref- erence plane shall not exceed 5 millimeters.

c.         The deviation of indicated scan increment versus actual increment shall not exceed plus or minus 1 millimeter with any mass from 0 to 100 kilograms resting on the patient support device.

4.        The control panel and gantry provides a visual indication, if x-rays are produced.

5.        Emergency buttons and switches are marked by function.

6.        Parameters of CT operation used during a patient exam- ination are visible to the operator upon initiation of the scan. If an operational parameter is not adjustable by the operator, this subsection may be met by indicating on the control panel the parameter is not adjustable by the opera- tor.

7.        Radiation exposure does not exceed 100 mR in one hour at one meter in any direction from the tube port of an operating CT.

8.        The angular position or positions where the maximum surface CTDI occurs is identified to allow for reproduc- ible positioning of a CT dosimetry phantom, except in those cases where the x-ray tubes are designed to move, in which case, the maximum dose and associated tube position shall be evaluated according to manufacturer recommendations.

D.      Operating Procedures. A registrant shall ensure that:

1.        Operating procedures are available at the control panel, or by electronic means, regarding the operation of a CT and evaluation of a CT’s operation.

2.        The operating procedures contain the following informa- tion:

a.         A copy of the latest evaluation of the CT’s opera- tion, to include output for each CT procedure, per- formed by a qualified expert;

b.        Instructions on the use of the CT performance phan- tom by the qualified expert, a schedule of quality control tests with the results of the most recent qual- ity control test, and the allowable variations for the indicated parameters;

c.         The distance in millimeters between the tomo- graphic plane and the reference plane if a reference plane is used; and

d.        A current technique chart that contains the informa- tion required in R12-1-607(D)(4)(a) for both adult and pediatric patients, as applicable, is available at the CT operating console, and a procedure for deter- mining whether a CT has been performed according to instructions of a physician.

e.         A written or electronic log that contains the informa- tion required in R12-1-607(D)(5) as well as an entry in the record of any displayed values for the exam from either a CTDI vol or DLP measurement for each patient exam completed on equipment manu- factured on or after January 1, 2011.

3.        If the evaluation of the CT’s operation or quality control test identifies a parameter exceeding the tolerance estab- lished by a qualified expert, the use of a CT for patient examination is limited to those uses established in written instructions from the qualified expert.

E.       Quality control tests. A registrant shall have a written quality control test procedure, developed by a qualified expert, and ensure that the quality control test procedure:

1.        Incorporates the use of a CT performance phantom that is compatible with an approved accreditation program approved by the Medicare Improvements for Patients and Providers Act (MIPPA) or supplied by or approved for use by the manufacturer of the unit.

2.        Is followed in the evaluation of the CT's operation, that the interval between tests does not exceed those set forth in the application for accreditation or quarterly if not accredited by an organization approved by (MIPPA), and

that system conditions are specified by the registrant's qualified expert.

3.        Includes obtaining quality control test images with the CT performance phantom using the same processing mode and CT conditions of operation that are used to per- form the evaluation of the CT’s operation.

4.        Requires that images obtained under subsection (E)(3) be retained until a new evaluation of the CT’s operation is performed.

5.        Requires that any Alerts and Notification settings using CTDI vol or DLP are reviewed against preloaded tech- niques in the system and any missing fields are reviewed with the staff radiologist and noted in the annual report.

6.        Requires the quality control test procedure and records of quality control tests performed be maintained for three years for Agency inspection.

F.       Evaluation of a CT’s operation. A registrant shall ensure that:

1.        The evaluation of a CT’s operation is performed by, or under the direct supervision of, a qualified expert who is physically present at the facility during the evaluation of the CT’s operation.

2.        The evaluation of a CT’s operation:

a.         Is performed before initial patient use and annually (within two months of the annual due date) and after any change or replacement of components that could, in the opinion of the qualified expert, cause a change in radiation output; and

b.        Shall measure the CTDI in a dosimetry phantom along the two axes specified in subsection (F)(4)(b).

c.         A complete evaluation of a CT unit, performed before the annual due date shall clearly list if the new survey changes the annual due date for the unit. It shall be clearly noted on all documentation for the next three years that the survey has established a new annual due date based upon the date of the new survey.

3.        The evaluation of a CT’s x-ray system is performed with a calibrated dosimetry system that:

a.         Has been calibrated using a method that is traceable to the National Institute of Standards and Technol- ogy (NIST), and

b.        Has been calibrated within the preceding two years.

4.        CT dosimetry phantoms used in determining radiation output are  compatible with an approved accreditation program approved by (MIPPA) or supplied by or approved for use by the manufacturer of the unit; and

a.         Are constructed in a way that the parameters used to image the most commonly imaged parts of the human body are evaluated; and

b.        At a minimum, provide means for placement of a dosimeter along the axis of rotation and along a line parallel to the axis of rotation 1.0 centimeter from the outer surface and within the phantom.

5.        Any effects on the measured dose due to the removal of phantom material to accommodate the dosimeter are accounted for in the reported data or included in the state- ment of maximum deviation for the measured values.

G.      CT units designated for simulator use, veterinary use, dental use, podiatry use, and non-diagnostic use on humans are exempt from the annual requirements in subsections (E) and

(F)    provided an initial evaluation is conducted by a qualified expert and the output does not exceed the manufacturers spec- ified limits.  The  initial evaluation  shall be maintained  for Agency review.

Historical Note

Adopted effective June 30, 1977 (Supp. 77-3). Former

Section R12-1-612 repealed, new Section R12-1-612 adopted effective August 8, 1986 (Supp. 86-4). Amended

effective January 2, 1996 (Supp. 96-1). Amended by final

rulemaking at 5 A.A.R.1817, effective May 12, 1999 (Supp. 99-2). Amended by final rulemaking at 7 A.A.R. 2584, effective June 8, 2001 (Supp. 01-2). Amended by

final rulemaking at 10 A.A.R. 2122, effective July 3,

2004 (Supp. 04-2). Amended by final rulemaking at 15

A.A.R. 1023, effective August 1, 2009 (Supp. 09-2). Amended by final rulemaking at 19 A.A.R. 3882, effec-

tive January 4, 2014 (Supp. 13-4).