Code of Massachusetts Regulations › 105 CMR - DEPARTMENT OF PUBLIC HEALTH › Title 105 CMR 120.000 - The Control of Radiation › RECORDKEEPING REQUIREMENTS › Section 120.409 - Computed Tomography (CT) X-ray Systems

Current through Register 1525, July 5, 2024
Any facility offering CT services after April 30, 2011 shall
				  have ACR accreditation.
Definitions
. In addition to the
				  definitions provided in
				  105 CMR 120.402, the
				  following definitions shall be applicable
Computed Tomography Dose Index
				  (CTDI)
means the integral of the dose profile along a line
				  perpendicular to the tomographic plane divided by the product of the nominal
				  tomographic section thickness and the number of tomograms produced in a single
				  scan, that is:
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				  image
where:
z = Position along a line perpendicular to the tomographic
				  plane;
D(z) = Dose at position z;
T = Nominal tomographic section thickness;
n = Number of tomograms produced in a single scan.
Computed Tomography Dose Index
				  (CTDI)
assumes that the dose profile is centered around z=0 and
				  that, for a multiple tomogram system, the scan increment between adjacent scans
				  is nT.
CT Dosimetry Phantom
means the
				  phantom used for determination of the dose delivered by a CT x-ray system. The
				  phantom shall be a right circular cylinder of polymethl-methacrylate of density
				  1.19±0.01 grams per cubic centimeter. The phantom shall be at least 14
				  centimeters in length and shall have diameters of 32.0 centimeters for testing
				  any CT system designed to image any section of the body (whole body scanners)
				  and 16.0 centimeters for any system designed to image the head (head scanners)
				  or for any whole body scanner operated in the head scanning mode. The phantom
				  shall provide means for the placement of a dosimeter(s) along its axis of
				  rotation and along a line parallel to the axis of rotation 1.0 centimeter from
				  the outer surface and within the phantom. Means for the placement of a
				  dosimeter(s) or alignment device at other locations may be provided for
				  convenience. Any effect on the doses measured due to the removal of phantom
				  material to accommodate dosimeters shall be accounted for through appropriate
				  corrections to the reported data or included in the statement of maximum
				  deviation for the values obtained using the phantom.
Dose Profile
means the dose as a
				  function of position along a line.
Modulation Transfer Function
means
				  the modulus of the Fourier transform of the impulse response of the
				  system.
Noise
means the standard deviation
				  of the fluctuations in CTN expressed as a percentage of the attenuation
				  coefficient of water. Its estimate (Sn) is calculated using the following
				  expression:
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				  image
where:
CS = Linear attenuation coefficient of the material of
				  interest.
µw = Linear attenuation
				  coefficient of water.
= Standard deviation of the CTN of picture elements in a
				  specified area of the CT image.
Picture Element
means an elemental
				  area of a tomogram.
Remanufacturing
means modifying a CT
				  system in such a way that the resulting dose and imaging performance become
				  substantially equivalent to any CT x-ray system manufactured by the original
				  manufacturer on or after November 29, 1984. Any reference in
				  105 CMR
				  120.408 to
manufacture
,
manufacturer
, or
manufacturing
includes
remanufacture
,
Remanufacturing
, respectively.
Sensitivity Profile
means the
				  relative response of the CT x-ray system as a function of position along a line
				  perpendicular to the tomographic plane.
Single Tomogram System
means a CT
				  x-ray system which obtains x-ray transmission data during a scan to produce a
				  single tomogram.
(A)
Equipment Requirements
.
(1)
Tomographic Plane Indication
				and Alignment
.
(a) For any single
				tomogram system, means shall be provided to permit visual determination of the
				tomographic plane or a reference plane offset from the tomographic
				plane.
(b) For any multiple
				tomogram system, means shall be provided to permit visual determination of the
				location of a reference plane. The reference plane can be offset from the
				location of the tomographic planes.
(c) If a device using a light source is used
				to satisfy 105 CMR 120.409(A)(1)(a) or (b), the light source shall provide
				illumination levels sufficient to permit visual determination of the location
				of the tomographic plane or reference plane under ambient light conditions of
				up to 500 lux