Washington Administrative Code › Title 246 - Health, Department of › RADIATION › Chapter 246-226 - Radiation protection - Computed tomography › Section 246-226-010 - Definitions, abbreviations, and acronyms

Current through Register Vol. 24-14, July 15, 2024
The definitions, abbreviations, and acronyms in this
				  section, WAC
				  246-220-010 and
				  246-225-010, apply throughout
				  this chapter unless the context clearly indicates otherwise.
(1) "CT" or "computed tomography" means
				technology that uses computer-processed X rays to produce tomographic images
				(virtual slices) of specific areas of the patient's body or scanned
				object.
(2) "CTDI" or "computed
				tomography dose index" 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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Where:
Z = Position along a line perpendicular to the tomo-graphic
				  plane;
D(z) = Dose at position z;
T = Nominal tomographic section thickness;
N = Number of tomograms produced in a single scan.
And:
The dose profile is centered around z and that, for a
				  multiple tomogram system, the scan increment between adjacent scans is
				  nT.
(3)
				"CTDIvol" means the product of the
				CTDIw and NT, divided by the table increment I and
				expressed as milliGray.
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(4) "CT dosimetry phantom" means an object
				used to determine the dose delivered by a CT X-ray system.
(5) "CTN" or "computed tomography number"
				means the number used to represent the X-ray attenuation associated with each
				elemental area of the CT image:
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				  here to view image
Where:
k = A constant, a normal value of 1,000 when the Hounsfield
				  scale of CTN is used;
µx = Linear attenuation
				  coefficient of the material of interest;
µw = Linear attenuation
				  coefficient of water.
(6)
				"CT procedure" means an activity directed at or performed on a patient
				necessary to make a diagnosis using a CT X-ray system including, but not
				limited to, setting, modifying, or applying parameters or protocols.
(7) "CT simulator" means a CT unit that
				allows for precise cancer treatment planning by demonstrating the relationship
				between the target tumor and healthy tissues while the patient is in a
				treatment position.
(8) "CT X-ray
				system" means a gantry-style X-ray system that generates a tomographic image
				through acquisition of cross-sectional image slices perpendicular to the plane
				of travel of the gantry.
(9)
				"Department" means the Washington state department of health.
(10) "Dose profile" means the dose as a
				function of position along a line.
(11) "DLP" or "dose length product" means the
				product of the CTDIvol and the scan length of a single
				or group of scans performed on the same body part. This number can be
				calculated over the entire CT procedure to give an estimate of the total dose.
				The value is expressed in milliGray centimeters.
(12) "Filtration" means material placed in
				the beam to preferentially absorb low energy photons that contribute no
				diagnostically meaningful data to the image.
(13) "Fixed CT X-ray system" means a CT X-ray
				system that is permanently mounted in the building in which it is used or a
				portable CT X-ray system that is permanently stationed in one
				location.
(14) "Joint commission"
				means the independent, not-for-profit organization that accredits and certifies
				health care organizations and programs in the United States.
(15) "kW" or "kilowatts" means peak power,
				which is the highest rated kilovoltage of a CT X-ray system multiplied by the
				maximum rated amperage multiplied by the power factor.
(16) "Lead CT technologist" means the
				radiologic technologist licensed under chapter 18.84 RCW and designated by the
				registrant to perform the duties identified in this chapter. A licensed health
				care professional listed in
				RCW
				   18.130.040 acting within their scope of
				practice may also be designated by the registrant to perform the duties
				identified in this chapter.
(17)
				"Lead interpreting CT physician" means a physician licensed under chapter 18.71
				or 18.57 RCW designated by the registrant to perform the duties identified in
				this chapter. A licensed health care professional listed in
				RCW
				   18.130.040 acting within their scope of
				practice may also be designated by the registrant to perform the duties
				identified in this chapter.
(18)
				"Medical physicist" means a physicist who meets the requirements of WAC
				246-226-065.
(19) "Mobile CT X-ray
				system" means a CT X-ray system that is permanently mounted in a vehicle or
				trailer.
(20) "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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				  here to view image
Where:
= Linear attenuation coefficient of the material of
				  interest;
µw = Linear attenuation
				  coefficient of water;
s = Standard deviation of the CTN of picture elements in a
				  specified area of the CT image.
(21) "Nominal tomographic section thickness"
				means the full width at half-maximum of the sensitivity profile taken at the
				center of the cross-sectional volume over which X-ray transmission data are
				collected.
(22) "Operator" means a
				Washington state licensed health care professional whose scope of practice
				includes CT diagnostics which includes choosing the appropriate scan protocol,
				appropriately adjusting parameters when necessary, an
d
administering the CT procedure.
(23) "PACS" or "picture archiving and
				communication system" means a medical imaging technology that provides
				economical storage of and convenient access to images from CT.
(24) "Parameter" means settings on the CT
				X-ray system that can be modified including, but not limited to, peak tube
				potential in kV, filtration thickness, the tube current in mA and the exposure
				time in milliseconds, and the product of tube current and exposure time in
				mAs.
(25) "Physician" means an
				individual licensed under chapter 18.71 or 18.57 RCW.
(26) "Portable CT X-ray system" means a CT
				X-ray system that is not permanently mounted in a building, vehicle, or trailer
				and is able to move between locations of use.
(27) "Protocol" means the collection of
				settings and parameters affecting CT dose and image quality that specify how
				data collection and reconstruction, patient positioning, and contrast
				administration are performed
(28)
				"Radiologic technologist" means an individual licensed under chapter 18.84
				RCW.
(29) "Scan" means the complete
				process of collecting X-ray transmission data for the production of a
				tomogram.
(30) "Scan increment"
				means the amount of relative displacement of the patient with respect to the CT
				X-ray system between successive scans measured along the direction of such
				displacement.
(31) "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
(32) "SSDE" or "size specific dose estimate"
				means a patient dose estimate which takes into consideration corrections based
				on the size of the patient using linear dimensions measured on the patients or
				the patient images.
(33) "Tomogram"
				means a two dimensional image representing a slice or section through a three
				dimensional object using a CT X-ray system.
(34) "Tomographic plane" means the geometric
				plane which is identified as corresponding to the tomogram.
(35) "Tomographic section" means the volume
				of an object whose X-ray attenuation properties are imaged in a
				tomogram.