Illinois Administrative Code › Title 32 - ENERGY › Part 360 - USE OF X-RAYS IN THE HEALING ARTS INCLUDING MEDICAL, DENTAL, PODIATRY, AND VETERINARY MEDICINE › Appendix A - Medical Radiographic Entrance Exposure Measurement Protocol

Current through Register Vol. 48, No. 28, July 12, 2024
The following protocol shall be used for measuring and
				calculating entrance skin exposures (ESE) for routine diagnostic examinations.
				Radiation measurements shall be performed with a calibrated radiation measuring
				device that is sufficiently sensitive to determine compliance with the criteria
				specified in Section 360.60(e) of this Part. The instrument shall have been
				calibrated within the previous 12 months with devices which have no more than a
				three-step (tertiary) calibration, traceable to the National Institute of
				Standards and Technology. Patients are not involved in the measurement
				protocol.
a) Position the x-ray tube at the source-image
				receptor distance (SID) routinely used and adjust the collimation to the active
				portion of a radiation measuring device.
b) Measure the distance from the x-ray source to the
				source against which the patient rests. Subtract the thickness of the patient
				to obtain the source-skin distance (SSD). The standard patient thickness for
				each projection to be measured shall be the following:
Projection
Thickness (cm)
Chest (PA), Grid
23
Chest (PA), Non-Grid
23
Abdomen (KUB)
23
Lumbo-Sacral Spine (AP)
23
Cervical Spine (AP)
13
Skull (lateral)
15
Foot (D/P)
8
c) Place a radiation measuring device in the center
				of the useful beam, measure and record the distance from the source to the
				device (SDD). Use of a test stand to position the device away from the table
				will reduce backscatter contribution. Placing the radiation measuring device at
				the actual source-skin distance (SSD) will accomplish this and allow direct
				reading of the ESE.
d) Set the exposure technique as follows:
1) For non-phototimed x-ray systems, set the
				controls to the exposure technique used by the x-ray operator for the standard
				patient thickness specified in subsection (b) of this Section.
2) For phototimed x-ray systems, set the controls to
				the exposure technique used by the x-ray operator for the standard patient
				thickness specified in subsection (b) of this Section, and use one of the two
				methods below:
A) Place an appropriate phantom (simulating body
				attenuation) in the useful beam between the radiation measuring device and the
				radiographic tabletop; or
B) Set an appropriate exposure technique in the
				manual mode (without activation of the phototimer)
AGENCY NOTE: Specifications for appropriate phantoms
				are included in the American Association of Physicists in Medicine (AAPM)
				Report No. 31, entitled "Standardized Methods for Measuring Diagnostic X-Ray
				Exposures" (July 1990). A copy of this report is available for public
				inspection at the Illinois Emergency Management Agency, 1035 Outer Park Drive,
				Springfield, IL. Copies of this report may also be obtained from the AAPM, One
				Physics Ellipse, College Park MD 20740-3846.
e) Make a radiographic exposure (without patient)
				and record the reading obtained from the radiation measuring device
f) Calculate the entrance skin exposure for the
				specific examination, using the radiation exposure reading from subsection (e)
				of this Section and the equation in this subsection (f) below (if a direct
				result was not obtained with the dosimeter at the SSD). The entrance skin
				exposure equals the product of the radiation exposure reading from subsection
				(e) of this Section multiplied by the square of the ratio of the SDD, to the
				SSD. This expression is mathematically represented by the equation below (if a
				direct result was not obtained with the dosimeter at the SSD):
Click here to view
				image
g) Compare the results of the calculation from
				subsection (f) of this Section with the criteria specified in Section 360.60(e)
				of this Part to determine compliance.
AGENCY NOTE: There are many different techniques for
				  measuring ESE that may result in significant differences in measured values.
				  Factors that can cause variations include instrument calibration, backscatter,
				  collimation, estimation of focal spot location, choice of phantom, location of
				  dosimeter in the primary beam, etc. Because of these variations, the procedure
				  for determining the ESE should be performed with strict attention to each
				  detail noted above.