§ 221.32a. Radiographic beam limitation.
(a) The useful beam shall be limited to the area of clinical interest.
(b) The beam limiting device shall do one of the following:
(1) Indicate numerically the field size in the plane of the image receptor to which it is adjusted to within 2% of the SID.
(2) Provide for visually defining the perimeter of the X-ray field except for systems designed for one image receptor size. The total misalignment of the edges of the visually defined field with the respective edges of the X-ray field may not exceed 2% of the distance from the source to the center of the visually defined field when the surface upon which it appears is perpendicular to the axis of the X-ray beam.
(c) A means shall be provided for stepless (continuous) adjustment of the size of the X-ray field except for systems which use removable fixed operation beam limiting devices.
(d) A means shall be provided to:
(1) Indicate when the axis of the X-ray beam is perpendicular to the plane of the image receptor if the angle between the axis of the X-ray beam and the plane of the image receptor is variable. This paragraph does not apply to portable, mobile or intraoral dental units.
(2) Align the center of the X-ray field with respect to the center of the image receptor to within 2% of the SID.
(3) Indicate the SID to within 2%.
(e) Intraoral dental X-ray systems designed for use with an intraoral image receptor shall be provided with means to limit SSD to not less than either of the following:
(1) Eighteen centimeters if operable above 50 kVp.
(2) Ten centimeters if not operable above 50 kVp.
(f) Indication of field size dimensions and SIDs shall be specified so that aperture adjustments result in X-ray field dimensions in the plane of the image receptor which correspond to those indicated by the beam-limiting device to within 2% of the SID when the beam axis is indicated to be perpendicular to the plane of the image receptor.
(g) Intraoral dental systems designed for use with an intraoral image receptor shall be provided with a means to limit the X-ray beam so that:
(1) Eighteen centimeters or more, the X-ray field at the minimum SSD shall be containable in a circle having a diameter of no more than 7 centimeters.
(2) Less than 18 centimeters, the X-ray field at the minimum SSD shall be containable in a circle having a diameter of no more than 6 centimeters.
(h) When positive beam limitation is used, the following conditions shall be met:
(1) The radiation beam may not be larger than the linear dimensions of the image receptor being used.
(2) The positive beam limitation device shall allow the operator to further reduce the size of the radiation field.
(i) Mobile or portable X-ray systems, other than intraoral dental X-ray systems, shall be provided with a means to limit the source-to-skin distance to at least 30 centimeters.
(j) Radiographic equipment designed for one or more image receptor sizes at a fixed SID shall be provided with a means to accomplish one of the following:
(1) Limit the field at the plane of the image receptor to dimensions no greater than those of the image receptor and align the center of the X-ray field with the center of the image receptor to within 2% of the SID.
(2) The X-ray field shall be sized and aligned so that at the plane of the image receptor, it does not extend beyond the edge of the image receptor by more than 2% of the SID.
Authority The provisions of this § 221.32a issued under sections 301 and 302 of the Radiation Protection Act (35 P. S. § § 7110.301 and 7110.302); and section 1920-A of The Administrative Code of 1929 (71 P. S. § 510-20); amended under sections 301 and 302 of the Radiation Protection Act (35 P. S. § § 7110.301 and 7110.302); section 1920-A of The Administrative Code of 1929 (71 P. S. § 510-20) and the Radon Certification Act (63 P. S. § § 2001—2014).
Source The provisions of this § 221.32a adopted October 2, 1998, effective October 3, 1998, 28 Pa.B. 4894; amended November 16, 2001, effective November 17, 2001, 31 Pa.B. 6282; amended May 16, 2008, effective May 17, 2008, 38 Pa.B. 2243. Immediately preceding text appears at serial pages (304499) and (304500).
Cross References This section cited in 25 Pa. Code § 221.35a (relating to fluoroscopic X-ray systems).
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