Radiation Protection in Mammography: Recommended Safety Procedures for the Use of Mammographic X-Ray Equipment - Safety Code 33

Appendix II

Recommended Glandular Dose Limits per Irradiation

While recommended dose limits have been defined for radiation workers and members of the public, there is no specific permissible level recommended for patients undergoing diagnostic X-rays procedures. However, it is possible to recommend limits on the amount of radiation breast tissues receive by setting dose limits on the level of radiation a representative breast phantom would receives for a given irradiation. This breast phantom represents a breast which is composed of 50 percent fat and 50 percent glandular tissues and is compressed to 45 mm thickness. The dose received by the phantom would become a representative mean glandular dose for a breast of similar composition and thickness when compressed.

A mammographic X-ray system producing phantom dose estimates greater than the values set in Table 8 would use more radiation than necessary to produce quality mammographic images and the performance of the mammographic X-ray system and film processing would need to be reassessed.

These glandular dose estimates are calculated by measuring the phantom surface dose while the mammographic X-ray equipment is operated in a normal fashion. The surface dose values are then applied to Table 9 to obtain the mean glandular dose.

Table 8: Recommended dose limits per irradiation

Procedure	Mean Glandular Dose Limits
Film-Screen Mammography (no grid)	1.0 mGy (100 mrad)
Film-Screen Mammography (grid technique)	2.0 mGy (200 mrad)
Xeromammography	4.0 mGy (400 mrad)

 

Table 9: Mean Glandular Dose in mrad (or in mGy) for Surface Exposure of 1 R (or 1 Gy)¹

	Mo Target / Mo FilerX-ray Tube Voltage (kVp)											W Target Al Filter Combination
HVL	23	24	25	26	27	28	29	30	31	32	33
0.23	109
0.24	113	116
0.25	117	120	122
0.26	121	124	126	128
0.27	126	128	130	132	134
0.28	130	132	134	136	138	139
0.29	135	137	139	141	142	143	144
0.30	139	141	143	145	146	147	148	149				170
0.31	144	146	147	149	150	151	152	153	154			175
0.32	148	150	151	153	154	155	156	158	159	160	160	180
0.33	153	154	155	157	158	159	160	162	163	164	164	185
0.34	157	159	160	161	162	163	164	166	167	168	168	190
0.35		163	164	166	167	168	169	170	171	172	172	194
0.36			168	170	171	172	173	174	175	176	176	199
0.37				174	175	176	177	178	178	179	180	204
0.38					179	180	181	182	182	183	184	208
0.39						184	185	186	186	187	188	213
0.40							189	190	191	192	192	217
0.41								194	195	196	196	221
0.42										200	200	225
0.43											204	230
0.44												234
0.45												238

¹Wu X, "Breast Dosimetry in Screen-film Mammography." published in "Screen film mammography; imaging considerations and medical physics responsibilities." Madison, WI, Medical Physics Publishing: 159-175 (1991). Stanton et al. "Dosage evaluation in mammography." Radiology 150:577-584 (1984).