Quality factor

The quality factor is a parameter from radiation dosimetry . Since the probability of stochastic radiation effects depends not only on the absorbed dose but also on the type of radiation, the quality factor was introduced to define the dose equivalent . The dose equivalent is the absorbed dose absorbed by the body through ionizing radiation multiplied by a quality factor.

The quality factor takes into account the fact that different types of ionizing radiation have different effects on the cells of the body tissue due to their different ionization capacity. The quality factor Q is a function of the unlimited linear energy transfer :

{\ displaystyle L _ {\ infty} = {\ frac {{\ text {d}} E} {{\ text {d}} x}}}

.

The relationship between the quality factor and the linear energy transfer was determined by the international radiation protection commission ICRP as shown in the following table:

lin. energy transfer L in keV / µm	Quality factor Q (L)
${\ displaystyle <10 \,}$	${\ displaystyle 1 \,}$
${\ displaystyle 10-100 \,}$	${\ displaystyle 0 {,} 32 \ cdot L-2 {,} 2}$
${\ displaystyle> 100 \,}$	${\ displaystyle {\ frac {300} {\ sqrt {L}}}}$

In the case of radiation fields in which different energy transfers occur, the entire quality factor is calculated by averaging over L :

{\ displaystyle {\ overline {Q}} = {\ frac {1} {Q}} \ cdot \ int _ {L} Q (L) \ cdot D_ {L} \ cdot {\ text {d}} L}

The quality factors Q differ from the radiation weighting factors w _R , which also assess the biological effectiveness of different types of radiation. However, these are used to calculate the organ dose H _T employed.

Historical

Before 1991, the dose equivalent was calculated as the product of the quality factor Q and the modifying factor N. The following quality factors were assigned to the various types of radiation:

Type of radiation	lin. energy transfer L in keV / µm	Quality factor Q (L)
β , photons	${\ displaystyle <3 {,} 5 \,}$	${\ displaystyle 1 \,}$
α , p , n	${\ displaystyle 3 {,} 5-7 {,} 0 \,}$	${\ displaystyle 1-2 \,}$
	${\ displaystyle 7-23 \,}$	${\ displaystyle 2-5 \,}$
	${\ displaystyle 23-53 \,}$	${\ displaystyle 5-10 \,}$
	${\ displaystyle> 53 \,}$	${\ displaystyle 10-20 \,}$

Individual evidence

^ ICRP, 1991. 1990 Recommendations of the International Commission on Radiological Protection. ICRP Publication 60th Ann. ICRP 21 (1-3).
↑ Hanno Krieger: Fundamentals of radiation physics and radiation protection. BG Teubner, Wiesbaden 2004, ISBN 3-519-00487-9 , p. 295f.
↑ Hanno Krieger: Fundamentals of radiation physics and radiation protection. BG Teubner, Wiesbaden 2004, ISBN 3-519-00487-9 , p. 308f.

[1] ICRP, 1991. 1990 Recommendations of the International Commission on Radiological Protection. ICRP Publication 60th Ann. ICRP 21 (1-3).

[2] Hanno Krieger: Fundamentals of radiation physics and radiation protection. BG Teubner, Wiesbaden 2004, ISBN 3-519-00487-9 , p. 295f.

[3] Hanno Krieger: Fundamentals of radiation physics and radiation protection. BG Teubner, Wiesbaden 2004, ISBN 3-519-00487-9 , p. 308f.