Tissue weighting factor
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At the time the article was created Ankit Balani had no recorded disclosures.View Ankit Balani's current disclosures
At the time the article was last revised Craig Hacking had the following disclosures:
- Philips Australia, Paid speaker at Philips Spectral CT events (ongoing)
These were assessed during peer review and were determined to not be relevant to the changes that were made.View Craig Hacking's current disclosures
The tissue weighting factor (WT) is a relative measure of the risk of stochastic effects that might result from irradiation of that specific tissue. It accounts for the variable radiosensitivities of organs and tissues in the body to ionizing radiation.
In 2007, the International Commission on Radiological Protection (ICRP) published a new set of tissue weighting factors 2 as below:
- WT = 0.12 (for each of 6): stomach, colon, lung, bone marrow (red), breast & remainder tissues*
- WT = 0.08: gonads
- WT = 0.04: urinary bladder, esophagus, liver, thyroid
- WT = 0.01: bone surface, skin, brain, salivary glands
*Remaining tissues, collectively (13 organs): adrenals, extrathoracic region, gallbladder, heart, kidney, lymph nodes, muscle, oral mucosa, pancreas, small intestine, spleen, thymus, and uterus/cervix (♀), prostate(♂).
Calculating sum of all weighted tissue factors: (0.12 x 6) + 0.08 + (0.04 x 4) + (0.01 x 4) = 1.0
The numerical values given above are valid for legal EU regulations for calculating equivalent dose in an organ or tissue.
Note: Changes in respective WT from last ICRP publication-60 of 19913 to ⟶ current ICRP publication-103 of 2007 are:
- gonads: 0.20 ⟶ 0.08
- breast and reminder tissue: 0.05 ⟶ 0.12
- bladder, esophagus, liver, thyroid: 0.05 ⟶ 0.04
- addition of brain and salivary glands to 0.01 category
- 1. Penelope Allisy-Roberts, Jerry R. Williams. Farr's Physics for Medical Imaging. (2007) ISBN: 9780702028441 - Google Books
- 2. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann ICRP. 2007;37(2-4):1-332. doi:10.1016/j.icrp.2007.10.003 - Pubmed
- 3. ICRP, 1991. 1990 Recommendations of the International Commission on Radiological Protection. ICRP Publication 60. Ann. ICRP 21 (1-3).
- 4. Brenner D. Effective Dose: A Flawed Concept That Could and Should Be Replaced. BJR. 2008;81(967):521-3. doi:10.1259/bjr/22942198 - Pubmed