Attenuation coefficient
Updates to Article Attributes
The attenuation coefficient is a measure of how much the incident energy beam (e.g. ultrasound or x-rays) is weakened by the material it is passing through.
Photon interactions
When a photon passes through a matter, it can either penetrate the matter without any interactions (penetration), deposit its energy, and be completely absorbed by matter (absorption), or deposit its energy and deflected from its original path (scatter). The three main mechanisms of photon interactions in body tissue are 3:
The attenuation of X-rays or gamma rays in tissues is generally affected by several factors, namely the energy of the photon, the thickness of the bodily tissue, atomic number, and density of the tissue 3.
In photon interactions, there are two types of attenuation coefficients 2:
Acoustic interactions
In ultrasound, the attenuation coefficient (α) is estimated from the gradient of attenuation against the frequency of ultrasound with units of dB MHz-1 cm-1. In soft tissue, ultrasound attenuation is 0.5 to 0.75 dB MHz-1 cm-14. In fatty liver and fibrotic liver, the attenuation coefficient increases. In the case of breast tissue, the attenuation coefficient decreases in fatty tissue and medullary carcinoma. It increases fibrotic tissue and ductal carcinoma of breasts 1.
-<p>The <strong>attenuation coefficient</strong> is a measure of how much the incident energy beam (e.g. <a href="/articles/ultrasound-introduction" title="Ultrasound (introduction)">ultrasound</a> or <a href="/articles/x-rays-1" title="X-rays">x-rays</a>) is weakened by the material it is passing through.</p><h4>Photon interactions</h4><p>When a photon passes through a matter, it can either penetrate the matter without any interactions (penetration), deposit its energy, and be completely absorbed by matter (absorption), or deposit its energy and deflected from its original path (scatter). The three main mechanisms of photon interactions in body tissue are <sup>3</sup>: </p><ul>- +<p>The <strong>attenuation coefficient</strong> is a measure of how much the incident energy beam (e.g. <a href="/articles/ultrasound-introduction" title="Ultrasound (introduction)">ultrasound</a> or <a href="/articles/x-rays-1" title="X-rays">x-rays</a>) is weakened by the material it is passing through.</p><h4>Photon interactions</h4><p>When a photon passes through a matter, it can either penetrate the matter without any interactions (penetration), deposit its energy, and be completely absorbed by matter (absorption), or deposit its energy and deflected from its original path (scatter). The three main mechanisms of photon interactions in body tissue are <sup>3</sup>:</p><ul>
-</ul><h4>Acoustic interactions</h4><p>In ultrasound, the <a href="/articles/attenuation-ultrasound" title="Attenuation (ultrasound)">attenuation coefficient</a> (α) is estimated from the gradient of attenuation against the frequency of ultrasound with units of dB MHz<sup>-1</sup> cm<sup>-1</sup>. In fatty liver and fibrotic liver, the attenuation coefficient increases. In the case of breast tissue, the attenuation coefficient decreases in fatty tissue and medullary carcinoma. It increases fibrotic tissue and ductal carcinoma of breasts <sup>1</sup>.</p>- +</ul><h4>Acoustic interactions</h4><p>In ultrasound, the <a href="/articles/attenuation-ultrasound" title="Attenuation (ultrasound)">attenuation coefficient</a> (α) is estimated from the gradient of attenuation against the frequency of ultrasound with units of dB MHz<sup>-1</sup> cm<sup>-1</sup>. In soft tissue, ultrasound attenuation is 0.5 to 0.75 dB MHz<sup>-1</sup> cm<sup>-1</sup> <sup>4</sup>. In fatty liver and fibrotic liver, the attenuation coefficient increases. In the case of breast tissue, the attenuation coefficient decreases in fatty tissue and medullary carcinoma. It increases fibrotic tissue and ductal carcinoma of breasts <sup>1</sup>.</p>
References changed:
- 4. Attenuation. Atlas of Ultrasound-Guided Regional Anesthesia. 2019;:5-6. <a href="https://doi.org/10.1016/b978-0-323-50951-0.00003-7">doi:10.1016/b978-0-323-50951-0.00003-7</a>
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