## What is the linear quadratic model?

The linear-quadratic model was derived by Chadwick and Leenhouts (2). They proposed that the linear component (A*X) represents cell death due to a single lethal hit to the DNA, and that the quadratic (B*X2) component represents cell death that only happens with two hits.

**What are the 5 R’s of radiotherapy?**

In conventional radiotherapy (RT), the relative biologic effectiveness of radiation is influenced by radiobiological determinants, the so-called ‘5Rs’: Repair, Repopulation, Redistribution, Reoxygenation, and Radiosensitivity.

**What is alpha beta ratio in radiobiology?**

The alpha/beta ratio is the dose where the linear as well as the quadratic component cause the same amount of cell killing. Generally speaking, the higher the alpha/beta ratio is, the more linear the cell survival curve is.

### What is the alpha beta ratio for spinal cord?

The repair capacity (alpha/beta ratio) for the cervico-thoracic and lumbar spinal cord was assumed to be 2 Gy and 4 Gy, with a BEDtolerance of 100 Gy and 84 Gy, respectively.

**What is the multi target model?**

This concept is based on the ‘multitarget single-hit’ model that was proposed later [9]. This model defines that there are more targets than just one in an organism, and inactivation of all the targets leads to death of the organism.

**What is survival curve in sterilization?**

A cell survival curve is a curve used in radiobiology. It depicts the relationship between the fraction of cells retaining their reproductive integrity and the absorbed dose of radiation. Conventionally, the surviving fraction is depicted on a logarithmic scale, and is plotted on the y-axis against dose on the x-axis.

#### What is redistribution in radiotherapy?

Redistribution: is defined by cells that survive a dose of radiation due to synchronisation in resistant phases of the division cycle and redistributing into more sensitive phases of the cell cycle during subsequent doses of radiation.

**What is repair Radiobiology?**

Abstract. Three dualities underscore the role of repair in radiobiology: the discrete and random nature of energy deposition; the coupled processes of damage and repair; and the harmful and beneficial properties of radiation in connection with issues of public health and the radiation therapy of cancer, respectively.

**What is a good alpha beta ratio?**

The alpha/beta ratios were usually at least as high as those for acutely responding normal tissues, and 36/48 tumors gave values greater than 8 Gy. Low values of less than 5 Gy were obtained for only 4/48 tumors.

## What is Bed and EQD2?

The important difference between BED and EQD2 is that BED reports an effective dose, while EQD2 gives the equivalent dose needed in 2 Gy/fx to achieve that effective dose. Using the previous example, suppose you want to figure out what 2 Gy fractionation scheme would give the same BED as the original prescription.

**What does Alpha Beta mean?**

Alpha is the excess return on an investment relative to the return on a benchmark index. Beta is the measure of relative volatility. Alpha and beta are both risk ratios that calculate, compare, and predict returns.

**What is the identity of Alpha Beta?**

Identity 1: α2 + β 2 α2+β2=(α+β)2−2αβ

### What is the linear quadratic model in radiation biology?

The linear-quadratic model is one of the key tools in radiation biology and physics. It provides a simple relationship between cell survival and delivered dose: [Formula: see text], and has been used extensively to analyse and predict responses to ionising radiation both in vitro and in vivo. Despit …

**Is the linear-quadratic dose response model still relevant?**

It is difficult to over-state the ubiquity of the linear-quadratic (LQ) dose response model in this area. Since its early formulations over 50 years ago, it has become the preferred method for characterising radiation effects in both the laboratory and the clinic.

**What is the role of mathematical modelling in radiotherapy?**

From almost immediately after the first radiotherapy treatments over 100 years ago, mathematical modelling has played an important role in how we understand and optimise radiation delivery for the treatment of cancer.

#### Is there a model equivalent to the modern LQ?

A broad range of publications over several decades independently proposed models that are recognisably equivalent to the modern LQ, with justifications ranging from empirical fitting to detailed descriptions of DNA repair, emerging from both preclinical cell survival data as well as tissue iso-effect studies.