## How is EQD2 calculated?

EQD2 was calculated with the equation EQD2 = D × [(d + α/β)/(2 + α/β)], as derived from the linear-quadratic model; D = total dose, d = dose per fraction, α = linear (first-order dose-dependent) component of cell killing, β = quadratic (second-order dose dependent) component of cell killing, α/β ratio = the dose at …

### What is GEC Estro?

Responsibilities. GEC-ESTRO was formed in 1990 from the amalgamation of the The Groupe Européen de Curiethérapie (GEC) and the European SocieTy for Radiotherapy & Oncology (ESTRO).

#### What is EQD2?

Biological Effective Dose (BED) and Equivalent Dose in 2Gy Fractions (EQD2) are often used to quantify radiobiological concepts into concrete interpretable values.

**What is EQD2 in radiotherapy?**

These simplified biologically equivalent doses are called either EQD2, denoting equivalent total doses in 2-Gy fractions [13]. Rectal bleeding is a common late toxicity of pelvic radiation.

**What is the alpha beta ratio?**

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 HR CTV?

As defined by GEC-ESTRO, the high risk. CTV (HR-CTV) 2-includes the GTV at the time of brachytherapy plus any MRI grey zones. The HR CTV includes the whole cervix and presumed. extracervical spread.

### How is RBE calculated?

RBE is calculated as a ratio of the reference radiation dose to the dose of the test radiation (ICRP, 2003): 3. However, the value of RBE varies depending on the level of effect being considered (Fig 1). The ratio Dγ High/Dn High may be different from Dγ Low/Dn Low.

#### What is the linear quadratic model?

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: S = e−αD−βD2, and has been used extensively to analyse and predict responses to ionising radiation both in vitroand in vivo.

**What does a low alpha beta ratio mean?**

Low alpha/beta values (1.5 to 5 Gy) have been observed for late responding normal tissues and indicate that radiation damage should be greatly spared by the use of dose fractions smaller than the 2 Gy used in conventional radiotherapy.

**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.

## How to calculate eqd2 in 2 Gy FX?

To make it simple, consider a “2 Gy fraction conversion factor”, C: which will depend on the fraction size and αααα/ββββratio for each case. EQD2 =Nd ×C EQD2 – Eq uivalent Dose in 2 Gy Fx

### What is eqd2 in radiology?

EQD2= dose in 2 Gy fractions biologically equivalent to dose D given in fractions of size d, in units of Gray E is biological effect, D is total dose (D = nd), d is dose per fraction, n is the number of fractions, and alpha/beta is a property of the irradiated tissue.

#### How do you convert bed to eqd2?

EQD2 – Eq uivalent Dose in 2 Gy Fx EQD2 is the BED value converted back to an equivalent dose in traditional 2 Gy fractions: or, combining equations: = × + α/ β 2 BED EQD 2 1

**What is the dose per HDR fraction for 70 Gy eqd2?**

For 70 Gy EQD2 the dose per HDR fraction is 4.5 Gy (18 Gy). The same dose is reached with 48 PDR pulses with 54 cGy/puls, 1 puls/h (26 Gy), and LDR with 54 cGy/h in 48 h (26 Gy). 2.1. Point doses versus dose volume parameters