## 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.

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