What is flattening filter free?

Purpose: The flattening filter (FF) has traditionally been used to flatten beams or create uniform fields in conformal and intensity-modulated radiation therapy (IMRT) but reduces the dose rate.

What is the function of flattening filter in the linear accelerator?

It is well known that the flattening filter in a standard linac acts as an attenuator, the beam hardener and the scatterer. Obviously, the removal of the FF results in an increase in dose rate, softening of the x-ray spectra, reduction in head scattered radiation, and the nonuniform beam profile.

What does FFF mean in radiotherapy?

In external radiotherapy (RT), the use of flattening filter-free (FFF) radiation beams obtained by removing the flattening filter (FF) in standard linear accelerators is rapidly increasing, and the benefits of clinical use are the issue of research.

What are flattening filters made of?

In the most clinical linac, the materials which formed the flattening filters are aluminium, Iron, copper, tungsten, or a mixture of these components, that are all characterised by a high Z material.

What is an isodose curve?

An isodose curve (or contour) is a line of constant absorbed dose. The line is in a plane and, for single radi- ation beams, its value is usually related by a simple percentage value (e.g., 90 percent, 80 percent, etc.) to the peak absorbed dose (or the surface absorbed dose, for x rays below 400 kV) on the beam axis.

When was tomotherapy invented?

History. The tomotherapy technique was developed in the early 1990s at the University of Wisconsin–Madison by Professor Thomas Rockwell Mackie and Paul Reckwerdt.

Why are flattening filters used for high energy photon beams from an accelerator?

Specifically, the spectrum of X photons is shown to be more penetrating when the target is combined with a flattening filter with Al, while the spectrum of X photons combined with a Pb target and flattening filter makes the beam less penetrating.

What is SSD in radiation therapy?

Source to skin distance (SSD) is almost used as an important reference to examine the depth of an x- ray in radiotherapist treatment [1]. The aim of this study is to characterize and to measure the dosimetric output of 6 and 10 MV Varian Clinac CX linear accelerator using the variation of SSD.

How successful is IMRT?

The majority of patients who were treated with intensity-modulated radiation therapy (IMRT) remained alive with no evidence of disease after an average follow-up period of eight years. Researchers followed 561 men who were treated for prostate cancer with IMRT at Memorial Sloan-Kettering Cancer Center.

Can flattening filter-free radiotherapy be implemented on linear accelerators?

This report describes the current state of flattening filter-free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists.

What is the advantage of flattening filter in FFF beam?

Furthermore, removing the flattening filter reduces out-of-field dose and improves beam modeling accuracy. FFF beams are advantageous for small field (e.g., SRS) treatments and are appropriate for intensity-modulated radiotherapy (IMRT).

Why does neutron fluence decrease in a flattening filter?

To a much smaller degree, reduction in the neutron fluence also occurs because the flattening filter is no longer a source of neutrons (the flattening filter produces ~ 10% of neutrons in a high-energy Varian linac 76, 79 and in a 15 MV Siemens beam 80 ).

How do linear accelerators achieve uniform intensity across the beam?

In conventional linear accelerators, uniform intensity across the treatment field (at least nominally) is obtained by placement of a flattening filter in the beam.