What is tissue phantom ratio?

What is tissue phantom ratio?

Tissue Phantom Ratio is defined as the quotient of ab- sorbed dose at a given depth d to the absorbed dose at fixed refer- ence depth in water phantoms [10,11].

What is SSD and sad technique in radiotherapy?

Modern photon beam radiotherapy is carried out with a variety of beam energies and field sizes under one of two set-up conventions: a constant source to surface distance (SSD) for all beams or an isocentric set-up with a constant source to axis distance (SAD).

What is build-up region radiotherapy?

The dose of build-up region consists of a primary component such as electrons, photons, and electron contamination from the treatment head and the air between the patient and treatment head.

What is DMAX 10 MV?

For 10 MV d(max) is 2 cm for a field size of 5 x 5 cm2 and 2.5 cm for a 10 x 10 cm2 field.

Does Dmax change with field size?

For megavoltage x-ray beams, it is well known that the percent depth-dose increases considerably with field size in the buildup region, resulting in a significant shift in the apparent position of maximum dose, dmax.

Why does PDD increase with SSD?

The percentage depth dose (PDD) increases with SSD due to the effects of inverse square law. NO dependance on the SAD or SSD. and hν constant TMR decreases with increasing z.

What is tissue max ratio?

The concept of tissue-maximum ratios (TMR) as a basis of dose computations has posed problems when applied to a whole range of clinically used megavoltage beams. Another problem is the definition of scatter-maximum ratio (SMR) which assumes a value of zero at the depth of maximum dose.

What is sad technique in radiotherapy?

International Conference on Physical Instrumentation and Advanced Materials. IOP Publishing. IOP Conf. Series: Journal of Physics: Conf. Series 853 (2017) 012023 doi :10.1088/1742-6596/853/1/012023.

What is the Dmax for 6mv?

For 6 MV x-ray beams we observe that the depth of maximum dose d(max) is 1.5 and 2 cm for field sizes of 5 x 5 and 10 x 10 cm2 respectively. For 10 MV d(max) is 2 cm for a field size of 5 x 5 cm2 and 2.5 cm for a 10 x 10 cm2 field.

What is the Dmax for a 15 MV beam?

The depth dose characteristics of photon beam is dmax of 3.0 cm and percentage depth dose of 76.8% at 10 cm, 100 cm source-surface distance, field size of 10 x 10 cm2 for 15 MV X-ray beam.

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.