What are the factors contribute to both random and systematic deviations in dose delivery?

Daily patient setup

Target delineation

Dose calculation are the main factors

Manual calculations are based on machine data, which are typically gathered with a flat, homogeneous water phantom.

What is the advangage of image-based

treatment planning System?

The  Image-based treatment planning has allowed incorporation of patientspecific internal heterogeneity information into the calculation of dose.

The normalization depth for photon and electron dosimetry

For photons, d₀ = 10 cm is recommended, but not required. For each photon beam, d₀ is independent of field size and shall be greater than or equal to the maximum d_m.

For electrons, d₀ is taken to be the d_m along the central axis for the same field incident on a water phantom at the same SSD. It is field-size dependent.

Does this protocol require D’₀ =1 cGy/MU ?

No

What are the advantages of choosing a normalization depth of 10 cm?

Choosing d₀ = 10 cm for photon beams eliminates the uncertainty associated with converting the calibrated output to the dose rate at other depths, particularly at d_m 

Different machines of the same energy will be matched at a more clinically relevant depth, which may decrease the differences in programmed MU when moving patients from one machine to another.

Some of the field size dosimetric quantities vary less significantly at depths greater than d_m, making dosimetric measurements less susceptible to setup error.

Some treatment-planning systems require measured output factors at a depth of 10 cm, thus requiring users to measure these data anyway. Choosing a normalization depth of 10 cm eliminates the duplication of effort, either at time of commissioning or during annual inspections.

If another depth is chosen for d₀, at a minimum this depth shall be greater than or equal to the maximum d_m depth, determined from percent depth dose measurements for the smallest field size and greatest SSD used clinically.