IAEA TRS-398 kV x-rays data

A web app for back scatter factors and water/air ratios of mass energy-absorption coefficients

IAEA TRS-398 kV x-rays data

DATA FOR THE DOSIMETRY OF LOW- AND MEDIUM-ENERGY KV X RAYS USING IAEA TRS-398


This web site provides graphical user interfaces (GUIs) for the calculation of dosimetric quantities for the dosimetry of low- and medium-energy kV x rays, as a function of the beam quality Q specified by the kilovoltage and half-value layer in mm of Al or mm of Cu, $Q(\text{kV},\text{HVL})$. The calculated quantities correspond to the two routes described in the Code of Practice:

  1. Measurements with ionization chambers calibrated in terms of air kerma free-in-air (FIA)
    1. For low-energy kV x rays, the GUI BmuenAl calculates backscatter factors in water, $B_\text{w}(Q,f,\text{SSD})$, and water/air ratios of mass energy-absorption coefficients free-in-air, $[\mu_{\text{en}}(Q)/\rho]^{\text{FIA}}_{\text{w,air}}$, for the determination of the absorbed dose to water at the surface of a water phantom based on in-air measurements with a field diameter f and a source-to-surface distance SSD. The ranges included are 10-150 kV, HVL between 0.01 and 10 mm Al, f between 1 cm and 30 cm, and SSD between 10 cm and 100 cm.

      Note that, although strictly the recommended low-energy range is up to 100 kV, it has been extended up to 150 kV to include cases where an HVL in mm of Al is used at these kilovoltages.

    2. For medium-energy kV x rays, the GUI muen2Cu calculates the water/air ratios of mass energy-absorption coefficient at 2 cm depth in water, $[\mu_{\text{en}}(Q,f,\text{SSD})/\rho]^{\text{z=2}}_{\text{w,air}}$, for the determination of the absorbed dose to water at a depth of 2 cm based on in-water-phantom measurements at this depth. The ranges included are 70-300 kV, HVL between 0.01 and 5.5 mm Cu, f between 1 cm and 30 cm, and SSD between 10 cm and 100 cm.

    3. Although TRS-398 does not recommend that medium-energy kV x-ray beams be measured in air, data for this alternative (backscatter factors for 70-300 kV, HVLs specified in mm of Cu) is included as an option (BmuenCu) for users that base their dosimetry on this procedure.

  2. Measurements with ionization chambers calibrated in terms of absorbed dose to water

    1. For low-energy kV x rays, the GUI kgBwAl calculates the backscatter component in a PMMA phantom of the geometry factor for a clinical beam quality, Q, $k^{\text{PMMA}}_{Q,\text{g}}$ for (f,SSD) conditions different from those for the clinical reference beam $Q_\text{0}$, $(f_\text{0}, \text{SSD}_\text{0})$. The ranges included are 10-100 kV, HVL between 0.01 and 10 mm Al, f between 1 cm and 30 cm, and SSD between 10 cm and 100 cm.

    2. For medium-energy kV x rays, the GUI kgmuen2Cu calculates the $[\mu_{\text{en}}(Q,f,\text{SSD})/\rho]^{\text{z=2}}_{\text{w,air}}$ component of the geometry factor for a clinical beam quality Q, $k^{\text{z=2}}_{Q,\text{g}}$, for $(f,\text{SSD})$ conditions different from those for the clinical reference beam $Q_\text{0}$, $(f_\text{0}, \text{SSD}_\text{0})$. The ranges included are 70-300 kV, HVL between 0.01 and 5.5 mm Cu, f between 1 cm and 30 cm, and SSD between 10 cm and 100 cm.

The parameters (e.g., kV, HVL, etc) that are used in the calculation of the different quantities on this website are modified with range sliders. After a range slider has been selected, fine tuning of that parameter can be achieved using the left or right arrow key on a physical keyboard.

Details on the input for these calculations are given in the report Data for the dosimetry of low- and medium-energy kV x rays (Andreo 2018). The present GUIs perform interpolations of extended databases for HVLs in mm Al and mm Cu of $B_\text{w}(\text{kV}, \text{HVL}, f, \text{SSD})$, $[\mu_{\text{en}}(\text{HVL})/\rho]^{\text{FIA}}_{\text{w,air}}$ and $[\mu_{\text{en}}(\text{kV}, \text{HVL}, f, \text{SSD})/\rho]^{\text{z=2}}_{\text{w,air}}$.