Reference dosimetry

OpenDose Calculator
Personalized dosimetry

OpenDose 4D
“OpenDose brings together resources and expertise to provide open access material for the benefit of Nuclear Medicine dosimetry through an international collaboration.”

Dosimetry in Nuclear Medicine (diagnostic or therapy) can be implemented using the
methodology introduced in the late 60s by the Medical Internal Radiation Dose (MIRD)
committee of the American Society of Nuclear Medicine (SNM). This methodology, known as
the *MIRD formalism* [1] can be expressed as:
\[ \overline{D}_{Target} = \sum_{Source} \widetilde{A}_{Source}
\times S_{\left( Target \leftarrow Source \right)} \]
where \( \overline{D}_{Target} \) is the absorbed dose (Gy) delivered to the target
(organ or tissue), \( \widetilde{A}_{Source} \) is the cumulated activity (i.e. the total
number of disintegrations, Bq.s) occurring in each source (organ or tissue) and
\( S_{\left( Target \leftarrow Source \right)} \) is the mean absorbed dose in a target
per nuclear disintegration in the source (*S value*,
Gy.Bq^{-1}.s^{-1}).
This formalism separates the determination of the absorbed dose in two independent tasks:
the estimation of the cumulated activity \(\widetilde{A}_{Source}\) and the calculation of
the *S value*. *S values* are obtained for a specific human model and for a
given radioisotope, and can be expressed as:
\[ S_{\left( Target \leftarrow Source \right)} =
\sum_i y_i E_i \Phi_{i \left( Target \leftarrow Source \right)} \]
where \( \Phi_{i \left( Target \leftarrow Source \right)} \) is the Specific Absorbed
Fraction (SAF, kg^{-1}) for radiation type i and \(y_i\), \(E_i\) are the yield
(Bq^{-1}.s^{-1}) and energy (J) of radiation type i, respectively.
The calculation of SAFs is done through intensive Monte Carlo simulations of
radiation transport in the human model, for every particle type (photons, electrons) and
energy.

The OpenDose project is a collaborative effort to generate and distribute free dosimetric
data for the benefit of the Nuclear Medicine community. By sharing expertise and resources,
the collaboration can produce data for one human model in a few months. SAFs are produced
independently using different Monte Carlo (MC) codes with different radiation transport
algorithms and physics models, allowing data cross-verification. *S values* are then
calculated using SAFs and radioisotope decay characteristics. All data produced by OpenDose
is provided with statistical uncertainties.

[1] Loevinger R, Budinger TF, Watson EE. MIRD primer for absorbed dose calculations. Society of Nuclear Medicine, 1991.