Medical dosimetry calibration services

The Laboratory for Fundamental Medical Dosimetry (LFMD) within the DTU Dosimetry Reference Laboratory at DTU Health Tech offers DS/EN ISO/IEC 17025:2017 accredited calibrations of ionization chambers and electrometers in the context of radiotherapy dosimetry in accordance with the IAEA TRS-398 code of practice or similar protocols.

DTU Dosimetry Reference Laboratory is accredited by Danish Accreditation and Metrology Fund (DANAK). The laboratory calibration and measurement capability (CMC) can be found here: DANAK database (accreditation reg. no. 266). The DANAK accreditation document can be found here (pdf file).

Ionization chamber calibrations are traceable to PTB in Germany.

Planned calibration periods for ionization chambers: November 2023 + March 2024. Please send mail to indicate if you are potentially interested in calibrations at a given time (then will influence the planning of these activities)..

For bookings, further information or discussions about the procedure, please contact:

List of DS/EN ISO/IEC 17025:2017 accredited calibration services:

  • Ionization chamber (absorbed dose to water) in Co-60 beam.
    Measurements of initial recombination and polarity are included in the certificate. 

  • Ionization chamber (absorbed dose to water) in Co-60 and five MV photon beams (4 MV - 18 MV). Measurements in Co-60 of initial recombination and polarity are included in the certificate.
    Measurements in MV beams of volume recombination. 

  • Electrometer, charge calibration.

  • Electrometer, current calibration (DC).  

List of other services (not accredited):

  • Separate test of triax cables (leakage test for a range of high voltages, e.g. from 0 to +/- 500 V).

  • Test of the full customer system (electrometer, ionization chamber and cable) in linac MV beams (and/or cobalt) against DTU reference measurements. For example, it can be demonstrated if the current from the customer chamber under irradiation as measured with the customer electrometer system (after correction in accordance with the electrometer calibration certificate) at a given high-voltage setting is consistent with measurements performed with the same chamber and under the same conditions using the DTU master electrometer system and a DTU cable. The test could, for example, be in the 6 MV and/or 10 MV FFF (flattening-filter free) linac beams as to cover a range of clinically relevant dose-per-pulse conditions. Note that such system tests in cobalt are normally conducted under conditions of low (stable) currents (DC) whereas accelerator beams require that the electrometer can handle pulsed currents with high peak values. 


Water-tight ionization chambers are calibrated directly in water unless otherwise requested.

High-voltage settings 
Ionization chambers are calibrated at the main voltage requested by the customer. 

Measurements with LFMD ionization chambers are normally carried out using a high-voltage setting such that negative charge is collected. For PTW30013, PTW31021, PTW34001, and FC65G ionization chambers we use 300 V, for NE2571 chambers we use 250 V, and for NPL2611 chambers we use 200 V. 

Recombination measurements
Special procedures have been implemented for measuring the initial recombination in cobalt, and the initial and general recombination in linac beams (Niatel methid). These procedures involve measurement of the ionization chamber current at different dose rates. The initial recombination is estimated by extrapolation to zero dose rate. 


Claus Erik Andersen
Senior researcher
DTU Health Tech
+45 46 77 49 12


Christina Ankjærgaard
Head of Dosimetry, senior researcher
DTU Health Tech
+45 93 51 19 80


Mark Bailey
R&D Engineer
DTU Health Tech
+45 93 51 14 80