[en] Isomer excitation by gamma-gamma' reactions and aluminium oxide thermoluminescence dosemeters (TLDs) have been used to monitor bremsstrahlung from the 4 MeV electron beam of a linear accelerator type LPR4 produced on a 0.9 mm Pt converter foil. Natural indium and osmium as well as TLDs have been irradiated at different distances (2-11 cm) and angles (0 deg.-90 deg.). Dose rates measured by TLDs were 5-110 kGy.h^-1. Isomer excitation of ¹¹⁵In (half-life 4.5 h) was used for monitoring bremsstrahlung of energies above 1 MeV, while that of ¹⁸⁹Os (half-life 5.8 h) extended the available range down to 200 keV. Isomer production yields measured by gamma spectrometry and found to be about 10^-19-10-18 Bq per nucleus were calibrated against dose rate. A graphical method based on a semiempirical formula was used to evaluate the bremsstrahlung flux as well as the dose rate from the activity of isomeric monitors with uncertainties below 20%. The method is simple, of linear response in a large scale, independent of temperature, and able to monitor extremely high gamma intensities. (author)