An online method for functional monitoring and follow-up of treatment progression of a therapeutic modality based on Blood Oxygenation Level-Dependent (BOLD) magnetic resonance imaging (MRI). The therapeutic modality is applied to a disease or disorder treatable by local embolization, meaning by therapeutic introduction of a substance into a blood vessel in order to occlude it, such as some malignant and non-malignant diseases, or by recanalization, meaning a treatment leading to photodynamic reopening of previously occluded blood vessels like in cardiovascular disorders. The treatment involves a sensitizer drug which accumulates in the tissue of interest, and upon excitation by the appropriate sensitizing radiation, initiates local oxygen consumption or depletion. The change in the oxygen level result in changes in BOLD-MRI contrast. This technique can be used to in vivo, real time evaluation of response to treatment, during the sensitized treatment. The method is preferably applied to photodynamic therapy (PDT).
In this method a BOLD weighted MR-image of the target region of interest within the patient's body is generated at time t0. Then a sensitizer is administrated to the patient and the target region of interest within the patient's body is irradiated with the appropriate sensitizing radiation while the patient is placed in the magnetic field of an MRI spectrometer and is subjected to continuous MR imaging. Next a sole or a plurality of T2* weighted sequential BOLD MR images during and/or after irradiation are generated (time t). The data of time t0 and time t are being processed while generating a color-coded difference or ratio map on a pixel by pixel basis. This map is superimposed on the map generated at time t0 to obtain a composite image.