Standardization of Aquisition and Postprocessing of Perfusion Study
Rationale
The use of perfusion and dynamic contrast agent enhanced MRI allows new insights into the physiology and pathophysiology of pathological processes of the brain. The beyond the morphological characterization achieved data may allow for a better refinement of differential diagnosis as well as important information regarding patient management. The dominant dynamic Gd enhanced techniques utilized in the brain are T1-weighted dynamic contrast-enhanced (DCE) MRI and the T2* weighted dynamic susceptibility contrast (DSC) MRI.
Gadovist with its unique combination of high relaxivity and high Gd concentration shows features which might be of benefit for the performance and results of perfusion MRI techniques. Early studies in volunteers have shown that the high concentration is beneficial for the assessment of T2* perfusion measurements.
One of the great challenges in perfusion imaging is the inconsistency in the acquisition of perfusion data, especially in DCE MRI and the complexity of the different available post-processing strategies.
DCE MRI data undergo a pharmacokinetic analysis extracting a number of parameters reflecting different physiologic or pathophysiologic tissue characteristics. There are various pharmacokinetic models that have been used to analyse the DCE MRI data which extract different parameters but also require different acquisition schemes and contrast media injection strategies.
Of the various pharmacokinetic models, the one from Tofts and Kermode (1) is the most popular. Other strategies to assess the perfusion data include the first-pass bolus technique with the assessment of peak enhancement, time-to-peak rate or just rate of enhancement.
To assess the complex dynamic data sets, several software tools have been used and presented of the last couple of years – the majority are institutional self-developed tool, however recently several commercially available programs came on the market.
As there are several studies on the use of Gadovist as contrast media for perfusion and T1-dynamics currently planned and initiated, there is a need for a centralized organization and assessment of these studies.
To achieve reproducible and comparable results and to allow the pooling of the results from different studies, the following prerequesites will be assessed in the SAPP Study protocol:
- A harmonization of the sequences – type of sequence, temporal resolution, number of repetitions etc. - to be used for data acquisition
- A standardization of the injection strategies- amount of contrast media, use of power injection, injection speed, saline flush – specific for the use of Gadovist
- To establish and continuously expand a “Perfusion Platform/Database” including source data of different study populations in a homogeneous data quality allowing for secondary analysis/postprocessing
- To establish a standardized data analysis including postprocessing of raw data, pre- and postprocessing using a standardized and tested software tool
- Development of reproducible and comparative parameters for disease assessment.
As there are no standards for perfusion and T1-dynamic assessments available so far, the proposal has different objectives focusing on the acquisition, the management and the post-processing of the imaging data. Beside experimental and theoretical work, volunteer studies and clinical studies of different indications (e.g. brain tumors, stroke and dementia) will be integrated.
Data management and centralized reading of data including the quality assessment will be partly performed by MEDIRI and MEDIDATA as contract research organizations.