Regarding neuroimaging acquisition, CATI can support project leaders on several issues related to neuroimaging acquisition:

  • neuroimaging protocol design (selecting MRI sequences and NM tracers…);
  • proposal of a set of optimised / harmonised MRI sequences on several MRI systems (3DT1 for anatomy, 3DFLAIR for lesions, 3D multiecho GRE for R2* and QSM, diffusion MRI, functional MRI…);
  • optimisation / harmonisation of new MRI sequences;
  • update of existing MRI sequences (technical improvement or new MRI systems);
  • proposal of PET acquisition parameters (acquisition time, dynamic framing …)
  • optimisation / harmonisation of PET / SPECT reconstruction (new tracers, new systems);
  • MRI parameters and PET / SPECT reconstruction set up and validation;
  • study documentation related to neuroimaging acquisition.

CATI can be involved from the very beginning of a study, when the imaging protocol is defined in order to be able to assess the outcomes that are planned in the study (MRI sequence, NM tracer…). During this first stage, CATI can also participate or manage the feasibility study to ensure that the selected acquisition centres meet the technical requirements with respect to the sequences that have to be acquired for MRI and the reconstruction for NM.

Once the necessary sequences / tracers have been established and the MRI or NM system types are known, the neuroimaging protocol implementation is undertaken with the help of experts (nuclear or MRI physicists from collaborating teams, reference centres or the French REMI network) to better include the latest methodological and technological improvements, thus enhancing the overall quality and reliability of the study.

MRI

According to study requirements, CATI can work from existing sequences (e.g. from a previous study of the project leader or from the literature), propose already optimised sequences or manage optimization and harmonisation steps. Reference centres are identified, one for each MRI system type among the centres involved in the study, and parameter optimisation and harmonisation are undertaken. This process will become more complex and time-consuming as more system types and manufacturers are included, making the first stage and feasibility study crucial.

The aim here is to build a set of parameters for each system type that will allow reaching a compromise between optimisation for each system type and harmonisation between system types. Dummy runs on volunteers will be acquired, processed and analysed in an optimisation process to ensure sufficient quality to estimate the outcomes planned in the study. CATI will aim at harmonising acquisition parameters and acquired images according to different levels of harmonisation linked with sequence types (quantitative MRI…) or study requirements (from visual assessment to quantitative measurements).

For longitudinal studies, a longitudinal reproducibility evaluation can be undertaken if planned in the study. CATI will also consider the feasibility of a travelling volunteer study or phantom experiments, according to MRI sequences and levels of harmonisation.

CATI will prepare an acquisition guide during, with finalised information regarding sequences and acquisition procedures. For each new sequence type, quality control processes will be designed and implemented in accordance to its specific requirements.

When the protocol is ready for reference centres, parameters will be set up in all centres participating to the study and validated by CATI, in close collaboration with local radiographers and engineers. If a centre is not yet part of the CATI network, a dummy run is required and processed by CATI to evaluate that image quality is consistent. MRI system change during the study will be monitored and specific procedures may apply.

Nuclear Imaging

To minimize the site effect in multicentre and longitudinal PET/SPECT studies, CATI implements a rigorous procedure for reconstruction parameters harmonisation using phantoms. This crucial step is designed specifically for each study according to its objectives. The phantom is carefully selected based on the outcomes evaluated by the study to best replicate the requested clinical conditions. Commonly used phantoms by CATI include the Hoffman, Jaszczak, and Striatal phantoms, among others.

CATI acquires data for these phantoms from all participating centers, working closely with local physicists and engineers. From a set of pre established reconstructions from each center, various quantitative metrics are extracted. The objective is to select reconstruction parameters that minimize variability in metrics across centers. If a scanner change occurs during the study, this harmonization process has to be repeated to ensure data consistency.

Ultimately, CATI provides dedicated reconstruction parameters for each scanner at each center, specific to each study. This approach ensures optimal consistency and precision in imaging results, enhancing the reliability of multicentre and longitudinal studies.