Fieldmaps intended for multiecho task fmri

Software Support
1

Hi all,

I am using dcm2bids 3.1.0 for converting DICOMs and have a question regarding the declaration of multiecho (ME) task (bold) dicoms and how to relate fieldmaps to them. The question simply is, do you relate the fieldmap to each echo (4 in my case) or only to one and how do you properly note it in the config file. Currently I assume that you relate the fieldmap to each echo, by using the same id for each of the 4 task echoes, which looks like this:

    {
        "id": "task_rest",
        "datatype": "func",
        "suffix": "bold",
        "custom_entities": "task-rest_dir-AP_echo-1",
        "criteria": {
            "SeriesDescription": "*rfMRI_REST_ME_AP*",
            "EchoTime": 0.0126,
            "ImageComments": "*Unaliased MB4/PE4/LB SENSE1*"
        }
    },
    {
        "id": "task_rest",
        "datatype": "func",
        "suffix": "bold",
        "custom_entities": "task-rest_dir-AP_echo-2",
        "criteria": {
            "SeriesDescription": "*rfMRI_REST_ME_AP*",
            "EchoTime": 0.02916,
            "ImageComments": "*Unaliased MB4/PE4/LB SENSE1*"
        }
    },
    {
        "id": "task_rest",
        "datatype": "func",
        "suffix": "bold",
        "custom_entities": "task-rest_dir-AP_echo-3",
        "criteria": {
            "SeriesDescription": "*rfMRI_REST_ME_AP*",
            "EchoTime": 0.04572,
            "ImageComments": "*Unaliased MB4/PE4/LB SENSE1*"
        }
    },
    {
        "id": "task_rest",
        "datatype": "func",
        "suffix": "bold",
        "custom_entities": "task-rest_dir-AP_echo-4",
        "criteria": {
            "SeriesDescription": "*rfMRI_REST_ME_AP*",
            "EchoTime": 0.06228,
            "ImageComments": "*Unaliased MB4/PE4/LB SENSE1*"
        }
    },

The associated fieldmap is described as follows:

    {
        "datatype": "fmap",
        "suffix": "epi",
        "custom_entities": "task-rest_dir-AP",
        "criteria": {
            "SeriesDescription": "*rfMRI_SpinEchoFieldMap_AP*"
        },
        "sidecar_changes": {
            "IntendedFor": "task_rest"
        }
    },
    {
        "datatype": "fmap",
        "suffix": "epi",
        "custom_entities": "task-rest_dir-PA",
        "criteria": {
            "SeriesDescription": "*rfMRI_SpinEchoFieldMap_PA*"
        },
        "sidecar_changes": {
            "IntendedFor": "task_rest"
        }
    },

Is that correct?

Thanks in advance!

Bests,
Philipp

2

Dear @galambda,

Looking at this conversation (with some of the best multi-echo experts) you only need to link the fmap to the first echo.

Hope it helps.
Best,
Arnaud

3

Dear @abore ,

thank you very much for the helpful response! I will proceed accordingly.

Bests,
Philipp