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Data Access

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• Imaging Data Commons (IDC) (Imaging Data)

Detailed Description

Notes:

• There are data for 984 patients but only 969 were included in the primary data analysis due to study criteria.
• Due to a missing value in the type 1 Sequence Variant DICOM tag (0018,0021), it was decided to populate the missing tag values with "NONE" (the Sequence Variant is actually unknown but "Unknown" is not a valid value for this tag).
• Case Number 120 image data has been removed due to data corruption; clinical information is still present in clinical data spreadsheets.

Date Offsets:

All dates, like the visit date, are protected by presenting just the year; however, dates are also listed as offset days from the base date. The offset dates are used as a means of protecting patient information provided by the local sites in the original data, while allowing users to determine intervals between events. The standard DICOM date tags (i.e. birth dates, imaging study dates, etc.) have been de-identified so that all patients have a baseline study date of January 1, 1960.  This falsified date represents the day patients were entered into trial database. The number of days between a subject’s longitudinal imaging studies are accurately preserved.  A patient with a study performed on January 4, 1960 means the images were collected 3 days after the base date.  For convenience, this calculation has been performed for all scans with the results inserted in DICOM tag (0012,0052) Longitudinal Temporal Offset From Event. This means an imaging study that took place on January 4, 1960 would contain a value of "3" in tag (0012,0052). 

Overview of Clinical Data

The basic data flow for legacy ACRIN multi-center clinical trials was that all clinical information provided by the local imaging sites were contained in a series of forms.  The form data submitted by local investigators to ACRIN during and after the trial, were manually encoded into the ACRIN CTMS (Clinical Trial Management System), and were cross-checked for accuracy by ECOG-ACRIN personnel. These ACRIN 6667 forms, filled out by the local sites, deliver information on imaging, clinical management of the patient and pathology/outcome variables, like dates of progression and survival, along with other critical information.  The image data was initially anonymized while uploading from the local sites through TRIAD software and archived in a DICOM database at ACRIN.

After the trial accrual had ended, the clinical data was sent to the Brown statistical center, that is funded by NCI to provide support for ECOG-ACRIN clinical trials, specifically for analysis of the primary and sometimes secondary aims of the trial. The statisticians at Brown strip all the actual dates, names and other PHI from the CTMS data and create a .csv file for each form that has selected information useful for analysis of the trial data.  A Form Dictionary file detailing all the forms used in the study accompanies the .csv data files.  Additionally, the accompanying Form Dictionary file lists each element for each form that has been selected for data retention along with a description of each form element.

Extracting clinical (non-imaging) data example:

Beginning with the Form Dictionary.csv file, select the form with the desired information needed, such as form A0.csv the patient confirmation form. Next, using the form Dictionary.csv file (e.g. 6667_A0_Dictionary.csv), find the form elements listed for A0 (e.g., A0exx, where xx is the form element number). The file lists the form number, variable name, its description or label, the type of data, and, when applicable, the option codes and corresponding text values (option code:description pairs like 1=’No’, 2=’Yes’; or 1=’Baseline’, 2=’Post treatment’) for each data element available from the form.  In the example in Figure 2, the A0 form element 31d (A0e31d) reports the days between the base date and the day of surgery for the patient.  In the corresponding A0.csv file column G lists the days between the base date and surgery for each patient.  

Figure 2: In this example of extracting clinical data, the first step is to 1) find the form from the Form Dictionary, 2) Find the desired element and description in the accompanying form Dictionary (e.g. 6667_A0_Dictionary.csv) and finally 3) extract the values from the .csv data file.

The procedure above is basically how the statisticians organized the selected data for export, but the structure of the data dictionaries and individual forms are different for each clinical trial. 

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Version 1 (Current): Updated 2021/03/05