NLST Images -- General Details
Dates
The Study Dates are fictitious. While appearing real, they are coded to represent the 3 screening years:
- 19990102 -- Screening Year 0
- 20000102 -- Screening Year 1
- 20010102 -- Screening Year 2
Patient Identifiers
The Patient Identifiers (PIDs), in DICOM tag (0010, 0020) Patient ID, are 6 digit random numbers assigned by IMS. They are called IMS-Global-IDs. PIDs beginning with '1' are LSS images; those beginning with '2' are ACRIN images; examples:
- 101337 is an LSS PID
- 208344 is an ACRIN PID
Prior ACRIN and LSS PIDs may be found in 2 DICOM tags: (0010, 1000) Other Patient IDs and (0013, 0040) Clinical Trial Subject ID. These prior-PIDs are random 4- or 5-digit (ACRIN) or 6-digit (LSS) numbers that contain no screening site information; the LSS prior-PIDs may have leading zeroes which may or may not appear unless specified that they do so; examples:
- 2542 is an ACRIN prior-PID
- 18519 is an ACRIN prior-PID
- 022921 is an LSS prior-PID that may also be rendered as 22921
Patient Names
Patient Names appearing in DICOM tag (0010, 0010) are a construct from the participant's prior PID concatenated with a caret and the string 'ACRIN' or 'LSS'; examples:
- 2542^ACRIN
- 18519^ACRIN
- 022921^LSS
Series Descriptions
The original Series Descriptions, if present, were often vague and/or, at best, inconsistent.
New Series Descriptions consist of 11 coded comma-separated values, listed below. Code value descriptions may be found in the attachment Series-Description-Details.xlsx.
- (1) Screening Year
- (2) Image Type
- (3) Manufacturer
- (4) Scanner Model
- (5) Convolution Kernel
- (6) Reconstruction Diameter
- (7) Slice Thickness
- (8) kVp
- (9) mAs*
- (10) Effective mAs*
- (11) Pitch*
* In order to calculate 'effective mAs' (=mAs/pitch), one needs to first determine mAs and pitch. Understanding both of these require extensive reading of manufacturer DICOM conformance statements and explanations from the manufacturers. Values neede to determine mAs and pitch are sometimes stored in private attributes. Discussions with manufacturers' engineers allowed us to interpret those private attributes and extract the information necessary to to determine effective mAs, mAs, and pitch. Extractions were made prioir to the removal of DICOM private tags because some contained protected health information (PHI).