DFT TAC file format

DFT is a multi-purpose ASCII data file format for regional tissue time-activity curves (TTACs), blood or plasma TACs (PTACs, BTACs), and fractions of authentic tracer and its metabolites in plasma. Analysis tools developed in TPC can read DFT files (as well as a few other TAC formats, including PMOD CRV files). Tools for processing TAC files in DFT and other formats are downloadable in TPC download pages.

Use program tacformat to change TAC file format.

Specifications

Datafile can contain one or more lines, which represent the separate samples (time points); lines end with line feed character. First one or two columns contain the sample time or frame start and end times, respectively. The next one or more columns contain the numerical sample values measured at the specified time. Columns are separated with any number of spaces or with a single tabulator (TSV format). File must contain only a single type of column separator.

Missing values or strings are represented with a single "." (period), or in TSV format also an empty field represents missing value. Data column widths can be varied.

There are no restrictions for the name of file, but for clarity, extensions .dat or .dft are recommended.

Title lines

Four (4) title lines include information about names and sizes of regions and the measurement units.

As an identifier of file type, DFT files must start with string DFT. After the identifier, the first title line contains the names of regions.

The second title line contains an identification string for the study, e.g. study number, which may be maximally 8 characters long. Following that, hemisphere or other secondary name for each (region) curve must be specified (specified as missing, if necessary).

The third title line contains the unit of measured numerical values (usually string kBq/mL), followed by the planes (slices) where regions were drawn, or other preferred type of description for the regions.

If spaces are used as column separator, the name fields obviously cannot contain any space characters; additionally the name fields should be maximally 6 characters long.

Fourth title line starts with the string "Times", if frame start and end times are stored (PET data), or "Time", if only sample measurement times (plasma data) or mid times of PET frame are stored. After that, time unit is provided in parenthesis, as (min) or (sec) or (s). And after that, the volumes of regions in units mm3 (= uL). Alternatively, strings Times and Time can be replaced by Distances or Distance, and the units with strings (um) or (mm); these are mainly used for technical purposes, e.g. in FWHM determination.

Weight column

Columns which have been named as weight are not processed as other TAC columns, but are considered to contain relational weights for different time frames in model calculations and in fitting of mathematical functions to data.

Simple files

All programs must be able to read also files with no title lines, containing only sample time (or mid time of PET frame) and the numerical values (usually blood or plasma data, or parent fractions). In this case, programs should assume that times are minutes, unless units are given as comments.

File name extension .kbq can be used to specify that radioactivity concentrations are in units kBq/mL.

Comment lines

TAC files may contain comment lines starting with character '#'. These lines may also contain useful, or outdated, information on data units etc. In bash the comment lines can be removed with command:

sed '/^#/ d' < input.dat > output.dat

, or using program rmcmnts.

It is recommended, that all programs preserve old comment lines.

Examples

DFT file containing frame start and end times, with spaces as column separator:

DFT         putam putam cereb
exam0001    dx    sin   .
kBq/ml      pl18  pl18  pl29
Times (min) 675.2 712.8 9167.1
0.00 0.25   0.00e+00 -9.18e-03 2.98e-04
0.25 0.50   1.24e+00 1.11e+00 1.43e+00
0.50 0.75   4.68e+00 4.71e+00 5.22e+00
0.75 1.00   1.21e+01 1.15e+01 9.87e+00
1.00 1.50   1.89e+01 1.97e+01 1.03e+01
1.50 2.00   2.12e+01 2.56e+01 9.36e+00
2.00 3.00   2.45e+01 2.87e+01 8.69e+00
3.00 4.00   2.37e+01 2.67e+01 8.57e+00
4.00 5.00   2.68e+01 2.92e+01 6.99e+00
5.00 10.0   2.56e+01 .        7.05e+00
10.0 15.0   2.66e+01 2.80e+01 6.54e+00
# Example data for testing purposes

The same data with mid frame times, and tabulators as column separator:

DFT1	putam	putam	cereb
exam0001	dx	sin	.
kBq/mL	pl18	pl18	pl29
Time (min)	6.752000e+02	7.128000e+02	9.167100e+03
0.125	0.00e+00	-9.18e-03	2.98e-04
0.375	1.24e+00	1.11e+00	1.43e+00
0.625	4.68e+00	4.71e+00	5.22e+00
0.875	1.21e+01	1.15e+01	9.87e+00
1.250	1.89e+01	1.97e+01	1.03e+01
1.750	2.12e+01	2.56e+01	9.36e+00
2.500	2.45e+01	2.87e+01	8.69e+00
3.500	2.37e+01	2.67e+01	8.57e+00
4.500	2.68e+01	2.92e+01	6.99e+00
7.500	2.56e+01	.	7.05e+00
12.500	2.66e+01	2.80e+01	6.54e+00
# Example data for testing purposes

Plasma and blood data is typically stored in the simple format. As an example, the plasma TAC, based on arterialized venous blood sampling, in a [¹⁸F]FDG PET study is given below in this simple format:

# Injection time: 10.05.2019 10:12:58
# Isotope: F-18
# Activity units: kBq/mL
# Time units: min
  0.333               3.222
  0.850              33.467
  1.233              19.928
  1.667              16.322
  2.050              14.923
  3.250              12.470
  5.367               9.910
  9.117               6.685
 19.000               3.071
 24.367               2.277
 29.083               1.753
 34.017               1.399
 49.300               0.725
 69.100               0.455
 82.967               0.354