acquisition variable attributes

These attributes store parameters about the acquisition. All of these attributes are optional, and have no default value defined.

1. contrast_agent - String identifying the contrast or bolus agent.
2. dose_units - String giving units of dose.
3. echo_time - Number giving the time in seconds between the middle of a 90 degree pulse and the middle of spin echo production.
4. imaged_nucleus - String specifying the nucleus that is resonant at the imaging frequency.
5. imaging_frequency - Precession frequency in Hz of the imaged nucleus.
6. injection_day - Integer giving day (1-31) of injection.
7. injection_hour - Integer giving hour (0-23) of injection.
8. injection_length - Number giving the time duration of the injection (in seconds).
9. injection_minute Integer giving minute (0-59) of injection.
10. injection_month - Integer giving month (1-12) of injection.
11. injection_seconds - Floating-point number giving seconds of injection.
12. injection_time - String giving time (and date) of injection.
13. injection_year - Integer giving year of injection.
14. injection_dose - Total dose of radionuclide or contrast agent injected (in units specified by dose_units).
15. injection_route - String identifying administration route of injection.
16. injection_volume - Number giving the volume of injection in milliliters.
17. inversion_time - Time in seconds after the middle of the inverting RF pulse to the middle of the 90 degree pulse to detect the amount of longitudinal magnetization.
18. num_averages - Number of times a given pulse sequence is repeated before any parameter is changed.
19. protocol - String description of the protocol for image acquisition.
20. radionuclide - String specifying the isotope administered.
21. radionuclide_halflife - Half-life of radionuclide in seconds.
22. repetition_time - Number giving the time in seconds between pulse sequences.
23. scanning_sequence - String description of type of data taken (eg. for MR - IR, SE, PS, etc.).
24. tracer - String identifying tracer labeled with radionuclide that was injected.