Cardiac Segmental Perfusion Analysis

If your image time-series consists of a set of images showing the passage of a bolus of contrast agent through the myocardium, you can perform segmental perfusion analysis. The perfusion parameters will be assessed for each cardiac segment. You will first need to defined the endo- and epicardial borders at all time points, and set up the segments.

You will also need to provide an additional ROI at every time point that outlines the blood pool in the left ventricle, as illustrated below:

Additional ROI needed for perfusion analysis, outlining the blood pool in the left ventricle. This is needed to calculate the arterial input function. This ROI is needed at every time point in the time-series of images.

Select the "Cardiac Perfusion" tab in the Cardiac Segment toolkit:

• . Select this check box if you want to correct the signal saturation that occurs in T₁-weighted MR images. If you do not select this, the contrast agent concentration will be assumed to be proportional to the image signal intensity change. If you do select this option, this will bring up the following parameters to set:
  • You can do the correction by setting the pre-contrast T₁ relaxation time of blood. Set the relaxation time of whole blood in milliseconds. You should use literature values, for example 1650 ms at 1.5 Tesla, or 2020 ms at 3.0 Tesla.
  • You can do the correction by entering a calibration factor (fully-relaxed signal intensity). This value is output whenever you run a perfusion analysis while performing the correction by setting the pre-contrast T₁ relaxation time of blood. You can use the calibration factor from a previous analysis done on the same subject if the scanner has not recalibrated between scans. For example, in a stress/rest protocol, you can perform an analysis of the stress perfusion using the relaxation time of blood for calibration, and then run the analysis of the rest images using the calibration factor found from the stress images.
  • TRec (saturation recovery time). The analysis assumes that you are using a saturation-recovery pulse sequence. Enter the recovery rime in milliseconds.
  • Flip angle. Enter the readout pulse flip angle for the pulse sequence, in degrees.
  • Number of lines to centre of k-space.

• Time between image frames. Jim does not automatically detect the time at which each image frame is acquired. Instead, it assumes that the image frames are equally-spaced in time. This time spacing is normally the nominal or average R-R interval. Set this is milliseconds.

• Image frame at contrast arrival. This is the image frame number (numbered from 1) at which the contrast agent is first seen in the blood pool in the left ventricle.

• Model. You can fit either:
  • A one-compartment (single-exponential residue function) model. The output parameters are plasma flow (F; units: ml/min/ml), distribution volume (vd; units: %) and mean transit time (MTT; units: seconds).
  • A Fermi residue function model. The output parameter is the plasma flow (Fp; units: ml/min/ml). If you choose the Fermi residue function model, you must also specify the image frame (time point) number at which the minimum in signal intensity occurs between the first-pass peak and the first recirculation peak. This is used to 'crop' the data so that only that portion up to the recirculation is used in the analysis.
• Manually specify tissue lag. Jim will automatically attempt to determine the time lag between the arrival of contrast agent in the left ventricle and the arrival in the myocardium. However, if the results are unsatisfactory, you have the option to set the lag manually. Select the check box, and alter the lag using the spinner. You can fix the lag anywhere between zero and six image frames.

For a text report, the table will be in the form of a comma-separated list of values.