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3.8. Evaluation of a dynamic study of brain perfusion

With the help of this examination we obtain qualitative information about the patency of large intracranial vessels, resp. other gross abnormalities of the intracranial circulation, and quantitative information on the relative perfusion of both cerebral hemispheres.

Data storage

The patient is lying on his back, the camera detector equipped with a collimator with high sensitivity is placed above the cranium in the AP-projection. Care must be taken to ensure that the sagittal plane is exactly perpendicular to the plane of the detector. Nasus-meatus connectors ac.ext. runs vertically. Using a point source (pointer), make sure that the vertex is in the field of view of the detector.

Recommended storage mode:

64x64 matrix

Group 1: 80 shots 0.5 sec./frame

2nd group: 1 shot 120 sec.

The first group captures the actual dynamics of perfusion, the static image forming the 2nd group is not mandatory, but it is suitable for automatic definition of the ROI of hemispheres in the program. We start saving data immediately after intravenous application of a 99m Tc bolus with an activity of approx. 600-800 MBq.

Study evaluation

After calling up the scintigraphic study in the basic menu of the OSTNUCLINE system, we will start a comprehensive program PERMO - brain perfusion .

Visual evaluation of images

The program first displays a series of art images (along with the appropriate time intervals) and offers them for preliminary verbal evaluation - either by implicit normal formulation " On scintigraphic images of bolus passage through the cerebral circulation can not differentiate occlusion of large cerebral vessels ", or free text.

Defining the areas of interest of the hemispheres

This is followed by the automatic delineation of areas of interest in the cerebral hemispheres. For this purpose, the program will use the last (static) image of the study, if it has been uploaded according to the above recommendation and has a sufficient information density; otherwise, the necessary picture is obtained by summing the whole study. First, a vertical axis of symmetry is automatically created in this image, which can be moved left and right with the "left" and "right" commands, if necessary. After agreeing on the y- positions of the symmetry axis, the image is flipped (in the computer's memory) around this axis and summed, the center of gravity of the formed left + right hemisphere is found and the hemisphere boundaries are searched in polar coordinates starting at this center of gravity. Thus automatically created The ROI is displayed in the right hemisphere and is offered for review and, if necessary. manual modification (care is taken not to include arrow raft structures, vasa interhemispherics, basal structures and calva). After agreeing with the axis of symmetry formed regards n tic ROI in the left hemisphere.

Mathematical processing of curves

From the thus defined ROIs of the right and left hemispheres, the program then creates curves of the time course of radioactivity in the hemispheres. On the sum of these curves, the program automatically (with the possibility of manual modification) determines some significant points: the point of arrival of the activity, the point of maximum, the point of the interface of early and late arterial phase and the end point of the first pass of the radio indicator. The images corresponding to the significant phases thus determined are then summed and stored in the SAVE AREA. The display shows images of the early arterial phase and the late arterial phase, which are offered for visual evaluation of the perfusion of the cerebral hemispheres. The preliminary text of the visual evaluation can be modified and supplemented, for example, with the specification of sections of vessels with occlusion or susp. occlusion. The images together with the evaluation text are photographed for documentation.

This is followed by quantification of the curves from the left and right hemispheres to compare the perfusion of both hemispheres. First, these curves are corrected for the dead time of the camera-computer system. On the curves of the right and left hemispheres, the points of arrival of activity and points of maximum are then determined automatically (with the possibility of manual correction), the curves are integrated between these boundaries and the index of relative flow through the left and right hemispheres is calculated . NORM l the index range is from 0.9 to 1.06 (however recommended verification on a group of patients). The color-coded right and left hemisphere flow curves, along with the relative perfusion index value and maximum times, are displayed on the display from which they are photographed.

Final protocol

The display then summarizes the prominent images, curves along with the value of the perfusion symmetry index. At the bottom of the display, the text of the verbal evaluation is displayed, which can be edited, modified or inserted and the conclusion and signature of the evaluating physician. The text prepared in this way is then printed together with the images, curves and quantitative parameters in the final report:

Computer evaluation of dynamic scintigraphy of brain perfusion
Visual evaluation: After intravenous application of 99m-Tc on scintigraphic images of bolus passage through the cerebral circulation, we observe a good and symmetrical perfusion of both cerebral hemispheres, without occlusion of large cerebral vessels.

Conclusion: Visual evaluation of sequential scintigrams and quantitative analysis of the curves indicate good and symmetrical perfusion of both cerebral hemispheres.

PERMO program structure

The PERMO program consists of the following separate parts:

PERMO 1 - display of a series of images, visual evaluation
PERMO 2 - automatic definition of ROI of hemispheres, creation of curves
PERMO 3 - summation of images of early and late art. phase, verbal evaluation of
PERMO 4 - quantification of curves, calculation of index relat. hemisphere perfusion, protocol printing

Occupancy of SAVE AREA after the end of the PERMO program:

SA 1 - curves of the left and right hemispheres
SA 3 - painting of early art. phase
SA 4 - painting of late art. phase

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