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3.16. Evaluation of radionuclide splenoportography
Dynamic radionuclide splenoportography is used to examine blood flow through the portal stream and to determine of event. portosystemic short circuits (shunts).
After intrasplenic application, the radionicitor passes rapidly through the splenic vein and the vena portae into the liver and from there through the hepatic veins into the inferior vena cava and into the heart. Radionuclide splenoportography captures this flow using a scintillation camera.
Evaluation of appreciated dynamic splenoportography consists of three stages :
Acquisition of studies
We place the patient on his back under the camera so that the examined structures are in the visual field - the spleen in the lower right edge of the visual field, the liver in the lower left (or middle) part of the image and the heart and lungs in the upper part. For accurate determination of the injection site, it is advantageous to mark the contours of the spleen on the skin in the area of ??the intercostal space and cross the center of the spleen in the patient's maximum exhalation under the camera during previous static scintigraphy of the spleen. In the place of this cross, during the actual splenoportography, we apply the radioindicator again in the maximum exhalation of the patient.
Intra-Splenetic administration tracer 99 mTc-pertechnetate in a small volume (1 ml.) by thin needle and sufficiently fast (almost "bolus") to be well expressed in the first phase of the flow. At the same time, we will start saving a dynamic study that captures the flow of a radio indicator through the portal and system streams.
Recommended storage mode:
Dynamic study : matrix 64 ┤ 64, 16 bits 60 frames / 2 sec .
After calling up the required dynamic scintigraphic study in the basic menu PROCESSING, we will start the complex program SPLDYN - evaluation of dynamic splenoportography .
Visual evaluation of dynamic images
First, a series of appropriately captured images (together with the values of the respective time intervals) are created on the screen, capturing the individual phases of the radioindicator's passage through the areas: spleen « v.lienalis « v.portae « liver « systemic circulation.
Under normal circumstances, after itrasplenic application, the radiolabel passes rapidly through the v.lienalis and v.portae into the liver, where the flow slows down appropriately in the capillary bed, then flows through the hepatic veins and inferior vena cava into the heart and lungs, and then into the systemic circulation. In the presence of short circuits (connectors) of the portal and systemic flow, part of the radioindicator passes out of the liver and reaches the heart prematurely . In addition to these portosystemic shorts, we can also consider an event in a series of images. obstruction of the v.lienalis or v.portae.
In this visual evaluation, we can use either the implicit standard formulation of the normal evaluation, e.g.
After intrasplenic application of 99m-Tc, we
first observe on scintigrams the rapid passage of the radioindicator through the v.lienalis and v.portae
into the liver, without obvious porto-systemic shunts.
After the usual slowing down in the capillary bed of the liver, the
radiolabel flows out through the upper vena cava into the heart and lungs.
or the text of a pathological finding. In case of obvious pathology, we can print the images together with the text.
Delineation of areas of interest and construction of curves
To quantify the dynamics of the flow of the radio indicator through the portal and system streams, it is necessary to mark the relevant areas of interest. Using the arrows or the slider below the image, we step through the images in the study and gradually make the individual structures through which the radio indicator flows visible. Areas of interest are drawn in the order :
ROI 1 ......... vena lienalis
ROI 2 ......... liver
ROI 3 ......... heart + lungs
RO I 6 ......... tissue background
From the marked areas of interest, the program then creates curves of the time course of the passage and distribution of the radio indicator.
Quantification of radio passage dynamics
A suitable addition and refinement of the visual evaluation of the radio indicator flow may be the quantification of the flow dynamics by means of a mathematical analysis of the curves from the marked areas of interest. For curves from the v.lienalis, liver and heart regions, the time of arrival of the radioindicator, the time of the maximum , the slope ( gradient ) of the increase (the ascending section intersects the linear function) and the half-life of the escape are determined.radio indicator (the exponential function interleaves the exponential function). The calculations are optional, they are performed automatically with the possibility of manual modification of the selection of points on the curves, the resulting parameters together with the curves and graphs of interpolated functions are displayed on the screen to agree or repeat the calculation.
Images of significant flow phases
The above-mentioned analysis of the curves, in addition to the quantification of the flow dynamics, also serves to construct images of significant phases of the radio indicator flow. The images corresponding to the significant points and sections on the curves during their mathematical analysis are added together to form images of the significant phases of the radio indicator flow : v.lienalis flow , portal flow , liver flow and cardiopulmonary. flow . The program describes these images with the corresponding text and time data. In the box below we can edit or add the text of the verbal evaluation.
The upper part of the display shows images of significant phases of the radio indicator flow together with time data, in the middle part there are curves with theá results of quantification of the flow dynamics. In the box below we can edit the text of the verbal evaluation of scintigraphic images and the final evaluation - when preselecting a normal evaluation, a standard formulation of a normal conclusion is offered:
Visual evaluation of sequential scintigrams as well as quantitative analysis of
curves indicate normal flow conditions in the portal stream,
without obvious portosystemic shunts
Finally, we can print basic data such as the patient's name) , containing (in addition to the relevant images, quantitative parameters of flow dynamics, text of verbal evaluation, conclusion and signature - Fig.3.16.1.
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