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3.13. Evaluation of dynamic 3-phase scintigraphy of the skeleton
Dynamic (3-phase) scintigraphy of the skeleton is used to examine the perfusion and metabolism of selected parts of the skeleton, especially bone lesions (whether they are inflammatory, tumor, metabolic, traumatic ) .
A suitable osteotropic radioindicator is used , which binds to the hydroxyapatite lattice and thus is taken up in bone lesions with increased osteoblastic activity, eg metastases, fractures, foci of osteomyelitis. Currently, 99m Tc-MDP (methylene diphosphonate) is the most commonly used .
The evaluation of dynamic scintigraphy of the skeleton consists of three stages:
We place the patient under the camera so that the examined bone structures (lesions) are in the field of view. Intravenous administration radi oindikátoru upper limb vein perform sufficiently fast (almost "bolus") to be well expressed in the first phase of the flow. The radio indicator passes through the bloodstream, including the examined structures in the field of view of the camera. Simultaneously with the application, we start saving a dynamic study that captures the perfusion phase (phase 1) and the phase of radioindicator flow through the capillary vessels, including possibly. penetration into the extravascular space (phase 2). Static scintigraphy, capturing the self-accumulation of the radioindicator in bone tissue (phase 3), then follows in 2 to 4 hours.
Recommended storage mode:
Dynamic phase : matrix 64 ´ 64, 16 bits
1st group: 60 shots after 2 sec.
2nd group: 24 shots after 10 sec.
Static phase : matrix 128 ´ 128, 16 bits, preselection min. 200,000 imp.
24 hrs pi: Targeted images in AP and PA projections, or lateral (max. 10 shots) .
After calling up all parts (dynamic and static) of the required scintigraphic study in the basic menu PROCESSING, we will start the complex program OSTEODYN - 3-phase scintigraphy of the skeleton .
Visual evaluation of dynamic
and static images
First, a series of appropriately summed images (together with the values ??of the respective time intervals) are created on the screen, capturing the passage and accumulation of the radio indicator in the examined part of the skeleton during the dynamic phase . Later static skeletal scintigrams (if scanned) are displayed at the bottom of the screen , capturing the accumulation of a radiolabel in the bone tissue. If several static images were captured (images of different places and different projections), the command to select the static image of the skeletal phase that corresponds to the place and the projection in the dynamic phase will appear (Fig.3.13.1) - this image will then appear on the resulting protocol along with significant dynamic phase images.
Visual evaluation begins , and we can use either the implicit standard formulation of normal evaluation, e.g.
After intravenous administration
of 99m-Tc-diphosphonate, we
first observe a good and symmetrical perfusion of the examined skeletal parts in the dynamic phase . In the next
course, we observe the normal accumulation of the radioindicator in the skeleton,
without bearing changes.
Visual evaluation of sequential scintigrams as well as quantitative analysis of the
curves indicate normal perfusion and metabolism of the examined
skeletal parts .
or the text of a pathological finding. In the case of a positive display of the pathological distribution of the radioindicator (especially on static scintigrams), we can print the images together with the text.
Designation of areas of
interest and construction of curves
In order to quantify the relative perfusion and dynamics of radioindicator accumulation in bone lesions, it is necessary to mark the relevant areas of interest. As ROI 1, we mark in the images shortly after application a suitable part of the bloodstream supplying the examined part of the skeleton. Other areas of interest (max. 4) will then be located in the places of the examined lesions. Since we assess the relative perfusion and accumulation of the radiodicator , we mark the areas of interest in pairs (eg ROI2 Left knee , ROI3 Right knee , or ROI4 healthy bone , ROI5 lesionsetc.). Before the actual marking, we insert the names of the required ROIs at the instruction of the program ; these calls will then appear next to the relevant curves and parameters throughout the evaluation and will be printed on the final report. We implicitly use irregular regions of interest (IR), but we can also use quadrangular (RI).
From the marked areas of interest, the program then creates curves of the time course of the radio indicator distribution. The program normalizes these curves to the number of pixels, so keeping the same size of paired ROIs is useful, but not critical.
Quantification of lesion
If a fast group of images capturing the perfusion phase was successful, the relative perfusion of the lesions can be analyzed (optionally - it is important only in the case of a well-expressed phase of the first flow). The initial (ie perfusion) phase of the pair of curves of both lesions is displayed and it is possible to set the scale of the display in the horizontal direction (expansion-compression) for optimal presentation of perfusion dynamics. The points of arrival of the radioindicator and the peak of the perfusion flow of the radioindicator are then automatically marked (with the possibility of manual correction) on the perfusion curves of both lesions. Together with the time parameters, the relative perfusion index is calculated , which is calculated in [ percent ] based on the proportion of integrals (areas) of the ascending parts of the perfusion curves of both lesions . relative blood flow to each of the lesions (the method is analogous to Fig.3.4.1b).
The perfusion curves together with the calculated perfusion parameters are displayed (Fig.3.13.2) and can be printed graphically (however, we do not normally perform this printing, the relative perfusion parameters will be included in the final report).
Quantification of vascular and
extravascular accumulation in lesions
To assess the nature of the lesions (hyperemia, inflammatory process) and to interpret the osteoblastic activity of bone tissue, an analysis of the dynamics of radioindicator accumulation in vascular phase lesions may be useful . An ascending section (following the perfusion phase) is automatically defined on each of the curves (with the possibility of manual correction ). This ascending section interpolates the linear regression function (the fit graph is displayed) and quantifies the steepness (gradient) of the increase in radioactivity in [ percent increase in instantaneous activity per minute ] and the relative vascular accumulation relative to each other.of both lesions in [ percent of the sum of both lesions ] .
Note : The second phase of dynamic scintigraphy of the skeleton (following the perfusion phase) was called the vascular phase , resp. vascular + extravasular , because we do not consider the name "blood-pool phase" used in the literature to be completely adequate. At this stage, the radioindicator enters the capillary vessels and gradually penetrates (especially, for example, in inflammation) into the extravascular space. The increased value of the relative vascular accumulation parameter (or growth gradient) indicates a congestion of the respective site, or for increased penetration of the radioindicator, eg into inflammatory tissue.
Dynamic and static scintigrams
All significant dynamic and static images of the required size, together with quantitative parameters, would not fit on one panel of the screen. Therefore, before displaying the final protocol, images of significant phases of perfusion and vascular (+ extravascular) accumulation are displayed, purposefully summed up on the basis of dynamic phase analysis and provided with time data, together with static images of the third, ie skeletal phase. In the box below we can edit or add the text of the verbal evaluation. In the case of a positive display of the pathological distribution of the radioindicator (especially on static scintigrams), we can print the images together with the text.
The display shows images of significant phases of perfusion and accumulation of the osteotropic radioindicator in the skeleton, together with time data and the results of quantification of relative perfusion and vascular and accumulation of lesions. In the box below we can edit the text of the verbal evaluation of scintigraphic images and the final evaluation . Finally, we can print a report containing (in addition to basic data such as the patient's name) relevant images, the results of determining the relative perfusion and dynamics of lesion accumulation, the text of verbal evaluation, conclusion and signature - Fig.3.13.3.
|Computer evaluation of dynamic 3-phase scintigraphy of the skeleton|
evaluation: After intravenous administration of
99m-Tc-diphosphonate, we first observe in the dynamic
phase a good and symmetrical perfusion of the thigh
areas, the left knee and tibia show increased perfusion
with foci of (probably peristatic) hyperemia. In the
further course in the skeletal phase, we observe deposits
of increased accumulation of the radioindicator in the
head of the left fibula, in honey. condyle of the left
tibia and in the later. parts of the knee joint.
Visual evaluation of sequential scintigrams and
quantitative analysis of the curves indicate increased
perfusion in the left knee with hyperemia deposits and
increased accumulation of a radiolabel, indicating the
possibility of an inflammatory process around the left
knee of the above localization.
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