Transpl

3.5. Comprehensive evaluation of dynamic scintigraphy of a transplanted kidney

Dynamic scintigraphy of the transplanted kidney is used for qualitative and quantitative evaluation of perfusion and functional ability of the transplant, its drainage and kinetics of the upper urinary tract . The computer evaluation of a dynamic study of a transplanted kidney is largely analogous to that of dynamic scintigraphy of the kidneys - we therefore recommend that you first study Chapter 3.4. The more significant differences (apart from the difference in the number of kidneys) are mainly in two aspects :

A comprehensive mathematical evaluation of this dynamic study includes the following main points :

We perform the examination lying down in the front projection, the scintillation camera detector is focused so that the transplanted kidney is just below half of the visual field (in the lower part of the visual field there is a sufficient reserve for imaging the bladder). Prepare a bolus of the appropriate radioindicator *) with an activity of approximately 100-300 MBq ^99m Tc-DTPA or MAG-3 into the syringe .
*) If we want to determine the absolute value of kidney function (clearance or glomerular filtration; ERPF, TER) by the method of blood sampling, we follow the instructions given in the note to the acquisition part of the program for evaluating dynamic scintigraphy of the kidneys.

Specify the position of the detector by applying a point source (or a syringe with ready activity) above the symphysis before application - on the monitor screen or persistent oscilloscope, this source should be displayed about 5-10 cm above the lower edge of the field of view so that the entire transplant and bladder.

For precise positional adjustment (especially in the case of an atypical location of the kidney), the method of pre-application of a small amount of radioindicator (2-3 MBq - does not significantly affect the dynamic study itself) is recommended, which makes the transplant visible on the camera monitor after 2-4 minutes. kidney, which we then set to the field of view without any problems.
We then quickly apply the indicator as a bolus (a three-way valve is advantageous) and at the same time we start alternating a dynamic scintigraphic study.

The recommended storage time is 30 minutes. However, if we see a sufficiently fast passage of the radio indicator on the display during storage and we do not need an accurate determination of the global function by blood-curve analysis, the examination can be terminated earlier, eg in the 20th minute. If, on the other hand, we observe the retention of the radioindicator, it is appropriate to apply a diuretic (furosemi d ) in 15.-20. minute (we will write down the time of diuretic application) and continue the storage until 30.min. When evaluating the study, we then evaluate the retention response to the diuretic.

If urine leaks into the peritoneal cavity (urinoma formation) are suspected, we also accumulate:

In this late image (due to the already low activity of the body background) or. urinary deposition in the abdominal cavity is clearly visible.

After calling up all parts of the scintigraphic study (perfusion group, functional + excretion group, or late static images) in the basic OSTNUCLINE system, we will start a comprehensive program TRNDYN - a dynamic study of a transplanted kidney .

First, a series of appropriately absorbed images (together with the values ??of the respective time intervals) are taken on the screen, capturing the passage of the radioindicator through the vascular system, then the distribution and accumulation of the radioindicator in the transplanted kidney and then its gradual excretion into the bladder. If you were on a Tradan and preset before starting the program and stills late stages will also be displayed.

According to the displayed images, it is possible to choose a preliminary verbal evaluation , both as an implicit standard formulation of a normal evaluation , e.g.

"After intravenous administration of tracer shows
conventional manner abdominal aorta and iliac arteries, then
then the well-perfused kidney transplant.
In the course of the radiotracer well concentrated at the kidney,
subsequently sufficiently rapidly excreted into the bladder.

Visual evaluation of sequential scintigrams as well as quantitative analysis
of radioactivity curves indicate good perfusion and
transplant function , rapid transit through the parenchyma and free drainage of the hollow
system. There are no signs of incipient rejection.

so non-standard text (fig ....). A series of images together with a verbal evaluation can be printed for documentation, but this is usually not necessary, as significant images are included in the resulting protocol.

Illiac artery ................ ROI 1
Transpl. kidney ........... ROI 2
Parenchyma .................. ROI 3
Tissue background .......... ROI 4
Urinary bladder .......... ROI 5

Optional:
Blood-pool (if visible) ... ROI 6

For the area of ??interest ROI 1 Art.illiaca (and also possibly for ROI 6 of the bloodstream - blood-pool) we will use the images immediately after the arrival of the activity. As ROI1 we mark a sufficiently wide area including art.illiaca ext. and surroundings - creating a real "noodle" ROI art.illiaca the program will do it automatically in the next step (see below).

In the images of the parenchymatous phase we also mark the whole transplanted kidney (ROI 2) and later images of the excretion phase are used to mark the parenchyma (ROI 3) - these ROIs will be moon-shaped, while the inner part avoids the pelvis and urinary tract, whole kidneys. Tissue background (ROI 4) is characterized by a crescent-shaped area near the bottom outside corners s borders renal parenchyma - we make sure that we did not include part of the kidney, vascular structures or efferent urinary tract. In the last images we will mark the ROI 5 of the filled bladder.

If we want to calculate the absolute function of the kidney by the method of analysis of the decrease in radioactivity in the blood, or to perform a deconvolution transit analysis, it is necessary to mark the region of interest ROI 6 representing the blood pool. Since the heart area is usually not in the field of view, the aortic area can be used in an emergency (it is completely suitable for the calculation of transit functions and times, but it can lead to certain deviations to determine the function - it is necessary to verify!).

The program creates curves of the time course of radioactivity from the marked areas of interest and performs a correction on the tissue background.

Before the actual mathematical processing of dynamic curves, the program asks what kind of sequential scintigraphy of the kidneys it is: whether it is an examination of glomerular filtration (using ^99m Tc-DTPA), or an examination of tubular function (using ^99m Tc - MAG 3). According to this answer, the performance of the respective calculations is adapted and the terminology of the calculated parameters is generated.

The mathematical processing of the curves follows. At all stages of processing below, the program first asks if we want to execute them, and they are executed only if the answer is yes. This saves evaluation time in cases where we are only interested in some parameters, or only visual and qualitative data.

If a fast group of images capturing the perfusion phase has been recorded, renal perfusion can be analyzed (optionally). The initial (perfusion) phase of the art curve is displayed. illiaca and kidneys, where it is possible to set the scale of the display in the horizontal direction (expansion-compression) for optimal presentation of perfusion dynamics. On perfusion curves are then automatically (with r in towers correction) indicates point of arrival of the radiotracers, the first peak of the bolus flow, the end of the peak and the "valley" of the separating plates and parenchymal perfusion phase nefrografické curve. In addition to the time parameters and the ratio of peak height and "salary", important perfusion indices are calculated (the principle of calculations and the relevant formulas are given in Fig. 3.5.1):

Hilson's perfusion index based on the proportion of integrals (areas) of the ascending parts of the curve art. illiaca and kidney quantifies the blood supply to the graft in relation to the blood supply to art.illi ca, which supplies the kidney (Fig. 3.5.1a).
From the kidney curve itself, the Washid perfusion-flow index is calculated , which, based on the ratio between the descending and ascending arms of the first-pass bolus, quantifies the portion of the blood-borne radiolabel that flows through the kidney and continues is filtered by the kidney (Fig.3.5.1b).

Perfusion curves together with the calculated perfusion parameters are displayed and can be printed graphically (however, we do not normally perform this printing, perfusion indices are included in the final report).

To assess the excretory activity of the transplanted kidney, the important parameters are the time of reaching the maximum and the value of the half-life of the radiolabel excretion from the whole kidney and parenchyma. On the nephrographic curves of the whole kidney and parenchyma (generated from ROI2 and ROI3), the point of maximum and the start and end point of the section for quantification of kidney excretion are automatically defined (with the possibility of manual modification). This section with e method of least squares interpolates the exponential functions and the fit graph is plotted. Counts time highs and half excretion radiondikátoru of kidney and parenchyma.
If we have a blood pool curve and we want to do a deconvolution transit analysis, we can use the same method as for dynamic kidneys to perform a mathematical linearization of the curves of the whole kidney and parenchyma - the purpose is not to determine a separate function, but only subtraction of vascular background from these curves.

If we have marked the area of ??interest of the bloodstream (ROI6) and we have a blood-pool curve, mathematical analysis of the rate of decrease of the concentration of nephrotropic radioindicator in the bloodstream can determine the clearance and le dvina (ie GFR, TER or ERPF - according to the radiopharmaceutical used) in the same way as for dynamic renal scintigraphy - we refer to chapter 3.4. If we do not have a blood pool curve, kidney function can be approximately determined by an empirical sampling method ( according to Buebeck) based on the relationship between the applied activity and the activity of a blood sample (plasma) taken at 20-30 minutes.

The clearance results are shown on the display along with the color-coded nephrographic curves of the entire kidney and parenchyma and the bloodstream curve (can be printed for documentation).

If a bloodstream or aortic curve is available (quite sufficient for this purpose), deconvolution analysis of nephrographic curves with a blood-pool curve can be performed in the same way as for dynamic renal scintigraphy. We obtain the transit functions of the whole kidney and parenchyma, which model the passage of a bolus of a given radioindicator through the parenchyma and the hollow system in a situation if we applied this bolus directly to the art. illiaca.

Three significant time moments, characteristic of the dynamics of the radiolabel passage through the kidney, are subtracted from the transit functions:

The minimum transit time (beginning of the decrease in the transit function) indicates that the radio indicator has already passed through the kidney (or parenchyma) and begins to throw. The mean transit time (at the point where the transit function is halved) indicates the time taken for half of the input amount of the radio indicator to pass through the kidney (or parenchyma). The maximum transit time (the point where the transit function drops to practically zero) indicates the time during which all the input radio indicator has already passed through the kidney or a given part of it.

Transit functions and times are calculated for the entire transplant. kidney, both for parenchyma and pelvis. This makes it possible to assess whether any prolongation of the radiolabel transit through the kidney is already at the glomerular and tubular level, or is caused by dilatation of the pelvis or obstruction of the urinary tract.
The transit curves of the whole kidney and parenchyma are displayed in a clear graph together with the values ??of transit times, from which we can infer a possible prolongation of radioindicator transit by individual parts of the transplanted kidney (for documentation we can print it out). Details are given again in chapter 3.4.

Based on the analysis of sections of curves in the quantification of perfusion, and the half-excretion is nasumují relevant images and thus create images of the transplanted kidney (together with the vascular system and bladder), in perfusion, parenchymal and early and late excretory phase, wherein the bottom of the screen offering to control and editing the text of the visual evaluation of these images. If static images of late phases have also been loaded and preselected before starting the program, they will also be displayed for visual assessment or urinoma.

Nephrographic curves are also displayed together with a question about or. application of diuretics. If the diuretic has been applied, enter the time of its application. The color-differentiated nephrographic curves of the entire kidney and parenchyma, together with the intersecting curve of the urinary bladder , are magnified on the display . A significant vertical line indicates the moment of diuretic application. In the text of the visual evaluation, which is offered for editing at the bottom of the screen, we can assess the shape of the nephrographic curves, including possibly. diuretic responses.

For a comprehensive assessment of the success of kidney transplantation, prognosis and effective therapy of possible pathologies, it is useful to perform dynamic scintigraphy repeatedly at appropriate time intervals. It is best to perform the first examination early enough (already on the 1st or 2nd day after transplantation) to obtain reference values. For an objective assessment of the normalization of physiological and pathological processes of development is sometimes more important time change function and perfusion parameters than their currently zjiště n s values. For easier assessment of time trendsFor perfusion and functional parameters, the program can save the current values ??of these parameters to a file for each specific examination. The display then shows graphs of the time dependence of individual parameters, so that the days of transplantation are marked on the horizontal axis and the values ??of perfusion and functional parameters examined on these days are plotted on the vertical axis. In the text box, we can respond to these trends by verbal evaluation or. for pathological c hairstyle.

Finally, a summary image is displayed on the screen containing images of the transplanted kidney, vascular structures and bladder in significant phases of the dynamic study (images of perfusion and parenchymatous phase, early and late excretion phase), perfusion curves and nephrographic curves (or transit functions). Below them is an overview of the most important quantitative parameters of perfusion and functions calculated by the program. At the bottom of the screen is the text of the verbal evaluation, which can be modified and supplemented. This t EZ applies to text "Conclusion", was generated when the standard formulation; otherwise we will insert the text of the final evaluation here, including the doctor's signature. Finally, the final report is printed (in the required number of copies)containing significant images, curves, calculated parameters and verbal evaluation, including the conclusion and signature of the doctor (Fig.3.5.2):

Department of Nuclear Medicine, University Hospital Ostrava Date: .............. Name of patient: ....................... . Birth certificate number: .........................
Mathematical analysis and complex evaluation of dynamic functional scintigraphy of a transplanted kidney

Evaluation: After intravenous administration of a radioindicator, the abdominal aorta and iliac artery are imaged in the usual way, followed by a well-perfused transplanted kidney. In the further course, the radiolabel is well concentrated in the kidney, then excreted into the bladder quickly enough. Conclusion: Visual evaluation of sequential images and quantitative analysis of the curves of the passage of the radio indicator indicate good perfusion and function of the graft , rapid transit through the parenchyma and free drainage of the hollow system. There are no signs of incipient rejection.

TRNDYN 1 - display of series of images, verbal evaluation, marking of ROI, creation of curves
TRNDYN 2 - thematic processing of curves, quantification of flow, clearance and excretion
TRNDYN 3 - Laplace deconvolution, calculation of transit functions and times
TRNDYN 4 - summation of images of secretory and excretory phase, verbal evaluation of
TRNDYN 5 - analysis of long-term time trends of
TRNDYN 6 parameters - display of results, text editing, report printing

At the same time, this structure shows how to proceed when the calculation is interrupted or when the program is restarted in order to repeat a certain part of the calculations. E.g. to change the texts of the verbal evaluation it is enough to run TRNDYN5, to repeat the calculation of the perfusion parameters and the function we start TRNDYN2 (after which TRNDYN3 and 4 can be omitted and continue by running TRNDYN6).

SA 1,2,3 - ROI, curves
SA 10 - image of perfusion phase
SA 11 - image of secretory phase
SA 12 - image of early excretion phase
SA 11 - image of late excretion phase