|AstroNuclPhysics ® Nuclear Physics-Astrophysics-Cosmology||OSTNUCLINE|
|Nuclear physics and physics of ionizing radiation||Radionuclide scintigraphy|
MATHEMATICAL ANALYSIS AND COMPREHENSIVE COMPUTER EVALUATION OF SCINTIGRAPHIC EXAMINATIONS
3.1. Radionuclide ventriculography
Radionuclide ventriculography is used for a detailed examination of the dynamics of the cardiac cycle, both by visual assessment of the motility of the heart walls , as well as by quantitative analysis and in the calculation of a number of parameters of central hemodynamics. Of the quantitative parameters, it is mainly the ejection fraction of the left (or right) ventricle, end-diastolic, pulse and residual volume , cardiac output, ejection and filling rates , time intervals of significant phases of the heart revolution. To assess the motility of the heart walls, contours of the heart walls in end-diastole and end-systole, parametric images of heart rate volume and paradoxical movement, Fourier images of phase and amplitude. Regional phase and amplitude analysis can be performed . If we perform the study in the LAO projection in connection with the study in the LL projection, we will get an overview of the motility of all segments of the left ventricular wall with this combination.
The program uses a completely automatic (mathematical) delimitation of the areas of interest of the heart chamber and background, which improves the accuracy and reproducibility of the quantification of hemodynamic parameters.
After premedication with inactive Sn-pyrophosphate (to label erythrocytes 99mTc in vivo), the patient is given approximately 400-800 MBq of sodium pertechnetate 99m Tc. Connect the electrodes of the ECG-cardiomonitor connected to the acquisition computer and set the scintillation camera detector above the precordium in the LAO projection so that the left ventricle lies in the right middle part of the field of view. Select the zoom scale so that the left ventricle fills as much of the field of view as possible. If we want to quantify the right ventricle, it is necessary that this is displayed with a reserve in the left part of the field of view.
Recommended storage mode:
64 x 64 matrix , 16 bit, Study type: ECG -gated
Zoom approx. 1.5-2 ´
(otherwise individually according to the size of the heart and the field of view of the camera)
LAO projection , or and projection LL
Preset time 10 min. Pulse preselection 5,000,000
Preset number of cycles 700, Cycle elimination interval 10%
Before starting the
study, care should be taken to stabilize the heart rhythm so that
the average and current (last) length of the cycle are close;
otherwise, cycles would be incorrectly excluded. Therefore, when
preparing the study, we recommend switching to the monitoring
storage mode only after the heart rhythm has stabilized.
Then we start our own storage of the phase dynamic study of the cardiac cycle synchronized by the ECG signal. If there is a significant change in heart rate during study storage, the study should be restarted and restarted with a new stabilized rhythm.
The methodology of phase dynamic scintigraphy of the cardiac cycle gated by the ECG signal is described in detail in §4.4 "Gated dynamic scintigraphy " of Chapter 4 "Scintigraphy" of the book "Nuclear physics and ionizing radiation physics ".
Evaluation of the study
After invoking the required ventriculographic scintigraphic study using the basic OSTNUCLINE system, we start a comprehensive program VENTR - radionuclide ventriculography (its first part).
Images of end-diastole and end-systole
Images of the maximally filled ventricle (in end-diastole) and maximally emptied ventricle (in end-systole) are important both for visual assessment of chamber shape and size, for calculating ventricular volume and mainly for defining areas of interest of the ventricle and tissue background. With proper R-wave ECG synchronization, the initial frames up to about 1/4 cycle (and often several end frames) correspond to end-diastole, the end-systole is about 1/3 to 1/2 of the cycle length. However, this temporal location of ED and ES is highly variable individually, so that a flat-rate determination of the end-diastole and end-systolic phase "hard" would not always be accurate (for other systems, however, this is simply solved). In our program VENTR is the definition phase of the end-diastole and end-systole precisely adjusts the en of the actual situation at the particular heart.
The program first summarizes preliminary images of end-diastole and end-systole, calculates a preliminary heart rate image from them and constructs a preliminary volume curve from its most pulsating parts - this curve is always well "modulated", even in severe pathologies of ventricular motility. The upper and lower levels are determined automatically (with the possibility of manual shift) on this curve for the determination of end-diastole and end-systole points. The images corresponding to these curve points are then summed, normalized to each other to form end-diastole (ED) and end-systole images.(ES). This method allows completely accurate creation of these images even in the case of very poor functioning of the heart chamber, as the program finds relatively well pulsating sites on the chamber, from which the curve is sufficiently modulated to reliably determine end-diastole and end-systole.
Defining the regions of interest of the heart chamber and background
On images in end-diastole and end-systole, another important action can be taken for the complex processing of radionuclide ventriculography - delimitation of the areas of interest of the ventricles and background . This delimitation can be performed either manually or automatically in the VENTR program. For better reproducibility of the results, we recommend using automatic delineation , which based on geometric analysis of the radioactivity distribution image in most cases objectively delimits the left ventricular ROI (however, the automatically delimited ROI can be arbitrarily corrected as needed).
Automatic delimitation of the area of
interest of the ventricle
The center of gravity of the ventricle is automatically marked (with the possibility of manual correction) on the image of the end-diastole, which is taken as the origin of the polar coordinates in further calculations. In these polar coordinates, an image of the local concavity of the radioactivity distribution image is then constructed (the calculation is performed simultaneously on the ED image and on the pulse-paradox image), on which the chamber boundaries as places with increased concavity should be sharply expressed. The program then searches this image and constructs the ROI as a junction of places with maximum concavity .
Method of computer delimitation of the area of ??interest of the heart chamber.
a) In the end-diastolic image, the center of gravity T is automatically defined as the origin of the polar coordinates. The center of gravity is to cut the sections (profiles) gradually at different angles.
b), c) Two typical shapes of these profiles. From the profile curves f (x) the function of local concavity K (x) is determined; the maxima of the local concavity lie at the boundary of the chamber.
d) Quantification of the local concavity of the profile using the size of the area between the function f (x) and its secant p (x).
e) The resulting image of local concavity has significant maxima at the border of the ventricle. The heart contour (ROI) can then be defined as the junction of points with maximum local concavity.
The course of automatic delineation of the ROI of the heart chamber
a) The center of gravity of the chamber is made incisions gradually at different angles, on which the local concavity is calculated and stored in the parametric image.
b) In the finished parametric image of local concavity, places of significant maxima are searched for and a line in ROI bits is guided through them - the ROI of the heart chamber (c) is created, which is then smoothed radially and is offered to possibly. manual adjustment.
This automatically defined ROI is then displayed on the background of the end-diastole image and at the same time on the background of the concavity image. This ROI can be modified manually as needed. ROI is further confronted with a combined paradoxical-pulse image (described below), where there is a very important gap separating the ventricle from the vestibule from the vestibule with the opposite dynamics. If it happens that the originally marked ROI partially encroaches into the atrium, it is necessary to delete the overlying part and lead the upper limit of the ROI through this gap between the ventricle and atrium (however, in the VENTR program this happens very rarely, because the automatic delineation procedure image into account). At this stage, we will also know whether the entire possible dyskinetic region is included and we can add it as needed.
The automatically generated ROI of the heart chamber can be definitively corrected not only according to the
parametric image of the local concavity, but also very precisely according to the combined
Once the ROI of the
ventricle in the end-diastole is definitively marked, the ROI of
the tissue background for that vent is automatically determined.
The calculation is performed on the image of the end-systole and
the result is a "crescent-shaped" area, the outer part
of which is bounded by the end-diastolic ROI of the ventricle and
the inner part by the image of the ventricle in the end-systole.
The background ROI is avoided or structures with increased
activity. If there is not enough space inside the end-diastolic
ROI for a sufficient number of background points (this happens
with very low chamber contractility), the program will gain the
appropriate number of points from a close neighborhood outside
the ROI. Automatically defined ROI background can also be
manually modified, but the sentences Shiit is not necessary. The
resulting ROI is representative of the average tissue background
in the area of the ventricle in the ES-phase, as it closely abuts
the ventricle in the ES. Background ROI is important for correction
against tissue background of images, but mainly of curves for
calculation of EF and other parameters of central hemodynamics
If we also want to quantify the activity of the right ventricle , we mark (manually) the ROI of the right ventricle on the appropriate instruction. Again, we mark simultaneously the ED image and the combined heart rate-paradox image using well-visible dark transitions between the ventricle and the atrium. We try to avoid art. pulmonalis. The background ROI for the right ventricle is then defined automatically according to the same criteria as for the left ventricle.
Heart stroke and paradoxical image, heart contours
The images of the heart
chamber in end-diastole and end-systole give us some idea of its
contractility, but for a better assessment of the shape and
mobility of the heart walls, it is appropriate to emphasize these
walls in some way ("visibility") - to create contours
of the heart chamber . The contours of the heart wall are
constructed using mathematically generated isochromatic curves
("contour lines") on the image in end-diastole and
end-systole and are displayed together in one image with
significant color difference - the contour in end-diastole is
blue, the contour in end-systole is red (Fig.3.1.1).
Fig.3.1.1. Distinctive images of the heart revolution constructed by a program for assessing the motility of the heart walls.
Left: Images of end-diastole, end-systole, paradoxical and stroke image. Right: Contours of the heart wall in end-diastole (blue) and end-systole (red).
This is a markedly pathological case with apical dyskinesis.
Under normal circumstances (with good and isotropic ventricular contraction), the entire end-systolic contour must lie deep and concentrically within the contour in the end-diastole. With an overall reduced ejection fraction, the "depth of immersion" of the end-systolic contour within the end-diastolic contour decreases. When there is a disorder in the local mobility of the heart wall (anisotropic pulsation), the concentration is disturbed - both contours approach in the appropriate place ( hypokinesis ), touch ( akinesia ), or even the end-systolic contour intersects and emerges from the end-diastolic contour ( dyskinesia ) - Fig. 3.1.2.
|Fig.3.1.2. Typical shapes of heart wall contours in end-diastole ( ______ ) and in end-systole (...........) at different pathologies of left ventricular contractility.|
From the images of end-diastole and end-systole, important parametric images mapping the regional distribution of the dynamics of systolic-diastolic function of the heart are constructed (Fig. 3.1.1):
The stroke image SV (image of Stroke Volume) arises as the difference between the image of end-diastole and end-systole:
SV = ED - ES.
It quantifies us (in relative numbers - pulses), how much blood decreases during the contraction of the ventricles in individual places of the image, ie the local intensity of pulsation of the chamber (in this it is somewhat similar to the amplitude Fourier image). The atria are not visible in the heart rate image (there is filling - negative values), the heart chambers should normally be displayed clearly and relatively homogeneously (a small decrease in the intensity of the heart rate image inside the ventricle at the inlet site is physiological). A dark defect in the left ventricular heartbeat is a sign of reduced contractility - hypokinesia or akinesia . A brighter island separated from the rest of the ventricle by a dark transition on the pulse image is (along with the corresponding finding on the paradoxical image) a manifestation of dyskinesia.
The paradox picture arises as the difference between the pictures in end-systole and in end-diastole:
PAR = ES - ED.
In normal contractility, in the paradoxical image, the chambers must be dark (there is emptying - negative values), the atria is light. The presence of a light "island" in the dark field of the left ventricle is an unmistakable indicator of the paradoxical (opposite, opposite ) movement of the heart wall in this place - dyskinesia (Fig. 3.1.1).
The combined stroke -paradoxical image of SP is given by a suitable composition of stroke and paradoxical image, which can be achieved by using absolute values of differences in the contents of individual elements of ED and ES images, thus turning negative values into positive:
SP = ÷ ED - ES ú = ÷ ES - ED ÷ = ÷ SV - PAR ÷ .
Chambers and atria are clearly shown in this image, which is very similar to an amplitude Fourier image. Very important is the sharp dark transition between the ventricles and atria in this image (it is the transition between ventricular dynamics and opposite atrial dynamics), which allows accurate the regions of interest of chambers to be specified so that they do not interfere with the atria (as described above).
Images of end-diastole and end-systole, contours of the heart wall in ED and ES, stroke and paradox images, are cleary simultaneous displayed in the VENTR program - or we can print them graphically.
Fourier amplitude-phase analysis
Mathematical methods of Fourier analysis can be used for a completely detailed analysis of the dynamics of the heart revolution in individual parts of the heart . From a general point of view, Fourier analysis is based on the theorem, according to which each function f (x) can be expressed as a superposition of harmonic functions A.cos ( w .x) and B.sin ( w .x) with different amplitudes A, B and circular frequencies. w . Cardiac activity is periodic at time t, so we can naturally model it with the function A.cos( w .t + j ) with a fixed circular frequency w = 2 p / T determined by the period T of the cardiac cycle, where A is the pulsation amplitude and j expresses the time (phase) shift of the beginning of the decrease in radioactivity after the arrival of the R-wave, ie the phase difference between the electrical and mechanical systole. It is customary to express the phase shift j in angular units - degrees o , while the whole heart cycle (period T) is assigned 360 o . The relationship between the phase shift j in degrees and the time shift D t in seconds between the electrical and mechanical systole is
D t = T. j / 360 .
The Fourier analysis of radionuclide ventriculography can be imagined in the following steps :
|Fig.3.1.3. Principle of construction of amplitude and phase Fourier images illustrated on the example of pathological ventriculography.|
We will now briefly describe how the Fourier phase analysis of cardiac cycle dynamics is implemented in the VENTR program. When asked whether this analysis should be performed, we will answer in the affirmative especially when, according to the image of heart rate volume or paradoxical image, we suspect a regional heart chamber motility disorder. Before the actual calculation, the time course of the radioactivity in the entire field of view of the camera is first displayed and the end point of the phase analysis is automatically defined on it (with the possibility of manual modification). The calculation then does not include images located near the end of the cycle behind this point, which may be affected by heart rate fluctuations. The result of Fourier analysis at each point of the image are parametric images of the phase and amplitude of cardiac pulsation - Fig.3.1.4.
|Fig.3.1.4. Results of regional Fourier phase-amplitude analysis for a severely pathological case of extensive apical dyskinesia. (Physiological Fourier images are seen in the resulting protocol of a normal patient in Fig. 3.1.9.)|
histogram is constructed from the phase image , where on the
horizontal axis is the phase angle (0 to 360 o
) and on the vertical axis is the number of points (ie the size
of the area) with this phase angle of pulsation. The color
modulation of the phase image is chosen so that the blue color
corresponds roughly to normokinesis (ie phase angles around 60 o
) and the red and yellow colors to asynchrony and dyskinesia with
opposite dynamics (phase angle close to 360°) (phase angle approx. 120° and
higher); the atriums are displayed in yellow to white. The
corresponding verticals on the phase histogram are shown in the
same colors - Fig.3.1.4. The amplitude image has the same color
modulation as the scintigraphic images - well-pulsating areas
with high amplitude are displayed in brighter, darker colors
(blue - black). Dyskinetic (red - yellow - white), hypokinetic
areas are the area in the amplitude image is expressed by an
island (because the surroundings are necessarily akinetic) the
brighter the color, the higher the amplitude of dyskinesia.
Overall, it can be said that the amplitude image is very similar
to the image of heart rate volume, respectively. combined
heartbeat - paradoxical image.
If we want to perform regional quantification phase and amplitude of the cardiac cycle, we will answer the relevant question in the affirmative. Then we gradually mark the respective structures as ROIs on the phase and amplitude images simultaneously (we end each marking with "Mark" and "Continue"). According to the instructions on the display, we first mark the normokinetic region (usually a posterolateral segment), which is then taken as a reference for determining the phase shift and relative amplitude of other regions. After marking each area of interest on the instruction of the program, we will insert its name . For each such marked region, a histogram of the phase distribution in this region is generated and displayed, and the size of the region relative to the whole chamber, the average absolute phase, the relative amplitude, and the phase shift relative to the reference normokinetic region *) are calculated.
*) Only non-zero ones are taken into account in the calculation cells defined by ROI, because zero values ??are created by truncation and have no real meaning. Therefore, when defining the ROI, we do not have to anxiously avoid or. zero notches or islands.
After completing the regional Fourier analysis (answer "no" to the question whether to continue with further quantification), a table of the results of the regional amplitude-phase analysis (Fig. 3.1.4) will be displayed in the lower right part of the display. areas can be printed for documentation (it is especially useful for pathological cases).
Visual evaluation of heart wall motility
The following is a simultaneous display of all significant images (ED, ES, SV, paradox, amplitude and phase images), according to which we can visually assess the regional motility of the heart walls. At the request of the program, we can choose three ways to insert the text of the visual evaluation (Fig. 3.1.5) :
1. Normal finding (standard text)
This method automatically generates a standard formulation of normal evaluation, eg:
"We do not observe a regional ventricular wall motility disorder on phase scintigraphic images of the cardiac cycle. "
In addition, a standard formulation of normal conclusion is automatically generated:
" Conclusion : Visual evaluation of images of individual phases of the cardiac cycle as well as quantitative analysis of the volume curve indicate good global and local contractility of the walls of the left ventricle. ".
2. Pathological finding (semi-standard text)
In this method, the following text is automatically preselected:
" Phase scintigraphic images show:
segment asynchrony: "
In the lines of individual types of disorders, we then enter the names of the segments of the heart wall in which we observe the respective disorder and, if necessary other data (eg about the extent of the fault).
3. Non-standard free text
If none of the previous methods suits the given case, we choose the third method, in which we insert any free text into the free frame using the keyboard.
No normal conclusion is generated in pathological evaluation or non-standard text. All preset texts can be easily edited, supplemented and modified as needed using the mouse and keyboard.
Calculation of absolute ventricular volume
An important parameter in nuclear cardiology is the absolute volume of the heart chamber in milliliters. Absolute volume is important both in itself (it may indicate, for example, dilatation of the heart chamber), and serves as a "conversion factor" between relative and absolute quantities. Knowledge of end-distolic volume allows to create a volume curve of the ventricle from the time course of radioactivity in the chamber, to determine the minute volume of heart and heart rate and residual volume from the value of ejection fraction and heart rate, to determine immediate and maximum ejection and filling rates in milliliters per second.
To calculate the absolute end-diastolic volume of the heart chamber , in principle 4 options can be selected at the request of the program (however, we recommend method 1) :
1. Geometric ratio method
This method calculates the end-diastolic volume of the heart chamber on the basis of geometric analysis of the distribution of radioactivity in the heart chamber image, specifically on the basis of the ratio between the maximum in the ventricular image and the area integral of radioactivity in the whole ROI - Fig.3.1.6. The only external parameter that this method needs - the camera display scale [mm / cell] - is stored in the CAMERA.PAR file. This method was developed at our workplace within the research task of 1985-1990 and tested on a number of phantom measurements and clinical examinations. Based on this experience, we can recommend it to all users as the simplest, most durable and most reproducible. The result of the calculation here practically does not depend on the depth of the ventricular placement and is only slightly dependent on the exact marking of the ROI of the heart chamber.
geometric-analytical method for determining the absolute
volume of the heart chamber.
(was developed in Department of Nuclear Medicine in Ostrava)
To put this method into
practice, we do not need to perform any series of phantom
calibration measurements, just a simple method (two point sources
at a distance of 10 cm) to measure the scale of the camera
display and save it in the CAMERA.PAR file.
Note: With good zoom coding (1, 1.2, 2 or 50%, 75%, 100%), it is sufficient to set the display scale in the full-size field of view (zoom 1 or 100%) and the actual display scale for other zoom values. the program calculates itself.
Geometric ellipsoidal method
This method calculates the end-diastolic volume of the heart chamber based on a geometric analysis of the size of the ROI of the heart chamber. The shape of the chamber is approximated by a rotating ellipsoid, the major axis of which is given by the two farthest points in the ROI and the minor axis being counted as the axis of an ellipse which has a major axis determined as before and whose area is equal to the ROI of the chamber. To put this method into practice, it is first necessary to perform a series of calibration measurements using a phantom (eg a rubber balloon) for different volumes in the range of about 60 - 300 ml. and the coefficients regres e vl thus obtained
to add to the CAMERA.PAR file. This method was developed at our workplace at the same time as the first version of the VENTR program on the CLINCOM device (around 1977) and is still used occasionally. When carefully calibrated and performed, it provides good results, but is very sensitive to the accuracy of the chamber ROI marking. We therefore recommend using a rather proportional geometric method.
|Geometric method for determination of absolute ventricular volume by radionuclide ventriculography|
Simple sample method
The sample method determines the end-diastolic volume of the heart chamber based on the ratio of the integral of the number of pulses in the ROI of the heart chamber and the number of pulses measured in the blood sample taken. We take a blood sample of a defined volume during a radioventriculographic study, then place it in the field of view of the camera and measure the number of pulses for a defined time (or take a static scintigraphic image and determine the integral number of accumulated pulses). When evaluating with the VENTR program, after selecting a simple sample method, we first enter the measured activity of 1 ml. blood sample in pulse count./sec. The following is a question of how to make a correction for the absorption of gamma radiation from the left ventricle. The absorption depth of the chamber can be specified explicitly, or the program will determine it approximately from the height and weight of the patient. The sampling method should theoretically provide more accurate values of ventricular volume, but is more difficult to practice (blood sampling and measurement) and uncertainty in the absorption of radiation from the ventricle may also introduce certain errors.
|Sample method for determination of absolute ventricular volume by radionuclide ventriculography|
4. Sample method combined
with the integral of the first flow
This relatively complicated method is based on the relationship between the applied bolus activity and the integral of the first bolus flow through the heart chamber in bolus angiocardiography, which precedes just before equilibrium ventriculography. Before application, the bolus activity is measured in a suitable arrangement either under the camera (in a suitable absorbing case) or another detector or activity meter (we must have a conversion factor between this measurement and direct measurement on the camera). Then we apply the bolus and store the angiocardiographic study, followed by a radioventriculographic study. When evaluating a first-pass cardiographic study, we determine the integral of the first bolus flow through the left ventricle (using exponential extrapolation). When calculating the EDV method 4 in the VENTR program, we enter the value of the applied bolus activity in imp./sec., integral of the first flow in imp. and heart rate at first transit. This method has the advantage ofthat it does not need to determine the depth of chamber placement, but is generally methodologically very demanding and is applicable only in combined RKG + ventriculographic studies (details are given in the book Ullmann V., Kuba J., Kuchař O., Mrhač L., Dudzik J. : Computer processing of dynamic scintigraphic studies, final report of research task No. 30-02-03 of the Ministry of Health, 1985.
not calculate ED volume
The calculation of end-diastolic volume is optional . If we select the “Do not count” option, the EDV does not count, which is expressed on the display and in the final protocol by the statement " End-diastolic volume not counted ". We choose this option when, for example, due to inappropriate projection, the heart chamber overlaps with other structures or part of the chamber is missing and the EDV value would not be correct.
For each method, the calculated end-diastole value appears on the display. volume with the question whether we agree with the calculation. If we answer in the negative, the table of methods for determining EDV will reappear and we can repeat the calculation with the same or another method (with possibly modified parameters).
Mathematical analysis of the volume curve; ejection fraction
To calculate the quantitative parameters of central hemodynamics, curves of the time course of radioactivity in the marked ROIs (ie the left ventricle and background, or even the right ventricle and its background) are created . The following is a mathematical processing of these curves, in which some corrections of the curve must first be made :
Event correction. distortion (artificial reduction) of the end section. This distortion is caused by fluctuations in the period of the cardiac cycle during the study, which leads to a slightly smaller number of cycles contributing to the last few images than to the other images. The program corrects this distortion by multiplying the respective endpoints of the curve by a coefficient created as the ratio of the number of cycles accumulated in the initial section of the curve and the number of cycles accumulated for the respective endpoint section.
The time course curve of radioactivity in the heart chamber shows statistical fluctuations, which can have an adverse effect at some stages of mathematical processing (especially in derivation). Therefore, it is useful to suppress these interfering statistical fluctuations by appropriate smoothing of the m curve. However, conventional smoothing methods (eg multiple 3-point smoothing), if they are to be sufficiently effective, also distort the dynamics of the curve - it can lead to a reduction in the pulsation amplitude and thus to a reduction in the value of the ejection fraction. In the VENTR program, a special algorithm is used to smooth the curve, which smooths the curve strong enough without causing its distortion - the values of dynamic parameters such as ejection fraction are not affected.
The time course curve of radioactivity in the ROI of the heart chamber captures the time dependence of the instantaneous radioactivity not only in the chamber, but is superimposed with the radioactivity of the tissues above and below the chamber during planar camera projection. In order to obtain a "pure" curve of the course of radioactivity in the heart chamber itself, it is necessary to correct it against the tissue background . The exact correction of this kind is fromproblematic because the tissue background is inhomogeneous and it is not known what part of the background is caused by Compton-scattered radiation from the ventricle, blood supply to the heart wall and blood supply to other tissues - the proportion of constant and variable background components is not known. In the VENTR program, a curve from the above-described "moon-shaped" ROI between the contours of the ventricle in the ED and ES is used for background correction, from which the value at the points corresponding to the end-systole is taken for background subtraction.
After correction for the tissue background, an undistorted curve of
the time dependence of the instantaneous radioactivity
(proportional to the instantaneous amount of blood) in the heart
chamber during the cycle *) is formed, from which we can
objectively calculate dynamic parameters. To calculate the
quantitative parameters, the points of end-diastole ED,
end-systole ES, beginning and end of ejection and filling are
automatically defined on the curve (with the possibility of
*) In general, the dynamics of the curve could be distorted by two other factors - dead time and self-absorption of gamma radiation in a pulsating chamber. Fortunately, none of these adverse factors apply to equilibrium ventriculography for the following reasons.
The loss of pulses through the dead time is determined by the total frequency of pulses in the entire field of view of the camera. In ventriculography, both the ventricles and the atria, which pulse in the opposite direction, are usually in the visual field - in systole, the decrease in pulse frequency from the ventricle is roughly compensated by the increase in atrial radioactivity, and in diastole the growth of ventricular activity is compensated by the pulse rate. Total radioactivity and therefore the pulse frequency in the whole visual field j e are roughly constant, so is the constant or. percentage of loss of impulses due to dead time - therefore it will have no effect on the quantification of dynamics.
As for self-absorption, if the heart chamber pulsed under the camera in free spacewithout the surrounding environment, then when the chamber is filled, the self-absorption of gamma radiation in the blood volume of the chamber itself would be somewhat greater than when the chamber is emptied. In reality, however, the heart chamber pulsates in an environment with an absorption coefficient approximately the same as that of the blood in the chamber, which changes the situation. The relevant calculation and phantom measurements (both were performed as part of our research task ..........) show that if a chamber of approximately spherical or elliptical shape is isotropically pulsating in an environment with the same absorption coefficient, not only is there no increase in loss by absorbing gamma radiation in the filled chamber, but on the contrary, there is a slightly lower total absorption in the filled chamber than in the empty chamber. In practice, there is no appreciable effect on the pulsation dynamics by the absorption of gamma radiation, so that the corresponding curve V (t) can be considered as the actual volume curve of the ventricle.
The EDV value, determined above, makes it possible to create a volumetric curve V (t) from the normal curve A (t) of the time course of radioactivity in the heart chamber , each point of which indicates the instantaneous volume V of the heart chamber at the respective time t of the heart cycle. Important parameters of central hemodynamics are calculated from this curve (Fig. 3.1.7) :
|Fig.3.1.7. Important parameters of central hemodynamics calculated by volume curve analysis.|
Some time intervals can also be calculated from the volume scream, but a more accurate determination of time intervals is performed on a derived (velocity) curve - see below. The calculated volume parameters of the left ventricle are displayed together with the volume curve (time is marked on the horizontal axis, volume in [ ml. ] Is calibrated on the vertical axis ) and we can print them out for documentation - Fig. 3.1.7. If the ROI of the right ventricle has also been marked, this quantification will also be performed for the right ventricle.
Quantification of speed parameters
The time derivative of the volume curve V (t) gives rise to the velocity curve R (t) - Fig.3.1.8
R (t) = d V(t) / dt
which at each of its points indicates the instantaneous rate of ejection or ventricular filling during the cardiac cycle. The smoothing of the velocity curve so that it does not affect the dynamics is performed analogously to the volume curve. The points of the maximum ejection and filling speed, the beginning and end of the ejection, the beginning and the end of the fast filling phase are defined by the program on the speed curve. The relevant speed parameters are calculated :
Further, from the velocity curve, a number of time intervals characterizing the time schedule of significant phases of the heart revolution are determined :
|Fig.3.1.8. Velocity and time parameters of ejection and filling calculated by velocity curve analysis|
The displayed velocity curve (time is on the horizontal axis, ejection and filling speed in [ ml./sec. ] Is calibrated on the vertical axis ) together with a number of speed and time parameters can be printed out again for documentation (Fig.3.1.8). If the ROI of the right ventricle has also been marked, the described calculations will also be performed for the right ventricle.
The resulting protocol
The following is a summary of the most important evaluation results: images of end-diastole and end-systole, contours of the heart wall, paradoxical and pulse image, Fourier images of phase and amplitude including histogram of phase distribution, volume and velocity curve, below them a clear table of the most important calculated quantitative parameters left and right ventricle. At the bottom of the screen, a verbal assessment is offered for editing. These verbal evaluation texts (including the conclusion) can be freely modified or supplemented as required. Among other things, we can reconcile verbal evaluation with the results of quantitative parameters. After the final value, I will appreciate the "Signature:" section, where we will insert the name of the evaluating doctor.
Nuclear Medicine, University Hospital Ostrava
Name of patient: ....................... . Birth certificate number: .........................
|Mathematical analysis and complex evaluation of radionuclide ventriculography|
We do not observe regional disorders of heart wall motility on phase scintigraphic images of the cardiac cycle, nor on Fourier images of phase and amplitude.
|Fig.3.1.9. The resulting protocol of complex evaluation of radionuclide ventriculography - an example of a normal finding.|
The comprehensive evaluation of ventriculography ends with the printing of a clear report containing administrative data (name of workplace, name and birth number of the patient, name of examination, date, etc.), prominent images, curves, calculated quantitative parameters, verbal assessment of heart wall contractility and final evaluation of the whole examination with by the doctor's signature - fig.3.1.9 (normal) and fig.3.1.10 (markedly pathological case ).
Nuclear Medicine, University Hospital Ostrava Date:
Name of patient: ....................... . Birth certificate number: .........................
|Mathematical analysis and complex evaluation of radionuclide ventriculography|
The following regional disorders of left ventricular wall motility are observed in phase scintigraphic images of the cardiac cycle and in Fourier images of phase and amplitude:
segment hypokinesia: Virtually all except posterolat.
|Fig.3.1.10. The resulting protocol for
a comprehensive evaluation of radionuclide
- an example of an extremely pathological finding.
Separate Fourier analysis
Fourier phase analysis can be performed not only as part of a comprehensive evaluation within the VENTR program, but also separately. This separate design is advantageous, for example, in ventriculography in LL projection, where the quantification of ejection fraction and other dynamic parameters would not be correct due to the mutual overlap of cardiac structures, but we are interested in the local contractility of the respective heart wall segments. The FOURI program, which start,is used for this purposewe take from the menu ClinProg. The only difference from phase analysis in the VENTR program is that the FOURI program first generates a time course curve of radioactivity in the entire field of view in order to determine the endpoint of the Fourier analysis. Images of phase and amplitude and histograms of phase distribution together with a table of quantitative data of regional amplitude-phase analysis of evaluated areas can be printed on a printer. Fourier phase analysis program Four projections at j different s than LAO recommended to perform before a comprehensive evaluation program LAO projection ventry to any knowledge of motility disturbances respective segments of the heart wall (invisible in LAO projection) may include in the final word evaluation program VENTR.
The VENTR program consists of the following parts (capable of independent function):
VENTR1 - precise determination of end-diastole
and end-systole phases, summation of their images, construction
of paradoxical image, heart rate image and combined
paradoxical-heart rate image
VENTR2 - automatic delimitation of heart chamber and background
ROI VENTR3 - photography of ED, ES, paradoxical and heart rate images, wall contours in ED and ES, Fourier analysis
VENTR4 - verbal evaluation of heart wall contractility, creation of curves
VENTR5 - mathematical processing of curves and calculation of quantitative parameters of central hemodynamics, editing and printing of the final protocol
At the same time, this structure shows how to proceed when the program is interrupted or restarted in order to repeat some part of the calculation. If we want to repeat the mathematical processing of curves or modify the wording of the word evaluation and print a new protocol, just run the last part of the program - VENTR5. If we want to perform Fourier phase analysis (whether to repeat it or we have not performed it before), we run VENTR3, or we will use a separate FOURI program (as mentioned above).
Cast of SAVE AREA after the end of the
SA 3 - heart rate image
SA 4 - paradoxical image
SA 5 - end-diastole image including ROI
SA 6 - end-systole image including ROI
SA 7 - curves from ventricular and background areas
SA 8 - combined paradoxical +
heart rate image SA 9 - heart wall contours in ED and ES
SA10 - Fourier image of amplitude
SA11 - Fourier image of phase
|Nuclear physics and physics of ionizing radiation | OSTNUCLINE|
|Nuclear and radiation physics||Radiation detection and spectrometry||Radiation applications|
|With cintigraphy||Computer evaluation of scintigraphy||Radiation protection|
|Gravity, black holes and spacetime physics ;Anthropic principle or cosmic God|
|AstroNuclPhysics ® Nuclear Physics - Astrophysics - Cosmology - Philosophy|