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Angiocardioscintigrafia equilibrium - Thin Layer Chromatographic Techniques ACS

The Angiocardioscintigrafia is a technique that studies the cardiovascular system after a radiocompound introduced in the circulation is evenly distributed throughout the vascular space, representing images simultaneously in all chambers of the heart and great vessels. It is based on the use of radiolabelled that persist in circulation for a long time such as albumin or red cells labeled with 99mTc. It rpeferisce mark iin vivo erythrocytes according to the procedure Pavel (1977), iv injection of tin salts (agent stannous Sn-DTPA), in doses of 35.7 micrograms / kg and 20-30 minutes after a dose of 99mTc pertechnetate mCi 25 (925MBq). At about 5 min from the injection of 99mTc pertechnetate obtained Marking the Dek 96% approx. goobuli of circulating red, marcarura that remains stable for about 3 hours. A votla achieved a balanced distribution of the intravascular tracer, provides information on the cyclic changes of intracardiac blood volume for filling (diastole) and emptying (systole) ventricle.

uan In order to obtain suitable counting statistics, plus the counts of many cycles synchronized with each other resulting in the so-called representative cardiac cycle. Still then the computer system of the gamma camera to a physiological signal (ECG R-wave), there is the activity of the heart only in times of the cycle corresponding to the R-phase (early diastole).

synchronization (gating) of all phases du diastolic many cardiac cycles allows you to obtain scintigraphic image, whose resolution depends on the dose administered and the radiocompound the number of cycles added up, ultimately that is the acquisition time data.

MUGA

Using a high-speed image processor, you can capture a large number of images per cycle. In this way a multi-gated (MUGA - multiple gate) you can get the images not only in systole and diastole, but in all phases of the cardiac cycle. With the MUGA technique is the physiological trigger of the ECG R wave, which marks the beginning of each cycle cmpreso between 2-R later. The computer divided each cycle in 20-30 microintervals of 30 -50 ms to a sum and a large number of images recorded by similar micro intervals of several cardiac cycles.

ACS synchronized equilibrium, based sulal difference in radioactivity between systole and diastole, as an expression of the development of ventricular volume during the cardiac cycle, through the reconstruction of time-activity curves, gives precise indication of overall functionality.

With the same method is also possible to obtain an evaluation visual chambers of the heart, great vessels and their Chinese and global zonal.

With the ACS, and can also be measured accurately and reliably, a parameter delal ventricular function such as ejection fraction FE.

Technical

are administered ev mCi (925 MBq) of 99m 30 'after insroduzione in the vein of salts of tin (stannous agent). the investigation is being conducted with computerized gamma camera with a trigger connected to a physiological signal (usually the R wave of ECG). The projection is commonly used the OAS to 45 °. However, it should pay particular attention alal separation of right from the left side of the heart and the separation of the heart from the surrounding organs. You can use a high-resolution collimator. The projection is more informative than the OAS with the head angle of 35-45 degrees, so that the left and right ventricles are completely separated. The collimator during the examination must be kept attached to the chest. The examination requires that each survey acquisition synchronized (gated) with the ECG for several minutes. The acquisition allows you to add a wild series of short intervals of the dynamic phase of contraction. To have intervals (frames) of the RR cycle with a count of adequate Doppler processing must be sufficiently The higher the number of heartbeats acquired.

The number of cycles required varies depending on the FC and the number of frames which divides lìintervallo RR. Uan for certain reliability you need at least 24-32 samples per beat. The aim of all the acquisition technique is to add the cycles of the same duration and therefore are discarded premature beats and no abnormal cycle times compared to an average value of the RR interval.

Data Processing

Data processing sequence provides an overview of moving images represented on the screen in a continuous loop, where you can evidenzialre changes in cardiac chambers, ventricular wall motion, size and pulsatility of the limbs and large vessels. Then proceed to the construction of curve activity / time, obtained from atrial and ventricular ROI, after subtracting the background radioactivity of circulating surrounding structures, which express the development of ventricular volumes throughout the cardiac cycle. From these curves are obtained uan series of quantitative data and build functional images (parametric).

reliable quantitative data are

1. ejection fraction (EF), left and right ventricular;
2. top speed of emptying (peak emptying rate - PER);
3. the speed of filling (peak filling rate - PFR);
4. the time between the PFR and diastole (time of peak filling rate - TPRF)
5. the sininstro diastolic ventricular volumes (end diastolic volume - EDV), and remote systolic left (end sistolic volume-EDV);
6. stroke volume (stroke volume - SV).

quantitative parameters

Table I.

• ejection fraction (EF) right ventricular. 62% ds. 52%
• Maximum discharge (FOR)> 4 vol / diastolic / sec
• speed filling (PFR)> 2.5 vol / diastolic / sec
• time between telesistolee PFR (TPFR ) <>
• since end-diastolic volume (EDV)
• since end-systolic volume (ESV)
• stroke volume (SV)
• ventricular stroke volume ratio ds / sn: 1
• fraction regurgitation: 1 to 1.3

Ejection fraction (EF)

The most important is the FE obtainable by ACS. It is calculated using the formula: diastolic

counting - counting systolic / diastolic count

correct for background subtraction.

The most reliable method uses a semi-automatic operator-assisted, which identifies the edge of the left ventricle throughout the cardiac cycle in projection OAS (Oblliqua front left).

speed evacuation and riempiment0 (PER-PFR)

The speed of emptying and filling expresses changes in ventricular volume over time. The values \u200b\u200bobtained are expressed in diastolic volume per second (EDV / sec). For the speed of emptying (PER). Normal values \u200b\u200bare greater than 3 EDV / sec, the speed of filling (PFR) is greater than 2.5 EDV / sec. They reflect the capacity of ventricular relaxation, are particularly affected by the frequency and measure the diastolic function (Table I). To obtain more accurate oparametri using the ratio PER / PFR.

ventricular volumes and stroke volume

Hypocrite in a 'balance-way ACS is proportionality between the counts measured in the cardiac chambers and volumes. In fact it leads to a reduction self-absorption of radiation emitted by tissue together with an increase of diffuse radiation in the surrounding tissues. This variability should be taken into account. The method currently used for the measurement of left ventricular volumes is based on the counting of strokes, regardless of any consideration and geometric analysis:

Activities Ventricular Volume = sin / No cardiac cycles * (time / frame) * activities

blood counts obtained by measuring the volume of a given frame, usually the left end-diastolic (EDV) is correct for the time of acquisition of that frame and the activity of a blood sample of known volume.

Constant (K) is obtained an average factor of attenuation correction and a correction introduced obtain average attenuation, although sometimes, with the variation of body morphology as with subjects very fat or very thin or in case of ventricular size significantly increased the possibility of error rises . The left end-diastolic volume (EDV) measured this way correlates well with that calculated by ventriculography. From

diastolic volume and the FE you get the end-systolic volume (end sistolic volume - ESV) and stroke volume (stroke volume - SV).

regurgitant fraction

The relationship between the counts left ventricle / right ventricle or difference between the count range of left and right ventricular counts as a percentage of the left ventricle can be used for calculating the amount of regurgitation. This number is close to 1 in the absence of irigurgiti left but can arrivarea to 5 in case of aortic or mitral regurgitation. The data provided with this metodicasi correlate quite well with those obtained from a wild and qualitative evaluation of ventriculography with those calculated quantitatively by the method of Fick. The limit of this method lies in the frequent overlap of the atrium and right ventricle that can lead to errors of evaluation such as an overestimation of the regurgitant fraction.

flow ventricular left

is determined by multiplying the FE with CF and end-diastolic volume. The relationship between stroke volume of the two ventricles (stroke count ratio) is obtained by comparing the stroke volume of left and right ventricle, which under normal conditions is equal to 1.

Motility regional

Summing up the computer with the individual images from different cardiac cycles, you get a wild sharp image, the total of any phase of the cycle and you can see the changes to quality of the heart chambers. For a more accurate assessment of various quantitative methods have been proposed, in which the end-diastolic frame ventricle was divided into anterior oblique projection in different regions. The criterion is more valid than the radial regions. Identified a ventricular heart, usually center of gravity, are plotted areas of interest (ROI) using the edges in the shape of circular sectors. You typically use 4-5 sectors. Changes in the count during the cardiac cycle, for volume changes within each region are used to calculate the FE region. It 'still relevant simple assessment of visual images on display.

Images parametric

angioscintigrafica The computer divides the image into small squares (pixels) and assess the progress of the counts in the series of images characteristic curves with the development of cardiac structures examined. nellanalisi curves flat bottom, curved sinusoidal areas with ventricolaricurve opposite trend to that atrial and ventricular areas in the aortic-pulmonary.

For each computer calculates dopoaver performed the fitting of the same, the phase angle and the amplitude of variation these two parameters and builds functional images. Pixels with the same parameters are the same color, changes in parameters are expressed with different colors. Higher values \u200b\u200bare represented by red and then with the yellow, green, blue values \u200b\u200bprogressivamentepiù low.

The amplitude of the curve of ventricular volumes - parametric image amppiezza - provides information on the synergy of contraction, and hypokinetic areas have a cooler color, green or blue, or red expressing Valloria max amplitude. Curves with the same trend of the phase synchronism of contraction and expressed with the same color, while alterations of segmental timing appear as areas of different color.

The computer can also express the image phase parameters, as well as with different colors, including a diagram of the distribution phase in siongoli pixels. The diagram consists of specified peak in the number of pixels and the abscissa the degree of phase. normally the highest peak corresponds to the symmetrical and the ventricles, the lower courts to separate from the first.

the ordinary

The picture shows the normal ventricular cavity as areas of radioactivity with a well-defined contours, a clear separation from the septum and normal Chinese and uniform in color parametric images of amplitude and phase. At rest, the FE of the left ventricle is usually considered around 62%. The left ventricular EF contituisce parameter ventricular function more reliable and reproducible methodological variations contained within acceptable margins of error.