**3.11b.
Dynamic scintigraphy of pulmonary ventilation**

Dynamic scintigraphy of pulmonary ventilation
is a comprehensive examination that allows detailed and regional
quantification of a number of parameters of **lung
respiratory function** - total lung capacity, residual
volume, **exchange fraction of air** in the alveoli
(per unit lung volume) and exchange volume of air.

**Study storage
**Dynamic
scintigraphic examination of

in the evaluation . Then the appropriate valve is opened and the patient breathes normal air without radioxenone, thereby radioactive

**Study evaluation**

**Determination of
significant phases of ventilation**

In the computer evaluation of the dynamic study thus obtained,
the **areas of interest** (ROI) of the left lung, right
lung and tissue background are first marked on the summation
image of the equilibrium (Fig ... a). From these areas, **curves of the** time course of radioactivity ^{133} Xe during the examination are formed .
The curve from the lungs has a typical shape (Fig.3.11b.1 top
left): at the beginning of the **equilibrium** , where the elevated points
corresponding to the maximum inspiration and the decreased points
corresponding to the maximum expiration are visible; followed by
a phase of **exhalation **^{133} Xe from the lungs (wash-out) in which the
activity of the lungs decreases gradually to the level of body
background.

Fig.3.11b.1. Principle of absolute
dynamic scintigraphy of the lungs by breathing ^{133} Xe in a closed circuit
(max. Inspiration and expiration, equilibrium) and
subsequently in an open circuit (wash-out). |

The points and sections corresponding to the maximum inhale and exhale, equilibrium and the wash-out section are then defined on this curve (automatically with the possibility of manual intervention). By summing the images corresponding to these dynamically significant points and sections, the resulting scintigraphic images of the characteristic stages of the examination are created, and further analysis is used to construct parametric images and calculate the values ??of quantitative parameters.

**Parametric images of
the regional distribution of spirometric parameters**

Images corresponding to significant points and sections defined
on the time course curve of radioactivity ^{133} Xe in the lungs are **summed** , thus creating images of the lungs in
the phase of max. Inspiration, max. 2 c, d, e).

Fig.3.11b.2. Mathematical analysis of
dynamic scintigraphy of pulmonary ventilation. a) Areas of interest of the left and right lungs and background. b) Time course curves of radioactivity ^{133} Xe in the lungs and
background. c) Equilibrium image. d) Image of lungs in
max. breath (TLC distribution). e) Image of max.
exhalation (residue distribution). f) Parametric picture
of vital capacity. g) Parametric picture of the
distribution of effective ventilation (exchange volume).
h) Parametric picture of the regional distribution of the
exchangeable air fraction. |

Next, we enter the
measured value of **the volume
difference**
between the maximum inhale and exhalation (in milliliters). Based
on this value and the difference between the charged number of
pulses in the respective images of the lung max. Inpiriu and
expirium calculated **calibration
factor **__F__ between nastřádanám number of pulses
and the volume of air (the "tagged" ^{133} Xe) in milliliters - scintigraphic
studies thus becomes **quantitative** and what the **absolute volumes** - each impulse in each element of the
image is expressed in **milliliters
of air** at a
given location of the lungs.

The program then creates images of the
distribution of pulmonary volume in equilibrium, the distribution
of vital capacity of the lungs at maximum inspiration, the
distribution of residual volume at maximum expiration and the
distribution of vital capacity of the lungs - Fig.3.11b.2 c, d,
e, f. These images are quantified - the contents of individual
cells directly indicate the number of milliliters of air at a
given site of the lung - they are locally parametric images.

Then follows the construction of locally **parametric
images of the regional distribution of pulmonary ventilation**
. A time course curve of radioactivity ^{133} is generated for each point in the image matrixXe at
this point and from it the relevant ventilation quantity is
calculated according to the formulas in the lower part of
Fig.4.11b.1 - exchangeable fraction EF [% / s] and exchangeable
volume EV [ml./s], ie the amount of air that is in replace at the
appropriate location in 1 second. The parameter calculated in
this way is then stored at the point in the image from which the
analyzed curve originated. This is done for all points of the
image matrix, which gives **parametric** or **functional
images** , which is a kind of clear "map" of the
regional distribution of the dynamics of the studied process -
pulmonary ventilation (Fig.3.11b.2 g, h):

- Image of the distribution of the
**exchange fraction**VF (x, y) showing what part of the air volume in% is exchanged in individual places (x, y) of the lungs in 1 second. - An image of the distribution of
**effective lung ventilation**showing at each location (x, y) the amount of air V (x, y) in milliliters that is exchanged here in 1 second.

From these parametric images it is clear which
parts of the lungs have better or worse functional (respiratory)
ability and it is also possible to immediately determine the **local
values ??of the** relevant quantitative ventilation
parameters at each location - exchange air fraction in percent
and exchange volume in milliliters per second .

Fig.3.11b.3. Regional distribution of exchange fraction in individual lung fields. |

The regional
distribution of lung ventilation parameters is sometimes
evaluated for individual **lung
segments** .
The areas of interest of the left and right lungs are usually
divided vertically into three equally large parts, in which the
average or summary values ??of the required ventilation
parameters are calculated from parametric images and also
expressed as a percentage of the total global value - an example
is shown in Fig.3.11b .3.