Method and device for processing at least one image of a given part of at least one lung of a patient
A method for automatically processing at least one image slice of a given part of at least one lung of a patient suffering from a pathology that causes a bronchial infection by diffuse dilatation of the bronchial tubes of the lungs. The method includes segmenting the at least one image slice of the given part of the lung, in order to produce a histogram characterizing the pulmonary density of the given part of the lunch, by means of the voxels of the at least one image slice, each voxel associated with a given pulmonary density; calculating a threshold, from the histogram, corresponding to a threshold pulmonary density, based on at least one characteristic of the histogram, a first characteristic being the mode of the histogram; determining from the at least one image slice of the given part of the lung, a pulmonary volume having a pulmonary density higher or lower than the calculated threshold, corresponding to the sum of the voxels having a pulmonary density higher or lower than the calculated threshold; and calculating an automatic score on the basis of the determined pulmonary volume.
1. Method for automatically processing at least one image slice of a given part of at least one lung of a patient with a pathology that induces bronchial damage by diffuse dilatation of the bronchi of the lungs, the method comprising steps of:
acquiring at least one image slice by CT scan,
segmenting the image slice(s) of the given part of the lung, in order to produce a histogram characterizing the lung density of the given part of the lung, using the voxels of the image slice(s), each voxel being associated with a given lung density,
calculating from the histogram a threshold corresponding to a threshold lung density, based on one or more characteristics of the histogram, a first characteristic being the mode of the histogram, the mode corresponding to the lung density most represented in the histogram of the image(s) of the given part of the lung,
determining, from the image slice(s) of the given part of the lung, a lung volume having a lung density above or below the calculated threshold, corresponding to the sum of the voxels having a lung density above or below the calculated threshold,
calculating, from the determined lung volume, an automatic score to monitor changes in the patient's bronchial involvement,
wherein the threshold is based on at least two characteristics, and the second characteristic is a standard deviation of density values of the histogram.
2. Method according to claim 1 , wherein the threshold is calculated using the following formula:
threshold=mode+ N ·(standard deviation)
where N is a predetermined value comprised in an interval ranging from 0 to 4.
3. Method according to claim 2 , wherein N is a predetermined value comprised in an interval ranging from 1 to 2.
4. Method according to claim 1 , in which the automatic score is a ratio between:
the lung volume having a lung density above or below the calculated threshold, and corresponding to the sum of the voxels having a lung density above or below the calculated threshold; on
a total volume of the lung shown by the image(s), corresponding to the sum of all voxels in the image slice(s).
5. Method according to claim 1 , wherein:
the lung volume with a lung density above the calculated threshold is determined ( 106 ) from the image(s) of the given part of the lung,
the automatic score is the ratio between:
the lung volume having a lung density greater than the calculated threshold corresponding to the sum of the voxels having a lung density greater than the calculated threshold; on
a total volume of the lung shown by the image(s), corresponding to the sum of all voxels in the image slice(s).
6. Method according to claim 1 , wherein the images are taken over both lungs, or over one or more lobes of the lungs.
7. Method according to claim 1 , wherein the images are acquired when the patient inspires.
8. Method according to claim 1 , wherein the automatic score is also a function of a third characteristic, which is the skewness coefficient of the histogram, and a fourth characteristic, which is the kurtosis coefficient, and is calculated using the following formula
score
=
a
*
(
standard
deviation
)
+
b
*
(
mode
)
+
c
*
(
skewness
coefficient
)
+
d
*
(
kurtosis
coefficient
)
+
e
*
(
lung
volume
with
a
lung
density
above
the
calculated
threshold
total
lung
volume
of
the
lung
shown
by
the
image
)
where a, b, c, d and e are predetermined coefficients, at least one of the coefficients a, b, c, d and e depending on an image segmentation algorithm used to implement the segmentation step and where the skewness coefficient and the kurtosis coefficient refer to the histogram.
9. Method for measuring, in a patient, the extent of a pathology that induces bronchial damage by diffuse dilatation of the bronchi of the lungs, the measurement method comprising the processing method according to claim 1 .
10. Device for automatically processing at least one image slice of a given part of at least one lung of a patient with a pathology that induces bronchial damage by diffuse dilatation of the bronchi of the lungs, the device comprising:
a module for acquisition of at least one CT image slice and for segmentation, configured to segment the image(s) of the given part of the lung, in order to produce a histogram characterizing the lung density of the given part of the lung, using the voxels of the image slice(s), each voxel being associated with a given lung density,
at least one processor configured to:
calculate a threshold based on one or more characteristics of the histogram, a first characteristic being the mode of the histogram, the mode corresponding to the lung density most represented in the histogram of the image(s) of the given part of the lung,
determine, from the image slice(s) of the given part of the lung, a lung volume with a lung density above or below the calculated threshold, corresponding to the sum of the voxels with a lung density above or below the calculated threshold,
calculate, from the determined lung volume, an automatic score to monitor changes in the patient's bronchial involvement,
the threshold being based on at least two characteristics, and the second characteristic is a standard deviation of density values of the histogram.
11. Method according to claim 9 , wherein the pathology that induces bronchial damage by diffuse dilatation of the bronchi of the lungs is selected from the group consisting of cystic fibrosis, primary ciliary dyskinesia, post-infectious bronchial dilatation and idiopathic diffuse bronchial dilatation.