Application of threshold detectors for increasing of the contrast in X-ray images
Efficiency in the use of detectors with threshold energy discrimination of radiation (“threshold detectors”) for improvement of contrast in X-ray images in quasimonochromatic X-rays is considered. The threshold detectors would allow to eliminate registration of X-rays with energy below of the energy...
Збережено в:
| Опубліковано в: : | Вопросы атомной науки и техники |
|---|---|
| Дата: | 2005 |
| Автори: | , , , |
| Формат: | Стаття |
| Мова: | Англійська |
| Опубліковано: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2005
|
| Теми: | |
| Онлайн доступ: | https://nasplib.isofts.kiev.ua/handle/123456789/79817 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Application of threshold detectors for increasing of the contrast in X-ray images / V.V. Sotnikov, V.A. Voronko, A.V. Shchagin, V.M. Sanin // Вопросы атомной науки и техники. — 2005. — № 2. — С. 226-228. — Бібліогр.: 5 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860084260892835840 |
|---|---|
| author | Sotnikov, V.V. Voronko, V.A. Shchagin, A.V. Sanin, V.M. |
| author_facet | Sotnikov, V.V. Voronko, V.A. Shchagin, A.V. Sanin, V.M. |
| citation_txt | Application of threshold detectors for increasing of the contrast in X-ray images / V.V. Sotnikov, V.A. Voronko, A.V. Shchagin, V.M. Sanin // Вопросы атомной науки и техники. — 2005. — № 2. — С. 226-228. — Бібліогр.: 5 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | Efficiency in the use of detectors with threshold energy discrimination of radiation (“threshold detectors”) for improvement of contrast in X-ray images in quasimonochromatic X-rays is considered. The threshold detectors would allow to eliminate registration of X-rays with energy below of the energy of incident monochromatic X-ray beam. Therefore, incoherent scattered photons will not be registered and contrast will be increased and/or total dose may be reduced.
Розглядається ефективність застосування детекторів із граничною дискримінацією випромінювань (“граничних детекторів”) для збільшення контрастності рентгенівських зображень, одержуваних за допомогою квазимонохроматичних рентгенівських пучків. Граничні детектори дозволяють відітнути з формованого рентгенівського зображення некогерентно розсіяні фотони, і тим самим збільшити контрастність зображення і/або зменшити дозу опромінення.
Рассматривается эффективность применения детекторов с пороговой дискриминацией регистрируемых излучений (“пороговых детекторов”) для увеличения контрастности рентгеновских изображений, получаемых с помощью квазимонохроматических рентгеновских пучков. Пороговые детекторы позволяют отсечь из формируемого рентгеновского изображения некогерентно рассеянные фотоны, и тем самым увеличить контрастность изображения и/или уменьшить дозу облучения.
|
| first_indexed | 2025-12-07T17:18:55Z |
| format | Article |
| fulltext |
APPLICATION OF THRESHOLD DETECTORS FOR INCREASING OF
THE CONTRAST IN X-RAY IMAGES
V.V. Sotnikov, V.A. Voronko, A.V. Shchagin, V.M. Sanin
NSC Kharkov Institute of Physics and Technology, Kharkov, Ukraine,
e-mail: sotnik@kipt.kharkov.ua
Efficiency in the use of detectors with threshold energy discrimination of radiation (“threshold detectors”) for
improvement of contrast in X-ray images in quasimonochromatic X-rays is considered. The threshold detectors would
allow to eliminate registration of X-rays with energy below of the energy of incident monochromatic X-ray beam.
Therefore, incoherent scattered photons will not be registered and contrast will be increased and/or total dose may be
reduced.
PACS: 95.55.Ka; 41.50+h; 41.60-m
1. INTRODUCTION
In X-ray imaging, one of the topical problems is the
improvement of image contrast. A high-contrast X-ray
image can be obtained by excluding from the image a part
of photons scattered by the irradiated object, which
represent an interfering background in the formation of
the image and necessitate an increase in the radiation
dose.
One of the possible ways of decreasing the portion of
scattered photons in X-ray imaging lies in the use of
detectors with threshold energy discrimination of
radiation (“threshold detectors”). This possibility stems
from the fact that the photon incoherently scattered by
free electrons gives a part of its energy to the electron.
Therefore, if the initial quantum beam is monochromatic,
then the incoherently scattered photons arriving at the
detector will have the energy lower than the energy of
ballistic (unscattered) photons, and the part of these
scattered photons will be cut off by the threshold detector.
A certain part of incoherently scattered photons will also
be cut off through energy discrimination in the case,
where the primary X-ray beam is quasimonochromatic.
These quasimonochromatic X-ray beams may be
produced, for example, by using the parametric X-ray
radiation (PXR) or the coherent bremsstrahlung (CB).
Below we give the estimated percentage of X-ray
quanta scattered in the irradiated sample that may be
eliminated from the X-ray image owing to their energy
discrimination. Numerical calculations were performed
for different initial X-ray beam energies as functions of
quantum energy spread in the initial beam, and also, of
the accuracy of energy discrimination (energy resolution
of the detector).
2. ESTIMATION OF THE NUMBER OF
INCOHERENTLY SCATTERED PHOTONS
ELIMINATED FROM THE X-RAY IMAGE
The cross section for incoherent scattering of
photons by atomic electrons is generally presented as a
product of two multipliers [1]. As a first multiplier, we
use the Klein-Nishina cross section. The second
multiplier is called the incoherent scattering function
( )1 exp 5S v≈ − − [1, 2]. Take into account value of ν [1],
the differential cross section of incoherent scattering by
the atomic electron can be approximately estimated by the
formula:
( )2 / 3
1 exp 456 sin
2
KN
S Sd d
d d Z
σ σ α θ
≈ − − Ч Ч
Ω Ω
й щ
к ъл ы
. (1)
If the photon is scattered through the angle θ from the
initial direction, then its energy varies by the following
value:
( )[ ]1 1 /[1 1 cos ]E Eγ γ α θ∆ = − + − . (2)
The ratio of the number of primary photons scattered
through the range of angles θS < θ < 90˚ to the total
number of photons incoherently scattered to the forward
semisphere will equal the ratio of the corresponding
integral cross sections:
/ 2
/ 2
0
2 sin
( / 2)
(0 / 2)
2 sin
S
s
s
s
d
d
d
d
d
d
π
π
θ
σ
π θ θ
θ θ π
σθ π
π θ θ
ΩΣ Ј Ј
= =В
Σ Ј Ј
Ω
т
т
. (3)
If the energy resolution of the threshold detector
(accuracy of energy discrimination) permits the separation
between photons of energy Eγ and photons of energy E
γ - ∆E , then formula (3) with the lower limit of
integration θS equal to
( )[ ]2arccos 1 /[ ]
S eE m c E E Eγ γθ = − ∆ − ∆Ч Ч , (4)
will determine the percentage of incoherently scattered
photons having the initial (monochromatic) energy Eγ ,
which will be cut off from the X-ray image by the
threshold detector having the energy resolution ΔE.
We now consider how the energy spread in the X-ray
beam influences the scattered-photon cutoff efficiency by
the threshold detector. Let the X-ray beam not be
monochromatic, while the quantum energy distribution in
the beam is uniform from the minimum energy minEγ to
the maximum energy max minE E Eγ γ γ= + ∆ . The energy
threshold of the X-ray detector is tuned to the energy
minsdE E Eγ= − ∆ , where ΔE is the energy resolution of
the detector.
Let us denote the number of quanta incoherently
scattered to the forward semisphere and having the energy
sc
sdE Eγ < by ( )sc sc
sdN E Eγ γ < and the total number of
photons incoherently scattered to the forward semisphere
by 0( 90 )sc
totalNγ θ < . The ratio of these values
226 Problems of Atomic Science and Technology. Series: Plasma Physics (11). 2005. № 2. P. 226-228
0
( ) ( 90 )
sc sc sc
s sd totalN E E Nγ γ γ θ= < <В (5)
determines the percentage of incoherently scattered
photons excluded from X-ray imaging by the threshold
detector having the energy resolution ΔE, when the
primary X-ray beam has the energy spread from minEγ to
minE Eγ γ+ ∆ . The sВ values can be calculated by
integrating the numerator and the denominator in formula
(3) over Eγ with a variable limit of integration θS (4).
The results of numerical calculations of
( )min, ,s E E Eγ γ∆ ∆В for three values of the initial X-ray
beam quantum energy (25.5, 50 and 120 keV) and for
different beam energy widths Eγ∆ are shown in Fig. 1. In
our calculations we have used Z=8 in formula (4), this
corresponding to the basic weighting factor in different
tissues, blood and cerebrum of man [3].
0 0.2 0.4 0.6 0.8 1
0.2
0.4
0.6
0.8
1
ℜ
t( ∆
E
, ∆
E
γ, E
γm
in
)
∆E, keV
0 0.5 1 1.5 2 2.5 3 3.5 4
0.2
0.4
0.6
0.8
1
ℜ
t( ∆
E
, ∆
E
γ, E
γm
in
)
∆E, keV
0 2 4 6 8 10 12 14 16
0.2
0.4
0.6
0.8
1
ℜ
t( ∆
E
, ∆
E
γ, E
γm
in
)
∆E, keV
7
6
5
4 3
1
2
1 - 1.75 keV
2 - 1.50 keV
3 - 1.25 keV
4 - 1.0 keV
5 - 0.75 keV
6 - 0.50 keV
7 - 0.30 keV
8 - 0.15 keV
9 - 0 keV
8 9
9
8
7
6
5
4
3
2
1
1 - 35 keV
2 - 30 keV
3 - 25 keV
4 - 20 keV
5 - 15 keV
6 - 10 keV
7 - 5 keV
8 - 2 keV
9 - 0 keV
a)
b)
c )
1
2
3
5
4
6
7
8 9
1 - 7 keV
2 - 6 keV
3 - 5 keV
4 - 4 keV
5 - 3 keV
6 - 2 keV
7 - 1 keV
8 - 0.5 keV
9 - 0 keV
E
γmin
= 25.5 keV
E
γmin
=50 keV
E
γmin
= 120 keV
∆E
γ
∆E
γ
∆E
γ
Fig. 1. The relative number of incoherently scattered photons
cut off from the X-ray image versus the energy resolution ΔE of
the detector. The plots are given for different energy spread
values in the initial X-ray beam ΔEγ: a) Eγmin = 25.5. keV,
b) Eγmin= 50 keV, c) Eγmin= 120 keV
The analysis of data presented in the figure shows the
application of threshold detectors for X-ray imaging to be
most efficient in the case of using the X-ray radiation
beams of energies higher than 50 keV. The detector that
forms the X-ray image must have the energy threshold
close to the initial photon beam energy. For example, in
the digital radiography with the application of CCD
matrices it appears possible to image only with the use of
those photons registered, whose energy exceeds a certain
threshold value. For threshold detectors with the 2.5 keV
energy resolution and for X-ray beams with an energy
spread of ± 1 keV, about 85% of background (Compton)
photons will be rejected from the image.
One of the interesting variants of threshold detector is
a common X-ray film. It is just the radiation absorbed in
silver halide (AgBr) that mainly forms the X-ray image.
The X-ray quanta of energy slightly higher than the K-
edge (13.470 keV for Br and 25.5165 keV for Ag) are
absorbed nearly 2.5 times more intensively than the
photons having the energy slightly lower than the K-edge.
In other words, if we use a monochromatic initial X-ray
beam of energy equal, e.g., to 25.52 keV, we shall
automatically obtain the image on the film, where the
scattered photons will be essentially suppressed.
In fact, the X-ray film is a threshold detector with an
accuracy of discrimination ΔE ≈ 8.6 eV (full width at half
height of K-line of silver). Therefore, if the primary X-ray
beam (e.g., PXR) has the energy spread, e.g., from 25.52
to 25.82 keV, then ~ 90% of photons incoherently
scattered in the sample will fall into the region of a lower
absorption of photons in the photoemulsion (see Fig. 1).
Considering that these 90% of photons will be absorbed
in the photoemulsion by a factor of 2 worse than the
remaining 10%, the percentage of incoherently scattered
photons eliminated from the X-ray image is estimated to
be ~ 45%.
Thus, by using quasimonochromatic X-ray quantum
beams of energy slightly higher than the absorption K-edge
in silver (25.52 keV) it is possible to increase the image
contrast of a common X-ray film.
3. CONSIDERATION OF COHERENTLY
SCATTERED QUANTA
It has been demonstrated above that the application of
threshold detectors may cut off 45 to 85% (and more) of
photons incoherently scattered in the sample under
irradiation. However, the incoherently scattered photons
make up only a part of the total number of scattered
(coherently and incoherently) photons that deteriorate the
X-ray image contrast. In the coherent interaction of the
photon with the atom of substance it is only the direction
of photon motion that changes, but the photon energy
remains unchanged. Therefore, these scattered photons
cannot be cut off by the threshold detector.
The totalВ ratio of the number of incoherently
scattered photons eliminated from the image to the total
number of scattered (coherently and incoherently)
photons is equal to
/( )total s inc inc cN N N=В В + , (6)
where incN , cN denote, respectively, the number of
photons scattered incoherently and coherently to the
forward semisphere (falling on the detector), sВ is the
percentage of incoherently scattered photons excluded by
the threshold detector from X-ray imaging.
Taking into account that more than three fourths of
coherent scattering acts occur at angles smaller than the
characteristic angle ( )[ ]1 3 22 arcsin 0.026c Z mc Eγθ =
227
([1]) and that no less than a half of incoherently scattered
photons is scattered to the forward semisphere, for the
lower limit of the ( )
inc inc cN N N+ ratio we shall have
c/( ) /( 2 )inc inc c inc incN N N σ σ σ=+ + , (7)
where inc , cσ σ are the total effective cross sections for
incoherent and coherent scattering, respectively, for the
given substance and given energy of the initial X-ray
beam.
To calculate the ( )
inc inc cN N N+ ratio, we have used
the database and approximation algorithms of the XCOM
program [4]. Figure 2 shows the ( )
inc inc cN N N+ values
versus the X-ray beam energy. The calculation was
performed for different irradiated objects such as water,
skeletal muscles and mamma of man, quartz, stainless
steel and gold. The stoichiometric composition of skeletal
muscles, the mammary gland and cortical bone adult
was taken from ref. [3].
10
1
10
2
10
3
0
0.2
0.4
0.6
0.8
1
E
γ
, keV
N
in
c/(
N
in
c+
N
c)
1
2
3
4
5
6
Fig. 2. The ratio of the number of photons scattered
incoherently to the forward semisphere to the total number of
photons scattered to the forward semisphere versus the energy
of X-ray beam: 1 – water, 2 – mammary gland, 3 – skeletal
muscles, 4 - cortical bone adult, 5 – stainless steel, 6 – gold
From the data presented in the figure 2 it can be seen that
at a photon energy of the primary X-ray beam higher than 70
keV, more than 90% of the photons coming to the detector,
which were scattered from such objects as water, skeletal
muscles, or the mamma, are the incoherently scattered
photons. These photons can be cut off by means of a
threshold detector. For example, if the mamma is X-rayed
with the X-ray beam of energy of ~ 120 keV and with an
energy spread of ± 1 keV, then up to 85% of incoherent
photons can be cut off from the image, if a threshold detector
with the 2.5 keV accuracy of energy discrimination is used
for image registration. This will make about 80% of the total
number of non-ballistic photons. This result makes it
possible to improve considerably the image contrast, and, as
a consequence, to reduce the radiation dose for the patient.
Similar estimates hold for any irradiated objects, whose main
composition by weight is made up by light elements. The use
of threshold detectors for imaging from substances, whose
main composition by weight is determined by heavy
elements, will not be so effective because of a substantial
part of coherently scattered photons.
4. CONCLUSION
The use of detectors with an energy threshold
discrimination of the radiation registered may substantially
improve the contrast of X-ray image due to the cutoff of a part
of incoherently scattered photons. The number of incoherently
scattered photons eliminated from the image is determined by
the energy resolution of the detector and by the characteristics
of the initial X-ray beam (energy and energy resolution), and
may make up to 80% of the total number of non-ballistic
photons in the case of imaging from the samples, whose main
composition by weight is determined by light elements. The
image contrast of a common X-ray film may also be improved
by applying quasimonochromatic X-ray quantum beams of
energy slightly higher than the absorption K-edge in silver
(25.52 keV). PXR- and CB-based sources may be used as
energy-readjustable quasimonochromatic X-ray beams [5].
This paper became possible partially due to Grants
1031 and 1030 from Science and Technology Center in
Ukraine.
REFERENCES
1. Alpha-, Beta- and Gamma-Ray Spectroscopy / Ed. Kai
Siegbann. Amsterdam: North-Holland Publ. Company,
1965, v.1.
2. X-ray fluorescence analysis / Ed. By N.F. Losev.
Novosibirsk: Nauka, 1991 (In Russian).
3. H.Q Woodard and D.R White. The composition of body
tissues //Brit. J. Radiology. 1986, vol. 59, p. 1209.
4. M.J. Berger, J.H. Hubell // XCOM: Photon Cross Section
on a Personal Computer. National Bureu of Standarts
Internal Report NBSIR 87-3597, 1987, disk updated to
1994.
5. Scientific Designing of X-Ray Beam Generator for Control
of Nuclear Materials. Proceedings of the STCU Project
1031, v.1 / ed. A.V. Shchagin. Kharkov: KIPT, 2003.
ПРИМЕНЕНИЕ ПОРОГОВЫХ ДЕТЕКТОРОВ ДЛЯ УВЕЛИЧЕНИЯ КОНТРАСТНОСТИ
РЕНТГЕНОВСКИХ ИЗОБРАЖЕНИЙ
В.В. Сотников, В.А. Воронко, А.В. Щагин, В.М. Санин
Рассматривается эффективность применения детекторов с пороговой дискриминацией регистрируемых излучений
(“пороговых детекторов”) для увеличения контрастности рентгеновских изображений, получаемых с помощью
квазимонохроматических рентгеновских пучков. Пороговые детекторы позволяют отсечь из формируемого
рентгеновского изображения некогерентно рассеянные фотоны, и тем самым увеличить контрастность изображения
и/или уменьшить дозу облучения.
ЗАСТОСУВАННЯ ГРАНИЧНИХ ДЕТЕКТОРІВ ДЛЯ ЗБІЛЬШЕННЯ КОНТРАСТНОСТІ
РЕНТГЕНІВСЬКИХ ЗОБРАЖЕНЬ
В.В. Сотников, В.О. Воронко, А.В. Щагин, В.М. Санін
Розглядається ефективність застосування детекторів із граничною дискримінацією випромінювань (“граничних
детекторів”) для збільшення контрастності рентгенівських зображень, одержуваних за допомогою
квазимонохроматичних рентгенівських пучків. Граничні детектори дозволяють відітнути з формованого
рентгенівського зображення некогерентно розсіяні фотони, і тим самим збільшити контрастність зображення і/або
228
зменшити дозу опромінення.
229
|
| id | nasplib_isofts_kiev_ua-123456789-79817 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T17:18:55Z |
| publishDate | 2005 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Sotnikov, V.V. Voronko, V.A. Shchagin, A.V. Sanin, V.M. 2015-04-04T20:34:44Z 2015-04-04T20:34:44Z 2005 Application of threshold detectors for increasing of the contrast in X-ray images / V.V. Sotnikov, V.A. Voronko, A.V. Shchagin, V.M. Sanin // Вопросы атомной науки и техники. — 2005. — № 2. — С. 226-228. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 95.55.Ka; 41.50+h; 41.60-m https://nasplib.isofts.kiev.ua/handle/123456789/79817 Efficiency in the use of detectors with threshold energy discrimination of radiation (“threshold detectors”) for improvement of contrast in X-ray images in quasimonochromatic X-rays is considered. The threshold detectors would allow to eliminate registration of X-rays with energy below of the energy of incident monochromatic X-ray beam. Therefore, incoherent scattered photons will not be registered and contrast will be increased and/or total dose may be reduced. Розглядається ефективність застосування детекторів із граничною дискримінацією випромінювань (“граничних детекторів”) для збільшення контрастності рентгенівських зображень, одержуваних за допомогою квазимонохроматичних рентгенівських пучків. Граничні детектори дозволяють відітнути з формованого рентгенівського зображення некогерентно розсіяні фотони, і тим самим збільшити контрастність зображення і/або зменшити дозу опромінення. Рассматривается эффективность применения детекторов с пороговой дискриминацией регистрируемых излучений (“пороговых детекторов”) для увеличения контрастности рентгеновских изображений, получаемых с помощью квазимонохроматических рентгеновских пучков. Пороговые детекторы позволяют отсечь из формируемого рентгеновского изображения некогерентно рассеянные фотоны, и тем самым увеличить контрастность изображения и/или уменьшить дозу облучения. This paper became possible partially due to Grants
 1031 and 1030 from Science and Technology Center in
 Ukraine en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma diagnostics Application of threshold detectors for increasing of the contrast in X-ray images Застосування граничних детекторів для збільшення контрастності рентгенівських зображень Применение пороговых детекторов для увеличения контрастности рентгеновских изображений Article published earlier |
| spellingShingle | Application of threshold detectors for increasing of the contrast in X-ray images Sotnikov, V.V. Voronko, V.A. Shchagin, A.V. Sanin, V.M. Plasma diagnostics |
| title | Application of threshold detectors for increasing of the contrast in X-ray images |
| title_alt | Застосування граничних детекторів для збільшення контрастності рентгенівських зображень Применение пороговых детекторов для увеличения контрастности рентгеновских изображений |
| title_full | Application of threshold detectors for increasing of the contrast in X-ray images |
| title_fullStr | Application of threshold detectors for increasing of the contrast in X-ray images |
| title_full_unstemmed | Application of threshold detectors for increasing of the contrast in X-ray images |
| title_short | Application of threshold detectors for increasing of the contrast in X-ray images |
| title_sort | application of threshold detectors for increasing of the contrast in x-ray images |
| topic | Plasma diagnostics |
| topic_facet | Plasma diagnostics |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79817 |
| work_keys_str_mv | AT sotnikovvv applicationofthresholddetectorsforincreasingofthecontrastinxrayimages AT voronkova applicationofthresholddetectorsforincreasingofthecontrastinxrayimages AT shchaginav applicationofthresholddetectorsforincreasingofthecontrastinxrayimages AT saninvm applicationofthresholddetectorsforincreasingofthecontrastinxrayimages AT sotnikovvv zastosuvannâgraničnihdetektorívdlâzbílʹšennâkontrastnostírentgenívsʹkihzobraženʹ AT voronkova zastosuvannâgraničnihdetektorívdlâzbílʹšennâkontrastnostírentgenívsʹkihzobraženʹ AT shchaginav zastosuvannâgraničnihdetektorívdlâzbílʹšennâkontrastnostírentgenívsʹkihzobraženʹ AT saninvm zastosuvannâgraničnihdetektorívdlâzbílʹšennâkontrastnostírentgenívsʹkihzobraženʹ AT sotnikovvv primenenieporogovyhdetektorovdlâuveličeniâkontrastnostirentgenovskihizobraženii AT voronkova primenenieporogovyhdetektorovdlâuveličeniâkontrastnostirentgenovskihizobraženii AT shchaginav primenenieporogovyhdetektorovdlâuveličeniâkontrastnostirentgenovskihizobraženii AT saninvm primenenieporogovyhdetektorovdlâuveličeniâkontrastnostirentgenovskihizobraženii |