BY DR. ADHIRAJ GHOSH

1. SEMINAR PRESENTATION
Topic: Advanced Imaging Modalities
in Maxillofacial Surgery.
Presented by:
Adhiraj Ghosh,
PGT, Dept. of Oral & Maxillofacial,
Surgery, HIDSAR.

2. 3 Timelines
• Imaging for Diagnosis ( 1818 – 1980).
• Advanced imaging ( 1980 – 2000).
• 3D Imaging and Treatment Planning
(2000 to Present).

3. Imaging for Diagnosis
Conventional Radiography,
Sialograms,
Ultrasonography,
Fluoroscopy,
Angiography,
Tomography.

4. Sialography
• Sialography visualises the ducts and the
parenchyma of the salivary gland, after
contrast administration into the main salivary
duct.
• In 1925 the advent of iodized oil (lipiodol) as
the first non-toxic contrast agent made
evaluation of the salivary ductal system
possible.

5. • In this method the stenson’s/ warthon’s duct
is first identified and cannulated with the help
of Rabinov sialography catheter.
• 1-1.5 ml of contrast is then injected
retrogradely , slowly to fill the ducts and the
glandular parenchyma.
• The glands are viewed in the lateral and sub-
mentovertex projections.

6. Conventional sialography of submandibular (A) and parotid glands (B) showing ductal system

7. Sialography with Digital substraction
• Digital subtraction sialography was first reported by
Gullotta in 1983
• The use of post-processing enables for a subtraction of a
bony background and contrast enhancement of the salivary
ducts.
• In this method, first a control image is taken then contrast
is introduced and a series of pictures taken.
• The duct is then decannulated to prevent contrast
remaining and again control image taken for next
projection.
• DSS can be done under fluoroscopic control to obtain
dynamic view of the ductal system.
• The operator is able to view the duct filling during injection.

9. Sialoendoscopy
• It is an endoscopic technique that allows
complete exploration of the salivary ductal
system and a precise evaluation of its
pathologies.
• Two types:
• Diagnostic sialendoscopy
• Interventional sialendoscopy

10. Indications and Contraindications
• Salivary gland swellings of unclear origin,
• Calculi,
• Strictures,
• Inflammation,
• Tumor, and
• Other causes that may cause obstruction of
the duct.

11. Equipment

14. Ultrasonography
• Ultrasound is an imaging modality that utilizes
high-frequency sound waves to provide cross-
sectional images of the body.
• Its main advantage is that it is noninvasive,
painless, rapid and inexpensive and gives
accurate details of soft tissues without much
distortion.
• Images are acquired in real-time and can be
acquired in any imaging plane.

15. • The principle of USG is based on the fact that,
there are large differences in the impedance for
ultrasound waves between soft tissue and air,
and between soft tissue and bone. Bone and air
are absolute barriers to an ultrasound beam, this
means that no image within or behind bony or air
containing structure can be produced by
ultrasound.
• Therefore some regions of maxillofacial field
cannot be evaluated by ultrasound, such as the
retropharyngeal region and paranasal sinuses.

16. The Transducer
• A transducer performs two functions: it emits
sound waves (echoes) at a certain frequency
and captures the returning echoes .
• US frequency ranges from 2 to 20 MHz
• High-frequency transducers (up to 10–15 MHz
range) to image superficial structures and
• Low-frequency transducers (typically 2–5
MHz) for imaging the structures that is deep in
most of the cases.

19. Clinical Applications

20. Space Infection
• USG is an effective diagnostic tool to confirm
abscess formation in the superficial facial
spaces and is highly predictable in detecting
the stage of infection.
• It has the ability to pinpoint the relation of the
abscess to the overlying skin, accurately
measure the dimensions of the abscess cavity
and its precise depth below the skin surface.

22. Osteomyelitis
• Ultrasound detects certain features of
osteomyelitis several days ahead of
conventional radiographs.
• Juxtacortical soft-tissue swelling together with
early periosteal thickening is the earliest sign
of acute osteomyelitis on ultrasound.

23. Vascular Malformations
• Doppler ultrasound is used for vascular studies.
• The information provided by a Doppler examination
includes presence or absence of blood flow, direction
of blood flow, type of blood flow (arterial high
resistance/venous, presence and quantification of
arterial stenosis etc.
• A high-frequency linear array transducer (5–10 MHz) is
used.
• The target of color Doppler imaging is the moving
blood cells within the blood vessel.
• Blood flowing towards the USG transducer is displayed
as red and that moving away from transducer as blue.

24. A Color Doppler scan of common carotid artery

25. Features of inflammatory process – hypoechogenic parenchyma with increased blood
flow in Power Doppler.

26. Cervical Lymphnodes Metastasis
• Ultrasound with a high-resolution real time
linear scanner with 7.5 MHz transducer is
used to detect the nodes.
• Scans are evaluated for,
1. Presence of definite internal echoes,
2. Homogeneous hilar echoes and
3. The ratio of the short and long axis (L/S
ratio).

28. Criteria for USG
1. A lymph node with definite internal echoes is defined as
malignant.
2. A lymph node with hilar but no definite internal echoes is defined
as benign.
3. A lymph node measuring 10 mm or more in the short axis is
defined as malignant.
4. A lymph node with an L/S ratio of 3.5 or more is considered
benign.
5. A lymph node which cannot be associated to categories 1–4 is
considered to be questionable.

30. Fractures
• McCann et al. used ultrasound with 85 %
accuracy in diagnosing fractures of the
zygomatico-orbital complex (ZMC) and the
anterior wall of the frontal sinus.

32. Tissue Harmonic Imaging
• THI is a advanced form of USG where higher
harmonic frequencies (multiples) generated
by the propagation of the ultrasound beam
through tissues are used to produce the
image.
• It provides images of higher quality than
conventional sonography.
• Harmonic imaging provides additional
information in both solid and cystic lesions.

33. Tissue harmonic imaging (A) demonstrates much better delineation of both cystic and
solid lesions , when compared to conventional gray scale imaging (B)

34. Fluoroscopy
• Fluoroscopy is an imaging modality that uses x-
rays to allow real-time visualization of body
structures. During fluoroscopy, x-ray beams are
continually emitted and captured on a screen,
producing a real-time, dynamic image. This allows
for dynamic assessment of anatomy and function.
• High density contrast agents may be introduced
into the patient to allow for greater
differentiation between structures.

35. Common clinical applications
• The C-arm fluoroscope, can be effectively
utilized for intraoperative radiographic
support in the Oral Maxillofacial region.
• Accidental displacement of metallic or other
radiographically detectable fragments into the
surrounding tissue spaces.
• Fistulography: for the evaluation of fistulae.
• Reduction of fractures under image guidance.

37. Angiography
• Angiography is the use of fluoroscopy to view the
cardiovascular system. An iodine-based contrast is
injected into the bloodstream and watched as it travels
around. Since liquid blood and the vessels are not very
dense, a contrast with high density (like the large
iodine atoms) is used to view the vessels under X-ray.
Angiography is used to find aneurysms, leaks,
blockages (thromboses), new vessel growth, and
placeent of catheters and stents.
• Balloon angioplasty is often done with angiography.

38. Digital substraction angiography
• In OMFS digital substraction angiography is
primarily used to evaluate vascular lesions like
AVMs.
• For this a catheter is introduced into the femoral
artery and manipulated under fluroscopic control
to reach the lesion.
• A contrast media is then introduced and
angiograms taken.
• These pictures can then be used by the
Interventional radiologist for therapeautic
purposes like Embolization of the vessels.

39. Advanced Imaging
• Computed tomography (CT)
• Cone-beam (CB) CT,
• Magnetic resonance imaging (MRI),
• Nuclear medicine including positron emission
tomography (PET).

40. Computed Tomography
• Sir Godfrey Hounsfield developed the first
commercially available CT scanner in 1972.
• CT scanner consists of an x-ray tube and
detectors which measure the number of photons
that exit the patient.
• The photons recorded by the detectors represent
the absorption characteristics of all elements in
the path of x-ray beam.
• Computer algorithms use these photon counts to
construct one, or many digital cross-sectional
images.

41. • The first-generation CT scanners acquired the
data in the axial plane by “slice-by-slice” scanning
with a narrow fan-shaped X-ray beam and a
single array of detectors.
• In 1989 CT scanners were introduced that acquire
image data in a helical / spiral fashion- high-
quality 3D imaging.
• Multidetector helical CT scanners were
introduced in 1998.
• It is important to note that all these detectors
were linear detectors.

44. • Early CTs could take images of a single plane at a time.
• Spiral CTs decreased scan time and reduced slice
thickness making 3D reconstruction possible.
• MDCT enable acquisition of several (as many as the
number of detectors or “slices”) images at once.
Sixteen-slice scanners have been widely available for
years, while 64-slice MDCT scanners became available
in 2004.
• MDCT has made multiplanar reconstruction possible
thus obviating the need for direct imaging of the
saggittal and coronal planes.

47. • Contrast media may be employed during a CT
study.
• It helps to distinguish structures of similar
density in the body.
• Many abnormalities, such as bleeding,
extravasation or neoplasms become more
evident through contrast perfusion.
• Iodine-based IV contrast medium is used for
most CTs.

48. CT Physics
• The more dense a tissue, the more X-rays it
absorbs.
• Bone: X-rays absorbed = few X-rays reaching
detector: White
• Air: X-rays not absorbed = lots of X-rays reaching
detector: Black
• Density of tissues on CT:
Air < Fat < Fluid < Soft tissue < Bone < Metal

49. Windowing
• A small range of tissue density is represented
by a full grey scale spectrum from black to
white, thus making subtle density differences
within the specified range easier to see.
• Examples of commonly used windows are soft
tissue, lung, and bone.
• A soft tissue window is used to view most
organs.
• A bone window is used to view bone detail.

51. ADVANTAGES OF CT
• Eliminates the superimposition of images.
• Differences between tissues that differ in
physical density by less than 1% can be
distinguished.
• Data from a single CT imaging procedure can
be viewed as images in the axial, coronal, or
saggittal plane. This is referred to as
multiplanar reformatted imaging.

52. Trauma
• CT is the imaging modality of choice for
extensive maxillofacial trauma cases.
• Useful for fractures of the orbital region.
• Rarely used to evaluate isolated mandibular
fractures but saggittal fractures of the
condylar head and intracapsular fractures can
be identified very well.
• Trauma of the head and the cervical spine
often coexist with large maxillofacial fractures.

53. Frontal Sinus Fractures

55. ORBITAL FRACTURES
• CT in axial, and coronal planes are essential to
determine presence of fractures and status of
intraocular muscles.
• Axial: medial, lateral wall fracture, entrapment
of medial rectus muscle .
• Coronal: floor, roof fracture, entrapment of
inferior rectus muscle, fracture involving
nasolacrimal duct, fracture of optic canal,
retro-orbital hematoma .

59. Globe rupture is evident by flattening of the posterior wall of the globe “flat tire sign”
and narrowing of the space between cornea and lens “deepening of anterior
chamber”- Vitreous hemorrhage.

60. Traumatic Lens Dislocation

61. ZYGOMATIC FRACTURES

62. ISOLATED ALVEOLAR PROCESS
FRACTURE

63. LEFORT 1 FRACTURE

64. LEFORT II FRACTURES

65. MANDIBULAR FRACTURES

67. Malignant tumours
• CT is very sensitive for detecting small areas of
cortical bone invasion.
• MRI is better for evaluating the extent of bone
marrow invasion by the tumour.
• Iodine contrast enhanced CT studies are used.
• The size, shape, necrosis and extracapsular
spread of the lymph nodes are evaluated.
• Assessment of invasion of vital structures, i.e.
common or internal carotid artery, internal
jugular vein, the skull base or thoracic inlet, is
also indicated.

69. Benign (odontogenic) tumours, cysts,
bone abnormalities
• The contrast-enhanced images are considered
to be useful for example differentiating
odontogenic cysts, which show rim
enhancement, from tumours consisting of
solid components.

70. Neck infections
• Deeply located abscesses cannot be evaluated
with USG and contrast enhanced CT
examination is indicated.
• In CT images an abscess appears as a single or
multiloculated low-density area, with or
without gas collection.
• Airway narrowing can be better visualised
with CT.

72. CONE BEAM COMPUTED TOMOGRAPHY
(CBCT)
• CBCT was introduced in the early 2000s.
• Cone-beam CT scanners use a cone-shaped
beam, rather than a fan-shaped beam of x-rays.
• It is a form of imaging in which a single projection
obtains volumetric data from where a 3D image
can be reconstructed.
• Cone beam CT (CBCT) uses a high-resolution two
dimensional detector instead of a series of row of
one dimensional (1D) detector elements as in
MDCT.

74. CBCT scanners are connected to a computer, and the data or the region of interest
is acquired with a single full 360° or partial rotation of the cone-shaped X-ray beam
and reciprocal rotating single image detector around the patient’s head.

75. • During rotation, multiple sequential planer projection images are obtained while the
x-ray source and detector move through an arc of 180 to 360 degree.
• Usually several hundred 2-D basic images from which the image volume is calculated.

77. CBCT is also called the “THIRD EYE
IN IMPLANTS.”

78. CBCT images produced for dental implant treatment planning. (a) reconstructed
panoramic and (b) crosssectional views. Inferior alveolar nerve marking is also
shown by red line. (c and d) Coronal CBCT views show corticated inferior alveolar canal
(green arrows) and the mental foramen (red arrows)

79. Advantages of CBCT in implant
dentistry.
1. Evaluates all possible sites and anotmical structures.
2. No superimposition
3. Uniform magnification
4. Simulates implant placement with implant planning
software
5. CBCT dose of radiation exposure is less than that
produced by CT scanning
6. Can limit radiation exposure according to Field of
View chosen (FOV): small, medium, or large
7. Less expensive than CT scanning
8. Allows for the 3-D evaluation of an arch

80. MRI
• MRI uses an exceptionally strong magnet and radio
frequency waves to generate image. The powerful
magnets polarise and the RF excites hydrogen nuclei
(single proton) in water molecules in human tissue
producing a detectable signal.
• MRI was first demonstrated by Peter Lauterbur, in
1973.
• Current diagnostic MRI scanners use cryogenic
superconducting magnets in the range of 0.5 Tesla (T)
to 1.5 T. However, 3 T systems are now widely available
and are being used regularly in the research setting

81. • When a human body is placed in a large
magnetic field, many of the free hydrogen
nuclei align themselves with the direction of
the magnetic field. The nuclei precess/align
about the magnetic field direction like
gyroscopes. This behavior is termed Larmor
precession.

82. • Next, a radio-frequency (RF) pulse, , is applied
perpendicular to the magnetic field.
• When the RF pulse stops, the nuclei return to
equilibrium This return to equilibrium is referred to as
relaxation. During relaxation, the nuclei lose energy by
emitting their own RF signal. This signal is referred to
as the free-induction decay (FID) response signal.
• FID can be resolved by a mathematical process known
as Fourier transformation, into an image (MRI). To
produce a 3D image, the FID resonance signal must be
encoded for each dimension.

84. • The voxel intensity of a given tissue type (i.e. white matter
vs grey matter) depends on the proton density of the tissue
• MR image contrast also depends on two other tissue-
specific parameters:
1. The longitudinal relaxation time, , and
2. the transverse relaxation time, .
• TR- The period of the RF pulse sequence is the repetition
time.
• TE- The time between which the RF pulse is applied and the
response signal is measured is the echo delay time.
• By adjusting TR and TE the acquired MR image can be
made to contrast different tissue types.

85. T1 Weighted MRI
• Demonstrates good anatomic structures
• Fat and meniscal tears appear bright white
• Water, CSF, muscle, tendons, and ligaments
appears light to dark grey
• Air and cortical bone appears dark

86. T2 Weighted MRI
• Demonstrates contrast between normal and
abnormal (can identify abnormal lesions of
fluid)
• Water and CSF appears bright white
• Fat, muscle, tendons, ligaments and cartilage
appear light to dark gray
• Air and cortical bone appears dark (unless
fluid is in the lung)

89. Other Views
DWI (diffusion weighted imaging): Diffusion restriction is bright
• useful for ischaemic strokes, abscesses, most tumours.
FLAIR (fluid attenuated inversion recovery): Like T2, but Water is dark
• useful for multiple sclerosis (periventricular lesions).
STIR (short tau inversion recovery): Like T2, but fat is dark
• useful for oedema in tissues, abscesses.
MRA (magnetic resonance angiography): Vessels are bright
• useful for AVMs, aneurysms.

90. Clinical applications
• MRI is particularly useful for evaluation of
suspected osteomyelitis and neoplastic
conditions near bone since edema in the bone
marrow and soft tissues can be easily
detected.

91. Contrast
• Gadolinium is a metal-based contrast given IV.

92. Contraindications for MRI
• Pacemakers, aneurysm clips, cochlear
implants, and orbital foreign bodies
• Projectiles in the room (includes oxygen tanks,
IV poles, stethoscopes, hair pins, etc)

93. Difference between MRI and CT:
• Like CT, MRI traditionally creates a two dimensional image of a thin
"slice" of the body and is therefore considered a tomographic
imaging technique.
• Unlike CT, MRI scans do not use X-rays
• Because CT and MRI are sensitive to different tissue properties, the
appearance of the images obtained with the two techniques differ
markedly.
• In CT, X-rays must be blocked by some form of dense tissue to
create an image, so the image quality when looking at soft tissues
will be poor.
• In MRI, while any nucleus with a net nuclear spin can be used, the
proton of the hydrogen atom remains the most widely used,
especially in the clinical setting, because it is so ubiquitous and
returns a large signal. This nucleus, present in water molecules,
allows the excellent soft-tissue contrast achievable .

94. Radionuclide Imaging
• Radionuclide imaging or nuclear medicine is a
diagnostic technology that uses small amounts of
radioactive material to produce images of
internal body.
• radioactive isotopes are given as an injection or
by mouth.
• These isotopes are absorbed by specific organs,
bones or tissues,and produces emissions, which
can be detected by special radiation detectors.
The scanner works with a computer to convert
the emissions into an image.

95. Applications
• Bone scans to evaluate fractures, tumors, or unexplained bone pain.
• Heart scans to identify normal or abnormal blood flow to the heart
muscle, measure heart function, or determine the existence or extent of
damage to the heart tissues after a heart attack episode
• Thyroid iodine scans to analyze the thyroid function and show the
structure of the gland. Larger doses of radioactive iodine are used to
destroy thyroid nodules in case of Graves' syndrome
• Gallbladder or hepatobiliary scans to evaluate both liver as well as
gallbladder function. This test can determine obstructions caused by the
presence of gallstones.
• Lung scans to evaluate the flow of blood and movements into and out of
the lungs, as well as the determination of the presence of blood clots
• Gallium scans to evaluate infection and certain types of tumors.
• Brain scans.
• Gastrointestinal scans.

96. Radioisotopes

97. Gamma Camera
• Gamma camera consists of different components
such as collimator, scintillator, and
photomultiplier tubes.
• The gamma rays, which are not visible to the eye,
are converted into flashes of light by the
scintillation crystal.
• This light is, in turn, transformed into electronic
signals by an array of photomultiplier tubes
(PMT) viewing the rear face of the crystal.
• After processing, the outputs from the PMTs are
converted into images.

99. • Radionuclide imaging includes three
techniques:
• Planner Scintigraphy
• SPECT
• PET

100. Disadvantages of nuclear medicine
• Although contrast of a lesion versus surrounding
tissues is high when radiotracers accumulate in
the lesion, spatial resolution, in general, is poor
compared with radiographs, CT or MRI.
• The radiation exposures are different from
radiographs and CT, which involve external and
generally only partial body exposure, whereas
radionuclide administered into patients causes
internal whole body exposure.

101. Planner Scintigraphy
• Radioisotope such as Tc99m is used.
• Commonly used to examine:
1. Primary and secondary malignancies
2. Inflammatory conditions
3. Metabolic disease
4. Trauma

102. BONE SCAN
• The scan demonstrate areas of altered bone
metabolism within and around the lesion,
thus allowing a reasonably accurate
assessment of the growth of a lesion and
extent of its borders.
• Bone scan gives no information on
morphology of lesion.

103. Types of Bone scan
• Standard whole body scan.
• Three-phase bone scan.

106. SPECT
• Use radiotracers that generate gammay decay
• – Capture photons in multiple directions,
similar to X-ray CT
• – Uses a rotating Anger camera to obtain
projection data from multiple angles
• It obtains tomographic slices

108. PET (Positron emission tomography)
• A PET scan measures important body functions, such as
blood flow, oxygen use, and sugar (glucose)
metabolism, to help evaluate how well organs and
tissues are functioning.
• A radioactive isotope that decays by positron emission
is introduced into the body.
• Many different radioisotopes are there, such as
Fluorine18,
• Oxygen15,
• Carbon11.
• 18F is the most commonly used isotope.

109. • Positron decay produces two photons in two
opposite directions at a time.
• Special coincidence detection circuitry is used
to detect two photons in opposite directions
simultaneously.
• (PROVIDES RADIATION EVENT LOCALIZATION,
THUS INCREASING RESOLUTION OF IMAGES
THAN SPECT)
•

111. ADVANTAGES OF PET
• Non-invasive
• Low-risk infection compared to surgery
• Identifying active diseases after therapy completion
• Outcome of chemotherapy e.g. in non-Hodgkin’s
lymphoma, FDG uptake was found to decrease as early
as 1 d after the initiation of chemotherapy
• Early assessment of response during the first treatment
cycles is important to appreciate chemo-sensitivity and
may potentially guide further risk-adapted therapeutic
strategies in aggressive lymphoma

112. Uses OF PET
• Detect nodal neck disease in OSCC.
• Response of tumor to treatment.
• Detect distant unknown metastasis.
• For occult or micrometastasis.

113. Condylar hyperplasia
• Bone scintigraphy has been used in the
diagnosis and treatment planning of
mandibular condylar hyperplasia for many
years.
• This imaging modality has the ability to detect
abnormalities at an earlier stage before
morphological changes are evident.

114. Lymph node scintigraphy
• Sentinel lymph node mapping.
• Simple and non-invasive functional test for
demonstrating lymphatic pathways.
• Technetium 99m sulphur colloid is injected in 4-6
subcutaneous sites around neoplastic sites.
• Colloid will be carried in lymphatic channels to
first lymph node draining that area, so called
sentinel node.
• Best predictor of nodal spread of tumor.

115. Head and Neck Cancer
• 18F-FDG PET has a significant role in the
diagnosis and management of head and
• neck cancer. It helps in the detection of distant
metastasis.
• Being a modality to assess the metabolic
activity of the malignant cells, 18F-FDG PET
plays a major role in detecting response to the
treatment in chemoradiotherapy.

116. Salivary gland scintigraphy
• Several modalities are known for salivary
gland imaging such as sonography,
sialography, scintigraphy, CT and MRI.
• The parenchymal and excretory function of
salivary glands can be simultaneously
quantified by salivary gland Scintigraphy
• Gland aplasia/agenesis, obstruction, trauma,
as well as fistulas in the glands can be
detected.

117. Temporomandibular joint
• Evaluation of bone metabolism in bony
components of TMJ.
• For assessment of skeletal facial growth.
• Presence of active hyperplastic activity in
these joints.

118. Fibrous dysplasia
• There is a slow and insidious enlargement of
bone which may persist until growth cessation
or continue to adulthood.
• Nuclear medicine demonstrates increased
tracer uptake on 99mTc bone scans.

119. Inflammatory and infectious processes
• A positive bone scan image is seen in
inflammatory conditions such as
osteomyelitis, osteoarthritis, traumatic
injuries, periapical lesions and periodontal
lesions.

120. Bone-graft viability
• Positive scan is correlated with a viable bone
graft.

121. Fusion imaging
• CT and SPECT.
• CT and PET.
• PET and MRI
• Structure and function.

123. Surgical navigation
• The use of a navigation system can improve pre-
operative planning and provide a high degree of
intra-operative accuracy and precision.
• Three primary components:
• A localizer
• an instrument or surgical probe,
• Ct scan data

124. Orientation of system
• Surgical navigation systems use a stereoscopic
camera emitting infrared light which can
determine a 3D position of prominent structures,
like reflective marker spheres.
• During the surgery, the marker spheres are
attached to the patient and at surgical
instruments (using reference arrays) to enable an
exact localization in space.
• The preoperative image data need to be matched
to the current patient position via a registration
process.

126. • Orbital reconstruction- accurate positioning of
plates
• Maxillofacial reconstruction
• Tumor resection-surgery involving the skull
base, pterygomaxillary fossa, or infratemporal
fossa.
• (TMJ) ankylosis release
• Orthognathic surgery

128. Virtual Surgical Planning
• High-resolution computed tomographic (CT) scan
• 3D reconstruction of the CT images
• Stereolithographic models are manufactured of
the area.
• Pre-bent plates can be fabricated.
• In case of tumors the resection and
reconstruction is virtually planned
• Specific cutting guides for both the resection and
the vascularized bone graft that will be used

131. Thank you.