3 d facial imaging

RECENT ADVANCES
IN DIAGNOSTIC AIDS
www.indiandentalacademy.com

3 D FACIAL IMAGING
THE CUTTING EDGE

• Principles of 3d imaging
• Over view of different techniques
Stereophotogrammetry
3d laser scanning
3d cephalometry
3D facial morphometry
Moire topography
3d cone beam ct scanning
• Applications of 3d imaging

3D FACIAL IMAGING

3 D DENTAL IMAGING

PROCESS OF ACQUIRING 3 D
IMAGE
• In 3D medical imaging set of
anatomical data is collected using
diagnostic imaging equipment.

IMAGE
• Then processed by a computer and
then displayed on a 2D monitor to give
an illusion of depth.

IMAGE
• Depth perception causes the image to
appear in 3D.

Applications of 3D imaging
• Pre post orthodontic assessment of dento-skeletal and
facial relationships.
• Auditing orthodontic outcomes in regard to soft and hard
tissue.
• 3D treatment planning
• 3D soft and hard tissue simulation
• 3D customized arch wires
• Archiving 3D facial,skeletal and dental planning for in
treatment records.
• Research and medico legal purpose are also benefits of
3D imaging.

Historical background
• Singh and Savara ( angle orthodontist
1966) 3D analysis of maxillary growth
changes in girls.
• Thalmann and degan ( 1944) reported
the use of stereophotogrammetry.

PRINCIPLES

STEPS IN 3D IMAGING

MODELLING

TEXTURE MAPPING

Shading and lighting

RENDERING

APPROACHES TO 3D IMAGING
• Udupa and Herman ( 3d imaging in
medicine 1991).

SLICE IMAGING

VOLUME IMAGING

PROJECTIVE IMAGING

MEASURING SCANNED OBJECTS
• Orthogonal measurement
• Measurement by triangulation

ORTHOGONAL MEASUREMENT
X
Y
Z

MEASUREMENT BY
TRIANGULATION

VARIOUS TECHNIQUES
• 3D Cephalometry
• 3D CT scanning
• 3D laser scanning
• Moire topography
• Structured light technique
• Stereophotogrammetry

3D CEPHALOMETRY
• Drawbacks
– Time consuming
– Exposes the patients to radiation
– Does not define soft tissue and there are
difficulty in relating accurately the same
landmarks in two radiographs ,especially in
biplanar technique.

3D LASER SCANNING
Advantages –
Less invasive technique for capturing
face for planning or for evaluation
outcomes of treatment.

Disadvantages –
- slowness of method, making distortion of
scanned image likely.
- safety issues of exposing eyes to laser
beam, especially in growing children.
- inability to capture soft tissue texture, which
results in difficulties in identification of
landmarks that are dependant of surface
color.

Moire topography
• Defines 3D information based on the
contour fringes and fringe intervals.
• Difficulties are encountered if the
surface has sharp features.
• Care to be taken about positioning of
the head.

• Motoyoshi et al ( AJO 1992)
described the system and concluded
that it does not capture facial texture
and subsequent landmark identification
is difficult.

STRUCTURED LIGHT TECHNIQUE
• Light is used to illuminate the scene
and only one image is required.
• The position of the illuminated points in
the captured image compared to their
position on the light projection plane
provides the information to extract the
3D co-ordinates of the imaged object.

DRAWBACKS
• To obtain high density image the face
needs to be illuminated several times
with light.this is time consuming and
may alter the position of the head.
• Also the camera does not provide a
1800
ear to ear facial model.

• Techaletpaisarn and Kuroda (Int J Adult
Orthod Orthog surg 1998)
Used two Lcd projectors and Ccd ,and
computer to produce a 3D image.

• Curry et al ( seminar in orthodontics
2001) their system consists of 2
cameras and a projector.
• Texture mapping

STEREOPHOTOGRAMMETRY
• Two cameras configured as a stereo
pair are used to recover 3D distances of
features on the surface of face by
triangulation.

• Uses a portable stereometric camera
along with a plotting instrument .
• Recent advances have enabled
conversion of simple photographs into
3D images.

• Ras et al ( journal of dentistry 1996 )
demonstrated a stereophotogrametric
system that gives 3D co ordinates of
any chosen facial landmarks that can
be measured
• Consists of 2 synchronized semi metric
cameras mounted on a frame with a
difference of 50 cm and a position
convergently with an angle of 15
degrees.

C3D IMAGING SYSTEM
• This is based on use of special digital
cameras and with a special textured
illumination ,with a capture time of 50
milli seconds and is sufficiently cost
effective to be used in daily practice.

• It captures the natural surface
appearance of patients skin and drapes
this texture on the captured 3D model
of the face.
• It offers a life like3D model that can be
rotated tilted and angulated like a
patients head.

3D FACIAL MORPHOMETRY
• Uses 2 CCD cameras that capture the
subject
• real time hardware for recognition of
markers
• software for 3D reconstruction of
landmarks.

• Landmarks are located with a 2mm
hemisphere reflective markers.
• An infra red streptoscope is used to
light up the reflective markers.
• Two side acquisiton is required to
capture the whole face.

DRAWBACKS
• Placement of landmarks on the face is
time and labour consuming
• Reproducibility of landmark is
questionable.
• No life like models are produced to
show natural soft tissue appearance of
the face.

APPLICATIONS OF 3D FACIAL IMAGING
• Assessment of facial deformity and outcome
of surgical and/or orthodontic correction.

• Subjective outcome of deformities, 3D models
are a valuable media for locating the source
of deformity and its magnitude.

• Assessment of outcome can also be
performed easily by visual comparison of pre
and post treatment models placed side by
side.

LAND MARK BASED
SUPERIMPOSITION

3D CT SCANNING
• Surgical outcome and soft to hard
tissue ratio following orthognathic
surgery (Mccance et al BJO 1992)

OPTICAL LASER SCANNING
• Used to assess soft tissue changes
following functional treatment (Morris et
al EJO 1998)
• Following extraction and non extraction
treatment (MORRIS et al AJO DO
2002)
• Following orthognathic surgery (Moss et
al AJO DO 1994)
• Cleft lip and palate (Mccance et al Cleft
Craniofac J 1997)

STEREOPHOTOGRAMMETRY
• Assess the outcome of twin block
treatment (Bourne et al Clin Orthod
2001)
• Combined orthodontic surgical
treatment of class II or class III (Hajeer
et al Int J Adult Orthod Orthognath
2002)

3D FACIAL MORPHOMETRY
• Application in orthodontics and allied
fields (Ferrario et al Plast Reconstr Surg
1999)

RESULTS OF FACIAL CHANGES
• Landmark identification
• Inter landmark distance and angles
• Color millimetric maps
• Volumetric changes

3D Dental Imaging

3D LASER SCANNING
• Difficult procedure
• Safety issues

3D LASER SCANNING OF STUDY CASTS

APPLICATIONS OF 3D IMAGING OF THE
TEETH
Archiving study models (Orthocad)

VIRTUAL ORTHODONTIC PATIENT

• Combining 3D skeletal ct scan with
vision or laser scanning techniques.

XIA TECHNIQUE (IJO 2000)
• Reconstructing 3D soft and hard tissue
models for sequential CT slices using a
surface rendering technique
• Three colouerd potraits (different
colours) were texture mapped onto the
3D mesh
• Validity of construction was not
evaluated nor was the importance of
head postioning

3D CT SKELETAL MAPS AND 3D
LASER MODELS
• Nishi et al and Terraai et al (JOMS
1997)

3D SKELETAL DATA WITH 3D
LASER SCANNING
• Okumura et al (AJO DO 1999)
• This cannot be used for prediction of
soft tissue changes following treatment.

3D CEPH DATA WITH 3D LASER
SCANNING
• Chen and chen
(Int J Adult Orthod Orthognat Surg
1999)
• 3D computer aided simulation system to
plan surgical procedures an to predict
post operative changes in orthognathic
surgery patients

3D SPIRAL CT SCAN AND
STEREOPHPTOGRAMMETRY
• Khanay et al (Int J Adult Orthod
Orthognat Surg 2002)

CRANIOFACIAL RESEARCH
• Tie points( landmarks placed on speific
areas of the face prior to imgaing).
• Anatomic areas marked on the x ray act
as refrence points.

Teleradiology
• Teleradiology is the electronicTeleradiology is the electronic
transmission of radiological imagestransmission of radiological images
from one location to another for thefrom one location to another for the
purposes of interpretation and/orpurposes of interpretation and/or
consultationconsultation

• When a teleradiology system is used toWhen a teleradiology system is used to
produce the official authenticatedproduce the official authenticated
written interpretation,- there should notwritten interpretation,- there should not
be a significant loss of spatial orbe a significant loss of spatial or
contrast resolution from imagecontrast resolution from image
acquisition through transmission to finalacquisition through transmission to final
image displayimage display..

RECENT ADVANCES
IN DIAGNOSTIC AIDS
Dr. Sathwik. B. S.

3D cone beam c t scan

Conventional c t scan
• Developed by Godfrey hounsfeld (1967)
• Different generations based on
organization of the individual parts of
the device and physical motion of the
beam of capturing the data.

First generation
• Single radiation source and a single
detector.
The information obtained by slice and
slice.

Second generation
• Multiple detectors within the plane of
scan.
• These were not continuous nor did they
scan the diameter of the object.

Third generation
• Advancement in data acquisition and
detector
• Fan beam ct.
• Ring artifacts were seen on the image
often distorting the 3D image and
obscuring certain landmarks.

Fourth generation
• A moving radiation dose and a fixed
detector ring were introduced.
• More scattered radiation were seen.

Fifth generation
• To reduce motion or scatter artifacts.
• The detector is stationary and electron beam
is swept along a semi circular tungsten strip
anode.
• The radiation is produced where the electron
beam hits the anode and this results In an x
ray that rotates about the patient without any
translation or scatter.
• 4D motion picture

limitations
• Considerable physical space.

limitations
• Much more expensive.

limitations
• Stacking procedure (time consuming
and expensive).
• Radiation exposure was primarily
responsible for limiting its usage.

CBCT (cone beam CT scan)

• Developed to overcome some of the
limitations of conventional ct scanning.

Procedure
• Object is captured by a 2 d detector so
that a single rotation can capture the
area of interest
• Cone beam also produces less
scattering of radiation.
• Radiation exposure is 20% of
conventional c t ( equal to full mouth
IOPA)

Advantages of CBCT
• Reduction in the cost

Advantages of CBCT
• Smaller in size
• Exposure chamber (head) is custom
built and reduces the amount of
radiation

Advantages of CBCT
• Images are comparable to conventional
c t and are displayed as full head view
or regional components.

• CBCT machines are available for
different size,possible settings,area of
image capture and field of view.

Acquisition systems
• New tom 3 g (quantitative radiology Italy)
• I cat ( imaging sciences international USA )
• C b mercury ( Hitachi medical corp., japan)
• 3 d acuitomo ( J morita mfg corp. ).

New tom 3 g
• Image capture is done in 36 sec.
• Voxel resolution of .125mm.
• They can be incorporated into dicom 3
d software for analysis.

I cat
• 20 – 40 sec image
capture time
• Field view of 20 x 25
cms can be obtained .
• Amorphous silicon flat
panel detector
produces no distortion.

Cb mercury ray
• Image intensifier and a solid state ccd.
• Gives 288 views in 10 sec .

3 d accuitomo
• Field of view 30x40 mm focuses on
regional and anatomical investigations
• Small size ( 1.6 times an OPG unit ).

Clinical applications

Impacted teeth

Airway analysis
• Aboudara et al (orthod craniofac 2003)
• Showed variability in the upper airway
space compared with lateral ceph.

Assessment of alveolar bone height
and volume
• Hatcher et al ( 2003) site for implant
placement.

Lateral and frontal cephalometric
views

Advantages over other cephalograms
• True 1:1 representation of the structure
being imaged.
• Avoiding superimposition of irrelevant
structures.

3 d skeletal views

3 d facial analysis

Alveolar ridge shape and volume

3 d review of dentition

TMJ analysis

Radiation exposure
• Depends on the kvp and ma.

Alara principle
• Radiographs on the patient needs
• Using the fastest film compatible with
the diagnostic task
• Collimating the size of the beam to as
close o film size.
• Using lead aprons and thyroid shields.

Drawbacks
• Map out the muscle structures and their
attachments
• True colour texture of the skin cannot
be captured
• Long capture time of the full view of a
subject ( 30 –40 sec).
• High costs

Resorption of incisors after ectopic
eruption of maxillary canines:
a CT study
• Angle orthodontist 2000 (Sune Ericson
and Kurol)

Superimposition of 3D cone beam CT
models of orthognathic surgery
patients
• British journal of radiology 2005
(Bailey et al)

MRI scan

• Formerly called as NMR ( nuclear
magnetic resonance )
• Primarily used to demonstrate the
physiological or pathological alterations
in living tissues.

History of MRI
• Developed by Dr. Raymond Damadian
and a group of graduate students at
downtown medical centre.
• First performed in July 1997.
• Paul Lauterbur and sir Peter Mansfield
were awarded the Nobel prize in 2003.

• What is an MRI scan
• How does a MRI scanner work
• What does a MRI scan show
• When are MRI scans done
• How is an MRI scan done
• Difference between an MRI and CT
scan
• Risks and safety issues concerning an
MRI scan www.indiandentalacademy.com

What is a MRI scan?
• Is a radiological technique that uses
magnetism, radio waves and a
computer to produce images of body
waves.

How does a MRI scanner work
• Radio waves 10,000 – 30,000 times
stronger than the magnetic field of earth
are sent through the body.
• Body produces radio waves of its own.
• Scanner picks up these signals and a
computer turns them into an image.

What does an MRI scanner show
• It is possible to
make pictures of
all body
structures.
• Less hydrogen
atoms (darker).
• More hydrogen
atoms (brighter).

• It is possible to get clear pictures of
body that are surrounded by bone
tissue (brain and spinal cord).
• Best technique to find out tumors
especially of the brain .
• MULTIPLE SCLEROSIS (BLEEDING)
and lack of oxygen or stroke.

When are MRI scans used
• Brain tumors
• Integrity of spinal cord after trauma.
• Structure of the heart and aorta.
• Accurate information of the joints, soft
joints and bones inside the body.
• Surgeries can be accurately directed
after MRI.

Dental applications
• Relation of orthodontics and TMD
(Temperomandibular disorders).
• Post treatment
• Results of orthognathic surgeries.
• Effects of mandibular advancements in
obstructive sleep apnea.

How is an MRI scan performed?
• Out patient procedure
• Patient needs to relax.
• All metallic objects need to be removed
before the scan
• Remove all hearing aids or pace
makers.

• Loud clicking noises are heard which
may be uncomfortable for the patient.
• Iv injections are necessary to enhance
the images

• Water
• Paramagnetic contrast compound
(gandolium compound)
• Super-magnetic contrast agents (iron
oxide nano particles)
• Diamagnetic agents (barium sulphate)

Safety procedure
• Implants and foreign objects

Ferromagnetic foreign bodies
• Shell fragments
• Metallic implants

Reactions
• Trauma due to movement of objects in
magnetic field
• Thermal injury
• Failure of an implanted device

Projectiles
• Missile effect accidents ( attractions of
ferromagnetic objects towards Center of
magnet)

Radiofrequency energy
• Hyperthermia in children.

Acoustic noise
• 130 db ( jet engine take off)
• Appropriate use of ear protection

Cryogens
• Emergency shut down of
superconducting magnet leads to an
operation called quenching.
• Release of helium and risk of
asphyxiation.
• Recommissioning of magnet is
extremely expensive

Is MRI scan dangerous
• There are no known side effects.
• Within first 12 weeks of pregnancy.
• Because of large cylinder the procedure
may be claustrophobic.

Specialized MRI scans
• Diffusion MRI scanning
- diffusion tensor imaging
- diffusion weighted imaging
• Magnetic resonance angiography
• Magnetic resonance spectroscopy
• Interventional MRI
• Radiation therapy stimulation
• Current density imaging

Applications of MRI scanning

MRI of pharynx and treatment
efficiency of mandibular advancement
in OSPS
• Eur resp j 2002 (Sanner et al )

Orthodontics and TMD
• AJO DO 2002 (Grabber et al )

Frankel appliance therapy and TMD
• AJO DO 2002 (Franco et al )

Rigid versus wire fixation for
mandibular advancement
• AJO DO 2002 (Dolce et al )

Changes in condylar disc position and
tm after disc repositioning therapy
• Angle orthodontist feb 2000 (Hatice and
Turkharmann)

3 d facial imaging

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