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Medical Physics Support for Dental X‐ray Imaging :
Technology and physics measurements for intraoral systems and accreditation of cone beam CT.
Robert J. Pizzutiello, MS, FACR, FAAPM, FACMP
Residency Program Director, Upstate Medical Physics, PC Senior Vice President, Imaging Physics
LANDAUER Medical Physics
Outline
• Evolution of Dental imaging in Clinical Practice
• Film based dental imaging
– Dose, Image Quality and Consistency
• Digital dental imaging, planar and CBCT
• Dose, Image Quality and Consistency
• Medical Physics Measurements for Dental
Systems
• Accreditation of Dental Imaging Facilities
• Summary and Conclusion
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Learning Objectives
• To understand the factors that affect dose and image
quality in film and digital dental radiography
• To understand the methods of performance evaluation
of dental imaging systems
• To understand the emerging importance of Cone
Beam CT scanning in dental imaging
• To understand the medical physicist’s requirements to
support accreditation of dental practices by the
Intersocietal Accreditation Commission CT program
Film based Intraoral radiography
•
•
Film, no screen, foil backing
D-Speed, E-Speed
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RADIOGRAPHIC TRENDS OF DENTAL OFFICES AND DENTAL SCHOOLS ORHAN H. SULEIMAN et al JADA 1999
RADIOGRAPHIC TRENDS OF DENTAL OFFICES AND DENTAL SCHOOLS ORHAN H. SULEIMAN et al JADA 1999
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Typical Exposure Data, mR
Dental Bite Wing for 2009 (N=7205)
TYPE
Total
% of Total Average
D
3483
55%
256
E
1001
16%
162
F
774
12%
148
T (digital)
1947
31%
105
SD
99
72
63
59
Highest
2150
1320
520
693
Dental Bite Wing for 2005 (N=6325)
TYPE
Total
% of Total Average
D
3084
49%
258
E
1118
18%
162
F
500
8%
140
T (digital)
1623
26%
106
SD
93
70
67
58
Highest
860
786
952
712
Dental Bite Wing for 2001 (N=8600)
TYPE
Total
% of Total Average
D
5127
81%
262
E
1674
26%
161
F
510
8%
148
T (digital)
1289
20%
110
SD
106
68
58
64
Highest
3308
675
650
560
Courtesy NYSDOH
Courtesy Joel Gray, DIQUAD
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Collaborating to
Bring a Unique Solution
New York State Guidelines
240‐350
120‐170
100‐140
Based on the most recent FDA analysis of film based
intraoral radiography, which of the following is a true
statement?
20%
1.
2.
3.
4.
5.
20%
20%
2
3
20%
20%
Newer, faster films can be processed
in half the time previously required
F speed film images use significantly
lower dose than E-speed Film
E and F speed film images use
significantly lower dose than D
speed film
Approximately 90% of film based
dental imaging is now performed
using D speed film
D Speed film images use
significantly lower dose than Espeed Film
1
4
5
10
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Based on the most recent FDA analysis of film
based intraoral radiography, which of the
following is a true statement?
1. Newer, faster films can be processed in half
the time previously required
2. F speed film images use significantly lower
dose than E-speed Film
3. E and F speed film images use significantly
lower dose than D speed film
4. Approximately 90% of film based dental
imaging is now performed using D speed film
5. D Speed film images use significantly lower
dose than E-speed Film
Ref: Conference of Radiation Control Program Directors, Inc. (CRCPD), Publication E‐03‐6, "NEXT Tabulation and Graphical Summary of the 1999 Dental Radiography Survey", November 2003
Advantages of Digital Dental
Radiography
• immediate image production with solid‐state devices such as a charge‐coupled device (CCD) and a complementary metal‐oxide semiconductor (CMOS);
• interactive display on a monitor with the ability to enhance image features and make direct measurements;
• integrated storage, providing access to images through practice management software systems;
• security of available backup and off‐site archiving;
• wide exposure latitude
Ref Farman et al. JADA 2008;139(6 supplement):14S‐19S
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Advantages of Digital Dental
Radiography
• perfect image duplicates to accompany referrals to other practitioners;
• security mechanisms to identify original images and differentiate them from altered images;
• ability to tag information such as a patient identifier, date of exposure and other relevant details;
• interoperability of the (DICOM) file format, which enables practitioners with different equipment and software to view and enhance the same images.
Ref Farman et al. JADA 2008;139(6 supplement):14S‐19S
Typical Exposure Data, mR
Dental Bite Wing for 2009 (N=7205)
TYPE
Total
% of Total Average
D
3483
55%
256
E
1001
16%
162
F
774
12%
148
T (digital)
1947
31%
105
SD
99
72
63
59
Highest
2150
1320
520
693
Dental Bite Wing for 2005 (N=6325)
TYPE
Total
% of Total Average
D
3084
49%
258
E
1118
18%
162
F
500
8%
140
T (digital)
1623
26%
106
SD
93
70
67
58
Highest
860
786
952
712
Dental Bite Wing for 2001 (N=8600)
TYPE
Total
% of Total Average
D
5127
81%
262
E
1674
26%
161
F
510
8%
148
T (digital)
1289
20%
110
SD
106
68
58
64
Highest
3308
675
650
560
Courtesy NYSDOH
7
Ref Farman et al. JADA 2008;139(6 supplement):14S‐19S
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Compared with dental film radiography,
for digital intraoral radiographs:
a) Lower dose is always delivered
b)
c)
d)
e)
20%
20%
20%
b)
c)
20%
to the patient than with film
techniques
Image processing of digital
intraoral radiographs is
comparable to processing time
needed for table top automatic
film processors
Digital dental systems
incorporate new technology to
alert the operator when preset
dose levels have been exceeded
Digital dental imaging systems
have superior spatial resolution
Operators of digital intraoral
radiographs can produce images
over a wide range of doses
a)
d)
20%
10
e)
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Compared with dental film radiography, for digital
intraoral radiographs:
a) Lower dose is always delivered to the patient than with
film techniques
b) Image processing of digital intraoral radiographs is
comparable to processing time needed for table top
automatic film processors
c) Digital dental systems incorporate new technology to
alert the operator when preset dose levels have been
exceeded
d) Digital dental imaging systems have superior spatial
resolution
e) Operators of digital intraoral radiographs can produce
images over a wide range of doses
Ref: Farman and Farman, Oral Surg Oral Med Oral Pathol Oral Radiol Endod
2005;99:485‐9
Toshiba Aquilion 64 MDCT and
NewTom vGi CBCT Scanner (Dental)
A Comparison of Maxillofacial CBCT and Medical CT. Christos Angelopoulos
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Basics of CBCT
• CBCT imaging is performed using a rotating platform to which an x‐ray source and detector are fixed.
• A divergent pyramidal‐ or cone‐shaped x‐ray source is directed through the middle of the RO
• Transmitted, attenuated radiation is projected onto an area x‐
ray detector on the opposite side
• The x‐ray source and detector rotate around a fulcrum, the center of the final volume imaged
• During the rotation, multiple sequential planar projection images covered by the detector or the field of view (FOV) are acquired in an arc of 180o or greater
• These single projection transmission images constitute the raw primary data and are individually referred to as basis, frame, or raw images
Basics of CBCT
• Basis images appear similar to cephalometric radiographic images • There are usually several hundred projection‐basis images that are reconstructed an image volume
• The complete series of images is referred to as the projection data or volumetric dataset
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Advantages of CBCT
• Irradiated field of view (FOV) reduced to region of interest
• Mechanical lead collimation or electronic masking
• Only collimation reduces volume of tissue irradiated
Collaborating to
Bring a Unique Solution
MDCT vs. CBCT
X-ray source 80-140 kVp
20-100 kW
80 – 120 kVp
Stationary Anode
Pulsed beam
Focal Spot
0.5 – 1.2 mm
0.5 – 1.2 mm
Detector
MD arrays
64 – 256+ rows
Flat panel
Tl:CsI, Tr:GdOS
Spatial Res 0.5 – 0.625 mm
Contrast Res ~1 HU
0.4 mm (20 cm FOV)
~10 HU
A Comparison of Maxillofacial CBCT and Medical CT. Angelopoulos et al
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DOSIMETRY
OOOOE (Palomo, et al. & Ludlow, et al.)
Principles of CBCT – Dosimetry
Conclusions: The Kodak 9000 3D
provides doses that are
substantially lower than previously
reported doses produced by
medium and large FOV CBCT units.
The digital panoramic mode provides
a low dose alternative for panoramic
examinations of the jaws using the
same unit.
Level
s
2
3
4
5
6
7
9
Ludlow JB: Dosimetry of Kodak 9000 3D Small FOV CBCT and Panoramic Unit, UNC School of Dentistry,
Chapel Hill, NC, 2008.
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Ludlow JB: Patient risk related to common dental radiographic examinations JADA 2008
Ludlow JB: Patient risk related to common dental radiographic examinations JADA 2008
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Ludlow JB: Patient risk related to common dental radiographic examinations JADA 2008
Principles of CBCT – Dosimetry
Ludlow JB: Dosimetry of Kodak 9000 3D Small FOV CBCT and Panoramic Unit, UNC School of Dentistry,
Chapel Hill, NC (2008)
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Adapt CT measurement
techniques
• Follow MDCT Methods +
• Dosimetry – Head only
• Challenges
– Image Quality phantom size
– Manufacturer provided, CATPhan,
old RMI
– AAPM Head dosimetry OK
– Use of detector entrance exposure?
– Positioning phantoms – not trivial!
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Dosimetry and Image Quality Evaluation of a Dedicated Cone‐beam CT System for Sinus and Temporal‐Bone Applications
Lifeng Yu, PhD, Thomas J. Vrieze, Michael R. Bruesewitz, James M. Kofler, PhD, Cynthia H. McCollough, PhD
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Reports
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For dental CBCT systems, measurement of
dose and image quality
20%
20%
20%
b)
c)
20%
20%
a) Can follow the methods
b)
c)
d)
e)
described in the ACR CT
accreditation program QC
Manual (2012)
Can only be performed using
TLD’s in a Rando head phantom
Require adaptation of standard
CT testing methods to the unique
challenges of CBCT systems
Are not necessary because all
new systems are self-calibrating
Can be performed by the service
engineer
a)
d)
10
e)
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For dental CBCT systems, measurement of dose and
image quality
a) Can follow the methods described in the ACR CT
accreditation program QC Manual (2012)
b) Can only be performed using TLD’s in a Rando head
phantom
c) Require adaptation of standard CT testing methods to
the unique challenges of CBCT systems
d) Are not necessary because all new systems are selfcalibrating
e) Can be performed by the service engineer
Ref. Dosimetry of two extraoral direct digital imaging devices: NewTom cone beam CT and Orthophos Plus DS panoramic unit, Ludlow, Daview‐Ludlow and Brooks. Dentopmaxillofascial Radiology (2003) 32 229‐234
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Correct for Geometry to Image Receptor
Distances, from CJ, IMTEC
FS to detector
FS to tube cover (for CTDP)
FS to axis of rotation
Patient (axis of rotation) to detector
FS to detector active depth
Full Field
Reduced Field
Horizontal
inches
31
mm
787.4
V:
Approx CTDP
40.5mm
6.347
24
161.2
609.6
H:
V2:
51mm
29mm
7
177.8
31.607
802.8
CTDP at tube half Exposed length of pencil chamber (assuming point cover (mm) length source)
40.5 20.25
76.6
29
51
14.5
25.5
54.8
Regarding assessment of beam collimation in CBCT
systems:
a) Scanning of GafChromic media images may be used,
corrected for geometry
b) CR or film based imaging systems must be used to
detect the x-ray beam
c) This is not necessary because CBCT systems collimate
automatically
d) Is not possible to be performed in the field by a medical
physicist
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Regarding assessment of beam collimation in
CBCT systems:
a) Scanning of GafChromic
25%
25%
25%
b)
c)
25%
media images may be
used, corrected for
geometry
b) CR or film based imaging
systems must be used to
detect the x-ray beam
c) This is not necessary
because CBCT systems
collimate automatically
d) Is not possible to be
performed in the field by a
medical physicist
a)
d)
10
Regarding assessment of beam collimation in CBCT
systems?
a) Scanning of GafChromic media images may be used,
corrected for geometry
b) CR or film based imaging systems must be used to
detect the x-ray beam
c) This is not necessary because CBCT systems collimate
automatically
d) Is not possible to be performed in the field by a medical
physicist
Ref: Application of Gafchromic film in the study of dosimetry methods in CT phantoms. Martin CJ, Gentle DJ, Sookpeng S, Loveland J., J Radiol Prot. 2011 Dec;31(4):389‐409
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IAC CT
Accreditation for
Dental CT
Mary Lally, MS, RTR (MR)
IAC Deputy Chief Executive Officer
Improving health care through accreditation
Improving health care through accreditation
Who is the IAC?
• Accreditation is IAC’s only business for 22 years
• Over 10,000 sites accredited
• One non profit 501(c)(6) organization with seven
divisions
– Five diagnostic imaging modalities (vascular testing, echo,
nuclear/PET, MR and CT)
– Two therapeutic (carotid stent; vein center)
• Overall organization directed by IAC board
– Composed of 2 representatives from each division
– Responsible for strategic direction and financial oversight
• Primary division responsibility – review and revise
modality specific standards
Improving health care through accreditation
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Improving health care through accreditation
IAC Sponsoring Organizations
American Academy of Dermatology (AAD)
American Academy of Neurology (AAN)
American Academy of Orthopaedic Surgeons
(AAOS)
American Academy of Otolaryngology — Head
and Neck Surgery (AAO-HNSF)
American Association of Physicists in Medicine
(AAPM)
American Academy Of Oral and Maxillofacial
Radiology (AAOMR)
American Association of Oral and
Maxillofacial Surgeons (AAOMS)
American College of Cardiology (ACC)
American College of Phlebology (ACP)
American College of Surgeons (ACS)
American College of Nuclear Medicine (ACNM)
American Institute of Ultrasound in Medicine
(AIUM)
American Society of Echocardiography (ASE)
American Society of Neuroimaging (ASN)
American Society of Neuroradiology (ASNR)
American Society of Nuclear Cardiology (ASNC)
American Society of Radiologic Technologists
(ASRT)
American Venous Forum (AVF)
Improving
health
care through
accreditation
International
Society
for Musculoskeletal
Imaging
in Rheumatology (ISEMIR)
American Association of Neurological Surgeons
Neurocritical Care Society (NCS)
Society for Cardiovascular Angiography and
Interventions (SCAI)
Society for Cardiovascular Magnetic Resonance
(SCMR)
Society for Clinical Vascular Surgery (SCVS)
Society for Vascular Medicine (SVM)
Society for Vascular Surgery (SVS)
Society for Vascular Ultrasound (SVU)
Society of Cardiovascular Computed
Tomography (SCCT)
Society of Diagnostic Medical Sonography
(SDMS)
Society of Interventional Radiology (SIR)
Society of NeuroInterventional Surgery (SNIS)
Society of Nuclear Medicine and Molecular
Imaging (SNMMI)
Society of Nuclear Medicine and Molecular
Imaging Technologist Section (SNMMITS)
Society of Pediatric Echocardiography (SOPE)
Society of Radiologists in Ultrasound (SRU)
Society of Vascular and Interventional Neurology
(SVIN)
World Molecular Imaging Society (WMIS)
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Improving health care through accreditation
Improving health care through accreditation
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Improving health care through accreditation
http://www.intersocietal.org/ct/standards/IACCTStandards2012.pdf
Improving health care through accreditation
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Dental CT Standards
• Dental staff training and experience
requirements
• Patient safety and confidentiality policies
• Equipment QC
• Radiation oversight and safety adherence
• Report content
• Quality assurance program
• Image quality review
Improving health care through accreditation
Medical Physics Responsibilities
• Reports follow Guidance Documents for
– Radiation Protection Survey (one time)
– Image Quality and Dose reports
• Phantom Images from Annual MP Survey
• Participate in Quarterly QC Committee Meetings
• 3 hour CT Radiation Safety Training
(quiz=100%) for operators who are not RT’s
• Standards definition of medical physicist
– “…board certified or in states where
licensed, registered, or otherwise state
approved”
Improving health care through accreditation
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Improving health care through accreditation
Improving health care through accreditation
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Improving health care through accreditation
Dental CT Standards
• Dental staff training and experience
requirements
• Patient safety and confidentiality policies
• Equipment QC
• Radiation oversight and safety adherence
• Report content
• Quality assurance program
• Image quality review
Improving health care through accreditation
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For IAC CT accreditation, facilities must
submit:
a) Dosimetry provided by the manufacturer
20%
20%
20%
b)
c)
20%
20%
b) TLD’s mounted to the surface of the ACR
accreditation phantom
c) Images of the ACR CT accreditation
phantom, reconstructed at the minimum
slice thickness
d) Reports and image quality assessments
performed by a medical physicist or other
individual licensed, registered, or
otherwise state approved to perform
these measurements in CT facilities
e) The standard ACR dosimetry report for
an adult abdomen
a)
d)
10
e)
For IAC CT accreditation, facilities must submit:
a) Dosimetry provided by the manufacturer
b) TLD’s mounted to the surface of the ACR accreditation
phantom
c) Images of the ACR CT accreditation phantom,
reconstructed at the minimum slice thickness
d) Reports and image quality assessments performed by a
medical physicist or other individual licensed, registered,
or otherwise state approved to perform these
measurements in CT facilities
e) The standard ACR dosimetry report for an adult abdomen
Ref: IAC CT Standards. http://www.intersocietal.org/ct/reaccreditation/ct_standards.htm
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Growth of Dental CBCT
• Initially used by specialists for implants
• Increasingly found in larger general dentistry
offices
• Current estimates about 10,000 Dental CBCT
• Growing rapidly
• American Academy of Oral and Maxillofacial
Radiologists
• American Dental Association
– Council on Dental Benefits
– Council od Dental Specialties
• Support for accreditation
Summary
• Evolution of Dental Imaging in Clinical
Practice
• Film based dental imaging
– Dose, Image Quality and Consistency
• Digital dental imaging, planar and CBCT
• Dose, Image Quality and Consistency
• Medical Physics Measurements for
Dental Systems
• Accreditation of Dental Imaging Facilities
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Conclusion
• The medical physicist can make a significant
contribution to dental imaging facilities through careful
measurements , education and consultation
32