[Oradlist] Bone dentisty measurement with CBCT : How Reliable?
Allan G Farman
agfarm01 at louisville.edu
Sun May 17 10:12:41 PDT 2009
A statement was made that went unquestioned; namely the necessity of implant dentists to know with precision bone density. I would like to hear of article that provide strong evidence that this is indeed the case. What is the relationship between jawbone density and implant success or failure? Second, I seem to remember that not all multislice CT scanners are well calibrated for precision in determining Hounsfield units. I would be obliged if anyone could provide references concerning this issue as well. AGF
Allan G. Farman, BDS, PhD, MBA, DSc, Diplomate ABOMR
Prof. Radiology & Imaging Science
Univ. Louisville School of Dentistry: SUHD
501 South Preston Street,
Louisville, Kentucky 40292, USA
Tel: +1(502) 852.1241
>>> "Benn, Douglas K." <DouglasBenn at creighton.du> 05/17/2009 12:43 PM >>>
I have no experience with CBCT regarding density measurements. However, I wonder if a jaw shaped step-wedge placed into the occlusal region could provide a good reference? You will still have issues such as beam hardening from jaw bone but this could be allowed for when calculating density.
Dr Douglas K Benn, BDS, M.Phil., Ph.D., Dipl. Dental Radiology (Royal College of Radiologists, England).
Dept of General Dentistry
Creighton University Dental School
2500 California Plaza
Tel: (402)280 5025
Fax: (402)280 5094
From: oradlist-bounces at lists.ucla.edu on behalf of Mohamed Elrufaei
Sent: Sun 5/17/2009 9:58 AM
To: oradlist at lists.ucla.edu
Subject: [Oradlist] Bone dentisty measurement with CBCT : How Reliable?
The attached abstract was published in April's Issue of OOOE, the authors
suggest "*it may be necessary to use calibration phantoms that are scanned
simultaneously with the patient to allow for accurate determination of bone
Do you have an opinion on this issue? do you still think CBCT can produce a
reliable measurement of bone density (D1, D2, D3, D4)? A major issue at
least for implantologists
The authors note *a marked change* in grayscale values (bone density)
readings *on changing the FOV*!!
Dr. Mohamed I Elrufaei
KSMC "Riyadh Dental Center"
*CORRELATION OF CBCT GRAY SCALE VALUES WITH*
* **Haristoy RA, Valiyaparambil JV, Mallya*
*SM, Section of Oral and Maxillofacial Radiology, University*
*of Connecticut School of Dental Medicine, Farmington CT*
*Introduction: *Cone beam CT (CBCT) units allow for determination
of gray scale values of pixels within the image. However,
unlike with Hounsfield Units, there is no standard for
scaling these gray-scale values to attenuation coefficients of
tissues. Variations of the gray scales with exposure parameters
(kVp, mAs and field of view) are not known. Additionally, the
relationship between the gray values and bone densities are not
*Objectives: *The purpose of this study was to determine the
influence of exposure parameters on the gray-scale values of a
*Materials and Methods: *We fabricated a radiographic phantom
consisting of varying concentrations of dipotassium hydrogen
phosphate (K2HPO4, 50 - 1000 mg/ml). K2HPO4 solutions
are bone equivalent and, thus, were used to simulate bone densities
of trabecular and cortical bone. The phantom was imaged
on a CB Mercuray unit at various exposure parameters. Grayscale
values were determined using 2 software programs-Image
J and Osirix. Gray-scale values were normalized to the gray-scale
value of water. The influence of the various exposure parameters
to normalized, gray-scale values was determined.
*Results: *At all exposure settings examined, there was a
strong correlation between gray-scale values and bone density
over the entire range of bone densities examined (R2_0.99).
Both software programs yielded similar results-measured grayscale
values were not significantly different between the 2 programs.
However, at a given kVp-mAs setting, the normalized grayscale
values varied between the different fields of view- smaller
fields of view yielded higher gray-scale values for the same
concentration of bone-equivalent material. This variance ranged
from 10% at lower (trabecular-bone equivalent) densities to 15%
at higher (cortical bone equivalent) densities.
*Discussion: *Our results demonstrate a strong correlation
between gray-scale values on CBCT images and bone densities.
This has implications for potential quantitative radiological approaches
to determine bone density from CBCT images. However,
given the variation of the gray-scale values, despite normalization,
it may be necessary to use calibration phantoms that
are scanned simultaneously with the patient to allow for accurate
determination of bone density.
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