[Oradlist] Bone dentisty measurement with CBCT : How Reliable?

[Mohamed Elrufaei]

Dear Dr. Benn,

This seems like the practical approach,
but  I am not sure if it can produce reliable Hounsfield numbers.


Dear Dr. Farman,
I appreciate you addressing my question,

A good reference would be Dr. Carl Misch's Contemporary Implant Dentistry
[Mosby]
Dr. Carl Misch made the modification for the jaw bone density classification
to include D5
D2 bone is what implantologists prefer.
The surgical approach is different when dealing with D1,D2 bone than when
dealing with D4 bone
at least there is one implant system that has a different implant design for
almost each class of bone density (as advocated by Dr. Carl Misch)

CBCT is a great tool for measuring bone quantity, but how about quality?

Kindest regards

Mohamed

On Sun, May 17, 2009 at 7:43 PM, Benn, Douglas K. <DouglasBenn at creighton.edu
> wrote:

>  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).
> Professor
> Dept of General Dentistry
> Creighton University Dental School
> 2500 California Plaza
> Omaha
> Nebraska 68178
>
> Tel: (402)280 5025
> Fax: (402)280 5094
>
>
>
>
> -----Original Message-----
> 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?
>
> Dear Oradlisters,
>
>
>
> 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
> density**"*
>
>
>
> 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*!!
>
>
>
> Kind regards
>
>
>
> Dr. Mohamed I Elrufaei
>
> KSMC "Riyadh Dental Center"
>
> Saudi Arabia
>
> * *
>
> * *
>
> * *
>
> *CORRELATION OF CBCT GRAY SCALE VALUES WITH*
>
> *BONE DENSITIES*
>
> * *
>
> * **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
>
> known.
>
> * *
>
> *Objectives: *The purpose of this study was to determine the
>
> influence of exposure parameters on the gray-scale values of a
>
> CBCT unit.
>
> * *
>
> *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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