Diagnosis Digital

7/31/2019 Diagnosis Digital

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TECHNO BYTES

Diagnosis goes digital

David C. Hatcher, DDS, MSc, MRCD(c),a and Cameron L. Aboudara, DDS, MSb

Sacramento and Moraga, Calif

Accurate images of the craniofacial region are critical for the development of an orthodontic diagnosis and

treatment plan. The NewTom QR 9000 Volume Scanner (QR s.r.l., Verona, Italy) represents a significant

advance in imaging capabilities for dentistry and orthodontics. This new-generation scanner uses computed

tomography technology to provide a complete 3D view of the maxilla and mandible with relatively high

resolution and low radiation exposure to patients. This article discusses some technical aspects of this new

scanner and its possible orthodontic uses. (Am J Orthod Dentofacial Orthop 2004;125:512-5)

Images of the craniofacial region are an important

part of the dental patient record. Ideally, the

imaging process begins with the development of an

imaging goal, or a clinically derived question that can

be answered with imaging. Specific and detailed clini-

cal questions require specific and detailed imaging

solutions. Digital processes have improved the diagnos-

tic capabilities of the imaging tools being used in

dentistry and orthodontics.

CHARACTERISTICS OF DIGITAL IMAGES

A digital image is composed of picture elements

(pixels) that are arranged in a 2-dimensional rectangu-

lar grid, with each pixel having a specific size, color,intensity value, and location within the image (ie,

bitmapped or raster). A pixel is the smallest element of

a digitized image. Radiographic images generally use

gray color with an intensity value between 8 bits (28 or

256 shades of gray) and 12 bits (212 or 4096 shades of

gray). Image resolution refers to the degree of sharp-

ness of the image. Resolution is determined by the

number of pixels per given length of an image (pixels/

mm), the number of gray levels per pixel (bits), and the

management of the gray levels. Selected digital imag-

ing devices can produce digital volumes or 3D images.

The volume element (voxel) is the smallest element ofa 3-dimensional (3D) image. A voxel volume can be

thought of as a 3D array or stack of bitmapped images,

with each voxel having height, width, and thickness.

NEW DIGITAL IMAGING DEVICES

New trends in dentistry include digital imaging and

3D imaging of the maxillofacial regions. The ultimatereward of the technologic imaging advancements is the

digital representation of the patients anatomy as it

exists in nature (anatomic truth). Multiplanar reformat-

ting of the accurate digital 3D image data volume with

software tools can provide clinically relevant diagnostic

and spatial information. A digital imaging break-

through, the NewTom QR 9000 Volume Scanner (QR

s.r.l., Verona, Italy),1 is now available for clinical

practice.

Other medical volume scanners or computed to-

mography (CT) machines acquire image data by using

either a single narrow x-ray beam or a thin, broad,fan-shaped x-ray beam. These beams rotate around the

patient in a circular or spiral path as the patient moves

through the scanning machine or as the rotating beam

passes over the patient.2 The NewTom 900 scanner

uses a cone-shaped x-ray beam that is large enough to

encompass the region of interest. This type of beam

uses the x-ray emissions very efficiently, thus reducing

the absorbed dose to the patient. This type of beam also

allows for the acquisition of the image data in 1

revolution of the x-ray source and detector without the

need for patient movement. These attributes make this

system more efficient and mechanically simpler thanothers, and thus it can be designed for specific pur-

poses, such as imaging the maxillofacial region.

The NewTom QR 9000 volume imaging technique

uses the principle of tomosynthesis or cone-beamed CT

because of the shape of the x-ray beam. It received US

Food and Drug Administration approval in April 2001.

The NewTom QR 9000 has been designed specifically

to image the maxillofacial region (Fig 1). In a single

scan, the x-ray source and a reciprocating x-ray sensor

rotate around the patients head and acquire 360 pic-

tures (1 image per degree of rotation) in 17 seconds of

aDiagnostic Digital Imaging, Sacramento, Calif.bPrivate practice, Moraga, Calif.

Reprint requests to: Dr David C. Hatcher, Diagnostic Digital Imaging, 1 Scripps

Dr, Suite 101, Sacramento, CA 95825; e-mail, [email protected].

Submitted, September 2003; revised and accepted, December 2003.

0889-5406/$30.00

Copyright 2004 by the American Association of Orthodontists.

doi:10.1016/j.ajodo.2003.12.009

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accumulated exposure time. The entire maxillofacial

volume (13-cm-diameter field of view) is imaged, and

the patient receives an absorbed dose similar to a

periapical survey of the dentition. The 360 acquired

images undergo a primary reconstruction to mathemat-

ically replicate the patients anatomy into a single 3D

volume that comprises voxels similar to those of a

Rubiks cube. Each voxel is small (0.29 mm for each of

the cube faces), thus the image has a relatively high

resolution. The NewTom software allows for reformat-

ting and viewing the image data from any point of view

in straight or curbed planes and in 3 dimensions (Figs

2-4). With these software tools, the anatomy can be

peeled away layer by layer to locate the desired section.

The NewTom 9000 scanner ranks extremely high when

the balance between high diagnostic yield, low cost,and low risk is considered.

The image data can be organized into a mounting

template and viewed on the computer screen, copied

to a floppy or a compact digital disk (CD), or printed in

diagnostic-quality glossy paper or transparency for-

mats. This is similar to the way that digital extraoral

and intraoral photographs are mounted. In addition, the

entire data volume can be exported to a CD in DICOM

format and transferred to any computer to be recon-

structed and viewed as shown in Figs 2-4 with software

tools that are available to the dental community.

ORTHODONTIC USES

The NewTom 9000 Volume scan has been ex-

tremely valuable for investigating impacted teeth, tem-

poromandibular joints, implant planning, and pathol-ogy. Figures 2 through 4 give excellent examples of

how the various reconstructions provide detailed infor-

mation on the location of an impacted canine, thus

facilitating treatment decisions regarding adjacent root

resorption, surgical exposure planning, and mechanics

design.

With traditional orthodontic imaging techniques,

some areas of anatomy are poorly visualized. Three-

dimensional scans can give valuable information about

other areas of the dentition, such as the position of the

maxillary incisor roots relative to the lingual cortical

border of the palate to plan retraction, the amount ofbone in the posterior maxilla available for distalization,

the amount of bone lateral to the maxillary buccal

segments available for dental rather than skeletal ex-

pansion, airway information on the pharynx and nasal

passages, maxillary root proximity to the maxillary

sinus, the 3D extent of an atrophied alveolar ridge, and

the position of the mandibular incisor roots in bone.

These scans also allow 3D visualization of bony defects

and supernumerary teeth in patients with cleft lips or

palates. Additionally, axially corrected tomograms of

the temporomandibular joints can be obtained from the

same scan. The ability to visualize an axially correctedview of the temporomandibular joints with the teeth in

occlusion on the same reconstructed section is a signif-

icant advantage of the volume scan. Therefore, there

are substantial value added imaging benefits to these

scans for complicated orthodontic patients.

At this time, the NewTom 9000 volume scans

occasionally needs to be supplemented with panoramic

or periapical projections. According to its manufac-

turer, lateral views, including the cranial base, will be

reconstructed and exported with the updated larger

vertical sensor due to be released soon. Linear mea-

Fig 1. A, Patient just before entering scanner. B, Adjacent workstation. Courtesy of Diagnostic

Digital Imaging, Sacramento, Calif (www.ddicentral.com).

Fig 2. Reformatted image in curve plane with buccolin-

gual thickness of 10 mm.

American Journal of Orthodontics and Dentofacial Orthopedics

Volume 125, Number 4

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Fig 3. Image collage shows multiplanar reformation of NewTom 9000 volume data of facial anatomy

and impacted tooth. Top row, left to right: maxillary anatomy in axial plane; anatomy in curved plane

similar to panoramic projection. Middle row, left to right: sagittal sections of head near midline;

coupling of anterior teeth, hard and soft palate, tongue, and pharyngeal air space. Bottom row, left

to right: coronal section through molars, maxillary sinuses, nasal fossa, and mandible; axially

corrected view of right temporomandibular joint while teeth are in occlusion.

Fig 4. Image collage showing impacted tooth 6 in axial plane (upper right and middle left sections)

and in 3 dimensions. This type of visualization can be used to determine location of impacted tooth

relative to roots of adjacent teeth.


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surement tools are available in the current software.

Software tools to facilitate accurate landmark identifi-

cation for quantitative measurements and software to

facilitate segmentation of regions of interest in individ-

ual slice sections for volumetric measures are currentlyin development.

CONCLUSIONS

Computer-assisted imaging is now allowing the

dental profession to better visualize and study cranio-

facial anatomy. New imaging tools like the NewTom

9000 allow for accurate 3D replication and display of

the patient in the form of voxel volumes. Interactive

software tools allow the clinician to peel away the

tissue layers and see the hidden anatomy, which can be

invaluable in orthodontic diagnosis and treatment plan-

ning.

REFERENCES

1. Mozzo P, Procacci C, Tacconi A, Martini PT, Andreis IA. A new

volumetric CT machine for dental imaging based on the cone-

beam technique: preliminary results. Eur Radiol 1998;8:1558-64.

2. Carlsson C. Imaging modalities in x-ray computerized tomogra-

phy and in selected volume tomography. Phys Med Biol 1999;44:

R23-56.


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