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valuation of Chronic Periapical Lesions by Digitalubtraction Radiography by Using Adobe Photoshop CS: Aechnical Report

abiola B. Carvalho, DDS, MSc,* Marcelo Gonçalves, DDS, MSc, PhD,† andário Tanomaru-Filho, DDS, MSc, PhD*

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bstracthe purpose of this study was to describe a newechnique by using Adobe Photoshop CS (San Jose, CA)mage-analysis software to evaluate the radiographichanges of chronic periapical lesions after root canalreatment by digital subtraction radiography. Thirteenpper anterior human teeth with pulp necrosis andadiographic image of chronic periapical lesion werendodontically treated and radiographed 0, 2, 4, and 6onths after root canal treatment by using a filmolder. The radiographic films were automatically de-eloped and digitized. The radiographic images taken, 2, 4, and 6 months after root canal therapy wereubmitted to digital subtraction in pairs (0 and 2onths, 2 and 4 months, and 4 and 6 months) choosingimage,” “calculation,” “subtract,” and “new docu-ent” tools from Adobe Photoshop CS image-analysis

oftware toolbar. The resulting images showed areas oferiapical healing in all cases. According to this meth-dology, the healing or expansion of periapical lesionsan be evaluated by means of digital subtraction radi-graphy by using Adobe Photoshop CS software. (Jndod 2007;33:493–497)

ey Wordsigital subtraction, periapical lesion, radiograph

From the *Department of Restorative Dentistry, Arara-uara Dental School, São Paulo State University, UNESP,raraquara, SP, Brazil; and †Department of Radiology, Arara-uara Dental School, São Paulo State University, UNESP,raraquara, SP, Brazil.

Address requests for reprints to Dr. Mário Tanomaru Filho,ua Humaitá, 1680, Caixa Postal 331, Centro, 14801-903raraquara, SP, Brazil. E-mail address: [email protected]/$0 - see front matter

Copyright © 2007 by the American Association ofndodontists.oi:10.1016/j.joen.2006.12.015

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OE — Volume 33, Number 4, April 2007

hronic periapical lesions associated with root-filled teeth are usually monitored byconventional periapical radiography (1, 2). However, the suggested radiographic

riteria, including lesion persistence and increase of periapical lesion size, are quali-ative and subjective (3). Several methods have been described to measure periapicaladiolucencies, including measurement of the diameter, distance between root surfacend radiolucency outlines, use of a specific classification, and determination of the areay means of tracing (4).

Digital radiographic techniques and computed analysis methods allow measuringf the periapical lesion area and provide a correlation among the images obtained atifferent follow-up periods (3).

Digital subtraction radiography with specific software is considered as a valuable toolor evaluation of periapical lesions because they are capable of detecting extremely smallone alterations. It increases the accuracy for assessment of bone gain or loss during or afteroot canal treatment (5). In addition, this technique almost duplicates the sensibility inetecting lesions in comparison to conventional radiographic interpretation (6).

The importance of digital subtraction radiography as an evaluation tool of theealing process of periapical lesions has been shown in follow-up studies with en-odontically treated teeth (7–10). The results of those studies show that image sub-raction is a good tool to be used in reliable diagnoses of minimal changes of periapicalissues during short-time intervals. However, the technology involved in digital subtrac-ion radiography together with the need of additional equipment (specific software like-PoseIt [XP, Torben Jorgensen, Lystrup, Denmark] and the EMAGO [Oral Diagnosticystems, Amsterdam, The Netherlands]) and computer support make this techniqueomplicated for use in daily practice (5).

Nonspecific image-analysis software can represent an alternative for the digitalubtraction radiographic technique in the evaluation of healing or increase of periapicalesions. Adobe Photoshop CS image-analysis software allows digital subtraction of twouperposed images (11).

The aim of this study was to describe a new technique performed by using Adobehotoshop CS image-analysis software to evaluate the radiographic changes of chroniceriapical lesions after root canal treatment by digital subtraction radiography.

Materials and MethodsThirteen upper anterior human teeth with pulp necrosis, asymptomatic, in normal

asticatory function, and a radiographic image of chronic periapical lesion larger thanmm in diameter measured in its largest long axis were selected for this study. Patientritten informed consent was obtained after the nature of the procedures and possibleiscomforts and risks had been fully explained.

In each specific case, the root canal was prepared according to the crown-downechnique by using manual instrumentation and irrigation with 2.5% sodium hypochlo-ite. After biomechanical preparation, a calcium hydroxide-based paste (Calen PMCC;S White, Rio de Janeiro, Brazil) was placed as root canal dressing for at least 15 days.inal obturation was done by lateral condensation of gutta-percha points and Sealapexoot canal sealer (SybronEndo/SDS, Glendora, CA).

Radiographs were taken 0, 2, 4, and 6 months after root canal filling by using Rinn XCP
ilm holder (Rinn Corp, Elgin, IL) stabilized with spherical rubber silicone impression
Chronic Periapical Lesions 493

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aterial (Optosil Comfort, Heraeus Kulzer, Germany) to standardize imageeometry (Fig. 1). All radiographs were taken by using periapical film (In-ight; Eastman Kodak Company, Rochester, NY) with GE 1000 X-ray deviceGeneral Electric, Milwaukee, WI) at 90 kVp, 10 mA, and 0.12-secondxposure time

The exposed films were automatically developed in an automaticilm processor (Dent-X 9000; Dent-X Co, Elmsford, NY) by using 5

inutes of dry-to-dry time and digitized by using a desk scanner (Snap-can 1236s Flatbed Scanner; Agfa-Gevaert NV, Mortsel, Belgium) using400 dpi acquire resolution. The resulting images were stored in JPEGormat at low-compression level.

igure 2. Selection of a sequence of superposed radiographic images showing th

igure 1. Rinn XCP device for intraoral radiographs. (a) Mounted film holderegions, and red for bitewing radiographs. (b) Mounted film holder showing r

he “Image” submenu of the main menu of Adobe Photoshop CS image-analysis softw

94 Carvalho et al.

Radiographs taken 0, 2, 4, and 6 months after root canal treatmentere submitted to digital subtraction in pairs by using Adobe PhotoshopS image-analysis software. The radiograph obtained after 2 months of

ollow-up was subtracted from that taken immediately after root canalherapy. In a sequence, the radiograph obtained after 4 months ofollow-up was subtracted from that taken after 2 months, and the-month follow-up radiograph was subsequently subtracted from therevious one. Before digital subtraction, both radiographs were moved

n horizontal, vertical, or rotational directions applying software tools toeduce geometric distortion. To remove bright and contrast variations,oth images were enhanced based on the mean of pixel intensity shown

tract” and “New Document” commands of the “Calculation” tool, selected from

for upper and lower anterior regions, yellow for upper and lower posterioraphic film and bite block stabilized with impression material.

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JOE — Volume 33, Number 4, April 2007

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n histogram scale. Then, these images were superposed and sub-racted. First, “Image” option was selected on the main menu of Adobehotoshop CS image-analysis software. Next, in the “Image” submenu,he “Calculation” tool was selected by a left click. A toolbar box waspened; the following commands were chosen: “source 1” (later ra-iographic image), “source 2” (earlier radiographic image), “blend-ng” (subtract) and “result” (new document) (Fig. 2). The imagesesulting from digital subtraction were enhanced with brightness and

igure 3. (a) Radiographic image obtained after root canal treatment. (b) Tw

ontrast tools to facilitate the observation of new bone tissue areas. g


ResultsThe observation of the radiographic images resulting from digital

ubtraction performed by using Adobe Photoshop CS image-analysisoftware showed periapical healing areas in all studied cases. Only threeases showed expansion of the radiolucent area between 2- and-month controls.

Regions that presented the same pixel intensity in both radio-

ths of follow-up. (c) Result of the digital subtraction.

raphic images were shown with grayscale on the digital subtraction


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mage. Regions that represent areas of new bone tissue exhibited aadiopaque appearance, whereas regions with bone tissue resorptionere radiolucent (Figs. 3–5). A smooth anatomic image in black back-round was observed on digital subtraction images.

DiscussionDigital subtraction radiography has been shown to improve the

etection of periapical lesions compared with conventional radio-raphs (6), and its diagnostic accuracy has been shown (12, 13).

In vitro studies have shown that digital subtraction can increase theetection of periapical bone lesions, particularly those confined to can-ellous bone (12–14). Razmus (15) reported better findings in initialiagnosis of caries and detection of bone changes in cases of periodon-al disease and periapical lesions by using digital methods and radio-raphic subtraction. The results of the present study also showed thatigital subtraction was a reliable method to detect the healing of peri-pical lesions after root canal treatment, showing periapical bonehanges in small time intervals emphasizing the initial period of 2onths after completion of root canal therapy.

The success of digital subtraction radiography depends directly on

igure 4. (a) Two months of follow-up. (b) Four months of follow-up. (c) Re

he reproducibility of the radiographic image, which is associated to g

96 Carvalho et al.

ontrast, brightness, and geometric distortion. Density standardizationan be obtained by careful repetition of technical incidence factors bysing the same brand of radiographic film and maintaining a strictontrol of technical conditions (7, 16). In this study, all radiographsere taken with the same X-ray equipment and using F-speed films that

educe the exposure time by 20% when the films are automaticallyrocessed with no detriment to diagnostic efficacy (17). However,adel et al. (18) used digitized F-speed films and showed lower accu-acy than digital systems in endodontic measurement.

According to Van der Stelt (19) and Mikrogeorgis et al. (10), these of the parallel technique for radiographic acquisition is recom-ended in order to obtain images with good quality and a high degree

f reproducibility. Duckworth et al. (20) and Yoshioka et al. (9) used ailm holder associated with a custom-made bite block to provide geo-

etric standardization of the radiographs used in digital subtraction.he present study used the Rinn XCP film holding device stabilized withspherical rubber silicone impression material.

Adobe Photoshop CS image-analysis software is an excellent pro-ram for image editing that has different tools and produces good re-ults in digital image manipulation (21). In the finding related by Sar-

the digital subtraction.

ent et al. (11), after conversion into grayscale and alignment of the

JOE — Volume 33, Number 4, April 2007

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igitized images, they were subtracted by using the “subtract” commandf the “calculation” tool. In the present study, the same procedure waserformed maintaining a standardized radiographic technique becausehis software is not specific for digital subtraction and has no specificools to correct any variation of image alignment.

Despite its limitations for this application, Adobe Photoshop CSmage-analysis software has shown a great potential for use in dentistry,

igure 5. (a) Two months of follow-up. (b) Four months of follow-up. (c)esult of the digital subtraction showing an area of radiolucency.

ore specifically in endodontics and radiology.


ConclusionsThe radiographic changes of chronic periapical lesions can be

valuated by means of digital subtraction radiography by using Adobehotoshop CS image-analysis software. The use of nonspecific software

or digital subtraction can represent an important tool in follow-upvaluations both in research and in clinical practice.

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