photoshop evaluation of leos

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Evaluation of Chronic Periapical Lesions by DigitalSubtraction Radiography by Using Adobe Photoshop CS: ATechnical ReportFabiola B. Carvalho, DDS, MSc,* Marcelo Gonalves, DDS, MSc, PhD, andMrio Tanomaru-Filho, DDS, MSc, PhD*

Abstract

The purpose of this study was to describe a newtechnique by using Adobe Photoshop CS (San Jose, CA)image-analysis software to evaluate the radiographicchanges of chronic periapical lesions after root canaltreatment by digital subtraction radiography. Thirteenupper anterior human teeth with pulp necrosis andradiographic image of chronic periapical lesion were

endodontically treated and radiographed 0, 2, 4, and 6months after root canal treatment by using a filmholder. The radiographic films were automatically de-veloped and digitized. The radiographic images taken0, 2, 4, and 6 months after root canal therapy weresubmitted to digital subtraction in pairs (0 and 2months, 2 and 4 months, and 4 and 6 months) choosingimage, calculation, subtract, and new docu-ment tools from Adobe Photoshop CS image-analysissoftware toolbar. The resulting images showed areas ofperiapical healing in all cases. According to this meth-odology, the healing or expansion of periapical lesionscan be evaluated by means of digital subtraction radi-ography by using Adobe Photoshop CS software. (JEndod 2007;33:493497)

Key Words

Digital subtraction, periapical lesion, radiograph

Chronic periapical lesions associated with root-filled teeth are usually monitored byconventional periapical radiography (1, 2). However, the suggested radiographiccriteria, including lesion persistence and increase of periapical lesion size, are quali-tative and subjective (3). Several methods have been described to measure periapicalradiolucencies, including measurement of the diameter, distance between root surfaceand radiolucency outlines, use of a specific classification, and determination of the areaby means of tracing (4).

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

Digital subtraction radiography with specific software is considered as a valuable toolfor evaluation of periapical lesions because they are capable of detecting extremely smallbonealterations.It increasestheaccuracyforassessmentofbonegainorlossduringorafterroot canal treatment (5). In addition, this technique almost duplicates the sensibility indetecting lesions in comparison to conventional radiographic interpretation (6).

The importance of digital subtraction radiography as an evaluation tool of thehealing process of periapical lesions has been shown in follow-up studies with en-dodontically treated teeth (710). The results of those studies show that image sub-traction is a good tool to be used in reliable diagnoses of minimal changes of periapicaltissues during short-time intervals. However, the technology involved in digital subtrac-

tion radiography together with the need of additional equipment (specific software likeX-PoseIt [XP, Torben Jorgensen, Lystrup, Denmark] and the EMAGO [Oral DiagnosticSystems, Amsterdam, The Netherlands]) and computer support make this techniquecomplicated for use in daily practice (5).

Nonspecific image-analysis software can represent an alternative for the digitalsubtraction radiographictechniquein theevaluation of healing or increase of periapicallesions. Adobe Photoshop CS image-analysis software allows digital subtraction of twosuperposed images (11).

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

Materials and Methods

Thirteen upper anterior human teeth with pulp necrosis, asymptomatic, in normalmasticatory function, and a radiographic image of chronic periapical lesion larger than5 mm in diameter measured in its largest long axis were selected for this study. Patientwritten informed consent was obtained after the nature of the procedures and possiblediscomforts and risks had been fully explained.

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

Radiographs were taken0, 2, 4, and6 months after root canal filling by using Rinn XCPfilm holder (Rinn Corp, Elgin, IL) stabilized with spherical rubber silicone impression

From the *Department of Restorative Dentistry, Arara-quara Dental School, So Paulo State University, UNESP,Araraquara, SP, Brazil; and Department of Radiology, Arara-quara Dental School, So Paulo State University, UNESP,Araraquara, SP, Brazil.

Address requests for reprints to Dr. Mrio Tanomaru Filho,Rua Humait, 1680, Caixa Postal 331, Centro, 14801-903

Araraquara, SP, Brazil. E-mail address: [email protected]/$0 - see front matterCopyright 2007 by the American Association of

Endodontists.doi:10.1016/j.joen.2006.12.015

Case Report/Clinical Techniques

JOE Volume 33, Number 4, April 2007 Chronic Periapical Lesions 493


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material(OptosilComfort,Heraeus Kulzer, Germany)to standardize imagegeometry (Fig. 1). All radiographs were taken by using periapical film (In-sight; Eastman Kodak Company, Rochester, NY) with GE 1000 X-ray device(General Electric, Milwaukee, WI) at 90 kVp, 10 mA, and 0.12-secondexposure time

The exposed films were automatically developed in an automaticfilm processor (Dent-X 9000; Dent-X Co, Elmsford, NY) by using 5minutesof dry-to-dry time and digitized by using a desk scanner(Snap-Scan 1236s Flatbed Scanner; Agfa-Gevaert NV, Mortsel, Belgium) using2400 dpi acquire resolution. The resulting images were stored in JPEGformat at low-compression level.

Radiographstaken0,2,4,and6monthsafterrootcanaltreatmentwere submitted to digitalsubtraction in pairs by using Adobe PhotoshopCS image-analysis software. The radiograph obtained after 2 months offollow-up was subtracted from that taken immediately after root canaltherapy. In a sequence, the radiograph obtained after 4 months offollow-up was subtracted from that taken after 2 months, and the6-month follow-up radiograph was subsequently subtracted from theprevious one. Before digital subtraction, both radiographs were movedin horizontal, vertical, or rotational directionsapplying software tools toreduce geometric distortion. To remove bright and contrast variations,both images were enhanced based on the mean of pixel intensity shown

Figure2. Selectionof a sequence of superposedradiographic images showing theSubtractand NewDocumentcommands of theCalculation tool, selected fromthe Image submenu of the main menu of Adobe Photoshop CS image-analysis software.

Figure 1. Rinn XCP device for intraoral radiographs. (a) Mounted film holder: blue for upper and lower anterior regions, yellow for upper and lower posteriorregions, and red for bitewing radiographs. (b) Mounted film holder showing radiographic film and bite block stabilized with impression material.


494 Carvalho et al. JOE Volume 33, Number 4, April 2007


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in histogram scale. Then, these images were superposed and sub-tracted. First, Image option was selected on the main menu of AdobePhotoshop CS image-analysis software. Next, in the Image submenu,the Calculation tool was selected by a left click. A toolbar box wasopened; the following commands were chosen: source 1 (later ra-diographic image), source 2 (earlier radiographic image), blend-ing (subtract) and result (new document) (Fig. 2). The imagesresulting from digital subtraction were enhanced with brightness andcontrast tools to facilitate the observation of new bone tissue areas.

Results

The observation of the radiographic images resulting from digitalsubtraction performed by using Adobe Photoshop CS image-analysissoftware showedperiapical healing areas in allstudied cases.Only threecases showed expansion of the radiolucent area between 2- and4-month controls.

Regions that presented the same pixel intensity in both radio-graphic images were shown with grayscale on the digital subtraction

Figure 3. (a) Radiographic image obtained after root canal treatment. (b) Two months of follow-up. (c) Result of the digital subtraction.




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digitized images, theywere subtracted by using thesubtract commandof the calculation tool. In the present study, the same procedure wasperformed maintaining a standardized radiographic technique becausethis software is not specific for digital subtraction and has no specifictools to correct any variation of image alignment.

Despite its limitations for this application, Adobe Photoshop CSimage-analysis software has shown a great potential for use in dentistry,more specifically in endodontics and radiology.

Conclusions

The radiographic changes of chronic periapical lesions can beevaluated by means of digital subtraction radiography by using AdobePhotoshop CS image-analysis software. The use of nonspecific softwarefor digital subtraction can represent an important tool in follow-upevaluations both in research and in clinical practice.

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



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