ENDODONTOLOGY INTRODUCTION. Original Research ABSTRACT

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1 Original Research Radiovisiography and ultrasound real time imaging in the differential diagnosis of periapical lesions of endodontic origin A comparative in vivo study SHILPA H. BHANDI * SUBHASH T.S. ** ABSTRACT Background & Objective: Radiographic images are routinely used in the field of endodontics for the diagnosis, treatment planning and followup of periapical bone lesions. The possibility of making a distinction between cystic lesions and granulomas among the lesions of endodontic origin may be important in the management of periapical pathosis and in predicting endodontic treatment. Recent developments in radiovisiography (RVG) and Ultrasonography have given the dentist the ability to perform radiographic examinations with greatly reduced rates of radiation exposure. Objective of the study is to assess whether the use of real time ultrasound imaging and RVG can help in the differential diagnosis of periapical lesions of endodontic origin. ethod: Ten patients diagnosed with periapical lesions using conventional radiographic findings were subjected to radiovisiography and ultrasound imaging. The comparative evaluation of reports of radiologist and echographist was done to arrive at a tentative differential diagnosis. Interpretation and conclusion: This study has shown that there was definite correlation between the echo structure of a lesion and the nature of lesion. Cystic lesion versus granuloma. The results obtained tallied 90% of the time. Based on the results we can conclude that real time ultrasound imaging and RVG can be used in the endodontic field for the study of periapical lesions. Keywords: RVG; ultrasound; cyst; granuloma. INTRODUCTION The possibility of diagnosing a periapical lesion, accurately measuring it, describing its histopathologic features and understanding the severity of the infection may help understand its healing potential. It is also important in assessing treatment results and for epidemiological studies. ost of the times it is also difficult to properly evaluate healing of periapical lesions because the recall radiographs are taken at long intervals and are developed differently. For all these reasons new technique, for obtaining more accurate imaging and more predictable interpretation of the images of periapical lesions are constantly being sought. 1 Radiographs are an important part of root canal treatment, especially for the detection, treatment and follow up of periapical bone lesions. However, routine radiographic procedures do not demonstrate reliably the presence of every lesion and they do not show the real size of lesion and its spatial relationship with anatomical structures. 2 * Assistant Professor, ** Professor, Department of Conservative Dentistry and Endodontics, Bapuji Dental College and Hospital, Davangere. 29

2 SHILPA H. BHANDI, SUBHASH T.S. Currently, radiographs are the most accurate and least subjective diagnostic aids available to endodontics and are essential for the detection of osseous abnormalities in the maxilla and the mandible. Pathological changes in body architecture and disease progression can be followed with radiographs. However, past studies have indicated that periapical pathosis are only detectable in later stages of bone destruction. Density and gray scale changes in radiographs are important visual features the clinician uses to evaluate changes in bone pattern. With advances in technology, researchers are constantly seeking ways to enhance radiographic diagnostic accuracy. Advances in digital technology have been made in dental and medical imaging. One direct digital radiographic technique currently used in dentistry is radiovisiography (RVG, trophy radiology, Inc., arietta GA). This system is based on digital image capture with a chargedcoupled device capable of image enhancement using upto 256 shades of gray. 3 The use of computerized tomography (CT) has been shown to be of help in the management of extensive periapical lesions and it has been suggested that CT is a noninvasive method that could be used to make a differential diagnosis between a cyst and a granuloma. Unfortunately, routine use of CT is associated with high dosage of radiation even though dose reduction methods have been established. 2 Ultrasonography has revolutionized every sphere of science and technology. In medicine, it has abundant potentials to monitor physiological conditions, investigate suspected pathology and aid in the treatment of the same. These applications are further enhanced by its high end aspects of color power Doppler to assess blood flow, 3dimensional imaging and detection of tissue harmonies for improved resolution. 4 Therefore the purpose of the study is to assess whether the use of realtime ultrasound imaging (echography), together with the application of color power Doppler and radiovisiography can help in the differential diagnosis of periapical lesions of endodontic origin. ETHODOLOGY Ten patients aged between 18 and 50 years, were selected for the study. The patients had been diagnosed with periradicular lesion of endodontic origin based on clinical signs and symptoms and conventional radiography. The patients were scheduled to be treated in the department of conservative dentistry and endodontics at Bapuji Dental College and Hospital, Davangere. for endodontic treatment. Patient who agreed to take part in the study were asked to sign an informed consent form before undergoing the echographic examination. Detailed history of patient was recorded. The patient was subjected to RVG and findings were recorded. Next area of diagnostic interest in the mouth was selected for the echography. The ultrasonic sensor covered with a layer of echographic gel was placed extra orally corresponding to the apical area of the, tooth of interest. The sensor was put in contact and moved slightly in order to obtain adequate number of transversal scans to define the defect, color power Doppler was applied to each examination. 30

3 RADIOVISIOGRAPHY AND ULTRASOUND REAL TIE IAGING IN THE DIFFERENTIAL DIAGNOSIS OF PERIAPICAL LESIONS OF ENDODONTIC ORIGIN A COPARATIVE IN VIVO STUDY For each lesion, a representative echographic image was selected, and analyzed by an expert echographist together with an endodontist. A tentative differential diagnosis between a cystic lesion and granuloma was agreed based on the following principles. Cystic lesions: A transonic (hypoechoic) well contoured cavity, surrounded by reinforced bone walls, filled with fluids and with no evidence of internal vascularization on color power Doppler examination. Granuloma A poorly defined lesion, which could be frankly corpusculated (hyperechoic/echogenic) or could show both corpusculated and hypoechoic area exhibiting a rich vascular supply on color power Doppler examination. RESULTS The results of this study showed that, out of 10 cases examined, RVG and ultrasound report for 9 cases were similar except in one case it was differed. Sl. No Age Sex 19 F 19 Tooth No RVG PAG PAG US H/P DISCUSSION The latest alternative to film for intraoral radiography is Radiovisiography (RVG), a digital imaging system utilizing an intraoral sensor in place of radiographic film. 5 RVG image enhancement produces images that are significantly more diagnostic then CR within bone.rvg was more accurate in detecting periapical breakdown in earlier stages such as lamina dura perforation and medullary bone involvement. The clinical findings suggest that RVG could provide an accurate method for cooling detection of periapical pathosis with less exposure. 3 The occurrence of pathologic changes associated with periapical bone tissue is common, and radiography is still the superior tool for the detection of periapical pathosis. However, radiography is not a perfect diagnostic test. A lot of effort has been made to improve the imaging of the periapical bone in order to detect early signs, pathosis or healing. The development of digital radiography has created new options in this field. 6 Evolution of RVG: RVG was first described in 1988 and introduced commercially to the UK in 1989.Since then, it has undergone several changes, both major and minor F RVG Radiovisiography US Ultrasound H/P Histopathology PAG Periapical Granuloma Periapical Cyst PAG RVG comprises of four basic components: An Xray set with electronic time; an intraoral sensor; a display processing unit (DPU); and a printer. Features of RVG: 1) Image Enhancement A) A smoothing (lowpass) filter eliminates noise/scatter that may be present within the image; 31

4 SHILPA H. BHANDI, SUBHASH T.S. B) Edge enhancement (highpass filter) enhances the edges between adjacent regions of different greylevel values, but increases the electronic noise level (this feature can be further improved by use of the next method of enhancement); and C) Edge detection (Laplacian), which dramatically enhances the edges within image but eliminates detail from the rest of the time. 2) Radiation dose Current radiation protection regulations recommend the use of the fastest available films consistent with satisfactory diagnostic results. The specific radiation dose required is dependent on the area of the mouth to be irradiated, for example the dose required is greater in the maxillary molar region than the lower incisor region. 3) Resolution The introduction of the ZHR function increased the resolution to 11 line pairs/ mm in this mode. This measurement has been confirmed by Benz and ouyen. The authors found a resolution of 7 line pairs/ mm in standard mode. 4) Collimation In conventional intraoral radiography, the beam size is larger in area than in adultsized periapical film, because the beam is enlarged and circular while the film is rectangular. This latitude is designed to accommodate errors in the alignment. Recommendations for rectangular collimation in intraoral radiography have been made by several authors as a means of reducing patient exposure to Xrays. Incorporating rectangular collimation to the RVG sensor would therefore permit a further decrease in radiation dose. Advantages of RVG: Several features of the RVG system have potential clinical advantages: Substantial dose reduction; the production of instantaneous images; Control of contrast. Ability to enlarge specific areas, which may be of use in visualizing instrument location during endodontic treatment; and the potential for computer storage and subsequent transmissions of the images. Disadvantages of RVG: Previous disadvantages of the system included limitations caused by the relatively small sensor size and its greater thickness than conventional film. To date, only limited clinical studies have been reported regarding the RVG technique. The possibilities of the technique s unique ability of image enhancement have still to be explored to the full. As the technique is so different from the conventional, it is important for the observer to view the image produced without the constraints imposed by conventional radiography. The technique is simple to use, but assessment of images may require a certain degree of familiarization as the image is different from a conventional radiograph. 7 Realtime ultrasound imaging (echography) is widely used in medicine: it is based on the phenomenon of the reflection of ultrasound (US) waves (echoes) at the interfaces between tissues that have different acoustic properties. The application of Color Power Doppler ultrasound to the echography offers an opportunity to evaluate and determine the presence, direction and velocity of blood flow within the ultrasound image of the 32

5 RADIOVISIOGRAPHY AND ULTRASOUND REAL TIE IAGING IN THE DIFFERENTIAL DIAGNOSIS OF PERIAPICAL LESIONS OF ENDODONTIC ORIGIN A COPARATIVE IN VIVO STUDY examined tissue. Color Power Doppler gives a colorcoded representation of the Doppler signal and its time modification (Fleischer & Emerson 1993). The use of realtime ultrasound examination for the evaluation of bone lesions of endodontic origin has been assessed recently and reported. 8 US waves are generated by a quartz or synthetic ceramic crystal when it is exposed to an alternating current of 310 hz. as a result of the piezoelectric effect, the crystal distributes US waves oscillating at the same frequency. The US waves arriving in biological tissues encounter areas of different density and different mechanical and acoustic properties. At the interface between two tissues with different acoustic impedance the US waves undergo refraction and reflection. The echo is the part of the US wave reflected back toward the crystal. The echo is transformed by the crystal into electrical energy, which in turn is transformed into a light spot using a grey scale into a TV monitor. The point of origin of the echo along the line of the US wave is calculated by the computer built into the US apparatus from the time delay between the initiation of the wave signal and its return. The US image seen on the monitor is produced by automatic movement of the crystal over the tissue of interest. As each movement gives one image of this tissue (depending on its plane) and there is a frequency of 3050 images per s, they appear in a screen as moving images. oving the US probe by hand over the area of interest changes the sector plane and thus a real time threedimensional impression of the space is obtained. The interpretation of grey values on an image is based on a qualitative comparison of the echo intensity with that of normal tissue. Hypoechoic or transonic is an area with low echo intensity; anechoic is an area where no reflection occurs (i.e. any area filled with fluids), and hyperechoic is an area which has high echo intensity. Bone exhibits a phenomenon of total reflection (hyperechoic / totally echogenic), therefore US imaging can only be performed through windows in bone or where the bony architecture has been altered (Auer & Van Velthoven 1990). Areas which have different types of tissues show what is termed a dishomogeneous echo. (E. Cotti, G. Campisi IEJ 2002). 2 The results from preliminary investigations suggested that ultrasound realtime imaging was an easy and reproducible examination that could become a useful adjunct to conventional radiography in the management of extensive periapical lesions, as it provides specific information on the size of the lesion, it has few risks and the images are obtained in digital form that are easy to read, store and reproduce. From a biological standpoint, in experimental and clinical studies, no adverse effects of ultrasound waves have been shown to occur in the tissues as a consequence of echographic examination, and even if the effect of repeated echographic examinations is less certain, the risks entailed by radiography are much greater. 8 The results obtained from 10 lesions showed that there was a definite correlation between the echo structure of a lesion and the nature of lesion: cystic lesion versus granuloma. The results obtained by subjecting the lesions to ultrasound and RVG were compared, which showed that outcome of both methods tallied 90% of the time; however in one case the result was dissimilar. 33

6 SHILPA H. BHANDI, SUBHASH T.S. CONCLUSION Based on these results, real time ultrasound imaging and RadioVisioGraphy can be used in the endodontic field for the study of periapical lesions. REFERENCES 1) Cotti E, Simbola V, Dettori C, Campisi G. Echographic evaluation of bone lesions of endodontic origin: Report of two cases in the same patient. JOE 2006; 32(9): ) Cotti E, Campisi G, Garau V, Puddu G. A new technique for the study of periapical bone lesions: ultrasound real time imaging. Int Endodont J 2002; 35: ) Yokota ET, iles DA, Newton CW, Brown C. Interpretation of periapical lesions using radiovisigraphy. J Endodont 1994; 20(10): ) Rajendran N, Sundaresan B. Efficacy of ultrasound and color power Doppler as a monitoring tool in the healing of endodontic periapical lesions. JOE 2007; 33(2): ) Horner K, Shearer AC, Walker A, Wilson NHF. Radiovisiography: An initial evaluation. Br Dent J 1990; 168: ) Kullendorff B, Nilsson, almo. Diagnostic accuracy of direct digital dental radiography for the detection of periapical bone lesions. II. Effects on diagnostic accuracy after application of image processing. Oral Surg Oral ed Oral Pathol Oral Radiol Endod 1996; 82: ) Russell, Pitts NB. Radiovisiography: An update. 20 th Anniversary Issue/Dental Update. 1993: ) Cotti E, Campisi G, Ambu R, Dettori C. Ultrasound realtime imaging in the differential diagnosis of periapical lesions. Int Endodont J 2003; 36: