Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X

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Dr Bhanu K Bhakhri

"The Journal of Clinical and Diagnostic Research (JCDR) has been in operation since almost a decade. It has contributed a huge number of peer reviewed articles, across a spectrum of medical disciplines, to the medical literature.
Its wide based indexing and open access publications attracts many authors as well as readers
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Dr Bhanu K Bhakhri
Faculty, Pediatric Medicine
Super Speciality Paediatric Hospital and Post Graduate Teaching Institute, Noida
On Sep 2018




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Believers Church Medical College,
Thiruvalla, Kerala
On Sep 2018




Prof. Somashekhar Nimbalkar

"Over the last few years, we have published our research regularly in Journal of Clinical and Diagnostic Research. Having published in more than 20 high impact journals over the last five years including several high impact ones and reviewing articles for even more journals across my fields of interest, we value our published work in JCDR for their high standards in publishing scientific articles. The ease of submission, the rapid reviews in under a month, the high quality of their reviewers and keen attention to the final process of proofs and publication, ensure that there are no mistakes in the final article. We have been asked clarifications on several occasions and have been happy to provide them and it exemplifies the commitment to quality of the team at JCDR."



Prof. Somashekhar Nimbalkar
Head, Department of Pediatrics, Pramukhswami Medical College, Karamsad
Chairman, Research Group, Charutar Arogya Mandal, Karamsad
National Joint Coordinator - Advanced IAP NNF NRP Program
Ex-Member, Governing Body, National Neonatology Forum, New Delhi
Ex-President - National Neonatology Forum Gujarat State Chapter
Department of Pediatrics, Pramukhswami Medical College, Karamsad, Anand, Gujarat.
On Sep 2018




Dr. Kalyani R

"Journal of Clinical and Diagnostic Research is at present a well-known Indian originated scientific journal which started with a humble beginning. I have been associated with this journal since many years. I appreciate the Editor, Dr. Hemant Jain, for his constant effort in bringing up this journal to the present status right from the scratch. The journal is multidisciplinary. It encourages in publishing the scientific articles from postgraduates and also the beginners who start their career. At the same time the journal also caters for the high quality articles from specialty and super-specialty researchers. Hence it provides a platform for the scientist and researchers to publish. The other aspect of it is, the readers get the information regarding the most recent developments in science which can be used for teaching, research, treating patients and to some extent take preventive measures against certain diseases. The journal is contributing immensely to the society at national and international level."



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Professor and Head
Department of Pathology
Sri Devaraj Urs Medical College
Sri Devaraj Urs Academy of Higher Education and Research , Kolar, Karnataka
On Sep 2018




Dr. Saumya Navit

"As a peer-reviewed journal, the Journal of Clinical and Diagnostic Research provides an opportunity to researchers, scientists and budding professionals to explore the developments in the field of medicine and dentistry and their varied specialities, thus extending our view on biological diversities of living species in relation to medicine.
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As an experienced dentist and an academician, I proudly recommend this journal to the dental fraternity as a good quality open access platform for rapid communication of their cutting-edge research progress and discovery.
I wish JCDR a great success and I hope that journal will soar higher with the passing time."



Dr Saumya Navit
Professor and Head
Department of Pediatric Dentistry
Saraswati Dental College
Lucknow
On Sep 2018




Dr. Arunava Biswas

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Dr. Arunava Biswas
MD, DM (Clinical Pharmacology)
Assistant Professor
Department of Pharmacology
Calcutta National Medical College & Hospital , Kolkata




Dr. C.S. Ramesh Babu
" Journal of Clinical and Diagnostic Research (JCDR) is a multi-specialty medical and dental journal publishing high quality research articles in almost all branches of medicine. The quality of printing of figures and tables is excellent and comparable to any International journal. An added advantage is nominal publication charges and monthly issue of the journal and more chances of an article being accepted for publication. Moreover being a multi-specialty journal an article concerning a particular specialty has a wider reach of readers of other related specialties also. As an author and reviewer for several years I find this Journal most suitable and highly recommend this Journal."
Best regards,
C.S. Ramesh Babu,
Associate Professor of Anatomy,
Muzaffarnagar Medical College,
Muzaffarnagar.
On Aug 2018




Dr. Arundhathi. S
"Journal of Clinical and Diagnostic Research (JCDR) is a reputed peer reviewed journal and is constantly involved in publishing high quality research articles related to medicine. Its been a great pleasure to be associated with this esteemed journal as a reviewer and as an author for a couple of years. The editorial board consists of many dedicated and reputed experts as its members and they are doing an appreciable work in guiding budding researchers. JCDR is doing a commendable job in scientific research by promoting excellent quality research & review articles and case reports & series. The reviewers provide appropriate suggestions that improve the quality of articles. I strongly recommend my fraternity to encourage JCDR by contributing their valuable research work in this widely accepted, user friendly journal. I hope my collaboration with JCDR will continue for a long time".



Dr. Arundhathi. S
MBBS, MD (Pathology),
Sanjay Gandhi institute of trauma and orthopedics,
Bengaluru.
On Aug 2018




Dr. Mamta Gupta,
"It gives me great pleasure to be associated with JCDR, since last 2-3 years. Since then I have authored, co-authored and reviewed about 25 articles in JCDR. I thank JCDR for giving me an opportunity to improve my own skills as an author and a reviewer.
It 's a multispecialty journal, publishing high quality articles. It gives a platform to the authors to publish their research work which can be available for everyone across the globe to read. The best thing about JCDR is that the full articles of all medical specialties are available as pdf/html for reading free of cost or without institutional subscription, which is not there for other journals. For those who have problem in writing manuscript or do statistical work, JCDR comes for their rescue.
The journal has a monthly publication and the articles are published quite fast. In time compared to other journals. The on-line first publication is also a great advantage and facility to review one's own articles before going to print. The response to any query and permission if required, is quite fast; this is quite commendable. I have a very good experience about seeking quick permission for quoting a photograph (Fig.) from a JCDR article for my chapter authored in an E book. I never thought it would be so easy. No hassles.
Reviewing articles is no less a pain staking process and requires in depth perception, knowledge about the topic for review. It requires time and concentration, yet I enjoy doing it. The JCDR website especially for the reviewers is quite user friendly. My suggestions for improving the journal is, more strict review process, so that only high quality articles are published. I find a a good number of articles in Obst. Gynae, hence, a new journal for this specialty titled JCDR-OG can be started. May be a bimonthly or quarterly publication to begin with. Only selected articles should find a place in it.
An yearly reward for the best article authored can also incentivize the authors. Though the process of finding the best article will be not be very easy. I do not know how reviewing process can be improved. If an article is being reviewed by two reviewers, then opinion of one can be communicated to the other or the final opinion of the editor can be communicated to the reviewer if requested for. This will help one’s reviewing skills.
My best wishes to Dr. Hemant Jain and all the editorial staff of JCDR for their untiring efforts to bring out this journal. I strongly recommend medical fraternity to publish their valuable research work in this esteemed journal, JCDR".



Dr. Mamta Gupta
Consultant
(Ex HOD Obs &Gynae, Hindu Rao Hospital and associated NDMC Medical College, Delhi)
Aug 2018




Dr. Rajendra Kumar Ghritlaharey

"I wish to thank Dr. Hemant Jain, Editor-in-Chief Journal of Clinical and Diagnostic Research (JCDR), for asking me to write up few words.
Writing is the representation of language in a textual medium i e; into the words and sentences on paper. Quality medical manuscript writing in particular, demands not only a high-quality research, but also requires accurate and concise communication of findings and conclusions, with adherence to particular journal guidelines. In medical field whether working in teaching, private, or in corporate institution, everyone wants to excel in his / her own field and get recognised by making manuscripts publication.


Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."



Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011




Dr. Shankar P.R.

"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."



Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011

Important Notice

Dentistry
Year : 2011 | Month : April | Volume : 5 | Issue : 2 | Page : 410 - 413

Digital Imaging

SUJATA M BYAHATTI

Dept of Oral medicine and Radiology, Maratha Mandals N.G.Halgekar institute of dental sciences and reaserch centre,Belgaum,India

Correspondence Address :
Dr. Sujata M Byahatti, Plot no 49, sector # 9, Malmaruti Extn, Belgaum-
590016
E-mail address: sujatabyahatti@rediffmail.com
Phone: 9731589981, 08312456931

Abstract

With the rapid developments in the field of computers and technology, newer methods of image acquisition and processing are available, which have been made very easy to perform. These systems utilize electronic media to record the image and advanced computer software to process the acquired image and also to modify it according to our needs. In digital imaging, the tonal value of each pixel is represented in a binary code. The binary digits for each pixel are called “bits,” which are read by the computer to determine the analog display of the image. The number of pixels-per-inch (ppi) is a good indicator of the resolution, which is the ability to distinguish the spatial detail of the digital image. The bit-depth and the pixel measurement of the pictures relate to the colours which are viewable in the image, and determine the size of the image file on a computer. Images with only two pixel shades – black and white – are binary. Grayxxscale images are typically displayed in an 8-bit mode, which is 256 shades of gray.

The aim of this article is to enlighten this latest imaging technology with its advantages and disadvantages and its multiple applications in dentistry

Keywords

Direct digital imaging, photostimulable phosphor radiography, charged couple device

How to cite this article :

SUJATA M BYAHATTI. DIGITAL IMAGING. Journal of Clinical and Diagnostic Research [serial online] 2011 April [cited: 2018 Nov 18 ]; 5:410-413. Available from
http://www.jcdr.net/back_issues.asp?issn=0973-709x&year=2011&month=April&volume=5&issue=2&page=410-413&id=1252

The advent of digital imaging has revolutionized radiology. The term ‘digital radiography’ refers to the method of capturing a radiographical image by using a sensor, breaking it into electronic pieces and presenting and storing the image by using a computer. This system is not limited to intraoral images; panoramic and cephalometric images may also be obtained (1). With the rapid development in the field of computers and technology, newer methods of image acquisition and processing are available. These systems utilize electronic media to record the image and advanced computer software to process the acquired image and also to modify it according to our needs (2). The diagnostic efficacy of intraoral radiography (3) with its limitations of clinical use, are often poorly understood or simply ignored. The aim of this article is to review the digital techniques with their advantages and disadvantages over the conventional imaging modality with reference to oral radiology

Discussion

Continuing research efforts are required to address the technical and diagnostic performance of new technologies with respect to specific clinical needs. Because detector technology only addresses one aspect of the diagnostic imaging chain, solutions might not be found merely on the basis of developments at this level. Studies are needed, that can help to improve our understanding of the complex relationships among x-ray attenuation, detector characteristics, and observer performance, and their effect on diagnostic performance and clinical outcomes. Although the currently available digital sensors are by no means ideal detectors, the increased spatial resolution and improved contrast characteristics of these sensors may already represent a level of receptor performance. The loss of oral hard tissues is a well-known public health problem for which better diagnostic methods are needed. X-ray films are poorly suited for absorptiometric measurements because their response is nonlinear and not very reproducible (4).

A study by White S C (5) (1992) says that continuing efforts toreduce the patients’ dose are desirable; however, it has been demonstrated that the dose and the associated risks for patients who are subjected to intraoral radiography are very small (5). This is especially true when an E-speed film and a rectangular collimation are used; moreover, the use of ionizing radiation for diagnostic purposes is based on cost-benefit considerations. As a result, the benefit of dose reduction should be considered in the context of physical characteristics and clinical diagnostic performance. A large number of studies have addressed the physical characteristics of intraoral films and digital systems (6)(7)(8)(9)(10). An even greater number of investigators have studied the performance of emerging digital systems for various diagnostic tasks (11)(12)(13)(14).

The rate at which new technologies are entering the marketplace and the limited amount of knowledge regarding the relationship between the physical characteristics and clinical outcomes, sustain a high demand for diagnostic efficacy testing. This would facilitate the clinical extension of scientific outcomes and the provision of data to drive the development of new technologies on the basis of diagnostic needs (15).

Diagnostic accuracy with intraoral radiography still leaves much to be desired, and detector technology only addresses one aspect of the diagnostic imaging chain. Further advancement requires a better understanding of the various components of the diagnostic imaging chain and their interactions with each other.

Various advantages of the digital systems are as follows. Chemical processing of the film is not required, the acquired images can be modified to obtain the desirable density and contrast and the exposure lattitude is higher in digital imaging as compared to films. Images can be obtained without the loss of their quality and can be retrieved as and when required. They can also be transmitted via electronic media (2). The other advantages are; superior grey scale resolution (1), easy reproducibility, reduced exposure to ra-diation, increased speed of image viewing, lower equipment and film cost, increased efficiency, the enhancement of the diagnostic images and its strong efficiency as a patient education tool.

The various disadvantages (2) of the technique which were noted, are as follows. The expenditure involved in initially setting up a digital imaging system is quite high, the image receptors are vulnerable to the effects of rough handling, once damaged, they are expensive to replace and the image receptors are bulky and rigid and tolerate the rigid sensor in the mouth as compared to the film. The resolution of the images which are acquired with a digital system is inferior to the conventional film based images. At a time, not more than two to three teeth can be studied with digital image receptors. As for infection control (1), the sensor has to be covered adequately in a disposable plastic wrapper. There can also be legal issues, because the original digital image can be manipulated.

Three methods to obtain a digital image
1. Direct digital imaging (DDI):Here, a sensor (1) is placed in the patient’s mouth and is exposed to radiation. The sensor captures the radiographical image and then transmits the image to a computer monitor, and within seconds, the image appears on the computer screen. The recent introduction of direct digital radiographical devices for oral use is a potential breakthrough for oral hard tissue measurement. Like films, photostimulable phosphor radiography (PPR) systems have good imaging characteristics and acceptable resolution (16). Unlike films, the phosphor plates have a reproducible, linear response over many orders of magnitude (17)(18)(19) and are therefore well suited for quantitative measurement.
2. Indirect digital image:In this method, an existing x-ray film is digitized by using a CCD camera (1) which scans the image and the digitizer or converts the image and then displays it on the computer monitor.
3. Storage phosphor imaging:This is a wireless digital radiography system (1). A reusable imaging plate which is coated with phosphor is used. These plates are flexible and fit into the mouth. The storage phosphor imaging records diagnostic data on the plates following the exposure to the x-ray source and uses a high speed scanner to convert the information to electronic files which can be displayed to electronic files, which can be displayed on the computer screen.

Analog versus Digital
A digital image (1) consists of a number of collections of individual pixels which are organized in a matrix of rows and columns. Each pixel has a row and a column coordinate that uniquely identifies its location in the matrix. The electrons that make up the electronic detector can be visualized as being divided into an arrangement of blocks or picture elements known as ‘pixels’. A pixel is a small box or “well” into which the electrons produced by the x-ray exposure are deposited. A pixel is the digital equivalent of a silver crystal which is used in conventional radiography. As opposed to the film emulsion that contains a random arrangement of silver crystals, a pixel is structured in an ordered arrangement. The X-ray photons that come into contact with the electronic device, cause electrons to be released from the silicon and produce a corresponding electronic charge. Consequently, each pixel arrangement or electron potential well contains an electronic charge which is proportional to the number of electrons that react within the well. Furthermore, each electronic well corresponds to a specific area on the linked computer screen. When x-rays activate the electrons and produce such electronic charges, an electronic latent image is then transmitted and stored in the computer, which can be converted into a visible image on screen or can be printed on paper. The formation of a digital image requires several steps, beginning with the analog processes. At each pixel of an electronic detector, the absorption of x-rays generates a small voltage. At each pixel, the voltage can fluctuate between a minimum and maximum value and is therefore called as an Analog signal.

The production of a digital image requires a process called ‘analog to digital conversion’ (ADC). This consists of 2 steps Sampling: That is a small range of voltage values which are grouped together as a single value Quantization: In which every sampled signal, is assigned a value. The values are stored in the computer and represent the image. This is done by the computer by organizing the pixels in their proper locations and giving them shades of gray that corresponds to the number that was assigned during the quantization step (1).

The different types of sensors or digital detectors:
1. Charged couple device (CCD):This is a solid state detector (1) that contains a thin wafer of silicon chip with an electronic circuit embedded in it. The silicon chip is sensitive to x-rays or light. The silicon matrix and its associated readout and amplifying electronics are enclosed with a plastic housing to protect them from the oral environment.
2. Complementary metal oxide semiconductors (CMOS):These are silicon based semiconductors (1) where the pixel is isolated from its neighboring pixels and is directly connected to the transistor. This technology is believed to give 25% more resolution and the chip is less expensive and offers greater durability than the CCD.
3. Charge injection device (CID):This is another sensor technology. Structurally, it is very much like the CCD, but in this case, no computer is required to process the images.
4. Photostimulable phosphor plates (PSP):These absorb and store energy from x-rays and then release this energy as light when stimulated by other lights of radiographic imaging is Europium doped, barium fluorohalide.
5. Flat panel Detectors (FPD):These provide a relatively large matrix area with pixel sizes less than 100 microns. This allows the direct digital imaging of larger areas of the body, including the head.
The digital image display can be done by two ways:
1. Cathode ray tubes which are used in conventional computer monitors. 2. Thin Film Transistor (TFT) is used in laptops and in flat panel computer displays (1).

Digital Substraction radiography
This is used for the diagnosis of subtle changes in the bone (1). Eg; it can be used to assess the bone levels before and after periodontal therapy, for the study of the periapical region and to study the superior surface of the condyle. The basic advantages include an improved overall contrast the structures are more closely visualized in the processed image, the trabecular fine marrow spaces are excellently visualized and low density as well as high density structures are equally enhanced and better visualized. The diagnostic problem in a radiographical examination lies primarily in the identification of the image features which are caused by a pathological process and are buried in a background of normal anatomical structures. During interpretation, the desired part has to be separated from the irrelevant distribution of other structures. The other structures which do not contain diagnostic information of interest have been termed as “noise”. Here, the reference radiograph is digitized and converted into its positive image by the computer. The subsequent radiograph is then displayed on the same server and is aligned to the reference image and then digitized. Substraction of the gray levels between the two images is then performed. Any change that has occurred between the original radiograph and the subsequent radiograph shows up as light or dark areas. Loss of bone is seen as dark areas and gain of bone as the light areas (1). To compensate for variations in the film response, oral hard tissue measurements with films are sometimes made with the aid of an intraoral step wedge. Correct placement of the wedge is however a problem, because it is difficult to match the cheek thickness and the scattered radiation intensity without superimposing the step wedge image on the teeth, bone, film-positioning device, or on the occlusal registration material (20), (21). Subtraction radiography with films (22), (23) is improved by contrast and exposure corrections. Theprocess is tedious and is of questionable validity for the detection of generalized bone loss (osteopaenia). The loss of a substantial amount of bone (24), (25) would violate a fundamental assumption by changing the histogram and would therefore reduce the apparent bone loss or gain if a histogram-based correction is used (15), (26). No one has yet shown as to how to distinguish among the changes in the histogram which are due to changes in bone mass, film, exposure and processing. Indeed, an unambiguous distinction may not be possible from the image histograms alone. If contrast corrections and the use of intraoral stepwedges are fraught with difficulties, then a better and a more reproducible method for measuring x-ray attenuation is needed. (Table/Fig 1)(Courtesy: Freny R.Karjodkar, editor, Textbook of dental and maxillofacial Radiology. Jaypee brothers, Medical publishers)

Diagnosis
One of the most challenging areas of research (27) is the development of tools and procedures that can automate the detection, classification and the quantification of radiographical signs of the disease. The rationale for the use of such methods is to achieve early and accurate disease detection by using reproducible and objective criteria. The development of image analysis operations is very complex and requires a thorough understanding of anatomy, pathology and radiographical image formation. Caries detection, the classification of periodontal disease and the detection and quantification of periapical bone lesions. The success of many of these applications is highly dependent on specific imaging parameters. Very few of these provide reliable results when used clinically. This underscores the complexity of the radiographical image interpretation process.

Image store
The use of digital (27) imaging in dentistry requires an image archiving and management system which is very different from that which is used for conventional radiography. The storage of diagnostic images on magnetic or optical media raises a number of new issues that must be considered. The file size of the dental digital radiographs varies considerably, ranging from approximately 200kilobytes for intraoral images to as much as 6 megabytes for extraoral images. The storage and the retrieval of these images in an average sized dental practice is not a trivial issue. (Table/Fig 2)Fortunately, the development of new storage media and the continuing decrease in the price of a unit of storage has alleviated the capacity issue in dental radiography. The hard drive capacities of modern computers already exceed the storage needs of most dental practices. The simplicity with which a digital image can be modified though image processing, poses a potential risk with respect to ensuing the integrity of the diagnostic information. Once they are in a digital format, critical image data can be deleted or modified. [Table/Fig 3]

Image Receptors For Extraoral Radiography
Most of these OPG machines have direct digital acquisition (27) panoramic machines. The receptor on such a machine is an array that transmits an electronic signal to the controlling computer, which displays the image on the view screen as it is being acquired. The software of the unit makes internal adjustments to the acquired data to render an interpretable image on the screen. The PSP plate is processed in the same manner as an intraoral PSP, and a similar image characteristic adjustment is automatically performed by the software package. Both these digital modalities allow the user to perform post-processing modifications on the image. DICOM- digital imaging and ccommunication in medicine allows rapid communication worldwide. DICOM is the international standard language for the electronic communication of digital images, be they radiographs, photographshistopathological slides, or any other type of “Picture images.”

Clinical Consideration
Some fundmental differences from films in the clinical handling of digital receptors should be noted. Because digital receptors are intended to be reusable, they must be handled with greater care than their film counterparts. Indeed, in certain situations, films may be intentionally damaged through bending to accommodate the patient anatomy. This is never the case with digital receptors. Because of the inability of the digital detectors to be bent to accommodate patient anatomy, imaging strategies must be used for some patients.

The advantages of digital imaging (28) are that, it has a superior gray scale resolution, easy reproducibility, reduced exposure to radiation, an increased speed of image viewing, lower equipment and film cost, increased efficiency and the enhancement of the diagnostic images. It also gives an excellent quality image with no loss of quality. Loss of quality is commonly associated with conventional chemical processing. Image processing and enlargement and reconstruction for specific diagnostic purposes are possible with the help of computers. The detection of defects and the 3-dimensional visualization of the dental structures, based on radiographical data, is a possible effective patient education tool. The disadvantages include; the initial set up is costly and the sensor size is thicker than that of the intraoral films. For infection control, the sensor has to be covered adequately in a disposable plastic wrapper. There can be legal issues, because the original images can be manipulated.


Conclusion

A basic understanding of computers and the mastery of common computing skills is essential for viewing digital images. Beyond this, learning the pecularities will take time and may not be intuitive. Digital images avoid environmental pollutants which are encountered with film processing, but the initial financial outlay for digital imaging hardware make these systems more expensive than films. The mishandling of the digital system components can catastrophically shorten any projected life expectancy.

Key Message

Continuing research efforts are required to address the technical and diagnostic performance of new technologies with respect to the specific clinical needs.

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