Title Page
Copyright Page
Foreword
Acknowledgements
Chapter 1 Panoramic Radiography: History and Future Development
Aim
Outcome
Introduction
Development of the Technique
Panoramic Equipment Using an Intraoral Source of Radiation
Panoramic Equipment Using an Extraoral Source of Radiation
Further Developments
Digital Imaging
Charged Couple Device (CCD)
Photostimulable Phosphors (PSP)
Conclusion
Acknowledgements
Further Reading
Chapter 2 Dental Panoramic Radiographic Technique
Aim
Outcome
Introduction
Panoramic Image Formation
Tomography
Slit Beam Imaging
Image Magnification
Dental Panoramic Technique
Practical Procedures
Preparation
Radiography
Further Reading
Chapter 3 Anatomy
Aim
Outcome
Introduction
Hard Tissues
Mandible (Fig 3-1)
Maxilla, Antrum, Nasal Skeleton, Zygoma and Temporal Bone
Other Bony Structures
Soft Tissues
Air Shadows
Ghost Shadows
Further Reading
Chapter 4 Radiation Dose and Risk in Panoramic Radiography
Aim
Outcome
Introduction
The Biological Effects of Panoramic Radiography
Radiation Units
Measurement of Dose
Effective Dose and Risk in Panoramic Radiography
How Can We Reduce Dose to Our Patients?
Constant Potential (‘direct current’) X-Ray Generation
Field Limitation Techniques
The Use of Rare-Earth Screens
Digital Panoramic Systems
The Risks Associated with Panoramic Radiography
Conclusion
Further Reading
Chapter 5 The Use of Panoramic Radiography in General Dental Practice
Aim
Outcome
Introduction
The Development of Clinical Guidelines
The Limitations of the Panoramic Image
Magnification Variations
Overlap of Adjacent Teeth
Superimpositions
Diagnostic Accuracy and Efficacy of Panoramic Radiography
How do we Assess Radiographic Accuracy?
The Diagnostic Value of Panoramic Radiography for Common Dental Pathosis
Caries Diagnosis
Periodontal Disease
Periapical Inflammatory Pathology
The Diagnostic Value of Panoramic Radiography for Other Pathology
Prior to Oral Surgery
The Detection of Facial Fractures
Sinus Disease
Identification of Systemic Disease
The Assessment of Temporomandibular Joint Pathology
Conclusions
Routine Screening by Panoramic Radiography
Panoramic Radiography for the New Adult Patient
Edentulous Patients
Panoramic Radiography within Orthodontic Practice
Panoramic Radiography in Implantology
Conclusions
Reference
Further Reading
Chapter 6 Quality Assurance in Panoramic Radiography
Aim
Outcome
Introduction
How to Overcome Problems of Poor-Quality Images
Identifying the Problem - A Reject Film Analysis
How can we Improve Panoramic Film Quality?
Producing a DPR
Stage 1: The Darkroom
The dedicated dark room
Safe lights
Desktop processors
Film storage and film type
Cassettes
Stage 2: Operator Technique
Preparing the patient
Positioning the patient
Stage 3: X-Ray Equipment and the Image Receptor
X-ray equipment
The image receptor
Stage 4: Film Processing
Manual processing
Automatic processing
Monitoring of film processing
Stage 5: Viewing the Radiograph
Reporting of radiographs
Conclusions
Further Reading
Chapter 7 Radiographic Interpretation of Disease
Aim
Outcome
Introduction
Image Formation
Principles of Radiographic Interpretation
So How Should One Examine a DPR?
Use appropriate viewing conditions
Be familiar with the normal panoramic image
Assess image quality (see Chapter 6)
Examine the radiograph systematically
Familiarise yourself with disorders of the jaws
Relate what you see to the clinical findings
Use previous radiographs
Disorders of the Teeth
Hypodontia
Hyperdontia
Impacted Third Molars
Nature of impaction
Status of crown
Root morphology (Fig 7-5)
Association with the inferior alveolar (dental) canal
Other features to assess
Maxillary Canines
Radiographic assessment should include:
Dentinogenesis Imperfecta
Clinical features
Radiographic features
Periodontal Disease
Disorders Affecting the Jaws
Well Defined Radiolucencies of the Jaws
Radicular Cyst
Clinical features
Radiological features
Dentigerous Cyst
Clinical features
Radiological features
Odontogenic Keratocyst
Clinical features
Radiological features
Residual cyst
Clinical features
Radiological features
Ameloblastoma
Clinical features
Radiographic features
Solitary (Traumatic) Bone Cyst
Clinical features
Radiographic features
Stafne Bone Cavity
Radiographic features
Ill-Defined Radiolucencies of the Jaws
Osteomyelitis
Clinical features
Radiological features
Malignant Tumours
Mixed Density and Radiopaque Lesions of the Jaws
Sclerosing Osteitis
Radiographic features
Osteosclerosis (Dense Bone Island)
Osteoma
Bony Tori and Bony Overgrowths
Odontomes
Radiographic features
Fibrous Dysplasia
Cemento-Ossifying Lesions
Periapical Cemento-Osseous Dysplasia and Florid Cemento-Osseous Dysplasia
Clinical features
Radiological features
Cemento-Ossifying Fibroma
Clinical features
Radiological features
Trauma
Disorders in the Soft Tissues
Salivary Duct Calculi
Clinical features
Radiographic features
Calcified Lymph Node
Tonsilloliths
Foreign Bodies
Disorders of the Maxillary Sinus
Root Displaced Into the Maxillary Sinus
Clinical features
Radiographic features
Oro-Antral Fistula (OAF)
Clinical features
Radiographic features
Root-Filling Material
Radiological features
Mucous Cysts of the Maxillary Antrum
Clinical features
Radiographic features
Carcinoma of the Maxillary Sinus
Clinical features
Radiographic features
Disorders of the Temporomandibular Joint
Further Reading
Quintessentials of Dental Practice – 20
Imaging – 2
British Library Cataloguing-in Publication Data
Rushton, V. E.
Panoramic radiology. - (Quintessentials of dental practice: 20. Imaging; 2)
1. Teeth - Radiography 2. Radiography, Panoramic
I. Title II. Rout, John
617.6′07572
ISBN 1850973350
Copyright © 2006 Quintessence Publishing Co. Ltd., London
All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without the written permission of the publisher.
ISBN 1-85097-335-0
Panoramic radiology is extensively used in everyday clinical practice. It is therefore important that both existing and future practitioners are fully familiar with this imaging technique, the interpretation of panoramic images and very importantly, the indications and clinical justifications for such extraoral imaging. Practitioners using panoramic radiology must also have knowledge of relevant radiation doses, risks to patients and quality assurance protocols.
Panoramic Radiology, Volume 20 in the timely Quintessentials for General Dental Practitioners series, addresses all of these issues and, in addition, gives a great deal of practical guidance on panoramic radiology as it ought to be applied by practitioners. As with all forms of radiological examination each and every panoramic image should have a net benefit for the patient, with the exposure to ionising radiation having been optimised for the intended purpose. This excellent, succinct, generously illustrated book will assist practitioners in satisfying this requirement in relation to panoramic radiology.
As all members of the dental team should play their respective parts in ensuring the safe, appropriate and effective use of panoramic imaging, this book should find its way into the practice environment for all to study and use to good effect. An excellent addition to all practitioner and practice collections of reference texts.
Nairn Wilson
Editor-in-Chief
We would like to thank our respective families and colleagues for their help and encouragement during the writing of this book and also those patients whose clinical radiographs are integral to a book of this nature.
The aim of the chapter is to present an overview of the development of dental panoramic radiography during the past century.
After studying this chapter, the reader should have a clear understanding of the historical development of panoramic radiography and of the more recent technological advances in panoramic image production, including digital imaging techniques.
Dental panoramic radiography is a radiographic technique that produces an image of both jaws and their respective dentitions on a single extraoral radiographic film. The development of panoramic radiographic equipment represented a major innovation in the field of dental imaging as, prior to this, dental radiographic images consisted solely of intraoral and oblique lateral projections of the jaws taken using a conventional dental x-ray set.
Today panoramic radiographic equipment is found routinely both within most hospital radiology departments and in a high proportion of general dental practices. It has been estimated that around 60% of United Kingdom dentists have direct access to panoramic equipment. A similar level of use has been reported in other parts of the industrialised world.
In the early part of the 20th century, many researchers were developing techniques using movement of the x-ray tube and the film in order to visualise structures or foreign bodies (particularly bullets) situated within the patient. Andre Bocage, a French researcher, was the originator of the principles of body-section imaging. In Bocage’s seminal work, patented in 1922, the author mentions the possibility of imaging curved surfaces such as the jaws.
Further interest in this field of research did not resurface for another 20 years and resulted in the development of x-ray equipment using two quite different radiographic techniques to produce an overall image of the jaws. One group of researchers developed a small x-ray source which, when positioned intraorally, would directly expose an x-ray film moulded to the outside of the patient’s face. The other group relied upon the production of a tomographic image of the jaws with the tube positioned extraorally, combined with either an intraorally or an extraorally positioned film.
Bouchacourt first proposed the possibility of using an intraoral source of radiation to image the jaws as early as 1898. This concept was finally developed almost half a century later when two separate groups of researchers applied for patents to develop intraoral panoramic equipment. These were, in 1943, the German company of Koch and Sterzel (Fig 1-1), followed in 1951 by the Swiss researcher Dr. Walter Ott. Dr. Sydney Blackman, a British radiologist, modified the principles proposed by Dr. Ott, leading to the commercial development by Watson and Sons Ltd. of the ‘Panograph’ panoramic equipment (Fig 1-2).
Intraoral panoramic equipment used a cone-shaped anode located at the end of a thin rod (Fig 1-2) with a focal spot (the source of the x-ray beam) that was extremely small (ca. 0.1 mm) compared to conventional x-ray equipment. The intraoral technique had several inherent problems. It was extremely time-consuming, requiring separate exposures for both the maxilla and mandible (Fig 1-3). The technique also resulted in severe geometric distortion and, more importantly, delivered high doses of radiation to the oral tissues, notably the tongue. Paradoxically, these factors appeared not to have deterred the development of an intraoral panoramic unit that relied upon a radioactive isotope as its source of radiation. Fortunately, common sense prevailed and further experimentation with this type of intraoral panoramic equipment was rapidly curtailed, not least because of the obvious radiation risk but also the cost of the isotope.
Further development of the intraoral type of panoramic equipment centred upon improving patient comfort and reducing image distortion. An eccentric positioning of the x-ray tube was an attempt to improve the latter; however, the problems of geometric distortion proved insurmountable. Finally, the unacceptable dose level delivered by this type of equipment led to legislation within the United Kingdom recommending its withdrawal from clinical practice.
The records of the American Patent Office show that in 1922, a patent was issued to A.F. Zulauf for ‘Panoramic X-ray Apparatus’ (Fig 1-4). The equipment used a rotational narrow beam x-ray technique that scanned either the upper or lower jaw with an intraorally positioned waterproofed lead-backed film packet to receive the image. The x-ray generator was moved manually around the patient on a mobile carriage supported on a U-shaped table using a preformed track. The researcher clearly understood the principles of image production but also its limitations. Zulauf stressed that the exact speed of movement was ‘determined by experience and depends on the strength of the x-rays, the width of the collimator and its distance from the teeth being shadow-graphed’. While this patented design must qualify as the earliest example of rotational panoramic radiography, no further details concerning the subsequent development or the clinical use of the equipment have been found.
During the early 1930s, several researchers were active in pursuing and developing methods of imaging ‘curved’ structures such as the jaws. Numata proposed and discussed the principles of the panoramic technique as early as 1933, while at the same time constructing a suitable device for the clinical examination of the jaws. Numata’s prototype used a very narrow collimated beam of x-ray photons, often referred to as a slit beam. The x-ray equipment rotated around the patient’s head with the film positioned intraorally in the lingual sulcus.
Two researchers, Vieten and Heckmann, expounded the theoretical principles of imaging ‘curved’ structures without the superimposition of neighbouring structures. Both researchers experimented with a rotational slit beam technique to expose a film, but it was Olsson who refined the principles of an x-ray tube moving simultaneously to the detector, which is positioned behind the structure to be imaged.
In 1946, Dr. Yrjö Veli Paatero of the Institute of Dentistry, University of Helsinki, Finland, carried out similar work to that previously described by Olsson, although apparently unaware of this earlier research. The literature credits Paatero with developing and constructing the first working prototype of an extraoral rotational panoramic unit. The design of this unit was similar to that proposed by Numata in 1933. Paatero’s prototype positioned the film intraorally, requiring a separate film for each jaw. The equipment used a stationary slit collimated x-ray beam which scanned the teeth and jaws by manually rotating the patients around the x-ray source as they sat in the dental chair.
Further research by Paatero in 1949 resulted in the development of a single axis or concentric rotational panoramic system. This system incorporated a curved extraoral film cassette (Fig 1-5) rather than the time-consuming and uncomfortable intraoral placement of the image receptor. The equipment continued to use a slit collimated x-ray beam with the patient and the curved extraoral film cassette rotating around a stationary x-ray source, with the film exposed through a vertical slit. The method of exposure consisted of rotation of the patient in front of a stationary x-ray tube as the film was translated behind the vertical slit to achieve a sequential exposure.