Panoramic radiograph

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Panoramic radiograph
Panoramicfilm.JPG
A dental panoramic radiograph, showing the maxilla and mandible, all the teeth including the "wisdom teeth," the frontal and maxillary sinuses, the nasal cavity and the temporomandibular joint and other near by head and neck anatomy.
MeSH D011862

A panoramic radiograph is a panoramic scanning dental X-ray of the upper and lower jaw. It shows a two-dimensional view of a half-circle from ear to ear. Panoramic radiography is a form of focal plane tomography; thus, images of multiple planes are taken to make up the composite panoramic image, where the maxilla and mandible are in the focal trough and the structures that are superficial and deep to the trough are blurred.

Contents

Other nonproprietary names for a panoramic radiograph are dental panoramic radiograph and pantomogram; Abbreviations include PAN, DPR, OPT, and OPG (the latter, based on genericizing a trade name, are often avoided in medical editing).

Types

A panoramic radiograph of a 9 year old in mixed dentition Mixed dentition pan.jpg
A panoramic radiograph of a 9 year old in mixed dentition
A basic panoramic radiograph Basic panoramic radiograph.jpg
A basic panoramic radiograph
A Panoramic radiography machine. Panoramic Xray.jpg
A Panoramic radiography machine.

Dental panoramic radiography equipment consists of a horizontal rotating arm which holds an X-ray source and a moving film mechanism (carrying a film) arranged at opposed extremities. The patient's skull sits between the X-ray generator and the film. The X-ray source is rectangular collimated beam. [1] Also the height of that beam covers the mandibles and the maxilla regions. The arm moves and its movement may be described as a rotation around an instant center which shifts on a dedicated trajectory.

The manufacturers propose different solutions for moving the arm, trying to maintain constant distance between the teeth to the film and generator. Also those moving solutions try to project the teeth arch as orthogonally as possible. It is impossible to select an ideal movement as the anatomy varies very much from person to person. Finally a compromise is selected by each manufacturer and results in magnification factors which vary strongly along the film (15%-30%). The patient positioning is very critical in regard to both sharpness and distortions.[ citation needed ]

Films

There are two kinds of film moving mechanisms, one using a sliding flat cassette which holds the film, and another using a rotating cylinder around which the film is wound. There are two standard sizes for dental panoramic films: 30 cm × 12 cm (12″ × 5″) and 30 cm x 15 cm (12″ × 6″). The smaller size film receives 8% less X-ray dosage on it compared to the bigger size.

Digital

Dental X-rays' radiology is moving from film technology (involving a chemical developing process) to digital X-ray technology, which is based on electronic sensors and computers. One of the principal advantages compared to film based systems is the much greater exposure latitude. This means many fewer repeated scans, which reduces costs and also reduces patient exposure to radiation. Lost X-rays can also be reprinted if the digital file is saved. Other significant advantages include instantly viewable images, the ability to enhance images, the ability to email images to practitioners and clients (without needing to digitize them first), easy and reliable document handling, reduced X-ray exposure, that no darkroom is required, and that no chemicals are used.

One particular type of digital system uses a photostimulable phosphor plate (aka PSP - Phosphor Plate) in place of the film. After X-ray exposure the plate (sheet) is placed in a special scanner where the latent formed image is retrieved point by point and digitized, using a laser light scanning. The digitized images are stored and displayed on the computer screen. This method is in between old film based technology and the current direct digital imaging technology. It is similar to the film process because it involves the same image support handling and differs because the chemical development process is replaced by the scanning process. This is not much faster than film processing and the resolution and sensitivity performances are contested. However it has the clear advantage of being able to fit with any existing equipment without any modification because it replaces just the existing film.

Also sometimes the term "digital X-rays" is used to designate the scanned film documents which further are handled by computers.

The other types of digital imaging technologies use electronic sensors. A majority of them first convert the X-rays in light (using a GdO2S or CsI layer) which is further captured using a CCD or a CMOS image sensor. Few of them use a hybrid analog-to-digital arrangement which first converts the X-ray into electricity (using a CdTe layer) and then this electricity is rendered as an image by a reading section based on CMOS technology.

In current state-of-the-art digital systems, the image quality is vastly superior to conventional film-based systems. The latest advancements have also seen the addition on Cone Beam 3D Technology to standard digital panoramic devices.

Indications

Panoramic radiograph showing horizontally impacted lower wisdom teeth. PAN TEETH.jpg
Panoramic radiograph showing horizontally impacted lower wisdom teeth.
Minimally-displaced fracture in right mandibular. Arrow marks fracture, root canal on central incisor, teeth to the left of fracture do not touch Simple mandible fracture.jpg
Minimally-displaced fracture in right mandibular. Arrow marks fracture, root canal on central incisor, teeth to the left of fracture do not touch
Panoramic radiograph showing Stafne defect (arrowed). Stafne defect panorex.jpg
Panoramic radiograph showing Stafne defect (arrowed).
Dental panoramic radiograph showing dentigerous cyst (arrowed). JawCyst (with arrows).jpg
Dental panoramic radiograph showing dentigerous cyst (arrowed).

Orthopantomograms (OPTs) are used by health care professionals to provide information on:

Mechanism

Normally, the person bites on a plastic spatula so that all the teeth, especially the crowns, can be viewed individually. The whole orthopantomogram process takes about one minute. The patient's actual radiation exposure time varies between 5.5 and 22 seconds for the machine's excursion around the skull.

The collimation of the machine means that, while rotating, the X-rays project only a limited portion of the anatomy onto the film at any given instant but, as the rotation progresses around the skull, a composite picture of the maxillo-facial block is created. While the arm rotates, the film moves in a such way that the projected partial skull image (limited by the beam section) scrolls over it and exposes it entirely. Not all of the overlapping individual images projected on the film have the same magnification because the beam is divergent and the images have differing focus points. Also not all the element images move with the same velocity on the target film as some of them are more distant from and others closer to the instant rotation center. The velocity of the film is controlled in such fashion to fit exactly the velocity of projection of the anatomical elements of the dental arch side which is closest to the film. Therefore, they are recorded sharply while the elements in different places are recorded blurred as they scroll at different velocity.

The dental panoramic image suffers from important distortions because a vertical zoom and a horizontal zoom both vary differently along the image. The vertical and horizontal zooms are determined by the relative position of the recorded element versus film and generator. Features closer to the generator receive more vertical zoom. The horizontal zoom is also dependent on the relative position of the element to the focal path. Features inside the focal path arch receive more horizontal zoom and are blurred; features outside receive less horizontal zoom and are blurred.

The result is an image showing sharply the section along the mandible arch, and blurred elsewhere. For example, the more radio-opaque anatomical region, the cervical vertebrae (neck), shows as a wide and blurred vertical pillar overlapping the front teeth. The path where the anatomical elements are recorded sharply is called "focal path".

Principal advantage of panoramic images

Preparation

Persons who are to undergo panoramic radiography usually are required to remove any earrings, jewellery, hair pins, glasses, dentures or orthodontic appliances. [4] If these articles are not removed, they may create artifacts on the image (especially if they contain metal) and reduce its usefulness. There is also a need for the person to stay absolutely still during the 18 or so second cycle it takes for the machine to expose the film. For this reason, radiographers often explain to the person beforehand how the machine will move. [4]

Adverse effects

Like any medical imaging utilizing ionizing radiation, there will be a minute degree of direct ionizing damage and indirect damage from free radicals created during the ionization of water molecules within cells. A rough estimate of the risk of fatal cancer from a panoramic radiograph is about 1 in 20,000,000. [4] The age of the person being imaged also alters the risk, with younger people having a slightly higher risk. E.g. the 1 in 20,000,000 risk would be doubled for someone in the 1-10 age group (1 in 10,000,000). [4]

History

Historical milestones for digital panoramic systems

1985–1991 – The first attempt to build a dental digital panoramic was of McDavid et al. at UTHSCSA. [5] Their idea was based on a linear pixel array(single pixel column) sensor which was not appropriate for such an application because: a) there is no tomographic effect; b) huge difficulties to collimate the X-rays beam and to control the X-ray dose delivered to the patient; c) poor generator efficiency.

DXIS - real time display RotatingPan.gif
DXIS - real time display

1995 – DXIS, the first dental digital panoramic X-rays system available on the market, created by Catalin Stoichita at Signet (France). DXIS targeted to retrofit all the panoramic models.
1997 – SIDEXIS, of Siemens (currently Sirona Dental Systems, Germany) offered a digital option for Ortophos Plus panoramic unit, DigiPan of Trophy Radiology (France) offered a digital option for the OP100 panoramic made by Instrumentarium (Finland).
1998–2004 – many panoramic manufacturers offered their own digital systems.

Research

Arrows point to two vertical white lines which is how calcifications in the first part (proximal component) of the internal carotid artery appear on panoramic radiographs. X-ray64A.JPG
Arrows point to two vertical white lines which is how calcifications in the first part (proximal component) of the internal carotid artery appear on panoramic radiographs.
A line drawing depicting a panoramic radiograph with an ovoid atheroma in the bifurcation region of the common carotid artery (CCA) as it bifurcates (divides) in the neck into the internal carotid artery (ICA) which supplies blood to the brain and the external carotid artery (ECA) which supplies blood to the face and mouth. X-ray65B.JPG
A line drawing depicting a panoramic radiograph with an ovoid atheroma in the bifurcation region of the common carotid artery (CCA) as it bifurcates (divides) in the neck into the internal carotid artery (ICA) which supplies blood to the brain and the external carotid artery (ECA) which supplies blood to the face and mouth.

Panoramic radiographs have the capability to demonstrate a portion of the neck and display atheromas (calcifications in the carotid artery) which are an indication of both local and generalized (systemic) atherosclerosis. Atherosclerosis of the coronary arteries leading to myocardial infarction (heart attack), and atherosclerosis of the carotid artery leading to stroke are the number one and number three most common causes of death in the United States. [6]

There is interest to look at panoramic radiographs as a screening tool, however further data is needed with regards if it is able to make a meaningful difference in outcomes. [7]

Epidemiology: general public and high risk groups

Additional research projects have further determined the prevalence rate of these atheromas in the general population (3–5%) [8] [9] and among high-risk groups (over 25% in: recent stroke victims, [10] individuals with obstructive sleep apnea syndrome, [11] [12] [13] postmenopausal women, [14] [ non-primary source needed ] type 2 diabetics, [15] [13] [16] individuals with dilated cardiomyopathy, [17] [13] and among individuals who have received radiotherapy directed at the neck, [18] [ non-primary source needed ] [19] [ non-primary source needed ]). These findings have been corroborated by other several other researchers. [20] [21] [22] [23] [13]

Dental infection and atherosclerosis

Atherosclerosis is attributed to risk factors that include cigarette smoking, hyperlipidemia, obesity, diabetes mellitus, and hypertension (high blood pressure). These factors, however, do not fully account for the risk of disease. Atherosclerosis has been conceptualized as a chronic inflammatory response to endothelial cell injury [24] and dysfunction possibly arising from chronic dental infection. In 2010, using the previously validated Mattila panoramic radiographic index to quantify the totality of dental infection (i.e., periapical and furcal lesions, pericoronitis sites, carious tooth roots, teeth with pulpal caries, and vertical bony defects), Friedlander's group determined that individuals with carotid artery atheromas on their panoramic radiographs had significantly greater amounts of dental infection/inflammation than atherogenic risk-matched controls devoid of radiographic atheromas. [25] [ non-primary source needed ] [26] [ non-primary source needed ] While the Mattila index had been previously used to relate the extent of dental infection to coronary artery disease, this research is the first to link the full range of dental disease that it measures to panoramic radiographs evidencing calcified carotid artery atherosclerosis.

See also

Related Research Articles

<span class="mw-page-title-main">Atherosclerosis</span> Form of arteriosclerosis

Atherosclerosis is a pattern of the disease arteriosclerosis, characterized by development of abnormalities called lesions in walls of arteries. These lesions may lead to narrowing of the arterial walls due to buildup of atheromatous plaques. At onset there are usually no symptoms, but if they develop, symptoms generally begin around middle age. In severe cases, it can result in coronary artery disease, stroke, peripheral artery disease, or kidney disorders, depending on which body parts(s) the affected arteries are located in the body.

<span class="mw-page-title-main">Radiography</span> Imaging technique using ionizing and non-ionizing radiation

Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical and industrial radiography. Similar techniques are used in airport security,. To create an image in conventional radiography, a beam of X-rays is produced by an X-ray generator and it is projected towards the object. A certain amount of the X-rays or other radiation are absorbed by the object, dependent on the object's density and structural composition. The X-rays that pass through the object are captured behind the object by a detector. The generation of flat two-dimensional images by this technique is called projectional radiography. In computed tomography, an X-ray source and its associated detectors rotate around the subject, which itself moves through the conical X-ray beam produced. Any given point within the subject is crossed from many directions by many different beams at different times. Information regarding the attenuation of these beams is collated and subjected to computation to generate two-dimensional images on three planes which can be further processed to produce a three-dimensional image.

<span class="mw-page-title-main">Radiology</span> Branch of Medicine

Radiology is the medical specialty that uses medical imaging to diagnose diseases and guide their treatment, within the bodies of humans and other animals. It began with radiography, but today it includes all imaging modalities, including those that use no electromagnetic radiation, as well as others that do, such as computed tomography (CT), fluoroscopy, and nuclear medicine including positron emission tomography (PET). Interventional radiology is the performance of usually minimally invasive medical procedures with the guidance of imaging technologies such as those mentioned above.

<span class="mw-page-title-main">Coronary catheterization</span> Radiography of heart and blood vessels

A coronary catheterization is a minimally invasive procedure to access the coronary circulation and blood filled chambers of the heart using a catheter. It is performed for both diagnostic and interventional (treatment) purposes.

<span class="mw-page-title-main">Atheroma</span> Accumulation of degenerative material in the inner layer of artery walls

An atheroma, or atheromatous plaque, is an abnormal accumulation of material in the inner layer of an arterial wall.

<span class="mw-page-title-main">Cerebral angiography</span> Angiography that produces images of blood vessels in and around the brain

Cerebral angiography is a form of angiography which provides images of blood vessels in and around the brain, thereby allowing detection of abnormalities such as arteriovenous malformations and aneurysms. It was pioneered in 1927 by the Portuguese neurologist Egas Moniz at the University of Lisbon, who also helped develop thorotrast for use in the procedure.

<span class="mw-page-title-main">Chest radiograph</span> Projection X-ray of the chest

A chest radiograph, called a chest X-ray (CXR), or chest film, is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest radiographs are the most common film taken in medicine.

<span class="mw-page-title-main">Carotid artery stenosis</span> Medical condition

Carotid artery stenosis is a narrowing or constriction of any part of the carotid arteries, usually caused by atherosclerosis.

<span class="mw-page-title-main">Digital subtraction angiography</span> Method for delineating blood vessels using contrast medium

Digital subtraction angiography (DSA) is a fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a "pre-contrast image" or mask from subsequent images, once the contrast medium has been introduced into a structure. Hence the term "digital subtraction angiography. Subtraction angiography was first described in 1935 and in English sources in 1962 as a manual technique. Digital technology made DSA practical starting in the 1970s.

<span class="mw-page-title-main">Dentinogenesis imperfecta</span> Medical condition

Dentinogenesis imperfecta (DI) is a genetic disorder of tooth development. It is inherited in an autosomal dominant pattern, as a result of mutations on chromosome 4q21, in the dentine sialophosphoprotein gene (DSPP). It is one of the most frequently occurring autosomal dominant features in humans. Dentinogenesis imperfecta affects an estimated 1 in 6,000-8,000 people.

Dilaceration is a developmental disturbance in shape of teeth. It refers to an angulation, or a sharp bend or curve, in the root or crown of a formed tooth. This disturbance is more likely to affect the maxillary incisors and occurs in permanent dentition. Although this may seem more of an aesthetics issue, an impacted maxillary incisor will cause issues related to occlusion, phonetics, mastication, and psychology on young patients.

<span class="mw-page-title-main">Eagle syndrome</span> Medical condition

Eagle syndrome is an uncommon condition commonly characterized but not limited to sudden, sharp nerve-like pain in the jaw bone and joint, back of the throat, and base of the tongue, triggered by swallowing, moving the jaw, or turning the neck. First described by American otorhinolaryngologist Watt Weems Eagle in 1937, the condition is caused by an elongated or misshapen styloid process and/or calcification of the stylohyoid ligament, either of which interferes with the functioning of neighboring regions in the body, such as the glossopharyngeal nerve.

<span class="mw-page-title-main">Stafne defect</span> Mandibular depression

The Stafne defect is a depression of the mandible, most commonly located on the lingual surface. The Stafne defect is thought to be a normal anatomical variant, as the depression is created by ectopic salivary gland tissue associated with the submandibular gland and does not represent a pathologic lesion as such. This cavity is commonly observed on panoramic radiograph.

<span class="mw-page-title-main">Dentin dysplasia</span> Medical condition

Dentin dysplasia (DD) is a rare genetic developmental disorder affecting dentine production of the teeth, commonly exhibiting an autosomal dominant inheritance that causes malformation of the root. It affects both primary and permanent dentitions in approximately 1 in every 100,000 patients. It is characterized by the presence of normal enamel but atypical dentin with abnormal pulpal morphology. Witkop in 1972 classified DD into two types which are Type I (DD-1) is the radicular type, and type II (DD-2) is the coronal type. DD-1 has been further divided into 4 different subtypes (DD-1a,1b,1c,1d) based on the radiographic features.

<span class="mw-page-title-main">Dental radiography</span> X-ray imaging in dentistry

Dental radiographs, commonly known as X-rays, are radiographs used to diagnose hidden dental structures, malignant or benign masses, bone loss, and cavities.

<span class="mw-page-title-main">Projectional radiography</span> Formation of 2D images using X-rays

Projectional radiography, also known as conventional radiography, is a form of radiography and medical imaging that produces two-dimensional images by X-ray radiation. The image acquisition is generally performed by radiographers, and the images are often examined by radiologists. Both the procedure and any resultant images are often simply called 'X-ray'. Plain radiography or roentgenography generally refers to projectional radiography. Plain radiography can also refer to radiography without a radiocontrast agent or radiography that generates single static images, as contrasted to fluoroscopy, which are technically also projectional.

A coronary CT calcium scan is a computed tomography (CT) scan of the heart for the assessment of severity of coronary artery disease. Specifically, it looks for calcium deposits in atherosclerotic plaques in the coronary arteries that can narrow arteries and increase the risk of heart attack. These plaques are the cause of most heart attacks, and become calcified as they develop.

<span class="mw-page-title-main">Keutel syndrome</span> Medical condition

Keutel syndrome (KS) is a rare autosomal recessive genetic disorder characterized by abnormal diffuse cartilage calcification, hypoplasia of the mid-face, peripheral pulmonary stenosis, hearing loss, short distal phalanges (tips) of the fingers and mild mental retardation. Individuals with KS often present with peripheral pulmonary stenosis, brachytelephalangism, sloping forehead, midface hypoplasia, and receding chin. It is associated with abnormalities in the gene coding for matrix gla protein, MGP. Being an autosomal recessive disorder, it may be inherited from two unaffected, abnormal MGP-carrying parents. Thus, people who inherit two affected MGP alleles will likely inherit KS.

<span class="mw-page-title-main">Cone beam computed tomography</span> Medical imaging technique

Cone beam computed tomography is a medical imaging technique consisting of X-ray computed tomography where the X-rays are divergent, forming a cone.

<span class="mw-page-title-main">Pulp stone</span>

Pulp stones are nodular, calcified masses appearing in either or both the coronal and root portion of the pulp organ in teeth. Pulp stones are not painful unless they impinge on nerves.

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