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Volume 2, Issue 1 US $6.00 Editor: Ghost Images: Objects outside the image Allan G. Farman, BDS, PhD layer that are not entirely excluded from the (odont.), DSc (odont.), Diplomate of the panoramic radiograph American Board of Oral 50 years of trial and error by the and Maxillofacial By Dr. Allan G. Farman in Radiology, Professor of collaboration with Dr. Ali Shafie various manufacturers of Radiology and Imaging panoramic dental systems. Many Sciences, Department of Panoramic radiographs consist of ghost images are actually from Surgical and Hospital Dentistry, The University of a series of narrow tomograms normal anatomic structures. For Louisville School of sequentially scanned onto the example, in the edentulous patient Dentistry, Louisville, KY. detector (usually film in a having relatively thin soft tissues, it cassette) beneath a secondary slit. is not uncommon for the ghost Contributor: Panoramic radiology aims to image of the mandibular ramus to produce a complete view of both be clearly demonstrated in Ali Shafie, DMD, General dental arches and their adjacent magnified form over the Dental Practice, Louisville, KY. structures with minimal geometric contralateral mandibular body distortion and with minimal overlap (Fig. 1). The presence of such a of anatomic details from the ghost shadow of normal anatomic Featured Articles: contralateral side. To achieve this, structures is not an error in the patient’s head is maintained technique, but rather a normal Ghost Images: Objects stationary in a cephalostat about finding when using panoramic outside the image layer that are not entirely excluded which the radiation source and radiology on some patients. from the panoramic X-ray detector rotate. A curved While ghost images of some radiograph image layer is generally achieved anatomic structures cannot be using a continuously changing avoided, most ghost images can Panoramic imaging verses center of rotation. Objects that are be excluded or reduced. A very intraoral surveys: An opinion within the selected image layer are common unwanted image is that clearly visible in the image, while of the cervical spine reflected In the Recent Literature: objects outside the image layer over the mandibular incisor teeth are deliberately blurred out of (Fig. 2). This is best prevented by Dental Implants recognition. The degree to which having the patient stand, or sit, Dental Caries the blurring of extraneous details is upright with their neck straight and successful is dependent upon a extended, rather than slouched Panoramic Diagnostic Yield number of factors. There factors during panoramic exposures. If the include (1) the atomic density of patient’s neck is slouched, the Risk Assessment the contents of the object; (2) the X-ray beam traverses several bulk of the content of the object; cervical vertebrae on the way to F.A.Q.s (3) the proximity of the object to exposing the incisor view causing Film Quality the image layer; and (4) the bulk an opaque shadow of the spine to and density of the patient’s soft obscure details of the incisor tissues. teeth. Anatomic Ghosts Jewelry Ghosts Panoramic Corporation All panoramic radiographs include Jewelry, such as earrings, is usually [email protected] ghost images even though these constructed of materials with high are minimized following more than atomic density, and is generally “ While ghost images of some anatomic structures cannot be avoided, most ghost images can be excluded or reduced.” outside the image layer. It can Fig. 1. Panoramic radiograph of an frequently lead to ghost image edentulous patient. The formation. All patients (male and true image of the right female) should be asked to remove mandibular angle is the jewelry around the head and outlined by white neck before panoramic arrows. The ghost image radiography is performed. Ghost of the same structure is outlined using black images of earrings are generally arrows. magnified and displayed over the maxillary sinus and body of the mandible on the opposite side of the radiographic image (Fig. 3.) Their actual appearance will be Fig. 2. Detail of dictated by their orientation (Fig. 4). panoramic radiograph Particular care needs to be taken if showing how the shadow of the spine the earring is unilateral and solid as can obscure detail of the ghost might be mistaken for an the mandibular anterior odontoma or other radiopaque teeth if the patient’s disease entity. Bullets and shrapnel neck is not kept erect in the soft tissues may also cause during panoramic radiography. ghost images to appear magnified and contralaterally in the panoramic radiographic image (Fig. 5). Tongue rings are centrally positioned and can cast a Fig. 3. Bilateral earrings radiopaque shadow upwards over and their ghost images. the nasal passageway (Fig. 6). The actual shadow depends on where the tongue is positioned during the making of the panoramic image. Lead Apron As the X-ray beam is well– collimated for panoramic dental radiography, a lead apron is now not required for patient safety in many parts of the world; however, Fig. 4. Appearance of requirements do remain in some the earrings is dependent upon their parts of the USA, including relative position with Kentucky. The use of a leaded respect to the incoming garment is to protect the patient X-ray beam. In this case, against radiation; hence, if worn it the right earrings are should face the incoming beam. In rotated so both the real panoramic radiography the beam and ghost images differ in appearance from the comes from the rear of the patient. earring on the other side. The apron should be draped around Fig. 5. Sharp opaque images on the left side of Fig. 6. Tongue rings have become evermore frequent. The patient the image are buckshot. The indistinct opaque is often reluctant to remove this device. It can case a images on the right side are ghost images. radiopaque shadow upwards superimposed in the midline over the nasal passageway. Fig. 8. Sometimes it is not a bad idea to leave dentures with entirely radiolucent bases in place to facilitate patient positioning Fig. 7. A lead apron raised up on the right for panoramic radiography. In such cases the artificial teeth are shoulder has cast a radiopaque image on the usually radiopaque – but rarely hide important details so long as left side of the image in the premolar region. the patient is properly positioned. Fig. 9. Where denture bases are radiopaque Fig. 10. This patient has not removed the eyeglasses and also has a the denture should always be removed prior unilateral earring on the left side. The primary image of the to panoramic radiology being performed. eyeglasses while not desired, probably does not obscure relevant Otherwise the primary image of the denture information. The left earring has cast a ghost image over the base will exclude necessary details from the maxillary right tuberosity region and obscures important interpretation. information concerning an unerupted third molar tooth. “ The panoramic radiograph supplemented by bitewings and an occasional periapical is all that is needed.” the patients back rather Panoramic imaging verses intraoral surveys: An opinion than over their chest. In any event, it is necessary By Dr. Allan G. Farman film and patient positioning for reliable to make sure that the results are much easier for panoramic lead apron is placed All radiographs should be selected radiography than for periapical imaging. smoothly over the according to the professional judgment The panoramic radiograph also permits a patient’s shoulders. A of the dental specialist. This follows the clear identification of the patient, lead apron rising up at taking of a health and dental history and procedure date and laterality of the patient’s shoulder will careful clinical inspection of the oral structures. It is difficult to replace produce an artifact in and para-oral structures. The panoramic periapical radiographs lost from film the same manner as radiograph has the advantage of mounts – individual intraoral radiographs occurs with earrings; providing a wide overview of the dental cannot be labeled. namely, contralaterally arches in which the structures can be Admittedly, radiographs made using clearly related. It provides a greater area intraoral direct emulsion film have a (Fig. 7) over the body of of coverage than the full mouth somewhat higher spacial resolution than the mandible, possibly periapical image series, while using a those made using extraoral film-screen extending over the lower average dosage of radiation. The combinations. The question to be asked maxillary sinus. time taken to make a panoramic image is where such fine resolution is needed? is a small fraction of that required to It is possible to supplement the baseline Prostheses make and mount a full mouth intraoral panoramic radiograph with bitewings to Dental protheses are survey. It is much more comfortable for assist in detection of early proximal generally within the the patient than the cutting edge of dental caries. Where endodontics is to image layer, and cast films inserted into the mouth, and it be performed, the periapical radiograph primary rather than ghost simplifies issues of infection control in is needed to assess the numbers and images. When the the operatory and in the darkroom. The positions of a fine root canals as these denture base is entirely panoramic radiograph is ideal for are not adequately displayed on the radiolucent, the denture assessment of growth and development panoramic image. For all other may be left in place to of the dentition at ages 6, 12 and 18 years radiographic assessments of the teeth aid patient positioning and as a baseline in the assessment of and jaws the panoramic radiograph is during panoramic the jaws of the edentulous adult. It is also generally adequate alone. radiography, without loss recognized as being the method of Perhaps it is time to rethink imaging of needed image details choice for evaluation of possible strategies and try something new if you (Fig.

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