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 , 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 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 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 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 , 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 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 . “ 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 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. 8). However, if the mandibular fractures following trauma to are still bound to the use of full mouth denture base is the jaws. intraoral surveys. There is certainly no radiopaque (e.g. One might ask why so many need for a panoramic radiograph plus a chrome-cobalt or practitioners continue using full mouth full mouth intraoral survey. The panoramic stainless steel) the intraoral series as the principal baseline- radiograph, supplemented by bitewings denture should always be imaging regimen for their patients. The and an occasional periapical is all that is removed prior to probable answer, is “force of habit” needed. This provides savings in time and panoramic radiographs following indoctrination during dental reduces patient discomfort. As the being made (Fig. 9). school training – and the perception that radiation scatter from a panoramic panoramic radiographs are of poorer radiographic machine is very small, the Finally, eyeglasses should quality. For the practitioner that feels that substitution of a panoramic radiograph also be removed before panoramic radiographs are inadequate for a full mouth intraoral radiograph series panoramic radiology as in quality, it is time to check out the new has the potential to reduce the radiation these can also obscure machines that are available. There have dose that might inadvertently affect the important image details been many improvements over the past dental office personnel. (Fig. 10). decade. Furthermore, beam geometry, In The Recent Literature:

Dental implants: The panoramic anterior . In patients requiring Bitewing and panoramic radiograph is considered the more than 5 periapical images, a radiographs provided sensitivity standard for treatment planning panoramic radiograph is preferred. values of 25 % and 19 % and dental implants. specificity values of 93 % and 97 % Dula K, Mini R, van der Stelt PF, Buser Dental caries: For detection of respectively. Receiver operating D. The radiographic assessment of occlusal dental caries, no characteristic (ROC) analysis was implant patients: decision-making statistical significance was also performed. No statistically criteria. Int J Oral Maxillofac demonstrated between panoramic significant difference in diagnostic Implants 2001 Jan;16(1):80-9. [From and bitewing radiography. quality was proven between the the Department of Oral Surgery, Thomas MF, Ricketts DN, Wilson RF. panoramic and bitewing School of Dental Medicine, Occlusal caries diagnosis in molar radiographs. Intra-examiner University of Berne, Switzerland.] teeth from bitewing and panoramic reproducibility was found to be poor radiographs. Prim Dent Care 2001 to moderate (Kappa values for Indications for the most frequently Apr;8(2):63-9. [From the Division of bitewing radiographs = 0.31-0.44, and used imaging modalities in implant Conservative Dentistry, King’s for panoramic radiographs = 0.07- dentistry are proposed based on College.] 0.54). In conclusion, no difference in clinical need and biologic risk to the overall diagnostic performance was patient. To calculate the biologic Previous studies implying that proven between bitewing and risk, the authors carried out dose panoramic radiographs are inferior panoramic radiographs for the measurements. A panoramic to bitewing radiographs for caries diagnosis of occlusal surface dentin radiograph plus a series of 4 diagnosis lacked validation. This caries. conventional tomographs of a study used an electronic caries single-tooth space in the molar meter (ECM II, LODE, Groningen, The Panoramic diagnostic yield: region carry respectively 5% and Netherlands) to validate occlusal Optimization of the diagnostic yield 13% of the risk from computed caries diagnosis made from from panoramic radiographs . The authors indicate bitewing and panoramic requires a systematic approach that panoramic radiography is radiographs. Forty-nine Army with special attention to high yield considered the standard recruits were examined with the areas. radiographic examination for ECM, and had bitewing and Monsour PA. Getting the most from treatment planning of implant panoramic radiographs made. In rotational panoramic radiographs. patients, because it imparts a low total, 299 molar occlusal surfaces Aust Dent J 2000 Jun;45(2):136-42. dose while giving the best were available for examination. [From the Queensland Diagnostic radiographic survey. Periapical Seven examiners viewed the Imaging, Holy Spirit Hospital, radiographs are used to elucidate bitewing and panoramic Brisbane, Australia.] details or to complete the findings radiographs on two separate obtained from the panoramic occasions and rated each occlusal Rotational panoramic radiography radiograph. Other radiographic surface for dentin caries using a five is an invaluable tool in modern methods, such as conventional film interval scale (1: almost definitely no dentistry. To use the full potential of tomography or computed caries, 2: probably no caries, 3: this resource the entire radiograph tomography, are applied only in unsure, 4: caries probably present, must be examined in a systematic special circumstances, film and 5: caries almost definitely way to extract the great wealth of tomography being preferred for present). To determine intra-rater information available. A framework smaller regions of interest and reliability, repeat measures were should be applied for the computed tomography being made on 20 % of the radiographs at development of a systematic justified for the complete maxilla or two further separate sittings. ECM method to examine panoramic mandible when methods for dose conductance readings greater than radiographs. The essential elements reduction are followed. During 9 were taken to indicate dentin are that all areas of the radiograph follow-up, intraoral radiography is caries. Examiner decisions that should be examined and that there considered the standard caries was probably and definitely are a number of high yield areas radiographic examination, considered to be present were with regard to pathology that particularly for implants in the taken as positive diagnoses. require special attention. Risk assessment: The risk from Age estimation for forensic purposes is radiograph of the hand, a radiation radiation used in making a usually based on a panoramic dose of 0.15 mGy was adopted. panoramic radiograph is less than radiograph of the teeth or a radio- Mortality risks obtained were 1.8 x 10-7 one in a million. It is of a similar graph of the left hand. Procedure for a panoramic radiograph and 5.1 x magnitude to the risks associated mortality risks were calculated using 10-8 for a radiograph of the hand. By with public road traffic encountered both the risk coefficients of comparison, it was estimated that on the way to the examination. International Committee for Radiation the calculated risks is approximately Jung H. The radiation risks from x-ray Protection and the mass ratio of equivalent to the mortality risks studies for age assessment in radiation-exposed portion to total associated with public road traffic criminal proceedings Rofo Fortschr organ. For a panoramic radiograph during less 2.5 hours or one hour, Geb Rontgenstr Neuen Bildgeb the following doses were used: respectively. The calculated radia- Verfahr 2000 Jun;172(6):553-6. [From surface and red bone marrow 0.25 tion risks are of similar magnitude to the Institute of Biophysics, Hamburg mGy, skin on the neck 0.56 mGy, the risks the person is exposed to on University, Germany.]. thyroid gland 0.053 mGy. For a the way to the examination. Frequently Asked Questions About Film Quality: Q: What are these odd clear in the intensifying screens. film and the developing solution. artifacts on our films? Examine the screens for damage. Keep your hands and the area A: Clear artifacts fall into four If the screens are damaged it is where you handle the film, general categories. permanent. Make sure the screens cassettes and screens clean. 1. Clear artifacts caused by metal are not handled roughly, folded, 3. Black “starburst”, “tree branch”, or or radiopaque objects on or in or stored in an unsafe location. “lightning bolt” artifacts caused the patient. Jewelry, eyeglasses, by static electric discharges. The and radiopaque dental Q: What are these black marks on intensifying screens need to be prostheses should be removed our films? treated with antistatic/screen before the radiograph is made. A: Black artifacts on films fall into cleaner solution or mild soapy 2. Clear triangular shape in the lower four general categories. water. Apply solution to anterior caused by improper 1. Black ends or corners caused by intensifying screens only, not position of the patient lead exposure to white light. Usually a cassette sleeve. Remove screens shield. Make sure the shield is torn cassette or an exposed box from the cassette and place placed low enough on the of film is the culprit. Physically them on a clean countertop. patient’s shoulder and neck so as check the cassette sleeve for Apply solution to inside and not interfere with the X-ray beam. tears and replace sleeve if outside of the screens. Partially 3. “Tube Side” decal is visible on the necessary. To check a box of film dry the screens and allow the developed film. The decal will for exposure take one sheet of remaining solution to air dry. appear when the intensifying film out of the box, under Make sure the screens are screens are inverted (inside out) safelight conditions, and process completely dry before reloading or the film was not between the it at normal time and into the cassette. screens. Orient the screens so temperature settings. The film 4. Black “crescent” or “half moon” that the “Tube Side” decal is on should develop clear/translucent. artifacts caused by dented film the outside and the left and right If the film develops with artifacts or intensifying screens. Thumb- markers (L & R) are inside. Make similar to the problem film, the nails or rough handling of the film sure the “Tube Side” decal side of box of film needs to be replaced. or screens usually makes dents. the screens is aligned with the 2. Black spots or smudges caused by Any stress to the film, thumbnail “This Side Toward Tube” side of a foreign substance dent, a sharp crease, a heavy the cassette sleeve. Insert the film contaminating the film. Glove object dropped onto the film, between the intensifying screens. powder residue is usually the will develop black. If no dents are 4. Distinct clear lines, scratches, or source of this artifact. Any visible on the film surface cracks, visible on the developed substance on the film before it is examine the screens. Damage to film. These odd artifacts are developed will effect the the screens is permanent. Make usually caused by cracks or splits chemical reaction between the sure the area where you handle films is accessible and uncluttered. Store cassettes in a location where they will not be damaged.

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