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Panoramic Roentgenography a Clinical Evaluation
PANORAMIC ROENTGENOGRAPHY A Clinical Evaluation
Louis D. Mitchell, Jr.,* D.D.S., Richmond, Va.
For many years there has been virtually universal agreement that roentgenograms are indispensable aids to dental diagnosis and treatment planning. No such una nimity has been reached, however, as to what constitutes “adequate” or “com plete” roentgenographic coverage. Many dentists would insist that 18 to 24 films are needed for the adult patient. But even among those who consider 10 to 14 intraoral films sufficient for the usual full-mouth series, it is doubtful that there are many dentists (if any patients at all) who have not wished, frequently and devoutly, for a quicker and more comfortable way— some sort of “oneshot” or “instant” method— for making dental roentgenograms. Unfortunately, as yet no royal road to roentgenography is quite ready for regu lar travel. It is possible, however, with the “panoramic” equipment available, to produce a useful roentgenogram of the dental structures on a single film. This can be done in a fraction of the time required for a conventional full-mouth series. How useful will these films be? What place will this method have in practice? Although categorical answers to such questions would be premature, the pur pose of this paper is to suggest some tentative answers, based on use of “Panorex” equipment in the Medical College of Virginia School of Dentistry.
BACKGROUND
Several separate but essentially similar methods have been developed for apply ing the principles of what is generally called “body-section roentgenography” to the dental structures, producing images of the entire maxilla and mandible on one film. These methods are analogous to a group of technics used in medical roentgenography described variously by such terms as “tomography,” “planigra phy,” “laminagraphy,” and so forth. They produce visible images of structures in selected planes (or, more precisely, in layers or sections). This is done by caus ing the shadows of structures outside the selected plane or section to be so blurred as to leave clearly recorded on the film only the image of the area “in focus.” The principles on which these methods are based and the development of equip ment for applying them to dental use have been described in detail by Nelsen and Kumpula1; by Blackman of Eng land2; and by Hudson, Kumpula and Dickson.3 The latter, working together at the National Bureau of Standards, pro duced the prototype apparatus which led to the development of the machine now marketed under the trade name “ Panorex.” Kumpula4 has recently reviewed the subject from the historical standpoint, discussing the present status of panoramic
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roentgenography, as has Paatero,5 who uses the term “pantomography” to de scribe the system which he has been active in developing. Both have described tech nical differences and have drawn com parisons between various devices which have been used. Kraske and Mazzarella6 have reported an evaluation of panoramic dental equip ment ( “Panorex” ) as used by the United States Navy at Great Lakes, 111. Their study was- concerned with the value of the method in forensic identification and dental records for the armed services as well as its uses in dentistry for naval per sonnel. TE C H N IC A L CONSIDERATIONS
Mechanical features of several variations of panoramic roentgenographic equip ment have been described in detail by others.3'5 The machine used for this study is the Panorex, of the “double-eccentric” type, equipped with a 90 K V P x-ray tube having a focal spot of 0.8 mm. The target-film distance is about 17 inches, and the machine’s exposure cycle is about 35 seconds. The target-skin distance var ied for patients of different size, and at different times in the cycle of rotation, from about 7.5 to about 13 inches. The machine exhibited operating characteris tics essentially similar to those reported by Kraske and Mazzarella.6 Eastman Kodak Royal Blue film was used in 5 inch by 12 inch cassettes fitted with Dupont “detail” intensifying screens. Kilovoltage peak and milliamperage val ues were varied according to age and size of patients, with 5 ma. at 85 kvp. as the usual setting for adults of average size. Standardized time-temperature darkroom procedures were maintained in processing the films. A fair degree of proficiency in operat ing the Panorex was acquired easily and quickly. Despite minor difficulties in ad justing the apparatus to accommodate patients with large heads, necks and shoulders, it can be operated with less trouble than often is encountered in posi
tioning intraoral films. Since nothing need be placed within the mouth except a small bite-tab, the patient experiences lit tle discomfort. Five to ten minutes usually is ample time for an operator to load the film carrier, instruct the patient, ad just the machine and complete the ex posure. The cost of each film amounts to about that of four or five intraoral films, and it can be processed as quickly as can a single film of any type. RADIATION DOSAGE
Hudson and Kumpula7 measured radia tion dose rates of the prototype apparatus from which the Panorex was developed. Using 10 ma. of current at 65 kvp., they recorded a rate of delivery in air of about 558 milliroentgens per second at 12 inches from the target of the x-ray tube. When the machine was operated for a 25 second exposure cycle, the highest level recorded at any of ten locations in a phantom head was 0.42 R , in the cervical lymphatic re gion. A slightly smaller amount was re corded at the skin of the neck. The high est comparable measurements recorded for a simulated intraoral series of 14 ex posures were 23 R at the skin of the cheek and 27 R in the thyroid gland region. Using a Panorex machine at 70 kvp. and 10 ma., Kraske and Mazzarella6 re ported a delivery rate in air at 12 inches from the target of 228 mr. per second. At the lower ma. and higher kvp. values used for the study now under discussion (about 5 ma. at 85 kvp.), an output of well below 200 mr. per second is esti mated. At a rate of 200 mr. per second, each cycle of 35 seconds exposure would deliver 7 R, as compared with 13.95 R delivered for its 25 second cycle by the prototype machine at 558 mr. per second. Thus it is estimated that levels of patient radiation dosage applicable to this study would be less than half the levels meas ured for the prototype machine. On the basis of the foregoing, it is estimated that the highest level of radia tion at the skin for each Panorex exposure
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as made in this study would not exceed 0.21 R. This is less than the estimated dose to the patient’ s skin resulting from a single intraoral exposure, using ultra speed film. The total area of skin surface exposed at any one time during the Panorex cycle is estimated as less than one square inch, whereas each intraoral ex posure covers about six square inches, as suming collimation of the beam to a circle 2.75 inches in diameter. Since this study was made, a new Royal Blue film has become available. Use of this film, having an emulsion “ speed” about one third faster, permits a corre sponding reduction in radiation dosage, and also results in roentgenograms show ing more contrast. Measurements were made for scattered radiation at the operator’s position, using a Tracerlab Model SU IH Survey Meter. Radiation intensity was found to vary at this position as the tube head moved. The total dose per complete cycle was estimated to be about 0.37 milliroentgens without a protective shield and 0.01 milli
roentgens per film behind the leaded screen which was used always in actual practice. PLAN OF T H IS STUD Y
After routine operating procedures were developed, “ Panorex” exposures were made for clinic patients chosen more or less at random from different age groups and categories. From the first 200 thus produced, 100 run-of-the-mill films were chosen for in tensive study and evaluation. To get a broad consensus of their practical value, they were divided into ten groups, and each group of ten films was submitted to two different dentists for objective evalu ation. The reviewers were asked to mark individual score sheets as illustrated in Table 1. The films selected for review varied a great deal in quality, but all appeared to have some diagnostic value. As a group they were considered fairly representative of the quality of films which could be
Table 1 • Evaluation sheet for Panorex film General film quality Detail (Confrast and definition) Excellent Satisfactory Unsatisfactory
As compared with Intraoral Extraoral (I) (2) (3)
Coverage of areas of diagnostic interest Superior (4) Adequate (5) Inadequate (6) Accuracy of anatomic relationships Anterior dental regions Satisfactory (7) Distorted or overlapped (8) Posterior dental regions Satisfactory (9) Distorted or overlapped (101 General opinion as to diagnostic value of this film: Adequate for initial examination and basic treatment planning Adequate for (11)if posterior brewings are available Adequate for (11)if intraoral anterior films available Adequate for (11)only if both (12) and (13) Adequate for oral surgery diagnosis and treatment Adequate for prosthodontic treatment planning Supplemental diagnostic value for oral surgery Supplemental diagnostic value for prosthodontics Remarks:
(11) (12) (13) (14) (15) (16) (17) (18)
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Table 2 • Tabulation of 200 evaluations of Panorex films as compared with intraoral films General film quality (1) Excellent (2) Satisfactory (3) Unsatisfactory Coverage (4) Superior (5) Adequate (6) Inadequate
Totals 31 105 64
Per cent (of 200) 15.5 52.5 32
82 92 26
41 46 13
Accuracy of relationships Anterior regions: (7) Satisfactory (8) Distorted or overlapped
118 82
59 41
Posterior Regions: (91 Satisfactory (10) Distorted or overlapped
156 44
78 22
produced consistently. They were classi fied according to subjects as follows: (A ) Adults with nearly all teeth 16 (B) Edentulous or semi-edentulous 34 (C) Children— mixed dentition 36 (D ) Patients of special surgical interest 14 Intraoral views were available to ac company 44 of these films; for the others the intraoral films remained with active clinic records of patients undergoing treat ment. Other extraoral films were not fur nished for direct comparison in any of these cases. The dentists who participated are members of the faculty of the Medical College of Virginia (15 full-time and 5
part-time). Their fields of interest are as follows: General (including diagnosis, restora tive dentistry, and pedodontics) 13 Denture prosthesis 3 Orthodontics 2 Oral surgery 2 The films were distributed to reviewers without regard to their specialties or pre vious familiarity with this type of roent genography. Each group of ten films included all four categories of cases, and several accompanying intraoral series, in approximately equal proportions. The following is quoted from the memoran dum which accompanied each group of films submitted for review: The “ compared with” columns should be considered and used even if only a panorex of the case is enclosed, since it is your opinion of the comparison with conventional projec tions of “ normal” quality which is desired at this time. Therefore, please check all spaces you deem applicable, consistent and logical for the case at hand. By “ basic treatment planning” as used in (11) is meant preliminary decisions as to type and scope of treatment, classification as to urgency, initial assignment and commencement of treatment. (It is assumed in all cases that roentgenographic findings would be related directly to clinical examinations.) Opinions under (11) through (18) should be related to age group and type case. (For example, evidence of caries in an adolescent might be given different diagnostic weight than in a semi-edentulous patient with extensive periodontal involvement.)
Table 3 • Tabulation of 200 opinions of diagnostic value of Panorex films
*(11) *(12) *(13) *(14) (15) (16) (171 (18)
Adequate for initial examination and basic treatment planning Adequate for (11) if posterior bitewings are available Adequate for (11) if intraoral anterior films are available Adequate for (11) only if both (12) and (13) Adequate for oral surgery diagnosis and treatment Adequate for prosthodontic treatment planning Supplemental diagnostic value for oral surgery Supplemental diagnostic value for prosthodontics
Totals
Per cent (of 200)
95 32 12 54 87 64 92 67
47.5 16 6 27 43.5 32 46 33.5
*Where (12) and/or (13) were marked as well as (I I) on individual evaluation sheets, (12) and (13) were not included in the totals shown. ( I I ) + (12) total 127 or 63.5% of 200
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R E S U L T S OF SU R V E Y
Tables 2 and 3 were compiled from tabu lations of the 200 completed evaluation sheets. Table 4 represents only 120 evalu ations, since eight of the participants did not wish to make comparisons with hypo thetical extraoral films and so did not mark the column “as compared with extraoral.” EXPLAN ATION OF TA BLE S
Because of relatively poor definition, it was immediately apparent that Panorex films are of little use in the detection of incipient caries or for detailed study of such fine structures as the lamina dura. Therefore, spaces were not provided in the evaluation sheets (Table 1) for re cording judgments of its specific value for restorative dentistry, endodontics or periodontics. In the section on “General Opinion as to Diagnostic Value,” many of the sheets were marked not only under item (11) but also had markings under one or more of items (1 2 ), (13) and (1 4 ). It was felt that the inclusion of all of these figures in the totals and computations might indi cate more favorable opinions of “ ade quacy” than was intended by some of the reviewers. Therefore, whenever item (11) was marked, any markings of items ( 12), (13) and (14) were not included in the totals. Likewise when either item (12) or (1 3 ), or both, were marked as well as item (1 4 ), the totals include item (14) only. All markings of items (15), (16), (17) and (18) are included in the totals. A N A L Y SIS OF R E S U L T S
After tabulation of the completed evalu ations and compilation of tables, the sheets again were reviewed individually. Informal comparisons were made of scores given by different dentists. These varied widely, even between scores given the same films. A statistical representation of these comparisons, or of the “remarks,”
Table 4 • Tabulation of 120 evaluations of Panorex films as compared with extraoral films General film quality
Totals
Per cent (of 120)
(1) Excellent (21 Safisfactory (3) Unsatisfactory
33 62 25
27.5 51.7 20.8
Coverage (4) Superior (5) Adequate (6) Inadequate
75 42 3
62.5 35 2.5
Accuracy of relationships Anterior regions: (7) Satisfactory (8) Distorted or overlapped
81 39
67.5 32.5
Posterior regions: (9) Satisfactory (10) Distorted or overlapped
96 14
80 20
the tenor of which ranged from “To me this film is of no value whatever” to “This Panorex should satisfy all x-ray requirements for complete diagnosis and treatment planning,” was not attempted. Sample remarks are quoted below: “ Sharpness could be improved— outlines of teeth not clear enough.” “ Most of the maxillary area is hazy— of only gross diagnostic value.” “ Contrast not good, but O K for oral surgery treatment planning.” “ Effect of extensive caries on periapical areas would show up better on intraoral films.” “ Coverage o f areas is of course always good.” “ Excellent film for developmental study.” “ Excellent for picking up impacted molar without full-mouth x-rays. Certainly supple ments intraoral films.” “ This film alone is adequate for oral surgery or prosthodontics; other x-rays not needed.” “ Coverage of entire dentition is far superior to any intraoral film examination of a patient this age. Bitewings would be necessary to study more carefully the extent of caries.” “ The general background of haze in this film tends to make one reluctant to rely upon it for diagnostic value— yet when it is examined closely, one wonders if anything more than posterior bitewings really would be needed.”
There appeared to be no particular correlation of the special fields of review ers and their enthusiasm, or lack of it,
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Fig. 3* Panoramic roentgenogram of nine-year old patient
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for panoramic films. Seeming inconsisten cies may perhaps be explained by assum ing that opinions sometimes were related to long-accepted ideas about the stand ards o f clarity and detail that all good roentgenograms should exhibit, whereas others may have approached the evalua tion more objectively, attempting to judge simply the practical usefulness of the films as presented. The averages as shown in the tables are believed significant and representative of a fair sampling of current conservative opinion. From Table 2, it is seen that the general quality of this group of films was considered unsatisfactory in comparison with intraoral films in less than one third of the opinions, except for the anterior dental regions which were reported as dis torted or overlapped in 41 per cent of the instances. With regard to coverage of areas of diagnostic interest, only 13 per cent were judged inadequate. The score of the Panorex roentgenograms compared with extraoral roentgenograms was considerably higher, as seen in Table 2, which shows that coverage was deemed adequate in 97.5 per cent of the opinions.
Table 3 presents a cross-section of opin ions which probably have more direct bearing on the question of the application' of panoramic roentgenography to dental practice. As pointed out previously, mul tiple scores of items (11) to (14) were corrected before computing the totals. Therefore, the figures shown can be taken as conservative reflections of opinions ex pressed for these categories. Item (11) indicates that 47.5 per cent of the opin ions held that the Panorex film alone would give adequate roentgenographic information for the initial examination and treatment planning. By adding items (11) and (12) it will be seen that in 63.5 per cent of the opinions, the Panorex roentgenogram supplemented by posterior bitewing films was judged adequate. Items (11) and (14) taken together show that in 74.5 per cent of the opinions, the Panorex roentgenogram would suffice if supplemented by intraoral views of an terior teeth and posterior bitewings. Items ( 15) to ( 18) show that from 32 per cent to 46 per cent of the opinions recognized specialized and supplemental value of the Panorex films.
Fig. 4 • Intraoral roentgenograms, same patient as Figure 3
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Fig. 5 • Panoramic roentgenogram of 38 year old patient
D IS C U S S IO N
Direct comparisons demonstrate at once both the typical advantages and disad vantages o f panoramic roentgenograms (Fig. 1-10). Figures 1, 2, 3, 5, 7 and 9 were made from cropped photographs of the 5 inch by 12 inch Panorex films. It will be noted that the midline and central incisors of both sides, when present, can be seen on either side of the blurred central area of the typical Panorex film. This blurred area may be confusing at first glance. It can be eliminated by cutting the film ver tically along the midline on each side, then reassembling the right and left sec tions. This is unnecessary, since with ex perience in viewing the films, immediate
identification of the midline on each side of the blurred area becomes almost au tomatic. (In the illustrations, arrows point to midlines.) Furthermore, having two views of this region projected from different angles is frequently helpful for comparison and orientation (Fig. 7 ). Panoramic roentgenograms have spe cial value for showing the status o f de velopment and eruption of teeth at vari ous ages, as illustrated in Figures 1, 2 and 3. Several extraoral projections would be needed for each of these cases in order to give similar coverage. In Figure 5 the Panorex film can be seen as a useful supplement to the intra oral series shown in Figure 6. In a comparison of Figures 7 and 8, roentgenographic evidence of numerous pathologic conditions can be seen in the Panorex film, even though not as clearly defined as in the intraoral films. Note that two different views are seen o f the un erupted maxillary cuspid. The typical appearance of edentulous areas in the Panorex film is illustrated in Figure 9. The appearance of the remain ing teeth and roots can be compared with Figure 10. Note also the arrows indicating the approximate midline.
Fig. 6 • Intraoral roentgenograms, same patient as Figure 5
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CO M M E N TS
Whereas many are disappointed with the definition and contrast of panoramic roentgenograms, most experienced den tists quickly recognize the intrinsic advan tages offered. The relatively poor detail inherent in roentgenograms produced by this method limits its usefulness to those situations where extreme clarity of detail is not essential. Opinions are likely to differ as to what degree roentgenographic quality should
be sacrificed to expediency. Certainly ex cellent detail is always desirable, even if not an absolute requirement for roent genograms to be useful. Perhaps an ob jective evaluation should be related directly to the kind of information sought from them as well as their technical ex cellence. In view of the inexorable biologic ef fects of ionizing radiations, diagnostic roentgenography is justified only by virtue of the need for and value o f the infor mation which can be deduced from its
Fig. 7 • Panoramic roentgenograms of 21 year old patient
Fig. 8 • Intraoral roentgenograms, same patient as Figure 7
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Fig. 9 • Panoramic roentgenogram of 32 year old patient
results. When appraising a method of roentgenography, then, due consideration must be given not only to the sine qua non aim that it serve its essential purpose, but also to such other factors as radiation dosage, convenience of use, and comfort o f patients. S U M M A R Y A N D C O N C L U S IO N S
Initial experience with panoramic roent genography in a dental school clinic is described. The results of a preliminary opinion survey are presented and an alyzed as a basis for discussing its practi cal value in dentistry. The following conclusions are drawn: 1. Panoramic roentgenography has lit tle value for revealing incipient caries or the finer details of dental and osseous structures. 2. It is a very useful and convenient supplement to intraoral roentgenography.
Fig. 10 • Intraoral roentgenograms of retained teeth seen in Figure 9
3. It has particular value for children; for adolescents when clinical examina tions indicate no defects; for edentulous patients, and wherever extraoral projec tions would be indicated. 4. For the majority of routine dental examinations, its judicious use will pennit considerable reduction in radiation dos age and in the time required for roentgenographic procedures. 5. Further improvements can be pre dicted in the design and operation of equipment of this type. As experience is gained in this field, wider applications are likely to be found, both in diagnosis and in anatomic and clinical investiga tions.
*Professor of oral roentgenology, School of Dentistry, Medical College of Virginia. 1. Nelsen, R.J., and Kumpula, J. W. Panographic radiography. J.D. Res. 31:158 April 1952. 2. Blackman, S. Mass dental radiography. Radiog. 22:21 Feb. 1956. 3. Hudson, D. C.; Kumpula, J. W., and Dickson, G. A. Panoramic X-ray dental machine. U.S. Armed Forces M.J. 8:46 Jan. 1957. 4. Kumpula, J. W . Present status of panoramic roent genography. J.A.D.A. 63:194 Aug. 1961. 5. Paatero, Y. V. Pantomography and orthopantomog raphy. Oral Surg., Oral Med. & Oral Path. 14:947 Aug. 1961. 6. Kraske, L. M., and Mazzarella, M. A. Evaluation of a panoramic dental X-ray machine. D. Progress 1:171 April 1961. 7. Hudson, D. C., and Kumpula, J. W. Ionization chambers for radiation data during dental x-ray expo sure. U.S. Armed Forces M.J. 6:1131 Aug. 1955.
Louis D. Mitchell, Jr.,* D.D.S., Richmond, Va.
For many years there has been virtually universal agreement that roentgenograms are indispensable aids to dental diagnosis and treatment planning. No such una nimity has been reached, however, as to what constitutes “adequate” or “com plete” roentgenographic coverage. Many dentists would insist that 18 to 24 films are needed for the adult patient. But even among those who consider 10 to 14 intraoral films sufficient for the usual full-mouth series, it is doubtful that there are many dentists (if any patients at all) who have not wished, frequently and devoutly, for a quicker and more comfortable way— some sort of “oneshot” or “instant” method— for making dental roentgenograms. Unfortunately, as yet no royal road to roentgenography is quite ready for regu lar travel. It is possible, however, with the “panoramic” equipment available, to produce a useful roentgenogram of the dental structures on a single film. This can be done in a fraction of the time required for a conventional full-mouth series. How useful will these films be? What place will this method have in practice? Although categorical answers to such questions would be premature, the pur pose of this paper is to suggest some tentative answers, based on use of “Panorex” equipment in the Medical College of Virginia School of Dentistry.
BACKGROUND
Several separate but essentially similar methods have been developed for apply ing the principles of what is generally called “body-section roentgenography” to the dental structures, producing images of the entire maxilla and mandible on one film. These methods are analogous to a group of technics used in medical roentgenography described variously by such terms as “tomography,” “planigra phy,” “laminagraphy,” and so forth. They produce visible images of structures in selected planes (or, more precisely, in layers or sections). This is done by caus ing the shadows of structures outside the selected plane or section to be so blurred as to leave clearly recorded on the film only the image of the area “in focus.” The principles on which these methods are based and the development of equip ment for applying them to dental use have been described in detail by Nelsen and Kumpula1; by Blackman of Eng land2; and by Hudson, Kumpula and Dickson.3 The latter, working together at the National Bureau of Standards, pro duced the prototype apparatus which led to the development of the machine now marketed under the trade name “ Panorex.” Kumpula4 has recently reviewed the subject from the historical standpoint, discussing the present status of panoramic
46/778 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
roentgenography, as has Paatero,5 who uses the term “pantomography” to de scribe the system which he has been active in developing. Both have described tech nical differences and have drawn com parisons between various devices which have been used. Kraske and Mazzarella6 have reported an evaluation of panoramic dental equip ment ( “Panorex” ) as used by the United States Navy at Great Lakes, 111. Their study was- concerned with the value of the method in forensic identification and dental records for the armed services as well as its uses in dentistry for naval per sonnel. TE C H N IC A L CONSIDERATIONS
Mechanical features of several variations of panoramic roentgenographic equip ment have been described in detail by others.3'5 The machine used for this study is the Panorex, of the “double-eccentric” type, equipped with a 90 K V P x-ray tube having a focal spot of 0.8 mm. The target-film distance is about 17 inches, and the machine’s exposure cycle is about 35 seconds. The target-skin distance var ied for patients of different size, and at different times in the cycle of rotation, from about 7.5 to about 13 inches. The machine exhibited operating characteris tics essentially similar to those reported by Kraske and Mazzarella.6 Eastman Kodak Royal Blue film was used in 5 inch by 12 inch cassettes fitted with Dupont “detail” intensifying screens. Kilovoltage peak and milliamperage val ues were varied according to age and size of patients, with 5 ma. at 85 kvp. as the usual setting for adults of average size. Standardized time-temperature darkroom procedures were maintained in processing the films. A fair degree of proficiency in operat ing the Panorex was acquired easily and quickly. Despite minor difficulties in ad justing the apparatus to accommodate patients with large heads, necks and shoulders, it can be operated with less trouble than often is encountered in posi
tioning intraoral films. Since nothing need be placed within the mouth except a small bite-tab, the patient experiences lit tle discomfort. Five to ten minutes usually is ample time for an operator to load the film carrier, instruct the patient, ad just the machine and complete the ex posure. The cost of each film amounts to about that of four or five intraoral films, and it can be processed as quickly as can a single film of any type. RADIATION DOSAGE
Hudson and Kumpula7 measured radia tion dose rates of the prototype apparatus from which the Panorex was developed. Using 10 ma. of current at 65 kvp., they recorded a rate of delivery in air of about 558 milliroentgens per second at 12 inches from the target of the x-ray tube. When the machine was operated for a 25 second exposure cycle, the highest level recorded at any of ten locations in a phantom head was 0.42 R , in the cervical lymphatic re gion. A slightly smaller amount was re corded at the skin of the neck. The high est comparable measurements recorded for a simulated intraoral series of 14 ex posures were 23 R at the skin of the cheek and 27 R in the thyroid gland region. Using a Panorex machine at 70 kvp. and 10 ma., Kraske and Mazzarella6 re ported a delivery rate in air at 12 inches from the target of 228 mr. per second. At the lower ma. and higher kvp. values used for the study now under discussion (about 5 ma. at 85 kvp.), an output of well below 200 mr. per second is esti mated. At a rate of 200 mr. per second, each cycle of 35 seconds exposure would deliver 7 R, as compared with 13.95 R delivered for its 25 second cycle by the prototype machine at 558 mr. per second. Thus it is estimated that levels of patient radiation dosage applicable to this study would be less than half the levels meas ured for the prototype machine. On the basis of the foregoing, it is estimated that the highest level of radia tion at the skin for each Panorex exposure
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as made in this study would not exceed 0.21 R. This is less than the estimated dose to the patient’ s skin resulting from a single intraoral exposure, using ultra speed film. The total area of skin surface exposed at any one time during the Panorex cycle is estimated as less than one square inch, whereas each intraoral ex posure covers about six square inches, as suming collimation of the beam to a circle 2.75 inches in diameter. Since this study was made, a new Royal Blue film has become available. Use of this film, having an emulsion “ speed” about one third faster, permits a corre sponding reduction in radiation dosage, and also results in roentgenograms show ing more contrast. Measurements were made for scattered radiation at the operator’s position, using a Tracerlab Model SU IH Survey Meter. Radiation intensity was found to vary at this position as the tube head moved. The total dose per complete cycle was estimated to be about 0.37 milliroentgens without a protective shield and 0.01 milli
roentgens per film behind the leaded screen which was used always in actual practice. PLAN OF T H IS STUD Y
After routine operating procedures were developed, “ Panorex” exposures were made for clinic patients chosen more or less at random from different age groups and categories. From the first 200 thus produced, 100 run-of-the-mill films were chosen for in tensive study and evaluation. To get a broad consensus of their practical value, they were divided into ten groups, and each group of ten films was submitted to two different dentists for objective evalu ation. The reviewers were asked to mark individual score sheets as illustrated in Table 1. The films selected for review varied a great deal in quality, but all appeared to have some diagnostic value. As a group they were considered fairly representative of the quality of films which could be
Table 1 • Evaluation sheet for Panorex film General film quality Detail (Confrast and definition) Excellent Satisfactory Unsatisfactory
As compared with Intraoral Extraoral (I) (2) (3)
Coverage of areas of diagnostic interest Superior (4) Adequate (5) Inadequate (6) Accuracy of anatomic relationships Anterior dental regions Satisfactory (7) Distorted or overlapped (8) Posterior dental regions Satisfactory (9) Distorted or overlapped (101 General opinion as to diagnostic value of this film: Adequate for initial examination and basic treatment planning Adequate for (11)if posterior brewings are available Adequate for (11)if intraoral anterior films available Adequate for (11)only if both (12) and (13) Adequate for oral surgery diagnosis and treatment Adequate for prosthodontic treatment planning Supplemental diagnostic value for oral surgery Supplemental diagnostic value for prosthodontics Remarks:
(11) (12) (13) (14) (15) (16) (17) (18)
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Table 2 • Tabulation of 200 evaluations of Panorex films as compared with intraoral films General film quality (1) Excellent (2) Satisfactory (3) Unsatisfactory Coverage (4) Superior (5) Adequate (6) Inadequate
Totals 31 105 64
Per cent (of 200) 15.5 52.5 32
82 92 26
41 46 13
Accuracy of relationships Anterior regions: (7) Satisfactory (8) Distorted or overlapped
118 82
59 41
Posterior Regions: (91 Satisfactory (10) Distorted or overlapped
156 44
78 22
produced consistently. They were classi fied according to subjects as follows: (A ) Adults with nearly all teeth 16 (B) Edentulous or semi-edentulous 34 (C) Children— mixed dentition 36 (D ) Patients of special surgical interest 14 Intraoral views were available to ac company 44 of these films; for the others the intraoral films remained with active clinic records of patients undergoing treat ment. Other extraoral films were not fur nished for direct comparison in any of these cases. The dentists who participated are members of the faculty of the Medical College of Virginia (15 full-time and 5
part-time). Their fields of interest are as follows: General (including diagnosis, restora tive dentistry, and pedodontics) 13 Denture prosthesis 3 Orthodontics 2 Oral surgery 2 The films were distributed to reviewers without regard to their specialties or pre vious familiarity with this type of roent genography. Each group of ten films included all four categories of cases, and several accompanying intraoral series, in approximately equal proportions. The following is quoted from the memoran dum which accompanied each group of films submitted for review: The “ compared with” columns should be considered and used even if only a panorex of the case is enclosed, since it is your opinion of the comparison with conventional projec tions of “ normal” quality which is desired at this time. Therefore, please check all spaces you deem applicable, consistent and logical for the case at hand. By “ basic treatment planning” as used in (11) is meant preliminary decisions as to type and scope of treatment, classification as to urgency, initial assignment and commencement of treatment. (It is assumed in all cases that roentgenographic findings would be related directly to clinical examinations.) Opinions under (11) through (18) should be related to age group and type case. (For example, evidence of caries in an adolescent might be given different diagnostic weight than in a semi-edentulous patient with extensive periodontal involvement.)
Table 3 • Tabulation of 200 opinions of diagnostic value of Panorex films
*(11) *(12) *(13) *(14) (15) (16) (171 (18)
Adequate for initial examination and basic treatment planning Adequate for (11) if posterior bitewings are available Adequate for (11) if intraoral anterior films are available Adequate for (11) only if both (12) and (13) Adequate for oral surgery diagnosis and treatment Adequate for prosthodontic treatment planning Supplemental diagnostic value for oral surgery Supplemental diagnostic value for prosthodontics
Totals
Per cent (of 200)
95 32 12 54 87 64 92 67
47.5 16 6 27 43.5 32 46 33.5
*Where (12) and/or (13) were marked as well as (I I) on individual evaluation sheets, (12) and (13) were not included in the totals shown. ( I I ) + (12) total 127 or 63.5% of 200
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R E S U L T S OF SU R V E Y
Tables 2 and 3 were compiled from tabu lations of the 200 completed evaluation sheets. Table 4 represents only 120 evalu ations, since eight of the participants did not wish to make comparisons with hypo thetical extraoral films and so did not mark the column “as compared with extraoral.” EXPLAN ATION OF TA BLE S
Because of relatively poor definition, it was immediately apparent that Panorex films are of little use in the detection of incipient caries or for detailed study of such fine structures as the lamina dura. Therefore, spaces were not provided in the evaluation sheets (Table 1) for re cording judgments of its specific value for restorative dentistry, endodontics or periodontics. In the section on “General Opinion as to Diagnostic Value,” many of the sheets were marked not only under item (11) but also had markings under one or more of items (1 2 ), (13) and (1 4 ). It was felt that the inclusion of all of these figures in the totals and computations might indi cate more favorable opinions of “ ade quacy” than was intended by some of the reviewers. Therefore, whenever item (11) was marked, any markings of items ( 12), (13) and (14) were not included in the totals. Likewise when either item (12) or (1 3 ), or both, were marked as well as item (1 4 ), the totals include item (14) only. All markings of items (15), (16), (17) and (18) are included in the totals. A N A L Y SIS OF R E S U L T S
After tabulation of the completed evalu ations and compilation of tables, the sheets again were reviewed individually. Informal comparisons were made of scores given by different dentists. These varied widely, even between scores given the same films. A statistical representation of these comparisons, or of the “remarks,”
Table 4 • Tabulation of 120 evaluations of Panorex films as compared with extraoral films General film quality
Totals
Per cent (of 120)
(1) Excellent (21 Safisfactory (3) Unsatisfactory
33 62 25
27.5 51.7 20.8
Coverage (4) Superior (5) Adequate (6) Inadequate
75 42 3
62.5 35 2.5
Accuracy of relationships Anterior regions: (7) Satisfactory (8) Distorted or overlapped
81 39
67.5 32.5
Posterior regions: (9) Satisfactory (10) Distorted or overlapped
96 14
80 20
the tenor of which ranged from “To me this film is of no value whatever” to “This Panorex should satisfy all x-ray requirements for complete diagnosis and treatment planning,” was not attempted. Sample remarks are quoted below: “ Sharpness could be improved— outlines of teeth not clear enough.” “ Most of the maxillary area is hazy— of only gross diagnostic value.” “ Contrast not good, but O K for oral surgery treatment planning.” “ Effect of extensive caries on periapical areas would show up better on intraoral films.” “ Coverage o f areas is of course always good.” “ Excellent film for developmental study.” “ Excellent for picking up impacted molar without full-mouth x-rays. Certainly supple ments intraoral films.” “ This film alone is adequate for oral surgery or prosthodontics; other x-rays not needed.” “ Coverage of entire dentition is far superior to any intraoral film examination of a patient this age. Bitewings would be necessary to study more carefully the extent of caries.” “ The general background of haze in this film tends to make one reluctant to rely upon it for diagnostic value— yet when it is examined closely, one wonders if anything more than posterior bitewings really would be needed.”
There appeared to be no particular correlation of the special fields of review ers and their enthusiasm, or lack of it,
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Fig. 3* Panoramic roentgenogram of nine-year old patient
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for panoramic films. Seeming inconsisten cies may perhaps be explained by assum ing that opinions sometimes were related to long-accepted ideas about the stand ards o f clarity and detail that all good roentgenograms should exhibit, whereas others may have approached the evalua tion more objectively, attempting to judge simply the practical usefulness of the films as presented. The averages as shown in the tables are believed significant and representative of a fair sampling of current conservative opinion. From Table 2, it is seen that the general quality of this group of films was considered unsatisfactory in comparison with intraoral films in less than one third of the opinions, except for the anterior dental regions which were reported as dis torted or overlapped in 41 per cent of the instances. With regard to coverage of areas of diagnostic interest, only 13 per cent were judged inadequate. The score of the Panorex roentgenograms compared with extraoral roentgenograms was considerably higher, as seen in Table 2, which shows that coverage was deemed adequate in 97.5 per cent of the opinions.
Table 3 presents a cross-section of opin ions which probably have more direct bearing on the question of the application' of panoramic roentgenography to dental practice. As pointed out previously, mul tiple scores of items (11) to (14) were corrected before computing the totals. Therefore, the figures shown can be taken as conservative reflections of opinions ex pressed for these categories. Item (11) indicates that 47.5 per cent of the opin ions held that the Panorex film alone would give adequate roentgenographic information for the initial examination and treatment planning. By adding items (11) and (12) it will be seen that in 63.5 per cent of the opinions, the Panorex roentgenogram supplemented by posterior bitewing films was judged adequate. Items (11) and (14) taken together show that in 74.5 per cent of the opinions, the Panorex roentgenogram would suffice if supplemented by intraoral views of an terior teeth and posterior bitewings. Items ( 15) to ( 18) show that from 32 per cent to 46 per cent of the opinions recognized specialized and supplemental value of the Panorex films.
Fig. 4 • Intraoral roentgenograms, same patient as Figure 3
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Fig. 5 • Panoramic roentgenogram of 38 year old patient
D IS C U S S IO N
Direct comparisons demonstrate at once both the typical advantages and disad vantages o f panoramic roentgenograms (Fig. 1-10). Figures 1, 2, 3, 5, 7 and 9 were made from cropped photographs of the 5 inch by 12 inch Panorex films. It will be noted that the midline and central incisors of both sides, when present, can be seen on either side of the blurred central area of the typical Panorex film. This blurred area may be confusing at first glance. It can be eliminated by cutting the film ver tically along the midline on each side, then reassembling the right and left sec tions. This is unnecessary, since with ex perience in viewing the films, immediate
identification of the midline on each side of the blurred area becomes almost au tomatic. (In the illustrations, arrows point to midlines.) Furthermore, having two views of this region projected from different angles is frequently helpful for comparison and orientation (Fig. 7 ). Panoramic roentgenograms have spe cial value for showing the status o f de velopment and eruption of teeth at vari ous ages, as illustrated in Figures 1, 2 and 3. Several extraoral projections would be needed for each of these cases in order to give similar coverage. In Figure 5 the Panorex film can be seen as a useful supplement to the intra oral series shown in Figure 6. In a comparison of Figures 7 and 8, roentgenographic evidence of numerous pathologic conditions can be seen in the Panorex film, even though not as clearly defined as in the intraoral films. Note that two different views are seen o f the un erupted maxillary cuspid. The typical appearance of edentulous areas in the Panorex film is illustrated in Figure 9. The appearance of the remain ing teeth and roots can be compared with Figure 10. Note also the arrows indicating the approximate midline.
Fig. 6 • Intraoral roentgenograms, same patient as Figure 5
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CO M M E N TS
Whereas many are disappointed with the definition and contrast of panoramic roentgenograms, most experienced den tists quickly recognize the intrinsic advan tages offered. The relatively poor detail inherent in roentgenograms produced by this method limits its usefulness to those situations where extreme clarity of detail is not essential. Opinions are likely to differ as to what degree roentgenographic quality should
be sacrificed to expediency. Certainly ex cellent detail is always desirable, even if not an absolute requirement for roent genograms to be useful. Perhaps an ob jective evaluation should be related directly to the kind of information sought from them as well as their technical ex cellence. In view of the inexorable biologic ef fects of ionizing radiations, diagnostic roentgenography is justified only by virtue of the need for and value o f the infor mation which can be deduced from its
Fig. 7 • Panoramic roentgenograms of 21 year old patient
Fig. 8 • Intraoral roentgenograms, same patient as Figure 7
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Fig. 9 • Panoramic roentgenogram of 32 year old patient
results. When appraising a method of roentgenography, then, due consideration must be given not only to the sine qua non aim that it serve its essential purpose, but also to such other factors as radiation dosage, convenience of use, and comfort o f patients. S U M M A R Y A N D C O N C L U S IO N S
Initial experience with panoramic roent genography in a dental school clinic is described. The results of a preliminary opinion survey are presented and an alyzed as a basis for discussing its practi cal value in dentistry. The following conclusions are drawn: 1. Panoramic roentgenography has lit tle value for revealing incipient caries or the finer details of dental and osseous structures. 2. It is a very useful and convenient supplement to intraoral roentgenography.
Fig. 10 • Intraoral roentgenograms of retained teeth seen in Figure 9
3. It has particular value for children; for adolescents when clinical examina tions indicate no defects; for edentulous patients, and wherever extraoral projec tions would be indicated. 4. For the majority of routine dental examinations, its judicious use will pennit considerable reduction in radiation dos age and in the time required for roentgenographic procedures. 5. Further improvements can be pre dicted in the design and operation of equipment of this type. As experience is gained in this field, wider applications are likely to be found, both in diagnosis and in anatomic and clinical investiga tions.
*Professor of oral roentgenology, School of Dentistry, Medical College of Virginia. 1. Nelsen, R.J., and Kumpula, J. W. Panographic radiography. J.D. Res. 31:158 April 1952. 2. Blackman, S. Mass dental radiography. Radiog. 22:21 Feb. 1956. 3. Hudson, D. C.; Kumpula, J. W., and Dickson, G. A. Panoramic X-ray dental machine. U.S. Armed Forces M.J. 8:46 Jan. 1957. 4. Kumpula, J. W . Present status of panoramic roent genography. J.A.D.A. 63:194 Aug. 1961. 5. Paatero, Y. V. Pantomography and orthopantomog raphy. Oral Surg., Oral Med. & Oral Path. 14:947 Aug. 1961. 6. Kraske, L. M., and Mazzarella, M. A. Evaluation of a panoramic dental X-ray machine. D. Progress 1:171 April 1961. 7. Hudson, D. C., and Kumpula, J. W. Ionization chambers for radiation data during dental x-ray expo sure. U.S. Armed Forces M.J. 6:1131 Aug. 1955.