Radiology

Vol. 81 No. 6

ORAL AND MAXILLOFACIAL RADIOLOGY

June 1996

Editor: Sharon L. Brooks

Radiology Closing a century, opening a millennium S. Julian Gibbs, DDS, PhD, Nashville, Tenn. DEPARTMENT OF RADIOLOGY AND RADIOLOGICAL SCIENCES, VANDERBILT UNIVERSITY

As we close the file on the first century of radiology, we honor the pioneers and reflect on the progress they started. We also open a new file, not just a new century, but a n e w millennium of opportunity. The dramatic technologic advances in diagnostic imaging within recent decades have provided the foundation for expanding our activities in Oral and Maxillofacial Radiology. We are no longer just dental radiology; we can no longer rest on the teaching and practice of conventional dental radiography. We can summarize in one word the direction our efforts must take in opening the millennium: research. Only with research at the fundamental as well as clinical level can we continue to expand our service to the public, to our patients, and to our colleagues. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod

1996;81:603-6)

" I f you don't know where you're going, you'll wind up somewhere else." Yogi Berra Any time is a good time to pause and reflect on where we are and where we are going and to honor those who got us here. In this Centennial Year, it is especially appropriate to pay tribute to our pioneers. Allow me to remind you of a few, some you know quite well, some only by name, and some not at all. Wilhelm ConradRgntgen. Known to all of us as the discoverer of x-ray, we honor h i m with this Centennial Year. But did you know that he published a total of 58 papers, but only three were on the subject of the x-ray? 1-3 And that in those three papers he covered the subject so thoroughly that nothing of substance was added in the succeeding 10 years? 4' 5 And that in his will he ordered that all his laboratory notes and scientific papers be burned? As a result, the only remaining original ROntgen document is the first page of his handwritten note about the discovery of x-ray. William Dudley, MD. Dr. Dudley is known to only a few as Dean of the Vanderbilt Medical School at the time of R6ntgen's discovery, as a member of the Hartman Centennial Lecture and H. Cline Fixott Memorial Lecture; presented at the American Academy of Oral and Maxillofacial Radiology meeting in Chicago, Nov. 30, 1995. Copyright 9 1996 by Mosby-Yeas Book, Inc. 1079-2104/96/$5.00 + 0 7/16/71654

committee that formed the National Collegiate Athletic Association, and as the person for w h o m the football stadium on the Vanderbilt campus is named. He also was the first reported victim of biologic injury from a diagnostic x-ray. Professor John Daniel of the Physics Department at Vanderbilt, on reading R6ntgen's first paper, quickly assembled equipment duplicating R6ntgen's laboratory; his first exposure of a human subject, on February 29, 1896, was a lateral skull radiograph with Dean Dudley as his willing volunteer. He placed the unshielded Hittorf gas discharge tube as close as possible to one side of Dean Dudley's head with the plate taped to the opposite side. The exposure was 1 hour. The plate bore only faint traces of an image, but 3 weeks later Dean Dudley began to epilate on the tube side. 6 It is now known that the dose required to produce temporary epilation is at least a few Gy. John Dally. Mr. Dalley was Thomas Edison's laboratory associate; he was among the first to get radiation dermatitis from frequent exposure of his hands beginning in early 1896. The dermatitis progressed to carcinoma, which required amputation of his hands and subsequently his arms. He died from disseminated metastatic disease in 1904, the first American martyr to R6ntgen's rays. 7 Edmund Kells. Dr. Kells is well known to all in oral and maxillofacial radiology for his implementation

603

604

Gibbs

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY

May 1996

0.3 tO

:~

0.2

e..

~" 0.1 0

10

20

30

40

50

60

70

80

Photon energy (kev) Fig. 1. Interaction of diagnostic x-ray beam with direct exposure film that typically contains approximately 1 g/m2 of silver, generally as silver bromide, per emulsion layer; intraoral film is coated on both sides with emulsion. At typical diagnostic energies, only about 5% of photons are attenuated by emulsion and some 95% of the beam traverses the film without interaction or contribution to the image.

of R6ntgen's rays in American dentistry in the spring of 1896. But how many recall that he noted radiation-induced cancer on his left hand in 1914 that required more than 40 operations including amputation of the arm? Unable to continue, he took his life in 1928. 8 Howard Raper. This is a name most familiar to those of us in academic dentistry as the first dental radiology educator; he was at Indiana University. But did you know that he was the first treasurer of the Western Roentgen Society, Organized in Chicago on December 15, 1915? 9 The society changed its name in 1919 to the Radiological Society of North America. William Rollins. This Boston dentist and prolific early contributor published 183 short papers between 1896 and 1904 on what he called "X-Light. ''1~ His topics ranged from tube design to acute radiation lethality in rodents. Some of his ideas were " o f f the wall," such as his combined fluoroscopic screen and stethoscope that he called a "Seehear." Other ideas were best left undeveloped, such as his recommendation that radioactive materials be stocked in pharmacies to be dispensed on prescription to patients for treatment of cancer. However, his recommended principles, which he called axioms, remain pertinent, such as " . . . The source should be in a non-radiable tube box from which no X-light can escape except the smallest beam which will serve the purpose . . . . In using X-light it should not strike the observer . . . . Selective filters should be employed to strain out undesirable radiations . . . . The central r a y . . , should strike the photographic plate normal to its surface."l~

For his astute observations and conclusions he has been called the ' 'Father of radiation protection." But he remains obscure in dental circles. The list of contributors to our discipline could continue endlessly. One more, however, must be included: H. Cline Fixott is remembered by most of us as the prime mover in the establishment of what is now known as the American Academy of Oral and Maxillofacial Radiology in 1949. He was also its first President. The first 50 years of the x-ray age saw the promotion of radiation as the "silver bullet" for the diagnosis and treatment of nearly all human disease. Radiography was immediately recognized and implemented on a broad scale in the practice of dentistry and medicine. Radiation was also perceived very early as effective in the treatment of cancer, and its potential was realized as quickly as that of radiography. It was also used for treatment of a variety of benign diseases including gingivitis. 12The development of the cyclotron, o r " a t o m smasher," in the late 1930s made artificial radioisotopes available; scientists, in their unbridled enthusiasm, predicted the production ofradiopharmaceuticals specific for the diagnosis and treatment of a variety of cancers and numerous other diseases. Although accomplishments were numerous, there were also quite a few missteps. There were a few warnings, but the possibility of adverse effects was largely ignored. Low-energy grenz rays became accepted treatment for benign dermatologic conditions. Dilute solutions of radioisotopes were sold directly to the public. Mobile chest x-ray units became widely available to anyone who walked in from the street in the name of early detection of one of the major diseases of the time, tuberculosis. Many of these machines were parked in affluent neighborhoods designed to attract contributions to the agencies supporting the effort, rather than in poorer areas where undiagnosed tuberculosis was prevalent. Fluoroscopes were common in shoe stores for checking the fit of children's shoes while delivering substantial doses to essentially the total body of each young subject. X-ray machines became standard equipment in both physicians' and dentists' offices. These machines produced beams that were uncollimated and unfiltered, delivering large doses that frequently approached whole-body, to produce images with the slow films and screens of the era. The advent of the atomic age, beginning with nuclear weapons at the close of World War II, began to direct attention to the devastating biologic effects of radiation. Statistically valid evidence of genetic effects in drosophila had been available since the 1920s 13 However, it was not until excess leukemia appeared in Japanese atomic bomb survivors 14 and

Gibbs

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY

60.$

Volume 81, Number 5

the " m e g a m o u s e studies" of genetic effects in rodents 15 were published, all in the 1950s, that the public health risk of radiation was recognized. The news that the x-ray could indeed produce harmful biologic effects in the public was met with inertia totally uncharacteristic of the enthusiasm with which this new diagnostic modality had been embraced. It was a full decade before even simple, cost-free modifications came into widespread use in dental radiography: round collimators producing 7.5-cm diameter beams at skin entry, aluminum filters to reduce dose to skin and superficial tissues, ANSI Speed Group D film, and lead aprons. The second half of the first century of the x-ray, starting with the movement toward safe radiation practices started in the 1960s, has produced numerous significant accomplishments. The uncollimated, unfiltered x-ray machine rapidly became the exception. 16 Skin exposures for intraoral dental radiographs have dropped from the 1.1 R reported in the mid-60s 17 to reports of less than 0.5 R in the mid-70s 16 and the current state of the art of about 0.1 R. All of these developments occurred as new technologies--panoramic, digital, TMJ, and implant i m a g i n g - - w e r e introduced. New high-tech medical imaging procedures, including nuclear medicine, ultrasound, computed tomography, and magnetic resonance imaging, were added to the toolkit of the oral and maxillofacial radiologist. Oral and maxillofacial radiology now stands at the proverbial threshold of not just a new century but a new millennium of opportunity. There seems to be a consensus that a major impediment is the absence of recognition as a specialty by organized dentistry; numerous committees have deliberated, practitioners of the discipline have been enumerated, accomplishments cited, and petitions flied with appropriate bodies, all in a futile--to date---effort to achieve this recognition. These efforts must continue. However, the secret of success can be given in one so-far overlooked word: RESEARCH. All of us must contribute. We must overwhelm the editors of our journals with quality manuscripts. A new journal could be a desirable outcome. It is not required that all of us perform bench research of a caliber that would provide for Nobel nomination. Imaging research can follow a number of tracks that range from development of technology to its implementation in everyday practice. A wealth of new information, all of benefit to our professional colleagues, would gain us notoriety, followed by unavoidable recognition. A few examples of lines of research waiting to be exploited are in order. These range from technology and its accessibility to efficiency of both cost and

"6 iO f..) elD

175 150 125 100 75 50 25 0 50

/ I

/

.---5525 ..............................

.... Gd oxysulfide ~- La oxybromide 60

70

80

90

100

110

120

Beam energy (kVp)

Fig. 2. Intensification factor relative to direct exposure film from high-speed calcium tungstate screens is approximately 50, and from medium-speed rare-earth screens approaches 100; that is, these screens with appropriate films can provide diagnostic quality images from exposures of 1% to 2% of those required for direct exposure film. Redrawn from data of Bushberg et al. 22 time, efficacy, algorithms for disease detection, and integration with treatment. Apparatus of proven efficacy for achieving rectangular collimation of the x-ray beam for periapical radiography to approximately the dimensions of the image receptor has been commercially available for more than 25 years, as' 19 Similar apparatus for bitewing radiography is also available, but problems remain with its use. Here two lines of research are wide open: (1) to perfect the technique for bite-wing radiography and (2) to develop a protocol for universal application of the method in dental practice. Intraoral radiographic film of ANSI Speed Group E has been commercially available for more than a decade. With its recent improvements it has been pronounced suitable for essentially all periapical and bite-wing radiography, z~ Yet D-speed film is still used for the overwhelming majority ofintraoral films. An effective strategy for insuring universal use of Espeed film could be an award-winning research project. Full use of rectangular collimation and E-speed film could reduce exposure to patients from dental radiography by a factor of about 10. 21 A serious problem with intraoral imaging remains: directexposure film, even E-speed, is horribly inefficient (Fig. 1), attenuating only about 5% of the x-ray beam. More than 90% of the incident photons traverse the film without interacting, contributing nothing to the image. Medium-speed rare-earth screens (Fig. 2) provide intensification f a c t o r s - - o r exposure reduction f a c t o r s - - o f about 100. zz These screens attenuate about 60% of incident photons. A successful research project could develop an intraoral imaging system, that uses rare-earth screens and film, solid-state detectors, storage phosphors, or devices yet unknown,

606

Gibbs

that would provide exposure reduction factors of more than 100. Imaging of the temporomandibular joint (TMJ) has progressed during m y professional lifetime from transcranial or transpharyngeal views to linear and polydirectional tomography with or without cephalometric correction, arthrography, and tomography, and finally magnetic resonance imaging. Yet we are not even close to consensus on a protocol for imaging the symptomatic TMJ. Further, our orthodontic colleagues find themselves in the courtroom because they were perceived as not considering the possibility o f either asymptomatic TMJ disease preceding their treatment or symptomatic disease caused by their treatment. Many orthodontists are now obtaining pretreatment TMJ images on every patient. We could provide a major service by cooperating with our orthodontist friends in the development of an imaging protocol for the workup of patients for orthodontic treatment. The linear nonthreshold hypothesis relating radiation dose to probability of stochastic effect remains just that: a hypothesis. It is a model that fits most available data, but not to the exclusion of other models. However, when we publish results of dosimetric studies of our diagnostic procedures, estimating the probability of radiation-induced cancer or mutation from dental x-ray, we give undeserved legitimacy to the model. We and most of our colleagues recognize these estimates for what they are. However, the lay public, and even some conscientious scientists, accept them as established scientific fact. We must find a method to express our results that will not mislead the public, even unintentionally. One possibility that has been used successfully is to equate the diagnostic dose to an equivalent interval of natural environmental dose with the effective dose method. 23 There may be other methods, as yet undeveloped, that may be more appropriate. In summary, the first half century of the x-ray era was characterized by enthusiastic acceptance of this new tool for diagnosis and treatment of disease. The second half century saw major efforts to improve radiologic efficiency: increased diagnostic information at minimum patient dose. Our goal as we open a new millennium of opportunity is to achieve recognition of our discipline as a specialty area of dental practice. The secret of success in this effort is in one word: research. Several examples o f avenues open for innovative investigation have been presented. Other areas of high-tech imaging, including such things as monoenergetic photon beams, high-field MRI, real-time MRI, and image-guided treatment, represent other avenues open to those with access to the hardware. All

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY May 1996

of us must increase our productivity in scholarly efforts, resulting in increased visibility of our discipline among our peers, our patients, and the public.

REFERENCES 1. R6ntgen WC. 0ber eine neue Art von Strahlen. Wtirzberg: Sitzgsber physik-med Ges, 1985:135. 2. R6ntgen WC. 0ber eine neue Art von Strahlen. 2. Mitteilung. Wttrzberg: Sitzgsber physik-med Ges, 1896:11. 3. R~Sntgen WC. Weitere Beobacbtungen Ober die Eigenscbaften der X-Strahlen. Math u naturw Mitt a.d. Sitzgsber preuss Akad Wiss Physik-Math KI, 1897:392. 4. Glasser O. Dr. W. C. R~intgen, 2nd ed. Springfield IL: CC Thomas, 1958. 5. Stehr H, Buchholz U. R0ntgen, s rays. J Radiol Prot 1995; 15:187 9. 6. Daniel J. The x-rays. Science NS 1896;3:562-3. 7. Brown P. American martyrs to science through the Roentgen Rays. Springfield IL: CC Thomas, 1936. 8. Jacobsohn PH, Fedran RJ. Making darkness visible: the discovery of x ray and its introduction to dentistry. J A m Dent Assoc 1995;126:1359-67. 9. Radiological Society of North America. 1995 RSNA Membership Directory. Oak Brook IL: Radiological Society of North America, 1995. 10. Rollins W. Notes on X-light. Boston: privately published, 1904. 11. R o l l i n s W. A grouping of some of the axioms mentioned. Elect Rev, Dec. 12, 1903. 12. Pfahler GE. A case of tuberculous gingivitis treated with apparent success by radium. A m J Roentgenol 1922;9:756-7. 13. Muller HJ. Artificial transmutation of the gene. Science 1922;66:311-21. 14. Folley JH, Borges W, Yamawaki T. Incidence of leukemia in survivors of the atomic bomb in Hiroshima and Nagasaki. A m J Med 1952;13:311-21. I5. RusselI LB' RusselI WL" Radiati~ hazards t~ the embry~ and fetus. Radiol 1952;58:369-76. 16. Gibbs S J, Crabtree CL, Johnson ON. Educational approach to improved practices in dental radiology. J A m Dent Assoc 1977;95: 562-70. 17. Gitlin JN, Lawrence PS. Population exposure to x rays in the U.S., 1964. 1966:USPHS Publication 1519. 18. Medwedeff FM, Knox WH, Latimer PA. A new device to reduce patient irradiation and improve dental film quality. Oral Surg Oral Med Oral Pathol 1962;15:1079-8. 19. W e i s s m a n DD, Longhurst GE. Clinical evaluation of a rectangular field collimating device for periapical radiography. J A m Dent Assoc 1971;82:580-2. 20. Conover GL, Hildebolt CF, Anthony D. A comparison of six intra-oral x-ray films. Dentomaxillofac Radiol 1995;24:16972. 21. Gibbs S J, Pujol A Jr, Chen T-S, James A E Jr. Patient risk from intraoral dental radiology. Dentomaxillofac Radiol 1988; 17::15-24. 22. Bushberg JT, Seibert JA, Leidholdt EM Jr, Boone JM. The essential physics of medical imaging. Baltimore: Williams & Wilkins, 1994. 23. International Commission on Radiological Protection. 1990 recommendations of the International C o m m i s s i o n on Radiological Protection. ICRP Publication 60. A n n ICRP 1991:21 ( 1-

3). Reprint requests: S. Julian Gibbs, DDS, PhD Department of Radiology and Radiological Sciences Vanderbilt University Nashville, TN 37232-2675