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BEA M LIN E 25

IN T HE D AYS

following his

discovery of a

new, invisible ray in

N ovember, 1895,

Professor Wilhelm

Con rad Roentgen

experim ent ed doggedly

to t est its properties.

He not ed quickly that

solid objects placed inthe beam between th e

Crookes tu be and the

u orescent screen

serving as an im age

receptor atten uat ed or

blocked th e beam ,

depending upon th eir

density and stru cture.

Medical A pp lications of X Raysby O THA W. L INTON

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A CENTURY OF RADIOLOGY: 18951995

The discovery of the X ray in 1895 was one of the most momentous events in science and medicine, but it was only the beginning of what was to be accomplished in the next 100 years in radiology. What follows are some highlights

provided by American College of Radiology.

1895 German physics professor Wilhelm Conrad Roentgen discov-

ers the X ray on November 8 in his laboratory in Wrzburg. On December 28, Roentgen announces his discovery with a

scientic paper, W. C. Roentgen: About A New Kind of Rays (preliminary communication) , that is widely reprinted.

1896 On January 23, Roentgen delivers his rst lecture about the

X rays. Roentgens discovery launches a urry of experimentation

around the world with the Crookes tubes. Researchers study

what the X rays will do and tinker with rening the design ofthe tubes. Although the shapes and congurations of thetubes change, the basic concept will stay the same until1913.

Fluoroscopy is invented in January by Italian scientist EnricoSalvioni, while American inventor Thomas Edison, an earlyand active X-ray enthusiast, works on a similar device. Theuoroscope is a hand-held or mounted device consisting ofan oblong box, one end of which ts tightly against the eyes,the opposite end of which is a uorescent screen. The basicconcept is still used today.

In March, a Roentgen photograph is introduced as evidencein a Montreal courtroom by a man suing a defendant whoallegedly shot him. The X ray proves the presence of a bullet

not detected by exploratory surgery. Hospitals begin acquiring X-ray equipment to be used by

people with and without medical qualications. One of the rst physicians to specialize in X rays in 1896 is

Dr. Francis Henry Williams of Boston. He is also a graduateof the Massachusetts Institute of Technology, making him oneof the few physicians intimately conversant with the physicsthat create X rays. He is instrumental in early uses of X raysfor medical diagnosis, including the use of uoroscopy tostudy the blood vessels. Later this will be known asangiography.

1898 In December, Marie and Pierre Curie, working in Paris,

discover radium, a new element that emits 200 million timesmore radiation than uranium. In 1903, the Curies andAntoine-Henri Becquerel share the Nobel Prize in Physicsfor their work on radioactivity.

Like the discovery of X rays, the discovery of radium cap-tured the worlds imagination, says Nancy Knight, Ph.D., his-torian and director of the Center for the American History ofRadiology. Scientists knew that the radiation from X rays andradium was similar, but radium was considered the naturalversion of X rays.

Then , in a hear t -s topping m omen t , he chanced topass his hand th rough t he beam. As he looked at thescreen, th e flesh of the h and seem ingly melted away,projecting only the out lines of th e bones. The han d wasintact , un harm ed. But on the screen, only the bonesshowed up. With that observat ion, the science of medical radiology was born.

A few days later, Roentgen m ade a photographic imageof his wifes han d, using th e new rays instead of light forth e exposure. Again, only the bones showed, this tim eon a perm anent record wh ich others could seeand be-lieve.

Th e discovery of a new form of energy that cou ldpenetrate solid objects and record their stru ctu re excitedRoent gens scientific contem poraries. But it w as th eskeletal hand th at captured the im agination of the publicand of physicians, who recognized instant ly that thisdiscovery could change medical practice forever.

A centu ry later, th e vastly more sophisticated arts of m edical im aging are stil l based upon th e recognitionth at body parts absorb a beam of X rays according to theirdensity, producing an im age wh ich allows identicat ionof body struct ures as w ell as the recognition of abnor-m alities reective of injury and disease conditions.

Take a chest X-ray image, for example. T he calciumdensity of the spine and ribs blocks th e m ost X rays,leaving wh ite areas on a film . N o X rays penetrate t oexpose the f i lm and darken those spots . The waterdensities of the stom ach and liver are grayish. They block less of th e X-ray beam th an bon es. Its easy to see th econtrast between t hem . The fat density of m uscles isless than th at of th e water. They look only slight ly dark-er, but th e distinction is there for a trained eye. Final-ly, the air spaces in th e lungs allow penetration of m ost

of the X-ray beam , and look almost black on th e lm s.Allow that th e chest X-ray image looks com plex

because three dimen sions are recorded as two. Muscletissue overlies the ribs, wh ich in tu rn overlie the lungcavities. Th e shapes of blood vessels (wat er densit y) andthe esophagus, which carries food and l iquids to t hestom ach, can be seen. Fractu res of the ribs, abnorm alcurves of th e spine, unusu al heart silhouett es are readilyvisible. Irregular shadows, cau sed by can cers growing inthe lung, may require a sophist icated viewer to pick

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BEA M LIN E 27

up in t he w elter of overlapping shad-ows. Th e pat tern of coal par t ic lesretained in t he lun g field of m inersmay be even more subt le , but isessent ial to a diagnosis of black lung.

IN T H E WEEKS after the firstmedical X-ray images early in1896, scientists and physiciansbegan to im prove on the faint im agesproduced by tubes and generators likethe ones Roentgen used. How theymade improvementsborrowingfrom advances in physics, chem istry,pharm acology, nu clear science, com -puters , te lemetry and informationscienceis the story of a century of m edical radiology.

Th ose ear ly X-ray experiment salso led scient ists to observe that t hepassage of X rays through livingtissue could cause changes. The low-

energy X rays appeared to h ave a goodeffect on m any skin diseases. Opencancers shrank an d the sores driedup. Art hrit is sufferers reported relief from th eir pains . When exposureswere seen to m ake hair fall out , theX ray was tou ted as an end to m ensdaily shaving chores. But just asquickly, workers with X rays notedth at repeated exposures seemed tocause skin inf lamm ations, ulcers,sores, supercial and deeper cancers,

blood abnorm alities, and even death.The quest ion arose: must X-rayworkers inevitably forfeit t heir ownhealth, as some pioneers did, to th epromise of this new science?

The struggles of radiation scien-t is ts to develop radiat ion safetyprotocols, to devise measurements,to learn to con trol X-ray production ,and to exploi t the seeming para-dox th at h igher energies of radiation

The famous radiograph made by Roentgen on December 22, 1895. This is traditionally known as the rst X-ray picture and the radiograph of

Mrs. Roentgens hand. However, it was not actually the rst X-ray pic ture (others exposed photographic plates to X rays previously, without knowing

the images signicance), and was not labeled as Mrs. Roentgens hand when it was rst published.

G e r m a n

M u s e u m ,

M u n

i c h

This much admired rst radiograph of the human brain from 1896 is actually a pan of cat intestines.Since the X ray was so novel to the public, falsied images appeared frequently after Roentgens discovery.

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kill m ore cancer cells wh ile sparingnorm al ones are a lso par ts of thiscentury of remarkable progress.

The earliest X-ray images werem ore useful to surgeons th an to ot herdoctors. Bone fractu res or displace-m ents, gallstones, kidney stones, andbullets or other m etallic fragmentscould be located reliably. With th eimproved tubes and f i lms thatrelaced the original glass plates,doctors began t o see organ sh apes.But they s t i l l could not see i n t oorgans, which had th e same waterdensity inside and out .

Nevertheless , other advancescame qu ickly. In 1896, the inven torThomas Edison devised the fluoro-scope, a calcium tu ngstate coatedscreen w hich glowed when X rays hitit, allowing direct viewin g of any partof the anatom y. In 1913, William D.

Coolidge of the General Electr icLaboratories devised an im proved hotcathode X-ray tube, w hich producedconsistent repeated exposures andwas shielded to prevent t he scatteredradiation th at had harm ed the earlyX-ray u sers. X-rays em erged fromCoolidges tu bes only t hrough anaperture in t he lead shielding. Thepatient could then be placed into t hebeam wh ile oth ers were kept awayfrom it . Additionally, fil ters were

devised to absorb soft, u seless X rays,and a d evice called a grid, placed infront of the film, absorbed m uch of th e X-ray scat t er that could causefuzzy images. Screens sim ilar to th eu oroscope surface were used in lmholders to enhance X-ray images.

And the problem of lookingwith in body structures was finallyaddressed as well. Liquids opaqueto X rays were found that could

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be ingested or oth erwise placed within a patient. Forinstance, bar ium sulfate , a common mineral , couldbe ground u p and swallowed to outline t he esophagus,stom ach, and sm all intestine. Barium sulfate could alsobe inser ted as an enem a to visual ize the large intes-tin e. This practice allowed th e viewing of strictu res,blockages, ulcers, cancers, and oth er defects. But th e de-velopment of other radio-opaque liquids, now called con-trast agent s , wh ich could be used with th e kidneys,the brain an d spinal canal, the circulatory system andthe lungs, took much longer and required far morecomplex solutions.

R OENTGEN S DISCO VERY was art ificial ionizingradiation. Two years later, a French ph ysicist ,Hen ri Becquerel, discovered th at certain rocksem itted natu ral ionizing radiation w ith characteristicsm uch like Roent gens X rays. Becquerels colleaguesPierre and Marie Cu rie ren ed the n aturally radioactiveores to derive uranium , polonium , and radium .

Radium was perceived to have a value in t reat ingcancers, already seen to be responsive to X rays. Marie

Cu ries work produced only t iny am ount s , with oneoun ce of radium being offered for sale at $1 m illion. Th eradium salt (usually radium sulfate) was sealed in hol-low gold or platinum needles and inserted into or againstcancerou s lum ps to deliver cell-killing doses of radia-tion. A decay product of radium , radon gas, was u sedin h ollow glass seeds for insertion in t um ors which couldnot be reached with t he removable needles.

William Coolidge soon im proved his X-ray tu bes todeliver energy levels of 200 kilovolts and more, and asdoctors used radium coupled wit h th e high energy X-raybeams, they noted the seeming paradox that higher

energies killed more cancer cells and spared more n ormaltissue t han lower-energy radiation. Radiobiologists cam eto un derstand th at th e rapid mit osis of cancer cells madeth em m ore susceptible to radiation destruction and lesscapable of regeneration than slower-growing normalcells. But because som e norm al cells were necessarilyradiated in th e process of get t in g the energy to th ecancers , the success of t reatm ent depended upon theability of the radiologist to plan an d deliver a dose th atwould k i l l a ll of the cancer cel ls with out destroyingan un acceptable amoun t of normal cells.

Around the world people believe radium to have marvelousmedicinal properties. It is said to lessen constipation, lowerblood pressure, cure insomnia by soothing the nerves, andincrease sexual activity, and is put in skin creams and tooth-pastes. People ock to radium springs, where the water is

mildly radioactive, a craze that lasts into the 1930s, and useradium drinkers, ceramic vessels made of irradiated earth, atradium cocktail parties, where inside everyones drink is a vialof radium emanationradon gasto make the drinks glowin the dark. Also popular is radium roulette, in which theroulette balls and table are painted with radioactive paint.

1900 German scientists Friedrich Giesel and Friedrich Walkhoff

discover that radium rays are dangerous to the skin; PierreCurie purposely leaves a radium sample on his arm for tenhours and produces a sunburn-like rash. En route to a confer-ence, Henri Becquerel unthinkingly carries a sample in hislower vest pocket and suffers a burn on his abdomen.

Radiology begins to emerge as a medical specialty. Itbecomes increasingly clear that producing an X-ray imagerequires skill and technical know-how, and interpreting theimage requires a knowledge of anatomy.

1901 Roentgen wins the rst Nobel Laureate in Physics prize

for his discovery.

1904 Clarence Dally, Thomas Edisons assistant in X-ray research,

dies of extreme and repeated X-ray exposure. X rays hadalready caused severe burns on his face, hands, and arms,resulting in several amputations. From this point on, the risksposed by radium and X rays become more clear. X-ray usebegins to be conned largely to doctors ofces and hospitals.

1910 Eye goggles and metal shields are commonly used to shield

X-ray users.

1917 During World War I, X-ray equipment is an accepted compo-

nent of aid stations and hospitals in the eld.

1919 Dr. Carlos Heuser, an Argentine radiologist, is the rst to use

a contrast medium in a living human circulatory system. Thecompound, potassium iodide diluted with water, is acceptablebecause it is excreted by the body and causes the blood ves-sels to appear opaque on the X-ray image. Dr. Heuser suc-cessfully injects the compound into a vein of a patients handand simultaneously takes an X ray to visualize the veins inthe forearm and arm. His discovery, however, is lost on thescientic world because it is published only in Spanish, in anArgentine medical journal.

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BEA M LIN E 29

X-ray image of coins made by physicist A.W. Goodspeed and photographer William Jennings in 1896, duplicating one they had made by accident

in Philadelphia in 1890. When the two made the 1890 radiograph, they did not realize its signicance, and the photographic plates lay unnoticed and unremarked

until Roentgens announcement of the X-ray discovery caused them to review the images.

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Opt imal dose levels, t im e inter-vals for treatm ent t o take advantageof the m itot ic cycle , ways of pro-tecting normal parts of the patient,medical care to protect pat ientsagainst in fections, and ot her prod-ucts of whit e blood-cel l radiat iondestruction all began to contributeto im proved radia t ion t rea tment .Even so, surgery rem ained t he firstchoice of treatm ent for many kin dsof cancers, leaving radiation as anadjun ct ive m ethod for destroyingcancer cells not rem oved by surgeryand for trying to control m etastasesfrom advanced cancers.

D U RIN G T H E FIRST fourd ec a de s o f t h i s c en t u r y,m any advances in m edicalradiat ion uses cam e from gradualimprovements in equ ipment and

techn iques. Th e availability of X-raymachines in military hospitals dur-ing World War I convinced manyphysicians of th e u sefuln ess of X-raystudies in detection of som atic prob-lems, as wel l as t rauma. A chestX ray became t he standard met hodof diagnosing tuberculosis. About allthat could be offered the act ivetubercular patient w as nursing care,but isolation of such patients helpedto break the spread of the highly

contagious disease to other familym embers and co-workers. Tubercu-losis was th e target of th e rst X-raypopulation screening efforts.

Th e creation of articial isotopesin t he 1930s by Frdric Joliot andIrene Curie, daughter of Pierre andMarie , opened new dim ensions inradiation science. Soon, ErnestLawrence w as m aking articial iso-topes in the cyclotron of the D onner

Laboratory at th e Un iversity of Cal-ifornia in Berkeley. Lawren ce invit edRobert Ston e, th e chief of radiologyat the Universi ty of Cal i forniaMedical Cent er in San Francisco, tobring cancer patients for treatmentwi th neu t rons p roduced in theDonner lab. Cancers t reated withneut rons m elted away. Soon, so didthe cancer pat ients . N eutrons hadm ore energy and different biologicalcharacter is t ics than high energyX rays. Stone discontinu ed his treat-m ents un t i l the characte r i st i c s o f neut rons could be un derstood better.

World War II arrived, and in qu ick succession Lawrence, Stone, andmost of the leading radiat ionscient is ts in the free world weredrawn into th e Manhat t an projectto develop an atom ic bomb. Wartim eimperat ives dr ive science more

strongly th an peaceful objectives. Butthere was an appreciation with in th eManh at tan project th at biologicalproblems w ere created by th e phys-ical and chemical advances, andafter th e war, th e congress createdthe Atom ic Energy Com m ission tofurther peaceful applications of th enew radiation science.

FOR PHYSICIANS , th ese peace-ful appl icat ions took two

directions. On e was th e devel-opmen t of articial reactor-producedisotopes as h igh energy sources forradiation t reatm ent. Du ring the waryears, th ere had been developm entof Robert van de Graaffs m illion voltstat ic generat ors and Don ald Kerstshigh energy betatron, the f i rs tsupervoltage th erapy mach ines. Butthe s implici ty of using cobal t 60or cesium 137 in rotat ing-head

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19201929 Chest X rays are used to screen for tuberculosisa scourge

of even greater concern to the public than cancer. Exposuresof up to 1 minute, with 10 to 20 rads (units of absorbed radia-tion dose) are used.

Roentgen dies February 10, 1923.

The rst practices of modern angiography are developed in1927 by a Portuguese physician, Dr. Egaz Moniz, who is therst to create images of the circulatory system in the livingbrain. He develops a carotid angiography technique, whichinvolves making a surgical incision into the neck, identifyingthe carotid artery and injecting contrast into the artery, whichtransports it to the brain.

Drs. Evarts Graham and Warren H. Cole of Washington Uni-versity, St. Louis, discover in 1923 how to visualize the gallbladder with X rays by using contrast media, a discoverysignicant in the diagnosis of gall bladder disease.

This discovery demonstrates the role of chance in science,in that the doctors tried for four and one half months to visual-ize gall bladders in dogs by injecting contrast medium into thedogs in the morning, then taking X rays in the evening, to noavail. One day they nally produced a picture of a gall bladderin one particular dog, but for several days thereafter wereunable to recreate the results. In their hunt for an explanationfor this anomaly, they confronted the kennel attendanthadhe done anything different to that one dog? The attendantconfessed that due to a severe hangover he had not gottenaround to feeding that particular dog on the morning of thetest. If he had, the dogs gall bladder would have emptiedwhen the dogs food was digested. Thus the discovery wasmade.

19301939 In 1934, the American Board of Radiology is ofcially formed

and recognized by the American Medical Association. In 1936, the rst tomographan X-ray slice of the body

is presented at a radiology meeting. This revolutionary con-cept, in which the X-ray tube is moved by pulley around thepatient in order to take pictures on various planes, can focuson certain internal structures that cannot otherwise be seenclearly. This technique, also called laminagraphy, foreshad-ows the development in the 1970s of CT, or computed tomog-raphy.

While higher voltage X rays are being developed, their actualclinical benet remains untested. Beginning in March 1932,clinical trials are initiated. Results of the studies, comparing70,000-volt X rays to 200,000-volt X rays used on cancers ofthe larynx and tonsils, among others, are reported by scien-tists this way: The same results [cures] can be obtainedusing a [higher] dosage which causes considerably less dis-comfort to the patient. These results encourage furtherresearch into super-voltage equipment, although the equip-ment has some limitations; patient discomfort is not well-measured and the tumors evaluated are not the deep bodylesions that physicians still want to treat.

Blue Cross/Blue Shield and other insurance or medical pre-payment plans start to cover X-ray services, vastly increasingtheir availability.

t reatm ent devices soon ecl ipsed th e ear ly e lectronicgenerators . Cobal t 60, with an energy of 1 .33 mil-l ion electron vol ts , emerged in th e la te 1950s as th eworkh orse for radiation t herapy.

Th e second direction was th e developmen t of lowerenergy isotopes such as iodine 131 for use as diagnostictools. Trace am oun ts of iodine or oth er isotopes couldbe given a patient . By m easuring the out put of urine, forexam ple, using a Geiger count er, a physician could assesskidney function . With scintillation crystal detectors,a doctor could s tu dy an im age of radioact ive iodineuptake in the t hyroid gland, to s tudy funct ion and toinfer the presence of tum ors.

Advances in X-ray techniques cont inued apace.Russel l Morgan at th e Un iversity of Chicago devel-oped phototiming, a method of matching exposures tophysical characteristics of patient s. Morgan, EdwardCh am berlain of Tem ple Un iversi ty an d, pr incipal ly,John C oltm an of the West inghouse C orporat ion arecredi ted with the conceptual development of e lec-tron ic image inten sification, togeth er bringing fluoro-scopic stu dies out of darkened room s. Reduced amou nt s

of radiation could be fed into a fluoroscopic screenand brighten ed several thou sandfold before being dis-played on an ou tput screen. This procedure al lowedrecording of m otion, such as t he utt er of a heart valve,on m otion picture lm or videotape withou t subjectingpatients to u nacceptable levels of radiation.

Radiologis ts and som e oth er physicians began t oexpand t he u ses of hollow catheters to inject cont rastliquids into t he vascular system and other body chan-nels . The ski l ls needed to thread a catheter t ip intoposition to visualize th e coronary arteries or the vesselsof th e head were compared by one investigator to th e

task of pushing a rope through t wisted passageways.A major advance in isotopic diagnosis resulted fromth e developm ent by H arold Anger of th e Un iversity of Cal i fornia of the gamma camera, with i ts array of photomultiplier tubes and a large crystal which short-ened scanning tim e. This was coupled with t he devel-opmen t of various chem ical form s of techn etium 99m,an isotope with a six-hou r half life. Technet ium couldbe tagged to various chem icals to allow concen trationin different organs of interest. Given its six-hour decayperiod, relatively larger am oun ts of isotope could be usedwith out in creasing pat ient exposures . Soon isotope

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This X-ray image of a foot in a high-button shoe was typical of early images reproduced in the popular press after the discovery of the X ray. This image was made by Francis Williams of Boston, one of the rst radiologists,in March 1896.

BEA M LIN E 31

Angiographic work began in January,1896, with this post-mortem injection of mercury compounds. This image was made by E. Haschek and O. Lindenthal of Vienna.

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scans were the preferred method of explor ing many problems in thebrain and liver.

By th e late 1950s, investigators in-cluding Henry Kaplan and th e Vari-an broth ers at Stan ford Universitywere w orking on a device called a lin-ear accelerator to generate highenergy X rays or electrons for cancertreatm ent. Referred to as linacs, thedevices soon grew sm aller, deliveredhigher energies and becam e safer andm ore reliable. Th ey produced con-trolled energy beam s in ran ges from4 to 25 million electron volts, andgradually displaced cobalt u nits asth e primary radiation t herapy sour-ces in most advanced coun tries.

O

N T H E D IA GN O ST IC SID E ,the 1960s brought the adventof diagnost ic ul t rasound

with great promise. Soon u ltrasounddevices ut ilized a crystal t ransducerth at boun ced pulses off body struc-tures and displayed the echoes as ascan. Motion w as added, and Dopplertechn iques rapidly allowed study of blood flow and other physiologicalprocesses. Even after 30 years, th ereare s t i l l no indicat ions of harm fulbioeffects from ultrasoun d exposuresa t t h e e n e r g y r a n g e s u s e d f o rd i a g n o s i s .

By th is t im e, some radiologis tshad begun to inquire into th e newinformation systems based uponhu ge, un gainly devices called com-puters. But comput ers soon sh rank in size, grew in pow er, dropped inprice and began to be available inresearch centers. Th ey were used forcomplex radiation treatment plans,allowin g far m ore speed and sophis-tication with isodose curves than waspossible wit h m anu al calculat ions.

Diagnosticiansused computersfirst for imagea n a l y s i s , c o u -p l ing dens i to -meters with themto obt ain b asic dat a . These effortsmet w ith l imited success .

Early in the 1970s, diagnosticradiology made a huge leap intocross-sect ional imaging with thedeve lopment o f computed tomo-graphy ( C T ). Earlier, mechanicaltomography had been used for lim-ited purposes. But here was a com -pletely new t echnology, producingwh at looked l ike bloodless s l icesacross th e body area of interest. Th efirst scann er, devised by GeoffreyHoun sfeld of EMI in England, couldimage only th e head, and requireda pat ient to place his skul l into a

water bath w hile the X-ray tube andreceptor mechanical ly advancedaround the h ead. Im provem ents wereswift as oth er man ufacturers replacedmechanical par ts with electronicones. Soon, a ring of X-ray tubesand receptors could obtain im agesof any t ransverse body plane inseconds , and complex mathema-t ical a lgori thm s could draw clear,sharp images out of m illions of bitsof information .

By advancin g the plane of the scanin small steps, a three-dimensionalconstru ct of a suspect organ could bedeveloped. Elliot Fishman at JohnsHopkins worked out a reconstruc-tion m ethod to give surgeons th ree-dimen sional simu lations of crushedor missh apen body parts for guidan cein delicate operations. And radiationoncologis ts used com put ed tomo-graphic images to plan their treat-ment elds.

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19401949 The Betatron, a circular electron accelerator, is developed by

Dr. Donald Kerst of the University of Illinois between19401943. It generates energy (20 million volts or more) byorbiting electrons, faster and faster, through a large dough-nut, a circular glass tube with a heated cathode inside ahuge electromagnet.

19501959 Dr. W. Goodwin introduces the concept of X-ray guided per-

cutaneous nephrostomy, in which a needle and then acatheter are inserted directly into a kidney to create adrainage tract above an obstruction (kidney stone, cancer),allowing urine to escape from the kidneys. This procedureallows some patients to be treated without surgery.

Radioisotopes are introduced as sources of gamma-raybeams for radiation therapy. The process works, for example,by changing harmless cobalt 59 into cobalt 60, a highly unsta-ble nucleus that decays. As that happens, it releases twogamma rays. The gamma-ray beams adequately reach deepcancers without damage to the skin. Cobalt units are easy tomake and quickly become a cheaper, safer alternative to theBetatron, though later they will become virtually unused.

Ultrasoundimages created from the echoes of sound wavesbounced off tissuewhich has its roots in World War IIs

sonar (sound navigation and ranging), begins to showpromise in medical diagnostic applications. A Swedish physician, Dr. Sven Ivar Seldinger, renes

Dr. Monizs and Dr. Forssmanns work in angiography fromthe 1920s when he learns how to insert a catheter into ablood vessel without surgery. He uses a t iny guidewireinserted with the help of a needle into a blood vessel. Thecatheter is placed over the guidewire and into the vessel,after which the guide wire is removed. He then watches thelocation of the catheter on uoroscopy.

The rst image of a human coronary artery recorded in vivowith synchrotron radiation. This coronary angiogram was done at the Stanford Synchrotron Radiation Laboratory at the Stanford Linear Ac celerator Center in May 1986. The identied structures are an internal mammary artery ( IMA ), the aorta ( AO ), the left anterior descending coronary artery ( LAD ),the right coronary artery ( RCA ), and the left ventricle ( LV ).(Image courtesy of Edward Rubenstein, M .D .)

Because of political decisions based on h ealth plan-ning laws, many C T scanners were located out side of hospitals. In just a few years, CT scanning had becom estat e-of-the-art techn ology. Th e Unit ed Stat es had morescann ers than th e rest of th e world, and Los Angelesalone had more th an Great Britain.

Th ere was more to com e. In less than a decade, mag-netic resonance imaging burst on the scene w ith evenm ore promisingand even more expensivetechn ology.M R image analysis technology was comparable to C T ,but no X rays were n eeded. Instead, M R un its relied onstrong magnets, as mu ch as 8000 times as strong as theearths magnetic eld.

In an M R unit, m agnets rim an aperture into whichpatient s slide on a gant ry. Th e strong magnetic eld actsupon t he inherent m agnetism of the t rillions of hydro-gen atom s in th e hum an body. When th e m agnetic eldis imposed and released, hydrogen atom s emit a faintradio s ignal . Det ect ion an d analysis of these s ignalsproduces the im age.

M R proved to be complimen tary to C T . M R imagescould be created in any body planeaxial, sagittal,

oblique, AP , or all of th em . Soft t issue detail allowedbet ter s tudy of glandular systems. And soon, newdevelopments in CT resulted in spiral scanning, with t hemachine advancing across the chosen body area toproduce hundreds of slices at any designated interval.Contrast agents, very different for C T an d MR , allowedstudy of the inside of body organ systems. Various oth-er mathematical t r icks a l lowed the electronic sub-tract ion of other anatomic s t ructures to reveal avascular system of the h ead and neck w ith t he shad-ows of the sku l l , brain, and oth er s t ructu res erased.Strictu res, emboli, kink s, and accumu lations of plaque

had nowh ere to hide.In t he sam e years, the t erm int erventional radiologycame in to u se to describe th e ability of physicians u singcatheters and uoroscopy to detect and correct vascularinsufciencies and strictures in oth er body ductal sys-tem s. Init ially, catheters insert ed into arteries or uret ersallowed deposit of contrast agents at su spect spots. Thenmicro-sized tools were threaded through the samecathet ers to correct problems. Andreas Gru nt vig of Emory U niversity ren ed th is process, devising a balloon-tipped cath eter that could be advanced within an artery

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BEA M LIN E 33

An image of a human coronary artery recorded in vivoat the National Synchrotron Light Center, Brookhaven National

Laboratory, in November 1992. Improvements in the imaging system have increased the quality of the angiogram from the image shown on the opposite page. In this image, the entire

length of the right coronary artery ( RCA ) is shown.(Image courtesy of Edward Rubenstein, M .D .)

19601969 In 1960, Dr. Robert Egan of the University of Texas M.D.

Anderson Tumor Institute, Houston, with the support of theU.S. Public Health Service, publishes the results of an inten-sive, three-year study of mammography. Although previousstudies of X rays of the breast have been done, Egans studyconclusively proves mammographys effectiveness in earlydiagnosis. With neither physical exams nor any knowledgeabout the womens medical histories, Dr. Egan examinespatients mammograms and diagnoses whether or not canceris present. Egans accuracy in nding breast cancers isremarkable9799 percentand his precisely controlledmammography techniques mean that other radiology facilitiescan duplicate his results.

Drs. Charles Dotter and Melvin Judkins of Portland, Oregon,are the rst to report performing a transluminal angioplasty, anon-surgical technique to unblock a vessel clogged withplaque. They insert screw-tipped catheters into the narrowedvessel, starting with small diameter catheters and slidingbigger and bigger catheters over them, to push the plaque tothe interior walls of the vessel sides. The technique is notwell-accepted except in Europe; bypass surgery is still thepreferred treatment method in the United States.

A survey conducted by the U.S. Public Health Service reportsthat 48 out of every 100 persons receive X rays during any

one year, with urban residents having the most X rays (53 outof 100) and farm dwellers (31 out of 100) having the fewest.

19701979 CT, or computed tomography, which takes X-ray slices of

the body and images them on a computer screen, is intro-duced. Like the rst tomography units introduced in 1936, theX-ray tube rotates around the patients body, taking X-ray pic-tures as it moves. With the addition of computer technology,CT images can now be manipulated and the slices can evenbe put back together to create more 3-dimensional images.

to a n arrowing. Once in position, th e balloon is inat ed,compressing the fatty plaque against t he artery w alls andrestoring free blood flow. Soon th e balloons w ere aug-m ented w ith t iny rotary saws, lasers, and targeted med-icines. Researchers also created collapsible baskets t osnare kidney or gall stones for rem oval withou t an opensurgical incis ion. Recent ly, s tent s (m etal or plast icsleeves) have been developed for insertion into arteriesor other vessels to keep critical spots from narrowingafter th e angioplastic procedure. Not all patients respondto t hese procedures, but t hose wh o do save considerabletraum a and cost, sometim es even returning home theday of the procedure.

Of course, not all new ideas have been as fruitful asCT an d MR and linacs. Hopes that the bodys natu ral heatemissions could be a diagnostic tool w ere dashed w henthe heat- induced im ages, or therm ograms, could notbe correlated w ith disease problems. Th e use of oxy-gen poten tiation devices like pressure cham bers to treatcancer pat ients promised to help those with anoxictum ors. But after som e years of tests, the results failedto justify the efforts. More recent ly, radiation on colo-

gists have been experiment ing with heat as a radiationpotent iator. How ever, th e techn ical problems of con-trolled heat ing of a single body area durin g radiation havenot yet been overcome.

While diagnost ic an d th erapeut ic radiology havedeveloped as separate and den ed disciplines, th ere havealways been synergisms w ith ot her m edical specialties.Some tw o-th irds of all American cancer patien ts receivehigh energy radiation as a portion of their treatm ent.Current ly, most cancer centers a t tack m ost form s of cancer with a com bination of surgery, radiation, cancer-killing chemicals, and even m onoclonal antibodies or

imm un ological agents.

FOR THE ENTIRE CENTURY of radiology, physician sspecializing in t his area have perform ed m ost, butnot all , of th e procedures needed by Americans.Many pr imary care physicians undertake l imitedprocedures in t heir ofces. Som e specialists, such as car-diologists or orthopedists, perform examinat ions relat-ed to t heir areas of interest . Dent is ts an d podiatr is tsdo l ikewise. About two-thirds of medical imagingprocedures are done by radiologists.

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34 SU M M ER 1995

Thrombolysis, which dissolves clots in blood vessels by deliv-ering thrombolytic (clot breaking) drugs to the site or into thevascular system, is introduced by Dr. Charles Dotter. Using athin catheter, a dose of a thrombolytic agent such as streptok-inase is injected into the clot, dissolving it. One drawback ofstreptokinase is that it can induce allergies with repeated useover time. Later, synthetic thrombolytics that do not appearto induce allergic reactions will be used.

Swiss physician Dr. Andreas Gruntvig, later in the UnitedStates, invents balloon angioplasty. A tiny deated balloon isplaced at the end of a catheter and threaded on a guidewireinto a plaque-clogged section of blood vessel. The balloon isinated, and the plaque is pushed to the sides of the vessel.Then the balloon is deated and removed. The rst applica-tions of balloon angioplasty are all in arteries in the arms orlegs. Balloon angioplasty is an instant success, in partbecause it can be used to open smaller, more fragile arteries.

1980Today MRI (magnetic resonance imaging; also referred to as MR)

the marriage of a strong magnet and a computeris intro-duced. Instead of X-rays ionizing radiation, MR uses a mag-netic eld around the body and a radio signal to createimages. MR works by having a patient lie in a large magnetictube, which forces the hydrogen atoms in the body to line upin a polar formation. Then a strong radio signal bombards theatoms, and protons spinning in the hydrogen atoms aremomentarily knocked off course. When the radio signal isturned off and the atoms return to their normal orbit, they emita faint radio signal, which is used by a computer to measurethe speed and volume by which they return to orbit. MRsees hydrogen atoms in the bodypresent in all tissuesand thus is exceptional at imaging both hard and soft tissue.

Pulsed uoroscopy reduces radiation exposure by using shortbursts of high-intensity X-ray beams (up to 12 seconds; any-thing longer would burn out the tube) alternated with lowerintensity beams. The high-intensity beams linger on thevideo screen, allowing the physician to view the anatomy likeslow-motion moving pictures.

PET (positron emission tomography) begins to be used in clin-ical applications. It watches the way cells eat substancessuch as sugar. The substance is tagged with a short-livedradioisotope (unstable atoms that release stray particles thatcan be seen with gamma cameras), then injected into thebody. The PET scanner watches as the radioactive materiallights up in cells, identifying areas where cancer cells mightbe present. Cancer cells have a higher metabolism than nor-

mal, healthy cells. Teleradiology, the ability to send images through the informa-

tion superhighway, is introduced. Teleradiology usesinformation-networking capabilities to transmit images fromone place to another. However, it is more difcult than send-ing a written document because the digitized, computerradiology image contains so much more information than theprinted word.

Historic Whole Body RadiographsA whole body radiograph of a dead soldier (page 25, left), wastaken, in nine sections, by Ludwig Zehnder at the University ofFreiburg in 1896 and measures 1.84 meters in height. The exposuretime was approximately 5 minutes per lm. The faint writing, with anarrow pointing towards the forehead, reads small arms projectilelocated in the facing temple at a distance of 20 cm from the dryplate. The second radiograph (page 25, right) is a single-exposurewhole body image taken by a Dr. Mulder in Bandung, Java, about1900, presumably of a living person, wearing knee-length boots,with bunches of keys attached to an unseen belt.(Courtesy Deutsches Museum, Munich, and Bob Batterman, CornellUniversity).

Still , th e growth of managed care as an alternat iveto t radi t ional medical pract ice has dr iven manypat ientsand t heir doctors and h ospita lsinto con-trolled pattern s. One result has been a reduction in t hevolum e of medical services, includin g radiology, deliv-ered to m anaged-care plan pat ients . Mu ch of the re-duction in imaging comes as a loss to ph ysicians wh oself-refer procedures on th eir own pat ients. An d ques-tions arise: will m anaged care plans pay for m ore ex-pensive procedures , if man agem ent decides th e s im-pler ones are less expensive, and are adequate?

And with impen ding cut backs in federal health spend-ing and down ward pressures on costs by private pay-ers, the broader question is wh ether or not the n ationwant s and w ill pay for new er and better t echnologies. Agood example is positron-emission t om ography ( PET ), inwh ich a very short-lived injected isotope is used as th eenergy source for cross-sectional imaging rather thanX rays. PET has proved itself as a research tool. But itsacceptance for c l inical appl icat ions is proving moredependent on cost factors than scient ic ones.

Ever since X rays were discovered by a physicist , th e

growth of radiology has been dependent on t he cont ri-bution s of th at discipline, as well as th e contribut ionsof engineers, biologists, com put er scientist s, radiologictechn ologists, and a broad indu strial base. With out th esecontributions, m any of radiologys m ost im portant clin-ical advances would never h ave occurred. Clear ly,radiology has earn ed a vital place in m odern m edicine.It m ay well be that t he circum stances in w hich it willbe practiced are un certainbut th en, so are m ost oth erthings about modern health care.