“The army called me down to New York [in 1950]. I was with New York University (NYU)—and the colonel said to me, ‘Well, if you volunteer to be in the army, then you'll become a lieutenant, an officer. But if you don't volunteer, you'll be drafted anyway, and sent to boot camp. So I volunteered. And they sent me to medical field service school in Fort Sam Houston, Texas. And that was kind of interesting. And then, I guess my card dropped out, they wanted a dentist who was a physicist. And that was me.” Robert S. Ledley Dr. Robert S. Ledley is credited with “sowing the seeds” for the field of medical informatics [Ledley 1959],1 initiating the development of computerized medical image analysis [Ledley 1964],2 and for being the principal investigator of the Protein Information Resource (PIR) for 20 years [Dayhoff 1965].3 Dr. Ledley is best known for developing the first whole-body computerized tomography (CT or CAT) scanner in 1973 (Patent No. 3,922,552), which revolutionized diagnostic medicine. Dr. Ledley's first CT scanner [which he called the Automatic Computerized Transverse Axial, or ACTA, scanner; [Ledley 1974a, 1974b]2, 4 is now owned by the Smithsonian Institution's Museum of American History [Kondratas 2005].5 Using his scanner, he was the first to perform three-dimensional reconstructions [Huang 1975],6 the first to use CT in radiation therapy planning for cancer patients [Scheer 1977],7 and the creator of many other “firsts” in the application of CT in medicine. The following story describes his efforts to develop this scanner. I always liked physics. I started at Columbia [University in 1942]. Once you’re in the college, you can take any course in the whole university. In those days they only gave one year of college physics, and everything else was graduate physics. At Columbia, [graduate physics] was incredible. I had something like eight Nobel Prize winners as teachers. Hans A. Bethe,a for example, came down from Ithaca and gave a course on atomic physics. It was absolutely incredible. And I had [Enrico] Fermib in thermodynamics. Yeah, it was a fantastic place. I received my masters' degree in [Theoretical] Physics in 1949. I went to dental school because my father said, “You know, a physicist can't make a living, really. And the only thing you can do is be a poor professor. What you should do is become a dentist”—and we had a number of dentists in our family—“and then you can support your love of physics with your dentistry.” And it turns out that I knew something about the history of physics. In the late 1800s and early 1900s, that's what was done. Most people supported their physics by doing other things.c The only one who I knew who didn't do this was [Isidor Isaac] Rabi,d and he was a professor and head of the physics department at Columbia. And he thought the idea that I was going to dental school at the same time I was taking graduate courses in physics was hysterical. It was the funniest thing he had ever known about. I graduated from Dental School in 1948, but I was too young to get a license. You had to be twenty-one to get a license. I moved to Georgetown University in 1970. I moved the [National Biomedical Research] Foundation and everything, right in here, into these quarters [lower level of the medical library at Georgetown University]. And I had big grants from NIH. I had an engineering equipment grant, to build equipment that was required. And I also had a programming grant to do all the basic programming work that was required. And somebody said to me, “Why don't you put the two grants together, and it’d be a unified grant.” Fine, okay, so I put them together—NIH, whatever they say, you do. And then Nixon was president, and I get a call from NIH that the grants were approved, ready to be paid. This was in May. They were going to be paid in June. [Then] I get a call from NIH, “Nixon cut back the medical research funds”—“and we don't have the money to pay you.” I had about, I don't know, forty, fifty people working. So I had to figure something quick! So I talked to John Rose, hopefully my savior, and he said, “Wow. Well, you do scanning, right?” [RL:] “Yeah.” He said, “Well, Dr. Luessenhop is interested in buying a scanner.” So I went to see Dr. Luessenhop. Nice fellow, chief of Neurosurgery, but he was a brain surgeon. He says, “Well, I was going to buy this machine,” and he shows me a slick brochure, the EMI machine [Hounsfield, 1976].8 It was a head scanner only. But what he didn't know is that they didn't have it yet. They just had a brochure! So I looked at this book, and sure enough, you could see organs, but they were fuzzy. It was terrible; picture after picture. I didn't see how they could use much of that. But at the same time, I read a paper in The Journal of Applied Physics. It was written by a fellow by the name of Cormack at Tufts [Cormack 1963].9 And he took a cylinder of aluminum and a cylinder of wood, with a hole in it, that the aluminum fit into, and he scanned it, one scan. And he said, “Well, it's circular symmetric, so I’ll make a whole lot of scans, because they're all the same.” Okay? And then he worked out the absorption coefficient of the aluminum and the wood, to a very large number of significant figures. And I thought to myself, “Man! that's great! We can do it!” And I figured that I could make it. So I went back to Dr. Luessenhop and I said, “I can make it, and it’ll be half the price” [of that quoted for the EMI scanner]; I didn't even know what the price was! It was a miserable machine. But I knew what to do. I was going to use convolution.e How did I know that? Well, Science magazine began putting pictures on their covers in the late ’60s, I think. And they had a picture of a virus. They made the picture of the cross-section of a virus, and it looked kind of interesting. They took an electron microscope, and they scanned the virus right across. And then they couldn't really rotate it, so they said it's circularly symmetric, and they did what Cormack had done. Anyway, what they did use was [convolution]. Great! People were talking about [convolutions] because you could take scratches out of pictures and things like that. So I figured, “That's it!” And I made a deal with the university. $250,000 of the foundation's money, and we’ll make Dr. Luessenhop a machine that can scan every place on the whole body. A better one! Well, I said I did. (laughter) If you haven't done it, you don't know if you can do it. So we went ahead. I had it designed in my mind, and I drew it on a paper, and we had a lot of cooperation. There was a machine shop—you can't believe it—in Georgetown, on Wisconsin Avenue, just below M Street. Can you imagine? A machine shop run by Allan Mitchell. And I went down, and this guy had a big lathe. Okay, great, so that's the guy. So I went to him, because he had a big lathe. I told him, “I'm making a medical machine.” “Oh, you’re making a medical machine? Oh, that's wonderful. I'd love to help you out.” Of course, they charged, but still. And he said, “I’ve got one fellow, a young man I just hired, and he's very smart, very clever guy, and I’ll put him on it, totally, he will be your machinist! He’ll do nothing else.” Because I knew it had a lot of parts. Then I went around to get a mechanical engineer—couldn't get a mechanical engineer. I went to every engineering school in the region, and I couldn't get an engineer to do this for me. I could show the machinist what I wanted. So I figured, “Well, I’ve already spent two weeks on this, going around. Forget it, I’ l do it myself.” After all, I had had a course in engineering mechanics. So I designed every detail in it myself. There isn't a thing that I learned that I didn't use. So I sat down and designed it in detail. I also had a great electronic engineer, Tom Golab, and a great programmer/mathematician, James Wilson. And what I did was, I drew a sort of three-dimensional picture to show what each part was, and then I made the ordinary mechanical engineering drawings [See Fig. 1 for a copy of the mechanical drawing included in the original patent application]. And this fellow, Frank Rabbitt was his name, and he was great. He had all the sense that was required. So I drew him the pictures, and we’d leave them under the door at about eleven in the evening. It was an around-the-clock job. And then in the morning he’d study the plans when he came in at six in the morning, and he would call me up and say, “Do you really mean you want the hole here? And which hole is it going to be attached to? Are you sure?” And I looked at it, sure enough, he was right. You’ve got a figure that's off slightly he’d say. He was a great guy, and I hired him afterwards. But he never had any engineering training, but he had the engineering sense. Mechanical drawing of the ACTA scanner from Dr. Ledley's patent. So I decided to use cold-rolled steel; that was the strongest material for its weight [at that time]. So I found out about that, and I [went to] take a look at a piece of cold-rolled steel. It looked terrible! It was blotchy, looked like it was rusty, but it wasn't rusty. And I decided the doctors would never go along with that. It's got to look pretty. So Capital Cadillac in those days was down here. So I figured, well, car places have paint shops. So I go down to Capital Cadillac and I say, “I'm making this medical machine.” “Oh! You’re making a medical machine? We’d love to help you out.” So I said, “Cold-rolled steel looks terrible, and I need it painted before it comes here, right from the machine shop.” He said, “I have the ideal person. I’ll put him totally on your job.” And it was a man, who was ready to retire, but he still had time to go, another six months or so, and he said, “This fellow is a detail man. He’ll do the greatest paint job. I hate to give him big jobs, because he can't carry things. He's an older guy.” So that's what I did. So I designed the parts at Georgetown University, I went to Allan Mitchell, they machined it. And the fellow took it over to Capital Cadillac. He was supposed to call me when he got it, which he did, and then he painted it, and then we brought it back. I don't remember whether he brought it, or we went over there to get it. And all I had to do was ream out the threads, because he painted everything. So that's how we made it. That's what we did. And it was a resounding success.f [See Figs. 2 and 3.] The 0100 ACTA Scanner (which stands for automated, computerized, transverse axial scanner) is the world's first whole-body scanner. The computer used to run the ACTA Scanner. Oh! it feels so great. I gave a lecture the other day at the hospital over in Virginia—Fairfax Hospital. I gave this lecture on something about the history, this kind of thing, telling these stories. And a lady stands up and says to me, “You know, I'm walking because of you. I had a bad disease, and it was diagnosed by one of your machines. I'm a nurse now. I am always on my feet, and I always have to walk around. And if they didn't make the diagnosis, I wouldn't be walking today.” So that's the reward, when you really get down to it. I’ll tell you the story of my first life-saving. We were fixing up the machine and making it a little better, this, that, and the other, and Dr. Luessenhop comes in the room, and he looks at the pictures that I made, there were no CT phantoms. You know what a phantom is—a model that you make. They were models that generally were exactly like what you were going to take X-rays of—to see whether something worked—that was the purpose of the model. I figured the hardest thing was going to be the brain. And what I used was the skull, a real skull that I had when I went to school. I took a course in gross anatomy, had to have a real skull. Nowadays, you don't have to have a real skull, but you did then. And in those days there were butchers, and I had delivered to the university, every day, fresh calf's brains. Calf's brains were a delicacy in those days. What were they called—[sweetbreads]? And then I put the calf's brains in the skull, and put test tubes of water in for the ventricles, and scanned them. That was my Phantom. So he said, “That's good enough. I'm bringing down a patient.” This couldn't be done today [because of the Institutional Review Board procedures]! So we scanned a patient, and that was the beginning. Now, after about two weeks, there was a pediatric neurosurgeon, Dr. McCulloch. I got to know all the neurosurgeons. And he says to me on a Monday morning, “Did you hear about the wonderful case we had?” So I said, “Well, I'm sure I heard about it, because I must have seen it, because I haven't walked away from that computer.” I was there eight hours a day with that machine. I couldn't get myself to walk away. It was built into the room in which it was going to be used, and I couldn't get myself to walk away from it. I just couldn't walk away. So he said, “Well, we had a four-year-old boy who fell off a bike and hurt his head. Nobody saw him fall, but the parents took him to a pediatrician. He was kind of groggy, and the pediatrician brought him into the emergency room.” This is what Dr. McCulloch is telling. And he says, “So I happened to be in the emergency room at the time. So I looked at the kid, and I thought to myself, ‘You know, I think we ought to scan him.’ So I took him upstairs and I scanned him.” So I said, “Well, who ran the machine? Because I didn't see any four-year-old boy. There wasn't any four-year-old boy. What are you telling me about?” I stood there every day, eight hours a day, I was standing there, all the time the machine was being used. So I said, “Who ran the machine?” He said, “I did.” I said, “You did?! How’d you know what to do?” And he says, “I watched the tech do it. I’ve seen it.” I said, “And you just knew how to use the machine?” He says, “Yeah! And there was a bleed. And I took him down to Surgery and took out the blood, and you saved his life.” It was incredible! He said, “If I'd waited till Monday, then it would have been over, the kid would have been dead.” That was it. Can you imagine that? That was our first save. And I thought to myself, “What am I standing around for? This neurosurgeon just watched and he could run the machine. I don't have to watch!” [This happened] over and over again, and I was inducted into the National Inventors Hall of Fame. And they had a banquet at the museum. There were ten people at each big round table. After dinner, this lady comes over to me, and she gives me a big bear hug. I mean, she was big herself, she was tall. So I said, “Now, what did I do to deserve that?” And she says, “You saved my daughter's life.” So that's what makes it worthwhile. Well, I started my own company to make the scanners. I was manufacturing the scanners. Well, it was almost that bad. The vice-president in charge of the medical center, a fellow by the name of Matt McNulty—he passed away—but he comes down one day and says, “A lot of people want this thing, don't they?” [He meant] radiologists. I said, “Oh, yeah!” He says, “Well, you really can't go into business in the basement here.” I said, “Yeah, I know.” So he says, “Why don't you just form a profit-making company and bill them?” I said, “Okay, I’ll do that.” So I did, I formed a company called DISCO, Digital Information Science Corporation.g And when Disco was about four or five years old, it was difficult to fill all the orders. Not only that, but there was no venture capital in those days, no new venture capital. And somebody says to me, “Well, you go to the bank and you borrow money.” Okay, so I go to the bank, and I tell the guy I want to borrow money. And I’ve already told him all the things I'm doing. And he says to me, “Could you tell me again exactly what you’re doing?” So I tell him again, and he says, “Well, we actually only who build So I figured of that, I'm my time. So I said to the when they wanted it course the only paid me So I had to build with in And then when I'm half another [Then] when I it, the That's the I did it. That was the the time we got the to the time we it was about I hired all the That's the Now, what happened after a of I decided I’ve got to this I mean, this is too of the was, the in That the out of me, because I absolutely had to build that machine for gave me or And that's what I'm going to do. any about it, I’ve got to People that give me for it, they're going to get their they're going to get it. And that me up at It was a big We had a or And then I had a I delivered the parts to the room in which it was to be Well, first of all, they had to their And then I sent around an to make sure that they the It had to have water to the an to water They had to have the right and and everything. There was a lot to do. What I didn't was that these people made this a of of their I didn't that I went to one the first It was in in I said, “Do you have your room And he said, “Yeah, I have it all and he me to the “You want to see I walk and it had It was at Georgetown, they had the that you ever It was So that was a real good machine [Ledley Dr. Ledley was in in He a degree in physics and from Columbia University and a from the New York University of in In to the ACTA scanner, Dr. Ledley the first purpose image called the the for used by the and many and one of the first machines. He the first for on computer and in used for He was inducted into the National Inventors Hall of in for his of the first CT scanner, and is a of the of for the National of In he was the National of by He was a fellow of the American of and was the in by the Digital and New and New American of and Digital New of in and New New and A. of Dental and National Biomedical and for Computerized and and of the in and Computerized and and of from first whole-body computerized and for first purpose image Digital and In Dr. Ledley or over

In this paper, we present an X-ray radiography system which can provide intra-operative stereo imaging of the patient's operational area during a spinal surgery. We use two horizontally separated X-ray tubes and a flat-panel X-ray detector mounted on two ends of a C-arm microcontroller synchronizes the image acquisition, and the left and right images are grabbed into the system alternately. Surgeons can have a 3D perception of the spine's X-ray image in real-time. We further developed a whole image processing language called PPL. PPL takes images as operands instead of dealing with complex pixel operation. To speed up the rendering speed in a network environment, we proposed a level of detail (LOD) with reverse prediction method that can fast transmit images over Internet in real-time.

It is pointed out that even though the red-green-blue (RGB) color system is used by TV cameras and monitors, the perceptions of human observers are better described by other color systems which correspond more directly to the subjective human sensation of color. One of the simplest and most widely used of these alternative systems is the hue, saturation, intensity (HSI) color system. The authors describe the detailed derivation of the HSI system in terms of the RGB system and discuss how pattern recognition techniques and concepts originally developed for black-and-white images can be applied to color images in the HSI system.>

Three methods approaching the analysis of cells are described, with applications. The methods presuppose that the picture of the cells has already been digitized and resides in the memory of a computer. The first method is an ad hoc approach in which intercommunicating programmable cursors are utilized for the detection of boundary and area features. The second method is concerned with an evaluation of the curvatures of boundary segments in relation to the overall shape of the boundary. The third method imbeds the picture in a non-Euclidean coordinate system, preserving as invariants salient features while negating the effect of nonsignificant distortions.

A new algorithm is given for reducing the number of additions and subtractions required in binary division in a computer. The algorithm is presented in two parts. A simplified algorithm, which can significantly reduce the number of operations with minimal additional circuitry, is used to develop the justification of the method. The complete algorithm introduces modifications which allow the minimum number of operations by examination of no more than the leading five bits of the divisor and remainder. An average of two-thirds can be saved in the number of operations.

A systematic digital computational method is given that involves the use of Boolean matrix equations for solving certain types of functional circuit design problems. Specifically, all sets of Boolean functions f1(A1, . . ., A1), . . ., fJ(A1, - . . ., A1) are found such that if circuits with these outputs are connected to a circuit that generates the known Boolean function F(f1, . . . , fJ, X1, . . ., XK), then the output will produce a given desired function E(A1, . . ., A1, X1, . . ., XK). Illustrative examples of the method are presented.