Imaging Services

Glendon G. Cox,M.D.,MBA,MHSA, Bill Rostenberg, FAIA, FACHA, and Frank Zilm, D.Arch.,FAIA

N
o other area of healthcare has experienced the explosion of technological development that followed the discovery of x-rays in the last decade of the 1800s. The ability to image the internal structure of the human body has radically changed the practice of medicine. Today doctors can not only see the organs and actions of the body, but they can also use medical imaging to guide invasive therapies and interventional procedures - procedures that are often less risky, and less costly than conventional surgery, or those that would be impossible using even the most advanced surgical techniques. There is no doubt that continued advances in imaging will play a major role in shaping future health care facilities.
.
We will explore the basics of the physics underpinning this area, describe current imaging modalities, and then discuss the layout and design required to support safe and effective care.

Six weeks in 1895

RontgenUntil the end of the 19th Century physicians had few tools to diagnose patients other than their interpretations of a patient’s symptoms, their observations based on their five senses employed in the course of physical examination and a limited number of laboratory tests. In many cases exploratory surgery was necessary to allow doctors to directly see the internal tissue, and organs. This surgical approach to diagnosis carried the significant risks of primitve anesthesia and surgery, infection due to limited antisepsis and severe patient discomfort.
.
Everything changed at the end of the century due to groundbreaking research of Wilhelm Röntgen, chair of the physics department at the University of Giessen. Röntgen was studying electric currents passing through a variety of vacuum tubes. Setting up for an experiment on November 8, 1895, he encased one of his “cathode ray tubes” in cardboard and darkened the laboratory as he energized the tube to be sure that the light generated by the tube would not interfere with his intended observations. As he prepared to switch off the current to the tube in the darkened room, he noticed a faint, flickering light glowing on a nearby workbench. After repeating his observation upon re-energizing the tube, Röntgen struck a match and discovered that the light emanated from a cardboard screen coated with barium platinocyanide, a crystalline salt of barium that emits light when exposed to radiant energy. Röntgen knew that the effect on the screen was occurring at too great a distance to be due to the cathode rays that were the subject of his original experiments. Over the next seven weeks, Röntgen turned his complete focus to a series of experiments that would ultimately result in a thorough description of the properties of the previously unknown “X” rays. Among the most intriguing properties of the “new” rays was their ability to penetrate solid objects. A mere two weeks after his discovery, Röntgen took the first anatomic “photograph” using the invisible X-rays—a picture of his wife’s hand. Legend has it that when she saw the bones of her hand she exclaimed “I have seen my death!”

First X-Ray ImageRöntgen published his first paper on X-rayson December 28, 1895, seven weeks after his original discovery, an astonishingly short period. He continued his work with x-rays until shortly before his death on February 10, 1923. In 1901 Röntgen was awarded the first Nobel Prize in Physics.
.
.
.
.
.
.
.
.
.
Physicians quickly realized the potential benefit of this new imaging tool, but did not understand the associated risks. Early radiographs often required long exposure times using beams of relatively low energy which could produce severe burns. In addition, as a result of the practice among early radiologists of testing the “quality” of their x-ray beams by placing their hands between the tube and imaging plates, its became evident that exposure to x-ray radiation could lead to tissue damage, ulceration, necrosis and cancer. The results of long-term, repeated exposures of this type are seen in these images of a radiologist’s hands obtained several years apart. Fortunately, Röntgen himself observed that lead was one material that could absorb X-rays. Soon, this readily available, highly malleable metal was widely used to shield patients and care giver from unnecessary exposure.
.EARLY IMAGING
Through most of the 20th century (until the 1980s), X-ray techniques (primarily radiography and fluoroscopy) were the primary tool for imaging the body. In both radiology and fluoroscopy X-rays are passed through the body part of interest and strike a receptor. Denser body tissues absorb more X-rays, resulting in a decreased number of interactions with the receptor surface. In the radiographic technique that became most widely accepted through the 20th Century, the decreased numbers of x-rays that passed through denser structures created the “white on black” images of bones with which we are all familiar.
.
X-rayThe main difference between radiography and fluoroscopy is that radiography produces a “snapshot” or single image of the body at a given point in time. Fluoroscopy, on the other hand, produces a series of images that effectively create a radiographic movie of body parts or organs in motion. Common applications of fluoroscopy include viewing the movements of the heart or the contractions of the esophagus and stomach.






Until the late twentieth Century, the primary radiographic and fluoroscopic detector systems relied on conversion of x-rays to light using radiographic screens coated with various fluorescent materials and recording the resulting light images using specially manufactured photographic films. It is possible to directly expose photographic film with x-rays, but because film is very inefficient in absorbing x-rays, direct radiography would result in unsafe levels of exposure and is unsuitable for medical use. By the first decade of the 21st Century, most film-based radiographic systems and fluoroscopic systems, which had employed video technology for recording and storing examinations, moved to the use of filmless digital detector and recording systems. The digital images generated by modern imaging system offer a variety of advantages over the now obsolete film based systems. Because they are digital, these images can be efficiently stored, transmitted and retrieved using sophisticated computer networks called Picture Archiving and Communications Systems (PACS). These systems allow the diagnostic images to be transmitted for review and interpretation to medical facilities anywhere around the world. The move away from film to digital radiology systems has also resulted in a significant reduction in the space needed to store the increasing numbers of medical images and the number of personnel required to manage physical “film libraries” or “archives” radiology departments. Significant environmental benefits were realized by the move to digital imaging, primarily as a result of the elimination of potentially harmful chemicals and waste products that were a part of the processes used to develop and stabilize vast numbers of radiographic films. Using computer-based image processing techniques, it is possible to enhance digital radiographic images to make diagnostic features more apparent and to suppress features of an image that might obscure a diagnostic finding. Finally, using even more advanced processing techniques, it is possible to use a series of radiographic images obtained as the x-ray detector and tube moves relative to the patient to create a “volumetric data set” that the computer system can render as a three-dimensional image of the organ of interest.
.
CTThe early 1970s saw a major advance in medical imaging with the development of a technology called Computed Axial Tomography--the CATscan. CAT images were generated by detecting the changes in the intensity of a thin, fan-shaped (collimated) beam of x-rays as the x-ray tube and/or x-ray detector array rotates around a patient, producing multiple “axial” projections of x-ray data at slightly different angles. Using sophisticated computer software and processing techniques, these data can be used to generate an axial, cross-sectional image of the body. By incrementally moving the patient slightly toward their head or their feet between data acquisitions, a stack of , multiple thin slices or “sections” (similar to a building section) can be created of any part of the human body. CAT scans are much more sensitive to the slight variations in the ability of differing tissues to block the x-ray beam. Moreover, the cross-sectional rendering of the relationships of the internal structures make it easier to spotCT Imagediagnostic abnormalities as compared to conventional radiography. Further technological innovations in scanner design and manufacturing have now made it possible to obtain data from three dimensional volumes, rather than limited axial slices of tissue. Thus, it is now possible to obtain two dimensional cross-sectional images in any plane of projection and to generate three-dimensional renderings of the volumetric data. In recognition that computed tomography is no longer limited to generating axial imaged, the technique is now commonly referred to as “CT” scanning.
.
CT exams have been some of the most rapidly growing imaging procedures performed in the United States. Almost one in five patients seen in an emergency service will have a CT. However, volumetric, multislice CT scanning results in significantly higher levels of x-ray exposure for patients as compared to earlier techniques. Recently major concerns have been raised regarding the total level of radiation to which a patient is exposed, particularly when pediatric patients are involved.
.
In addition to CT technology, there has been an explosion of new imaging modalities, as illustrated in the following graph. We will provide a brief overview of the major new equipment and processes.






CT SummaryEvolution of imaging

Magnetic Resonance Imaging
.
Following on the heels of the CT revolution came a completely different imaging modality – magnetic resonance imaging (MRI). This technology is based on the behavior of sub atomic particles (protons) in our body in response to changes in the magnetic fields to which they are exposed. Fortunately protons are particularly abundant in the human body in the form of the nuclei of hydrogen atoms. Because a proton is a spinning electrical charge, each proton generates a tiny magnetic field—they are basically subatomic compass needles. By placing a patient in a very powerful magnetic field, the protons align their magnetic fields with the external field. When the protons are exposed to a radiofrequency energy “pulse” of an appropriate frequency, the protons tend to move out of alignment with the external field. When the radio frequency pulse is turned off, the protons “relax,” or return to alignment with the external field, emitting a radio frequency signal in the relaxation process. These radio frequency emissions are detected, recorded, and processed to produce computer generated images of the anatomic structures of interest. In addition to anatomic images, MRI techniques can be used to probe the changes in the molecular content of tissues that can result from various diseases. Thus MRI can provide anatomic, physiologic, and metabolic information about the human body in health and disease. MRI is extensively used in the diagnosis and treatment of cancer and heart disease, and for analysis of brain structure and function. A major benefit of MRI is that it does not use ionizing radiation such as x-rays, therefore eliminating the risks of x-ray exposure.
.
Because MRI systems rely on massive magnets to generate the necessary stable external magnetic fields that are many times stronger than that of the earth, they are extremely heavy and they have complex design requirements. Due to their size and complexity, MRI systems are frequently the most expensive imaging devices to install and maintain. Most MRI systems require that patients be placed into a very small tunnel (known as the bore) within the magnet. The confined space within the bore of the magnet often results in claustrophobia and stress for the patient. Beyond patient comfort and stress considerations, there are several major safety considerations in the design of MRI facilities. These include the need to control, or shield, the magnetic field so that objects outside the imaging suite are not affected and that the uniformity of the field within the bore of the magnet is not affected by changes in the external environment. Due to the need to pulse and measure radio frequency emissions with great accuracy, the MRI unit must also be shielded from external sources of radiofrequency energy. MRI shielding requires careful analysis of the unit’s location and equally careful design, specification and installation of radiofrequency shielding.
There is also the need to prevent the ferrous material from entering the examination room. The magnets used in MRI are so strong that non-constrained ferrous object will be drawn into the magnet’s bore with such force that it is virtually impossible to stop. There have been tragic accidents involving medical gas cylinders, monitoring devices, office chairs, guns and other objects being drawn into the bore of a magnet. In several instances these mishaps have occurred during a procedure, resulting in injury and, in some cases, death of the patient.
.
MRI SummaryMRI Image
.
Many MRI systems, especially the “high field strength” systems that can produce exquisitely detailed images that are suitable for techniques such as tissue spectroscopy, incorporate superconducting magnets to generate the uniform field in the magnet’s bore. Superconducting magnets function at the extremely low temperatures produced by cooling systems that use cryogens such as liquid nitrogen or liquid helium. In the normal course of operation, some of the liquid cryogen evaporates as its gas form which occupies more volume than in the liquid state. Consequently, superconducting systems must provide for adequate venting of cryogenic gases to prevent the build up of dangerous pressure levels in the cooling system or the displacement of room air from the suite with the attendant risk of asphyxiation of patients and personnel. In addition, in the event of a cooling system or power failure, the temperature of the magnet can rapidly increase to the point that the superconducting coil becomes a resistive (heating) coil—an event referred to as “quenching”. Quenching results in the rapid vaporization of large amount of cryogen, and unless there is adequate provision for venting of the resulting gases, explosion of the magnet can occur. Even when adequate venting is provided, care must be taken to assure that the vents do not become blocked or otherwise interrupted during installation, remodeling or de-installation.
.
Ultrasound
.
Radiography, fluoroscopy, CT and MRI all are based on the use of electromagnetic energy, x-ray in the first three instances and radio waves in the case of MRI. One imaging modality that does not use either is ultrasound. In ultrasound, or sonography, the imaging process is based on the interactions of very high frequency sound waves of between 3.5 and 15 million cycles per second (megahertz) within the soft tissues. The acoustical energy detected by the ultrasound probe after a pulse of high sound waves are scattered or reflected by the internal structures of organs and tissues is processed to form two or three-dimensional images of internal structures. The higher the frequency of the ultrasound beam used to generate the image, the better the ability to detect small structures (higher spatial resolution) but the shorter the depth of penetration into the tissues. Consequently, sonographicimaging is highly dependent on the skill of the operator in matching the need for structural detail with the need for depth by adjusting the selection of probe frequency with the particulars of patient body type and the diagnostic question at hand. Sonographic images (while cross-sectional in the same way as CT or MRI) are very different in their appearance, making their interpretation less intuitive until significant experience is gained with the technique.
.
Ultrasound EquipmentSonography’s major advantage is the elimination of the use of ionizing radiation and the associated risks to the patient. Ultrasound examinations can be recorded and viewed either as a series of static images or as real-time digital video. One of the most common uses of ultrasound is in obstetrical imaging where use of x-ray based methods would pose a risk to the developing fetus. Ultrasound is also frequently used to evaluate abdominal pain, to image blood vessels for areas of atherosclerosis or narrowing, and to evaluate the function of the heart and its valves. The ability to view sonographic “movies” at the bedside has made the technique particularly useful in guiding interventional and surgical procedures.
.
Ultrasound units are small, mobile, and relatively inexpensive compared to equipment used for other imaging modalities. The ultrasound systems used for evaluation of the heart are generally referred to as echocardiographic units. Many sonographic systems can measure the velocity and direction of blood flow based on subtle shifts in the frequency of the sound waves reflected by the cellular components of the blood moving through the arteries and veins. The frequency shifts are due to the Doppler effect with which we are all familiar—the apparent decrease in pitch of the sound of a car horn or train whistle as they pass.
.
Nuclear Medicine
.
Radiographic techniques rely on the detection of changes in intensity of x-rays as they pass through the body. In contrast, Nuclear Medicine imaging techniques rely on the detection of various forms of radiation emitted by radioactive isotopes that are injected, ingested or otherwise administered internally to the patient. Depending on the isotope used and the route of administration the emitted radiation can be detected and processed into images by a number of different devices including gamma cameras, single photon emission computed tomography (SPECT) scanners, and positron emission tomography (PET) scanners. A major advantage of this technique is that radioactive isotopes can be chemically bound to molecules that are selectively taken up by specific tissues or organs, providing the ability to identify localized abnormalities in the body’s handling (metabolism) of these molecules. While the anatomic detail of most nuclear medicine techniques is lacking as compared to CT or MRI, nuclear medicine’s strength lies in the ability to provide information about metabolic and physiologic processes. In addition, certain isotopes can be administered for the treatment of conditions such as hyperthyroidism or certain forms of cancer. In fact, one of the most common applications of nuclear medicine imaging is for the detection and monitoring of cancer.
Nuclear Medicine
.
Because many of the isotopes are short lived, because chemical processing is involved in binding the isotopes to the desired carriers (a process called labeling), and because the isotopes and labeled molecules will be administered internally to patients, there are special requirements for the storage and compounding of radioactive materials. These requirements must be met either by incorporating a nuclear medicine pharmacy in the design of the imaging facility or by contracting for radiopharmaceutical services. In addition, special provisions must be made to assure that radioactive materials are properly housed, that unused isotopes are appropriately disposed of, and that inadvertent contaminations or “spills” of radioactive materials are appropriately cleaned up. In some cases, patients receiving particularly high doses of radioactive isotopes must be temporarily isolated to prevent inadvertent exposure of personnel and family members.
.
Recently new imaging systems that combine multiple imaging modalities have been developed. Systems combining CT, and more recently MRI with positron emission tomography (PET) are now widely used, especially in the imaging of cancer. These hybrid systems are powerful tools that can provide precise anatomic localization of tumors while at the same time also providing information about the rate of physiologic uptake and turnover of compounds used in tumor growth and cell division.
MRI

Angiographic procedures

Angiographyorarteriographyis animagingtechnique used to visualize the heart and blood vessels of the body, with particular interest in thearteries, veinsand the heart chambers. Angiography is performed by injecting a radio-opaquecontrast agentinto the blood vessel and recording a series of radiographic or fluoroscopic images as the contrast material is carried through the length of the vessel. Two common applications of angiography are for the diagnosis and treatment of cardiac conditions, particularly coronary artery disease, and peripheral vascular disease.
.
The simplest angiographic systems typically incorporate an x-ray tube and its associated detector units mounted 180o from one another at either end of a c-shaped gantry, or “c-arm,” that can be freely positioned, rotated and angled with respect to the examination table. This allows images to be obtained in a fashion that best demonstrates the structures of interest. More complex angiographic systems may add a second c-arm unit that can be independently positioned so imaging can be obtained in two different projections with a single injection of contrast. Such complex, biplane angiographic systems are usually used in subspecialty applications such as neuroradiology, interventional or cardiac angiographic suites , or when imaging is performed on children who might not be able to remain still during an imaging procedure. In most facilities, angiographic studies of the heart and coronary arteries are typically done by cardiologists in specially designed cardiac catheterization laboratories operated within departments of cardiology separate from radiology departments. For the management of aortic and peripheral vascular disease, it is quite common that teams of physicians including radiologists and vascular and cardiothoracic surgeons to collaborate in angiographic procedures.
.
Angiography roomAngiographic studies of the arterial system generally start with a needle puncture in the groin to access the common femoral artery. Once access is obtained, a guidewire is passed through the needle. The needle is then removed and replaced over the wire by a flexible catheter which can be advanced into the more central portions of the arterial tree and finally into the aorta, the main artery that supplies blood to all body organs except for the lungs.
.
Beyond simply visualizing arteries and veins, it is common to use angiographic images as “roadmaps” while using specialized guidewires and catheters to study smaller vessels such as the coronary arteries of the heart or carotid arteries of the head and neck. One common application of these techniques is in the treatment of areas of vascular narrowing, or stenosis. Once an area of narrowing is identified and fully evaluated using multiple planes of projection, an attempt can be made to pass a guidewire and catheter through the narrowed segment. If the narrowing can be successfully crossed, special balloon tipped catheters can be used to perform an “angioplasty”- or dilation of the narrowed segment. If need be, specially designed wire mesh tubes called “stents” can also be placed in order to hold the narrowed segment open. Angioplasty and stenting have replaced much more expensive, higher risk, surgical techniques for the treatment of stenosis of the coronary arteries, peripheral arteries of the legs and arms, and carotid arteries for many patients.


Interventional Radiology
.
Space considerations

The design of imaging departments is one of the most challenging areas in a hospital of healthcare facility architecture because of: 1.) the range of imaging modalities; 2.) the diversity of imaging procedures and interventions, some of which must be performed under operating room conditions; 3.) the complexity of the site planning, installation and support for modern imaging systems; 4.) the mix of patients including both inpatients and outpatients; and 5.) the need to provide imaging services in settings that are safe, welcoming and supportive of patients, their families and facility personnel. Most hospitals manage both inpatients and outpatients in the same area. This makes access for ambulatory patients a major consideration. Some services, such as the emergency department, frequently require immediate images of high risk trauma patients, requiring either close proximity to the emergency service, or separate imaging equipment located within the ED.

Layout


Accommodating shifts in technology between imaging and surgery, and the accommodation of new imaging modes, such as hybrid operating rooms, has resulted in modular, interchangeable rooms, and “interventional platforms”, in which interventional imaging rooms and surgical operating rooms are co-located within a common area. This will be discussed in more detail in the next section.










August 20, 2012, 4:02 pm

Medical Radiation Soars, With Risks Often Overlooked

By JANE E. BRODY Radiation, like alcohol, is a double-edged sword. It has indisputable medical advantages: Radiation can reveal hidden problems, from broken bones and lung lesions to heart defects and tumors. And it can be used to treat and sometimes cure certain cancers.
But it also has a potentially serious medical downside: the ability to damage DNA and, 10 to 20 years later, to cause cancer. CT scans alone, which deliver 100 to 500 times the radiation associated with an ordinary X-ray and now provide three-fourths of Americans' radiation exposure, are believed to account for 1.5 percent of all cancers that occur in the United States.
Recognition of this hazard and alarm over recent increases in radiological imaging have prompted numerous experts, including some radiologists, to call for more careful consideration before ordering tests that involve radiation.
"All imaging has increased, but CTs account for the bulk of it," said Dr. Rebecca Smith-Bindman, a specialist in radiology and biomedical imaging at the University of California, San Francisco. "There's clearly widespread overuse. More than 10 percent of patients each year are receiving very high radiation exposures."
The trick to using medical radiation appropriately, experts say, is to balance the potential risks against known benefits. But despite the astronomical rise in recent years in the use of radiation to obtain medical images, this balancing act is too often ignored. The consequences include unnecessary medical costs and risks to the future health of patients.
Both doctors and patients have a responsibility to better understand the benefits and risks and to consider them carefully before doctors order and patients undergo a radiation-based procedure.
Patients may be surprised to learn that some of the newest uses of radiological imaging, including CT scans of coronary arteries to look for calcium buildup, have not yet been tested in scientifically designed clinical trials, and thus their true benefits are at best a guess. Experts have estimated that widespread use of coronary artery scans, which deliver 600 times the radiation of a chest X-ray, could result in 42 additional cases of cancer for every 100,000 men who have the procedure, and 62 cases for every 100,000 women who do.
For every 1,000 people undergoing a cardiac CT scan, the radiation adds one extra case of cancer to the 420 that would normally occur. This risk may seem inconsequential, but not to someone who gets a cancer that could have been prevented.
Complicating the matter is the enormous variation - sometimes tenfold or more - in the amounts of radiation to which patients are exposed from the same procedure at different institutions, or even at the same institution at different times.
Although the cancer-causing effects of radiation are cumulative, no one keeps track of how much radiation patients have already been exposed to when a new imaging exam is ordered. Even when patients are asked about earlier exams, the goal is nearly always to compare new findings with old ones, not to estimate the risks of additional radiation.
As Dr. Michael S. Lauer of the National Heart, Lung and Blood Institute wrote in The New England Journal of Medicine three years ago, "The issue of radiation exposure is unlikely to come up because each procedure is considered in isolation, the risks posed by each procedure are low and seemingly unmeasurable, and any radiation-induced cancer won't appear for years and cannot easily be linked to past imaging procedures."
After an extensive review of the environmental causes and risk factors for breast cancer, the Institute of Medicine reported last year that sufficient evidence of risk was found only for combined hormone therapy used by postmenopausal women and exposure to ionizing radiation, at doses much higher than those received during a mammogram.
Everyone is exposed to a certain amount of background radiation - about three millisieverts a year from cosmic rays, radon gas and the earth's radioactive elements. By 1980, according to The Harvard Health Letter, various introduced sources, like medical tests, nuclear power plants, nuclear fallout, television sets, computer monitors, smoke detectors and airport security scanners, added another 0.5 millisieverts per year.
Now, however, the amount of radiation used medically rivals that of the background radiation, adding three millisieverts each year to the average person's exposure. (A mammogram involves 0.7 millisieverts, a dose that is doubled with a 3-D mammogram.)
There are many reasons for this increase. Doctors in private practice who have bought imaging equipment tend to use it liberally to recoup the expense. The same goes for hospitals just a few miles apart that needlessly duplicate certain equipment so they can boast of having the latest and greatest capacity to detect disease. Doctors ordering tests suffer no adverse effects, and patients feel they are getting the most that modern medicine can offer.
Dr. Lauer wrote in a commentary about cardiac tests, "Most physicians who order imaging tests experience no consequences for incurring costs for procedures of unproven value. On the contrary, they or their colleagues are paid for their services, and their patients don't complain because the costs are covered by third parties. Patients are pleased to receive thorough evaluations that involve the best cutting-edge technologies."
According to a new study, the rise in medical imaging clearly goes beyond financial motives. Dr. Smith-Bindman and her colleagues reported in June in The Journal of the American Medical Association that a dramatic rise in imaging rates from 1996 to 2010, including a tripling of CT scans, occurred in six large prepaid health systems where the financial incentive ought to have encouraged fewer, not more, tests. The increased testing doubled the proportion of patients who received high or very high radiation exposures.
By 2010, the researchers reported, 20 CT scans were performed for every 100 adult patients; for every 100 patients ages 65 to 75, about 35 CT scans were done. And among the 10 to 20 percent of children in the study who underwent a single CT scan of the head, radiation doses were in the range previously shown to triple the risk of later developing brain cancer or leukemia.
Dr. Smith-Bindman urged patients to participate in the decision to undergo medical imaging. She said, "Patients should ask, 'What is this test for? Do I need it? Why? Do I need it now?' "
Legislation can help curtail, or at least monitor, radiation doses, she said, citing a California law that took effect in July requiring that the dose used for CT scans be recorded in every patient's medical record and that inadvertent overdoses be reported to the state immediately.
If such recording were to become a national mandate, electronic medical records could help doctors and patients keep track of radiation exposures and provide further incentive to avoid unnecessary imaging.
Sidebar: Limiting the Fallout of Cancer Treatment
Radiation therapy to treat cancer depends on much higher doses than are used in imaging, and these treatments have long been known to increase a patient's risk of later developing another cancer. Doctors consider this risk of radiation therapy reasonable when the goal is to prevent death from the original cancer.
Last year in a report in The Lancet Oncology, researchers from the National Cancer Institute and M.D. Anderson Cancer Center in Houston reported that among 647,672 adult cancer patients treated five or more years earlier, about 8 percent developed a second cancer years later related to radiation treatment of the first cancer. More than half of the second cancers occurred in survivors of breast and prostate cancers.
As expected, the risk of developing a second cancer was highest among those originally treated at younger ages and most often involved organs exposed to the highest doses of radiation.
In recent years, radiologists have taken great pains to limit radiation exposure to nontarget organs - for example, by using a cone beam when treating breast cancer - which should reduce the risk of radiation-induced second cancers. Contributors to this section include Stefan Novosel, Kate Renner, Andrew Petty and Frank Zilm

All forms of medical imaging are handled by the radiology department of hospitals. The field of radiology (also called medical radiography) began in 1895 when Wilhelm Conrad Roentgen discovered x-rays. Soon this form of electromagnetic radiation was applied for diagnostic purposes in medical care. Eventually specialists, called radiologists, were trained and employed specifically for the handling of such technology and the interpretation of the images produced. The services performed by radiologists grew with the development of other x-ray based technologies, including fluoroscopy and computed tomography (CT). As other medical imaging technologies that depend on other energy forms than x-rays were developed, such as ultrasound and magnetic resonance imaging (MRI), they also came under the scope of the radiologists' work. The different imaging techniques have various resolution abilities, relevant target structures in the body, hazards to patients and costs, making the professionals trained specifically to produce and interpret these images valuable for almost any medical facility. Today, medical imaging daily provides information critical to diagnosis, guiding procedures, monitoring treatments and effectively communicating with patients, their families and other medical staff.

References and Resources:

The Architecture of Medical Imaging: Designing Healthcare Facilities for Advanced Radiological Diagnostic and Therapeutic Techniques, Rosternberg, Bill, John Wiley & Son, 2006
"Designing a Facility for People, Not Just the Equipment,"Leaper, Christine, Radiology Today, February 7, 25. pages 18-20
"'Surgology' is Coming," Rostenberg, Bill, Health Facilities Management Magazine, June 2005, pages 49-52
Diagnostic Imaging Magazine