| Patients have the following procedures to provide | | | | be found via ultrasound before it dislodges and |
| images for Radiological decisions to be made. | | | | travels to the brain (creating a stroke), heart |
| Projection radiography | | | | (creating coronary blockage), or lungs (pulmonary |
| Radiographs (or Roentgenographs, named after | | | | embolism), all of which are fatal if left untreated. |
| the discoverer of X-rays, Wilhelm Conrad | | | | Ultrasound is useful for image-guided interventions |
| Roentgen (1845-1923)) are often used for | | | | like biopsies and drainages such as thoracentesis). |
| evaluation of bony structures and soft tissues. An | | | | It is also used in the treatment of kidney stones |
| X-Ray machine directs electromagnetic radiation | | | | (renal lithiasis) via lithotripsy. Small portable |
| upon a specified region in the body. This radiation | | | | ultrasound devices now replace peritoneal lavage |
| tends to pass through less dense objects (skin, | | | | in the triage of trauma victims by directly |
| fat, muscle, and other tissues), but is absorbed by | | | | assessing for the presence of hemorrhage in the |
| denser materials (bones, tumors, lungs affected | | | | peritoneum and the integrity of the major viscera |
| by severe pneumonia). Radiation which has passed | | | | including the liver, spleen and kidneys. Extensive |
| through a patient then exposes an x-ray film. | | | | hemoperitoneum (bleeding inside the body cavity) |
| Areas of film exposed to higher amounts of | | | | or injury to the major organs may require |
| radiation will appear black or dark gray after | | | | emergent surgical exploration and repair. |
| development. The unexposed areas of film remain | | | | MRI/NMR |
| white. | | | | MR image of human kneeMRI uses strong |
| Fluoroscopy | | | | magnetic fields to align spinning atomic nuclei |
| Fluoroscopy and angiography are special | | | | (usually hydrogen protons) within body tissues, |
| applications of X-ray imaging, where a fluorescent | | | | then uses a radio signal to disturb the axis of |
| screen or image intensifier tube is connected to a | | | | rotation of these nuclei and observes the radio |
| closed-circuit television system, which allows | | | | frequency signal generated as the nuclei return to |
| real-time imaging of structures in motion or | | | | their baseline states. MRI scans give the best soft |
| augmented with a radiocontrast agent. | | | | tissue contrast of all the imaging modalities. With |
| Radiocontrast agents are administered, often | | | | advances in scanning speed and spatial resolution, |
| swallowed or injected into the body of the | | | | and improvements in computer 3D algorithms and |
| patient, to help delineate anatomy such as the | | | | hardware, MRI has great potential for |
| blood vessels, the genitourinary system or the | | | | development in the next few years. One |
| gastrointestinal tract. Specific radiocontrast agents | | | | disadvantage is that the patient has to hold still |
| are used for specific types of evaluations; for | | | | for long periods of time in a noisy, cramped space |
| example, barium in a suspension is administered | | | | while the imaging is performed. Recent |
| into the gastrointestinal tract and imaged with | | | | improvements in magnet design like wider, shorter |
| fluoroscopy or radiography. Radiocontrast agents, | | | | magnet bores and more open magnet designs, |
| which strongly absorb X-ray radiation, in | | | | have brought some relief for claustrophobic |
| conjunction with the real-time imaging allows | | | | patients. MRI has great benefit in imaging the |
| demonstration of dynamic processes, such as | | | | brain,spine, and musculoskeletal system. The |
| peristalsis in the digestive tract or blood flow in | | | | modality can be contraindicated for patients with |
| arteries and veins. | | | | pacemakers, certain types of cerebral aneurysmal |
| CT scanning | | | | clips or metallic hardware due to the strong |
| CT imaging uses X-rays in conjunction with | | | | magnetic fields. Areas of potential advancement |
| computing algorithms to image a variety of soft | | | | include functional imaging, cardiovascular MRI, as |
| tissues in the body. CT is acquired in the axial | | | | well as MR image guided therapy. |
| plane, while coronal and sagittal images can be | | | | Nuclear medicine |
| rendered by computer reconstruction. | | | | Nuclear medicine imaging involves the |
| Radiocontrast agents are often used with CT for | | | | administration into the patient of substances |
| enhanced delineation of anatomy. Intravenous | | | | labelled with radioactive tracers which have |
| contrast allows 3D reconstructions of arteries and | | | | affinity for particular tissues. The heart, lungs, |
| veins. Although radiographs provide higher | | | | thyroid, liver, gallbladder, and bones are commonly |
| resolution for bone X-rays, CT can generate | | | | evaluated for particular conditions using these |
| much more detailed images of the soft tissues. | | | | techniques. While anatomical detail is limited in |
| CT exposes the patient to more ionizing radiation | | | | these studies, nuclear medicine is useful in |
| than a radiograph. | | | | displaying physiological function. As such, |
| Ultrasound | | | | processes such as the growth of a tumor can |
| Medical ultrasonography uses ultrasound | | | | often be monitored, even when the tumor cannot |
| (high-frequency sound waves) to visualize soft | | | | be adequately visualized using any of the other |
| tissue structures in the body in real time. No | | | | modalities. The principal imaging device is the |
| ionizing radiation is involved, but the quality of the | | | | gamma camera which detects the radiation |
| images obtained using ultrasound is highly | | | | emitted by the tracer in the body and displays it |
| dependent on the skill of the person | | | | as an image. Often the information is converted |
| (ultrasonographer) performing the exam. The use | | | | into a series of slices through the body. In the |
| of ultrasound in medical imaging has developed | | | | most modern devices Nuclear Medicine images |
| mostly within the last 30 years. The first | | | | can be fused with a CT scan taken |
| ultrasound images were static and two | | | | quasi-simultaneously so that the physiological |
| dimensional (2D), but with modern-day | | | | information can be overlayed on co-registered |
| ultrasonography 3D reconstructions can be | | | | with the anatomical structures to improve |
| observed in real-time; effectively becoming 4D. | | | | diagnostic accuracy. |
| Because ultrasound does not utilize ionizing | | | | PET scanning also falls under "nuclear medicine." |
| radiation, unlike radiography, CT scans, and nuclear | | | | The applications of nuclear medicine can include |
| medicine imaging techniques, it is generally | | | | bone scanning which traditionally has had a strong |
| considered safer. For this reason, this modality | | | | role in the work-up/staging of cancers. Myocardial |
| plays a vital role in obstetrical imaging. Fetal | | | | perfusion imaging is a sensitive and specific |
| development can be thoroughly evalauted allowing | | | | screening exam for reversible myocardial |
| early diagnosis of fetal anomalies or confirmation | | | | ischemia, which when present requires |
| of a normal gestation. Color flow Doppler well | | | | angiographic confirmation and potentially life-saving |
| documents the severity of peripheral vascular | | | | balloon angioplasty, stenting or cardiac bypass |
| disease. Stenosis of the carotid arteries can herald | | | | grafting. Molecular Imaging is the new and exciting |
| cerebral infarcts (strokes). A DVT in the legs can | | | | frontier in this field. |