The most common imaging technique used today is a radiograph (x-ray film) and the most common x-ray ordered is a chest x-ray, and the musculoskeletal x-ray exam comes in second. An x-ray provides a two dimensional image of the interior of the body and the procedure is performed by a Radiologic Technologist. A single x-ray passes through the body and exposes the film on a radiograph (or fluorescent screen) placed on the opposite side. Tissues having different densities show up as differing densities on the radiograph i.e. x-rays which have there nature of being absorbed to various degrees through body tissues depending on the density of them.
There are four fundamental radiographic densities. This is how they may appear on the fluorescent screen: Air and gases appear black or radiolucent. Fat appears gray to black. Muscles and water appear grey. Bones and calcium appear white, or radiopaque. A tissue that is more dense absorbs more x-rays than tissues that are less dense. Radiopaque is a very dense tissue and a less dense tissue is said to be radiolucent. Bone is very dense and fat is moderately dense while other tissues are least dense. It is important to differentiate between two types of densities that are physical density and radiographic densities. The radiographic density of a substance is related to it’s physical density-
In CT Scanning, x-rays moves in an arch around the part of the body being observed through a laser-like beam. The beams of x-rays passed through the region of the body imaged are collected by a special detector which converts the x-rays into electronic pulses that produce readings of the density of the tissue into a 1cm slice of the body. From these readings a computer can assemble a picture of the body called a CT Scan that can be viewed on a fluorescent screen, then photographed for later examinations. CT scan stands for computerized tomography. It obtains parts of the body that can’t be seen on a standard x-ray with the help of computer algorithms in conjunction with the enhanced x-ray technology.
MRI uses the magnetic properties of the hydrogen nucleus, which is excited by radio frequency radiation transmitted by a coil surrounded by the body part. When placed in strong magnetic fields, the nuclei of certain atoms absorb radio frequencies beamed at them and then emit their own radio frequency waves. This process allows MRI Tech’s and physicians to see very clear pictures of the inside of the body including tissues, organs, and blood vessels. MRI is a noninvasive technique that does not use ionizing radiation. MRI has become one of the primary tools used to image the brain, spinal cord, major blood vessels, and several key organs. The images can be produced in 3-D, which significantly enhances the physician’s ability to diagnose problems. MRI Technicians are also used to help view the process of surgery in real time in 3-D, which assists with a whole host of surgical procedures.
CT Scans are an advanced form of x-ray technology used in detecting diseases in soft body tissues and can actually provide images of internal organs that are impossible to detect with standard x-ray techniques. X-Ray’s are good at finding bone fractures and for being used as a contrasting agent for several types of exams; however, the CT provides greater detail and clarity. CT scan has additional advantages of being able to produce imaging in virtually any orientation. It is a more technologically developed version of an x-ray, which is used on specific parts of the body. It also provides better images for bone structures, inner ear as it can easily detect tumors in the auditory canal and cochlea. CT Scans help diagnose bone fractures, bone tumors, internal injuries and bleeding and blood clots and to monitor heart diseases and cancer.
MRI uses magnetic waves to produce images while CT images are produced using x-rays. MRI provides more details of bony structures compared to CT Scan. CT Scans can’t help much in seeing clearly very fine soft tissue details as in the shoulder or knee compared to MRI. MRI scans are best for imaging soft tissue. CT scans are much more costly and takes a longer time (30 minutes) to be completed compared to a MRI which can take less time to complete. People with surgical clips, metallic fragments, cardiac monitors and pace makers cannot have an MRI scan. Also pregnant women should not have CT scans. MRI machines can produce in any plane without moving the patient. They also have the ability to change the contrast of the images making them more clear than CT scan.