|
Radiology is the branch of medical science dealing with the
medical use of x-ray machines or other such radiation devices. It is also the examination of the inner structure of opaque objects using X rays or other penetrating radiation.
Subdivisions
As a medical specialty, radiology can be classified into two subfields. Diagnostic radiology is concerned with the use of various imaging modalities to aid in the diagnosis of disease. Interventional radiology uses these imaging modalities to
guide minimally invasive surgical procedures.
Radiation therapy uses radiation to treat diseases such as
cancer and is commonly lumped together in the same class as Radiology. Most medical practitioners, however, make a clear
distinction between the Radiologists and the Radiotherapists.
Diagnostic radiology
Commonly used imaging modalities include plain radiography, computed tomography (CT), magnetic
resonance imaging (MRI), ultrasound,
and nuclear imaging techniques. Each of these modalities has
strengths and limitations which dictate its use in diagnosis.
X-rays
Radiographs are often used to for quick evaluation of bony structures. Fluoroscopy, angiography and barium contrast
studies are special applications of X-ray imaging, where an X-ray video camera
allows the imaging of structures in motion or augmented with a contrast agent. Often, chemicals are injected, swallowed or
otherwise administered into the body of the patient to help delineate certain parts of the body such as the blood vessels and
gastrointestinal tract. These contrast
materials, which strongly absorb X-ray radiation, also help in the visualization of dynamic processes, such as the motion of
the digestive tract.
CT scanning
CT imaging uses X-rays in conjunction with
computing algorithms to image a variety of soft tissues in the body. X-ray contrast is often used with CT as well. CT can
generate much more detailed images than plain X-rays, but exposes the patient to more ionizing radiation.
Ultrasound
Ultrasound imaging uses high-frequency sound waves to vizualize soft tissue
structures in the body in real time. No radiation is involved, but the quality of the images obtained using ultrasound is highly
dependent on the skill of the person performing the exam.
MRI/NMR
MRI uses strong magnetic fields to align spinning atomic nuclei (usually hydrogen protons) within body tissues, then disturbs the axis of rotation of
these nuclei and observes the radio frequency signal generated as the
nuclei return to their baseline states. MRI scans give the highest resolution and definition of all the imaging modalities. With
advances in scanning speed and resolution and improvements in computer 3D algorithms and hardware, MRI appears to have the
greatest potential for development in the next few years. Its disadvantage is that the patient has to hold still for long periods
of time in a noisy, cramped space while the imaging is performed.
Nuclear medicine
Nuclear medicine imaging involves the administration into the
patient of substances labelled with radioactive tracers which have affinity for particular tissues. The heart, lungs, thyroid,
liver, gallbladder, and bones are
commonly evaluated for particular conditions using these techniques. While anatomical
detail is limited in these studies, nuclear medicine is useful in displaying physiological function. As such, processes such as the growth of a tumor
can often be monitored this way, even when the tumor cannot be adequately visualized using any of the other modalities.
External links
|