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Radiology

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.

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.

Commonly used imaging modalities include X-ray, 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 are often used to for quick evaluation of bony structures.
Fluoroscopy is a special application of X-ray imaging, where an X-ray video
camera allows the imaging of structures in motion. Often, contrast materials
(chemicals which are absorb X-ray photons and can be easily seen on X-ray
films) are injected, swallowed, or administered into the body in other ways
to help visualize dynamic processes, such as the motion of the digestive tract.

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 in the process.

Ultrasound imaging uses high-frequency sound waves to vizualize soft tissue
structures in the body in real time. No radiation is involved, but this
imaging modality is highly dependent on the skills of the person performing
the exam.

MRI uses strong magnetic fields to align spinning hydrogen protons within
body tissues, then disturbs the axis of rotation of these protons and
measures the electrical currents generated as the protons 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. The downside of it
is that the patient has to hold still for long periods of time in noisy,
cramped quarters while the imaging is performed.

Nuclear medicine imaging involves the administration into the patient of
substances labelled with radioactive tracers which have affinity for
particular tissues. The heart, lung, thyroid, liver/gallbladder, and bones
are commonly evaluated for particular conditions using these techniques.
Anatomical detail is limited in these studies, but processes such as the
growth of a tumor can often be seen this way when all other methods fail.

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