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Monday, June 29, 2009

Computed Tomography (CT) SCAN

Computed Tomography (CT) SCAN:




=>A CT or CAT scan is a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, organs, and blood vessels. CT scans are more detailed than standard x-rays.

=>In standard x-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue.

=>In computed tomography, the x-ray beam moves in a circle around the body. This allows many different views of the same organ or structure, and provides much greater detail. The x-ray information is sent to a computer that interprets the x-ray data and displays it in 2-dimensional form on a monitor. Newer technology and computer software makes three-dimensional (3-D) images possible.

=>CT scans may be done with or without contrast. "Contrast" refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your physician will notify you of this prior to the procedure.

=>CT scans may be performed to help diagnose tumors, investigate internal bleeding, or check for other internal injuries or damage.


ADVANCES:

Advances in computed tomography technology include the following:

  • high-resolution computed tomography
    This type of CT scan uses very thin slices (less than one-tenth of an inch), which are effective in providing greater detail in certain conditions such as lung disease.
  • helical or spiral computed tomography
    During this type of CT scan, both the patient and the x-ray beam move continuously, with the x-ray beam circling the patient. The images are obtained much more quickly than with standard CT scans. The resulting images have greater resolution and contrast, thus providing more detailed information.
  • ultrafast computed tomography (also called electron beam computed tomography)
    This type of CT scan produces images very rapidly, thus creating a type of "movie" of moving parts of the body, such as the chambers and valves of the heart. This scan may be used to obtain information about calcium build-up inside the coronary arteries of the heart.

USAGE:

CT imaging is:

  • one of the best and fastest tools for studying the chest, abdomen and pelvis because it provides detailed, cross-sectional views of all types of tissue.
  • often the preferred method for diagnosing many different cancers, including lung, liver and pancreatic cancer, since the image allows a physician to confirm the presence of a tumor and measure its size, precise location and the extent of the tumor's involvement with other nearby tissue.
  • an examination that plays a significant role in the detection, diagnosis and treatment of vascular diseases that can lead to stroke, kidney failure or even death. CT is commonly used to assess for pulmonary embolism (a blood clot in the lung vessels) as well as for abdominal aortic aneurysms (AAA).
  • invaluable in diagnosing and treating spinal problems and injuries to the hands, feet and other skeletal structures because it can clearly show even very small bones as well as surrounding tissues such as muscle and blood vessels.

Physicians often use the CT examination to:

  • quickly identify injuries to the lungs, heart and vessels, liver, spleen, kidneys, bowel or other internal organs in cases of trauma.
  • guide biopsies and other procedures such as abscess drainages and minimally invasive tumor treatments.
  • plan for and assess the results of surgery, such as organ transplants or gastric bypass.
  • stage, plan and properly administer radiation treatments for tumors as well as monitor response to chemotherapy.
  • measure bone mineral density for the detection of osteoporosis.


Friday, June 19, 2009

GAMMA CAMERA

GAMMA CAMERA :
A piece of apparatus that detects radioactivity in the form of gamma rays emitted by radioactive isotopes that have been introduced into the body as tracers. The position of the source of the radioactivity can be plotted and displayed on a TV monitor or photographic film.


SINGLE HEAD GAMMA CAMERA


DUAL HEAD GAMMA CAMERA


WHOLE BODY SCAN



SYSTEM COMPONENTS:
•Collimator
•NaI(Tl) crystal
•Light Guide (optical coupling)
•PM-Tube array
•Pre-amplifier
•Position logic circuits (differential&addition etc.)
•Amplifier (gain control etc)
•Pulse height analyzer
•Display (Cathode Ray Tube etc).




WORKING OF GAMMA CAMERA

Usage:

Lung Scans
Thyroid Uptakes and Scans
Brain Scans
Bone Scans
Cardiac Scans

NUCLEAR IMAGING

What is Nuclear Imaging ?
• The process involves injecting into the body a small amount of chemical substance tagged with a short lived radioactive tracer. Depending on the chemical substance used, the radiopharmaceutical concentrates in the part of the body being investigated and gives off gamma rays. A gamma camera then detects the source of the radiation to build a picture. These are called scans.
Radioisotope Treatments or Therapy :
• Radiotherapy using external beam treatment is used commonly for treatment of cancers (see Oncology). However the use of unsealed, liquid sources in the treatment of disease is important in a few, specialized situations. For example Iodine-131 is taken orally to treat overactive thyroid and cancer of the thyroid.
Nuclear Imaging Scans:
Brain Scans These investigate blood circulation and diseases of the brain such as infection, stroke or tumor. Technetium is injected into the blood so the image is that of blood patterns.
Thyroid Uptakes and Scans These are used to diagnose disorders of the thyroid gland. Iodine 131 is given orally , usually as sodium iodide solution. It is absorbed into the blood through the digestive system and collected in the thyroid.
Lung Scans These are used to detect blood clots in the lungs. Albumen, which is part of human plasma, can be coagulated, suspended in saline and tagged with technetium.
Cardiac Scans These are used to study blood flow to the heart and can indicate conditions that could lead to a heart attack. Imaging of the heart can be synchronised with the patient's ECG allowing assessment of wall motion and cardiac function.
Bone Scans These are used to detect areas of bone growth, fractures, tumors, infection of the bone etc. A complex phosphate molecule is labeled with technetium. If cancer has produced secondary deposits in the bone, these show up as increased uptake or hot spots.
Radioisotopes Used in Nuclear Medicine:
• For imaging Technetium is used extensively, as it has a short physical half life of 6 hours. However, as the body is continually eliminating products the biological half life may be shorter. Thus the amount of radioactive exposure is limited.
• Technetium is a gamma emitter. This is important as the rays need to penetrate the body so the camera can detect them.
Because it has such a short half life, it cannot be stored for very long because it will have decayed. It is generated by a molybdenum source (parent host) which has a much greater half life and the Tc extracted on the day it is required. The molybdenum is obtained from a nuclear reactor and imported. For treatment of therapy, beta emitters are often used because they are absorbed locally.

NUCLEAR MEDICINE

Nuclear Medicine:
Nuclear medicine began approximately 50 years ago and has evolved into a major medical specialty for both diagnosis and therapy of serious disease. More than 3,900 hospital-based nuclear medicine departments in the United States perform over 10 million nuclear medicine imaging and therapeutic procedures each year. Despite its integral role in patient care, nuclear medicine is still often confused with other imaging procedures, including general radiology, CT, and MRI.

Nuclear medicine studies document organ and function and structure, in contrast to conventional radiology, which creates images based upon anatomy. Many of the nuclear medicine studies can measure the degree of function present in an organ, often times eliminating the need for surgery. Moreover, nuclear medicine procedures often provide important information that allows the physician to detect and treat a disease early in its course when there may be more success. It is nuclear medicine that can best be used to study the function of a damaged heart or restriction of blood flow to parts of the brain. The liver, kidneys, thyroid gland, and many other organs are similarly imaged.