Christie hospital.

   

     The lead shield is used to try and minimise the amount of background radiation, this is so that the background radiation doesn’t affect and get mixed up with the gamma radiation.

Benefits versus risks

Benefits

• One of the obvious good things about a gamma camera is that is less traumatic than an exploratory surgery.
• The functional information provided by gamma camera examinations is unique and currently impossible by using other imaging procedures. For many diseases, gamma camera studies produce the most useful information needed to make a diagnosis.

Risks

• The gamma camera procedure will result in exposure to a small dose of radiation. However, the doses of radiopharmaceutical given are the smallest possible and there are no known long-term adverse effects from such low-dose studies.
• This procedure can be dangerous to women who are pregnant or are allergic to the radiopharmaceutical, however that is very rare.

     One of the main strengths of this sort of treatment is that is cheap compared to most other treatments, its £50 a dose. However I feel that this is still quite expensive. Another strength is that it is a successful treatment.

     A limitation is that cyclotran’s are big and expensive, they sometimes even cost more than the scanner itself.

Ultrasound

     Many people think that ultrasound is only used for monitoring pregnancies, however this is not true because it is also used in lots of other areas of the body, for example the liver, kidney, thyroid or breasts. This is because an ultrasound can show the blood flowing in arteries and enable distance and area measurements to be made.

     You only need to use short pulses of sound, usually between 3-15 MHz depending on how deep into the body you need to go to, which are sent into tissues along a known track. The pulses are sent into the body using a probe and are then reflected back. As the speed of the sound is very similar it is easy to work out the depth from which the echoes come from. The machine then calculates the distance between the probe and the body organ. The machine displays the distances and intensities of the echoes on the screen, forming a two-dimensional image as shown below. In a typical ultrasound millions of pulses and echoes are sent and received each second.

Photo courtesy Karim and Nancy Nice

Ultrasound image of a growing foetus (approximately 12 weeks old) inside a mother's uterus. This is a side view of the baby, showing (right to left) the head, neck, torso and legs.

     Over the past couple of years, machines have been developed capable of three-dimensional imaging.

Photo courtesy Philips Research

3D ultrasound images 

   

     3D imaging allows you to get a better look at the organ being examined and is best used for:

• Early detection of cancerous and benign tumours
• Visualising a foetus to assess its development, especially to see if there are any abnormal development of the face or legs.
• Looking at the blood flow in different organs or a foetus.

     An example of a 3D ultrasound-imaging device is the Doppler ultrasound. This is based upon the Doppler effect, which is when the object reflecting the ultrasound waves is moving; it changes the frequencies of the echoes. If the object is closer to the probe then the frequency gets higher and if it moves away from the probe then the frequency gets lower. The change in the frequency level shows how fast an object is moving; the Doppler ultrasound measures the change in frequency level and then calculates how fast the object is moving. The Doppler ultrasound is mainly used to measure the rate of blood flow through the heart and major arteries.

     Recently there have been some concerns over the safety of ultrasound because ultrasound is energy and pregnant women are afraid about what the energy might be doing to their baby. There have been some reports of low birth weight babies being born to mothers who had frequent ultrasound examinations during pregnancy. There are two possible explanations for this:

• Development of heat – The tissues or water absorb the ultrasound energy, which increases their temperature locally.
• Formation of bubbles (cavitation) – when dissolved gases come out of the solution due to local heat caused by ultrasound

     There are also some other problems with ultrasound; there are very strong reflections from air and bones so it is difficult to see through these tissues. Higher frequencies have a shorter wavelength and therefore a better resolution but less penetration, so the frequency and penetration have to be balanced. Also it needs a skilled person to interpret what they see.

     There are some good points to ultrasound though; it is very good at showing structure and movement without having to use radiation like x-rays. Diagnostic ultrasound is a simple, safe and cheap procedure, which is used in all hospitals. Also there have not been any substantial ill effects of ultrasound recognised in either humans or animals.

     Just like other computer technology ultrasound is most likely going to become faster and have more memory for storing data. 3D ultrasounds will get be more highly developed and more popular. Currently a research group are working to develop and make a system to look directly inside a patient using augmented reality. This could be a powerful and instinctive tool that could be used to assist and to guide the physician during various types of ultrasound-guided procedures.