3.10.2 Diagnostic Techniques

Dianostic Imaging

Refers to a range of techniques that produces images (usually 2D still images but in some cases moving or 3D images).

The main purpose is to investigate the appearance of internal organs/structures  without the need to open the body surgically.

Non invasive/painless. 

Imaging equipment is operated by radiographers.

Types of Diagnostic Imaging

• X rays
• Contrast x rays 
• CT scan
• PET scan
• Radionuclide scanning
• MRI 
• Ultrasound scanning

X-Ray

• Type of electromagnetic radiation - familiar to us in the form of light and radio waves.
• Extremely short wavelength.
• Allows them to penetrate soft tissue of the body - cannot go through bone/metal.
• Person lays the part to be x rayed on a photographic plate/paper.
• X ray machine is aligned above the area to be x rayed.
• Invisible beam is sent from the x ray machine directed at specific part of body.
• Penetrates the soft tissue.
• Different parts of the body blakcen and areas like bone are seen as a lighter shadow because the denser bones absorb more of the radiation than soft tissues.
• Image is transerred to a computer for examination - structures can be seen.

Contrast X-Ray

• Used on hollow or fluid filled organs such as the digestive tract (oesophagus, stomach and intestines) as do not show up on the x ray without contrast medium.
• Contrast medium - harmless solution of barium sulphate in water is used.
• Barium sulphate is a metal salt which x rays cannot pass through/opaque to x rays.
• Patient either swallows the liquid known as barium meal or it is pumped into the patient's rectum known as a barium enema.
• Time is then allowed to allow the liquid to reach its destination i.e. the intestines.
• Normal x ray is taken and the contrast will show up abnormalities in the body.
• The metal salts show up like bone would in a normal way so light shadows.
• Water-soluble iodine dyes can be carried around the bodyin the bloodstream, this can be used to check that the blood is flowing normally in the blood vessles.

CT Scan - Computerised Tomography Scanning

• Uses x rays to produce an image of a slice or cross section of the body.
• Patient lies on a table which moves into a cylinder containing the scanner.
• Scanner rotates around the patient emitting x rays.
• The radiation passes through some tissues, is reflected off other tissues and is analysed by the scanner.
• Information from a set of x ray receivers is processed by computer software to build a digital image in the form of slices.
• These slices can be processed into a 2D or a 3D structure of the body.
• Used for detecting and examining conditions affecting the brain, tumours, head injuries and damage from strokes. The entire digestive tract can be examined with the use of a contrast medium. Can produce images of structures encased in bone - such as the brain.
• If there is an RTA (Road Traffic Accident) and a patient comes in and the doctors cannot work out hatis wrong with them then the patient will be sent for a CT scan.

PET Scan - Position Emission Tomography

• Used to produce detailed 3D images of the inside of the body.
• It is a flat bed with a large circular scanner at one end. 
• A radioactive substance (a radiotracer) is injected into a vein of the patient.
• The tracer gives off particles called positrons that releases gamma rays (a type of radiation)
• These are detected by the PET scanner.
• By tracking the movement of the tracer, the scaner builds up a detailed image of the body's functions as well as identifying areas of the body affected by disease.
• Often used to confirm how far a cancer has spread or if treatment has been effective.
• Hot spots

A way of imagine bones, organs, and other parts of the parts of the body using a small dose of a radioactive chemical.

• A rad (sometimes called an isotope) is a chemical which emits a type of radioactivity called gamma rays
• Injected into a vein or swallowed - time then allowed for it to travel to target areas. Depends on the organ/tissues being examinated different rads are used
• Lie on a bed and the gamma camera detects rays being emitted
• Cells which are most sctive will take up the rad and emit gamma rays
• Dectected by a gamma camera, converted into an electrical signal, sent to a computer which will build a picture
• different colours are seen - hotspots for overactivity or cold spots for little

Used for:

• A bone scan
• Kidney scan
• Heart scan
• Thyroid scan

A type of scan used to diagnose health conditions that affect the organs, tissues and bones.

• A person is placed in a large horizontal cylinder equipped with a powerful electromagnet. 
• Uses a strong magnetic field on the body and radio waves
• By focussing magnetic field on the body, it causes the hydrogen protons in body tissues to line parallel to each other
• A strong pulse of radio waves then vidrates these particles and knocks them out of alignment
• When the particles realign, they emit small radio signals which are picked up by the scanner receiver and converted by a computer into an image as a cross section
• These can be combined to make a 3D picture which is examined by a health professional
• Used for brain and spinal cord, bones and joints, breasts, heart and muscles and lungs and liverYou need to be conscious before this scan

Ultrasound Scanning

A procedure that uses high frequecny soundwaves to create an image of part of the body

• A lunricant gel is put on the skin

• A small handheld device called a trasducer is used. The gel allows the transducer to move smoothly to ensure there is continuous contact between the sensor and the skin

• The transducer is connected to a computer with a monitor

• Pulses of ultrasound are sent from a probe in the transducer theorugh the skin and into teh body

• These bounce back from the structure in the doby to be displayed as am inage on the monitor. They also show movement