Diagnostic Techniques


Diagnostic Imaging

This refers to a range of techniques that produce images. 

These images enables medical professionals to investigate the appearance of internal organs, which otherwise could not be visually examined without opening the body surgically.

Staff who operate imaging equipment are called radiographers.

One advantage of all imaging techniques is that they are non-invasive; they do not involve opening the body surgically.

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Diagnostic Imaging - Ultrasound Scanning

  • Ultrasound scaning uses a transducer to produce a beam of high-frequency sound waves
  • These waves are several million Hertz, therefore too higher frequency for people to hear
  • These exceptionally high waves penetrate some soft tissues and are partially reflected from surfaces
  • The practitioner places the transducer on the skin over the part of the body that is to be scanned
  • An oily gel is used to make sure there is good contact between the transducer and the skin
  • Alongside the transducer there is a receiver that can detect the sound reflected frm surfaces inside the body 
  • Computer software is used to process the data and produce an image of the tissues
  • Mostly used to scan a fetus in the womb
  • The image is poor quality, but enables a practitioner to see the movement of the fetus
  • It can provide useful information including whether there is more than one fetus, the stage of development, and the proesence of neural tube defects such as spina bifida
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Diagnostic Imaging - Ultrasound Scanning

  • Ultrasound scanning is also used to help a practitioner position a needle accurately when test procedures such as amniocentesis or chorionic villus sampling are carried out
  • It is also used to observe the condition of several other structures and organs such as the liver and kidneys (this can identify the presence of kidney stones or gallstones)
  • An advantage of ultrasound scanning is that it carried a low risk of harm, so it can be used in some situations where X-rays cannot, such as observation of a fetus
  • It also produces a real-time moving imagine
  • It is inexpensive, compared with MRI scans
  • However, the quality of image is poor and there is not a great deal of detail
  • Also, an ultrasound scan cannot penetrate bone and therefore cannot be used to scan the brain
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Diagnostic Imaging - X-Rays

  • Type of electromagnetic radiation
  • Extremely short wave length, enabling them to penetrate some materials that light waves and radio waves cannot pass through
  • X-rays can pass through soft tissue however they cannot pass through thick pieces of bone
  • This property makes X-rays ideal for imaging certain structures inside a person's body
  • An X-ray machine produces an invisible beam of X-rays, which are directed at a specific part of the patient's body
  • Underneath the particular part of the body, a sheet of photographic paper is placed in an envelope (to protect it from light)
  • The X-rays pass through the body and the envelope and cause a change in the photographic paper
  • X-rays can pass through soft tissue therefore they are dark on the photographic paper, creating an almost shadow of the bone 
  • The paper is then developed like an ordinary photographic negative, producing an X-ray
  • This is because denser tissues such as bones and heart muscle absorb more of the radiation that soft tissues do 
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Diagnostic Imaging - X-Rays

  • One advantage of X-rays is that it is quick and easy to use
  • Negatives can be developed while the patient waits
  • X-rays machines can be made small enough to fit in small dental practises and local surgeries and larger ones can be made for hospital use to obtain larger images of larger body parts
  • Another advantage is that it is very cheap in comparison to other methods of imaging
  • However, X-ray radiation can cause damage to bodily cells which could lead to cancer in some cases
  • As a precaution, lead aprons are worn over reproductive organs to shield them from the effects of the radiation which could lead to infertility
  • Lead is particulary opaque to X-rays
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Diagnostic Imaging - Contrast X-rays

  • X-rays can also be used to examine softer tissue structures
  • Abnormalities of the heart and lungs often show up as shadows on an X-rays image
  • Howwever, hollow or fluid-filled organs such as digestive organs (stomach and intestines) are more difficult to image
  • The patient will swallow a contrast medium of barium sulphate (barium swallow)
  • This is a liquid containing metal salts that are opaque to X-rays
  • Some time is allowed to pass depending on which stage of the digestive process is being imaged, and then X-ray images are taken
  • When studying lower regions of the digestive system, then barium enema is used
  • This is where the barium sulphate solution is pumped into the rectum of the patient
  • Contrast mediums can also be used to examine the circulatory system
  • The medium in this case is a dye containing iodine which is injected via a catheter
  • An X-ray of the heart produced in this way is called an angiogram
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Diagnostic Imaging - Magnetic Resonance Imaging

  • MRI scanning takes place in a large, horizontal cylinder, which can accommodate a person's whole body
  • The cylinder is equipped with a powerful electromagnet which is so strong is causes charged particles in hydrogen atoms in the body tissue to become aligned in the same direction
  • A strong pulse of radio waves then vibrates these particles, knocking them out of alignment
  • The particles produce detectable radio signals as they fall back into alignment, which are then detected by a receiver
  • The strength of the emitted radio waves depends on the type of tissue
  • Tissues containing lots of hydrogen atoms produce a bright image, and little hydrogen atoms produce a dark image
  • A whole series of MRI slices can be imaged to produce a three-dimentional image of body structures and organs
  • This method is useful for imaging the brain and joints
  • Also, it shows a greater contrast between normal and abnormal tissues 
  • It does not produce harmful radiation
  • However, the magnetism can interfere with the functioning of electrical devices such as pacemakers
  • It is also very expensive
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Diagnostic Imaging - CT Scanning

  • CT = Computed tomography
  • Produces image of "slice" or section of body
  • Patient lies on table which slides into a cylinder
  • Cylinder rotates around them
  • Scanner in the cylinder emits pulses of x-rays
  • X-rays are passed at slight different angles to observe hundred of different levels of density
  • Detector receives radiation that has passed through the body
  • Different parts of the body absorbs radiation different (creating light and dark imaging)
  • Information from x-rays is processed by computer to produce an image
  • "Slices" of the body can be built up to create a 3D image
  • Used to scan head traumas, tumours and lung defects
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Diagnostic Imaging - Radionuclide Scanning

  • Way of imaging bones, organs and other parts of the body by using a small dose of radioactive chemical
  • A radionuclide (isotope) is a chemical which emits gamma rays
  • Small amount of radionuclide is injected through the vein
  • Different nuclides collect or concentrate on different organs or tissues
  • For example, iodine is quickly taken up into the tissues of the thyroid gland
  • Active cells in the target tissue or organ will take up more of the radionuclide
  • Active parts of the tissue will emit more gamma rays than less active parts
  • Gamma rays are detected by a gamma camera
  • Gamma rays emitted from inside the body are detected by the camera
  • Rays are converted into electrical signal
  • Computer builds a picture by converting the different intensities of radioactivity iemitted into different colours
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Diagnostic Imaging - Radionuclide Scanning

  • Areas of the target organ or tissue which emit lots of gamma rays may be shown as red spots on the picture on the computer monitor
  • Areas which emit low levels of gamma rays may be shown as blue
  • Radionuclide scanning is used for bone scans
  • Radionuclide collects in areas where there is a lot of bone activity
  • Used to detect cancer, infection or damage
  • Also used for kidney scans to assess the functioning
  • Radionuclide is taken up by kidney cells and passes into the urine
  • The scan can detect scars on the kidney and how well urine drains into the bladder
  • Used to observe the functioning organs or tissues, which often starts to deteriorate before physical structure which is seen on other scans
  • Gamma rays can be harmful to babies in the womb or women breastfeedings
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Diagnostic Imaging - PET Scanning

  • PET = Positron emission tomography
  • Produces a 3D colour image of the body using radionuclides
  • Shows where cells are particularly active
  • Used commonly in the diagnosis and assessment of cancer, to diagnose alzheimer's disease, epilepsy and heart disease
  • A radioactive medicine is produced in a machine called a cyclotron
  • The medicine is tagged to a natural chemical such as glucose, water or ammonia
  • This is called a radio-tracer
  • The radio-tracer is swallowed or injected
  • It travels to part of the body that use the chemical it has been tagged to
  • Works by detecting the energy released by positrons (tiny particles which are made as the radio-tracer is broken down)
  • When positrons are broken down by the body, they produce gamma rays which are detected by the scanner
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Diagnostic Imaging - PET Scanning

  • Produces a 3D image
  • Shows how different parts of the body work by observing the way it breaks down the radio-tracer
  • Different levels of positrons are shown as different colours and brightness
  • Hot spots show where large amounts of the radio-tracer have built up
  • Injected and then have to wait for it to travel to the part of the body required
  • Large cylinder shaped scanner
  • Rings of detectors that record the emission of energy from the radio-tracer
  • Little harm - radioactive chemicals are safe and leave the body quickly
  • If pregnant or breast-feeding, there may be a risk to the baby
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Diagnostic Imaging - ECG

  • ECG = Electrocardiography
  • Electrodes are attached to the patients skin by sticky pads
  • Linked by wires to the machine that records the electrical activity of the heart
  • Examined by cardiologist
  • Electrical activity is caused by nerve impulses that trigger contractions in different parts of the heart
  • Wavy line appears on the paper or moving line on a monitor
  • Deviations from normal shape can indicate damage to the heart muscle
  • Electrodes placed elsewhere on the body reveal activity of arteries and veins
  • Abnormalities are somtimes only observable when heart is under stress
  • Asked to run on tredmill or exercise bike
  • ECG's are non-invasive
  • Equipment is small and inexpensive
  • However, it can only indicate a problem, does not give a reason why
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Tissue Biopsy

  • A biopsy is a medical procedure that involves taking a small sample of tissue so that it can be examined under a microscope
  • It can be taken from almost anywhere on, or in, your body, including the skin, stomach, kidneys, liver and lungs
  • The term biopsy is often used to refer to both the act of taking the sample and the tissue sample itself
  • It is used to investigate the cause of a person's symptoms or to help diagnose a number of different health conditions. Also used to identify abnormal cells and identify a specific type of condition
  • When a condition has been diagnosed, biopsy is used to measure how sever it is
  • Used to diagnose: cancer, peptic ulcers, hepatitis and kidney disease
  • Impossible to determine whether a lump is malignant or benign by looking or feeling, a biopsy can provide this information
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Tissue Biopsy - Scraping Cells

  • Scraping cells from the surface layer of tissue, such as inside the mouth, is enough to provide a suitable sample for examination
  • Anaesthetic isnt required
  • Cervical screening test is where a small brush-like instrument is used to gently remove a sample of cells from the cervix
  • Cells are then examined under microscope for abnormalities
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Tissue Biopsy - Punch Biopsy

  • Used to investigate skin conditions such as deep spots and sores
  • A surgical instrument used to make small hole in the skin and remove sample of the top layer of tissue
  • Given local anaesthetic to numb the area
  • A scalpel may be used to remove a small amount of surface skin
  • The wound will be closed using stitches
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Tissue Biopsy - Needle Biopsy

  • A fine-needle aspiration biopsy is often used to take tissue samples from organs or lumps that are below the surface of the skin
  • If a larger sample is required, a core needle biopsy may be used instead
  • A hollow needle is inserted through your skin and into the area being examined
  • Ultrasound or x-rays will be used to guide the needle to the right place
  • When in position, the needle will **** out a sample of tissue
  • A local anaesthetic is used to numb the area
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Tissue Biopsy - Endoscopic Biopsy

  • An endoscope is a medical instrument that's used to look inside the body
  • Thin tube with light and camera on the end 
  • Small cuttintg tubes can be used for the surgeon to take a tissue sample
  • Can be inserted through your throat, anus, or through small cuts made by the surgeon
  • Depending on the area of the body being investigated and the entry point, local or general anaesthetic will be used
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Tissue Biopsy - Perioperative Biopsy

  • Sometimes carried out during an operation for another, unrelated reaons
  • Tissue sample taken durng surgery and checked immediately 
  • So surgeon can decide how to progress with treatment 
  • Lump found during surgery may be removed completely is patient is still under anaesthetic and previously given consent
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Tissue Biopsy - Testing a Sample

  • After a tissue sample has been taken, it will be sent to a laboratory
  • It is examined under a microscope and cells can be tested
  • This enables scientists to determine whether the tissue samples are abnormal
  • Chemical or genetic tests can also be carried out
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Body Fluid Sampling - Urine Tests

  • Can be collected at home by the patient, on a visit to the GP's surgery, or in hospital 
  • The sample can be tested chemically to detect levels of glucose or proteins
  • It can be detected for infectious disease agents, such as bacteria
  • Can be used to diagnose kidney diseases, UTIs and diabetes
  • Can reveal the prescence of drugs and abnormal levels of ions
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Body Fluid Sampling - Mucus Test

  • Mucus can be collected from mucous membranes
  • In the mouth, throat, or vagina
  • Cells from this mucus sample can be cultured (grown) and examined under the microscope for the presence of bacteria or viruses
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Body Fluid Sampling - Blood Test

  • A blood test is when a smaple of blood is taken for testing in a laboratory
  • Used to assess general state of health, confirm the presence of bacterial or viral infection, see the functioning of organs, screen for certain genetic conditions
  • Carried out at GP surgery or hospital under supervision of a nurse
  • A tourniquet is put around the arm to slow down the blood flow, causing the vein to swell
  • The nurse will clean the area with an antiseptic wipe
  • Needle attached to a syringe is pushed into the vein
  • Syringe is used to draw out a sample of the blood
  • The needle will be removed
  • Pressure is applied to the place where the needle was using a cotton-wool pad to stop the bleeding and prevent bruising
  • A plaster will keep the wound clean and prevent infection
  • The sample will be sent to the lab and tested chemically or microscopically
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