G622 Monitoring the activity of the human body

1. G622 Monitoring the activity of the human body DATE: 2nd April 2014 3.3.5 Imaging Methods LO:to understand how different imaging techniques are used Starter- get out exam questions, Jun 2012 Q1 p2-4, Jan 2012 Q3 (g) p10

2. 3.3.5 Imaging Methods Technology has provided us with some very important diagnostic tools. Surgery is more successful thanks to information gained from pre-operative, non-invasive diagnosis. You will become acutely aware of the significance of computer technology in modern medicine in terms of data attainment, management and use in diagnosis. You need to: • explain the basic principles of medical X-ray radiography; • describe how CAT scans and MRI scans are used for diagnosis; • explain the basic principles of ultrasound scanning and how ultrasound scans may be useful in diagnosis; • distinguish between different types of medical scanner used in diagnosis, to include X-ray, ultrasound, CAT and MRI.

3. http://www.youtube.com/watch?v=PPsqcYVwVeI

4. X ray appearance on a conventional radiograph

5. Medical X-ray Radiography A conventional X-ray machine generates electrons when its cathode, a tungsten filament, is heated. The cathode is positioned in the head of a tube which is kept under vacuum conditions. The electrons emitted are attracted to the an anode by a large potential difference. The anode gives off X-ray photons. Most of the radiation is absorbed by the tube but a window allows some to escape.

6. Forming an X-ray Image The X-ray beam is focussed onto the body or structure under investigation. The X-rays pass through the body to impact with a detector. The detector is photographic film sandwiched between two fluorescent screens. X-rays cause light to be emitted of the screens. The light causes blackening of emulsion to occur when the film is developed. As a result an X-ray image is produced on the film.

7. Materials producing an image Denser materials, such as bone, absorbs more radiation, softer tissues absorbing less. Consequently, different tissues absorb different amounts of X-rays providing an image that can be interpreted by an experienced radiographer.

8. Effective dose from a diagnostic scan When using ionising radiation in an imaging technique the subject is irradiated. The amount of radiation absorbed by a patient during a scan is called the effective dose. This can accumulate the more X-rays that are performed.

10. CT or CAT Scanner • The Computerised Axial Tomographic Scanner (CAT or CT scanner) uses X-rays to produce images of one slice of the body at a time.

11. Uses of CAT Scanners • CAT scanners are very good for examining soft tissue. They are used: • To produce detailed images of the brain • To produce detailed images of the chest, abdominal or pelvic organs; for example the lungs, liver, kidneys, bladder and the gut.

12. CT or CAT scanner • The X-rays from the beams are detected after they have passed through the body and their strength is measured. • Beams that have passed through less dense tissue such as the lungs will be stronger, whereas beams that have passed through denser tissue such as bone will be weaker. • A computer can use this information to work out the relative density of the tissues examined. Each set of measurements made by the scanner is, in effect, a cross-section through the body.

14. MRI Scanner • Magnetic resonance imaging (MRI) uses nuclear magnetic resonance to make detailed images of slices through the body. • The images produced are in many ways similar to those of the CAT scanner, but without the radiation hazard.

15. Uses of MRI Scanner • Detecting brain and spinal cord tumours and other neurological diseases • Analysis of joints, such as the ankle, knee or shoulder • Shows presence of abnormal body water (e.g. swelling, infection, bleeding, cysts) • Fluid flow (e.g. blocked blood vessels, heart studies) • Looking at cancerous tissues

16. MRI Scanner • How an MRI scan works

18. How an ultrasound is generated Ultrasound scans use sound waves to produce images of the internal organs, vessels and tissues. The images are produced when the sound waves are directed into the body then reflected back to a scanner that measures them.

19. Piezo-crystal Ultrasound is transmitted and received using a probe. The probe includes a transducer which is the piezo-crystal which acts as the loud speaker sending ultrasound waves out as the microphone picking them up on the way back.

20. Ultrasound Scan The sound waves in an ultrasound examination are beyond human hearing. The diagnostic frequency range is 2-20MHz. The ultrasound image is viewed as a real-time picture on a monitor. The images can be recorded and presented as either stills or moving images.

21. Uses of an Ultrasound Scan A gel is used to fill the gap between the probe and the surface of the area being scanned. This is to prevent reflection at the surface.

22. Uses of an Ultrasound Scan An ultrasound scan can be used in several different ways, such as monitoring an unborn baby, diagnosing a condition or guiding a surgeon during certain procedures. Sounds waves can even be used to assess moving structures, for example blood moving through a vessel can be looked at in this way.

23. Diagnosing conditions Ultrasound scans can help diagnose problems in many parts of your body, including: liver (cirrhosis) gallbladder (gallstones) thyroid gland lymph nodes ovaries uterus (womb) testes breasts

25. Ultrasound clips • Ultrasound - Imaging in medicine (7/13) – YouTube • How to use the ultrasound probe - YouTube

26. 3.3.6 Regulations Governing Specific Procedures and Data Management Health and Safety issues in the work place make it essential that good practice guidelines are clearly stated and understood. You need to: • describe regulations for the disposal of hazardous biological waste, e.g. sharps and hypodermic needles used in obtaining blood for testing; • describe and explain procedures for the treatment of material that may be contaminated with microbiological hazards, e.g. used petri dishes, materials from antibody testing; • design a risk assessment for a blood test, stating what the hazards are, and explaining how to minimise the risk from these hazards to the person carrying out the blood test; • design a risk assessment for any other non-invasive physiological measurement, e.g. heart rate measurement, stating what the hazards are and explaining how to minimise the risk from these hazards to anyone involved; • be able to choose and evaluate relevant sources of data; • be able to obtain and use primary and secondary data.

27. 3.3.7 Ethical Issues Related to Monitoring, Diagnosis and Treatment It is important to be aware that the decision to carry out a program of diagnosis and treatment involves consideration of other issues that might affect the patient. It may not be a simple case of medical expedience. You need to: • discuss the risks, benefits and ethical issues involved in using imaging methods; • identify the risks and benefits arising from the diagnosis and/or treatment of patients with circulatory or respiratory disorders; • identify situations where it may be considered inappropriate to diagnose and/or treat patients.

28. Blood pressure values • typical 18-year-old adult 120/80 mmHg • male aged 20 years, 125/80 mmHg • female, aged 20 years, 123/80 mmHg • male, aged 40 years, 135/85 mmHg • female, aged 40 years, 133/85 mmHg

29. breathing rate, 15 – 18 breaths per min • tidal volume, 0.4 – 0.5 dm3 • vital capacity (male), 6.00 dm3 • vital capacity (female), 4.25 dm3 • Peak flow, 400 – 600 dm3

30. Health and safety Student activities: find out and make notes on the health and safety requirements for the following: 1. Regulations for disposal of hazardous biological waste e.g. sharps and hypodermic needles used in obtaining blood for testing 2. Procedures for the treatment of materials that may be contaminated with microbiological hazards e.g. used petri dishes, materials from antibody testing 3. How to carry out a risk assessment for a blood test, state hazards and explain how to minimse the risks to the person carrying out blood test

31. Disposal of syringes and hypodermic needles Sharps and hypodermic needles are disposed of in special containers to avoid contact. Specialist waste disposal companies provide a service to collect and dispose of the waste material in the sharp boxes. Similar services exist for disposal of clinical waste that might be contaminated with blood borne viruses ,such as swabs and other soiled waste. The clinical waste is finally disposed of in special incinerators. Disposal of microbiological hazards Pathology laboratories produce large volumes of clinical waste. This will include microbiological cultures, antibody testing kits, including ELISA plates, contaminated plastic tubes and even radioactive waste. All of this is potentially infected waste. High hazard waste, like microbiological cultures are autoclaved before disposing as clinical waste and then incinerated. Non disposable apparatus is sterilised by being autoclaved, washed before being reused.

32. Risk assessment for a blood test: The volume of blood my differ depending on the type of analysis required. The details of a general blood test i.e. the method used is always designed to minimise the risks involved with that hazard. Techniques may alter in some way to take the blood but the hazards, risks and precautions will be similar. The risk assessment on the next slide might be used for a blood test but it is only one example of how the assessment might appear.