Unit_20_Medical_Physics_Techniques[1]

Aim and purpose The aim of this unit is to enable learners to develop, through a practical vocational skills approach, an understanding of the important fundamental physics concepts behind medical physics techniques such as x-rays, ultrasounds, diagnostic imaging and magnetic resonance imaging (MRI) and radiotherapy. Learners will also understand the importance of radiation safety. Unit introduction Diagnostic medicine has come a long way since the time when the best diagnosis occurred during the postmortem examination. Surgery today is faster, less invasive and more effective than ever – thanks in part to improvements in medical imaging technology. Imaging gives the doctor a clearer understanding of the patient’s condition so treatment can be planned more effectively and therapy delivered more precisely. Nuclear medicine is providing hope for the cure of the most serious diseases, especially cancer. Radioactive materials are used in this rapidly developing branch of medicine. At the cutting edge of developments in nuclear medicine is the precise targeting needed to get the radiation to the exact site of the cancer. Future prospects are even more exciting. Medical imaging is extending human vision into the very nature of disease; at the cellular level it will permit diagnosis before symptoms even appear. Surgery in the future will be bloodless, painless and non-invasive. It will be powered by medical imaging systems that focus on the disease and use energy to destroy the target but preserve healthy tissue. Researchers are testing the use of highintensity ultrasound to destroy tumours identified and targeted while the patient lies in an MRI scanner. This unit introduces learners to some of the established practices in medical physics imaging. It aims to deliver the underpinning knowledge of several of the fundamental techniques and provide a basic introduction to the more complicated theory of magnetic resonance imaging. Learning outcomes On completion of this unit a learner should: 1 Know atomic structure and the physical principles of ionising radiation and ultrasound 2 Understand how radiopharmaceuticals are used in diagnostic imaging 3 Know the basic principles of magnetic resonance imaging 4 Understand the importance of radiation safety to the treatment of malignant disease with radiotherapy. This study source was downloaded by from CourseH on :26:10 GMT -05:00 UNIT 20: MEDICAL PHYSICS TECHNIQUES Edexcel BTEC Level 3 Nationals specification in Applied Science – Issue 1 – January 2010 © Edexcel Limited 2009 2 Unit content 1 Know atomic structure and the physical principles of ionising radiation and ultrasound Radioactivity: industrial applications; atomic structure; characteristics of alpha, beta (β+ and β– ) and gamma radiations; random nature of radioactive decay, half-life t1 2 , decay constant λ and activity A A e t = − 0 λ , A = λN X-rays: industrial applications eg production of x-rays from a target; x-ray spectrum and effect of tube voltage, tube current, target material and filtration; interaction of x-rays with matter; attenuation, inverse square law, absorption and scattering, intensity I I e x = − 0 µ and half value thickness x1 2 2 = ln µ Ultrasound: industrial applications; production of ultrasound and basic principles of eg pulse echo technique, reflection α = ( ) − ( ) +         z z z z 2 1 2 2 1 2 and refraction, interaction with tissue, scattering and absorption; intensity measurement in decibels; specific acoustic impedance; sonar principle and ultrasonic scanning eg A-scan, B-scan and M-scan; Doppler effect; measurement of blood flow using Doppler ultrasound 2 Understand how radiopharmaceuticals are used in diagnostic imaging Radionuclides: industrial applications eg radionuclides; radionuclide generators and preparation of radiopharmaceuticals; the need for quality control, sterility and apyrogenicity; advantages and disadvantages of radionuclide imaging The gamma camera: operating principles of main components; function as a detector 3 Know the basic principles of magnetic resonance imaging Nuclear magnetic resonance: industrial applications; proton spin, energy levels and precession; resonance; overview of process, eg block diagram; factors influencing signal intensity; relaxation, contrast and resolution Instrumentation and equipment: magnets, gradient field coils, radio frequency coils MRI applications and safety: abnormal body water, joints, abdomen, head and spine; instruments and equipment, implants, patient tolerance and quenching 4 Understand the importance of radiation safety to the treatment of malignant disease with radiotherapy Effect of x-rays: effect on cells and tissue in relation to malignant disease; absorbed and effective doses Radiotherapy: types eg megavoltage and superficial therapy; beam characteristics, multiple and rotational beams, wedges and compensators; linear accelerator; industrial applications Radiation safety: major effects of ionising radiation on the body; outline of the need for legislative requirements and dose limits; use of film badges and thermoluminescent dosimeters; procedures for reducing radiation hazards This study source was downloaded by from CourseH on :26:10 GMT -05:00 3 Edexcel BTEC Level 3 Nationals specification in Applied Science – Issue 1 – January 2010 © Edexcel Limited 2009 Assessment and grading criteria In order to pass this unit, the evidence that the learner presents for assessment needs to demonstrate that they can meet all the learning outcomes for the unit. The assessment criteria for a pass grade describe the level of achievement required to pass this unit. Assessment and grading criteria To achieve a pass grade the evidence must show that the learner is able to: To achieve a merit grade the evidence must show that, in addition to the pass criteria, the learner is able to: To achieve a distinction grade the evidence must show that, in addition to the pass and merit criteria, the learner is able to: P1 describe radioactivity, including atomic structure [TW1,5] M1 explain the random nature of decay and how it relates to half-life D1 analyse the effect of the operation and design of the tube/head on a typical x-ray spectrum P2 describe the production of x-rays and ultrasound P3 describe the production and detection of radiopharmaceuticals [IE1,2; SM3] M2 compare the desirable biological properties and radiological properties of radionuclides used for imaging D2 evaluate the choice of radiopharmaceuticals for a range of clinical imaging requirements P4 explain the role of pharmaceuticals within the operating principles of the gamma camera [TW1,5] P5 outline the process of magnetic resonance imaging including the instrumentation and equipment used [IE1,2] M3 explain the factors influencing signal intensity in MRI D3 evaluate the appearance of bone and soft tissue in an MRI scan and a conventional x-ray P6 explain the principles and effects of radiation therapy including the equipment used [IE1,2; SM3]. M4 explain how excessive exposure to radiation can cause harm. D4 evaluate a range of therapy techniques, types of radiation available and the equipment used. PLTS: This summary references where applicable, in the square brackets, the elements of the personal, learning and thinking skills applicable in the pass criteria. It identifies opportunities for learners to demonstrate effective application of the referenced elements of the skills. Key IE – independent enquirers CT – creative thinkers RL – reflective learners TW – team workers SM – self-managers EP – effective participators This study source was downloaded by from CourseH on :26:10 GMT -05:00 Edexcel BTEC Level 3 Nationals specification in Applied Science – Issue 1 – January 2010 © Edexcel Limited 2009 4 Essential guidance for tutors Delivery Each learning outcome has a significant amount of underpinning knowledge and is best delivered by starting with the industrial applications. The practical opportunities are limited in this unit but work should be developed, where possible, to support learning outcome 1. It is unlikely that centres will have the facilities for learners to carry out practical work for the remaining learning outcomes. Therefore, tutors should use video recordings, computer simulations, visits to hospital medical physics departments and guest speakers. Lectures, group work and directed reading would also be appropriate in this unit. If learners will be working in hospital departments it may be possible for additional practical investigations to be undertaken in the workplace. There is an opportunity in this context to make the methods of assessment more inventive – the more this happens, the greater the potential benefit for learners to get more insight into the wide and expanding range of possible nuclear medicine-based careers available. If the tutor can convey the necessary enthusiasm for what is a remarkable area of science and actively work to engage learners through different methods of delivery, it should be a rewarding experience for everybody. It is suggested that each area of medical imaging continues to be covered throughout the criteria. For example, nuclear medicine begins with basic principles in learning outcome 1, techniques examined in learning outcomes 2 and 3 and safety addressed in learning outcome 4. This is a complex subject and care should be taken not to exceed the level of the course, especially with the section on MRI which should only be dealt with qualitatively. Learners should be made aware that our world is radioactive and has been since it was formed. Every day, we ingest and inhale radionuclides in our air, food and water, but the safety procedures and sterility required when dealing with radionuclides for medical uses should be stressed.