QuestionQuestionConceptConceptDocumentDocument

24. Medical physics

Start with Concept to understand a topic, then use Question Bank to check what you know.

3 topics · 16 learning objectives

Your progress

Sign in to see your mastery and mistakes.

  1. 24.1 Production and use of ultrasound

    1. 24.1.1A piezo-electric crystal changes shape when a p.d. is applied across it and

      • understand that a piezo-electric crystal changes shape when a p.d. is applied across it and that the crystal generates an e.m.f. when its shape changes

    2. 24.1.2Ultrasound waves are generated and detected by a piezoelectric transducer

      • understand how ultrasound waves are generated and detected by a piezoelectric transducer

    3. 24.1.3The reflection of pulses of ultrasound at boundaries between tissues can be

      • understand how the reflection of pulses of ultrasound at boundaries between tissues can be used to obtain diagnostic information about internal structures

    4. 24.1.4The specific acoustic impedance of a medium as Z = ρc

      • define the specific acoustic impedance of a medium as Z = ρc, where c is the speed of sound in the medium

    5. 24.1.5IR / I0 = (Z1 – Z2)2 / (Z1 + Z2)2 for the intensity reflection coefficient

      • use IR / I0 = (Z1 – Z2)2 / (Z1 + Z2)2 for the intensity reflection coefficient of a boundary between two media

    6. 24.1.6I = I0e–µx for the attenuation of ultrasound in matter

      • recall and use I = I0e–µx for the attenuation of ultrasound in matter

  2. 24.2 Production and use of X-rays

    1. 24.2.1That X-rays are produced by electron bombardment of a metal target and

      • explain that X-rays are produced by electron bombardment of a metal target and calculate the minimum wavelength of X-rays produced from the accelerating p.d.

    2. 24.2.2The use of X-rays in imaging internal body structures

      • understand the use of X-rays in imaging internal body structures, including an understanding of the term contrast in X-ray imaging

    3. 24.2.3I = I0e–µx for the attenuation of X-rays in matter

      • recall and use I = I0e–µx for the attenuation of X-rays in matter

    4. 24.2.4Computed tomography (CT) scanning produces a 3D image of an internal

      • understand that computed tomography (CT) scanning produces a 3D image of an internal structure by first combining multiple X-ray images taken in the same section from different angles to obtain a 2D image of the section, then repeating this process along an axis and combining 2D images of multiple sections

  3. 24.3 PET scanning

    1. 24.3.1A tracer is a substance containing radioactive nuclei that can be introduced

      • understand that a tracer is a substance containing radioactive nuclei that can be introduced into the body and is then absorbed by the tissue being studied

    2. 24.3.2That a tracer that decays by β+ decay is used in positron emission

      • recall that a tracer that decays by β+ decay is used in positron emission tomography (PET scanning)

    3. 24.3.3Annihilation occurs when a particle interacts with its antiparticle and that

      • understand that annihilation occurs when a particle interacts with its antiparticle and that mass–energy and momentum are conserved in the process

    4. 24.3.4That, in PET scanning, positrons emitted by the decay of the tracer

      • explain that, in PET scanning, positrons emitted by the decay of the tracer annihilate when they interact with electrons in the tissue, producing a pair of gamma-ray photons travelling in opposite directions

    5. 24.3.5The energy of the gamma-ray photons emitted during the annihilation of an

      • calculate the energy of the gamma-ray photons emitted during the annihilation of an electron-positron pair

    6. 24.3.6The gamma-ray photons from an annihilation event travel outside the body and

      • understand that the gamma-ray photons from an annihilation event travel outside the body and can be detected, and an image of the tracer concentration in the tissue can be created by processing the arrival times of the gamma-ray photons