medphysics final essays

electromagnetic radiation

• em spectrum, waves catgorised by

• RIVUXG

• light has wave particle duality

• light fastest in vaccum

• e= h (c x w)

• n = c/v

reflection refraction

• reflection

• refraction

• total internal reflection

• absorption

• scattering

• rreflection diagram

• refraction diagram

  • a = E x c

• range

• nonionising

• sources

• uv bands and ranges

  • a 315-400

  • b 280-315

  • c 200-280

• +ve and -ve of uv bands

• ct mutation

• protection

• diagram is spectrum

infrared

• non ionising

• range

• sources

• propereties; thermal effect, law diffraction

• uses; IR imaging and therapy

• spectrum

• bands

  • a 0.76 - 2.5um

  • b 2.5 - 50um

  • c 50 - 1000 um

• bio action; increase tissue temp, vasodilation

• thermodivision; detects heat emitted from body e.g. inflammation

luminescence

• what; electric transition from excited > ground state

• photoilluminescene

  • flurescence short illumination lasts less than 10-9

  • phosphorescence emittion after excitation stops, longer than 10-6

• stokes law Wlum > W ex

• vavilovs law; no of excited photons if proportional to no of luminescent photons

• diagnostic methods;

  • flurescence, cancer detection,

    • chemilluminescence, blood tests

parameters of laser radiation

• wavelength

• intensity

• pulse duration

• spot size

• monochromaticity

• coherence

• directionality

  • medical applocations; oncology, dermatology, surgery, opthamology

microscope

• instrument to observe microobjects

• opticsal microscope uses visible light and lenses to magnify small images = 2d, high M low R

• optic scheme,, eyepiece, objective

• components of M

• magnification'

• mag eq

• resolution

• observation modes

  • bright field microscopy, sample illuminated from below, observed from above

  • dark field microscopy, live microO, not visible or stained

  • phase contrast microcopy converts phase differences into brightness differences

lasers

• def; coherent light with properties

  • monochromatic

  • directional

  • coherent

  • polarised

• types of lasers

  • visible light

  • gas lasers

  • infrared

• absorption; atom E0, atom energy by incident photon so E1

• spontaneous emission; excited atom on e1 spontaneously emitts photon so moves to e0,, photon emitted in rando direction

• stimulated emission; excited atom, stimulated to fall to e0 as photon interacts w atom,, 2 identical photons released

• population inversion; more atoms in excited than ground by pumping

• pumping; energy to lasers active medium so theyre raised to higher level e.g. laser pumping

• metastable state; when atom is excited state, stays for time

• 3 level laser scheme; pumping moves atom e0>e2,, unstable state now so falls to metastable state = population inversion at e1.. photon allows e1>e0

• 4 level laser scheme; atom e1>e3,, unstable so fall to metastable state where pop inv,, atoms stimulated and fall to e1 = laser radiation

• component of laser

  • active medium

  • pumping system

  • optical resonator

human eye

• opticsl system

  • cornea

  • retina

  • lens

  • anterior chamber

  • optical nerve

• refractive power,, ability to bend light + focus on retina

  • n = c/v

• refraction

• reduced schematic eye; cornea and lens act as single convex lens

• optical lens types; cylindrical, spherical

• spectral sensitivity; eye responds to light 400-700

• emmetropia; normal

• myopia; short sighted,, image projected before retina,, high OP,, corrected by concave lens so rays spread and converge later

• hypermetropia; far sighted,, image proj after ret,, low OP,, corrected my convex lens which bends light so rays meet earlier

• astigmatism; light rays focussed on multiple points in retina,, cylindrical lens corrects this by meeting in one

• strabism,, muscles in the eye lack coordination

ionising radiatiations

• high energy radiation to remove e- from materials

• non ionising 10³ > 10^-8

• ionising 10^-8 > 10^-13 ,, x ray and gamma

• direct ionsising radiation,, charged particles, e- and photons

• indirect ionsiing radiation,, secondary charged particles,, gamma and x ray photons

• how indirect radiation interacts with matter

  • incoherenet scattering; partial energy transfer

  • photoelectric absorbption; complete energy transfer

    • couple production; e- > e+

x-rays

• type of ionising radiation called roentegen radiation

• EM radiation

• 10nm - 2pm

• produced by roentegen tube as e- hit the tungsten target so energy is converted to xrays

• characteristic radiation; e- jump between shells to then produce xrays

  • braking radiation; e- slow down, energy released to produce xrays

medical application of x rays

• x ray image formation; dense structures hv high absorption

• x ray imaging; radiography, radioscopy etc

• computer tomography; gives cross sectional images of body as machine rotates and takes images at diff sngles and are combined

  • hous=nsfield scale; scale in CT scans that state how much xray absorbed at tissues

radioactivity

• atoms emitts energetic particles from nucleus

• atom strucutre

• radioactive decay; random emittion of radiation from nucleus to make it more stable (a, b, gamma rays emitted)

  • alpha decay, a particle emitted

  • beta minus decay, radionuclide has +1 neutron

  • beta plus decay nucleus emitts positron

  • gamma decay, nucleus excited > low energy state

• decay laws;

  • half life; time for half nucleides to decay > Thalf = 0.693/w

  • nuclear decay

• radiopharmaceuticals; drugs w radioactivity, used for diagnostic and therapeutic purposes

nuclear medicine imaging

• tomograph; 2d image of thin tissue layer of organ

• somputed tomography, explain from previous point

  • SPECT, gamma cameras used to form images

  • PET, pateint injected w radioactive tracer to detect emittion of radioactivity

• gamma cameras; detect emittion of gamma rays from radiopharmaceuticals in the body

dosimetry of ionising radiation

• measurment and calculation of radiation dose in body and tissue

• exposure; amnt of radiation produced in air by x or g

• absorbed dose; radiation absorbed per unit mass of tissue/ Gy

• equivelent dose; how harmful radiation is/ unit, Sv

• effective dose; overall biological risk radiation has on body/ unit, Sv

• radiation weighting factorbiological effectivness of different radiations

  • tissue weighting factor; hpw sensitive tissue/organ to radiation

radiotherapy

• medical use of high energy radiation to treat cancer

• LINAC; xray beam directed at tumour to treat it

• CYBERKNIFE robotic RT tracking tumour movement

• BRACHYTHERAPY; radiation source v close to tumour

• direct and indirect ionising radiation

• linear accelerators; accelerate charged partices

mechanical waves

• waves which vobrate particles to transfer energy

• sound waves; longitudinal mechanical waves, produce hearing perception

• physical characteristics of sound

• physical characteristucs of sound

  • pressure'

  • wavelength

  • frequency

  • intensity

  • prop speed

  • acoustic impendance'

  • spectrum

paychophysical properties of sound

• how human ear percieves sound

• intensity, power per area

• pitch, frequencies of sound

• loudness

• timbre, quality

sound diagnostics and therapy methods

• auscullation, hearing internal body sounds to assess health

• BP, sphygmomameter and steth hearing kortokoff sounds

• audiogram

• phonocardiography, graph of heart sounds

ultrasound

• non invasive diagnostic technique, high f sound waves to measure movement of blood/fluids

• properites; mechanical waves, high F low W

• 20Hz - 1MHZ

• PEIZOELECTRIC EFFECT, give us waves for medical use

  • heart imaging and blood flow

ultrasonography

• medical imaging technique to visualise muscles, tendons, joints

• US pulse sent into tissue, sound waves hit boundary between tissues, reflected waves used to see distance between probe and tissue

  • doppler effect; frequency change as source and recievr of sound move close or further away

ultrasound- sonophoresis

US waves used to enhance penetration of drugs inbody, via gel or cream

gradients

• variation in physical quantity

• diffusion of molecules,, conc gradient

• internal friction, resistance o f flow in fluid bc friction in layers

• heat conduction, heat transfer thru material by temp gradient

• medical method; haemodialysis, tubing, dialyser, solution, opposite directions, urine and creatine removed

st

structure of liquids

• liquids lossly packed

• intermolecular forces; cohesion adhesion VDW, h bond

• molecular pressue; ITMF = attraction = pressure

• surface tension, cohesive forces between molecukes give elastic stretched memb

• laplace pressure;

  • emobilisim, obstruction of blood vesslel

movement of fluids

• ideal fluids hv constant density and 0 velocity

• laminar; smooth no mixing, healthy person

• turbulent, irregular motion, strong mixing, in aorta

• steady flow, constant

• poiseuilles law; rs of fluid flow rate in cylindrical pipe

  • reynolds no

blood flow

• laminar

• reynolds no is 2000

• pulse pressure= s-d

• systole, contraction

• diastole relax

• pulse wave; elastic deformation as artery walls stretch when blood moves in

mechanics of breathing

• change in pressure and volume in chest allows air in and out of lungs

• inspiration, diaphragm contacts

• syrfactant, lining in alveolis prevents collapse and reduce surface tension

  • laplace law; p=2T/r

electric current

• movement of charge or ions

• current = charge/time

• electric conductivity; electric field applied, how easily charge moves… high conductivity = easy charge flow

• conductors, high conductivity bc free e-, silver

• semiconductors, intermediate conductivity, temp dependant, sillicon

• dielectric, no conductivity bc e- tightly bound e.g, glass

dir

direct, pulsing, ac

• DC, constant flow of e- in one direction

• AC changes direction and magnitude

• pulsing current, current flow in discrete bursts

• circuit components; switch, resistors, voltage, conductors

• impendance resistance in ac

• ohms law; v= I x r

ONE AND TWO WAY CURRENT RECTIFICATION

ac > dc

• one way; diode used allowing half of ac waveform to pass forming pulsating dc

• two way; 2 diodes used allowing both ac waveform halves to pass

electrodiagnostics