Radiation Physics Quiz Question & Answers (Question Bank) Free Online Test For Medical Students like PG, PHD, Specialist exam entrance.
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Radiation Physics Quiz Question & Answers (Total 50 MCQs)
Radiation Physics Online Mock Test (high Level)
CT heads- 2mSv
CT throax- 18 mSv
CT abdomen- 10 mSv
Chest xray PA view - 0.02mSv
Orthovoltage or deep therapy is the treatment with x rays ranging from 150 to 500 kV.
X ray beams of energy 1 MV or greater can be classified as megavoltage beam.
A contact therapy machine usually operates at a potential of 450-660 kV.
Superficial therapy applies to the treatment with X rays from 50-150 kV.
Film gamma is the average slope of the characteristic curve
Speed can be defined as the exposure required producing a net density of 1
Sensitometer is an instrument that can be used to derive the characteristic curve
It is the curve between log exposure and optical density.
Increase Xray output per mAs
Reduces patient dose
Reduces film blackening
Aging increases base +fog level
Base + fog level is independent of temperature
Film is insensitive to chemicals
Base + fog is independent of development of film
Single leaf collimator
Output phosphor is smaller than the input phosphor
Output phosphor is made of zinc alumnium sulphate
Output phosphor converts incident light into electrons.
Thickness of outer phosphor is about 10 mm
It has high melting point
High vapour pressure
High thermal conductivity.
High atomic number.
X rays are electromagnetic radiations
X- rays have a velocity of sound
Produced by stopping high energy electrons in a tungsten target
Intensity falls off in accordance with the inverse square law.
Neutrons have 0 charges and 1 relative mass
Protons have +1charge and relative mass 1
Alpha particles are having +4 charge and relative mass of 2
Electrons have negative charge of -1
Density of the material
Photon energy (kV)
Atomic number (Z)
Physical state of matter
The radiation dose is designed to conform to the 3D shape of tumors
It has potential to reduce treatment toxicity.
It is used for the treatment of prostate cancer but never for thyroid and breast malignancies
It is beneficial in treatment of some pediatric malignancies.
They reduce the mean energy of the beam
Removes low energy photons
Glass of the tube also acts like a filter
K edge can be sometimes used in mammography
Depends upon the 90% of the tumor size.
Less than target radiation volume.
More than target radiation volume.
Equal to the target radiation volume.
Produced in a nuclear reactor
It has a very long biological half-life.
Involved in isomeric transition
Most commonly used isotope medically.
Energy of photon is reduced gradually
90 degree scatter photon has a higher energy than a 60 degree scatter photon
Direction of scattered photons depends on energy of incident photon
The energy of scattered photon depends on the energy of incident photon.
Random pattern of photons on X ray film.
Less with high kV energies
Less with use of filters
Larger the number of photons absorbed, more is the noise.
Use of screen
Thickness of the tissue.
Grids are stationary as well as moving.
The larger the grid ratio, the more efficient the grid is in absorbing scatter radiations..
Contrast improvement factor of the grids is defined as contrast with a grid divided by contrast without a grid.
Grids are frequently used in children and in extermities as they reduce the dose.
Resolution of a CR system is approximately 3.5-5.5 line pairs/mm
Fourier analysis is technique of representing an image by a series of cos waves.
A digital image is stored as a matrix of pixels having values in binary notations
CR is a method of image capture based on photostimulable phosphor plates.
Used for whole body dosage
Cannot be reduced
Permanent records achieved
Use lithium fluoride as active ingredient
Photon disappears completely
Produces ionized atom
Interaction between photon and bound electron
Decrease with increase in density
Linear attenuation coefficient.
Contrast medium given.
Film processing conditions.
Has multiple filters for different radiations
Processed six monthly
Can identify the type of radiation exposure
Effect by change in temperature and humidity.
Reduced by increasing film focus distance (FFD)
Reduced by increasing object film distance
Is propotional to relative length of image to object
Distortion increases by magnification increase
Isotopes have same atomic number (Z)
Isotopes have same mass number (A)
Isotopes have same physical property
Isotopes have same density
Absorbed dose is measured is Sieverts
Equivalent dose is measured in Sieverts
KERMA is measured in Gray
1Gy = 1J/kg
The characteristic curve of the film is a plot of optical density against the log of dose to the film
Film latitude is the range of film exposures that produce optical densities in the useful range of the film.
Intensifying screens convert the light rays into x rays.
Contrast is directly related to gamma.
Decreases with flattening of input screen
Can be minimized by strict quality control
Periphery is darker and magnified
Blur out shadows cast by lead strips
Increases patient dose
Decreses grid cutoff
Subject to failure
Bone marrow depression