basic radiological imaging Flashcards
Digital images are stored as a series of — in a computer memory where they are represented by a —- whose —- or — corresponds to the — of the object at a specific location
- pixels
- square box
- intensity or brightness
- brightness
- a —- or —- which consists of 2d or 3d array
- each element in the array corresponds to a specific — within the patient ( this region needs to be studied )
- each element of the array has a —- and/or — value assigned to it which is defined by —- which depend on —– as:
- template or computer generated grid
- physical location
- color and/or brightness
- the user
- measured parameter as : absorption . emission of radiation
all non visuals or computerised medical imaging carry out the following simple procedure which is:
1- —- what is to be imaged
2- apply the appropriate —-
3- measure the received signal as a function of —–( Each element of the matrix corresponds to a physical position within the region of study , The numerical value of each matrix element represents the strength of the signal received at that position.)
- a —–is defined by the user whereby colours or grey scale is assigned to each numerical value
- identify
- technology
- function of location
- color scale
ionising radiation needs to have :
1- frequency :
2- photon energy :
3- wavelength
and they will break bonds and cause electrons to be —
- more than 1 x 10 power 15
- more than 4ev
- less than 300 nm ( uv)
- free
( check slide 9 )
1-X-rays have — d images and they are —- equally well by all materials
2- heavy elements as — are — absorbers of x rays while lighter elements are — absorbers of x rays
3- since x rays can be blacken photographic film , —- can be produced when a body is placed between — and —-
- 2d
- not absorbed equally
- calcium
- good absorbers
- not absorbed well
- shadow pictures
- x ray source and photographic film
—– are electromagnetic radiation (photons) of high energy (10-100 keV).
these rays of different energies are produced by bombarding a material w —-
- x rays
- electrons
1-x rays can interact w atoms in tissue and creates tissue —- aka —-
2- when they are transmitted/detected
3- when they are absorbed/atteunated
4- when they are scattered/detected
- contrast aka artefacts
- are dark and have no interaction
- are bight and have photo-electric
- are artefacnt/blurring as Compton
( check image slide 13 )
1- muscle , fat and tumours are examples of – tissues and all have —-absorption characteristic for x rays and therefrom — to distinguish in standard x ray
2- —- of an x-ray beam is the reduction in its intensity due to the absorption and/or scattering of some of the x-ray photons out of the beam (note: Lambert-Beer Law).
3- the main contrast between :
4- better contrast at:
5- less scattering at — which leads to — and less —-
5- higher energies needed for —
- soft tissue
- attenuation
- bone and other tissue
- at lower x ray energies
- less scattering at lower x ray energies which gives netter quality image and less artifacnt
- higher energies needed for deeper penetration ( check graph important slide 15)
2-d x rays are commonly used to detect —
bone fractures
-DEXA is a — technique which is used to determine the – of the bone hence its —–
- its considered to be a gold standard method for diagnosing —-
- DEXA measures —- and —–
- scanning
- density
- mechanical strength
- osteoporosis and fracture risk
- bone mineral density BMD and is commonly used for hip and lumbar spine but also other bones
-DEXA works by sending —– which are absorbed differently by —- and —
-The ratio of the attenuation coefficients from these X-ray beams are used to calculate —-
- lower the density =
- DEXA is — and takes — and the amount of radiation is — about — of normal chest x ray
- 2 low dose x ray
- bones and soft tissue
- bone mineral density BMD
- greater risk of fracture at low density
- painless
- 10 minutes
- very low
- 10%
-bone densities are often given to a patient as —- or —
- your BMD is compared to – which is:
1- healthy young adult aka :
2- age matched adult aka:
- your BMD is compared w the BMD results from large sample of healthy —- adults of same —- .
- T score is given as the number of — between – and — of the same group
- postive t score idnicates :
- negative t score indicates
- t score or z score
- t score
- z score
- 25-35 yo
- sex and ethnicity
- standard deviation (SD) between your BMD and BMD of the sample group
- your bones are stronger than normal
- bones are weaker than normal
1- Bone density is within 1 SD (+1 or −1) of the young adult mean indicates —-
2- Bone density is between 1 and 2.5 SD below the young adult mean (−1 to −2.5 SD) indicates —
3- Bone density is 2.5 SD or more below the young adult mean (−2.5 SD or l
lower) indicates —-
4- Bone density is more than 2.5 SD below the young adult mean, and there have been one or more osteoporotic fractures indicates —-
- normal
- low bone mass
- osteoporosis
- severe ( establisehd ) osteoprosis
the risk of bine fracture – w every SD below normal.
the person w BMD of 1SD below normal ( t-score of -1) has – the risk for bone fracture as a person w normal BMD . when this info is known ppl w high risk for bone fracture can be treated w goal of preventing future fractures
- doubles
- twice
—- is that the structure of an object can be ‘reconstructed’ from a series of x-ray projections taken uniformly around the object.
consider a thin pencil beam of – passing through a section of tissue w many —– so that the beam have a —-
- CT ( computerised tomography )
- x rays
- different directions
- common crossing point
-From all these projections CT calculates (=computes) the ——
- significant gain in —-
- signal independent of —
- attenuation in each voxel / tiny volume (=3D information)
- tissue contrast and resolution
- tissue thickness
in ct scan:
1-a — array is constructed by a computer
2- each element of array corresponds to a specific — within the patient under asessemnt
3- a — assigned to each element corresponds to the — at the location
4- a — is developed whereby a specific color or greyscale is assigned to particular values of —
5- computer paints by —
6- — is constructed
- 3d
- location
- numerical value
- calculated absorption ( using lac’s from each projection )
- color scheme
- absorption
- numbers
- image
In —– machines, the patient slides through a circular ‘gantry’ containing x-ray sources and detectors, creating a spiral motion, creating many x-ray projections.
modern ct machines
ultrasound is — and — of using —- waves to look at parts of human anatomy
the technology work on principle similar to —
- safe and painless
- sound waves
- sonar
1-We know the — of the ultrasound, so measuring the —- taken to detect a reflected ultrasound wave, allows us to calculate the —- to the reflective boundary
2-The intensity of the reflected ultrasound wave tells us about the —- of the reflecting medium
- speed
- time
- distance
- density so image can be formed
( check slide 33 important )
true or false:
Musculoskeletal ultrasound allows physicians to see, in high resolution, a person’s muscles, tendons, ligaments, nerves and joints,“ (Yale Medicine radiologist)
true
Proton spins within water molecules become aligned to the very strong magnetic field which exists within the ‘bore’ of the —-
1——- (=electromagnetic radiation/photons of ultralow energy, <1 µeV) are used to perturb the alignment of proton spins and their dynamic return to equilibrium
2- gradient coil produce changing —- along different directions needed to probe signals at different location ( >3d info )
3- are — and —
MRI machine ( physics of underlying MRI is complex )
- Short radiofrequency pulses
- magnetic field
- non invasive and harmless
-Proton spins from different tissues return to their —- states at different rates – a difference that can be detected.
measurement of the recovery times include:
- equilibrium
-Spin-LatticeRelaxation or T1, and Spin-Spin Relaxation or T2) allows us to distinguish (contrast) between different tissue types.
mri provded better soft tissue contrast than —
CT
- info:
1- Provides good contrast between gray matter (dark gray) and white matter (lighter gray) tissues, while CSF is void of signal (black).
2- Provides good contrast between CSF (bright) and brain tissue (dark).
