Radiology Cafe Appendix (Erin) Flashcards
What is the equation for maximum number of electrons in a shell?
2n2 (n = shell number)
What is the equation for Intensity (E) of a photon
E= hf (h = planks constant)
As frequency increases what happens to the energy of a photon
Increases
What is the equation for intensity relative to distance
1 / d2 (d = distance)
What is the equation for photoelectric LAC
Photoelectric LAC = ρZ3 / E3 (ρ = density, Z = atomic number, E = energy)
What is the equation for Compton LAC
Compton LAC = ρ / E
What is the equation for Mass attenuation coefficient
LAC/p
What is the equation for the linear attenuation coefficient
Linear attenuation coefficient (LAC, cm-1) = 0.693 / HVL
What is the equation for factor of reduction relating to HVL
Factor of reduction = 2HVL (HVL = half value layer)
What colour of light is used to read out CR plates
Red light
What colour of light is released when CR plates are read out
Blue light
What material is the scintillation layer in indirect DR plates made from
caesium iodide with thallium (CsI:Tl)
What is the maximum compression used in mammography
200N
What is the typical compression used in mammo
100-150N
What is the image plate in computed radiography made from
barium fluorohalide activated with divalent europium ions.
In indirect DR what colour of photons are released from the scintillation layer
Green
In indirect DR how many light photons are produced per xray photon
3000 light photons in the green spectrum
In indirect DR what is the matrix made from
amorphous silicon layer doped with hydrogen (a-Si:H)
What is the focus to film distance used in mammo
65-66cm
What size is the broad focal spot in mammo
0.3mm
What size is the fine focal spot in mammo
0.1mm
What material of target/filter is commonly used in mammo
Mo/Mo
What material of target/filter is commonly used in mammo for larger breasts
Mo/Rh
Rh/Rh
In fluoroscopy what is the input window made from
aluminium of titanium foil
What material is used as the input phosphor in fluoro
Sodium activated caesium iodide (CsI:Na)
How thick is the Sodium activated caesium iodide (CsI:Na) used in fluoro?
400-500 μm thick
What colour photons does the input phosphor create in fluoro
Blue
What material is the photocathode made from in fluoro
Antimony caesium (SbCs3)
What material is the output screen made from in fluoro
Silver-activated zinc cadmium sulphide (ZnCdS:Ag)
What is the equation for G brightness in fluoro
Gbrightness = Gminification x Gflux (Gminification = minification gain; Gflux = flux gain)
What is the equation for G minification in fluoro
Gminification = (Dinput / Doutput)2 (Dinput = diameter of input screen; Doutput = diameter of output screen)
What is the atomic number of tungsten
74
What is the mass number of tungsten
184
What is the K alpha characteristic radiation of Tungsten
59.3 keV
What is the K beta characteristic radiation of tungsten
67.6 keV
What is the K alpha characteristic radiation of Molybdenum
17.5 keV
What is the K beta characteristic radiation of Molybdenum
19.6keV
What is the K edge of Mo
20keV
What is the K alpha and K beta characteristic radiation of Rhodium
Kα = 20.2 keV
Kβ = 22.7 keV
What is the K edge of Rh
23.3 keV
What 3 factors improve geometrical unsharpness
Small focal spot size
Increasing focus to detector distance
Decreasing object to detector size
What is the equation for multislice pitch in CT
Multislice pitch = beam pitch = couch travel per rotation / total width of simultaneously acquired slices
What is the equation for single slice pitch in CT
Single slice pitch = detector pitch = couch travel per rotation / detector width
What is the fine focal spot size used in CT
0.7mm
What is the broad focal spot size used in CT
1.0mm
What is the CT number of water
0
What is the CT number of fat
-50 to -100
What 2 factors increase maginification
increased object to detector distance
decreased focus to detector distance
What is the CT number if air
-1000
What is the CT number of bone
+1000
What is the CT number of CSF
15
What is the CT number of white matter
20 to 30
What is the CT number of grey matter
37 to 45
What is the CT number od liver
40-60
How is dose measured in CT
mAs/pitch
What is meant by CTDI
Dose to the detector from single gantry rotation
What unit is CTDI measured in
mGy
What is meant by Weighted CTDI
(CTDIw) in CT
Adjusted for spatial variation of dose
⅓ CTDIcentre + ⅔ CTDIperiphery
What is the definition of CTDI vol in CT
Accounts for pitch
CTDIw / pitch
What unit if CTDIw and CTDIvol measured in
mGy
What does DLP stand for in CT
Dose Length Product
How is DLP calculated
Total dose along distance scanned
CTDIvol x distance scanned
What is the range of audible soundwaves
Audible range of soundwaves = 20 to 20,000 Hz
What is the range of waves used in medial ultrasound
Medical ultrasound = 2 to 18 MHz
Equation for velocity in USS
Velocity (c) = √ ƙ / ρ (ƙ = rigidity; ρ = density)
What is the speed of ultrasound in soft tissue
Speed of sound through tissue = 1540 ms
What is the resolution of film screen radiograph
6lp/mm
What is the resolution of digital radiograph
3lp/mm
What is the resolution of digital mammography
5-10 lp/mm
What is the resolution of fluoroscopy
5lp/mm
What is the resolution of fluoroscopy flat panel detector
3lp/mm
What is the effective dose of a CTAP
10mSv
What is the effective dose of a barium enema
7mSv
What is the effective dose of CT colonography
6mSv
What is the effective dose of CT head
2 mSv
What is the effective dose of a CT spine
6mSv
What is the effective dose of CT neck
3mSv
What is the effective dose of CT chest
7 mSv
What is the effective dose of a CXR
0.1 mSv
What is the effective dose of an XR pelvis
0.5mSv
What is the effective dose of mammography
0.4 mSv
What is absorbed dose
Energy deposited per unit mass of tissue
What unit is absorbed dose measured in
Gray
What is the effective dose
sum of (equivalent dose x tissue weighting factor)
What is the equivalent dose
sum of (Absorbed dose x radiation weighting factor)
What is the average background radiation/year
2.7mSv/year
What is the average background radiation from natural sources
2.3 mSv/year
What is the average background radiation from medical exposure
0.4 mSv/year
What is the radiation weighting factors of xrays, gamma rays, beta particles and positrons
1
What is the radiation weighting factors of alpha particles
20
What is the radiation weighting factor of neutrons 100keV-2MeV
20
What is the radiation weighting factor of Neutrons <10keV
5
What does ALARP stand for
As low as reasonable practicable
Is ALARP under IRR or IRMER
Both
What is the role of IRMER
Governs all medical and non-medical exposures to patients
What is the effective dose limit per year to a radiation worker >18yrs
20mSv per year
What is the effective dose limit per year to members of the public
1mSv per year
What is the effective dose limits to radiation workers <18yrs
6mSv per year
What is the effective dose limit to carers/comforters
5mSv per year
What is the effective dose limit for pregnant employees
1mSv for remainder of pregnancy
What is the dose limit to abdomen of person of reproductive capacity
13mSv in any consecutive 3 months
What is the equivalent dose limit to lens of the eye for employees >18yrs
20mSv
What is the equivalent dose limit to lens of the eye for employees<18yrs
15mSv
What is the equivalent dose limit to lens of the eye for any other person
15mSv
What is the equivalent dose limit to extremities for employees>18yrs
500mSv
What is the equivalent dose limit to extremities for employees<18yrs
150mSv
What is the equivalent dose limit to extremities for any other person
50mSv
What is the equivalent dose limit to skin for employees >18yrs
500mSv
What is the equivalent dose limit to skin for employees <18yrs
150mSv
What is the equivalent dose limit to skin for any other person
50mSv
At what effective dose does someone need to be a classified worker
> 6mSv/year (i.e 3/10 of the dose limit which is 20mSv)
At what equivalent dose dose someone need to be a classified worker
Equivalent dose >3/10 of any dose limit
i.e >15mSv to lens of eye
>150mSv to skin or extremities
What classifies an areas as a controlled area
Area where staff likely to receive effective dose >6mSv
15mSv equivalent dose to eyes
Or >3/10 of any relevant dose limit
External dose rate exceeds 7.5uSv/hr over working day
Dose rate <7.5uSv/h over working day BUT instantaneous dose rate at ANY point exceeds 100uSv/h
What classifies an areas as a supervised area
Person working in area likely to receive dose of >1mSv/yr
Or equivalent dose of >1/10 any relevant dose limit
What does MARS78 govern
administration of radioactive substances
What does RSA govern
storage and safe disposal of radioactive materials
What does Radioactive Material (Road Transport) (Great Britain) Regulation 2001 govern
governs transport of radioactive substances by road
What is the MHRA guidelines for whole body exposures of patients in MRI (normal and pregnant) in Tesla
4 Tesla
What is the MHRA guidelines for whole body exposures of patients in MRI (controlled) in Tesla
8 Tesla
What is the MHRA guidelines for whole body exposures of patients in MRI (research purposes) in Tesla
No limit
What is the MHRA guidelines for exposure of staff for whole body (in Tesla)
<2 Tesla for whole body
What is the MHRA guidelines for exposure of staff for limbs (in Tesla)
<5T for limbs
At what gauss is an MRI area controlled
5 gauss
0.5mT boundary
What is the lead equivalence of lead aprons for 100kV and 150kV
0.25mm for 100kV
0.35mm for 150kV
What is the lead equivalence in mm of thyroid shield
0.5mm
What is the lead equivalence in mm for lead glasses
0.25 x 1.0mm
What is the lead equivalence for lead gloves in mm
0.5-1.0 mm (modern gloves)
Old gloves 0.25 mm
Can a person be the referrer, practitioner and operator
yes
What is the role of the referrer (IRMER)
Health care professional entitled in accordance with employer’s and local procedures to request and refer individuals for medical exposure
Need to supply practitioner with sufficient medical information
What is the role of the practitioner (IRMER)
Required to justify all medical exposures and decide if exposure is in patient best interest (e.g person who vets requests)
Can be radiologists or radiographer
What is the role of the operator (IRMER)
Carried out and optimises the medical exposure
ALARP
What is the role of the employer (IRMER)
Implements IRMER and allocated individuals with roles
Provides written procedures and protocol
Ensures staff are trainer
Responds to incidents
What is the risk of cancer per 1mSv in adults
1 in 20,000
Does effective dose concern deterministic of stochastic effects
Stochastic effects
Does equivalent dose concern deterministic or stochastic effects
Deterministic