HomeStretch CRACK Physics Mammo/Flouro Flashcards
What is the optimal keV and kVp for mammo?
ideal energy for mammo is 16-23 keV
to get this energy, a voltage of 25-30 kVp is used ( general Dx uses 50-120)
What is the target anode for mammo?
Moly or Rho
(gen rad uses republic of Tungsten)
What is the K-edge of moly? how about Rho?
Mo = 20 keV k edge
Rho = 21
(never use Rh target with Mo filter)
K edge filter combos (target/filter)
Mo/Mo
Mo/Rho
Rho/Rho (for denser breasts)
can’t use a Rho/Mo since the kedge of a Mo filter will block the characteristic xrays of Rho.
Mammo uses a focal spot of?
General X-rays use focal spot of?
Mammo = 0.1 and 0.3 mm
General = 0.6 and 1.2 mm
Spatial resolution of:
Screen film mammo?
Digital mammo?
DR?
CT?
MR?
- Screen film mammo = 15 lp/mm
- Digital mammo = 7
- DR = 3
- CT = 0.7
- MR = 0.3
FRAR version of mammo, focal spots, mA and exposure time?
smaller focal spots, lower mA (because of smaller focal spot and heat limits), and increased exposure time
exit window for mammo
exit window for general x-ray?
mammo = beryllium for BooBs
General = glass
most testable advantage for compression in mammo?
dose/scatter reduction
Grids in mammo versus General?
Mammo uses a 4-5 grid ratio (general uses 6-16)
mammo bucky factor = 2 and 5 for general x-ray
Magnification increases with?
Greater object to detector distance
Less source to object distance
are mag views lower or higher dose?
Higher, since the boob needs to get closer to source (inverse square law)
mag view focal spot, ma and exposure time
mag view uses a smaller focal spot, about a quarter of the mA and about triple exposure time relative to conventional “contact” mammo
mammo optical denstity and air kerma level relative to general x-ray?
mammo hhas higher opical density and higher receptor air kerma (100microGy versus 5).
Mammo
PPV1
PPV2
PPV3
PPV1 = cases from positive screening (ie callbacks - BR-0,3,4,5) benchmark = 4.4%
PPV2 = where biopsy is recommended (BR4,5) Benchmark = 25%
PPV3 = results of biopsy = biopsy yield malignancy = PBR (positive biopsy rate); benchmark = 31%
Mammo departments need to be “accredited and certified” every ___ years
3 years
Who is the evil overlord behind MQSA?
FDA! (Boobs are food. . .)
minimum number of megapixels on a mammo station?
3MP
Mammo appropriate target range for medical audit:
recall rate = ?
cancers/1000 screened?
recall rate = 5-7%
cancers / 1000 screened - 3 - 8
Mammo QA intervals:
Processor QC:
Darkroom Cleanliness:
View box conditions:
Phantom evaluation:
Repeat analysis:
Compression test:
Darkroom Fog:
Screen-Film Contrast:
- Processor QC: Daily
- Darkroom Cleanliness: Daily
- “process your cleanliness daily”
- View box conditions: Weekly
- Phantom evaluation: Weekly
- view the phantom weekly
- Repeat analysis: Quarterly
- QR - repeat quarterly
- Compression test: Semi-annually
- Darkroom Fog: Semi-annualy
- Screen-Film Contrast: Semi-annualy
- compress and screen-film contrast the fog semi-annually
Mammo privileges are bestowed upon you if you do what?
read 240 mammos during a 6 month period under direct supervision
3 months of formal training
60 documented hours of mammo education
what is the required dose for the phantom in mammo?
300 millirads (3mGy) (this is measured with a grid)
1mGy is without a grid
no actual regulation for human breast
How many digital spot films = the dose of 1 minute of fluoroscopy?
5-10 digital spot films
Differences between Flouro and regular Dx
- Regular Dx
- mA 200-800
- kVp = 50 - 120
- Very short exposure times
- focal spot 1.0 - 1.2 mm
- Flouro
- mA 0-5
- kVp = 50 - 120
- Longer exposure times
- focal spot 0.3 - 0.6 mm
Flouro - in what scenario is the tube not under the patient?
Any trivia about that setup?
GU radiology set up (bladder close to receptor)
lens dose is higher!
what is the scintillator used in image intensifiers?
CsI
Steps in Image intensifiers
- x-rays hit the input phospor (CsI)
- xrays turned into light
- light hits the photocathode
- light gets converted to e-
- e- go through electostatic focusing lens
- this hits the output phosphor
- converted to light
Brightness gain
flux gain
minification gain
conversion gain
Brightness gain = flux X minification gain
flux gain = accelerating e- in via focusing lens = more flux gain
minification gain = reducing image size (output versus input) = increased brightness
conversion gain = effieciency of an II in changing incident x-rays into light at the output source (older I.I.s are worse and more dose!)
when conversion gain falls to 50% - get a new one
Geometric versus electronic mag (zoom)
geometric = bring thing closer to x-ray source
electronic mag = decrease input field of view and keep input phosphor the same, which will decrease brightness, but the ABC kicks in
Both increase radiation (1.4-2x for electronic mag)
for general radiology, if you increase geometric mag what do you do to sharpness?
how about in mammo?
resolution decreases (blurring increases)
in mammo its the opposite
(for reasons beyond the scope of these flash cards)
What is the best position of the II and x-ray tube?
II very close to patient
x-ray tube distace from patient farther
Less minification (smaller FOV) = more/less mag? = more or less bright?
Less minification (smaller FOV) = Magnified = Less Brightness
opposite is true
Automatic brightness control circuit limiter max number?
87 mGy/min = 10 R/min
KERMA = ?
Air KERMA = ?
Kerma-Area product = ?
What does electronic mag to air kerma and KAP?
- KERMA = Kinetic Energy Release per unit Mass
- TOTAL amount of energy deposited from ionizing radiation
- Air KERMA = estimation of how many photons are in a unit of air prior to the energy striking the skin
- KAP = amount of kerma X cross sectional area = Dose Area Product
- the total radiation potentially incident on the patient
- KAP = dose x cross-sectional area
- Electronic mag increases Air Kerma, but dose not increase the KAP
What is the normal air kerma limit?
What is the high level control limit?
87 mGy/min = 10 R/min
176 mGy/min = 20 R/min
flouro pincusion artifact is due to ? how about S-distortion?
Flare or glare artifact?
Saturation artifact?
pincusion due to large FOV while S is due to earth’s magnetic field (or nearby MRI)
Flare = images become brighter with transition to less attenuation when you transition to heavy attenuation to minimal
Saturation = dose cranked up to penetrate very dense object like metal -> regions around metal very bright
Steps in Flouro Flat panel detector
- xrays go through Grid
- hits the flat panel detector then CsI needles and turns photons into light
- photodiode array then absorbs light and concerts to e-
- and then e- hit read out element (transistors and gates)
Flouro pitch
different that in CT
linear dimension of a detector element
Fill factor
Fill factor = senstive area / pitch2
What is binning?
takes several detector elements (DELs) and makes a larger DEL to reduce amount of data (reduce quantum mottle)
Key point = binning improves SNR
What is frame averaging (recursive filtration)?
image process feature that adds several images together with different weight factor
improves SNR but increases motion and ghosting artifact.
regular versus pulse flouro
which has higher mA?
at hat rate pulses / second is pulsed and regular flouro same dose?
if you decrease pulse flouro rate by 50% what percent do you decrease dose?
pulse flouro has higher mA
at 30 frames / second they both have same dose
50% reduction in pulse rate = 30 % reduction in dose
Flouro spatial resolution limiting factors and actual numbers?
FDP Systems
II systems
FDP = Detector element size (3.0 lp/mm)
II = TV system (2.0 lp/mm and 2.0-4.0 lp/mm for angio)
Flouro QA
How is spatial resolution tested?
How is distortion check for?
lead bar pattern
mesh screen or plate
kVp for angio study (using Iodine)
kVp for Barium study?
70kV
>100kV
What does increasing kVp do to dose in general radiology? how about CT?
decreases in gen rad
increases in CT
What does magnification due to KAP?
no net change in KAP, but does increase air kerma
What does collimation do to KAP? how about air kerma?
collimation decreases KAP but does nothing to peak skin dose
When are grids used in flouro?
everthing BUT extremities or peds
The dose standing 1 meter from the patient is what fraction of the dose received by the patient?
1/1000 of the dose received by the patient
how much dose can lead apron decrease?
90%
for flouro lateral views, where should you stand to decrease your dose?
side with the image receptor
Timeline and dose for the following:
Transient erythema
Main erythema
Epilation (hair loss)
Desquamation (skin peeling)
Secondary ulcer
Dermal atrophy
Telangiectasis
Dermal necrosis
- Transient erythema: 2-24 hours; 2 Gy
- Main erythema: 2 weeks; 6 Gy
- Epilation (hair loss): 3 weeks; 3 Gy = temporary and 7 Gy = permanent
- Desquamation (skin peeling) = 4 weeks; Dry = 14 Gy and wet = 18 Gy
- Secondary ulcer: > 6 weeks; 24 Gy
- Dermal atrophy > 52 weeks; 10 Gy
- Telangiectasis > 52 weeks; 10 Gy
- Dermal necrosis; >52 weeks; > 12 Gy
Dose levels that trigger follow to detect skin reactions
Peak skin dose
cumulative air kerma
KAP
flouro time
- Peak skin dose = > 2Gy
- cumulative air kerma = 5Gy
- KAP = 500 Gy /Cm2
- flouro time = 60 min
a 5 second DSA gives how much times more radiation relative to conventional flouro?
10X
US regulatory dose limit for a radiologist?
Limits to eyes
Lead apron thickness requirement?
Sentinal event? when to do root cause analysis?
50 mSv / year
US limit on eyes = 150 mSv/year while IRCP = 20 mSv/year
0.25mm thickness
cumulative dose > 1500 rads (15Gy) to a single field - root cause analysis within 45 days or fry!
