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radiology > 4th year > Flashcards

4th year Flashcards

1
Q

what do MF views show?

A

facial bones/skull from either a lateral or AP or basal perspective

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2
Q

which type of MF view is rarely indicated now?

A

basal

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3
Q

collimation

A

the control of the size and shape of the xray beam

- use smallest field of view compatible with diagnostic requirements

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4
Q

where does collimation occur?

A

at the tube head

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5
Q

what feature ensures correct collimation?

A

light beam shows area on patient which will be exposed to primary beam

cross shows where central ray will strike receptor

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6
Q

EO views equipment

A

xray tube head
collimator
cassette with film or digital

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7
Q

intensifying screen

A

min speed 400
have phosphor layer which gives out light when xrays interact with it
- film sensitive to that light

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8
Q

grid

A

thin lead strips adjacent to cassette which attenuate obliquely travelling photons before they reach the film

but for the same number of photons to reach film dose must be increased, otherwise insufficient blackening

lead v good absorber of xrays

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9
Q

OM line

A

ST line
central part of EAM to outer canthus of eye
much more easily visualised

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10
Q

OM vs FP

A

differs by approx 10 degrees

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11
Q

what is OM line used for?

A

radiographic baseline for skull radiographs

  • supposed to mimic angle of the skull base
  • helps get pt in right positioning
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12
Q

FP

A

orbitale to porion
most inferior IO rim to superior EAM

skeletal - select overlying ST

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13
Q

lateral skull

A

similar to a lat ceph - but free positioning and no ST images
shows lat view of whole skull as well as facial bones and upper cervical spine
no cephalostat/wedge for ST profile

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14
Q

indications for lat skull

A

*but increasingly replaced by CT (also detects intra-cranial abnormalities)
facial fractures to show vertical and AP displacement (but both sides superimposed on each other so not widely used)
fractures of skull/skull base
skull pathology (e.g. Pagets, myeloma - see discrete radiolucencies)
pituitary fossa enlargement, sphenoid sinus enlargement

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15
Q

what does an OM show?

A 
orbit
frontal sinus - often asymmetric
MS
zygoma, zygomatic arch
nasal septum
coronoid process
odontoid peg/dens of C2
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16
Q

taking OM

A

OM line at 45 degrees to IR - nose-chin position
mid-sagittal plane perpendicular to IR
inter pupillary line parallel to floor
xray beam perpendicular to IR
centred in midline, level with region of interest

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17
Q

what does AP/PA refer to?

A

direction of beam and position of tube and image receptor relative to pt

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18
Q

PA

A

tube posterior, IR anterior

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19
Q

AP

A

tube anterior, IR posterior

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20
Q

what are MF views usually - PA or AP?

A

PA

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21
Q

when might you do an AP MF view?

A

if eg. can’t put traumatised tissues against IR

- but image less clear

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22
Q

why PA direction?

A

reduced magnification
- objects closer to film are magnified less than more distant objects
- structures we want to see as close to IR as possible
dose reduction
- low energy photons entering back of head are attenuated before they reach radiosensitive tissues e.g. lens
- salivary glands also radiosensitive but can’t do much as in field of view

23
Q

alterations to standard 0 degree OM projection

A

changing angulation of xray beam alters projection of bones onto radiograph
gives better view of some areas e.g. zygomatic arch
gives different view of displacement e.g. displacement at IO rim in zygomatic complex fractures

24
Q

what imaging types are indicated for sinus disease?

A

MRI or CT

25
Q

why is xray not indicated for sinus disease?

A

acute sinusitis can be diagnosed and treated clinically

signs on xray are non-specific and are encountered in asymptomatic people

if persists beyond 10days of tx, CT is recommended when the results could alter management

26
Q

what does a PA mandible show?

A

posterior body, angle, ramus of mandible

superimpositions

  • cervical spine - obscures anterior mandible
  • mastoid process and zygomatic arch - obscures condyle
27
Q

taking a PA mandible

A

OM line perpendicular to IR
- forehead-nose position
mid-sagittal plane perpendicular to floor and IR
interpupillary line parallel to floor
xray beam perpendicular to IR centred between angles of mandible

28
Q

what does a SMV show?

A 
base of skull inc foramina
sphenoid sinus
MS
plain view of mandible inc condyle
zygomatic arches*
29
Q

taking SMV

A 
ensure no history of neck injury/disease
extend H and N as far as possible
OM line parallel to IR
mid-sagittal plane perpendicular to IR and floor
vertex of head contacts IR
beam centred between angles of mandible
30
Q

OM indications

A

(sinus disease - no longer indicated - maxillary, frontal, ethmoid)
middle 1/3 facial fractures - zygoma, le fort
coronoid process fracture

31
Q

imaging for middle 1/3 facial injury

A

XR of facial bones indicated

CT (inc CBCT) specialised investigation

32
Q

imaging for mandibular trauma

A

OPG/XR indicated for uncomplicated fracture
CT (inc CBCT) specialised investigation
MRI - only in specific circumstances

33
Q

PA mandible indications

A 
fractures of angle, posterior body and ramus of mandible - medial and lateral displacement (wouldn't use for condylar heads - CBCT)
cysts/tumours (same areas of mandible) - medial and lateral expansion/destruction - use CBCT if available as more detailed info
facial deformity (often then taken in a cephalostat - PA cephalometric)
34
Q

indications for SMV

A

fracture of zygomatic arch
expansion of more posterior mandible (anteriorly true occlusal as not so good anteriorly)
cranial base pathology (now replaced by CT)

  • lots of superimposition so infrequently done unless 3D imaging not available
35
Q

SMV to show zygomatic arches

A

can make show if need to but don’t normally see as such thin bones
- would need separate exposure
arch very thin so normal beam too penetrating, energy and quantity need to be reduced
exposure factors (kV and time) reduced cf those to show skull
therefore skull underexposed so appearing white

36
Q

Reverse Townes

A

beam from occiput to forehead

good for condylar heads

37
Q

which legislation means you need to do a CE report?

A

IRMER17

38
Q

why should you do a radiographic report?

A 
IRMER17
medicolegal
best practice
records 
audit
39
Q

CE report

A 
list views and justification
grade images
dentition (FDI)
Rxs
RRs/associated pathology
RCTs
caries
supporting bone (indicates)
periradicular changes
anything else

symmetry
margins
bone consistency

40
Q

what shape is most concerning?

A

irregular

41
Q

sclerosing osteitis

A

bone becomes more radiodense due to an infection

42
Q

more radiolucent

A

loss of previously opaque material e.g. bone, teeth

43
Q

more radiopaque

A 
increased density e.g. cortical bone
increased thickness e.g. overlaps
alteration e.g. ST calcification
ST within an air space - replacing air with anything - appears radiopaque
sclerosing osteitis
44
Q

what margin is worrying?

A

ill-defined

45
Q

what does a corticated margin indicate?

A

has to keep remodelling, slow growth

wouldn’t have if aggressive

46
Q

effect on other structures

A

none
displacement (usually indicates slow-growing)
expansion (reasonably slow growing)
resorption (more aggressive)

47
Q

why can well-defined lesions lose their corticated margins?

A

if they become infected e.g. abscess

can mimic malignancy

48
Q

radiological sieve

A 
normal
developmental
traumatic
inflammatory
cystic (typically radiolucent)
neoplastic (benign/malignant)
osteodystrophy
metabolic/systemic
idiopathic
iatrogenic
foreign body
artefact
49
Q

CT

A

multiple axial slices across long axis of pt
can also look at coronal and sagittal images
v high xray dose exam
thin fan shaped beam and line detector

50
Q

CBCT

A

xray beam is a cone
bigger flat panel detector
typically only goes round pt once - single location
hard tissues as not great ST differentiation, whereas CT is both
- don’t do CBCT if need STs
lower radiation dose

51
Q

Justification

A

by practitioner
specific objectives
total diagnostic/therapeutic benefits to individual and society
individual detriment exposure may cause
efficacy, benefits and risks of available alternatives

history and exam only acceptable means of determining which views required

52
Q

clinical indications for CBCT

A 
implant planning
impacted teeth (normal and supernumeraries)
 - location
 - relations e.g. IDC
 - ? related other teeth e.g. RR
pathology - cystic lesions, infections, benign tumours
orthognathic surgery
hypodontia - implant planning
cleft palate - bone defects
dental anomalies - dilaceration, double teeth
endo problems - ECR
autotransplantation
53
Q

Sedentexct

A

safety and efficiency of new and emerging dental xray modality and CT

54
Q

EADMFR basic principles on use of CBCT

A

use only when Q can’t be answered adequately with lower dose method
if evaluation of STs required - medical CT/MRI
use smallest vol compatible with clinical situation
choose resolution compatible with HPA

radiology (5 decks)

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