Non- invasive analysis of skeletal structures

Question 1

Why image bone?

Answer 1

Clinical investigation
Research purposes
Forensic puposes

Question 2

Purpose for imaging bone - clinical investigation

Answer 2

Diagnosis of pathologies
Identification of fracture
Pre- surgical visualisation

Question 3

Purpose for imaging bone - Research purposes

Answer 3

Investigation of bone structure

Cortical and trabecular bone:
Within an individuals
Between ontogenetic developmental groups
Between comparative species

Question 4

Purpose for imaging bone - Forensic

Answer 4

Assessment of microscopic trauma

Skeletal observation without defleshing/ destroying - CBRN

Question 5

Imaging techniques - Two dimensional

Answer 5

Plane plate radiography - clinical
Modified plane plate radiography (macro- radiology)
Ultrasonography

Question 6

Imaging techniques - 3D

Answer 6

Computer tomography (CT) - micro or clinical 
MRI- micro or clinical

Question 7

What are 3D imaging systems based on?

Answer 7

2D image capture

Question 8

What are produced at intervals along an individual in 3D imaging ?

Answer 8

single slices

several 2D slices are produced depending on the image being scanned can be more than 1000 slices

Question 9

What is each slice comprised off in 3D imaging?

Answer 9

Pixels ( X*Y)

Question 10

3 dimentional data is comprised of?

Answer 10

Voxels (X Y Z)

Question 11

what does z =?

Answer 11

slice thickness/ interval

Question 12

Resolution =

Answer 12

pixel / voxel size

Question 13

Sliced data is imported as a

Answer 13

data stack

Question 14

What is radiography?

Answer 14

A 2D representation of a 3D structures

Question 15

Problems with radiography

Answer 15

Superimposition
-over/ underlying structures obscure details/ features

Difficult to make accurate measurements due to magnification of image

Question 16

How is radiography useful clinically ?

Answer 16

Cheap
Fast - instant
Low radiation dosage

Question 17

Radiology source -

Answer 17

Beam of x-ray is produced by an x-ray generator
Beam is directed at an object which comprises materials of different densities
A proportion of the x rays are absorbed by dense material of the object

Question 18

Radiology detector-

Answer 18

The remaining x- rays reach a detector where they are viewed as an image

Question 19

Modern digital plates

Answer 19

re-useable and can be processed straight away using specialised reader and software

Question 20

X ray scintillators

Answer 20

materials that exhibit scintillation - the property of luminescence when excited by ionizing radiation

Question 21

Macro radiation

Answer 21

method of enlarging radiographs

Increase object film distance relative to focal film distance

Question 22

What is macro radiation useful for

Answer 22

observing fine details
carpals
petrous temporal
lacrimal system

Question 23

Computer tomography was introduced when and by whom?

Answer 23

Hounsfield - 1970’s

Question 24

What is Computer tomography based on?

Answer 24

radiography and digital detectors

Question 25

What does CT consist of ?

Answer 25

X ray source and detectors mounted on a ring on opposing sides Rotates 360 degrees around subject capturing data in intervals

Question 26

What is different about the detectors in CT scanners compared to those found in x ray radiography?

Answer 26

They do not produce an image | They measure the transmission of a thin beam of x rays through a full scan of the body

Question 27

CT is based on the fundamental principal that ?

Answer 27

the density of tissue passed by the x- ray beam can be measured from the calculations of the attenuation coefficient

Question 28

What is the attenuation coefficient ?

Answer 28

Quantity that characterises how easily a material or medium can be penetrated by a beam of light, sound, particles or other energy matter

Question 29

What units represent the attenuation coefficient?

Answer 29

Hounsfield units

Question 30

Hounsfield scale

Answer 30

Air = - 1000 HU Fat = - 60 to - 120 HU Water = 0 HU Compact bone = +1000 HU

Question 31

CT pros

Answer 31

Availability - most hospitals have facilities Large gantry sizes - up to whole body scans Relatively quick scan and reconstruction - depends on computer power

Question 32

CT cons

Answer 32

Poor special resolution "streak artefact" associated with bone Higher radiation does than radiography Relatively high running costs

Question 33

Micro computed Tomography was introduced by

Answer 33

Feldkamp et al 1989

Question 34

what was Mico computed Tomography designed for

Answer 34

high resolution imaging of bones

Question 35

Pros of Micro CT

Answer 35

Great for quantifications of structural indices which aid in explaining bone form High spatial resolution Good contrast in dry bone

Question 36

Cons of Micro CT

Answer 36

Gantry size does not always allow for imaging whole bone Larger specimen results in lower resolution and loss of detail Most literature centred on animal studies Limited anatomical region can be studied in humans Long scan and reconstruction time Artefact production if specimen is outside field of view

Question 37

Magnetic Resonance imaging

Answer 37

Complex imaging technology based on the excitation of hydrogen nuclei in water

Question 38

what is used to align MRI ?

Answer 38

Powerful magnetic field

Question 39

What is used to alter alignment

Answer 39

Radio frequency fields

Question 40

Detectors in MRI

Answer 40

Used to pick up energy emissions during movement Used to produce a 3D image based on slices Non-ionising radiation

Question 41

Micro MRI

Answer 41

used on a much smaller scale applied to visualise trabecular bone Due to MRI relying on free protons, bone studied requires soft tissue surrounding the bone

Question 42

Micro MRI pros

Answer 42

Good contrast between tissue types especially between bone and soft tissue Non ionizing

Question 43

Micro MRI cons

Answer 43

``` Good but limited resolution for trabecular resolution Limiting resonator size Lengthy scan time scan artefacts Powerful magnetic field Not so good for dry bone ```