Radiology Flashcards

Question

What do protons and electrons in an atom have in common?

Answer 1

An atom contains equal numbers of protons and electrons.

Answer 2

The mass number is at the top (Z+N) | The atomic number is at the bottom (No. of protons)

Answer 3

``` Protons = 11 Neutrons = 12 Electrons = 11 ```

Answer 4

A charged atom or molecule. The number of electrons does NOT equal the number of protons. eg. anion or cation

Answer 5

An ion where there are more electrons than protons so therefore a negative charge.

Answer 6

An ion with more protons than electrons so therefore a positive charge.

Answer 7

Alpha particles, Beta particles, Gamma rays

Answer 8

``` 2 protons and 2 neutrons (helium nucleus) Size - Large Charge - Positive Speed - Slow Penetration - 1-2mm in tissue Energy - 1-8MeV (mega electron volts) Damage potential - extensive ionisation ```

Answer 9

``` Electrons (fast electrons) Size - small Charge - negative Speed - fast Penetration - 1-2cm in tissue Energy - 100keV-6MeV Damage potential - ionisation ```

Answer 10

``` Electromagnetic radiation Size - Nil Charge - Nil Speed - very fast Penetration - can pass through tissue Energy - 1.24keV-12.4MeV Damage potential - ionisation ```

Answer 11

``` Do not occur naturally. Not involved in radioactive decay. Not particulate - no mass or weight Very fast No charge. Identical to gamma rays with lower energy values. Cause ionisation. ```

Answer 12

When it occurs in living cells. Can cause damage to tissues - eg. cataracts Can cause damage to DNA directly or produce chemicals that do this damage - tumours or cancer.

Answer 13

The properties of different parts of the spectrum depend on the wavelength of the particular area eg. radiowaves large wavelength, Gamma rays short wavelength

Answer 14

At the speed of light. (299,792,458m/s)

Answer 15

A packet of energy.

Answer 16

Electron volts (eV) or volts (V)

Answer 17

Cycles per second or Hertz (Hz)

Answer 18

Metres or nanometres (10 to the -9)

Answer 19

the distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave. S-shaped.

Answer 20

Frequency is the number of waves that form in a given length of time. It is usually measured as the number of wave cycles per second, or hertz (Hz).

Answer 21

Frequency (Hz) = cycles/seconds

Answer 22

``` 220/240 volts 13 amp current (usually) 50Hz circuits can be fused at 3, 5 or 13 amps. Cookers etc have 30 amp circuits. ```

Answer 23

the power or force that causes a current to move along a wire of for electrons to move across a gap from a cathode to an anode.

Answer 24

1 volt is the potential difference between 2 points on a conducting wire, carrying a constant current of 1 amp when the power dissipated between the points is 1 watt.

Answer 25

from -ve to +ve.

Answer 26

No electricity supply is alternating.

Answer 27

By the vibration of electrons.

Answer 28

Energy is not created nor destroyed, it can only be changed from one form to another.

Answer 29

X-ray source, object, receptor.

Answer 30

Horizontal or vertical

Answer 31

maxilla or mandible

Answer 32

``` DPT Lateral cephalogram Posterior-anterior mandible Lateral-oblique mandible Occipito-mental views of facial bones ```

Answer 33

``` Detect apical infection Assess periodontal problems Trauma - fractures of tooth or bone Morphology pre extraction Position/presence of unerupted teeth Endodontics Pre-post apical surgery Evaluation of implants ```

Answer 34

``` 1) Paralleling technique periapical use holders for positioning receptor parallel to tooth accurate/reproducible image 2) Bisected angle periapical can be done without holder operator dependent not reproducible ```

Answer 35

Paralleling technique

Answer 36

uses holders to facilitate positioning allows accurate geometry of image receptor parallel to tooth X-ray beam perpendicular to tooth/receptor minimises magnification accurate/reproducible image holders are bulky and may not be tolerated by all patients. Can reduce patient dose to patient by reducing repeats and does not expose patients fingers (see bisected angle periapicals)

Answer 37

digital or film

Answer 38

bite block - retains the receptor indicator arm/rod - fits into bite block Aiming ring - slides onto arm to establish alignment of collimator with receptor

Answer 39

Anterior or posterior

Answer 40

Accurate geometry of image

Answer 41

the vertical plane of the tooth should be positioned so that it is parallel to the long axis of the tooth. Film and tooth parallel vertically

Answer 42

horizontal plane must be parallel to the dental arch under examination.

Answer 43

If the tooth and film are not parallel

Answer 44

At 90 degrees, right angle.

Answer 45

elongation and fore-shortening

Answer 46

1) X-ray source (focal spot) to receptor distance | 2) Object (tooth) to receptor distance

Answer 47

Receptor position - horizontal and vertical Beam alignment - horizontal and vertical Distance

Answer 48

Horizontally/ Landscape

Answer 49

Vertically/portrait

Answer 50

Mouth size Film size Gag reflex Digital sensor size and shape

Answer 51

0, 1, 2, 4

Answer 52

Under 10 -> 0 or 1 | Over 10 -> 2

Answer 53

Left or Right Periapical - towards the crowns of the teeth Bitewing - towards the palate

Answer 54

Ionising Radiations Regulations 2017 (IRR17) and Ionising Radiation (Medical Exposure) Regulations 2017 (IRMER17)

Answer 55

The tube head is where the domestic electric supply is converted into ionising radiation so that we can produce the X-rays.

Answer 56

At the cathode

Answer 57

It is a very fine wire made of tungsten - high mp and high tensile strength

Answer 58

``` Firstly the domestic supply current (13A) goes through a step down transformer small current passed along it 8-10mA electrons are excited - they vibrate wire gets hot - may give off light excited electrons lost from outer shells electrons form cloud around cathode ```

Answer 59

Small tungsten target embedded in copper

Answer 60

-ve electrons bombard +ve anode high energy electrons come to sudden stop or decelerate and energy form changes. 99% heat, 1% X-rays

Answer 61

it will give rise to X-rays in the wavelength or power required for dental imaging.

Answer 62

Domestic supply is 240V so we need to increase it with a step-up transformer within the tube head again which is made out of copper coils.

Answer 63

Continuous spectra - Bremsstrahlung or breaking radiation, wide range of photon energies Characteristic spectrum - emitted by loss of electrons from K and L shells, depends on material in anode

Answer 64

An electron from the cathode is attracted to the positively charged atom of tungsten in the anode. As it moves round the nucleus it loses its energy, maybe not all of it but there will then be an electron with much less energy moving off to react with other atoms, much of the energy given off is heat but you also get some Bremsstrahlung radiation produced too.

Answer 65

wide range of photon energies small deflections most common - many low energy photons little penetrating power - need filtering out large deflections less likely - few high energy photons Maximum photon energy directly related to kV across X-ray tube

Answer 66

There are multiple electrons being attracted towards the anode and so we get multiple reactions and multiple X-ray photons being produced. These all have a wide range of energies.

Answer 67

when there is a small deflection around the nucleus (most common), we have low energy X-ray photons produced. They have little penetrating power and would be absorbed by the body therefore they need to be filtered out as it is absorbed radiation that gives rise to X-ray dose.

Answer 68

The absorbed radiation

Answer 69

Large deflections are less likely and give rise to high energy photons, therefore there are going to be few of them produced.

Answer 70

the kV used across the X-ray tube

Answer 71

for characteristic radiation to be produced an incident electron has a direct hit with an electron in the K shell, it knocks the K shell electron out which is called the ejected orbital electron. The initial electron may also be expelled from the atom as an inter-incident electron and it may have less energy now. The K shell is now deficient of one electron so it is unstable, therefore an electron from the L shell falls down to fill the space. However, that electron has too much binding energy so it gets rid of the excess energy as an X-ray photon. The gap in the L shell is then filled by an M shell electron and so on until you reach the outer shell.

Answer 72

X-ray tube needs to be operating above 69.5kV for the characteristic spectrum to be produced.

Answer 73

only Bremsstrahlung radiation not tungsten characteristic radiation

Answer 74

The electromagnetic spectrum

Answer 75

Ionising and non-ionising radiation

Answer 76

the larger the wavelength the more likely we are to be talking about non-ionising radiation as wavelength gets shorter, energy of photons increases and this is where ionising radiations form

Answer 77

random change in direction after hitting something

Answer 78

deposition of energy in tissues (represents dose)

Answer 79

number of X-ray photons in a defined area of the beam - further we are from the source, the more the intensity of photons decreases

Answer 80

reduction in intensity of beam due to scattering and absorption

Answer 81

removal of electron from a neutral atom to give -ve and +ve (atom) ions.

Answer 82

the ability of photons to pass through or into tissues/materials

Answer 83

1) completely scattered with no loss of energy 2) absorbed with total loss of energy 3) scattered with some absorption and loss of energy (mix) 4) transmitted unchanged (no scattering, no absorption, no loss of energy)

Answer 84

radiation passing down and scattered elsewhere in the patient's body

Answer 85

``` it travels in straight lines in free space X-ray photons form a divergent beam can travel through a vaccum Penetrate matter can be absorbed ```

Answer 86

``` Not detectable by human senses produce a latent image on film emulsion Cause ionisation can cause biological damage cause certain salts to fluoresce and emit light ```

Answer 87

the radiation dose is the amount of radiation absorbed by the patient.

Answer 88

Low energy photons - therefore they are the ones most likely to cause damage

Answer 89

Their wavelength

Answer 90

No - people believe microwaves can also be damaging and they are a type of non-ionising radiation

Answer 91

the technical term for the item the X-ray image is formed on ie. film, plate or digital sensor

Answer 92

some photons do not have enough energy to make a useful interaction with the receptor and this scatter can degrade the image.

Answer 93

1827 and it required an exposure time of 8 hours.

Answer 94

Film or Digital

Answer 95

Direct action film and indirect action film

Answer 96

Solid state sensor and photo-stimulable phosphor

Answer 97

Dental intra-oral. X-rays act directly on silver halide crystals in film emulsion.

Answer 98

Dental Extra-Oral. Light from intensifying screens act on silver halide crystals in film emulsion. The X-ray photons react with the intensifying screens to produce photons which expose the film to produce the image.

Answer 99

CCD = Charge-coupled device CMOS = complimentary metal-oxide semiconductor They work by converting light into electrons. The info is then collected by a computer programme and made into an image.

Answer 100

PSP = Photostimulable phosphor plate Latent image produced by interaction of X-rays with phosphor layer on plate. The phosphor coating is exposed to X-rays which causes a reaction with the phosphor which is known as the stable excited state. The plate is then dropped into the vista scan unit where it is scanned by a red laser. This is then the unstable excited state. The blue light emitted is collected and converted into the image.

Answer 101

Scan PSP Plates

Answer 102

Phosphor plate = used with existing film holders, tolerated well by patients, plates easily damaged, relatively expensive, sensitive to background radiation Solid state sensor = only used with its own holders, not tolerated well by patients, sensors are very expensive, easily damaged, image resolution better than PSP.

Answer 103

one pale side with a phosphor coating (coating can be of various compounds eg. barium fluoride). This is the side the image is formed on. Other side is black and shows size of film and orientation dot. This is the back of the plate.

Answer 104

Phosphor layer exposed to X-rays X-ray energy stored in electrons of phosphor crystals (trapped signal) - latent image plate inserted into scanner phosphor layer scanned by red laser stored energy released as blue light light detected by photodetector and sent to signal digitiser (ADC = Analogue to digital converter) ADC converts light to digital signal - each pixel assigned numerical value according to intensity Numerical values represent different shades of grey which are used in image.

Answer 105

After a PSP plate has been scanned and image obtained there is still residual trapped energy in phosphor electrons after scanning. Image on plate is erased by exposing phosphor to bright light (releases any remaining trapped energy in phosphor electrons). Plates then ready to re-use.

Answer 106

Front to back | Front cover, scintillator layer, silicon wafer, back cover

Answer 107

Front cover Scintillator layer - converts X-ray energy to light Silicon Wafer - converts light into electrical signal Back cover - often incorporates a cable to carry signal to PC (or wireless)

Answer 108

either caesium iodide or gadolinium oxysulphide

Answer 109

X-rays hit scintillator layer (caesium iodide or gadolinium oxysulphide) reaction gives off light which hits photosensitive cells in silicon wafer layer electrons within each cell (pixel) are released and these form a charge (voltage) which its converted into an image by the computer. Each cell is connected to its neighbour and the signal converted to the image is from a line of neighbouring cells.

Answer 110

CMOS is very similar to CCD Only difference is that the photocells are electrically isolated therefore a signal (voltage) is sent from each individual cell (pixel) rather than a line of cells (pixels).

Answer 111

There is no orientation dot. With many radiographs it can get confusing and be easy to look at an image in the wrong orientation.

Answer 112

CCD but CMOS catching up

Answer 113

No chemicals, faster processing, easy archiving, easy image transfer, image manipulation, dose reduction

Answer 114

expensive-damage, reduction in resolution due to pixel size, archiving-back up, easy image transfer-security issues, image manipulation, dose reduction-shorter exposure=drop in image resolution

Answer 115

High exposure, too much radiation given

Answer 116

Low exposure, not enough radiation

Answer 117

No, there must be some form of back-up to allow access to images in case something goes wrong, eg. CD, DVD, remote hard drive

Answer 118

PACS - Picture Archiving and Communication System

Answer 119

Most NHS hospitals in Scotland subscribe to a company called Carestream to provide PACS. In Tayside, images are initially uploaded to the local PACS and then national PACS server which is in Livingstone. Therefore you can access them anywhere in Scotland as long as the hospital uploads to PACS.

Answer 120

Tend to come in size 2 only. Can make X-raying anterior teeth more difficult due to the size of receptor.

Answer 121

Dr Edmund Kells - Dentist in New Orleans Prolific inventor - eg. surgical aspirator, 40+ patents 1885 employed first female dental assistant Supported conservative cavity prep suggested "saving" pulp-less teeth 1st to take radiographs in America Noticed adverse effects of radiation on hands of other dentists but claimed he was immune. He later suffered changes to skin and lost a number of fingers to surgery and developed a tumour on his hand.

Answer 122

Those we know WILL occur

Answer 123

Those which MAY occur

Answer 124

Deterministic effects definitely occur with specific doses Threshold dose - below this the effect does not occur SOMATIC effects Radiotherapy - use of somatic effects in positive way

Answer 125

1) Acute - radiation sickness 2-10Sv whole body irradiation. Death >10Sv whole body irradiation 2) Chronic - hair loss, cataracts, sterility, obliterative endarteritis

Answer 126

non-deterministic effects of radiation occur at random. There is no threshold dose. Damage affects patient and future children. Amount of damage not related to dose. Somatic effects - development of malignancy Genetic effects - congenital abnormality which may include malignancy. For genetic effects to occur reproductive organs need to be exposed to radiation.

Answer 127

Non-deterministic - this is the issue. | We do not expose patients to sufficient radiation to reach threshold dose.

Answer 128

estimated 26%

Answer 129

20.5 million

Answer 130

1) Type of radiation (we only use X-rays) 2) Tissue being irradiated (diff tissues diff sensitivity) 3) Age of the patient

Answer 131

0.0003-0.022mSv

Answer 132

0.0027-0.038mSv

Answer 133

0.0022-0.0056

Answer 134

1mSv (same as general public)

Answer 135

``` As Low As Reasonably Practicable ```

Answer 136

Although the risks from ionising radiation in dentistry are low, there are still a number of people who will die yes.

Answer 137

1 in 1 million

Answer 138

The younger a patient is, the greater the risk of developing adverse effects.

Answer 139

``` <10 = 3 10-20 = 2 20-30 = 1.5 30-50 = 0.5 50-80 = 0.3 >80 = negligible ```

Answer 140

Brazil nuts, butter beans, bananas, potatoes, carrots, red meat, avocado, beer, water, peanut butter - mainly from radioactive potassium

Answer 141

Banana equivalent dose

Answer 142

Chest scan = 70,000 BED = 7mSv

Answer 143

the information vs the radiation dose to the patient

Answer 144

avoid unnecessary radiographs use of selection criteria film speed - preferably use F speed kV of machine - higher the kV, lower the dose Rectangular collimation - keeps dose lower than round beam Collimated DPT viewer - restricts beam to area of interest Regular servicing of machines

Answer 145

The higher the kV of the machine, the lower the radiation dose to the patient.

Answer 146

The further away we are from the source, the less likely we are to be exposed to many X-ray photons. The intensity of radiation is proportional to 1/(distance squared) ie. you double the distance then you have quarter the intensity across the area

Answer 147

The area around the patient and the X-ray tube where only the patient should be present, the rest of the controlled area should be considered a no go zone.

Answer 148

The controlled area is 1.5m in radius for X-ray machines operating at less than 70kV. It also extends in the primary beam for as long as it would take for the intensity of the radiation to be almost minimum.

Answer 149

Behind a protective barrier with the red button that makes the exposure also behind the barrier.

Answer 150

2m or behind appropriate shielding

Answer 151

the kV of the machine

Answer 152

Intra oral radiographs

Answer 153

Outer plastic wrapping - keeps dry, saliva free, protects from light damage (fogging), indicates orientation (white side towards X-ray tube) Black paper - protects from light leakage, stiffens and supports film, prevents crimp/pressure marks Lead foil - mix of lead and aluminium, absorbs X-rays, prevents back scatter, distinct pattern embossed in lead Film - direct action - multiple layers in itself

Answer 154

Base - plastic (polyester or cellulose), blue anti glare Adhesive layer on both sides of that Emulsion layer on both sides of that Protective outer layer of Gelatin

Answer 155

Silver halide crystals suspended in gelatin. Silver bromide, silver iodide or a combination. Gelatin allow even distribution of crystals and absorbs liquid readily to allow processing.

Answer 156

To stick the emulsion to the base.

Answer 157

An additional protective layer of gelatin.

Answer 158

The X-ray photon hits silver halide crystal within emulsion. Silver halide crystal becomes sensitised. Latent image formed (not visible to naked eye but made so by chemical reactions in processing).

Answer 159

The reduction of silver bromide crystals to black metallic silver.

Answer 160

The sensitivity of film to X-rays. The exposure required to produce a given amount of blackening (optical density) on an image.

Answer 161

Size of crystals in the emulsion. Larger the crystals the faster the film speed. Faster the film speed the lower the amount of X-rays required to produce an image.

Answer 162

The larger the crystals the faster the film speed.

Answer 163

DPT and Lateral Cephalogram

Answer 164

Indirect action films

Answer 165

Indirect action films

Answer 166

The light produced

Answer 167

Base - polyester Reflective layer Phosphor layer - fluorescent phosphors, emit light when excited by X-rays The light produced is in proportion with the energy of the X-ray photon Supercoat - protects phosphor layer from damage

Answer 168

Base - polyester Reflective layer Phosphor layer - fluorescent phosphors, emit light when excited by X-rays The light produced is in proportion with the energy of the X-ray photon Supercoat - protects phosphor layer from damage

Answer 169

They allow a reduction in exposure and therefore a reduced dose to the patient BUT also a reduction in the detail of the image.

Answer 170

Radiographic film susceptible to damage by pressure marks, bends and crimps. Pressure sensitises the silver halide crystals. Handle with care, hold corners/outside.

Answer 171

Cool but not too cool, Dry but not too dry. Away from radiation - X-rays and heat Stock rotation to prevent using old film

Answer 172

Converting the latent image into a visible image

Answer 173

the reduction of the exposed silver halide crystals to black metallic silver and then making this image permanent.

Answer 174

Manual, instant and automatic

Answer 175

Develop - make latent image visible Wash - stop development and remove dev from film (only in manual processing) Fix - make image permanent Wash - stop fix and remove residual fixer Dry - easier handled, prevent damage

Answer 176

Feed in roller, developer rack, fixer rack, wash rack, dryer.

Answer 177

Phenidone and hydroquinone

Answer 178

The sensitised silver halide (iodide/bromide) crystals are acted upon by phenidone and hydroquinone which involves the chemical reduction of silver bromide to silver plus bromide. Silver is then in the form of black metallic silver. Giving blackening of the film.

Answer 179

Phenidone and hydroquinone

Answer 180

Calcium carbonate

Answer 181

Potassium bromide

Answer 182

sodium sulphite

Answer 183

working temperature

Answer 184

1) Time - too long = dark, too short = light 2) Temperature - too hot = dark, too cold = light 3) Concentration - too strong = dark, too weak = light

Answer 185

Makes the image permanent

Answer 186

change unexposed silver halide crystals to soluble compound so that they can be washed away. Acid maintains the pH and neutralises the developer.

Answer 187

1) ammonium thio-sulphate 2) acetic acid (maintains pH) 3) aluminium chloride 4) sodium sulphite 5) water

Answer 188

the image will be removed

Answer 189

It will appear to have a green tinge and will not archive well.

Answer 190

Between development and fixing and then again between fixing and drying. It stops the action of the developer and reduces carry over. Removes unexposed silver halide crystals made soluble by fixer.

Answer 191

only between fixing and drying | removes unexposed silver halide crystals once made soluble by the fixer.

Answer 192

Film will feel tacky. May also have a green or silvered appearance. Will not archive well - it will deteriorate.

Answer 193

Ensures it is dry before being handled and also reduces the possibility of damage to emulsion.

Answer 194

``` Consistent less operator dependent temperature controlled time controlled less chance of damaging film ```

Answer 195

very operator dependent if done well can be as good as automatic temp must be monitored time must be accurate

Answer 196

``` chemicals in pouch attached to film very quick no large amount of chemicals to dispose of convenient films do not archive well ```

Answer 197

Control of Substances Hazardous to Health

Answer 198

skin sensitisation

Answer 199

allergic contact dermatitis

Answer 200

Occupational asthma

Answer 201

Persistent cough

Answer 202

Possible carcinogen

Answer 203

10 or more room volumes per hour

Answer 204

Goggles, respirator, chemical resistant apron, chemical resistant gloves (not latex)

Answer 205

Look at the packaging for the warning signs.

Answer 206

detecting caries, monitoring caries, assessing periodontal status, assessing existing restorations

Answer 207

long axis of film horizontal usually one done on each side image 4 to 8 usually image crowns and 1/3 roots

Answer 208

long axis of film vertical 2 done on each side image the premolars and molars will image more of root than horizontal bitewing

Answer 209

Caries assessment | Perio assessment

Answer 210

caries assessment | perio assessment - when you need to see more of the root and supporting bone.

Answer 211

1) Film and object (tooth) parallel 2) Film close to object 3) X-ray beam perpendicular to object and film

Answer 212

Always use a holder

Answer 213

1) Rigid plastic - holds film accurately, assists X-ray tube positioning, uncomfortable 2) Paper tab - comfortable, X-ray tube positioned by eye, inaccurate positioning

Answer 214

Horizontal overlap - sometimes difficult to avoid, crowding or tilting of teeth acceptable if less than half of enamel superimposed can miss carious lesions must show EDJ and dentinal half of enamel

Answer 215

mis-positioning of X-ray beam

Answer 216

long source to object distance | short object to receptor distance

Answer 217

always to the palate

Answer 218

Adults - 2 only Child over 10 - 2 Child under 10 - 0 or 1

Answer 219

Can reduce the dose to the patient by up to 50%

Answer 220

Helps to minimise risks.

Answer 221

A guideline advocates good practice and expert opinions - often contains "should" Legislation HAS to be followed - often contains "must"

Answer 222

Radiation Protection Advisor must have one appointed must consult them when planning new surgery, radiation overdose etc. They establish controlled area. Name and contact details should be in radiation protection file. RPA and Medical Physics expert can be the same person

Answer 223

Radiation Protection Supervisor usually dentist or senior member of staff must be adequately trained to ensure compliance with IRR2017 and local rules

Answer 224

Name of RPS and MPE Name of person with legal responsibility for compliance - usually employer Controlled areas - identified + described Contingency arrangements (must be rehearsed) Details + results of dose investigation levels Name of RPA and contact details Personal Dosimetry arrangements Arrangements for pregnant staff Reminder of IRR17 obligations Must be displayed where X-ray equipment is

Answer 225

Medical physics expert (MPE) and RPA (Radiation Protection Advisor) They are not always the same person

Answer 226

Advising on IR(ME)R compliance and they need to be involved in development and review of all dental procedures.

Answer 227

Employer Referrer Practitioner Operator

Answer 228

The referrer, practitioner and operator. They must be entitled by their operator to undertake that role. It must be within their scope of practice and they must be trained and competent to undertake the role.

Answer 229

Entitlement of duty holders identification of the patient demonstrate staff training and competence quality assurance of procedures/documentation clinical audit

Answer 230

Appoint RPA/MPE and RPS | Have and ensure staff read the LOCAL RULES

Answer 231

establish recommendations for selection criteria establish recommendations for radiation dose levels ensuring critical evaluation of every image is carried out, including where appropriate factors relating to patient dose.

Answer 232

All radiographic exposures must be justified

Answer 233

The patient's history and examination - it should be based on presence of disease and rate of progression and diagnostic accuracy of the imaging technique.

Answer 234

Yes, the decision on whether to take radiographs or to not take radiographs should always be documented in the patient's records.

Answer 235

It helps to overcome the wide variation in practice and minimise or prevent any inappropriate radiographic examinations.

Answer 236

"descriptions of clinical conditions derived from patient signs, symptoms and history that identify patients who are likely to benefit from a particular radiographic technique" ie. which radiograph should we take in a particular clinical situation

Answer 237

All radiographs must be clinically evaluated and findings recorded in the patients records. They may include the quality of the radiograph - is it diagnostic or not, and any unusual factors relating to exposure or dose to the patient. Even if everything is normal it should be documented.

Answer 238

A registered medical practitioner or other health professional who is ENTITLED in accordance with the employer's procedures to refer individuals for medical exposure to a practitioner.

Answer 239

Supply sufficient info to practitioner to allow exposure to be justified. State that there is a net benefit to the patient Signed request form, given details to allow correct identification of patient.

Answer 240

Registered health care professional. In dental practice this usually means a registered dentist to take responsibility for an individual medical exposure Practitioner has big role in justification

Answer 241

will exposure cause change to prognosis or management of patient? are other radiographs/reports available? does radiograph requested relate to history and exam of patient? have risks and benefits been assessed? could other techniques with lower dose be utilised?

Answer 242

With no additional registration qualification they have limited entitlement as an operator - can process radiographs either conventionally or digitally With additional qualification they can take radiographs on "prescription" of another dental registrant

Answer 243

"Prescription" of radiographs

Answer 244

According to GDC they can prescribe radiographs and take, process and interpret various film views in GDP. Qualified for limited entitlement as referrer, operator and practitioner but this must be clarified with employer.

Answer 245

They can take and process radiographs and other images related to providing removable dental appliances. This assumes entitlement as an operator. Patients with natural teeth or implants would need to be seen by a dentist before the CDT can start treatment.

Answer 246

They can do everything that other DCP can do. Eligible to be entitled as referrer, operator and practitioners for all dental related radiography.

Answer 247

The dentist, dental hygienist or therapist, suitably qualified dental nurse, a clinical dental technician

Answer 248

The Operator

Answer 249

The dentist

Answer 250

Record of: training, competence in areas of - referrer duties, operator duties, practitioner duties. Signed by duty holder and employer you are ENTITLED by.

Answer 251

Preferably annually but minimum of every 3 years. Must include representative patient doses and routine maintenance by clinicians and manufacturer/supplier must be carried out.

Answer 252

Caries - depending on risk factors Perio disease - depending on severity and site Ortho assessment - possibly only from specialists Oral surgery Should be evidence based or specialist opinion

Answer 253

Anyone offering assistance to a patient during examination. Their potential dose from procedure must be quantified and taken into account when justifying examination. Will need to give informed consent.

Answer 254

inform the patient of any dose much greater than intended. Good practice and duty of candour legislation. Also should inform the referrer.

Answer 255

No this is unacceptable an individual approach/prescription is required.

Answer 256

``` Knowledge of: how image is acquired anatomy disease process Understand effects of: positioning, exposure, processing and for digital imaging - the computer algorithms and computer factors. ```

Answer 257

When there is significant demineralisation. Must be distinguishable from enamel and dentine.

Answer 258

Bitewings - usually horizontal | Paralleling periapicals can be used

Answer 259

If there is periodontal bone loss as well as possible caries.

Answer 260

Crowns of teeth and coronal portion of roots contact points with little/no overlap alveolar bone crest distinguish enamel from dentine pulp chamber any overhangs or deficiencies in restorations

Answer 261

cervical burnout or translucency visual perception - contrast below restoration air/lip shadow in premolar region dentine surrounding radio-opaque zone under amalgam radiolucent restorations

Answer 262

Overlap, technique, anatomy, exposure factors, 2D image

Answer 263

Long cone should be used - a near parallel beam

Answer 264

12-18 months (deciduous)

Answer 265

thick, close together, horizontally aligned

Answer 266

finer, more widely spaced, no obvious alignment

Answer 267

Radiolucent line representing PDL radiopaque line representing lamina dura Trabecula pattern and density of surrounding bone

Answer 268

Contrast, resolution or superimposition

Answer 269

No apparent changes OR possible widening of periodontal ligament space loss of lamina dura at apex further inflammatory spread = perio bone loss

Answer 270

no bone destruction seen OR | dense sclerotic bone periodically (sclerosing osteitis)

Answer 271

circumscribed, well defined, radiolucent area periapically with sclerotic bone surrounding radiolucency sometimes described as rarefying osteitis

Answer 272

Think of a well taken bitewing as the basis for a perfect paralleling periapical.

Answer 273

film is parallel to long axis of the tooth X-ray beam at 90 degrees to film and tooth long cone should be used - a near parallel beam

Answer 274

Accurate images Positioning devices determine the angulations reproducible on different visits by different operators relative positions of film, teeth and x-ray beam are always maintained

Answer 275

The X-ray photons overpenetrate or burn out the thinner tooth edge and create the radiolucent area that mimics cervical caries

Answer 276

Designed to assist the clinician and patient in making decisions about appropriate healthcare for certain specific circumstances

Answer 277

Horizontal bitewings

Answer 278

Vertical bitewings supplemented with parallel periapical views if perio-endo lesion suspected

Answer 279

Bitewings +/- paralleling periapicals

Answer 280

paralleling periapicals

Answer 281

Assess the fault and categorise it. Is the film diagnostic? use bright light to assess dark films. consider repeat exposure if not diagnostic

Answer 282

full mouth periapical films

Answer 283

difficult to take paralleling films of mobile teeth | difficult to use film holders and bite blocks if opposing teeth are missing

Answer 284

film/image receptor is placed as close to tooth as possible usually in contact with crown but be distance from root apex long axis of tooth and film form an angle which is mentally bisected X-ray tube head positioned so that beam is at 90 degrees to bisecting angle Length of image should be equal to length of tooth - laws of similar triangles

Answer 285

to separate the roots of teeth, overcome superimposition, assessing root fractures, localising unerupted teeth, diagnosing apical pathology(when parallel technique can't be used) and when it's okay to have a distorted view.

Answer 286

Consider using an occlusal view eg. oblique occlusal view

Answer 287

``` modified bisecting angle technique mandible and maxilla anterior and lateral shows teeth from crown to apex distortion often occurs superimposition away from central area easy for patients ```

Answer 288

When an area is too large to be imaged by a periapical for patients who retch children who cannot tolerate periapicals parallax views - help assess relative position of pathology or unerupted teeth

Answer 289

oblique and true occlusal views anterior oblique is often called 45 degrees film and long axis of incisors are at 90 degrees bisected angle of 45 degrees beam is angled at 90 degrees to the bisecting plane and therefore hits the film at 45 degrees

Answer 290

X-ray beam at 90 degrees to film Teeth look like buttons Often taken to check for submandibular duct calculi

Answer 291

finding the exact position of a structure that cannot be seen clinically. Overcoming limitations of 2D images.

Answer 292

90 degrees

Answer 293

``` assessing buccal-palatal r-ship of unerupted teeth to dental arch position of foreign bodies expansion/destruction of bone position of salivary calculi separating multiple roots for RCT assessing the displacement of fractures ```

Answer 294

Two views/radiographs taken of the same object with a change in angulation of beam. Usually taken to determine buccal/palatal position of non-visible object. Can be horizontal or vertical

Answer 295

an organised effort by staff to ensure that the diagnostic images produced are of sufficiently high quality to consistently provide adequate diagnostic information at the lowest possible cost and the least possible exposure to the patient.

Answer 296

Human error

Answer 297

Introducing simple systems, SOP improving working environment encourage reporting - without blame

Answer 298

the patient

Answer 299

staff and public but also deals with patient protection in relation to equipment

Answer 300

Set up and participate in quality assurance programme. Named person, details of procedures involved, frequency of procedures involved, frequency procedures carried out, frequency records are audited, all of this must be in writing.

Answer 301

image quality, X-ray equipment, processing (film and digital), working procedures, training, audit.

Answer 302

Audit the images we produce: 1) image quality rating system 2) film reject analysis

Answer 303

monthly, quarterly or at least every 6 months

Answer 304

``` Diagnostically Acceptable (A) - no errors or minimal errors in either patient preparation, exposure, positioning, image processing or image reconstruction and of sufficient image quality to answer the clinical question Not Acceptable (N) - errors in either patient prep, exposure, positioning, image processing or image reconstruction which render the image diagnostically unacceptable ```

Answer 305

Acceptable: Digital = no less than 95%, film = no less than 90% Unacceptable: Digital = no greater than 5%, film = no greater than 10%

Answer 306

Excellent - no errors of patient preparation, exposure, positioning, processing or film handling

Answer 307

Diagnostically acceptable - some errors in patient prep, exposure, positioning, processing or handling which do not detract from the diagnostic utility

Answer 308

Unacceptable - errors in patient prep, exposure, positioning, processing or handling which render the radiograph diagnostically unacceptable

Answer 309

1 > 70% 2 <20% 3 < 10%

Answer 310

Collect all rating 3 films, at end of each month assess these and categorise faults - eg. exposure, positioning, processing etc. Act on this, repeat every month and compare results

Answer 311

assess>grade(1,2,3)>results(analyse)>feedback>back to start

Answer 312

cool and not too humid, avoid direct sunlight and UV, preferably in light protection/cross infection barrier envelope. If not used for more than 24hrs after plate erased (exposure to light) it should be erased again.

Answer 313

It is a daily check of the developer as when the developer begins to be exhausted the images become paler. Step wedge used and when it is radiographed it will produce an image showing "steps" of blackening from pale grey to dark grey/black. Do this and process it in fresh chemistry - makes standard reference film. Expose step wedge film daily. Check films for any obvious changes in densities ie. drop of one step from reference film.

Answer 314

light entering daylight loading system/darkroom. Safelight - filter unsuitable for film or too close to work surface (1.5m) Test - coin test

Answer 315

Open intra-oral x-ray packet and remove film while hands are in glove box or in darkroom under safelight conditions. Place coin on film for specific amount of time (eg. 5 mins or average working time), remove coin and process film. Check the processed film for light fogging, repeat test for every different type and speed of film in practice. Helps to assess safelights and identify if there is light leakage causing fogging of films.

Answer 316

visual check for physical change weekly and radiographic monthly

Answer 317

visual check weekly and radiographic monthly

Answer 318

Radiograph monthly

Answer 319

DPT Postero-anterior mandible Lateral-oblique mandible

Answer 320

Lateral cephalogram (skull) Occipito-mental view (0, 10 and 30 degrees) (face) Sialography

Answer 321

Referring to the region of the mandible between the mental foramina.

Answer 322

AP - beam pointing to front of patient PA - beam pointing to back of patient OM - beam entering the patient at the occiput and exiting between the mental foramen

Answer 323

line from out canthus of the eye to EAM - represents the base of the skull

Answer 324

Inferior orbital border (IOB) to upper border of the EAM - also known as the anthropological base of skull.

Answer 325

ala of nose to tragus of ear.

Answer 326

Increase in the field of the beam causes more scatter to be produced. This adds to the background fog.

Answer 327

As the field of X-rays required to cover the entire skull is much larger, more scatter will be produced. If left unchecked this will add to background fog and produce a greyer image lacking in contrast.

Answer 328

It is made of narrow strips of lead alternating with plastic. It stops photons scattered in the patient from reaching the film and avoids degrading the image and reducing contrast while allowing the straight high energy photons to pass through . They can be fixed or moving/oscillating depending on the equipment, sometimes with fixed ones you may get stripes caused by the strips of lead, moving ones do not have this issue.

Answer 329

90 degrees

Answer 330

45 degrees

Answer 331

90 degrees

Answer 332

1) position of patient relative to film 2) position of x-ray beam relative to patient 3) angle of beam relative to patient/film

Answer 333

10 degrees

Answer 334

30 degrees

Answer 335

patient faces film, nose and forehead touching film holder, radiographic baseline at 90 degrees to film (horizontal). Aim centre of beam at midline of patient at height of mid ramps (roughly below the occiput).

Answer 336

Looking at front of patient the midline is generally between the eyes. (nose unreliable as often deviate) From the back look for external occipital protuberance.

Answer 337

Fractures, cysts, good visualisation of posterior body and ramps, limited view of head/neck of condyle, midline can be obscured by spine, requested along with DPT.

Answer 338

Reduced magnification of facial structures (remember always want object as close to receptor as possible) Reduced dose to eyes.

Answer 339

Fracture of body, ramps and condyle, pathology eg. cysts, assessment of wisdom teeth, dental assessment in special needs patient, caries in children who will not tolerate bitewings

Answer 340

If a lateral mandible view was taken (not obliquely) the two halves of the mandible would be superimposed making it difficult to examine. Taking it obliquely allows you to separate the rami to image one side at a time. you must oblique the mandible in the vertical plane to achieve full separation of the rami. Will only receive useful info from rami closest to receptor.

Answer 341

Patient supine, position patient for area to be imaged, rotate machine to horizontal plane, angle 25 degrees towards head, tilt patients head towards the film

Answer 342

Patient holds cassette parallel to area being examined. Tube head positioned beneath lower border of body of the mandible on side not under examination. Aim tube towards teeth under exam, angle tube head slightly upwards. This will project the opposing body of the mandible up and therefore away from the area of interest.

Answer 343

patient holds cassette parallel to area being examined. tube head positioned aiming along occlusal plane below ear towards the maxillary and mandibular teeth to be examined. Aims through the radiographic keyhole.

Answer 344

The triangular space between the back of the ramps and the cervical spine

Answer 345

angulation can cause vertical distortion of teeth | maxillary teeth are not always shown clearly

Answer 346

X-ray beam may not pass directly between the contact points of the teeth therefore causing overlapping on film.

Answer 347

Orthodontics to assess the relationships of the teeth to the jaws and the jaws to the rest of the facial skeleton. Can only be done with Cephalostat. Visualises soft and hard tissue

Answer 348

mid sagittal plane parallel to film/receptor, Frankfort plane horizontal, centre of X-ray beam aimed at EAM, teeth in occlusion and ear rods used to give standardised positioning.

Answer 349

A lateral cephalogram. The exposure factors and consequent dose is slightly higher. The lead protection is a thyroid shield as the thyroid is one of the more radiosensitive anatomical structures.

Answer 350

Ceph films should have a magnification rod shown on the image to allow for the calculation of any magnification that has occurred.

Answer 351

Aluminium filter. Positioned over anterior part of face, designed to attenuate beam in anterior facial region which allows visualisation of bone and soft tissue on one film, despite the relatively high exposure factors needed for the facial bones. If digital - soft tissues made visible by software.

Answer 352

Reduce beam size to reduce dose. | Some units have the facilities to collimate the beam to help to reduce the dose.

Answer 353

0 degrees, 10 degrees and 30 degrees

Answer 354

Patient faces film holder, nose and chin touch holder, radiographic baseline at 45 degrees to film, aim centre of X-ray to midline of patient through base of nose, angle beam at 10 or 30 degrees to feet.

Answer 355

Projects dense bones of skull base down away from facial structures. Improves view of zygomatic arch, gives diff perspective.

Answer 356

Wrong exposure selection, not enough time in developer, developer temp too low, incorrect dilution of developer

Answer 357

Sensitometry, routine processor maintenance, topping up developer when needed, appropriate exposure selection, regularly check X-ray tube output

Answer 358

Too high an exposure, processing faults, developer too hot, too much time in developer, dilution of developer too concentrated

Answer 359

Insufficient fixing during processing | Think time, temp, dilution

Answer 360

Time, temp and dilution

Answer 361

Dark spots

Answer 362

Clear spots

Answer 363

residual chemicals that are not properly washed away.

Answer 364

Caused by static electricity discharging on the film and it often resembles lightning or a tree. Can be caused when a film is pulled quickly from the packet when the atmosphere is dry.

Answer 365

The white line artefact is caused by a spec of dust on the sensor in the processing tower which has blocked the transfer of data from one line of pixels.

Answer 366

Positioning, artefacts, correct film size selection.

Answer 367

The film packet is back to front.

Answer 368

A radiograph showing a slice or section of tissue in focus. Multiple tomograms of sequential planes would build up to give 3D images eg. CT

Answer 369

Linear tomography

Answer 370

Film and tube move in opposite directions, only structures within a certain slice (focal trough) are sharp on image and objects further from the trough are more blurred.

Answer 371

synchronised movement of tube head and film/sensor, rotate around patient in horizontal plane, circular path, single centre of rotation, focal trough is an arch of circle, limited use in dentistry as the dental arch is not part of a circle

Answer 372

elliptical shape

Answer 373

Horse shoe shaped - narrow anteriorly, wider posteriorly

Answer 374

Light is emitted in all directions light affects larger area of film than a single photon image quality (fine quality) is not as good as direct action film

Answer 375

Phosphor plates | Solid state sensors/CCD

Answer 376

patient should be positioned so that focal trough corresponds to dental arch as much as possible X-ray tube head moves behind patient from R to L Receptor moves in front from L to R Bite block used to bring mandible into same focal trough as maxilla Only a narrow section exposed at any one time OR rotating sensor receives info constantly

Answer 377

minimal discomfort images teeth and facial bones shows vertical height of mandible and IDC shows maxillary sinus walls dose is reduced compared to full mouth of intra-orals shows both sides on one radiograph

Answer 378

lesion not clear on intra-orals, gross disease, symptomatic third molars, Orthodontic treatment, mandibular fractures, disease of TMJ, implant planning or review

Answer 379

lack of fine detail, superimposition of other soft and hard tissues, air shadows, exposure time up to 16 seconds, magnification of image due to object/receptor distance, requires patient co-operation

Answer 380

remove metal jewellery, glasses etc. patient stands with spine straight holding handles, bites incisors edge to edge in groove on bite block, light beam markers, head immobilised, tongue to roof of mouth, stand still

Answer 381

beam fan shaped and angled up at approx 8 degrees to horizontal. Different part of film exposed to film at any time.

Answer 382

Current guidelines state no justification for use of lead aprons, does not protect from internal scatter. Interferes with image on DPT as can be projected onto image and may also catch the tube as it rotates.

Answer 383

Limits field size.

Answer 384

Projection changes as machine rotates left side of image - lateral projection of RHS of mandible and spine Central portion - acquired with tube behind patient and sensor in front so its a PA projection right side of image - lateral projection of LHS of mandible and spine

Answer 385

Images of a structure on one side which are projected onto another side eg. angle or ramus of mandible, hard palate, foreign bodies (earring, surgical clips) They are always seen at a higher level than the real structure because the beam is pointing upwards at an angle of 8 degrees.

Answer 386

If a patient has a class III incisor relationship

Answer 387

Not the gold standard, frequently requested when strong gag reflex, poor fine detail, overlap, superimposition of anatomy/air

Answer 388

Cone Beam Computerised Tomography, developed by Sir Geoffrey Newbold Hounsfield

Answer 389

Hounsfield Scale Air = -1000HU Water = 0HU Cortical bone = +1000HU

Answer 390

High kV tube - 120kV, much higher than dental machines.

Answer 391

Tomographic image - looks at slice of tissue and these slices can be stacked together to form the 3D images.

Answer 392

Intracranial - bleed, infarct, tumour Trauma Evaluation of osseous lesions Salivary glands Neoplasia (benign/malignant) - primary tumour, metastases Orthognathic assessment and treatment planning Implant planning

Answer 393

Not subject to same magnification and distortion as plain radiographs Multi-planar (manipulate, reconstruct images) - avoids superimposition Images bone and soft tissue

Answer 394

Patient dose, artefacts (metallic objects, amalgam in head and neck produce pattern), may require intravenous contrast to distinguish tissues, expensive, interpretation more difficult

Answer 395

Dentascan - software available mainly for implant planning.

Answer 396

In Atkinson Morley Hospital Wimbledon 1st Oct 1971. Brain/head only.

Answer 397

Lower radiation dose than medical grade CT, overcomes issues of 2D imaging, should only be used if info gained will impact patient care, some machines have a large field of view and are usually in hospital departments.

Answer 398

Prior to the scan an initial positioning view is usually taken to ensure that the area of interest is in the field of view. This is a very short exposure with the tube and receptor at opposite sides of the patient. The image produced is a lateral one with R and L superimposed.

Answer 399

patient either seated or lying supine depending on machine. X-ray tube and flat panel receptor opposite eachother and rotate around patient at same time. Receptor sends signal to computer where an image will appear on screen. X-ray beam is cone-shaped and area of interest is inline go path of beam for whole rotation, passing through structures in full 360 degrees.

Answer 400

Axial - through horizontally Sagittal - front to back Coronal - through shoulder to shoulder

Answer 401

Localisation of unerupted tooth assessment of resorption from unerupted tooth cleft palate patients orthognathic surgery assessment Few indications for restorative dentistry - only if conventional radiographs are unhelpful. Periapical lesions, root canal anatomy, perforations, dental trauma, dental anomalies

Answer 402

Assessment of third molars to IDC, assessment of third molar morphology, implant assessment, pathology involving jaws, TMJ bone surfaces, facial fractures

Answer 403

Scan times, volume size-FOV, type of equipment used, part of maxillofacial region being imaged.

Answer 404

multi-planar reformatting -MPR- allows image to be viewed from all directions Geometrically accurate, fast scanning time, compatible with other software, good spatial resolution, lower radiation dose than medical CT

Answer 405

Patients must be still to avoid artefacts, soft tissues not imaged well, radio-dense materials like restorations and RF material produce beam hardening artefacts- streak artefacts, images can be difficult to interpret

Answer 406

No, additional training is required for the referrer, practitioner, operator

Answer 407

MRI (magnetic resonance imaging), Ultrasound, Nuclear medicine (radio-isotope scanning), Combination of modalities including PET

Answer 408

Images soft and hard tissues, differentiate different tissues, head injury (can see bone and brain), speed (compared MRI), multi-planar, cost and availability usually cheaper

Answer 409

Patient radiation dose, dose for head around 2mSv, often requires intravenous contrast to distinguish tissues, artefact, expensive in comparison with plain radiography

Answer 410

Small voxels result in a higher resolution image

Answer 411

Small size voxels requires longer scan time which results in higher dose.

Answer 412

involves protons (water), magnetic field, radio frequency pulses - patient is placed in a magnetic field, the water protons align in this field, another magnetic field is applied at an angle and then removed, the protons oscillate/resonate back to their original position, this resonance is measured by the computer.

Answer 413

no ionising radiation, excellent for viewing soft tissue and also cancellous bone (changes in marrow, infection, infiltration cortex breach), multi-planar

Answer 414

T1 weighted - water dark T2 weighted - water bright Generally T1 for anatomy, T2 for pathology.

Answer 415

Multiple contradictions - pacemakers, artificial heart valves, surgical clips particularly intra-cerebral aneurysm clips, 1st trimester pregnancy FB with eyes/orbit. Danger of strong magnetic field (might clear bank card!), units need to be away from car parks and facilities, availability and cost of scanning (waiting lists), scan times can be long and noisy, claustrophobia

Answer 416

MRI shows the soft tissues of the joint well, disc can be seen, normal disc is bow tie shaped, often difficult to image, scanned in open and closed positions, takes a long time and patients complain of the noise.

Answer 417

high frequency sound waves >13MHz, transducer placed on skin sound waves bounce off tissues and back to the probe, cannot travel beyond hard tissues, limited use around the jaws

Answer 418

no ionising radiation, no harmful effects, ideal for superficial soft tissue structures, multi-planar, operator dependent, real time images, blood flow, can be used to guide fine needle aspirate or biopsies.

Answer 419

operator dependent, difficult to interpret, superficial tissues, cannot penetrate bone

Answer 420

Neck swelling - tissue of origin, solid/cystic, characteristics (benign/malignant? Salivary glands - neoplasm, HIV, Sjogrens syndrome, calculi in salivary glands or ducts Blood flow - carotid artery disease, r-ship to lesion and lesion supply, guidance for biopsy/drainage.

Answer 421

inject isotopes which are unstable and defat emitting radioactive particles (a, b) or radiation Isotope selected according to tissue to be imaged. Radioactive compound concentrated in target tissue indicating: increased activity (hotspot), reduced/no activity (cold spot) radioactive emissions detected by gamma camera

Answer 422

99mTc short half life (6 hours) ensures lower patient dose. Easily available, can be bound easily to diff substances, red blood cells, taken up by thyroid and salivary glands. MDP - Methylene diphosphonate - bone

Answer 423

salivary gland function, condylar growth in mandibular asymmetry, thyroid, bone metastases, osteomyelitis

Answer 424

Poor resolution, appearances not specific and may not be able to distinguish between different pathological processes, radiation dose.

Answer 425

Positron emission tomography combined with CT Images are acquired with both technologies at the same time and superimposed on each other. The radioactive contrast can be given orally, inhaled or into a vein, depending on what is being investigated. Shows up where areas are more active than normal, scans do not have as much fine detail as CT alone.

Answer 426

Diagnose cancer, cancer staging, radiotherapy planning, assess how effective treatment has been, to distinguish between active disease and scarring following treatment

Answer 427

The exposure required to produce an optical density of 1.0 above background fog. Thus, the faster the film, the less the exposure required for film blackening and therefore the lower the dose to the patient.

Answer 428

Vertical angulation too large

Answer 429

Vertical angulation too small