Radionuclide Imaging Flashcards

Question

What is the main feature of a PET tracer?

Answer 1

They are positron emitting

Answer 2

Positron emitting tomography

Answer 3

15-O 11-C 13-N 18-F

Answer 4

20 minutes

Answer 5

10 minutes

Answer 6

10 minutes

Answer 7

110 minutes

Answer 8

Fluoro-Deoxy-Glucose

Answer 9

- Short half life - Cyclotron required for production - Relatively low energy gamma photons - Biological elements - Has a wide range of clinical applications - Mainly used in oncology - More natural elements - Most research and investigations are carbon based

Answer 10

Less time to do imaging Expensive Cyclotron needs to be close to the scanner

Answer 11

alpha beta gamma

Answer 12

4He 2 Travel straight but has a coulomb interaction with tissue the stops them within a few micrometres of travel Not possible to image

Answer 13

4He 2 Travel straight but has a coulomb interaction with tissue the stops them within a few micrometres of travel Not possible to image

Answer 14

0 e OR 0 beta+ -1 +1 Interact with coulomb force but because they are small, they do not travel straight Average tissue range is 1-5mm In vivo imaging possible Positrons annihilate and create 2 gamma particles (511kev)

Answer 15

``` Interact with matter through the photoelectric effect and compton scattering High energy (100-500KeV) helps them escape human tissue ```

Answer 16

``` Collimator Scintillation crystal Light Guide PMTs Processing electronics Lead casing ```

Answer 17

``` Collimator Scintillation crystal Light Guide PMTs Processing electronics Lead casing ```

Answer 18

Creates a 2D image It is a projection image No depth information Can determine direction not location

Answer 19

``` Emits gamma ray Collimators stop any non parallel rays Scintillator absorbs gamma photons Emits optical photons Converted to electrical current ```

Answer 20

Absorption: gamma ray ejects electrons (via Compton or photoelectric effect) Excitation: the electron is excited to the conduction band (can move through the crystal) Relaxation: the electron relaxes back to valence band Emission: subsequent emission if visible light (characteristic) radiation

Answer 21

Sodium iodide NaI Doped in thallium

Answer 22

Doped in thallium to achieve efficient scintillation at room temperature. Without this, it only scintillates at liquid nitrogen temperatures

Answer 23

``` Emits gamma ray Collimators stop any non parallel rays Scintillator absorbs gamma photons Emits optical photons Converted to electrical current ```

Answer 24

Absorption: gamma ray ejects electrons (via Compton or photoelectric effect) Excitation: the electron is excited to the conduction band (can move through the crystal) Relaxation: the electron relaxes back to valence band Emission: subsequent emission if visible light (characteristic) radiation

Answer 25

Sodium iodide NaI Doped in thallium

Answer 26

Doped in thallium to achieve efficient scintillation at room temperature. Without this, it only scintillates at liquid nitrogen temperatures

Answer 27

``` Gamma ray emitted Collimators block out non-parallel rays Scintillator absorbs gamma rays Converts to optical photons Optical photons are converted to electrical current ```

Answer 28

Absorption: gamma ray ejects electrons (via Compton or photoelectric effect) Excitation: the electron is excited to the conduction band (can move through the crystal) Relaxation: the electron relaxes back to the valence band Emission: with subsequent emission of characteristic frequency radiation (visible light)

Answer 29

NaI Sodium iodide Doped with thalium

Answer 30

1. High scintillation efficiency (high gamma to light conversion) 2. Linear conversion (light yield is proportional to deposited energy) 3. Low optical absorption (optically transparent crystal) 4. Short decay time of induced luminescence 5. Able to be manufactured in large sizes to image patients 6. Index of refraction = glass for efficient coupling to PMTs 7. Low cost

Answer 31

Very cheap to produce Puts it into the visible light range Allows it to occur at room temperature

Answer 32

Stops more gamma rays

Answer 33

The air/solid interface between the scintillation crystal and the PMT photocathode would cause total internal refractions

Answer 34

In an vacuum Incident light photons enter the PMT through the photocathode Light strikes the photocathode A photoelectron is emitted The electron strikes anodes of ascending voltages It gains energy and it ejects further electrons from the next dynode It produces an amplified signal

Answer 35

It ensures that there is little leakage of light from the crystal before it reaches the PMT

Answer 36

Silicon grease or oil of a similar optical index to the crystal and photocathode should be used as a light guide between the surfaces. Regular re-greasing at services

Answer 37

The air/solid interface between the scintillation crystal and the PMT photocathode would cause total internal refractions

Answer 38

Incident light photons enter the PMT through the photocathode Light strikes the photocathode A photoelectron is emitted The electron strikes anodes of ascending voltages

Answer 39

For each event, a signal is generated in each PMT The information is used to work back the initial location There will be more signal at some PMTs due to the position - light will hit multiple PMTs are light does not travel in a straight line

Answer 40

Pulse height analyser | Collimation

Answer 41

Excludes scatter Scattered photons will generally have lower energy than non-scattered It measures the energy and only accepts those that fall within a certain range +/- X%

Answer 42

Bandwidth - the range of energies that will be accepted

Answer 43

It is experimental There are small inaccuracies If the range is too small, may exclude some primary rays

Answer 44

Excludes all radiation not parallel to the detector | Reduces scatter

Answer 45

99m-Tc | 140keV (low energy)

Answer 46

``` Needs to be made of lead Size Septal thickness Hole depth Hole size Distance from detector ``` Different radioisotopes need different collimators

Answer 47

Get a decrease in resoltion

Answer 48

Many photons are absorbed by the collimators and this results in a loss of information and a reduction in resolution

Answer 49

99m-Tc | 140keV (low energy)

Answer 50

Increased thickness = Increased imaging energy Decreased sensitivity Septa must be thick enough to stop radiation with the energy of the imaged isotope

Answer 51

High sensitivity - allows most rays through Low resolution Decrease radiation for the same count

Answer 52

Each collimator hole sees a smaller region.

Answer 53

``` Increased hole depth = Increase resolution Decrease specificity Increase radiation dose required No change in the imaging energy ```

Answer 54

Decrease hole size = Decrease sensitivity Increased resolution No change in imaging energy

Answer 55

Smaller holes means more holes | This means more area is taken up from lead septa which decreases sensitivity

Answer 56

Each collimator hole sees a smaller region.

Answer 57

Increasing the distance Increased noise in the image Decreased image quality

Answer 58

Positron emitted Finds nearby electron and annhiliates with it This creates 2 gamma photons (511kEV) that spreads in opposite directions

Answer 59

2 x 511keV

Answer 60

The size of the crystal | 3mm

Answer 61

The gamma rays hit 2 detectors at the same time

Answer 62

4x4 array of crystal elements each of dimensions 4mmx4mmx30mm They are segmented The cuts in the crystal serve to distribute scintillation light between the 4 square PMTs PMTs from all crystals

Answer 63

The interaction crystal is identified by comparing light collected by each PMT as in gamma camera Can determine which crystal event it occurred in

Answer 64

The size of the crystal | 3mm

Answer 65

The gamma rays hit 2 detectors at the same time

Answer 66

There is uncertainty in coincidences due to the resolving time (approx 1ns) A coincidence window 'gate' is set Take events that occur within a window

Answer 67

Roughly 1000s per s

Answer 68

R = 2 x S1 x S2 This occurs when 2 gates overlap by chance and these need to be accounted for

Answer 69

Most gamma photons will not leave the body Most interactions with matter are through Compton scattering Both gamma rays need to escape to register a coincidence There is increased attenuation in larger objects and it appears there is an activity reduction Thinner parts of the body would emit more radiation

Answer 70

Allows for imaging with less radiation | Combines functional and anatomical information

Answer 71

Attenuation correction using CT CT measures the attenuation factor The true count rate measured by the emission scan is divided by the attenuation factor

Answer 72

CT provides anatomical information PET provides functional information Can do attenuation correction

Answer 73

Allows for imaging with less radiation | Combines functional and anatomical information

Answer 74

- Biological hazard, uses ionising radiation - Complicated chemistry - Need CT and/or MRI (increase in expense and training) - Complex physics and inverse mathematical problems - Complex logisitcs: radiation decay and protection

Answer 75

``` Measures all photons at once Get 40x more photons Less radiation Uses short life isotopes No gaps Decrease in time ```

Answer 76

Back projection Can be filtered or unfiltered It projects backwards the data and uses an analytical approach

Answer 77

Fast = approximately 1 minute Linear Well-known

Answer 78

Low resolution | Streak artefacts

Answer 79

Neutron excess nuclides

Answer 80

Decay occurs due to an imbalance between protons and neutrons Unstable nuclides do no not necessarily exist in nature as their decay is rapid

Answer 81

Relatively slow = 10 mins Stopping criteria can be hard to determine Get salt and pepper noise

Answer 82

Neutron deficient nuclides

Answer 83

Neutron excess nuclides

Answer 84

Decay occurs due to an imbalance between protons and neutrons Unstable nuclides do no not necessarily exist in nature as their decay is rapid

Answer 85

Nuclear reactions | Cyclotrons

Answer 86

Add a proton to a stable atom | Proton goes inside the nucleus

Answer 87

14 N + 1 H --> 11 C + 4 He 7 1 6 2 15 N + 1 H --> 15 O + 1 n 7 1 8 0

Answer 88

It gives energy to protons by accelerating them This creates a proton beam which bombards the target to produce PET radionuclides Particle is confined to a circular path by a magnetic field Energy increases with each rotation High energies possible with compact design Within a vacuum chamber

Answer 89

Shielded room - expensive, easy to access for maintenance and target development Self-shielded - compact, can work nearby, cheap, but more difficult to access

Answer 90

Very expensive to run and build | Cost 1-1.5 million

Answer 91

A charged particle in a magnetic field has a circular motion | The oscillator changes the direction

Answer 92

Can be more compact than linear | Increase in rotations causes an increase in energy

Answer 93

Shielded room - expensive, easy to access for maintenance and target development Self-shielded - compact, can work nearby, cheap, but more difficult to access

Answer 94

``` Mainly beta + decay: 18F 11C 13N 15O ``` Mixed decay: 124I 64Cu

Answer 95

97% beta + | 109.6 minutes

Answer 96

99% beta + | 20.3 minutes

Answer 97

100% beta + | 9.96 minutes

Answer 98

You have to isolate the patient :( Can see longer biological pathways and process Also allows for repeat scanning from the same radiation does to see a process in stages

Answer 99

Can combine radionuclide therapy with imaging | For example if mixed alpha and beta +

Answer 100

Maximum energy a positron can have | Different nuclei have different energies

Answer 101

Decreases resolution

Answer 102

You have to isolate the patient :( Can see longer biological pathways and process Also allows for repeat scanning from the same radiation does to see a process in stages

Answer 103

- Uranium decays and creates neutrons - Reaction increases exponentially - Target of heavy elements in reactor core - Nuclei absorb THERMAL NEUTRONS and undergo FISSION - Fission products are neutron rich and decay via beta minus decay

Answer 104

131 I 99 Mo 137 Cs 133 Xe

Answer 105

It is unpredictable - it is uncertain how it will split | There are many branches and potential fission biproducts

Answer 106

- Generators serve as a source of a short lived radionuclides - Constructed on a decay-growth relationship - Product a daughter nuclide from a parent nuclide (both of which must be distinctly different) - Makes SPECT cheaper

Answer 107

82Sr -> 82Rb 68Ge -> 68Ga 62Zn -> 62Cu

Answer 108

99Mo --> decays via beta negative decay with a half life of 67 hours to --> 99mTc 99mTc --> decays via gamma decay with a half life of 6 hours to 99Tc

Answer 109

- Radiochemistry quality control - Good manufacturing practice - Manufacturing licence Meeting all regulations is expensive and hard to set up

Answer 110

Several PET nuclides can be generator produced but they are not commonly used Likely to change

Answer 111

82Sr -> 82Rb 68Ge -> 68Ga 62Zn -> 62Cu

Answer 112

Radionuclide needs to be attached to another molecule This needs to be done quickly with minimal human interaction Generate more than you need to allow for the decay Needs to be made as automatic as possible and needs to be a quick process

Answer 113

- Radiochemistry quality control - Good manufacturing practice - Manufacturing licence Meeting all regulations is expensive and hard to set up

Answer 114

Need good reproducibility of these factors: - Radiochemical purity - Chemical purity - pH - Sterility - Apyrogenicity - Very low toxicity

Answer 115

The fraction of a specific radionuclide present in the desired chemical form and in the specified molecular position

Answer 116

Incomplete reactions Side reactions Incomplete removal of protecting groups

Answer 117

- FUNCTION: a platform that meets the radiochemists requirements - SAFETY: radiation, remote processing, health and safety regulations - QUALITY: reliability, reproducibility, validation - FINANCE: funding, manufacturing costs, running costs, resources - DELIVERABLES: synthesis yield, synthesis speed, size, simplicity

Answer 118

- Large amounts of radioactivity are needed (need shielding and robotics) - Radioactive half life - Very small molar quantities - High specific activity is usually required - Very high radiochemical yield and reliability

Answer 119

Mandatory for tracers to avoid adverse reactions and pharmacological or toxic effects. Impurities result in poor quality images due to the high background in surrounding tissues

Answer 120

Ensures the products are consistently produced and controlled to the quality standards appropriate to their intended use: - Personel - Premises and equipment - Documentation - Production

Answer 121

- FUNCTION: a platform that meets the radiochemists requirements - SAFETY: radiation, remote processing, health and safety regulations - QUALITY: reliability, reproducibility, validation - FINANCE: funding, manufacturing costs, running costs, resources - DELIVERABLES: synthesis yield, synthesis speed, size, simplicity

Answer 122

- Large amounts of radioactivity are needed (need shielding and robotics) - Radioactive half life - Very small molar quantities - High specific activity is usually required - Very high radiochemical yield and reliability

Answer 123

``` Reactions take place in very small places Fully automated syntheses can be conducted Very advanced technology Used for fast FGD production 40% 18-FDG yield in 10-12 minutes - 6 mins drying - 2 minutes radiolabelling - 2 minutes purification ```

Answer 124

1. Fixed site with cyclotron and scanner 2. Tracer sent to sites with a fixed scanner and no cyclotron 3. Tracer sent to mobile scanner 4. Stand alone production facility to support mobile scanners OR fixed sites

Answer 125

Very complicated procedure to control Planes can be used to transport FDG Allows for PET scanning in remote areas

Answer 126

Measure the change of radioactivity over time to calculate kinetic parameters Transport and phosphorylation of de-oxy glucose differs only a term from glucose *. This is termed the lump constant (0.89)

Answer 127

Fluoro-deoxy glucose Deoxyglucose is an analogue of glucose with H replaced by OH Deoxyglucose is then labelled with 18F. It cannot be isomerised to fructose-6-phosphate and metabolised further and is trapped in mitochondria

Answer 128

It is trapped within the cells. This is at a rate proportional to glucolysis. Tracer amount accumulates and get a higher intensity signal.

Answer 129

Measure the change of radioactivity over time to calculate kinetic parameters Transport and phosphorylation of de-oxy glucose differs only a term from glucose *. This is termed the lump constant (0.89)

Answer 130

Static: Inject, wait, scan an area Whole body: Inject, wait, scan in sections by moving the bed Dynamic: Inject then scan in sections

Answer 131

Inject and leave for 1 hour Scan for 20 minutes This allows FDG time to accumulate

Answer 132

1-3cm variation with breathing Large discrepancy in liver and lungs Can create a strong artefact in PET (due to attenuation correction)

Answer 133

7-8 bed movements with approximately 3 minutes at each

Answer 134

Multiple passes per bed position Possible continuous bed motion Respiratory motion correction (track motion mathematically or externally)

Answer 135

- First have a scout scan to determine body position - CT at lower dose than diagnostic CT and is used for localisation. Can do full dose if you require the CT - Used for CT attenuation correction - Normally without contrast agents - Normally with shallow breathing protocols

Answer 136

1-3cm variation with breathing Large discrepancy in liver and lungs Can create a strong artefact in PET (due to attenuation correction)

Answer 137

Lean body mass Geometric body surface area Ideal body weight 18FDG body surface area

Answer 138

Multiple passes per bed position Possible continuous bed motion Respiratory motion correction (track motion mathematically or externally)

Answer 139

Standardised Uptake Value | SUV = tissue concentration (MBq/ml) / Injected dose (MBq) / Body weight in kg

Answer 140

Standardised uptake value - Standardised way of comparing different patients - Changes day to day, scan to scan, hard to tell accuracy It doesnt include an error estimate

Answer 141

Lean body mass Geometric body surface area Ideal body weight 18FDG body surface area

Answer 142

Maximum SUV value in a region

Answer 143

Average SUV in a region

Answer 144

1. Manual deliniation (variations between individuals) 2. Automatic thresholding (e.g. include all voxels 40% SUVmax) 3. 3D imaging can be time consuming to delineate SUV max is commonly used

Answer 145

Rough description of tracer kinetics Limits on testing drug efficacy Doesnt fully exploit characteristics of different tracers Semi-quantitative Only works for tracers of flux (e.g. FDG) where uptake is not too influenced by perfusion

Answer 146

Offers a more complete framework of analysiss Tracks tracer over time and use this for SUV Can do kinetic modelling to determine the chemistry of the biological process Can do volumetric chemistry over time Parametric imaging Has units - not an arbritary number

Answer 147

Need to measure radioactivity in plasma Need multiple snap shots Need to know how fast the process is (number of counts per s)

Answer 148

99m-Tc- diphosphonates Organic phosphate compounds ``` MDP = methylene diphosphonates HDP = hydroxyl-methylene diphosphonates ``` Can choose which

Answer 149

Blood flow - lesion must have blood flow Activity of osteoblasts - bone turnover Local Ca2+/PO4 2-

Answer 150

``` Suspected metastases Radiographic lesion Persistent pain with normal radiograph Acute symptoms Assessment of joint disease ```

Answer 151

IRMER ARSAC Local rules Quality control

Answer 152

99m-Tc- diphosphonates Organic phosphate compounds ``` MDP = methylene diphosphonates HDP = hydroxyl-methylene diphosphonates ``` Can choose which

Answer 153

Blood flow - lesion must have blood flow Activity of osteoblasts - bone turnover Local Ca2+/PO4 2-

Answer 154

``` Suspected metastases Radiographic lesion Persistent pain with normal radiograph Acute symptoms Assessment of joint disease ```

Answer 155

20-25 minutes in the scanner Wait 2-4 hours after injection Need to wait as a low percentage of cardiac output to the bone Allows time for tracer to collect in bones Children have active growth rates and therefore there are increased tracer at plates

Answer 156

99mTc- MAA (macroaggregated albumin) for perfusion | 99mTc- technegas for ventilation

Answer 157

Used for lung perfusion It is injected Particles 10-30um in size, blocks 0.1-0.3% of pre-capillary arteries

Answer 158

Used for lung ventilation It is inhaled Particles 0.1-0.5um in size and are deposited on bronchoalveolar cell lining

Answer 159

Suspected PE Relative lung function Suspected right to left shunts

Answer 160

When CT can't be done: Allergic to contrast Renal failure (from contrast) Pregnancy

Answer 161

``` Draw ROI over organ See how radioactivity decays in the area Plot time activity curve Done with diuretic Can determine: shape, morphology, function and split function (%R&%L) ```

Answer 162

Renal imaging Used for dynamic renal function and drainage It is cleared by tubular secretion Can see drainage and whether there is an obstruction

Answer 163

Used for static renal function | Localises to the cortex (proximal tubular cells)

Answer 164

MAG3: dilated collecting system or obstruction DMSA: relative renal function and scarring

Answer 165

``` Draw ROI over organ See how radioactivity decays in the area Plot time activity curve Done with diuretic Can determine: shape, morphology, function and split function (RvL) ```

Answer 166

99mTc-pertechnetate | 99mTc-tetrofosmin (sestamibi)

Answer 167

Cardiac image Tracer stays in blood Can be used to look for LV ejection fraction Reserved only for patients on chemotherapy that is cardiotoxic. Very producible and not user dependent

Answer 168

Tracer is taken up where there is a high concentration of mitochondria Lipophilic cation which diffuses across the cell membrane and localises in mitochondria

Answer 169

Measures myocardial perfusion at rest and at stress | Indications: IHD, function significance of known CAD, risk stratification

Answer 170

99mTc- HIDA

Answer 171

Hepatobiliary imaging It shows the formation, excretion and drainage of bile, It is a bile salt analogue and it allows you to calculate a GB ejection fraction under stress (meal)

Answer 172

Biliary dyskinesia Sphincter of Oddi dysfunction Biliary atresia or biliary leaks

Answer 173

99m-Tc labelled solid component meal | Give the patient a standard meal - need to be aware of the effect of other drugs on stomach emptying

Answer 174

Allows the study of the rate of gastric emptying

Answer 175

``` Benign = 99mTc-pertechnetate Cancer = 123I and 131I ```

Answer 176

It is trapped by the thyroid in follicular cells. It measures uptake. Indications: demonstration of functioning thyroid tissue and investigation of thyrotoxicosis

Answer 177

123I and 131I It relies on trapping and organification 123I is used for imaging 131I is used for imaging and therapy

Answer 178

Treatment - complete ablation with high dose radiation (GBq) of 131I Imaging residual disease and metastases (MBq) doses with either 123 or 131 Need to remove all thyroid cells to allow for more effective recurrance detection

Answer 179

99mTc labelled nanocolloid

Answer 180

99mTcc labelled nanocolloid is injected either intradermally or subcutaneously. Intradermal is quicker as there is a greater lymphatic network. Nuclide then cleared by lymphatic channels.

Answer 181

Sentinel node imaging in cancer | lymphoedema

Answer 182

99mTc-HMPAO - cerebral perfusion | 123I - ioflupane = dopaminergic pathways

Answer 183

Brain imaging Used to measure cerebral perfusion Need to by hydrophilic to cross the BBB

Answer 184

Cognitive impairment Dementia image - diagnosis Epilepst Stroke imaging Moving towards PET

Answer 185

123I -ioflupane (DaTSCAN) The uptake depends on selective binding to pre-synaptic dopamine receptors Indications: investigation of suspected Parkinsons (90% accurate)

Answer 186

18F-FDG | Glucose analogue labelled with positron emitting isotope

Answer 187

Brain Heart Musuloskeletal Endocrine

Answer 188

Scatter Attenuation Partial volume effects

Answer 189

15 years ago Rudimetary CT using xray tube Low quality CT - used for localisation not characterisation

Answer 190

Latest multidetector CT technology - diagnostic CT, 64 detector rows Allows for more accurate localisation and characterisation Advanced gamma camera and CT = facilitates low dose imaging and faster data acquisition Iterative reconstruction (lower dose or speed up) Mulit-modality work station and additional PACS software required

Answer 191

1. Providing more accurate localisation 2. Detecting additional lesions 3. Excluding physiological tracer uptake 4. Charactering equivocal anatomical lesions 5. Providing reliable CT based attenuation correction 6. Facilitating one stop shop imaging 7. Reducing the need for multi-layered testing

Answer 192

Increase specificity = increased localisation Increased sensitivity = increased lesions detected The increase in specificity is greater than sensitivity

Answer 193

``` Bone imaging Neuroendocrine tumour imaging Parathyroid imaging Thyroid imaging Hepatobiliary imaging RBC imaging Infection/inflammation imaging ```

Answer 194

``` SPECT = approx 10 mins CT = seconds ```

Answer 195

Initial phase = tracer is in the blood and it is mainly used for looking at soft tissue uptake e.g. hyperaemia

Answer 196

Scans at an initial and delayed phase - common in bone scans.

Answer 197

No clear guidance. After X ray, MR recommended but there are problems with availability If a bone scan is negative - 99% confident no fracture It can miss if done in elderly or within 24 hours

Answer 198

When it affects the axial skeleton or proximal long bones as plain X-ray is poor here It is also good for pathology of the ankle When there is metal work (new CT have minimal artefacts)

Answer 199

Diverse group of rare neoplasms accounting for 2% of all cancers.

Answer 200

1. Neural crest origin - phaechromocytoma, paraganglionoma, neuroblastoma 2. Meduallry thyroid cancer (MTC) - rare and complex to image 3. Gastroenteropancreatic (GEP) tumours - carcinoid and endocrine pancreatic tumours (EPTs) they are hormonally active and hard to diagnose

Answer 201

They express somatostatin receptors (SSR) subtypes 2 and 5 Imaged with SSR analogues e.g. 111-Indium labelled pentreotide (octreoscan) Must use SPECT/CT Neural crest tumours are imaged with guanethidine analogues e.g. 123Iodine-mIBG

Answer 202

Done after resection and ablation Allows more effective monitoring of thyroiglobulin 131-I kills all thyroid cells Image 3 days after administration due to very high radiation levels Can pick up any metastases

Answer 203

99mTc- sestamibi

Answer 204

Used for primary parathyroid cancers Allows for more specific localisation of adenoma to have minimally invasive surgery Parathyroid holds onto radiation longer than thyroid which washes out

Answer 205

It is the first draining node of an area - well esablished in breast cancer and adenoma - prevents resecting multiple lymph nodes - prevents long term morbidity

Answer 206

Label the patients own WBCs and inject back into the patient | Useful in infection and inflammation

Answer 207

Used for GI blood loss Can find source of bleeding Can find smaller bleeding rates than CT angiography (High uptake in spleen due to sequestering)

Answer 208

- Can acquire diagnostic level CT - If not required can have low dose CT - Non-contrast - Shallow breathing protocol

Answer 209

- Number of bed positions (7-8) - Time per bed position (2-5 mins) - Movement artefact (increases with scan time) - Dual time point - Decrease dose and increase scan time or VV

Answer 210

18F 11C 13N 15O

Answer 211

Different tracers for different purposes Location of cyclotron limits what procedures you can do Most produced in cyclotron Short half life Measures physiological processes e.g. glucose metabolism, blood flow, hypoxia, proliferation etc

Answer 212

FDG - most cancers demonstrate an increased glucose uptake | Cancers upregulate GLUT1 receptors

Answer 213

Most cancers demonstrate an increased glucose uptake Cancers upregulate GLUT1 receptors

Answer 214

Administer tracer (positron emitting) Positron annihilates with electron This produces 2x511keV gamma photons Use coindence to detect locations

Answer 215

It competes with glucose for transport and into cancer cells | It becomes phosphorylated and trapped within the mitochondria

Answer 216

- Combines functional and anatomical info - More accurate localisation - Better detection - Increased sensitivity and specificity - has significant impact on patient management - Able to see disease not on normal CT - Fused data sets increase correct imaging reading

Answer 217

``` Lung Colorectal Lymphoma Head and Neck Oesophageal ```

Answer 218

Aim to have 1 PET/CT scanner per 1.5 million population Funded by the department of health National program Spread throughout country

Answer 219

``` PET/CT = = £1000 CT = £150 ```

Answer 220

``` 47% lung 16% lymphoma 10% oesophagus 8% colorectal 6% head and neck ```

Answer 221

``` Lung Lymphoma Head and Neck Oesophagus Colorectal Melanoma Breast Thyroid Cervical Heptaobiliary Unknown primary malignancy ```

Answer 222

Neuroendocrine tumours Brain tumours Bone and soft tissue sarcomas

Answer 223

1. Characterisation 2. Staging 3. Re-staging 4. Response assessment 5. Recurrence detection 6. Radiotherapy planning 7. One stop shop imaging

Answer 224

It is determining the nature of lesions detected on imaging | hard to tell if a mass is malignant or benign without pet/ct

Answer 225

It is determinig the extent of disease PET/CT increases the sensitivity and specificity Can guide appropriate treatment Can change the risk profile of nodules/findings Can detect multiple sites which a CT can miss

Answer 226

Determining the extent of disease (again) after treatment to determine efficacy Can pick up sites miseed on ct lymphoma not normally seen on ct

Answer 227

Checks if a treatment has worked and this is a rapidly growing area Guides treatment decisions - tailored therapy - Can change therapy, stop chemo, track effectiveness, change midway if prognosis poor PET/CT FDG shows changes before anatomical changes Can predict overall response and disease free survival Can determine end of treatment response: Can't tell residual disease vs fibrosis with just ct

Answer 228

Differentiating fibrosis from recurring disease Can tell with multiple CT scans over time but not with just one CT. Adds metabolic activity Can pick up occult disease missed on anatomical imaging

Answer 229

It allows for a more targeted therapy - to get higher doses to smaller areas ``` Outline the:: GTV - gross tumour volume CTV - clinical target volume PTV - planning target volume TV - treated volume IV - irradiated volume ``` Increases accuracy. It decreases toxicity by decreasing the area

Answer 230

Infections Inflammation Cardiology Neurology

Answer 231

Oncology (choline) Cardiology (rubidium) Neurology (amyloid plaques)

Answer 232

Waste product of FDG Marker of osteoblastic activty Good for imaging bone mets PET has better resolution than SPECT

Answer 233

Marker of membrane synthesis Useful in prostate cancer Prostate is not very metabolically active so has limited glucose uptake - can be picked up with choline Can also be used for occult node involvement and bone mets Can image the process you are targeting

Answer 234

68Ga-DOTA-ocreotate Used in neuroendocrine tumour receptor imaging Can use 111 Indium octeotide

Answer 235

FDG uptake is non-specific and is increased in infection and inflammation - can't distinguish from cancer Needs confirming with tissue samples - Can measure baseline and treatment response - Can be used to image large vessel vasculitis as this can't be seen on CT - Can be used to find pyrexia of unknown origin e.g. aortic graft rejection - Can be used for sarcoidosis (uncommon as benign)

Answer 236

Oxygen - research nitrogen - research rubidium FDG

Answer 237

Myocardial perfusion and myocardial viability PET perfusion = rubidium SPECT perfusion = 99mTc PET viability = FDG

Answer 238

FDG - Epilepsy - hypometabolism - Dementia - Neuro-oncology Non FDG - amyloid plaque imaging in Alzheimers

Answer 239

Image if the causes is unknown Assessed metabolic activity in the brain - hypometabolism Aims to detect patients early e.g. pre-symptomatic and use therapies to delay onset Can pick amyloid deposition Can pick up whether they are 11C - PIB positive or negative. 82% of those who are positive go on to get Alzheimers Amyvid can assess amyloid plaques but it very expensive

Answer 240

``` MRI doesnt give density map MR needs attenuation correction Scan times are longer Decreased quality of MR to shorten time Can have artefacts in mR very expensive ```

Answer 241

``` Paediatrics Oncology Gynae imaging Multiparametric assessment Neurology Cardiology ```

Answer 242

Measuring/locating a molecular process or gene expression It does not image anatomy or structure it does not image function processes like perfusion

Answer 243

PET | Optical

Answer 244

Used in preclinical research and detects light rather than gamma rays Useful for molecular imaging

Answer 245

``` beta + beta - alpha gamma X-ray ```

Answer 246

Beta + (positron) | 2 gamma rays

Answer 247

beta minus and alpha

Answer 248

1. Tracer quantities are pico or nano molar (much lower than CT and MR) 2. Should not ellicit physiological response 3. Low risk of toxicity 4. Radiation risks should be calcuable (radiation purely from tracer) 5. Rapidly translated to clinical studyy 6. Quantitative 7. Non- invasive 8. Whole body 9. Molecular rather than anatomical

Answer 249

Pet has better resolution (5-10mm) Pet has better sensitivity Pet has better quantification of images Uses lower levels of radiation as it does not need to over Collimators

Answer 250

Spect is cheaper It is more widely available Multitracer imaging is possible Improving performance imaging

Answer 251

It turns toxicity to your advantage. It is the selective delivery of radiation to the tumour using the same principles as imaging Uses beta or alpha emission Low penetration and therefore create a high local dose and kills the cells

Answer 252

Thyroid cancer 131- I Bone metastasis 188-Re or 153-Sm or 233-radium (alpha) Lymphoma Neuroblastoma

Answer 253

1. Find a molecular target 2. Consider chemistry - attach radionuclide to particle 3. Consider molecular biology/cell biology 4. Small animal models 5. Imaging 6. Computer modelling 7. Clinical imaging Repeat 1-6 until suitable for clinical

Answer 254

Sodium iodide symporter (iodine or pertechnetate) Tumour specific antigen Neuropeptide receptor (somatostatin or calcitonin) Glucose transporter (FDG) Amino acid transporter (f18 tyrosine) Angiogenesis (rgd peptides) Transferrin receptor (Ga 67)

Answer 255

``` Clinical diagnosis and decision making Location and detection of disease Molecular characterisation of disease Bio markers to predict or measure therapy outcome Drug development tool Basic biomedical research Therapy ```

Answer 256

Tissue penetration is greater than light Increased sensitivity Risk generally very small - risk of not scanning greater

Answer 257

``` Increased radiation dose Cost of radioisotopes and technology Development is expensive Avoid in children and pregnant women Needs to be avoided if unnecessary ```

Answer 258

Human sodium iodine symporter hNIS is imaged It is essential for thyroid function (production of thyroid hormone) and is over active or under active in some cancers Useful for staging and shows loss of thyroid and any metastatic spread

Answer 259

Thyroid Stomach Mammary glands

Answer 260

``` 123 I iodide. Spect 131 I iodide. Therapy 124 I iodide. Pet Perchlorate (competitive inhibitor) 99m Tc pertechnetate. Spect F18 tetrafluoroborate. Pet ```

Answer 261

They all have a single negative charge Very similar size Body can't differentiate molecules I-, At-, TcO4-, BF4-

Answer 262

High metabolism and replication Low oxygen Anaerobic metabolism Increased glucose consumption

Answer 263

Increased glycolysis requires increased glucose Glut1 expression is increased Glut1 is translocated to cell membrane Hexokinase is increased

Answer 264

It is an analogue of glucose and is a substrate for glut1 and hexokinase It enters the cell and is phosphorylated by hexokinase to FDG-6P It cannot be broken down further and is trapped with in the cell

Answer 265

It is a hormone that regulates the endocrine system and is involved in neuro transmission and cell proliferation It is switched on in neuroendocrine tumours and is not strongly expressed in adults Target for therapy and imaging

Answer 266

Using 68Ga octreotide - it has the same binding area as somatostatin. Somatostatin is very unstable and breaks down rapidly. Octreotide has a DOTA chelate which makes it more stable. It is broken down slower

Answer 267

It is an oxygen deficiency that causes changes in cell biology. These changes can be detected using molecular imaging. Hypoxia cells have increased free electrons and this breaks down the molecule. This causes an accumulation of copper/radionuclide in the cell and causes the copper to dissociate from the molecule

Answer 268

Hypoxia can cause resistance to radiotherapy and chemotherapy. It is also an indicator that a tumour is more aggressive. It can also be used in IHD and stroke

Answer 269

Cu-ATAM | 18F-FMISO

Answer 270

99m Tc HL91

Answer 271

``` It is the formation of new blood vessels and is associated with: Tumour growth Wound healing Tissue remodelling Inflammation ```

Answer 272

It is when cancer cells are transported by the circulatory system to distant sites. It requires angiogenesis. Cancerous tumour cells release molecules that send signals to surrounding tissue and this activates certain genes that encourage blood vessel growth.

Answer 273

Vasculogenesis - creates the primary network of vascular endothelial cells that will become the major blood vessels Angiogenesis - remodels the network into the new small vessels that complete the system

Answer 274

Menstrual cycle | Necessary for repair and regeneration of tissue during would healing

Answer 275

Inhibitors are high | Activators are low

Answer 276

Inhibitors low | Activators high

Answer 277

Integrins alphav beta3 - they are present on the surface of endothelial cells. They bind matrix macromolecules and proteinase a VEGF- affects permeability Ang 1 and ang 2 - stabilises the vessels Plasminogen activators

Answer 278

18F-galacto-RGD Binds to avb3 integrins Very high in angiogenic tumours - sign of an aggressive tumour

Answer 279

Cells have machinery to export potentially toxic substances Example: MDR1 gene product, this is found in bbb, liver and tumour cells. This is a problem for chemotherapy Increased expression of MDR1 can lead to increasing amount of drugs being exported out of the cell

Answer 280

It recognises a wide range of molecules, especially lipophilic cations. It is located in the cell membrane and the presence can be induced by hypoxia and chemotherapy. It captures the drug inside the cell and transports it out Imaging this can be used to measure quantity and make decisions about chemotherapy

Answer 281

Label with 99mTc or 64Cu Measure uptake - it is trapped in mitochondria Then measure clearance - clearance is faster with PgP, this requires dynamic sampling Can repeat the scan after injection of a PgP inhibitor to check (verapamil)

Answer 282

It transports iron in the blood to deliver it to cells

Answer 283

Ga3+ binds to transferrin and it mimics iron due to its similar size and charge. Inject 67 or 68 Ga and it binds to transferrin and receptors

Answer 284

Transferrin receptors are over expressed in lymphoma and prostate cancer. The Ga is internalised and it shows cells with increased iron requirement Increased fe in melanoma

Answer 285

It is where lactoferrin is present: milk, saliva, tears and nasal secretions. Also high in liver as this is where radio metals are metabolised

Answer 286

15O 13N 11C 18F

Answer 287

64Cu 86Y 89Zr 94mTc

Answer 288

12.7 hours

Answer 289

14.7 hours

Answer 290

``` Long half life (days-hours) Produced via cyclotron or generator Have redox chemistry Bio metal mimics Label large molecules, not small ```

Answer 291

``` Short half life (mins to hours) Produced in cyclotron No redox chemistry Label small molecules Can label large molecules but they have very short half life ```

Answer 292

Metallic elements have a very rich redox chemistry This is the addition or removal of electrons They have several states available

Answer 293

Advantage: used in hypoxia imaging using copper Disadvantages: problems with stability

Answer 294

- Higher energy particle bombardment, but several are still in the cyclotron range - labelling is simpler but the processing is more complex - inorganic - it is not easily used with small organic molecules and the uses reflect this - needs a chelator to increase stability

Answer 295

``` Peptides Antibodies Nano particles Processes that needs a long half life Biological and radiological half life need to be matched ```

Answer 296

It can be used to look at where the metal goes normally

Answer 297

When 1 ligand is bound it increases the probability of the 2nd and 3rd binding etc. this increases the stability constant It requires specific geometry and needs to be designed

Answer 298

It is not a one way reaction It is in equilibrium Increasing the stability constant decreases the likelihood of being broken down

Answer 299

It causes a significant modification of molecule Increases the size If it was a small molecule the change will be significant and it will no longer behave as the original If the molecule is large e.g. Antibodies, the change is insignificant

Answer 300

1. Half life needs to be matched to biological half life 2. Chelator is required to increase stability (need to be specifically designed) 3. Emission properties - beta plus range, beta plus emission dose 4. Effect of labelling and or chelating - on bio distribution or pharmokinetics 5. Specific activity - increased specific activity is increased radioactivity per gram

Answer 301

``` Mimicking bio metals 82Rb mimics K+ (myocardial imaging) 52Fe to see iron metabolism 64Cu to see Copper metabolism 83Sr to see bone metabolism (calcium analogue) ```

Answer 302

Rubidium 82 is injected as an atom It is produced from a Sr generator (half life of 25 days) It is used in myocardial perfusion and it identifies regions of poor blood flow Half life -76s It is a potassium analogue and can be used to image Na/K pump

Answer 303

It uses oxidation and reduction states of copper Half life - 13hours Small cation +1 or 2

Answer 304

``` Used for SSR imaging Hard small cation +3 charge Similar to iron No redox Binding to Ligands is weak ```

Answer 305

Change the shape and stop working Hard to design Expensive to develop Can involve heating which can damage the molecule e.g. Antibodies

Answer 306

``` Long half life 78hours Suitable for imaging antibodies Zr 4+ Binds readily to oxygen It is very selective Binds to prostate cancers ```

Answer 307

Beta emitters with a long half life can be delivered to the area Drug loaded nano particles can deliver chemo drugs to a specific area via receptors If beta and gamma can image and treat at the same time

Answer 308

Generator availability Longer half life for transportation Longer half life to image longer biological processes Specific metabolic and chemical properties Linked with therapeutic analogues

Answer 309

Non invasive Real time In living tissues and cells Allows you to study in the natural environment

Answer 310

It is transferable to humans | Saves a lot of lives

Answer 311

1. Select biochemical process 2. Find a molecular target 3. Choose imaging modality 4. Chemistry 5. Labelling 6. Molecular/cell biology 7. Small Animal models 8. Large animal models 9. Imaging 10. Computer modelling 11. Clinical imaging

Answer 312

``` Spatial resolution Sensitivity Whether it is dynamic Whole body or region Temporal resolution required Penetration depth Quantitative Can repeat studies be done Is it clinically relevant ```

Answer 313

``` Excellent spatial resolution Poor sensitivity Not dynamic Whole body or region Ok temporal resolution Limitless depth of penetration Quantitative Can repeat but dose High clinical relevance ```

Answer 314

``` Excellent spatial resolution Very poor sensitivity Not dynamic Whole body or region Poor temporal resolution Limitless depth of penetration Semi quantitative Can repeat High clinical relevance ```

Answer 315

``` Lowest spatial resolution Highest sensitivity Dynamic Whole body or region Very good temporal resolution Limitless depth of penetration Fully quantitative Repeats but dose High clinical relevance ```

Answer 316

``` Low spatial resolution Good sensitivity Dynamic Whole body and region Very good temporal resolution Limitless depth of penetration Quantitative Repeat but dose High clinical relevance ```

Answer 317

MDT Radiochemist, chemist, molecular biologist, geneticist, cell biologist, immunologist, animal model expert, medical physicist, clinician

Answer 318

Between 12 weeks and 3 years

Answer 319

``` Target or ligand discovery DNA cloning Expression system Protein production Imaging agent development In vitriol studies Preclinical imaging ```

Answer 320

Faster More expensive so not used preclinically Image quality limited due to noise HU less accurate

Answer 321

``` Offset Gain Bad pixel Geometrical calibration HU Beam hardening ```

Answer 322

Uses pin hole Collimator | Increase resolution

Answer 323

``` It either magnifies or shrinks the image It flips the image upside down Has much smaller field of view 6x the resolution Better sensitivity ```

Answer 324

Intrinsic - noise in pmt signal, spread of energy deposition in detector due to scattering Acceptance angle In which incident photons are accepted Septal penetration Septal scatter

Answer 325

``` Crystal pitch Positron range Ring diameter Location of source Optical encoding error ```

Answer 326

Increase pitch = decrease resolution

Answer 327

Decrease pixel pitch | Use computer correction for positron range

Answer 328

Increase resolution Increase inter crystal error Increase cost

Answer 329

It is when organs of different sizes appear different with the same activity concentration. Smaller objects look colder

Answer 330

Increase length of crystals Increased the solid angle Increase detector surface

Answer 331

Very expensive Very recent due to production of mr compatible detectors Currently sequential, mr then pet or vv

Answer 332

Pet has decreased resolution than spect | Pet has increased sensitivity than spect

Answer 333

``` Angiogenesis Hypoxia Proliferation Tumour metabolism Apoptosis Metastasis ```

Answer 334

FDG uptake in seizures | Dopamine system

Answer 335

``` Need new imaging agents Biomarker discovery Production is not very efficient Technology Communication between different fields Clinical translation Sensitivity Practical aspects ```

Answer 336

Increased magnification Increase sensitivity Increased resolution

Answer 337

Pet mr | Spect mr

Answer 338

Pet mr due to soft tissue and sensitivity Can do pet ct with contrast Spect

Answer 339

Combine gamma with beta Beta is highly energetic and is absorbed by tissue and damages DNA Can track therapy with gamma and measure response Use Lut177 16% gamma 84% beta Can predict outcome to treatment and indicate level of response

Answer 340

Images physiological function e.g. Glucose metabolism Spatial resolution 4-15mm Physiology nor always correlated with anatomy More specific but not useful without anatomy

Answer 341

Images anatomical properties e.g. Attenuation or t1/t2 times Spatial resolution is around 1mm Can take a long time to detect anatomical changes

Answer 342

Type of emission - is it a pure photon emission Energy of emitted photons - 100-200keV Half life - allows Imaging and chemistry to take place. Needs to be long enough to view the process but as short as possible to reduce dose Production - cyclotron or generator

Answer 343

``` 99mTc --> gamma + 99Tc 6hour half life Produced from 99Mo Gamma are 140keV It is reactor produced Can be kept in the hospital and alluded when needed Only gamma, no therapeutic doses ```

Answer 344

201Tl --> gamma + 210Hg Cyclotron produced K analogue so can see sodium potassium pump Gamma emission is 167keV and 135 keV Most are X-ray rang 69-80kev from 210Hg Images are noisier as you have to use less dose

Answer 345

``` Have to use less dose so less units of activity Decreased quality image Needs increasing smoothing Increased blurring Decreased contrast ```

Answer 346

Restrict the direction of photons 1% Can be less depends on Collimators

Answer 347

The position is calculated by the weighted position of each pmt based on the amount of light detected Anger logic - uses the coordinates of the centre of each pmt x amount of light at each / total light

Answer 348

Closely packed to increase effectiveness at collecting light | Some use hexagonal pmts to increase coverage of the NaI(Tl) crystal

Answer 349

Reads z pulses to determine the energy of each gamma ray If photons are scattered they lose energy Don't want to include as they provide false information Use a narrow energy window, usually 20% centred at the peak 99mTc 126-154keV

Answer 350

It is done by applying an inverse image to all subsequent images

Answer 351

6-7mm better in preclinical | Depends on the type of collimator

Answer 352

Image is the same size as object Fov is independent of the distance from the face of the collimator Count rate is independent of the distance from the face of collimator

Answer 353

Low energy

Answer 354

Thick septa to stop high energy photons Increased hole diameter Used for iodine

Answer 355

Increases dispersion and decreases resolution

Answer 356

NaI(TI) crystal Detects individual rays by gamma scintillation Converts to light Thickness is 9.5mm or 12.7mm

Answer 357

99mTc is done for perfusion Inhaled gas is used for ventilation Normally done with ct not possible e.g. Pregnancy or allergic to contrast agent

Answer 358

A window or ramp opens up along the camera face and scans down the body slowly. It ramps down as the camera reaches the end of the body Sensors ensure it stays close to the patient

Answer 359

``` Inject radio pharmaceutical Want to know how fast it arrives and is cleared Plot time activity curve in ROI Can quantify degree of abnormality Scan at repeated periods ```

Answer 360

Using ventricular ejection fraction Ef = edv-esv / edv Can measure regional wall motion to check for abnormalities Can label RBCs or track the wall edge

Answer 361

Spatial is 8-16mm Temporal 2-10mins Sensitivity 0.15%

Answer 362

Spatial resolution 3-8mm Temporal sec-min Sensitivity 0.5-5%

Answer 363

Rotates the gamma camera around to get multiple projections | Sums all data into a matrix -SINOGRAM

Answer 364

Easier for calculation and slice reconstruction Can use FBP or iterative reconstruction Can reorient set to get a standard view

Answer 365

Image registration - minimise the distance between landmarks on the 2 images If the patient moves it alters alignment Can use cross correlation, mutual information, landmarks and similarity criteria In pet,ct or spect,ct the centroid displacement between the 2 is calculated and applied to all subsequent images

Answer 366

Different depths have different levels of attenuation If there is no correction then the internal or thicker areas has lower uptake due to increased absorption. Values are underestimated at the centre. Ct allows you to correct this

Answer 367

Image segmentation Bilinear scaling Hybrid scaling

Answer 368

The HU image is segmented into regions and pixel values are replaced with the expected values for 511keV mu for the region

Answer 369

A scaling factor is applied to all hu values to convert to u values at 511 There are 2 separate scaling factors -1000 to 0 Hu greater than 0

Answer 370

Apply a scaling factor to HU to get u 511. | 2 separate scales, one for soft tissue and one for bone

Answer 371

Spatial resolution in ct must be adjusted to that of pet Must use iterative reconstruction

Answer 372

It can take a long time Need to optimise the number of iterations to the application Increasing iterations increases noise - however it also creates a uniform resolution Safest to over iterate and smooth

Answer 373

Solid state detectors Get the energy of the incident photon You know the angle of incidence Can potentially reconstruct using advanced mathematics

Answer 374

New design in cardiology Small multiple gamma camera can rotate and align with the ROI Increases scan time over ROI and increases sensitivity Also decreases resolution due to the wide collimation You know the percentage decrease in resolution so can correct

Answer 375

Decrease resolution | Increase sensitivity

Answer 376

It is the mathematical calculation that aims to correct for a decrease in resolution due to using wide collimators It takes into account specific performance characteristics like knowledge of system and user control

Answer 377

``` 131 I (NaI) for thyroid 131 I mIBG for neuroblastoma 177Lu-DOTA for neuroendocrine tumours 90Y-DOTA for neuroendocrine tumours 90Sr for bone mets ```

Answer 378

``` Nurses Clinicians Radio pharmacy Physicists Technicians ```

Answer 379

pRRT | Somatostatin receptors are targeted by peptides e.g. 111 In DTPA octreotide to deliver harmful radioactivity to the area

Answer 380

Perspex as you want to minimise the production of secondary X-rays

Answer 381

Range in air is many metres Can transverse the body Relative harmfulness 1

Answer 382

Range in air is 10s of cm Range in tissue is mm Relative harmfulness is 1

Answer 383

Range in air is many m Can transverse the body Relative harmfulness is 5-10

Answer 384

Range in air is cm Range in tissue is less than 1mm Relative harmfulness 20

Answer 385

Energy absorbed per unit mass | Gy

Answer 386

Absorbed dose X factors for radiation type and tissue sensitivity Sv

Answer 387

Measure do how quickly you are receiving radiation dose | mSvh-1

Answer 388

Can have no effect, kill cell or damage the cell and it can be incorrectly repaired Stochastic is long term Deterministic is short term

Answer 389

Skin damage Radiation sickness Decreased fertility Death

Answer 390

Fatal cancer risk of 1 in 20,000

Answer 391

Justification - exposure to ionising radiation should only occur to produce a net benefit Optimisation - dose, the number of people and the likelihood of exposure should be kept ALARP

Answer 392

As low as reasonably practicable

Answer 393

Should be reduced to acceptable levels Employee is 20mSv per year Trainees 6, general public 1 1mSv to the foetus during the declared term of pregnancy

Answer 394

Chest X-ray 0.02mSv | Nuclear bone scan 3mSv

Answer 395

Must be kept secure Any losses to be reported to police, health and safety executive and the environment agency Damage should be checked using leak tests

Answer 396

X-ray sets Linear accelerates Sealed and unsealed sources

Answer 397

Unsealed sources

Answer 398

Time Distance (inverse square law) Shielding

Answer 399

SPECT has lower energy SPECT has lower TVL and HVL Spect has a lower dose rate

Answer 400

Controlled area Enclosed prep cabinet Shielding for generator and eluted cavity Washing, changing and monitoring facilities

Answer 401

``` Shielded container to carry the syringe Syringe shield Spill tray with absorbent material Control of waste materials Room may be a controlled area ```

Answer 402

Containment Prevent ingestion Decontamination Procedures and monitoring

Answer 403

According to local rules Use decontamination kit Isolate, decontaminate, report

Answer 404

Ionising radiation regulations 1999 Ionising radiation (medical exposures) regulations 2000 Medicines (administration of radioactive substances) regulations 1978

Answer 405

``` Ionising radiation regulations 1999 Protection of workers and public Enforced by health and safety executive Controlled and supervised areas Radiation protection advisor Radiation protection supervisor Local rules Personal dosimeter Instructions and training ```

Answer 406

Protection of patients Justifying medical exposures Optimising medical exposures Adequately trained staff

Answer 407

System to maintain and verify expected performance It compares performance with other scans using standardised tests It characterises any deterioration in performance

Answer 408

Specific aspects of quality assurance e.g. Equipment tests

Answer 409

``` Spatial resolution Spatial linearity Uniformity Count rate capability System sensitivity Energy resolution Whole body scanning performance Multiple window spatial registration ``` Shield leakage - only at acceptance

Answer 410

Parameter which characterises the amount of positional distortion caused by the camera with respect to incident gamma events entering the detector A line source will appear wavy without correction due to positioning of PMTs

Answer 411

Measure the repsonse of the camera to a homogeneous flux of radiation WITHOUT collimator Point source 5 x FOV away

Answer 412

Sheet source (57Co) 122keV throug a collimator Measure the ability of the overall system to respond correctly to a homogenous flux of radiation

Answer 413

Max pixel - min pixel / (max pixel + min pixel) x100 For whole image

Answer 414

For all groups of 5 adjacent pixels | Max pixel - min pixel/ max pixel + min pixel x100

Answer 415

Acquire enough counts per pixel to allow the system non-uniformities to be seen as distinct from Poisson noise - around 10000 counts per pixel

Answer 416

Phantom with lines is place on top of sheet source - if straight then correction is working qualitiative also gives you an idea of spatial resoltion

Answer 417

The optical coupling between the crystal and the PMT If poor - regrease USE A POINT SOURCE

Answer 418

Most are made of lead | Can be tungsten - better performance but more expensive

Answer 419

Integral is max and min pixel from anywhere in the image | Differential, they must be within 5 pixel of each other

Answer 420

In spect any errors are magnified in the reconstruction process

Answer 421

Jaszczak phantom Industry standard for SPECT testing It assessed uniformity and spatial resolution Tank of Tc with cold object within e.g. spheres, parallel rods of varying sizes and pitch

Answer 422

The computer assumes that the gamma camera will rotate in a smooth manner around the postition Computer must know where the cameras are in order to reconstruct

Answer 423

Place a point source in the centre and it should execute a sinusoidal pattern

Answer 424

Acceptance and annually - NEMA tests *count rate performance, image quality, spatial resolution and sensitivty) Daily - CT warm up, air calibration, SUV check (PET) Weekly - PET/CT alignment Quarterly SUV calibration and check

Answer 425

Expose PET crystal to positron emitting point source Check uniformity and energy peaking/resolution and coincident timing SUV check

Answer 426

test using a uniform cylinder containing known activity and mass Calculate SUV daily to monitor Check fit for use

Answer 427

Appropriate emission to the modality Known decay method and activity and mass Long half life so don't have to replace often

Answer 428

SUV = activity concentration from the image / (injection activity/patient body mass)

Answer 429

``` Weekly CT moves so could get misregistered Use phantom with some attenuation characteristic of tissue with 5 radioactive sealed sources on them. metallic encapsulation so show up on CT Check they overlap ```

Answer 430

Check calibration is right need to check dose calibrator corresponds correctly to the dose seen by the camera Update and check correction factors

Answer 431

``` Sensitivty Spatial resolution Image quality Count rate performance Accuracy of cont loss corrections ```

Answer 432

Mean cps/kBq from an un-attenuated line source at the centre of FOV and offset 10cm. Low activity count so count losses are insignificant Sensitivty decreases linearly as you move out of the centre

Answer 433

Small sources infiedl of view and determine how big they look NEMA: 1 source 1cm off axis and 2x10cm off axis Line sources - look at line spread function - measure FWHM If it is wide will decrease quality of the image

Answer 434

6 coplanar spheres - hot background. they are fillable. - Some hotter than background - Some colder (no activity) Check attenuation correction by filling one with sample representing lung tissue - challenge attenuation correction Put object with activity around it to represent the body to challenge the scatter correction Can measure contrast, variability and whether they appear to have same concentration

Answer 435

It has double the distance to go | Therefore increases attenuation

Answer 436

Fill line source with high activity (GBq) Line source scanned in centre All profiles should be summed to get integrated counts for sinogram Any events outside width of line = scatter True count rate (remove scatter and random) = assume linear interpolation from outside the line.

Answer 437

From testing: Get scatter and random counts Get total counts Get system measures of random counts Calculate scatter fraction and noise equivalent count rate

Answer 438

A measure of the liely effect of scatter on images Counts from random+scatter - random counts / (total counts - random counts)

Answer 439

A global measure of the likely image SNR NECR = (total counts - counts from scatter and random)^2 / total counts

Answer 440

Net error is computed which expresses the error in count rate after the corrections are applied

Answer 441

Bismuth germanate

Answer 442

``` Hyperparathyroidism (sestamibi) Infection/inflammation (white cells) Bleeding studies (red blood cell) Hepatobiliary (hida) Neuroendocrine tumours (octreotide) Thyroid cancer (iodine) ```

Answer 443

It is produced from 99mo which is primarily obtained from nuclear reactors

Answer 444

as the number of nuclear generators reduces globally there will be limited access and high price of 99mTc, therefore cost of scanning is expected to increase significantly

Answer 445

Defined as the rate of molecular exchange from one compartment to another

Answer 446

Simple and versatile Suitable for clinical use Useful for diagnosis, staging and therapy

Answer 447

Only works for tracers of flux Limited efficacy of drug testing Semi quantitative Rough description of tracer kinetics Doesn't exploit the characteristics of different tracers SUV use has to be alway a priori validated

Answer 448

Positron emission Positron travelling /scattering with range mm Collide with electron Annihilation producing 2x511keV gamma rays in opposite directions Travels through body, some will be attenuated via Compton scatter, some will leave the body. Those that leave the body will hit the scintillator crystal This produces an optical photon from the gamma This passes into pmt where signal is amplified and produces an electrical signal Then calculate position based on light and coincidences

Answer 449

Can be combined with Ct to combine anatomical and functional data FDG is oncology to stage cancer Novel indications (treatment assessment ) Better access to tracers (now cyclotron and generator) Cost reduction

Answer 450

``` Cost is expensive Development of new tools are expensive New tracers are slow and expensive to develop Lag in patient referrals Complexity of reporting Logistics Current economic climate ```

Answer 451

FDG is phosphorylated and the product is trapped in the cell at a rate proportional to glycolysis. The glucose is not trapped and moves through the cycle

Answer 452

Combines functional and anatomical Can correct for attenuation problems in nuclear imaging Provides more accurate localisation of lesions Detects additional lesion Assists in the exclusion of physiological tracer uptake thereby improving accuracy of image interpretation Better identification of inflammatory lesions Reduce time imaging by combining

Answer 453

Longer scanning time Increased radiation dose Increased cost of development and production Increase cost per scan Artefacts which affects images if there is misalignment or incorrect attenuation provided Increased staff training Increased quality control requirements

Answer 454

Oncology cancer

Answer 455

Cell membrane proliferation FLT - imaging Biomarker do cell proliferation FCH- choline. Imaging Biomarker of malignancy induced over expression of choline kinase

Answer 456

Prostate cancer Has low glucose metabolism/requirement but high cell proliferation (f-choline) FLT: brain tumour. FDG has a high uptake in the brain and cancer can't be easily distinguished from normal. FLT does not have high uptake in the brain as standard

Answer 457

``` Parent free Sterile Easy to use High yield of daughter nuclide Compact Daughter decays to stable nuclide Parent free ```

Answer 458

Saline (NaCl) is washed through to obtain 99mTc This runs through an exchange column The molybdenum decays and it attached to alumina. 99TcO4- binds with sodium to give 99m Tc o4na (pertechnetate) which can then be eluted

Radionuclide Imaging Flashcards

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