Unit 1 - Screening and Imaging

Question 1

Why is it that non-melanoma skin cancers are often not included in cancer incidence and survival data?

Answer 1

This is because NMSC is the most common cause of the disease, accounting for around 20% of cases, yet the survival rates are incredibly high, usually, as the disease is detected early as tumours are often visible and subsequently it is responsible for a relatively low number of all cancer deaths (around 1%).

Question 2

Discuss the way in which direct tumour cells can spread, using examples of different cancers, may cause issues for patients?

Answer 2

Direct spread, this is common in NMSC’s where there is no barrier to stop the tumour growing like bone or cartilage. This can generally be treated by either surgery or radiotherapy – however this ordeal way mean the patient suffers from anxiety, due to diagnosis or potentially that he may suffer from the disease again in the future or they may deal with self-confidence issues if the radiotherapy/Mohs Micrographic surgery leaves any potential damage to surrounding normal tissue – particularly if this is a visible area like the face.
Breast cancers also primarily spread directly before any lymphatic or haematological spread – these tumours can often become ulcerated as it will block the flow of blood/lymphatic vessels – preventing the wound from being healed.

Question 3

Tumours can also spread via metastasis, this is via the lymph nodes or blood vessels, patients here are unlikely to undergo radical therapy, instead undergoing palliative therapy. What do these two terms mean?

Answer 3

Radical Therapy – focusses on preventing the tumour from growing to improve survival, rather than destroying the tumour.
Palliative therapy is not aimed to destroy the tumour or cure the cancer, but instead to relieve any symptoms or suffering the patient is experiencing.

Question 4

Some tumours spread via lymph nodes, discuss how any lymph node spread is detected in a cancer of your choosing and explain what impact this has on the patient’s treatment.

Answer 4

Breast cancers primarily metastasise via the lymph nodes. Taking a sentinel lymph node biopsy can be used to determine if any spread has occurred. This is where a patient has Tc99m (radioactive) and a blue fluorescent dye injected near the tumour before surgery. The sentinel lymph node (the mostly likely to contain any tumour cells that have spread) is then identified based on the amount of gamma radiation and/or the fluorescence of the dye. This is then surgically removed and examined for any cancer cells. If there no are cancer cells present that treatment is likely to be local, but if these are cancer cells present treatment is likely required to be more aggressive and systemic.

Question 5

Give examples of tumours that spread via blood vessels and transcoelomic spread?

Answer 5

Prostate cancer is often associated with haematological spread to the brain, pelvis and liver – the successful dissemination rate is relatively low due to stress during transport, however, this will likely lead to change in management from radical to palliative treatment.
Transcoelomic spread is when the tumour passes across a body cavity examples of this are the ovary to the peritoneum and the lung to the pleural space – this is because in these areas there is no barrier like cartilage or bone preventing tumour growth. Smaller micrometastasis here are known as peritoneal carcinomatosis.

Question 6

Why is ‘cure’ a controversial word in cancer treatment and what terms are used instead to look at survival?

Answer 6

This is because the concept of curing/totally abolishing a cancer is incredibly rare at difficult as recurrence is very common – instead the aim is to reduce the risk of recurrence to as low as a value as possible – which is often coincided with the 5-year survival rates.

Question 7

What are the 3 necessary components required for a screening system?

Answer 7

• The disease and its early manifestation must be known and well characterised (for a significant marker) with the early-stage treatment being associated with cheaper costs and better patient outcomes.
• The target population is identifiable and large enough for costs to be worthwhile (no point in some populations)e.g., age, gender, familial history etc
• The individual must have some personal risk if the condition is being screened for hence will commit to the process (give consent)

Question 8

What are some potential problems patients might face during screening

Answer 8

• Anxiety relating to waiting for results or shock if results come back positive
• If the procedure is invasive or painful
• The threat of false negatives leading to unnecessary follow up treatments/screening associated with pain (as well as psychological effects and cost in general)!
• False negatives could put the patient at ease when they already have the disease and ignore any other symptoms of the disease
  Because of some of these issues, the age of starting and how often the screening is used is datable (accuracy of tissue imaging and these other issues) – as well as cost as well, given that most of these programmes and subsequent treatment is funded in the UK by the NHS which is government funded.

Question 9

What 10 Criteria do the WHO required for a screening programme to be considered beneficial?

Answer 9

I. The condition is an important health problem
II. Its natural history is well understood
III. It is recognisable at an early stage
IV. Treatment is better at an early stage
V. A suitable test exists
VI. An acceptable test exists
VII. Adequate facilities exist to cope with abnormalities detected
VIII. Screening is done at repeated intervals when the onset is insidious
IX. The chance of harm is less than the chance of benefit
X. The cost is balanced against benefit
Can be summarised into Easily identifiable, curable, and common (although cervical cancer is not common but is screened for).

Question 10

What three factors must the screen itself be?

Answer 10

• Not too unpleasant/painful/distasteful
• Cheap
• Accurate (sensitivity and specificity)

Question 11

Discuss some disadvantages of cancer screening?

Answer 11

• False negatives – a patient who has the disease, but the test comes back negative – symptoms could be ignored leading to disease progression and poorer prognosis – this may also put people close to that person less likely to be screened themselves due to lack of trust
• False positives – Where a patient does not have the disease but has a positive result – could lead to unwarranted stress and could be traumatic invasive testing and may make them less likely to undergo further screening tests in the future (distrust)
• Interval disease – Where breast cancer may occur between screening events – could become a shock to patients
• Compliance – will patients continue to come in subsequent screens or will they feel they are okay given the previous negative results (Education and advertisement campaigns as seen with prostate cancer in football league.
• Cost- these services must be cost effective by reducing the potential cost of subsequent treatment
• Person to patient – Some people may fear turning up in case of getting a positive result – that sudden transformation can be quite a shock to individuals

Question 12

What Cancer Screening programmes are currently used in the UK?

Answer 12

Breast cancer
Helps identify those with either carcinoma in situ or stage T1, which can be removed quite easily using surgery. This consists of a two-view mography (X-rays in lateral-medial and top-bottom). In 50–70-year-olds, Some countries use a different age cut-off, but in those younger than 40 the exposure to radiation is actually associated with increased development of cancer. Additionally, for every death prevented 2-3 cancers will be over diagnosed - Only a proportion of Tis will develop into invasive breast cancer – but at this moment there is no way to identify who these patients are – overtreatment.
Despite this, it can be associated with discomfort as well as radiation hazards. Additionally, due to the ‘taboo’ nature of breasts, this could be a difficult process for some patients.
Cervical Cancer
Despite not being a common disease, cervical cancer is one of the only cancers screened for. Despite dramatically improving survival rates – compliance is quite low at only around 70% - which is dropping over time – this can be due to embarrassment, over-confidence due to lack of symptoms and worried about the procedure or possible results – because of this campaigns like smear for smear are helping educate young people and encourage them to comply.
CRC
This used a high sensitivity faecal occult blood test looking for blood – but this can often put off patients – if the disease can be diagnosed early then the disease is very curable – but because symptoms don’t become apparent until late in disease. Because of this, compliance is only at around 65% - which needs to be increased to around 80% if it is to be effective!!
There are some issues as in some cases false positives can be caused by other problems like ulcers or polyps – hence a colonoscopy is required as a validatory follow up.

Question 13

Discuss why despite prostate and ovarian cancer being very common in the UK do not have a screening programme?

Answer 13

Prostate cancer can be either be indolent or aggressive, with those with the indolent disease often living with the disease rather than dying with it – hence this population would gain no benefit from this, whilst having to deal with anxiety related to diagnosis unnecessarily. But as PSA-test is offered if the patients wish to have one.

1. It is a significant issue and one of the biggest causes of cancer death 
2. The impact on patients is variable, in some cases the disease is indolent requiring minimal intervention
3. Is recognisable at an early stage 
4. Indolent – unnecessary, active surveillance better, repeat PSA
5. Isn’t specific in prostate cancer, benign hyperplasia
6. ^ this is common in older patients 
7. 
8. Screening when it is done early can increase patient survival rates IN SOME CASES (indolent)
9. Overdiagnosis, stress caused with diagnosis with limited impact of cancer itself on patient health.
10. Expensive, especially in an ageing population

Ovarian cancer screening was trialed using either ultrasound or CA-125 levels, but due to false positives (Can be used by other conditions like endometriosis) it was decided that it wasn’t financially beneficial or significantly improved patient survival.

Question 14

List the five generally types of imaging used in cancer with a brief description

Answer 14

• Plain/Contrast agent Radiography – used X-rays to detect bone fractures and mammography with high energy photons used to look at density of tissue. Not so good for soft tissue. Generally, 1st used and can help identify what other modalities should be used next!
• Computed Tomography – Great anatomical detail and can be enhanced using contrast agents -> used in radiotherapy planning.
• Magnetic resonance imaging – Great anatomic detail (especially in head/neck) – often used with CT in radiotherapy
• Radionuclide imaging (like PET) – gives physiological activity but poor anatomical information as images are hard to interpret
• Ultrasound – great anatomical detail for soft tissues like pelvic soft tissue

Question 15

What is image registration and give an example?

Answer 15

Imagine registration is where different imaging modalities are used in combination and aligned/overlayed to improve our knowledge/understanding of the patients situation, as each will have their own advantages/disadvantages. This can include using radionuclide (PET) alongside CT to combine both the anatomical and physiological information. CT and MRI can be used together to improve anatomical information and minimise any off-target effects in radiotherapy!

Question 16

Why is image registration so important in cancer?

Answer 16

Joins anatomical and physiological information so can be used for:

• Follow up-studies
• Detection
• Staging of the disease (will affect treatment)
• Radiotherapy planning – different imaging techniques will identify different target areas to minimise off-target effects of treatment even using MRI and CT

Question 17

Why might overlaying images sometimes not be enough?

Answer 17

There might be differences in patient position or the magnification of images

Question 18

What does NICE stand for?

Answer 18

National institute for health and clinical excellence

Question 19

What are guidelines and what is their purpose in radiology? (IREFER)

Answer 19

A set of statements to assist the practitioner and patients about healthcare options in specific circumstances – which is evidence based and constantly updated!

• To determine the most appropriate imaging examination
• Reduce the number of unnecessary referrals and radiation dose
• Overall improving clinical efficiency
• Based on research

Question 20

What questions should a radiologist ask before imaging has been carried out?

Answer 20

• Has the investigation been done before?
• Do you need to image the patient now?
• What will the results mean to changes in patient management (should be a change otherwise pointless)?
• What is the most appropriate technique?
• What information is given from the referrer? Is there enough information to suggest the correct examination is taken place

Question 21

Using potential bowl tumour as an example describe the various stages that would be undertaken to identify a potential tumour?

Answer 21

• Colonoscopy to take biopsies for analysis
• Referral to a CT scan for 3D imaging for a colonic mass
• If there is a mass then PET-CT scans an be conducted to look for metastatic spread
• The tumour may also be staged using a system such as TMN to determine therapy options and prognosis.

Question 22

Give examples of how changes in imaging guidelines may benefit patients.

Answer 22

• Some techniques like plain film X-rays may be unable to determine differences in benign tumours compared to malignant – which can be by CT. But because radiation damage can cause severe issues including cancer itself, if some patients can use other techniques to remove patients with other problems before CT to remove patients who do not require CT, this could remove/reduce the risks associated! And subsequently Digital Tomosynthesis is being investigated which produces multiple chest X-rays at thin layers at lower costs and radiation than CT which can be used to distinguish between the two!!!
• A similar thing is seen in prostate cancer with MRI used with the current ultrasound guided biopsy samples which were often not reach malignant regions, lots required and often associated with false negatives– in the PROMIS trial.
• Breast imaging – usually used X-rays or ultrasound, along with physical examination and a biopsy -»> now looking if MRI can be used as it can detect the occult tumours and tumour size!!

Question 23

What is radionuclide imaging

Answer 23

Is a technique, generally used as a last resort that maps patient physiology rather than anatomy using radiolabelled molecules which are taken up by a specific organ (usually determined by radiopharmaceutical)and participate in normal physiology like Technecium-99M which degrades to a gamma ray and is used to look at distribution of this!

Question 24

Why is Tc99m used in radionuclide imaging?

Answer 24

• Has a short half-life of around 6 hours
• It only emits gamma radiation
• Its activity is high enough so only a small amount needs to be given to the patient
• It is non-toxic and compatible with patient physiology
• The energy emitted is found within the range of energy that can be detected by a gamma camera (140keV)

Question 25

How does radionuclide imaging work?

Answer 25

• Tc99 + radiopharmaceutical can be administer via injection or via food
• The radiopharmaceutical will be specific to an organ or process, such as osteoclasts for bone metastases (should be compared to a baseline to understand how molecule is distributed in healthy patient)
• Gamma cameras have two heads that are used to image the patient (can be rotated in SPECT to gain clearer picture
• Emitted photons are detected by cameras- the scintillation crystal and the photomultiplier can convert photons into light which is used to produce the image via a serious of pixels
• This can be done over time to look at the molecules up-take and release from a particular organ
• This can often be carried out alongside CT (hybrid imaging) to gain information about both physiology and anatomy

Question 26

What is PET?

Answer 26

Positron emission tomography -> beta particle decay (from F18 labelled fluorodeoxyglucose resulting in positron emitted which combines with an electron causing annihilation -> two photons of equal energy are released in opposite directions and are detected.
The point of annihilation is used to determine the location of signal. Tumours often express higher levels of Gluts and have increased up-take, hence preferentially taken up by tumour cells.

Question 27

How does a CT scan work?

Answer 27

The patient lies on a bed that slowly moves through the gantry with a rotating X-ray source. An X-ray source is then shot at the patients – the difference is this is longer so can withstand high temperatures. The X-rays are detected based on tissue thickness/density.
A helical block of data can be produced along the coronal (Side to side), axial (through) and sagittal axis (up and down). Good at separating small differences in tissue density i.e. – bone, tissues, fat etc… Is usually used for diagnosis and staging and identifying metastatic spread – particularly in lung cancers and TAP for unknown origins

Question 28

What units are used for tissues in CT, explain them?

Answer 28

Hounsfield units – water =0, those less than 0 are air, lung and fat. Whilst those more dense are bone, muscle and blood.

Question 29

How is image quality ensured during CT scans?

Answer 29

A scout view is used (in 2-planes) to ensure the correct area is being scanned. The thickness of the slice and the quality of the image – can ensure the quality of the image is high but the radiation dose is low. Maximizing the thickness (or dose) can minimise noise due to diffracted photons. Then the window limits can be applied (for the HU’s) to see only specific tissues by essentially shifting the greyscale!!! – note the window limit ins the tissue that occupies the mid-point of the grey levels)

Question 30

What factors can dictate the scanner speed in CT?

Answer 30

• The type of scanner
• The number of simultaneously acquirable slices
• The protocols for scanning (exposures/windowing)
• CT workload
• If the patient has had any contrast media

Question 31

What are contrast agents in CT imaging, give some examples.

Answer 31

These are agents which can improve image quality of CT-scans to help better visualise specific organs better. These can be positive- iodine containing agents such as Gastrografin (orally veins and urinary system) and niopam (IV brain scanning)– negative agents may include CO2 and air.
These can be triggered electronically to look for changes in HUs
They are based on salts with benzene rings so it disperses well in blood and the X-ray beam is well attenuated.

Question 32

What are the two types of contrast agents (not in terms of function but structure)

Answer 32

Ionic vs non-ionic. Ionic will divide into positive and negative ions which may increase the number of particles and can increase the chances of a reaction. Because of this non-ionic agents are preferred – but are expensive.

Question 33

Give a disadvantage of using contrast agents

Answer 33

They can often result in reactions like anaphylaxis (‘allergic reaction) and urticaria (itchiness – reaction) – hence it is important that a risk-assessment is carried out beforehand.

Question 34

Apart from a traditional large machine, what other ways can CT be used in oncology?

Answer 34

Brachytherapy in cervical and prostate cancer ( diagnosis and pre-treatment to ensure correct area is being targeted) and colonography (after endoscopy)

Question 35

Give some advantages and disadvantages of CT, compared to MRI?

Answer 35

Advantages:
- Is faster
- Easier access
- No contradictions to non-contrast imaging (don’t have to worry about pacemakers if we don’t use a contrast agent)
- Good in bony soft tissue and vascular imaging and thorax
- Biopsy and intervention (embolization) possible during imaging
- Ability to window/contrast agents to improve image quality
Disadvantages:
- High dosage – 1 head scan is equivalent to 1 year of background radiation – must be high to offset noise
- Movement/metal can result in artefacts
- Often a risk associated with IV contrast reactions
- Beam hardening artefacts caused in thick base of skull
- Is expensive
- Still some issues with accessibility

Question 36

What are the advantages and disadvantages of choosing MRI over CT

Answer 36

Advantages:
- No radiation dose (less mutagenic)
- Clear difference between normal/abnormal tissue
- Better definition within organs and structures
Disadvantages:
- Scans take longer (40/45 min)
- Claustrophobia
- Patients with surgical devices/metal fragments run risk of burning the bone
- Usually longer waiting lists

Question 37

How does MRI work?

Answer 37

Different molecules have different resonant frequencies. A very strong magnetic field (1.5-3T) with coils I used to ‘pick up’ signals from hydrogen atoms of water molecules– as in the magnetic field they will line up and at a specific radiofrequency pulse the atoms can then deflect from this magnetic field – when this pulse is turned off the same energy is then released and collected spatially and using a greyscale is used to produce these images. Different amounts of water are in different tissues – therefore different results!!

Question 38

Why is using hydrogen in MRI valuable?

Answer 38

Because it has the right magnetic properties, it is the most abundant element, its signal is stronger than any other element, bone only produces a weak signal and air none.

Question 39

What are advantages of using MRI over X-rays?

Answer 39

• It is non-ionising
• Soft tissue definition
• Multi-planar capabilities (3D image)
• Good for diagnosis and staging
• Tumour characterisation based on values – based on different peaks
• Can use contrast agents for demonstrating vascularity (Gadolinium-based)

Question 40

What safety precautions must be in place in MRI machines

Answer 40

• Due to strength of the magnet the machine must be well protected, metal substances must not be in the room (large diameter)
• Patients must be placed to prevent movement (artefacts) and breathing instructions/gating are usually given to reduce impact of artefacts
• Some patients may be unable to take part due to tattoos, joint replacements, pacemakers etc

Question 41

What are the two ways of producing an image in MRI?

Answer 41

Spin-echo – slow, not noisy and are associated with higher image quality
Gradient echo – quick, noisy but low quality images – good for orientation before hand.

Question 42

What are the two types of weighted-images in MRI (think of TE and TR)?

Answer 42

T1-weighted:
-	Short time to repeat and echo time
-	Fluid is dark 
-	Image is darker 
-	Done first and can tell you about anatomy 
-	Fat appears bright 
T2-wieghted:
-	Long TR and TE 
-	Fluid is light 
-	Image is more black than white 
-	Useful in pathology looking at fluid vascularisation 
-	Fat is dark

Question 43

How can we remove fat on a MRI image?

Answer 43

Fat can obscure some physiology – hence we can remove the signal using one of two techniques; STIR (short Tau Inversion recovery – lots of signal flipping) or SPIR (spectral inversion recovery – we ignore frequency fat resonates at).
Ignoring the cerebral spinal fluid using FLAIR (fluid attenuated inversion recovery) – may be useful at looking at fluid trapped in other tissues like in MS!

Question 44

What are the disadvantages of MRI?

Answer 44

• Expensive
• Not ideal for real time
• What if the patient is too large or has tattoos, pacemakers or joint replacements
• Gadolinium can cause nephrogenic systemic fibrosis
• Claustrophobia and is loud
• Artefacts can reduce image quality

Question 45

How does ultrasound work?

Answer 45

Simply images are created by transmitted sound waves which are reflected and detected by a hand-held probe which receives the signal and uses a transducer to convert these to electrical signals which are used to produce an image. Tissues with different densities will reflect the waves differently. Look at echogenicity of tissue!!

Question 46

What is an artefact?

Answer 46

Any structure in an image that does not correlate directly with an actual tissue (can be perceived objects that are not there, missing structures or misrepresented in terms of location).

Question 47

What are the advantages of ultrasound technology?

Answer 47

• Cheaper and more readily available
• Non-invasive
• Does not use ionising radiation
• Excellent soft tissue visualisation
• Accurate measurement of 2D/3D
• Biopsy under direct ultrasound visualisation is possible
• Blood flow assessed with Doppler at same time
• Imaging is real time
• No patient preparation is required
• Can be used during operation
• Readily acceptable by patients
• Can be used to monitor progress

Question 48

Disadvantages of ultrasound

Answer 48

• Relies on competent sonographer
• Cannot identify types of tissue 100% reliability
• Needs an up to date scanner
• Cannot scan through gas/bone
• Artefacts

Question 49

What is Doppler ultrasound?

Answer 49

This is where changes in the frequency of emitted sound from a source that is moving with respect to the observer – this can be red blood cells – this can allow colours to be allocated based on the size and direction of this shift!!
Power Doppler sonography indicates only that blood flow is present (nothing about velocity) – but helps low flow vessels to be identified (associated with tumours)

Question 50

What imaging techniques can be used to look at blood flow in cancer?

Answer 50

Ultrasound with doppler, CT and MRI (gadolinium)

Question 51

Why is the use of transrectal, transcervical and endoscopic ultrasound scans advantageous?

Answer 51

The transducer is close to the organ of interest and a higher frequency can be used which can increase the detail of the image