Imaging of Soft Tissues & Foreign Bodies

What are foreign bodies? Give a simple definition.

- they are are objects lying partially or wholly within the body that originated in the external environment.

Foreign body placement can be either voluntary or involuntary. True or false?

TRUE

Are implanted medical devices considered foreign bodies?

YES (in the broad sense of the term)

When imaging a potential foreign body in a patient, what should you consider as a radiographer?

- consider the radiodensity of the object; how well can it be seen on an x-ray?

- consider the location of the foreign body; is it located near vital organs?

- consider the material of the foreign body/object; does the material have potential to leak / erode in that area of the body?

- consider the quantity of foreign bodies; make sure all of the foreign bodies (if there are more than 1) are visible.

What are some potential problems that can arise when imaging foreign bodies? What are some barriers to good quality imaging?

- if the foreign body is radiopaque or not; is it visible on x-ray?

- for example, some fish bones cannot be seen on x-ray, some can. Some materials e.g. plastic may not be shown on x-ray.

- some foreign objects e.g. sexual objects may cause patient embarrassment = dignity should be maintained.

- patients with open knife wounds may not be able to move and so placing the detector at a close distance may be difficult.

- in severely injured patients with foreign bodies it may be difficult to remove all artefacts (e.g. clothing). Make sure the radiologist / reporting radiographer is aware of any artefacts present.

What are the standard principles for foreign body imaging? What should you ensure when imaging them?

• Get a good patient history / observation of the patient

• Ensure image recording system and any equipment used is clean and artefact free (especially for small foreign bodies)

• Remove what can be removed from the patient (as much as possible)

• Use radiopaque marker to show entry wound on resultant images

• Take a flexible approach - consider alternative modalities

Which imaging modality is usually the first line investigation for foreign bodies?

- usually plain film x-rays.

What are the advantages of using plain x-rays for foreign body imaging? List them.

• Readily available

• Image manipulation /windowing can be used to enhance the potential visualisation of a FB

• Radiopaque markers can be safely placed on the cassette / detector to identify the position of any entry-wounds

• Useful for pre-MRI orbital survey projections

• Fluoroscopy can be used in theatre to assist in the removal of radiopaque FBs

What are some disadvantages of using plain x-rays for foreign body imaging?

• Limited ability to detect certain materials e.g. wood, plastic and some types of glass

• Limited ability to detect certain types of fish bones which are radiolucent.

What are the advantages of using CT scans for foreign body imaging?

• CT is inherently very sensitive for soft tissue imaging

• Image manipulation and 'windowing' are excellent

• Good visualisation of FB in the orbit, especially prior to removal

• 3D reconstruction is available

What is a disadvantage of using CT scans for foreign body imaging? (obvious one)

- high radiation dose.

What are the advantages of using ultrasound for foreign body imaging? List them.

• Readily available

• Cheapest modality

• Portable - can be used in clinic or theatre

• Excellent for visualising wooden FB's which are radiolucent on x-ray

• Real-time modality, so tissue movement can be used to aid detection

• Sterile gel is available when wounds complicate achieving optimal skin contact by the transducer

What are some disadvantages of using ultrasound for foreign body imaging?

• Contact (with probe) is required so wounds can cause difficulty when achieving optimal skin contact with the transducer

• Limited applications in FB imaging, since ultrasound is unable to pass through bowel gas or bone

What are the advantages of using MRI for foreign body imaging?

• Very sensitive for soft tissue imaging

• Utilisation of different sequences can assist in FB detection

• 3D reconstruction is available

What are some disadvantages of using MRI for foreign body imaging?

• Most expensive modality

• Must never be used if there is any possibility of a metallic FB

• Claustrophobia

• Safety of patient with unknown foreign body

Ingested foreign bodies can be classified into 2 types:

- Accidental ingestion

- Deliberate ingestion

What are some example of foreign bodies that have been accidentally ingested?

- Dentures

- Food bones e.g. fish bones, chicken wings

- Children ingesting toys, batteries, etc.

What are some examples of cases where foreign bodies have been deliberately ingested?

- Children ingesting toys, batteries, etc.

- Patients with mental health issues may ingest objects e.g. for self-harm, compulsive disorders etc.

- Drug conveyance / smuggling.

- Coins & Batteries

Why are button batteries dangerous when ingested?

- when ingested, button batteries react with water & cause alkaline caustic injury i.e. tissue liquefaction within 2 hours.

- it could lead to damage to oesophageal tissue, intestinal tissue, arterial etc. Could even lead to death.

How can you tell, on an x-ray image, that there are drug concealment / packages present?

1. Double condom sign - a lucent rim of air trapped between multiple layers of latex, which may be less evident with well machine wrapped packages.

2. Tic Tac sign - multiple oblong, uniformly shaped packages.

3. Rosette sign - air trapped in the knot where the condom is tied.

Radiographic density of packages - how can each drug package look different on x-ray?

- the density of the ingested packet is variable and is determined by the type of wrapping material used, ranging from densely radio-opaque aluminium, (which is rarely employed these days) to radiolucent wax and the contents of the packet.

- different drug packages may have different appearances on a radiograph.

Soft tissue foreign body cases can be classified into 2 types:

- Accidental

- Deliberate

Give examples of cases where accidental soft tissue foreign bodies are acquired.

• Road Traffic Collision

• Sexual (consented)

• Iatrogenic (caused by medical treatment)

• Occupational (construction workers)

• Slips & trips (e.g. falling & landing on glass)

Give examples of cases where deliberate soft tissue foreign bodies are acquired.

• Mental health cases

• Sexual assault cases

• Physical assault cases

What are some examples of minor radiopaque penetrating foreign bodies?

• Glass

• Wood if painted

• Metal - except aluminium!

What are some examples of minor radiolucent penetrating foreign bodies?

• Plastic

• Unpainted wood

• Others

What views / projections should we do when plain imaging minor penetrating foreign bodies?

• AP/DP of affected area to include enough bony anatomy for confirmation of area

• Tangential view (modified views - to check how far the FB has penetrated into the soft tissue)

Gun shots could cause different types of appearances on radiographers based on the type of gun, speed of bullet, etc. :

• High velocity - shock wave, large exit wound

• Low velocity - no exit wound

• Fragment / Change shape on entry (mushrooming)

• Yawing (slows down and changes direction in tissue)

• Shotguns - low velocity but cause massive tissue damage

Some objects / foreign bodies could be left inside a patient (by the surgeon) during a major surgery / operation.

Give some examples of these retained post-op objects.

• Swabs

• Guidewire

• Needle

• Sponge

• Forceps

What is the common imaging protocol for retained post-op foreign bodies/objects?

• If surgical count incorrect, a DR image of the surgical site before patient leaves theatre

• May consider using a C-arm if object is suspected

• Small needles may only be visualised on DR images