Session 9 - Imaging Flashcards
What common imaging modality is adapted in the generation of CT scans? What are the major modifications to that technique?
X-ray imaging making use of digital technology to capture, process, compile and display resulting images
What would be the difference(s) in appearance of a single frame CT scan and a plain film radiograph of the head?
Plain film radiographs of the head image the bony cranium perfectly but show a void where the brain is to be expected, whilst CT radiographs image both the cranium and soft tissues of the brain.
In emergency cases of imaging the brain, why do radiologists always “order CT scans” as a first choice?
CT scan are simple to perform and patients do not need to be especially prepared for this imaging technique, the results are produced instantly. The technique is also cheap, hence cost-effective
What would be the usefulness of ordering a CT scan for a patient with a suspected fracture in the head and neck region?
Owing to the ability of this technique to image both bone and soft tissues adequately, fractures of the head and neck region may be accompanied by bleeding and soft tissue injuries. CT imaging will help to identify any of these injuries equally well (relatively speaking).
What limits the usefulness of CT imaging in the diagnosis of diseases or trauma to the brain?
Dosage of X-ray radiation. Some new (i.e. recent) pathologies as well as other soft tissue complications such as bleeding and tumours may also be missed by the CT method, unless contrast enhancement techniques are applied in conjunction with the native technique
What might a whitish trail within the brain resembling a stream or trail on a CT indicate?
Subarachnoid Intraparenchymal bleed (of most probably arterial blood-from a berry aneurysm)
To generate MRI images, a certain compound needs to be present in tissues being imaged. Name this compound?
Water
What chemical element in particular, forms the basis of MRI imaging?
Hydrogen and in particular, Hydrogen ions
Certain categories of patients are not suitable for MRI brain imaging. Name these
Patients with penetrating injuries to the head or eyes Patients with metal prostheses: Patients suffering from claustrophobia
Brain scans produced by the technique of MRI imaging are classed as either T1- or T2-weighted. What is the basis of T1- and T2-weighting?
It is the computer-driven pulsing and relaxation of magnetisation of Hydrogen ions. Pulse sequences of magnetisation can be varied to produce different signals from the protons, hence the different images.
What tissues of the brain are best imaged using the technique of MRI imaging?
Water- and/or fat-containing tissues, thus the soft tissues of the brain, in particular.
Apart from the dangers of MRI imaging what is the major factor that limits its usefulness in the imaging of the brain?
It is not so effective in imaging bone or hard tissues. As such, it is not ideal for imaging fractures of the head.
The various types of haemoglobin in the blood produce different imaging signals, making the signals rather complex in composition.
Le Fort I (horizontal maxillary fracture)
a fracture of the maxilla just above the teeth which remain in the detached portion of the bone.
Le Fort II
the body of the maxilla is separated from the facial skeleton with a horizontal fracture through the nose and vertical fractures from the floor of the orbit.
Le Fort III
a horizontal fracture through the top of the nose, the sphenoid bone and the fronto-zygomatic sutures and zygomatic arches. The maxilla and other bones of the face are entirely separated from the cranium
