Procedures- Brain Flashcards
What type of acquisition is used for a CT head scan?
Axial
What are the axial plane CT images to be set parallel to during acquisition?
Infra-orbital mental line
How many degrees above the IOML is the head acquisition performed?
15
If the acquisition for a CT head is set to 15 degrees above the IOML, what is the scan plane parallel to and how is it beneficial?
Parallel to the skull base;
Reduces orbital dose and minimize beam-hardening artifact
Which type of image acquisition provides the best z-axis resolution?
Axial/sequential
What size slices or sections are acquired from the skull base through the posterior fossa?
2-5mm
What size slices or sections are acquired from posterior fossa through the vertex?
5-10mm
What artifact is reduced when thinner sections are acquired through the posterior fossa?
Beam-hardening caused by petrous pyramids
Z-axis resolution allows for high quality exams of the brain with what type of acquisition?
Helical/volumetric
Which type of scan acquisition is preferred whenever MPR or 3-D imaging is anticipated or when examination speed is a critical issue?
Helical/volumetric
What size slice thickness/detector configuration is used for data acquisition of a CT head?
Thin (~0.6mm)
What size slice thickness is used for reconstructions of a CT head?
Thick
What algorithm is used for reconstruction of a CT head?
Standard or soft tissue
What type of algorithm can also be used for reconstruction of the head for suspected fractures or other skeletal abnormalities?
Bony or high spatial frequency
What’s the WW and WL setting for Gray/white matter?
WL: 35 and WW: 100
What’s the WW and WL of bone?
WL:400 and WW: 3,000
What’s the WW and WL of a hemorrhage/hematoma?
WL: 75 and WW: 150
What’s the WW and WL for acute ischemia?
WL: 35 and WW:25
What type of pathology is improved by high-contrast windowing?
Acute stroke
What CT exam of the brain is routinely indicated for trauma to diagnose intracranial hemorrhage or hematoma?
Non-contrast
Why is administering CM in a trauma patient initially contraindicated?
Contrast can mask subtle signs of hemorrhage
What exam is usually ordered first by protocol for evaluation of acute stroke?
Unenhanced CT of the brain
What must be ruled out on a scan before thrombotic therapy?
Hemorrhage
What are other indications of a head CT?
- Congenital abnormalities
- Hydrocephalus
- Mass or tumor
- Primary neoplasms of brain- meningioma, schwannoma, and gliomas like astrocytoma
- Metastatic lesions usually from lung, breast, renal and GI cancer
- Bony abnormalities
- Endocrine pathology
What indications would iodinated contrast be administered for a head scan?
Arteriovenous malformation, suspected neoplasm, or attention to the pituitary gland
What type of scan acquisition, what size thickness, and what imaging plane is acquired for a pituitary scan?
Coronal plane, thin section (1-3mm), helical imaging
What type of imaging technique is required for a study of the temporal bones and internal auditory canal?
High-resolution imaging technique
What factors are involved when using a high-resolution imaging technique for temporal bones and internal auditory canals?
Thin slices
Small DFOV
high-resolution reconstruction algorithm
What two planes are thin sections of a temporal bone reconstructed into?
Axial and coronal
What factor of MPR imaging allows for reduced radiation dose from coronal sliced images during axial acquisitions?
Isotropic
Should reconstructions of temporal bones be acquired unilaterally or bilaterally?
Bilaterally
What is the reason for using a small DFOV or increased zoom factor on a temporal bone reconstruction image?
To maximize resolution of the small bony components of the inner ear
What type of algorithm is used to reconstruct the temporal bones?
High spatial frequency/bone
What is the biggest cause of image degradation when imaging temporal bones?
Motion
What are 2 indications for CM for a CT of the temporal bones?
Tissue neoplasm, vascular anomalies
When imaging orbits, the axial is to be parallel to what anatomical landmark?
IOML
What size slices should an axial acquisition of the orbits be?
Thin- (1-3mm)
How do coronal images align with axial images of the orbits?
Perpendicular
Why would the acquisition angle be adjusted for a CT of the orbits?
To avoid dental apparatus
What anatomical structure is the area of interest for oblique Sagittal and oblique coronal MPR of the orbits?
Optic nerve
What algorithm is used when reconstructing orbits?
Standard or soft tissue
What would an additional bone algorithm for orbit reconstructions be useful for?
Trauma indications
What is the WW and WL of soft tissue of the orbits?
WL 40 and WW 400
What would the WW and WL setting be for orbit bone window?
WL 400 and WW 3,000
What indications would require CM to be administered for a CT of the orbits?
Vascular abnormalities, inflammation, suspected neoplasm
When imaging sinuses, the axial images should be parallel to what?
Hard palate
The acquisition for a sinus exam should extend inferiorly and anteriorly to include which to anatomical structures?
Maxillary and ethmoid sinuses
The acquisition for a sinus exam should extend superiorly to include which to anatomical structure?
Frontal sinus
The acquisition for a sinus exam should extend posteriorly to include which to anatomical structure?
Sphenoid sinus
Which two patient positions can be performed to obtain coronal images of the sinuses?
Prone or supine with head dropped back
What is a benefit of having an additional coronal position?
Demonstrates changing air-fluid levels and other sinus-related disease
The coronal and sagittal planes of the sinuses help visualize which anatomical structure?
Osteomeatal complex
Which structure is a common place to acquire sinus inflammation?
Osteomeatal complex
What type of sinus scan provides a limited coronal acquisition through the sinuses?
Low-dose survey
What two reconstructions should be created when imaging the facial bones?
Axial and coronal
Which two algorithms are used to visualize the facial bones?
Standard and bone algorithms
What is the WL and WW of soft tissue for the facial bones?
WL 40 and WW 400
What is the WW and WL of bone for the facial bones?
WL 400 and WW 3,000
What two plane acquisitions are needed for CT of the TMJ joints?
Axial and coronal
What two positions can the patient perform TMJ joints for a CT?
Open- and closed- mouth
What is an indication for CM with a TMJ CT scan?
Suspected neoplasm
