Imaging Procedures HEAD Flashcards
Axial CTs of the head are obtained parallel to what ?
Inraorbital- meatal line
How can you finesse a head Ct to lower dose to the orbital region and minimize beam hardening
Image 15 degrees above Infraorbital- meatal line . Parallel to skull base
Obtaining thinner sections through the posterior fossa of the head does what for the scan?
Reduces beam hardening artifact
Artifact is usually caused by the petrous pyramids in the head ( these are temporal bones at the base of the skull shaped like a pyramid)
What data acquisition mode will improve z axis resolution in a head ct?
What is the benefit of having higher resolution in head Ct ?
sequential mode ( also called axial mode)
better visualization of the brain during helical scanning
What size sections are obtained from skill base to posterior fossa? From posterior fossa to vertex?
(2-5 mm)
5-10 mm
Under what settings are thin (0.6mm) detector configurations used
thicker reconstruction settings
what reconstruction kernal is typically used for the head
standard or soft tissue
What are some other terms used to describe an algorithm?
filter or kernel
What kernel can maximize bony details and help you see fractures or skeletal anomalies
high spatial frequency kernal
What are the window levels and window widths for the following:
Gray/ white matter
Bone
Hemorrhage/ hematoma
Acute ischemia
Gray/ white matter
Bone
WL 400 WV 3000
Hemorrhage/ hematoma
WL 75 WV 150
Acute ischemia
WL 35 WV 25
What is the doctor trying to diagnose by ordering a non contrast head ct for a trauma patient?
hemorrhage, blood clot, or acute stroke
True/ False . The initial use of contrast in a patient with head trauma getting a CT can potentially mask a intra cranial hemorrhage
true
What scan must be obtained before proceeding with thrombolytic therapy?
Non contrast head ct to rule out intracranial hemorrhage
Indications for non-contrast head CT
tumors Hydrocephalus abscess bony abnormalities congenital abnormalities primary neoplasms of brain endocrine pathologies
What three factors aid in the high resolution imaging technique required to image temporal bones and auditory canal ?
THIN SLICES
small DFOV
High resolution kernels
Explain the concept of MPR
the process of using axial acquisitions to create nonaxial two-dimensional images ( coronal, sagittal, oblique, or curved plane images)
What is the benefit to the patient of conduction isotropic MPR in Ct ?
What scanners implement this technique?
Reduces added patient dose
MDCT scanners
How do you maximize the resolution of small bony features in the inner ear ?
Acquire targeted thin slices on both sides with a small Display field of view
Small DFOV allowed for a more zoomed in picture
What algorithm is used to acquire CT images of temporal bones
high spatial frequency algorithm / bone algorithm / bone kernel
Imaging orbits can be obtained in two ways:
How thin are these sections near the orbits ?
- along the axial plane
(parallel to IOML) - perpendicular to the axial plane
(1-3 mm)
Acquisition of the orbit may include the following MPRs:
The oblique MPRs go through which structure?
Axial
oblique sagittal & oblique coronal
The optic nerve
What reconstruction kernel is typically used to image the orbit?
What kernel could be used in the case of trauma ?
soft tissue or standard
bone
What is the window level and window width of soft tissue and bone?
Soft tissue
WL 40 WW 400
Bone
WL 400 WW 3000
In what case is contrast needed when imaging the eyes?
Looking for vascular abnormalities , inflammation, or neoplasms
True/ False.
Its not necessary to optimize the protocol because the eyes are not sensitive to radiation
false