CT scan Finals

make the contrast media thin

after myelography, CT of the spine must be delayed for 1-3hrours to?

Helical acquisition

allow for clearer coronal or oblique reformats and decrease susceptibility to motion artifact

: Evaluation of sinus cavity for tumors, masses, invasive sinusitis, suspicions of abscess.

PARANASAL SINUS WITH CONTRAST CT PROTOCOLS purpose:

3mm

PARANASAL SINUS WITH CONTRAST CT PROTOCOLS reconstruction

Hard palate through frontal sinuses

PARANASAL SINUS WITH CONTRAST CT PROTOCOLS scan extent

150 mAs s (CTDIvol [volume CT dose index] 34 milligray [mGy])

effective mAs for neonates

250 mAs (CTDIvol 57 mGy)

effective mAs for adolescents

320 mAs (CTDIvol 72 mGy)

effective mAs for adults

200 mAs (CTDIvol 45 mGy)

effective mAs for children ages 1 - 10 years

pronounce a prolonged "e" during scanning.

. Another technique that has been used to evaluate the aryepiglottic folds and pyriform sinuses is to ask the patient to

Valsalva maneuver.

. This technique helps to distend the pyriform sinuses.

1. BUN/creatinine 2. Informed Consent Form (signed by px, RRT and MD) 3. Ask the px for history of allergy

3 things to ask before contrast

frontal, ethmoid, sphenoid, maxillary

4 sinuses

they do not allow the gantry to be tilted when in helical mode.

A disadvantage of many multidetector CT systems is that

anteroposterior (AP) and lateral projections.

All studies should include scout images in both ___

supine, IOML perpendicular to the table

CT IAC/Temporal Bone Protocol: Pt position

none

CT IAC/Temporal Bone Protocol: contrast and injection rate

breath hold

CT IAC/Temporal Bone Protocol: respiration

myelography

CT examinations are performed after ___ to enhance or clarify myelographic findings of intradural and extradural abnormalities.

mucosa, lymph nodes, pathologic tissues

CT scan of the nck with contrast media is used to visualize

detection of hydromyelia

CTA DOES NOT do

CTDIvol x scan length

DLP formula

Split Bolus Technique

Dividing the dose into 50% to enhance the organ being examined

where is the start location for cervical spine ct scan?

EAM

Sized to include entire facial area, including tip of nose.

FOV for paranasal sinus

1. Type of equipment available (64 slice vs 16 slice) 2. Setting 3. Particular preferences of the radiologists in charge

Factors that influence a specific site's protocol parameters

age and head size.

For 40 to 64 detector scanners, the effective mAs (defined as the mA × the gantry cycle time/helical pitch) is adjusted according to the

0.75 × 0.75-mm collimator.

Image acq for paranasal sinus

brain perfusion imaging

In addition, cerebral CTA can be combined with___ to assess the viability of brain parenchyma and its vascular supply.

modified Valsalva maneuver.

In some institutions images of the neck are acquired while the patient performs a

0.6mm

In temporal CT, what is routinely used as a collimator?

extradural neoplasm.

Intrathecal contrast medium may be helpful for the diagnosis of degenerative disk disease and other disk diseases, such as

degenerative disk diseases, slipped disc, extradural neoplasm

Intrathecal contrast medium of the spine is used to diagnose

Display Field of View(DFOV)

It determines how much of the scan field of view is reconstructed into an image

Scan Field of View(SFOV)

It is the area being scanned. It is measured from a system isocenter to the most distant located edge of the patient.

orbits CT protocols

It is used for evaluation and management of neuro-ophthalmic and orbital diseases, especially for trauma, proptosis, and childhood leukocoria

orbitomeatal line

It was once common to program the cross-sectional slices of the brain to be parallel to the

15 degree caudad and 15 degrees rotate head of the affected side

Law's position

1 to 3 hours

Most reports suggest a delay of ___ between the intrathecal injection and scanning.

contrast injection technique referred to as a split bolus.

One strategy for addressing these contradictory goals is a

patient supine and the neck slightly extended.

Routine scanning of the neck is typically performed with the

2 minutes is observed.

The first dose is given and a delay of about

120 kVp

The gantry cycle time is set at 1 cycle or gantry rotation/second. The kilovolt peak (kVp) is usually?

allow sufficient time after contrast administration for mucosa, lymph nodes, and pathologic tissue to enhance

The goals in CT scanning of the neck are to

1) to accurately measure stenosis of the carotid and vertebral arteries and their branches 2) to evaluate the circle of Willis for completeness using three-dimensional reformations of cerebral vasculature in relation to other structures 3) to detect other vascular lesions, such as dissections or occlusions.

The goals of CTA for cervicocranial vascular evaluation can be summarized as follows:

sharpening the image.

The kernel affects the appearance of image structures by

maxillofacial studies

The split bolus injection technique is also frequently used for

maxillofacial

The split bolus injection technique is used for the study of

Valsalva maneuver.

This maneuver requires the patient to blow the cheeks out.

intrathecal administration of water-soluble contrast material.

Visualization of intradural structures is improved by the

sixth lumbar vertebra (an anatomic variant) that requires additional scans.

When scanning the lumbar spine, it is important to note whether the patient has a

axial (step-and-shoot) techniques

are often used for routine brain imaging.

Scan parameters

are quite similar to CTA, except images are acquired while contrast is in the venous enhancement phase.

cerebral catheter angiography or digital subtraction angiography

are still generally regarded as the gold standard for the imaging of cerebrovascular disorders, those techniques are time-consuming and are associated with a small, but significant, rate of permanent neurologic complications.

no longer opacify the vasculature

by delaying scan acquisition the injected contrast agent will

1mm

commercially available units can be collimated to at least

dose-length product (DLP)

factors the length of the scan to show overall dose output

1 mL/lb to a maximum of 80 to 100 mL for adults

intravenous (IV) contrast t is administered by power injector at standard doses of

CTDI100 (mGy)

is a linear measure of dose distribution over a pencil ionization chamber and hence does not take into consideration the topographical variation of a human body and is therefore not in clinical use.

CT dose index (CTDI) (measured in mGy)

is a standardized measure of radiation dose output of a CT scanner which allows the user to compare radiation output of different CT scanners.

CTDIw (mGy)

is closer to the human dose profile as compared with the CTDI100 , 2/3 CTDI100 (periphery) + 1/3 CTDI100 (center)

CTDIvol (mGy)

is obtained by dividing CTDIw by pitch factor

CT venography (CTV)

is used for the depiction of venous anatomy.

CTDI100

measured over a 100 mm long ionization chamber

CTDIvol

more commonly used index for helical scanners

supraorbital meatal line

more recent practice favors using the

IV contrast

not routinely used to evaluate for otomastoiditis or hearing loss

glabellomeatal line

other term for supraorbital meatal line

weight in kg.

pedia dose depends on

CT angiography

procedure that is considered as non invasive?

Bone kernels

produce a sharper image with higher spatial resolution.

scouts

reference images acquired before scanning

kernel, also known as a convolution algorithm

refers to the process used to modify the frequency contents of projection data prior to back projection during image reconstruction in a CT scanner

CT

remains a quick, clinically effective, and cost-effective method for evaluating most orbital problems

: Frontal sinuses through hard palate (Scan Craniocaudal)

scan extent for paranasal sinus

IV contrast

used for the evaluation of vascular pathology (e.g., dissection, tumors) and may be considered for some types of infections such as coalescent mastoiditis or for the evaluation of abscesses.

intravenous (IV) contrast

usually of the low osmolar type

base of the brain

where is the circle of willis located?

mid-orbit

where is the start location for neck ct scan?

CT angiography

y has the advantages of being noninvasive and widely available