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CT Scan

Computed tomography

two types

Helical
spiral

Four densities

still apply

Hounsfield Units

measure of relative density (WATER IS ZERO) (Air<Fat< Water< Soft Tissue< Calcium< metal)

By adjusting the gray scale level one can...

differentiate between the ventricles of the heart
IN ANOTHER WINDOW
detail the air ways of the lungs

Post-processing******

Multiplanar reformatted images
(spiral processing)
sagittal
coronal

3-D Images

digitally take out everything that is not bone

Scan Parameters

Anatomy: Brain, Neck, Chest, ABD, pelvis, bone
Contrast: Oral, IV, other (rectal, bladder)
Slice Thickness: (0.6-10mm)
Scan Timing: breath hold, arterial, venous, delayed phase

Be able to ID the type of contrast:
IV contast vs Oral contrast

IV contrast: the density within the aorta will be similar to that of the vertebrae
Oral contrast: you will see difference in the tissue within the observable intestine.

Pre contrast

you see the kidneys

Post contrast

30 sec post
one can see the parenchyma

delayed

one can see the draining into the ureters

**** Enhancing (Solid) renal mass

an increase in H.U (density) from pre to post contrast

*** PRE contrast required

Renal cell carcinoma...

until proven otherwise

Hepatic Vein drains into the

IGC

Is CT sensitive enough for gall stones?

NO!!!! (ok sometimes)
they are the same density as the fluid around them

***Ultrasound is much better for this DX

HYPOdense lesions in the spleen

multiple lesions lymphoma

If air density is found in tissue that is in bubble form all over...

necrotizing fasciitis

brain sand is in the

pineal gland

Glioma

A tumor of the Brain

CT Angiography

Inject intravenous contrast
obtain scan during the arterial phase
Helical CT (volumetric Data)
Post- Processing

CT Angiograph can evaluate:

AORTA
PULMONARY ARTERIES CAROTID ARTERIES PERIPHERAL VASCULAR SYSTEM CIRCLE OF WILLIS

CTA

CT Angiograph

CT- Guided interventional Radiology

use images to guide procedures that would normally require surgery

Cardiac CT

MULTIDETECTOR (64 SLICE) SCANNERS SUB-MM SLICE THICKNESS EKG GATING

CORONARY ARTERY CALCIUM SCORING CORONARY ARTERY CTA

Coronary artery Calcification Scoring

Amount of Calcium in the coronary arteries is proportional to the overalll amount of atherosclerotic plaque.
Quantitative measure of this
calcium gives an assessment of risk for significant stenosis
Does NOT directly measure the degree of stenosis. NO evaluation of cardiac function.

Report Total Score

Plaque burden
Percentile

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