CT

Answer 1

-multiple 2D, slice-like images (each millimeters in size) formatted in multiple imaging planes to display 3D images in various formats

Question 2

hounsfield units

Answer 2

-A CT image is composed of a matrix of thousands of tiny pixels
-each is computer-assigned a CT number from –1000 to +1000 measured in Hounsfield units (HU) , after Sir Godfrey Hounsfield
-Density of tissue determines amount of Hounsfield units (denser structures absorb more energy)
-Air = -1000, Fat = -40 to -100 HU, Water = 0, Soft tissue = 20 to 100 HU, -Bone = 400 to 600 HU -> bone absorbs contrast

Question 3

timing

Answer 3

2s-10s per slice -> every time donut comes around
-2-5ml SA
-continuous rotation
-abdomen- 30s

Question 4

multiplanar reformation

Answer 4

-overlapping images- reformat to see better
-single acquisition

-For Maximum Intensity Projection:
-CT Angiography
-Cardiac Imaging
-more specialized = more contrast
-allergies to iodine, renal function (filtered by kidneys)

Question 5

abnormalities on CXR -> CT indication

Answer 5

Evaluate abnormalities on CXR
Confusing shadows on plain x-ray
Pts with pneumonia not responding to therapy
Empyema verses abscess, evaluation of pleural Effusions
Pulmonary nodules – new or follow up
Interstitial lung disease
Lung/Hilar/mediastinal masses

-Negative CXR with clinical suspicious pathology
-Staging and follow up malignancies
-Evaluation vascular abnormalities ( PE, AA)
-Trauma
-Performance CT guided interventional procedures

Question 6

multislice CT scanners permit very fasting imaging

Answer 6

-(head to toe in less than 10 seconds)
-development of new applications for CT
-virtual colonoscopy
-virtual bronchoscopy
-cardiac calcium scoring
-CT coronary angiography
-these are controlled elective setting

Question 7

CT hazards and disadvantage

Answer 7

-Radiation to patient
-Requires computer processing power (expensive scanner)
-Portable CT Scanners
-Need space dedicated to its installation, and sophisticated

CONTRAINDICATIONS: NONE***

Question 8

patient considerations

Answer 8

Claustrophobia
Cooperation
Size & weight restrictions
Allergy to iodinated contrast agents -> you can still do it but need to make sure its done in controlled (non acute) setting

Question 9

terms for anatomic definitition

Answer 9

-Chest CT scans are usually “windowed” and displayed in at least 2 formats
-ex. if looking for pleural effusion -> look for lung window -> changes gray scale so you can see it better
-bone window- fracture
-Windowing AKA “grey-level mapping”: contrast enhancement.
-process in which the CT image greyscale component of an image is manipulated to highlight particular structures.
-“Post-processing” allows for additional manipulation of the raw data
-Benefits:
-demonstrate pathology
-without repeating a study
-Without radiation re-exposure to the patient