CT Flashcards
What does a CT scan measures?
Density
On CT image, what is calculated for every slice?
Attenuation coefficient
What are the two types of CT imaging?
Sequential scanning
Helical scanning
In which type of CT scan do we usually use?
Sequential scanning
Helical scanning
Helical scanning
For lungs HRCT, which CT scan will we choose?
Sequential scanning
Helical scanning
Sequential scanning
2 new CT scan options
Multi Slice CT (256 and 320 detector row MSCT)
Dual source CT
HU for bones
+400 -> +1000
HU for Soft tissues
+40 -> +80
HU for water
0
HU for fat
-60 -> -100
HU for lungs
-400 -> -600
HU for air
-1,000
In windowing, above the interval values is shown in which color?
White
In windowing, below the interval values is shown in which color?
Black
Parameters for windowing (2)
Level (HU center)
Width (HU values within the window)
Non contrast CT is used for
Give examples
Foreign body Kidney stone Lung HRCT Adrenal gland adenoma Bone structure Lipoma Atherosclerosis Exclude brain hemorrhage
Contrast CT is used for
Give examples
Angiography Study vascularization Tumor differantiation Inflammation process Abscesses
What are the phases of contrast enhancement? And time
(Non enhanced CT)
Early arterial - 20 sec (or 0 sec after bolus)
Late arterial- 40 sec (or 20 sec after bolus)
Hepatic- 80 sec (or 60 sec after bolus)
Nephrogenic- 100 sec (or 80 sec after bolus)
Delayed- 6 min
Early arterial phase is useful for the diagnosis of
Aorta dissection
Arterial bleeding
Late arterial phase is useful for the diagnosis of
Liver HCC
Pancreas AC
Insulinoma
Bowel ischemia
Hepatic phase is useful for the diagnosis of
Hypovascular liver lesions
Nephrogenic phase is useful for the diagnosis of
Renal cell carcinoma
Delayed phase is useful for the diagnosis of
Cholangiocarcinoma Fibrotic metastasis Breast cancer Transitional cell carcinoma Liver Hemangioma
In which parients will we have increased risk for Post Contrast Acute Kidney Injury?
GFR < 30 mL/min
Impaired kidney function
Multiple contrast admin.
We should perform GFR test 7 days after the contrast CT for which patients?
GFR < 60 mL/min
Age > 70
Other diseases (kidney failure…)
Which patient are at risk for lactate acidosis post contrast CT?
Patients who take Metformin for their DM-II
Which patients can continue to take Metformin normally before contrast CT?
GFR > 45 mL/min
Effective dose of CT is ___ mSV
5-20 mSV
On HRCT, what is the thickness of the slice
< 1 mm
Which Imaging modality is used in case of pelvic soft tissue imaging?
MRI
