Digital Subtraction Angiography
Digital Subtraction Angiography (DSA) - answer is a fluoroscopic technique used
extensively in interventional radiology for visualizing blood vessels.
what is "subtracted" in DSA images? - answer Radiopaque structures such as bones
are eliminated ("subtracted") digitally from the image, thus allowing for an accurate
depiction of the blood vessels.
3 subareas of DSA are: - answer- Image Formation
- Road mapping
- Patient Dose
There are two methods for image formation: - answer- Temporal Subtraction
- Energy Subtraction
temporal Subtraction - answer Image obtained at one time is subtracted from an image
obtained at a later time
Energy Subtraction - answerUses two alternating x-ray beams operating at two different
energy levels-subtracted image results from differences in photoelectric absorption in
contrast vs. non-contrast status of subject
the two most common temporal subtraction are: - answer- Mask Mode
- Time Interval Difference (TID) Mode
Mask Mode - answer- The patient is positioned under normal fluoroscopic control to
ensure that the region of anatomy under investigation is within the field of view.
- Mask mode results in successive subtraction images of contrast-filled vessels.
use of power injector on mask mode - answer- Venous -deliver 30 to 50mL of contrast
material at the rate of approximately 15 to 20mL/s
- Arterial -deliver 10 to 25mL of diluted contrast material at 10 to 12mL/s
What happens when the imaging system is changed from the fluoroscopic mode to the
digital fluoroscopic (DF) mode? - answerincrease in x-ray tube current of 20 to 100
times the fluoroscopic mode and the activation of a program of pulse image acquisition
process of mask mode - answer- Injector is fired, and after a delay of 4 to 10s, before
the bolus of contrast medium reaches the anatomic site, an initial x-ray pulsed exposure
is made.
- The image obtained is stored in primary memory and is displayed on video monitor
Digital Subtraction Angiography (DSA) - answer is a fluoroscopic technique used
extensively in interventional radiology for visualizing blood vessels.
what is "subtracted" in DSA images? - answer Radiopaque structures such as bones
are eliminated ("subtracted") digitally from the image, thus allowing for an accurate
depiction of the blood vessels.
3 subareas of DSA are: - answer- Image Formation
- Road mapping
- Patient Dose
There are two methods for image formation: - answer- Temporal Subtraction
- Energy Subtraction
temporal Subtraction - answer Image obtained at one time is subtracted from an image
obtained at a later time
Energy Subtraction - answerUses two alternating x-ray beams operating at two different
energy levels-subtracted image results from differences in photoelectric absorption in
contrast vs. non-contrast status of subject
the two most common temporal subtraction are: - answer- Mask Mode
- Time Interval Difference (TID) Mode
Mask Mode - answer- The patient is positioned under normal fluoroscopic control to
ensure that the region of anatomy under investigation is within the field of view.
- Mask mode results in successive subtraction images of contrast-filled vessels.
use of power injector on mask mode - answer- Venous -deliver 30 to 50mL of contrast
material at the rate of approximately 15 to 20mL/s
- Arterial -deliver 10 to 25mL of diluted contrast material at 10 to 12mL/s
What happens when the imaging system is changed from the fluoroscopic mode to the
digital fluoroscopic (DF) mode? - answerincrease in x-ray tube current of 20 to 100
times the fluoroscopic mode and the activation of a program of pulse image acquisition
process of mask mode - answer- Injector is fired, and after a delay of 4 to 10s, before
the bolus of contrast medium reaches the anatomic site, an initial x-ray pulsed exposure
is made.
- The image obtained is stored in primary memory and is displayed on video monitor
