Diagnostic Imaging Terminology

Flashcard highlighting the key term 'Heel Effect' from the diagnostic imaging lecture notes.

when radiographing a thorax a ___kvp/___mAs technique should be used

high - low

as a general rule, where should markers be placed when taking radiographs

either on the lateral or cranial aspect

where do you center the beam for a lateral thoracic radiograph 

caudal border of the scapula/over the heart 

how can you tell if a lateral thoracic radiograph was taken on inspiration

there will be a space between the cardiac silhouette and the diaphragm

why do you want to take abdominal radiographs on expiration

the diaphragm moves cranially, allowing the maximum amount of space for the contents of the abdomen

what are the landmarks for a carpal radiograph 

distal 1/3 of the radius/ulna and proximal 1/3 of the metacarpals 

do you want a high or low kVp for abdominal radiographs

medium - low kVp

why do you want medium - low kVp for abdominal radiographs

because you need a long scale of contrast so you can see the abdominal organs

what articact is commonly seen on ultrasound when scanning the liver/diaphragm interface 

mirror image artifact 

what echogenicity is the urinary bladder and what color does that appear to be on a standard b mode image

anechoic, black

what is the doppler mode used to visualize on ultrasound

blood flow and velocity

what is the heel effect

The heel effect refers to the variation in X-ray intensity that occurs due to the angle of the X-ray beam hitting the image receptor, resulting in differences in exposure across the image.

what is the penumbra effect

as the focal spot becomes larger, the image becomes fuzzier and less sharp

how can the penumbra effect be applied in the x ray room

to achieve a very sharp, detailed image, you will want to use a small focal spot,.

how can you achieve a small focal spot 

you will need to use a small filament and focusing cup. this means the machine would need to be set at 100 mA. 

which grid would be more efficient in absorbing scatter radiation - one with a grid ratio of 12:1 or 4:1

12:1 the taller the lead strips, the more scatter radiation the grid will absorb

what is santes rule

(2 x thickness in cm) + ffd/sid + grid factor

which imaging modality only “sees” hydrogen atoms 

MRI

where should you center the beam for a large rabbit lateral abdominal radiograph

center caudal to the last rib