imaging

Question 1

radiography definition

Answer 1

imaging technique using x-rays and gamma rays to view the internal form of an object

Question 2

which direction are x rays taken + why?

Answer 2

posterior to anterior

x rays give better definition and a better view of the heart

Question 3

explain appearance of image

Answer 3

bones contain a lot of calcium, absorb a lot of x-rays, this reduces the amount of x ray detected so the bones appear lighter on radiograph

fundus full of air is dark, as x rays can pass through easily

Question 4

function of x rays

Answer 4

can detect kidney or gall stones

can detect changes in lungs

bone fractures

can detect bowel obstructions

Question 5

x-ray attenuation concept

Answer 5

the intensity of the x-ray beam decreases the farther it penetrates into matter

depends upon the absorption coefficient of the material of the depth of penetration

Question 6

principle of radiology

Answer 6

the notion that radiation is absorbed and scattered as it passes through an object

if there are variations in thickness or density in an object, the more or less radiation passes through and affects the film exposure

Question 7

what is computed tomography?

Answer 7

slices of the body obtained from large series of 2D x rays taken from different directions

an image is then reconstructed

Question 8

ct image apperance

Answer 8

same as X ray- dense structures are white and air is black

Question 9

what plane are the images normally in?

Answer 9

transverse

looking at the image from the feet, patient facing upwards

Question 10

CT uses

Answer 10

located oedemas, fibrosis, angiography

Question 11

what is a radio contrast CT?

Answer 11

CT using a radiocontrast that can highlight structures that would otherwise be difficult to differentiate from the surroundings

Question 12

what contrast normally used in CT?

Answer 12

iodine based

Question 13

what is MRI?

Answer 13

Magnetic Resonance Imaging

uses strong magnetic field gradients and radio waves

Question 14

common use for MRI

Answer 14

Staging of cancers, investigative tool

good visualisation of posterior cranial fossa, containing brainstem and cerebellum

Question 15

contrast agents for MRI+ how it appears

Answer 15

often based on chelates of gadolinium

bright

Question 16

is MRI safe?

Answer 16

much safer than CT as no ionising radiation

Question 17

two different types of MRI image

Answer 17

T1 weighted and T2 weighted

Question 18

T1 image

Answer 18

bright- fat, melanin, blood, proteinaceous fluids

dark- iron, water, air, bone, collagen, most tumours

Question 19

T2 image

Answer 19

bright- water, oedema, fat, blood, most tumours

dark- air, bone, chronic blood, acute blood

Question 20

what is ultrasound?

Answer 20

transmit a high frequency 1-5 megahertz sound pulse into the body using a probe

can then calculate the distance to the organ thanks to the time taken for the ultrasound wave to reflect back to the transmitter

Question 21

where are the waves refleced?

Answer 21

boundaries between tissues

the bigger the boundary the stronger the echo

Question 22

ultrasound use

Answer 22

baby scan, destroying kidney and gall stones