Radiology and contrast agents Flashcards
1
Q
how are radiographs produced
A
- X-rays transmitted through a patient
- X-rays projected through body onto a detector
- image formed based on which rays pass through ad are deteted versus those that are absorbed or scattered in patient and not detected
2
Q
digital radiography and EOS imaging
A
- X-rays strike sensors that convert the signals generated into digital information which is transmitted and converted into an image displayed on a computer
- in DR the sensors are shaped like a plate
- in EOS a linear sensor vertically scans the patient
3
Q
examples of diseases diagnosed by plain radiography
A
- various types of arthritis
- pneumonia
- bone tumours
- fractures
- congenital skeletal abnormalities
4
Q
applications of low energy projectional radiography
A
- mammography for breast cancer evaluation
- DXA for osteoporosis evaluation
5
Q
fluoroscopy and angiography
A
- fluorescent screen and image intensifier tube connected to a closed circuit television system
- allows real-time imaging of structures in motion or augmented with a radiocontrast agent
6
Q
why are radiocontrast agents used
A
- to delineate anatomy and functioning of blood vessels, genitourinary system or the gastrointestinal tract
- they strongly absorb or scatter X-rays and in conjunction with the real-time imaging allow demonstration of dynamic processes such as peristalsis in the GI tract or blood flow in arteries and veins
7
Q
barium sulphate (BaSO4) as a radiocontrast agent
A
- given orally or rectally
- evaluation of the GI tract
8
Q
iodine as a radiocontrast agent
A
- given by oral, rectal, vaginal, intra-arterial or intravenous routes
- concentrated in abnormal areas more or less than in normal tissues and make abnormalities like tumours and cysts more conspicuous
9
Q
gases as contrast agents
A
- air for the GI system
- carbon dioxide in the venous system
- the agent attenuates the X-ray radiation less than surrounding tissues
10
Q
computed tomography (CT)
A
- uses X- rays in conjunction with computing algorithms to image the body
- X-ray tube opposite an X-ray detector in a ring-shaped apparatus rotates around the patient producing cross-sectional images
- radiocontrasts often use for enhanced delineation of anatomy
- detects more subtle variations in attenuation of X-rays than radiographs
11
Q
examples of conditions diagnosed using CT
A
- cerebral haemmorhage
- pulmonary embolism
- aortic dissection
- appendicitis
- diverticulitis
- obstructing kidney stones
12
Q
nuclear medicine
A
- administration of radiopharmaceuticals labelled with radioactive tracer into the patient
- substances consist of material with an affinity for specific body tissues
- anatomical detail is limited
- useful in displaying physiological function so can measure excretory function of kidneys, iodine-concentrating ability of thyroid, blood flow to heart muscle
- gamma camera and PET scanner detect radiation emitted by tracer in body and with computer processing display it as an axial, coronal or sagittal image as SPECT or PET
- most images can be fused with CT scan so physiological information can be overlaid with anatomical structures to improve diagnostic accuracy
12
Q
commonly used radioactive tracers
A
- technetium-99m
- iodine-123
- iodine-131
- gallium-67
- indium-111
- thallium-201
- 18F-fluorodeoxyglucose (18F-FDG)
13
Q
positron emission tomography (PET)
A
- positrons annihilate to produce two opposite travelling gamma rays to be detected coincidentally
- radioactive, biologically active substance (often 18F-FDG) is injected into patient and radiation emitted is detected to produce multi-planar images
- more metabolically active tissues such as cancer cells concentrate the active substance more than normal tissues so can be imaged
- PET images can be combined with CT imaging to improve diagnostic accuracy
14
Q
interventional radiology
A
- minimally invasive procedures are performed using image guidance for diagnostic (eg. angiogram) or treatment (eg. angioplasty) purposes
- often performed with patient fully awake with little or no sedation
- primary instruments used are needles and catheters
- images provide maps that allow the clinician to guide the instruments through the body to the areas containing disease
- peripheral interventions can reduce infection rates, recovery times and hospital stays