Introduction To Imaging

Question 1

X-ray

Answer 1

An electromagnetic pocket of energy with an exremely short wavelength between 0.1-10 nanometres.

Question 2

X-ray generation

Answer 2

1. Increase in filament voltage.
2. Large increase in tube current.
3. Accelerates high speed electrons from high temperature cathode within vacuum.
4. Electrons move towards tungsten target anode. Anode rotates to dissipate heat generated.
5. X-ray generated within tungsten anode and beam is directed to patient.
6. Emulsion contains silver halide; clumps form after exposure to light generated on luminescent screens.
   X-rays are generated by interactions of the accelerated electrons with electrons of tungsten nuclei within tube anode. Intensity of x-rays varies depending on tube current? Atomic number of target and tube voltage.

Question 3

Attenuation

Answer 3

The process by which radiation loses its power as it travels through matter and interacts with it. The attenuation co-efficient increases with atomic number, density and thickness.
E.g air appears black and has a low attenuation co-efficient. Contrast agents/metal implants appear white and have a high attenuation co-efficient.

Question 4

Ultrasound

Answer 4

Utilises high frequency sound pulses (1-20 MHz) to capture a pressure wave producing an image. An increase in Hz gives greater detail bu decreases depth penetration. Strengths include dynamic test, cheap, portable. Weakness is that it is operator dependant.

Question 5

Fluoroscopy

Answer 5

Uses x-rays to obtaon real time moving images of the interior of an object. E.g. barium studies. It has few strengths so is declining in use. It can cause bowel disturbance, colonic perforation at enema, possible leak leading to barium peritonitis and aspiration.

Question 6

Computed tomography CT

Answer 6

Rotating X-ray tube that produces multiple beams on a single axis of rotation resulting in an axial image via digital geometry processing.
Strengths; defines bony detail, used in trauma and cancer staging/response and guidance.
Weaknesses; exposure to ionising radiation.

Question 7

Iodinated contrast media

Answer 7

Enhances the visibilty of vascular structures and organs during radiographic procedures. May be given orally or IV. However it can lead to kidney failure.

Question 8

Hazards of ionising radiation

Answer 8

Ionising means it will ionise a neutral atom/molecule leaving a charge. Radiation is the process of emitting energy in the form of either particles or waves. It can cause cell damage which may be repaired, lead to cell death or transformation.