Part 14: Beam Direction Devices

term. Beam Direction Devices

def. Devices that assist in patient alignment

Beam Direction Devices

List:

1. Field light, ODI/ Rangefinder & Crosshair

2. Lasers

3. Mechanical pointers

4. Graticule/BB tray

term. Geometric Miss

def. A result of improper beam direction. As a result of:

1. improper use of beam alignment devices

2. inaccurate QI

RTTs and patients should be instructed not to look into the lasers because it can cause damage to ___

The retina

Why are lasers recessed into the wall?

To minimize being bumped out of alignment

Material used in lasers

Helium Neon (HeNe) Lasers

Lasers color

1. Red or

2. Green

Which laser color is shaper? Why?

Green due to having a shorter wavelength = less scatter

1.___ demonstrates beam exit point

2.___ demonstrates beam entry point

1. backpointer

2. crosshair

____ laser aligns the patient with the gantry axis of rotation

Sagittal

Lighting for tx rooms

1. standard or

2. dimmed

Mechanical Pointers:

1. ___: determines beam entrance point

2. ___: determines beam exit point

1. frontpointer

2. backpointer

Can you still set up a field if the field light burns out?

Yes if tx is simple. Use mechanical front pointer.

Give all names for this.

1. reticule

2. BB tray

3.Fiducial Plate

4.Graticule

What is a Graticule?

A tray with BBs 1 cm apart in the x-axis and y-axis.

Helps determine magnification and distance.

Plastic trays that are embedded with lead markers (BBs) at regular intervals (often 1cm apart) for easy determination of distance and magnification.

Fiducial Plate