Part 7: Contours

term. Contours

def.

devices that give a cross-sectional outline

of the patient’s body contour

at the central axis

in the transverse plane

At what point during the Conventional Simulation process is a contour taken?

At the end of a conventional sim

term. Contours

def.

devices that give a cross-sectional outline

of the patient’s body contour

at the central axis

in the transverse plane

At what point during the Conventional Simulation process is a contour taken?

At the end of a conventional sim

A contour outlining the patient’s body shape in the transverse plane.

What is the purpose of a contour?

having the body shape in the computer

↑ dosimetric accuracy

Since the body shape (contour) can change radically outside of the CA

What are areas that are frequently contoured? (specific)

chest, abdomen, pelvis

and H&N areas

What areas require more than one contour?

Areas where the body thickness varies significantly along the y (sagittal) axis

A contour must include:

(fyi: solder wire type)

1. a line representing the table top

2. Important bony landmarks

3. Beam entry points if available (use lasers)

Why must a contour include “a line representing the table top”?

The line can be used as a reference for beam angles

True or False: If a patient loses significant amount of weight a new contour must be made.

True

1.If a patient loses significant amount of weight, besides a new contour. Would you need to reconstruct tx accessories such as a tissue compensator, mask, etc.? Why?

2.Would you need to recalculate the MUs? Why?

1.Yes: You don’t want a source to mask distance, you want a source to skin distance.

2.Yes: MUs are calculated with patient’s body thickness in mind.

List all contour devices

1. Solder wire (or lead wire embedded in rubber or plastic)

2. Thermoplastic Strip or Tube

3. CT

4. MRI

5. Ultrasound

thermoplastic strip or tube

1. Which contour device is not commonly used?

2. Which contour device is the simplest and easiest?

3. What contour device is the most accurate?

4. What contour device is the least accurate?

5. What contour device is the most commonly used for conventional sim?

6. Which contour device(s) is/are reusable?

1. MRI

2. Solder Wire

3. CT

4. Solder Wire

5. Solder Wire

6. Solder wire & thermoplastic strip or tube

Which company creates the thermoplastic strip or tube?

W.R. Aquaplast Company

Why is MRI not commonly used as a body contour device?

It does not scale too well. It distorts shapes.

True or False: Utrasound image quality is better than CT quality.

False. It is not as good, but it is quickly imporving