ABC

Question 1

Issues caused by respiratory motion

Answer 1

• Causes displacement of tumour location
  
  • 12-16 respiratory cycles every minute
  • SI direction up to 2-2.5cms
  • Ant-post and lat directions 5mm to 1cm

Causes difficulty localising tumour - overdose normal tissue, underdose tumour

Question 2

How can motion be controlled

Answer 2

Motion compensation: Respiratoy gating and tumour tracking
Motion Suppression: Abdominal compression and deep inspiration breath hold

Question 3

Respiratory gating

Answer 3

Imaging and delivery of RT during a portion of the breathing cycle or “gate”

Question 4

Tumour tracking

Answer 4

radiation beam follows the tumours changing position

Question 5

Abdominal compression

Answer 5

use of compression plate to limit breathing. Originally designed for SBRT of lung and liver. Limits air intake of patient, therefore reducing amount the diaphragm can move. Smaller margins achievable

Question 6

Abdominal compression advantages

Answer 6

simplicity, minimal technological devices, easy to use, reduce respiratory motion, reusable

Question 7

Abdominal compression disadvantages

Answer 7

increased setup time, slight discomfort, difficult for patients with claustrophobia

Question 8

Deep inspiration breath hold

Answer 8

assist patient in holding his own breath at a pre-determined position. Commonly used for LT breast and lung tumours

Question 9

ELEKTA - ACTIVE BREATHING CONTROL (ABC)

Answer 9

• Apparatus can suspend breathing at any predetermined position
  
  • Used to avoid dose to healthy lung and heart
  • During a deep breath, the heart moves away from breast and chest wall, reducing the amount of heart tissue within the treatment area

Question 10

ABC eligibility criteria

Answer 10

Able to follow prompts from staff
Able to establish a reproduceable breathing pattern
Able to hold breath for a min of 20seconds - multiple times

Question 11

ABC process

Answer 11

1. mouthpiece placed in patient’s mouth
2. Hooked up to ABC machine
3. Continously monitors lung volume
4. When lung volume is at the ideal level, the valve on the mouthpiece is closed of (usually set at 70-80% of maximum inspiration and prevents the patient from inhaling and exhaling)
   5.Radiation beam is turned on and once beam is delivered, the valve re-opens

Question 12

Components of ABC

Answer 12

• Spirometer
• Tubing
• Filter
• Mouth piece
• Nose peg
• Patient control switch

Question 13

Advantages of ABC

Answer 13

• reproduceable breath holds
• reduces tumour motion and cardiac treatment volumes
• Allows a reduction in margin sizes
  can treat more complex volumes

Question 14

ABC Disadvantages

Answer 14

-more invasive
- patient needs to hold breath for min 15sec
- requires verbal training by therapist

Question 15

VARIAN RPM (real position management)

Answer 15

• Audio-visual feedback option used to assist patient in holding own breath at a pre-determined position
  Patient instructed to breathe when beam turns off

Question 16

Advantages and disadvantages of VARIAN RPM

Answer 16

• Less invasive
• Reduces tumour motion and cardiac treatment volumes
  Disadvantages:
  Difficult for many elderky and frail patients or those with pulmonary disease

Question 17

What to discuss during patient education:

Answer 17

• Familiarise patient with equipment
  
  • Taking a lung volume level to establish an immune breath threshold
  • Breathing routine reharsed to ensure patient can comfortably hold breath for required time
  • Patient returns next day for planning CT scan
    General health and side effect disccussion

Question 18

RPM method

Answer 18

Free breathing breath hold
Utilises an infra-red camera and marker block placed on the patient to track movement of their chest and breathing
Abches monitors breathing pattern
Patient is instructed to hold the breath at a specified breathing position. By viewing a breathing level indicator

Question 19

Components of VARIAN RPM

Answer 19

Camera, marker block

Question 20

Infra-red systems

Answer 20

camera sends signals, reflected off the markers, markers learn the patients breathing pattern

Question 21

Components of abdominal compression

Answer 21

Stereotactc body frame
pressure plate
screw