The document discusses quality assurance in patient immobilization and positioning for radiation therapy, outlining various immobilization devices and methods used to precisely position patients to maximize dose to cancerous tissues while sparing normal tissues and ensuring reproducibility from simulation to treatment. It analyzes sources of error in positioning and the benefits of immobilization devices in reducing errors and improving accuracy for conformal radiation therapies.

1. QUALITY ASSURANCE IN IMMOBILIZATION
AND
PATIENT POSITIONING FOR RADIATION THERAPY
RAJIV GANDHI CANCER INSTITUTE &
RESEARCH CENTRE- DELHI
Akhil Chaudhary , Vishvendra Gaur ,
R.S.Bedi , S. Mitra , S.N.Sinha ,G.S.Wadhawan ,

2. THE CLINICAL AIM OF
RADIOTHERAPY…
 To maximize the “therapeutic index” by:
• Delivering lethal doses of radiation to
cancerous cells (so increasing chances of
survival) ,while
• Sparing normal tissue (so reducing side-
effects and increasing quality of life)
 This is achieved by precisely shaping and
directing the radiation beams based on
information from medical images.

3. WHAT IS PATIENT POSITIONING?
 a reproducible localization of the patient with
the use of a device onto which a patient lays
a specific part of their anatomy
 designed to guide the patient into the original
simulation position for radiation beam
administration.

4. WHAT IS
PATIENT IMMOBILIZATION?
 A reproducible localization of the patient with a device into
which the patient is locked, to aid in the restriction of
anatomical movement
 Why use positioning and immobilization
devices?
• Increase target accuracy
• Easy to use
• Quick to setup
• Comfortable for patient
• Durable enough to withstand an entire course of treatment

5. HISTORY OF PATIENT POSITIONING
 sand bags
 Tape
 bite block
 plaster casts
 “home-made devices”

6. CURRENT METHODS FOR POSITIONING
AND IMMOBILIZATION
Thermoplastic
 •Treatment chair  Positioning aids
mask of the head Head rest
•Belly boards •Pelvic boards •Extremities

7. AIO INDEXED IMMOBILIZATION
• Exact reproducibility of
the patient’s position in
imaging and therapy.
• High level of patient
comfort.
• Precise immobilization
of all body regions.
• Reduction of patient set-
up time.
• Reduction of risk of
random and systematic
errors.

8. CONSIDERATIONS
FOR SELECTING A DEVICE
 Cost
• Value for money.
 Convenience
• If its not convenient it will just gather dust on the
shelf.
 Accuracy
• The identical position must be reproduced day to
day.

9. CONSIDERATIONS
FOR SELECTING A DEVICE
 Speed
• Minimal time should be required to get the device
ready for patient use.
 Compatibility
 devices should be constructed of
 radio-translucent materials to avoid image artifact
or anatomical obstructions
 Attenuation
• Beam integrity must be maintained.

10. CONSIDERATIONS
FOR SELECTING A DEVICE
 Durability
• Devices must be able to
withstand repeated use.
 Positioning aids:
• Silverman
• shoulder retractors
• bite bock
• foam wedge
• incline board
• prone pillow

11. BENEFITS OF POSITIONING AIDS
 work with positioning devices to increase
stability, comfort and reproducibility.
LIMITATIONS OF POSITIONING AIDS:
• During immobilization, patients still have freedom of
movement.

12. TEN SYSTEMS
 skeletal system Verbal statements to
 circulatory system immobilize patients:
 Please do not move.
 digestive system
 Don’t wiggle, now.
 respiratory system  Lay heavy, become as one
 urinary system with the table.
 reproductive system  Be placid, man.
 nervous system
 muscular system
 endocrine system
 integumentary system

13. PATIENT POSITIONING, FIXATION AND
REPRODUCIBILITY OF SETUP
 Whether you are doing conventional radiotherapy, 3D
conformal or IMRT treatments – accurate, reproducible
positioning and rigid fixation are important factors for precise
dose delivery to the treatment portals.
 Thermoplastic shells offers a reliable method for accurate
positioning and immobilization.
 There are three essential components required for making
these shells:
• (i) Base plate: made up of acrylic material or carbon fibre.
Available for head and neck cases, chest, pelvic regions.
• (ii) Neck supports: foam type poly urethane material or silver
man standard supports.
• (iii) Thermoplastic masks.

14. ABDOMEN / PELVIS POSITIONING AND
FIXATION
• Position the patient (prone or supine)
onto the board. Do an initial visual
check to make sure the patient is
centered as accurately as possible on
the board, adjust patient if needed.
• Once positioning is ok marked the
patient to the lateral and midline.
• These marks will now serve as daily
repositioning marks in the treatment
room.
• Avoid compressing the skin as much as
possible.
• To avoid shrinkage cool the casts
completely, make sure the heat is out
of cast before removing from the
patient.
• Use laser to align the patient, ensuring
identical repositioning from simulation.

15. BENEFITS OF THERMOPLASTIC MASKS
 Economical
 Disposable
 can re-use PVC frame (with re-loadable systems)
 markers can be placed on the mask rather than the
patient.
 reproducible positioning is achieved.

16. CHALLENGES OF
THE HIP AND PELVIS REGION
 cylindrical shape of this anatomical region
 rotation of the body axis
 cast fabrication is technique sensitive
 choosing supine or prone positioning
LIMITATIONS OF THERMOPLASTIC
IMMOBILIZATION
 thermoplastic sheets are expensive
 technique sensitive application requires hands-on
training by vendor
 must have a large water bath.

17. ERRORS
 Localization Error:
 results from the failure to appreciate the full extent of
the disease or to design adequate treatment fields
 Immobilization Error:
 occurs as a result of displacement of the treatment
fields relative to the intended treatment volume.

18. INTEGRATED
POSITIONING AND IMMOBILIZATION
 combining several
positioning or
immobilization devices
to adequately position
a patient.

19. VAC-LOK
• A complete vacuum is
drawn through the quick-
release valve, cushion
becomes a rigid and
comfortable mold, offering
accurate reproducibility
throughout the course of
simulation and treatment.
• Made up of Nylon-
urethane material, can be
cleaned and reused.

20. BENEFITS OF VAC-LOK LIMITATIONS OF VAC-LOK
 cost-effective  vacuum or wall suction is
 re-usable required
 quick to set up  storage space is required
 full range of sizes  may puncture or develop
 longevity is dependent on leaks
care and use.  can not “cut-away” into the
cushion.
VAC-LOK

21. LASERS
• Laser lines reference
the radiation beam
parameters to the
patient’s anatomy.
• Repositioning the
patient from simulation
room to the treatment.
• For the daily setup in
the treatment room.

22. INDEXED IMMOBILIZATION™
 The ability to provide a
method of indexing, and
locking down, a
positioning device to
multiple points along the
top of a
treatment, simulator or
CT tabletop.

23. FEATURES OF
INDEXED IMMOBILIZATION
 close tolerance repositioning
 improved target accuracy
 increased patient through-put
 quick and accurate patient set-up
 reliable repeatability
 maximized clinical efficiency

24. BENEFITS OF
INDEXED IMMOBILIZATION
 same spatial reference between simulation and treatment
 same spatial reference between treatments
 standardization of the spatial relationship for all couches and
treatment tables in the department, including CT couches
 improved target accuracy
 reduced patient set-up time resulting in increased patient through-
put.

25. QUALITY ASSURANCE ACHIEVEMENT
 comfortable to minimize movement
 reproducible for the treatment plan
 Portal Identification.
 CONSISTENCY:
• Consistency in patient positioning and
immobilization from treatment planning to
simulation, and from simulation to treatment must
be maintained.

26. ACUITY( SIMULATION)

27. RESULTS
 prescription of target dose
 physical dosimetry of the beam
 planning of individual treatment
 precision of daily dose delivery

28. PATIENT FLOW CHART IN RT
Immobilization setup CT Simulation/Imaging Target
Organ Delineation Specify Objective Function
Optimization Leaf Sequence Generation Dose
Distribution Calculation Plan Evaluation Plan
Implementation MLC Controller EPID portal
Treatment.

29. WHAT’S IN THE FUTURE FOR
POSITIONING AND IMMOBILIZATION?
 CT scanner:
 more immobilization devices and increased target
accuracy.
 more “upgrades”
 3D treatment planning systems will increase the
need for accurate patient positioning and
immobilization.
 more centers utilizing:
 Conformal and/or fractionated radiotherapy.
 Stereotactic Radiosurgery(SRS).
 Intensity Modulated Radiation Therapy.

30. RADIATION ONCOLOGY
CONFORMAL BEAM SHAPING

31. LIMITATIONS OF
POSITIONING METHODS
Method Accuracy Limit
laser alignment 2.0 – 2.5mm
using skin marks
radiographic alignment 1.0 – 2.0mm
using anatomy
radiographic alignment <1.0mm
using point markers
mechanical positioning of <0.25mm
indexed patient
visual image alignment ~1.0mm

32. CONCLUSION
 Currently most IMRT/3D-CRT/stereotactic
radiotherapy, approaches have increased the time
and efforts required by radiation oncologists
,medical physicist , dosimetrist and radiation
therapy technologist In precise delivery of radiation
dose .
 Actually in radiation therapy execution in hands of
radiotherapy technologists resulting –
• Safety of normal organs
• Proper coverage of target volume
• Precise delivery of dose
• Decreased toxicity in grade and size
• Improved overall survival and quality of life

33. CONT….
• Immobilization improves : the reproducibility of
patient positioning during conventional/Conformal/IMRT
Radiation therapy.
• Purpose : to determine the magnitude of patient
positioning errors and to assess the impact of
immobilization on these errors.
• The record of 22 patients , in our department whose
immobilization was prepared in open environment (Mould
room) were compared with rigid immobilization prepared in
closed environment (simulator room) and it was observed
there is 2 to 5 mm shift in open Vs closed environment
setup.

34. CONT….
• Portal films of patients: treated at both facilities
were subsequently review and deviation each portal
from the simulation film was determined.
• Simulation-to-Treatment variability &
Treatment-to-Treatment variability: was 2-
5mm along the patient treated with open vs closed
immobilization.

35. CONT….
• The use of immobilization devices significantly
reduces errors in patient positioning , potentially
permitting the use of smaller treatment volumes.
• Immobilization should be a component of
conformal radiation therapy programs for
cervix carcinoma to achieve the integrity of
treatment plan.