This document discusses various sources of uncertainty and errors in radiation therapy delivery due to patient and target motion. It describes advances in imaging guidance and motion management techniques like 4D imaging, respiratory gating, abdominal compression, and deep inspiration breath hold to minimize the effects of respiratory motion. Real-time tracking methods like RPM and ExacTrac systems are highlighted which allow continuous monitoring of tumor position throughout treatment. Managing respiratory motion remains an important area of focus to ensure accurate radiation delivery.

1. Dr.V.Lokesh M.D.
Professor & HOD , Dept of Radiation Oncology
Kidwai Memorial Institute of Oncology
AROI KS Chapter2021

2. Introduction
 Aim– Irradiate Tumour with minimal radiation dose to uninvolved
normal tissue
Era - common practice
 Hypo fractionated regimens
 Single Ablative doses of radiation
 Reirraditon
 Sophisticated RT Techniques
 IMRT/SRS/SRT/SABR – under IG
 Target Motion and normal tissue movements – confounding factor
 Currently Quality RT – demands adequacy of proper equipment, proper
SOPs, trained staff (RO/RP/RTT) -- > to ensure setup accuracy - less
than few millimeters and safe delivery

3. patient positioning and immobilization
 Often the weakest link in the chain of treatment
planning
 Corrected by :
 Appropriate - Mechanical immobilization
 Patient
 Education
 Psychological preparation
 Stabilization of Target etc.

4. Uncertanites
 Target delineation: Clinical/CT/MR/PET/Others
 Organ motion:
 Respiration
 Hear beat & Vascular changes
 Organs – digestive / excretory / gas – change in size and shape
 Buoyancy – Floating organs (brain , spinal cord)
 Skin / Surface marks
 Repositioning
 Patient motion :
 Skeletal muscle – voluntary /involuntary movements
 Anxiety
 Pain
 Neurological disorders / dimentia

5. Movements associate with Respiration
 Affects Multiple Organs
 Liver
 Lungs
 Pancreas
 Kidneys
 Retroperitoneum
 Thoracic wall
 Mediastinal region

8. respiratory motion is just one potential source of error in
radiotherapy :
 Other important Contribution for errors are eg: Lung & Breast
cancer
 Large inter-physician variations in GTV & CTV
 Setup errors
The dosimetric consequences of these variations are almost
an order of magnitude larger than those caused by
respiration-induced motion
 Respiratory motion varies
 from day to day,
 tumor and normal tissues can shrink, grow, and shift in response to
radiation therapy and potentially to other concomitant therapies.
 Machine related – issues (CT sim / LA / Couch /planning System –
related issues also have an impact and QA – dosimetric issues.

9. Methods of limiting respiratory
motion
a. Abdominal compression
b. Respiratory gated RT : involves turning the beam ON
during position of respiratory cycle
a. RPM
b. ABC

10. Advances in IGRT – Addressing
Motion Issues
a) Image guided Target / Tissue delineation
1. PET
 18 FDG
 Non FDG Pet Miso
2. MRI
3. SPECT
b) 4D Imaging and Motion Management
c) In room Imaging
a. Ultrasound
b. Video surface imaging
c. Planar imaging : EPID / KV imaging devises
d. Fluroscopic – Fidutial based / non fidutial based
e. Volumetric Imaging : KV/Mv CBCT
d) MRI
e) Radiofrequency Localization System – Transponders
f) 4D imaging and motion management – 2D CBCT & fluoroscopic imaging
g) Tumour Tracking

11. Respiration induced Organ Motion
 A significant problem in RT
 T – located in Thorax & upper Abdomen
 Ignored :
 Substantial imaging artefact In treatment planning image
 Inaccurate Target delineation
 Unnecessary large target volume

12. Static In motion
4D

13. Gating Strategy
 Regardless of the gating system
 patient respiration > divided - ten discrete time points (phases) per
period.
 used to assess tumor motion and determine a gating strategy
 0% phase corresponds to maximum inspiration
 50% phase corresponds to maximum expiration
 On average- most patients spend more time in expiration than
they do in inspiration, which creates a beneficial scenario for
respiratory gating around expiration

14.  Respiratorty motion is arrested > no respiration-
induced tumor motion :: large window to treat the
tumor with limited motion
 candidate for deep inspiration breath hold (DIBH)-
hold their breath for an extended amount of time,
creating a large window to treat the tumor with little
TARGET motion

15. Methods that are used in the management of
respiratory motion in radiation oncology
 Motion-encompassing methods
 respiratory gated techniques
 breath-hold techniques
 forced shallow-breathing methods
 respiration-synchronized techniques

16. SYMMETRY
Symmetry CBCT done on couch for verification Symmetry CBCT pushed to TPS for planning

17. DIBH
DIBH & Free breathing planning CT scan superimposed to see for the
difference in the distance between the heart & chest wall

18. DIBH
Treatment set up
Position
verification by
EPID images
Treatment
delivery in
DIBH

19. Active Breath Controller (ABC)
 Elekta ABC system- helps in treating patients in deep
breath hold position.
 It consists following components
1. Mouth piece
2. Spirometer
3. ABC control unit
4. Patient viewing monitor
5. Emergency button
6. Linac control Module.

20. Active Breath Controller (ABC)conti..
Indications for using ABC:
1. Carcinoma of Left breast ( conserved breast/ Chest wall)
2. Carcinoma lung- SBRT/ Radical RT for primary tumor
3. Carcinoma Liver
4. Carcinoma Pancreas
5. Mediastinal tumors
6. Metastatic tumor lesions in liver and lung.

21. Clinically suitable patient
Trained with spirometer for 3 days, patient is instrcuted to hold in deep inspiration
Patient is positioned in treatment position in mould room, the mouth piece is kept inside the
mouth of the patient, connected to the ABC system. Patient is asked to take the deep breath and
hold, the duration of breath hold and the volume is noted. The threshold levels are set.
Similarly patient is trained for 3 days
Patient is simulated in both free breathing (CT-1) and deep breath hold (CT-2), the external
fiducials are kept on body at the intersection of the orthogonal Lasers in DIBH position only.
The target structures and OARs are delineated on both CT-1 and CT-2
Planning is done on both CT-1 and CT-2
DIBH plan is implemented, then patient will positioned in the simulated position. In DIBH the
patient is aligned with in-room lasers, the necessary sifting of patient to the treatment isocenter
is done.
The verification image (CBCT/EPID) images are also taken in DIBH, couch corrections done and
radiation treatment is executed in DIBH

22.  Study setting: Dept. of Radiation Oncology, Kidwai
Memorial Institute of Oncology
 Study period: September 2019 to March 2020.
 Total number of Patients: 49.
 Carcinoma left Breast - where ever RT is indicated
Active Breath Controller (ABC)

23. Active Breath Controller (ABC)conti..
 Dose: BCS: 50Gy/25# + 10Gy/5# boost or 40Gy/15# + boost
10Gy/5# & MRM: 50Gy/25 fractions or 40Gy/15
 Technique: 3DCRT +/- free breathing or DIBH
Free Breathing
(n-25)
DIBH
(n-24)
Age 50±4.24 yrs 46±2.5yrs
Surgery type
BCS 3 6
MRM 22 18
Stage I - II 18 17
III 7 9

24. Active Breath Controller (ABC)conti..
Left breast patients treated with DIBH had statistically significant dose
reduction with respect to Mean dose to heart, percentage volume of
heart receiving 30Gy and Volume of lung receiving 20Gy compared to
free breathing technique.
Free Breathing
(n-25)
DIBH (n-24)
P-value
RT Technique 3DCRT
3DCRT +/-
hybrid VMAT
Left
Lung
Mean dose (Gy) 13.73±0.76 13.61±1.06 0.5876
V20Gy (volume-%) 29.5±8.71 24.7±4.94 0.005*
V15Gy(volume-%) 31.38±9.18 30.14±1.41 0.502
Heart Mean dose (Gy) 7.75±4.32 4.5±1.09 0.0003*
V30Gy (volume -%) 12.15±7.01 3.09±1.16 0.005*
V5Gy (volume- %)
26.16±9.12 25.08±21.21 0.75

25. Active Breath Controller (ABC)conti..
Advantage : Greater confidence in Tumour targeting
Limitations of ABC:
 Time consuming
 Cannot be integrated to the CT Simulator- Hence
automated gated simulation not possible.
 Maintenance of the ABC system and laptops.
 The superior threshold for the volume by which the chest
expands cannot be set.
 recurring cost – Mouth Piece
 Sterilization of mouth piece ???-
 Limitations - ongoing COVID PANDEMIC?????

26. Real-time Position Management
(RPM) system
 advantages
 noninvasive,
 easy to use,
 well-tolerated by patients
 because only an external respiratory signal is acquired, the correlation
between tumor motion and patient respiration must be closely
monitored throughout treatment.
Other system: ExacTrac X-Ray Monitoring System
 combine Xray imaging of internal anatomy with an external respiratory
signal.
 This technique allows the correlation between tumor position and
patient respiration to be continuously updated at a reasonable
frequency, keeping patient x-ray exposure in mind.

27. RPM – Attention to marker motion
and respiratory cycle – beam ON
mismatch

28. Thank You

29. AAPM Task Group 76a
 Intrafraction motion is an issue that is becoming
increasingly important in the era of image-guided
radiotherapy
 Intrafraction motion can be caused by the respiratory,
skeletal muscular, cardiac, and gastrointestinal
systems.
 Of these four systems, much research and
development to date has been directed towards
accounting for respiratory motion.
 Respiratory motion affects all tumor sites in the thorax
and abdomen