Title: Treatment delivery from the patient perspective: potential indication, set-up and organ motion issues at CNAO
1Treatment delivery from the patient perspective
potential indication, set-up and organ motion
issues at CNAO
ESF Exploratory Workshop on Advanced
Instrumentation for Cancer Diagnosis and
Treatment Oxford, United Kingdom, 23 26
September 2008
2We all know how nice it is to have the Bragg peak
Goitein et al, Physics today, 2002
Courtesy of Dr. Ando, NIRS
3We all know how nice it is to have a high RBE
(and only where you need it)
CIRT
7 years later
Vertebral osteosarcoma
Imai et al., Lancet Oncology 2006
4- We can hope in good clinical results if we are
able to deliver this radiation, with nice
physical and biological properties, to the target - We have to know where the target is
- No matter how good our beam, if the target is not
where we thought we will not kill the tumor
5Missing the target
6Why should the target be elsewhere?
- Mispositioning (interfraction)
- Organ motion (intrafraction)
- Shape change (interfraction)
7This issues are much more critical in
hadrontherapy (compared to photons RT) because of
- Steeper gradients
- Dose distribution heavily dependent on tissue
density - Hypofractionation
8- Organ motion is even more critical when active
scanning is used (risk of hot and cold spots) - For the CNAO delivery system spot size will be
of millimiters (4 - 10) and time scale will be of
milliseconds.
9- What has been done until now ?
- What do we plan to do at CNAO ?
- What would we like to do but do not know how?
10Delivery system at CNAO
- Fixed vertical and horizontal beams
- Active spot scanning (no passive spread beam)
111 - Precise positioning
- Always an issue (for all body sites)
- Need of fixation devices
- Need of position verification devices
- Need of 6 DOF position correction devices
- The only issue for some body district (limb,
head, spine ?) - Time consuming
12Precise positioning
- We believe that for fixed body sites a
orthogonal KeV X-Ray imaging coupled to a robotic
positioning device is necessary and sufficient. - Head and body masks, personalized cushions, bite
blocks and all such devices employed in high
precision photons RT can be straightforwardly
transferd to hadrontherapy
13A customized Schaer systyem will be used
13
1414
15Courtesy of SEAG, RPTC
15
1616
172 Shape change
- Tumor shrinkage
- Weight loss or gain
- Dependent on tumor biology
- Relatively easy to cope with through close
clinical monitoring of the patient and frequent
off line imaging (e.g. each week for
gynecological malignancy) - Too late if discovered in the treatment room (a
check is anyway most necessary)
183 Organ motion
- The real problem
- Due to peristalsis, swallowing, heartbeat,
vessels pulsation but especially BREATHING - Affects lung treatments, liver treatments, and to
a lesser extent all abdominal and pelvic
treatments. If the patients is in supine position
(as may be necessary without a gantry) it may
also affect retroperitoneal treatments
19Breathing
- A complex caotic phenomenon
- Intervals of more or less regular breathing that
each 5- 15 minutes change pattern and through a
highly unpredictable phase reach a new temporary
steady state - No reliable correlation betwen body surface and
internal displacement during change of patterns - Frequency, Tidal volume, relative role of
thoracic muscles and diaphragm and end expiration
volume are among the parameters that can change
in minutes - Elevated inter-patient and intra-patient
variability - Pain and emotional status can influence breathing
pattern - Displacements up to 3-4 cm can take place
- Not possible to predict a priori direction and
amplitude of a lung nodule displacement
20How to deal with respiratory organ motion
- Breathhold, gating, tracking, coaching, abd.
pressure - Whichever you choose you need to measure motion
(target position or surrogate marker) - Once you know how the target moves you can steer
the beam, or decide to enlarge the irradiated
volume (a simple CTV ? PTV approach is not
adequate) - It is mandatory to check what you are doing (a
real time, in vivo dosimetry would be
appreciated) - Robustness of the treatment plan should be
considered (ideally as a parameter for inverse
planning optimization) - Everything should happen in real time
21Strategies
- Breath hold requires active cooperation, you
cannot avoid measuring target position (to be
sure it is performed correctly) - Gating (in my opinion probably the best
solution) - Tracking much more complicated with only a small
gain on time efficiency
22Measuring target displacement
- Breathing is a caotic phenomenon
- Surrogate markers air flow, body surface
position (simple 1D marker option cfr NIRS, or
optoeletronic surface reconstruction with or
without passive markers) - Measuring the real thing implanted markers and
fluoroscopy, or frequent X-ray (how often ?)
23Surrogate markers
Only the phase probably not enough for spot
scanning (and for stack layer?)
24More advanced surface reconstruction
Body markers
Surface reconstruction
25- From the camera images to the surface or marker
position - From the marker position to the target position
- How many msec ?
- At the end it is only a guess (caotic behaviour,
hysteresis) - NOT ENOUGH
26You have to look at what you do
- Fluoroscopy (radioprotection issues)
- Periodic x-ray check during dose delivery to
verify the external ? internal model, i.e. you
trust the model for a short time between cheks
(how often have I to check ? Regular interval vs.
adaptive interval cfr. Isaksson et al, Med Phys
2005)
27- What has been done until now (by us)?
- X-ray Exac trac with a custom made BH system
(together with EIO and Politecnico di Milano).
Accuray Synchrony (together with CDI) .. ? - ? not precise enough for spot scanning
- What do we plan to do at CNAO ?? ?? . In the
beginning only fixed targets
28What would we like to do but do not know how?
- Approach similar to Accuray synchrony but with
better surface detection and adaptive chek
intervals (optimizing what already exist) ?
Problem our orthogonal X ray flat panels cannot
be both in position when the terapeutic beam is
on - Something new??
29- Can we detect in real time without extra dose to
the patient the position of a lung nodule ? - Can we avoid invasive fiducial marker placement ?
(I believe NO) - Could we measure the position of an implanted
marker in some other way ? Maybe measuring the
influence of an implanted coil on an external
magnetic field makes sense or is it only an
ignorants dreor measuring the change in electric
capacitance? Is anybody working on this? Does it
am? Would it work with a ion beam on?
30If you have an idea you like be sure somebody
else had already had it quite a while ago !
30 mm 20 mm 10 mm
Meas. Sci. Technol. 19 (2008) 024006 (9pp)
doi10.1088/0957-0233/19/2/024006 Tracking of
internal organ motion with a six
degree-of-freedom MEMS sensor concept and
simulation study Manuel Bandala and Malcolm J
Joyce
31Implantable with 14 gauge needle Accuracy 0.2
mm Read out rate 10 Hz Not yet tested in clinics
Balter et al, IJROBP 2005
32We are the ones who could benefit most of such
sensors
- Hadrontherapy as a community should support those
researches - Probably not too ambitious a goal but investment
and focusing are required
33- Steering the beam is easier than measuring the
motion - Novel approaches are welcome
- We should strive for a continuous real time
measurment of the target position - At present I believe we need implanted markers
- In the end active spot scanning may turn out to
be simply not the best way to treat lung and
liver and we may have to go back to passive
spreading
34Quality assurance and in vivo dosimetry
- Organ motion is difficult to deal with, we have
to check what we are doing and how effective it
is - In vivo dosimetry is mandatory
- In vivo dosimetry can detect also shape changes
that eluded clinical monitoring
35What has been done until now (not by us)?
What do we plan to do at CNAO ?
- In beam PET (cfr. FP7 call)
- AQUA
36- Those approaches have much in common
- They mesure something that would have happened
anyway (and so no extra dose is delivered to the
patient) - If the result is positive you can be sure that
everything went well, if it is negative you are
not sure of what went bad - The signal that can be detected bears less
information respect to the actual dose
distributions and therefore cold spots may be
masked by a blurring effect - You know the result after the treatment session
is ended, for hypofractionated treatments it may
be too late
37Different dose
38What would we like to do but do not know how?
- When a fiducial marker is inserted, have a
dosimeter inside it (it should be read without
extracting the fiducial from the patient body).
Science fiction ? - Have a proton portal imaging (or part of it) to
check position during dose delivery
39Proton portal imaging ?
- (CNAO can accelerate C12 to 400 MeV/u so protons
could be much faster) - Would it be possible to put the Bragg peak beyond
the patient and measure the range without
delivering a high dose ?
40How much dose ?
Can we build this black box ?
41?
42Thank you for your attention