734
M. Dohlus et al.
speed of 100 mm s −1 allows a high repetition rate of the scanning spots so that
a ‘volumetric multipainting’ of the tumour target is achievable. One-liter tumour
volume at a rate of 100 Hz can be repainted by the pencil beam several times in
few minutes reducing the statistical uncertainty in the delivered dose by a factor
√
n (where n is the number of re-paintings) and minimizing any local accidental
under-dosage or over-dosage. This method also improves the synchronization of
the irradiation with the breathing movements. A second development concerns the
superconductive gantry. The structure, studied for carbon-ion beams up to 430
MeV/u, has a radius of 5.5 m and a wait of approximately 200 tons, comparable
with normal-conductive proton therapy gantries and sensibly lighter than the 600
tons gantry built in Heidelberg.
The ultimate goal is the treatment of moving organs, a challenge that is more
critical in hadron therapy than in conventional therapy because of the dose is concentrated in the Bragg peak. In this case the accelerating system and beam delivering
system require a feedback that, based on on-line movement detection, adapt in few
milliseconds the beam characteristics to the three dimensional movements of the
target.
11.3.2.4 Present and Future Challenges
There is still space for improving the dose delivery, for instance, the active dose
delivery systems for protons and carbon ions have been used for a small part of the
patients treated with protons or ions. In spite of the fact that most new centres are
featuring ‘active’ scanning systems and some of the existing centres are upgrading
to them, the implementation in the clinical practice has been for many years quite
slow.
As far as the accelerators and transfer lines are concerned, two main lines of
research have to be intensively pursued:
• systems which actively scanned are able to follow the tumours which are subject
to movements,
• accelerator and delivery systems which are lighter, smaller, more efficient, and
less power consuming than the present cyclotrons
Fast Cycling Accelerators to Follow Moving Organs
In conventional radiotherapy various techniques have been introduced to determine
in real time the position of an irradiated tumour which moves, for instance, because
of the respiration cycle and to deliver the dose following these movement in IGRT.
In this case computer controlled multileaf collimators are used. In hadron therapy
the tumour position can be detected with the same methods and a better followup can be obtained by rapidly moving the Bragg spot so to compensate for threedimensional movements.
In the transverse plane the active scanning of tumours with hadron pencil beams
is obtained by adjusting two perpendicular magnetic fields located many meters
M. Dohlus et al.
speed of 100 mm s −1 allows a high repetition rate of the scanning spots so that
a ‘volumetric multipainting’ of the tumour target is achievable. One-liter tumour
volume at a rate of 100 Hz can be repainted by the pencil beam several times in
few minutes reducing the statistical uncertainty in the delivered dose by a factor
√
n (where n is the number of re-paintings) and minimizing any local accidental
under-dosage or over-dosage. This method also improves the synchronization of
the irradiation with the breathing movements. A second development concerns the
superconductive gantry. The structure, studied for carbon-ion beams up to 430
MeV/u, has a radius of 5.5 m and a wait of approximately 200 tons, comparable
with normal-conductive proton therapy gantries and sensibly lighter than the 600
tons gantry built in Heidelberg.
The ultimate goal is the treatment of moving organs, a challenge that is more
critical in hadron therapy than in conventional therapy because of the dose is concentrated in the Bragg peak. In this case the accelerating system and beam delivering
system require a feedback that, based on on-line movement detection, adapt in few
milliseconds the beam characteristics to the three dimensional movements of the
target.
11.3.2.4 Present and Future Challenges
There is still space for improving the dose delivery, for instance, the active dose
delivery systems for protons and carbon ions have been used for a small part of the
patients treated with protons or ions. In spite of the fact that most new centres are
featuring ‘active’ scanning systems and some of the existing centres are upgrading
to them, the implementation in the clinical practice has been for many years quite
slow.
As far as the accelerators and transfer lines are concerned, two main lines of
research have to be intensively pursued:
• systems which actively scanned are able to follow the tumours which are subject
to movements,
• accelerator and delivery systems which are lighter, smaller, more efficient, and
less power consuming than the present cyclotrons
Fast Cycling Accelerators to Follow Moving Organs
In conventional radiotherapy various techniques have been introduced to determine
in real time the position of an irradiated tumour which moves, for instance, because
of the respiration cycle and to deliver the dose following these movement in IGRT.
In this case computer controlled multileaf collimators are used. In hadron therapy
the tumour position can be detected with the same methods and a better followup can be obtained by rapidly moving the Bragg spot so to compensate for threedimensional movements.
In the transverse plane the active scanning of tumours with hadron pencil beams
is obtained by adjusting two perpendicular magnetic fields located many meters