Download Proton Therapy

Advanced Techniques:
Tomotherapy, GammKnife, CyberKnife, MR-Linac,
Proton Therapy, Vero
Jason Yan, MS, DABR, MCCPM
05/2015. Yanxxs at gmail dot com
Radiation Oncology & CyberKnife, U of Arizona Cancer Center at St Joseph’s Hospital & MC
GammaKnife, Barrow Neurological Insitute.
Big Picture:
World wide:
Linac
Tomo
GammaKnife
CyberKnife
# of machines
~8000
~300
~550
~500
# of pts treated
50,000,000
~100,000 ??
700,000
100,000
Existing in market
58 yrs
12 yrs
28 yrs
14 yrs
Proton Therapy
Vero
14(+11) in US
<5
~30,000
??
24 yrs
~4 yrs
Main sites treated
56%: lung, prostate, breast. 44%: all others
Mainly pelvis, prostate, H&N, etc.
Brain SRS (1 fx)
50% Brain SRS, 50% SBRT: lung, spine,
prostate, liver, pancreas, etc.
Some facts:
--- there are ~2000 cancer centers in US. 60% cancer patients were treated with RT. (in China, only ~15% cancer patients
were treated with RT).
--- for RT patients: ~75% is curative. Lowest cure rate including: 59% for lung, 50% for brain.
--- for RT patient: ~88% treated with EBRT (Linac, Tomo), ~6% GammaKnife, ~4% CyberKnife, ~6% brachy, etc.
--- on average, every RT patient will be treated with 23.4 fractions.
Tomotherpy (competitor with Linac)
Miniature Linac: X-band, 6MV only. Beam stopper as weight balance. (Linac: S-band, more stable)
Helical beam: gantry rotation + table moving in. It can treat 160cm length in Sup/Inf direction instead of 40cm.
Pneumatic driven MLC leaf:
-- 20 ms to close or open (binary MLC). More stable.
-- Higher dynamic range of intensities leads to better plan. (No rounded leaf end effect, no DLG, no sliding).
Jaw opening: 5mm – 50mm (equivalent to MLC leaf thickness of Linac)
Structure: Leaf height 10cm (MLC 6.3cm), collimator height 22cm.
Tomotherapy machine structure: every compacted into the ‘donut’. Shielding design requirement is much less stringent.
Fan beam irradiation: sharper penumbra  better plan. (similar to: CT has lesser noise than CBCT)
Linac
Iso wobbling
Table accuracy
Gantry speed
Field size
MLC
Beam penumbra:
Intensity level:
Non-coplanar beams:
Delivery accuracy:
~1mm
~1mm
5.6o/sec
40cm * 40cm
-- (60 leaves) x (2 banks), along Y direction.
-- Leaf thickness: 5mm/10mm
-- Modulation at rotational direction:
leaf speed 2.5cm/sec
-- leaf sliding 2.5cm/sec max.
-- prone to mechanical failure.
Moderate
Moderate
Yes  better plan for brain cases.
Good
SRS plans
CBCT
3D-CRT plans
CNS, TBI plans
Breast plans
Electron field plans
Yes
KV-CBCT has better soft-tissue contrast
Simple.
Need field junction
Easy
Yes, simple.
Room shielding
requirement
Portal dosimetry
~2m concrete wall
EPID panel (not really measuring dose)
Tomotherapy
0.2mm (mini-linac on ring)
0.25mm
30o/sec
160cm * 38cm
-- 64 leaves, along X direction.
-- Jaw opening: 5mm-50mm
-- Modulation at rotational direction:
binary at 6.25mm leaf thickness.
-- binary MLC (20 ms)
-- stable
Small  better plan
Big dynamic range  better plan
No
May be better, but largely depends on setup
uncertainty, and organ motions.
No (no cone)
MVCT has less image noise (fan beam).
Has to use helical IMRT, but comparable.
Easier
More complicated?
Has to use helical IMRT, but could be
comparable.
Much less requirement (beam stopper).
511 Xenon ion chamber ring  easy for
dose reconstruction.
二. GammaKnife
2.1) GK model 4C
(up to 2006):
Principle:
-- 201 Co-60 sources. 4 helmets with 4, 8,
14, 18mm collimator sizes respectively. All
collimator central axis focus on the center
of helmet (iso). Each helmet has 201
source holding chambers, with some
chambers empty and some loaded, it can
create different shape of isodose lines (at
prescription dose level).
-- Alloy frame with sharp pins that are
screwed into patient skull after local
anesthesia. Frame acts as the origin and
coordinate system for the head and tumor
in MR Image.
-- cap with image marker lines helps to
determine frame position in 3D space.
-- most GK SRS cases are done with MR
image, not CT. Assuming water in head.
-- TG 51 output? NO!
Task Group No. 178 – Gamma Stereotactic Radiosurgery Dosimetry and Quality Assurance
2.2) GK Perfexion
(2006)
-- built-in auto collimator size change, auto plugging by sectors.
-- sector: 6+4+5+4+5=24 sources/sector * 8 sectors = 192 sources.
-- By moving a sector, the corresponding set of sources is aligned with a specific size of collimator set (16mm, 4mm, off,
8mm), or beam off.
-- couch positioning system: LGK 4C -- auto positioning, or manual trunnion(炮耳) setting positions pt head. LGK Perfexion:
whole body movement, the couch is the positioning system.
-- head frame and caps are the same.
GK Perfexion Video https://www.youtube.com/watch?v=mAktF38ALus
Safety:
US Homeland Security: camera, alarm disable when going in, iris scan (background investigation by FBI), etc.
三. CyberKnife
-- Fixed 133 “nodes” in 3D space (114 nodes for body)
-- SAD = 80cm (or 65 cm)
Various Tracking methods with CyberKnife:
6D Skull Tracking
Spine Tracking
Tumor site
Brain
Near spine (C,
T, L, sacral)
Algorithm of tracking
KV image pairs of bone
Tracking accuracy*
0.44±0.12mm
Remark
KV image pairs of spine
0.52±0.22mm
Spine is distortable
Lung Tracking
in lung
KV image pairs of tumor
in lung, if visible.
Fiducial Tracking
in lung,
prostate, liver,
etc.
KV image pairs of
fiducials (1, or ≥3)
0.73±0.33mm
Moving tumor. MC optimization.
(1.4±1.1mm for patient)
MC dose calculation.
0.70±0.33mm
Fiducials on the perimeter of
(dynamic)
tumor. Wait 5-7 days after
0.29±0.10mm (static)
implant to stabilize fiducials.
*. Error includes planning CT image error, TPS error, KV image pair error, and robot tracking error.
Comparison between GammaKnife and CyberKnife:
GammaKnife
CyberKnife
Frame?
Frame
No frame, use mask.
Fractionation possible?
No
Yes
Real-time tracking?
No
Yes
Overall pt positioning accuracy?
<1mm
<1.0-1.5mm
Biggest cone size
16mm
60mm (G6 has Micro-MLC)
Gradient Index (GI=V50%Rx/V100%Rx)
2.5-3.0 for brain (better)
3.0-3.5 for brain
Treat body
No
Yes (lung, liver, prostate, etc.)
Dose Prescription
50% of Dmax
70% of Dmax
Cost of machine
2.5 million,
3.5 million, service 0.3 million/yr.
change sources 1.5 million/5 yrs.
Cost per patient
~$25,000 (surgery ~80,000?)
TG 135. quality assurance for robotic radiosurgery.
~$40,000 (regular EBRT: ~$20,000)
四. MR-Linac
4.1) MR: great soft tissue contrast.
-- Imaging frequency of MR: 2/sec (at best). 4D-MR (multi-cycle) much better than 4D-CT (single cycle). No dose!!
-- CBCT has good soft tissue contrast, but imaging frequency is 1/min (due to gantry speed limit).
-- opens the possibility of “see what you treat”!
-- Computer technology will make the real-time contour and real-time tracking possible!! Math model from 4D-CT is only
for one cycle of motion, not representative, need real-time tracking.
-- can also see tumor response, adjust dose on the fly  customized RT.
4.2) 1999 invention, 2004 design, 2009 first prototype, now 3rd generation in clinic.
4.3) Bright future:
GTV
CTV
Distant tumors
chemo
+/+
RT (with MR-linac)
++
++
surgery
+
+/-4.4) One of the pioneers in MR-Linac development family with Elekta company:
-- UMC Utrecht: 150 PhD’s, 80% with MRI titles. 20 MR-Linac research physicists, and 20 clinical physicists. 13 professors.
4.5) expect 510K approved by FDA in 2017.
4.6) ViewRay MR-Linac: 3 Co-60 sources at 120o apart. Not-popular: penumbra big??
Elekta MR-Linac Research Consortium:
The consortium includes the University Medical Center Utrecht (Utrecht, the Netherlands), The University of Texas MD
Anderson Cancer Center (Houston, Texas), The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital
(Amsterdam, the Netherlands), Sunnybrook Health Sciences Centre (Toronto, Ontario), The Froedtert & Medical College of
Wisconsin Cancer Center (Milwaukee, Wisconsin), The Institute of Cancer Research (London, UK), and The Royal Marsden
NHS Foundation Trust (London, UK). http://www.hotspot.philips.com/article/mr-linac/
五. Proton Therapy
5.1) Brag Peak magic:
5.2) principles and Proton Center layout:
5.3) Since the first medical center of PBT (Photon Beam Therapy), at least 2/3 of all radiation oncologists and physicists
have been discouraging its use in clinics. Reasons are:
-- Photon therapy has already achieved very successful curative rate for most type of cancers. It is very unlikely PBT will achieve
significant better curative rate.
-- Bottle neck for radiation therapy is imaging of soft tissue in real time, hence tracking organ motions in real time, which is not
solved at all by PBT. Rather, this will largely diminish the effect of PBT.
-- PBT is significantly more expensive than photon therapy (at least 4 times higher cost), especially the initial investment (at least
10 times higher).
5.4) Publications constantly warning our society to discourage PBT:
JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, VOLUME 16, NUMBER 3, 2015. Proton-beam therapy: are
physicists ignoring clinical realities? R. J. Schulz, Ph.D. Department of Therapeutic Radiology, Yale University
Summary It is eminently clear from phase II evaluations of the more common cancers that the clinical outcomes of PBT are
no better — nor any worse — than those achieved by IMRT or SBRT. This broad statement is supported by the reviews of
Brada et al.,(22) Lodge et al.,(23) Olsen et al.,(24) and Brada et al.(25) that compare the clinical results achieved by PBT for
a wide variety of disease sites with those achieved by more conventional means.
The conclusions reached by Lodge and Olsen and their colleagues are essentially the same as those of Brada et al.:(22) “An
uncontrolled expansion of clinical units offering as yet unproven and expensive proton therapy is unlikely to advance the field
of radiation oncology or be of benefit to cancer patients.”
22. Brada M, Pijls-Johannesma M, De Ruysscher D. Proton therapy in clinical practice: current clinical evidence. J Clin Oncol.
2007;25(8):965–70.
23. Lodge M, Pijls-Johannesma M, Stirk L, Munro AJ, De Ruysscher D, Jefferson T. A systematic literature review of the
clinical and cost-effectiveness of hadron therapy in cancer. Radiother Oncol. 2007;83(2):110–22.
24. Olsen DR, Bruland OS, Frykholm G, Norderhaug IN. Proton therapy — a systematic review of clinical effectiveness.
Radiother Oncol. 2007;83(2):123–32.
5.4) Massive market capitalization can confuse people for a period of time, but won’t be long.
-- Smoking was a fashion and 70% of people in US smokes for almost 40 years until 1930, which is ~20 years later than
medical and scientific findings that smokers are 5-25 times more related to lung cancer than non-smokers!
-- smoking was considered a fashion, an energy booster, a mental soother, and even good to health in the past in US.
六. Vero
6.1) Video of VERO machine: https://www.youtube.com/watch?v=YFoAC_nmPdg
6.2) A “combination” of Tomotherapy and CyberKnife：
-- miniature linac rotates in a donut shape gantry (similar to Tomotherapy).
-- it has two KV-imager for 3D positioning of patient bone structure (similar to CyberKnife or ExacTrac, but KC-imager
moving with linac head instead of fixed on ceiling or under floor.)
-- Linac head can rotate itself in a certain cone range, donut shaped gantry can also rotate in a certain angle range, with 6D
couch (similar to CyberKnife).
-- less than 10 machines sold in the world.