PMID- 28771749
OWN - NLM
STAT- MEDLINE
DCOM- 20180523
LR  - 20180523
IS  - 2473-4209 (Electronic)
IS  - 0094-2405 (Linking)
VI  - 44
IP  - 10
DP  - 2017 Oct
TI  - Registration of pencil beam proton radiography data with X-ray CT.
PG  - 5393-5401
LID - 10.1002/mp.12497 [doi]
AB  - PURPOSE: Proton radiography seems to be a promising tool for assessing the 
      quality of the stopping power computation in proton therapy. However, range error 
      maps obtained on the basis of proton radiographs are very sensitive to small 
      misalignment between the planning CT and the proton radiography acquisitions. In 
      order to be able to mitigate misalignment in postprocessing, the authors 
      implemented a fast method for registration between pencil proton radiography data 
      obtained with a multilayer ionization chamber (MLIC) and an X-ray CT acquired on 
      a head phantom. METHODS: The registration was performed by optimizing a cost 
      function which performs a comparison between the acquired data and simulated 
      integral depth-dose curves. Two methodologies were considered, one based on dual 
      orthogonal projections and the other one on a single projection. For each 
      methodology, the robustness of the registration algorithm with respect to three 
      confounding factors (measurement noise, CT calibration errors, and spot spacing) 
      was investigated by testing the accuracy of the method through simulations based 
      on a CT scan of a head phantom. RESULTS: The present registration method showed 
      robust convergence towards the optimal solution. For the level of measurement 
      noise and the uncertainty in the stopping power computation expected in proton 
      radiography using a MLIC, the accuracy appeared to be better than 0.3 degrees  for angles 
      and 0.3 mm for translations by use of the appropriate cost function. The spot 
      spacing analysis showed that a spacing larger than the 5 mm used by other authors 
      for the investigation of a MLIC for proton radiography led to results with 
      absolute accuracy better than 0.3 degrees  for angles and 1 mm for translations when 
      orthogonal proton radiographs were fed into the algorithm. In the case of a 
      single projection, 6 mm was the largest spot spacing presenting an acceptable 
      registration accuracy. CONCLUSIONS: For registration of proton radiography data 
      with X-ray CT, the use of a direct ray-tracing algorithm to compute sums of 
      squared differences and corrections of range errors showed very good accuracy and 
      robustness with respect to three confounding factors: measurement noise, 
      calibration error, and spot spacing. It is therefore a suitable algorithm to use 
      in the in vivo range verification framework, allowing to separate in 
      postprocessing the proton range uncertainty due to setup errors from the other 
      sources of uncertainty.
CI  - (c) 2017 American Association of Physicists in Medicine.
FAU - Deffet, Sylvain
AU  - Deffet S
AD  - Institute of Information and Communication Technologies, Universite catholique de 
      Louvain, Louvain-La-Neuve, 1348, Belgium.
FAU - Macq, Benoit
AU  - Macq B
AD  - Institute of Information and Communication Technologies, Universite catholique de 
      Louvain, Louvain-La-Neuve, 1348, Belgium.
FAU - Righetto, Roberto
AU  - Righetto R
AD  - Proton Therapy Unit, Hospital of Trento, Trento, 38122, Italy.
FAU - Vander Stappen, Francois
AU  - Vander Stappen F
AD  - Medical Accelerators Solutions - R&D, Ion Beam Applications (IBA), 
      Louvain-La-Neuve, 1348, Belgium.
FAU - Farace, Paolo
AU  - Farace P
AD  - Proton Therapy Unit, Hospital of Trento, Trento, 38122, Italy.
LA  - eng
PT  - Journal Article
DEP - 20170831
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
RN  - 0 (Protons)
SB  - IM
MH  - Algorithms
MH  - Calibration
MH  - Image Processing, Computer-Assisted/*methods
MH  - Phantoms, Imaging
MH  - *Protons
MH  - Radiometry
MH  - Signal-To-Noise Ratio
MH  - *Tomography, X-Ray Computed
OTO - NOTNLM
OT  - multilayer ionization chamber
OT  - particle imaging
OT  - proton radiography
OT  - range uncertainty
OT  - registration
EDAT- 2017/08/05 06:00
MHDA- 2018/05/24 06:00
CRDT- 2017/08/04 06:00
PHST- 2017/02/13 00:00 [received]
PHST- 2017/07/14 00:00 [revised]
PHST- 2017/07/21 00:00 [accepted]
PHST- 2017/08/05 06:00 [pubmed]
PHST- 2018/05/24 06:00 [medline]
PHST- 2017/08/04 06:00 [entrez]
AID - 10.1002/mp.12497 [doi]
PST - ppublish
SO  - Med Phys. 2017 Oct;44(10):5393-5401. doi: 10.1002/mp.12497. Epub 2017 Aug 31.