title: Improving ion beam therapy treatment planning for  metal implants by using dual-energy CT scanning  
creator: Tremmel, Christoph
subject: ddc-530
subject: 530 Physics
description: One of the major uncertainties in ion beam therapy planning is the calculation of ion  ranges in the patient’s tissue from CT images. The presence of non-tissue-equivalent mate-  rials and materials with high photon attenuation like metals may aggravate this problem.  Dual Energy Computed Tomography (DECT) allows to compute the electron density  and effective atomic number. It could already be shown that this additional material  information enables a more precise calculation of ion ranges.  This thesis investigates the feasibility of the DECT approach for a range of metals from  aluminum (Z = 13) up to tungsten (Z = 74). DECT scans of the samples reconstructed  with a 16 bit CT scale and raw data based beam hardening correction were analyzed. The  electron density and effective atomic number of aluminum and titanium (Z = 22) could be  determined within the range of a few percent. These quantities could not be determined  for samples with Z ≥ 22, but the samples were distinguishable from each other by their  different CT numbers up to molybdenum (Z = 42). The precision of the determined ion  ranges could be improved for aluminum from -11.46% to 4.88% and for titanium from  -36.4% to 2.75% compared to ion range estimations from 120 kV CT. The size of nearly  all metal samples could be assessed from the images with precision in the range of the  voxel size of 0.6 mm. Streaking artifacts around the samples were minor for aluminum and  titanium. For materials with Z ≥ 26, severe artifacts could be observed.  The samples were investigated with Mega Voltage Computed Tomography to compare  DECT with this rivaling method. It was found that MVCT yielded superior results in case  of materials with Z ≥ 26. However, DECT offers in clinical routine the advantage of faster  scanning times and greater technical maturity of the scanner.  Discriminant analysis was tested as an alternative way to obtain ion ranges from Dual  Energy CT images without physical model. Only small mean absolute deviations from  reference ion ranges were observed for an animal sample.  
date: 2012-11-30
type: Master's thesis
type: info:eu-repo/semantics/masterThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/15216/1/MA_tremmel_final.pdf
identifier: DOI:10.11588/heidok.00015216
identifier: urn:nbn:de:bsz:16-heidok-152169
identifier:   Tremmel, Christoph  (2012) Improving ion beam therapy treatment planning for metal implants by using dual-energy CT scanning.  [Master's thesis]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/15216/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: ger