Radiation Oncology BioMed Central

BackgroundThe precision in carbon ion radiotherapy depends on the calibration of Hounsfield units (HU) as measured with computed tomography (CT) to water equivalence. This calibration can cause relevant differences between treatment planning and treatment delivery.MethodsCalibration data for several soft tissues were measured repeatedly to assess the accuracy of range calibration. Samples of fresh animal tissues including fat, brain, kidney, liver, and several muscle tissues were used. First, samples were CT scanned. Then carbon ion radiographic measurements were performed at several positions. Residual ranges behind the samples were compared to ranges in water.ResultsBased on the measured data the accuracy of the current Hounsfield look-up table for range calibration of soft tissues is 0.2 ± 1.2%. Accuracy in range calibration of 1% corresponds to ~1 mm carbon ion range control in 10 cm water equivalent depth which is comparable to typical treatment depths for head and neck tumors.ConclusionCarbon ion ranges can be controlled within ~1 mm in soft tissue for typical depths of head and neck treatments.

[1]  E. Pedroni,et al.  The calibration of CT Hounsfield units for radiotherapy treatment planning. , 1996, Physics in medicine and biology.

[2]  P Zygmanski,et al.  The measurement of proton stopping power using proton-cone-beam computed tomography. , 2000, Physics in medicine and biology.

[3]  S Minohara,et al.  Relationship between CT number and electron density, scatter angle and nuclear reaction for hadron-therapy treatment planning. , 1998, Physics in medicine and biology.

[4]  D. Schardt,et al.  Magnetic scanning system for heavy ion therapy , 1993 .

[5]  E Pedroni,et al.  Proton radiography as a tool for quality control in proton therapy. , 1995, Medical physics.

[6]  D F Jackson,et al.  The relation between X-ray CT numbers and charged particle stopping powers and its significance for radiotherapy treatment planning. , 1983, Physics in medicine and biology.

[7]  E Pedroni,et al.  The precision of proton range calculations in proton radiotherapy treatment planning: experimental verification of the relation between CT-HU and proton stopping power. , 1998, Physics in medicine and biology.

[8]  Nobuyuki Kanematsu,et al.  A CT calibration method based on the polybinary tissue model for radiotherapy treatment planning. , 2003, Physics in medicine and biology.

[9]  O Jäkel,et al.  Treatment planning for heavy-ion radiotherapy: physical beam model and dose optimization. , 2000, Physics in medicine and biology.

[10]  D. Schardt,et al.  Correlation between CT number and water-equivalent thickness for heavy charged particles , 2000 .

[11]  J. Debus,et al.  [Carbon ion irradiation of skull base tumors at GSI. First clinical results and future perspectives]. , 2000, Strahlentherapie und Onkologie : Organ der Deutschen Rontgengesellschaft ... [et al].

[12]  Barbara Kaser-Hotz,et al.  Patient specific optimization of the relation between CT-hounsfield units and proton stopping power with proton radiography. , 2004, Medical physics.

[13]  松藤 成弘.  Relationship between CT number and electron density, scatter angle and nuclear reaction for hadrontherapy treatment planning , 1998 .

[14]  G. Chen,et al.  Treatment planning for heavy ion radiotherapy. , 1979, International journal of radiation oncology, biology, physics.

[15]  Oliver Jäkel,et al.  Results of carbon ion radiotherapy in 152 patients. , 2004, International journal of radiation oncology, biology, physics.

[16]  O Jäkel,et al.  Relation between carbon ion ranges and x-ray CT numbers. , 2001, Medical physics.