Dosimetry of an in-line kilovoltage imaging system and implementation in treatment planning.
OBJECTIVE
To present the beam properties of the Siemens 70-kV and 121-kV linear accelerator-mounted imaging modalities and commissioning of the 121-kV beam in the Philips Pinnacle treatment planning system (TPS); measurements in an Alderson phantom were performed for verification of the model and to estimate the cone-beam CT (CBCT) imaging dose in the head and neck, thorax, and pelvis.


METHODS
The beam profiles and depth-dose curve were measured in an acrylic phantom using thermoluminescent dosimeters and a soft x-ray ionization chamber. Measurements were imported into the TPS, modeled, and verified by phantom measurements.


RESULTS
Modeling of the profiles and the depth-dose curve can be achieved with good quality. Comparison with the measurements in the Alderson phantom is generally good; only very close to bony structures is the dose underestimated by the TPS. For a 200° arc CBCT of the head and neck, a maximum dose of 7 mGy is measured; the thorax and pelvis 360° CBCTs give doses of 4-10 mGy and 7-15 mGy, respectively.


CONCLUSIONS
Dosimetric characteristics of the Siemens kVision imaging modalities are presented and modeled in the Pinnacle TPS. Thermoluminescent dosimeter measurements in the Alderson phantom agree well with the calculated TPS dose, validating the model and providing an estimate of the imaging dose for different protocols.
Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany. Electronic address: yvonne.dzierma@uks.eu.
Yvonne
Y
Dzierma
Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany.
Frank
F
Nuesken
Hochschule für Technik und Wirtschaft des Saarlandes, Saarbrücken, Germany.
Wladimir
W
Otto
Department of Radiation Oncology, University of Minnesota, Minneapolis, Minnesota.
Parham
P
Alaei
Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany.
Norbert
N
Licht
Department of Radiation Oncology, Saarland University Medical Center, Homburg/Saar, Germany.
Christian
C
Rübe
D054893:Cone-Beam Computed Tomography; D004867:Equipment Design; D006257:Head; D009333:Neck; D010315:Particle Accelerators / Q000295:instrumentation*; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation*; D013819:Thermoluminescent Dosimetry / Q000379:methods; D013909:Thorax