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Erschienen in:
01.01.2012 | Original article
Phase-specific cone beam computed tomography reduces reconstructed volume loss of moving phantom
Erschienen in: Strahlentherapie und Onkologie | Ausgabe 1/2012
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Purpose
The accurate volumetric calculation of moving targets/organs is required to use cone-beam computed tomography (CBCT) for replanning purposes. This study was aimed to correct the reconstructed volume losses of moving phantoms by phase-specific CBCT.
Materials and methods
Planning fan-beam CT (FBCT) of five hepatobiliary/gastrointestinal/pancreatic cancer patients were acquired under active breathing control and compared with free-breathing CBCT for kidney volumes. Three different-sized ball phantoms were scanned by FBCT and CBCT. Images were imported to a planning system to compare the reconstructed volumes. The phantoms were moved longitudinally on an oscillator with different amplitudes/frequencies. The phase-specific projections of CBCT for moving phantoms were selected for volume reconstruction.
Results
The differences in reconstructed volumes of static small, medium, large phantoms between FBCT and CBCT were − 6.7%, − 2.3%, and − 2.0%, respectively. With amplitudes of 7.5–20 mm and frequencies of 8–16 oscillations/min, volume losses on CBCT were comparable with FBCT in large moving phantoms (range 9.1–27.2%). Amplitudes were more subject to volume losses than frequencies. On phase-specific CBCT, volume losses were reduced to 2.3–6.5% by reconstruction using 2–3 projections at end/midoscillation phase.
Conclusion
Amplitude had more impact than frequency on volume losses of moving phantoms on CBCT. Phase-specific CBCT reduced volume losses.