Article
Ex vivo studies and first case reports on PET/CT based marker implantation for image guided high precision radiotherapy for skull base tumors
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Authors
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Dieter Woischneck
- Klinikum Landshut
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Norbert Blumstein
- Paracelsus Klinik Osnabrück
| Published: | May 21, 2013 |
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Outline
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Objective: To evaluate the role of PET/CT (hybrid scanner of positron emission tomography and computed tomography) for gross target volume (GTV) delineation in patients with skull base tumors and 2. To evaluate the role of metallic markers before radiation treatment planning for minimizing movement patterns during image guided high precision radiation therapy (IGRT).
Method: After PET/CT imaging two types of markers, a golden seed and a brazen coil, were implanted into the skull base of an anatomical human whole head preparation. Afterwards a computed tomography (CT) scan and a 3D marker image guided high precision RT was planned and simulated with a state-of-the-art high precision RT accelerator (Novalis TX® with 6D robotics couch). The position of the marker was controlled with a cone beam CT before and with “on board imaging” during RT-simulation. The impact of the markers material, size and shape on image artefacts was evaluated. The marker type with the best properties was selected and used in the image guided high precision RT (IGRT) of a case of synchronous tumor of the nose (adjuvant RT) and the epipharynx (primary RT). Markers were implanted under local anaesthesia and radiotherapy was planned and performed on the Novalis TX.
Results: Least image artefacts were observed with the golden seed marker. For best results size must be <1mm and inter-marker distance >6 mm. The markers implanted allowed precise RT of the sites of interest with different shapes and dose concepts simultaneously, while sparing the spinal cord and the brain.
Conclusions: The implantation of golden markers in addition to PET/CT imaging in primary tumors, recurrent tumors and resection sites on the skull base is feasible and well tolerated. These markers allow image guided high precision RT of multiple sites simultaneously with correction of patient movements. Further PET/CT based target volume delineation may be of additional benefit especially in patients with recurrent tumors being retreated with radiation therapy.
