|Comment||Department of Oncology, Radiology and Clinical Immunology, UU|
|Title||Patient positioning in radiotherapy using body surface laser scanner|
|Abstract||In curative radiotherapy the goal is to deliver a dose sufficient to sterilise tumour cells, while keeping the dose burden to normal tissues within acceptable limits. The treatment process starts by imaging the patient in treatment position with computed tomography (CT). Target areas with tumour cells, radiation sensitive structures, organs and the body surface are segmented based on the CT images. The data are then used in a treatment planning system (TPS) to design a treatment where the type of radiation, its intensity, etc, are varied until the resulting dose distribution is satisfactorily shaped with respect to trade offs between sufficient tumour dose and risk for complications. The algorithms used in TPS’s have in recent years improved considerably, which in combination with the development of the radiation delivery equipment has enabled new therapy concepts with precisely shaped and locally concentrated dose distributions, e.g intensity modulated radiotherapy IMRT and intensity modulated proton therapy IMPT.
The focus for technical improvements of radiotherapy is now shifting from development of planning and radiation modulation techniques, to development of target localisation, patient positioning and radiation monitoring techniques. This is to assure that the more complex plans now produced can be implemented in practice and actually achieves better treatments. The most extensive measure of the patient at the treatment delivery is to use cone beam CT (CBCT) integrated into the treatment delivery system. This approach provides full 3D imaging of the patient, but is costly to implement and requires additional time of image acquisition due to limitation of gantry rotation speed plus extra time for evaluation. CBCT approach also imposes a higher dose burden to the patients.
An alternative way to set up the patient for radiotherapy is the use of a body surface laser scanner (BSLS) system. A body contour from the patient is acquired from the reflection of a laser beam scanned over the body. The scanned 3D body surface is rigidly registered with the 3D surface determined from the original CT-study used for treatment planning. The BSLS system may also monitor the patient position during treatment and serve as a detector for respiratory gating. The laser scanning technique is fast and inexpensive compared to CBCT-systems.
This seminar concerns the correlation between inner and outer anatomy in radiotherapy and how accurately the set up of the patient can be by the use of a BSLS system. Can a BSLS system be used instead of a CBCT to save time and dose burden to the patient?