Radiotherapy
Radiotherapy
Introduction
One third of people in Britain will develop cancer at some time during their lives and about half are cured. Opportunities for active treatment are increasing, with improvements in radiotherapy and chemotherapy and the development of novel biological and molecular treatment approaches. Of all cancer patients - 22% are cured by surgery, 18% by radiotherapy and 5% by chemotherapy alone or in combination with surgery or radiotherapy. Radiotherapy remains the most effective nonsurgical treatment modality forming a central provision of treatment in Cancer Centres and is solely responsible for or significantly contributes to cure in 40% of the long-term survivors of cancer. 40-45% of all cancer patients will require radiotherapy …show more content…
This minimises the risk of a geographical miss that may compromise tumour control and increase surrounding normal tissue damage. To help in this process various immobilisation devices are available, which include vacuum moulded bags of polystyrene beads, and foam blocks and wedges, which can be used for trunk and limb immobilisation. Higher degrees of precision are required for treatment of CNS and head and neck tumours due to the close proximity of critical structures such as the spinal cord, eyes and optic chiasm. This can be achieved with immobilisation devices such as custom made perspex/plastic moulded shells (masks) that can be fixed to the treatment …show more content…
These treatments have to be planned and will involve the physics department.
For more complex treatment (Level 3) planning, volumes are defined on a CT study at a graphics terminal. At this level, the GTV, CTV and PTV can be defined in one or more planes (sections), using a series of CT and/or MRI sections. It is also assumed that the complete dose distributions are computed in the central plane and in other planes (sections) and with inhomogeneity corrections, when appropriate.
The computer planning system can develop digitally reconstructed radiographs (DRRs) that give beams-eye-views of the radiation fields.
6. Dosimetry.
Dosimetry is calculation of the amount of radiation dose absorbed by the patient. Beam data for treatment units are available as depth dose charts that allow simple dose calculation For simple field arrangements (single fields and parallel opposed fields), it is assumed that the dose at the ICRU Reference Point and an estimate of the maximum and minimum doses to the PTV can be determined using central axis depth dose tables. Radical treatments often require multiple and complex field arrangements to achieve the optimum dose to the tumour with normal tissue sparing, and modern computer planning systems are required to carry out the very complex dosimetric
Introduction
One third of people in Britain will develop cancer at some time during their lives and about half are cured. Opportunities for active treatment are increasing, with improvements in radiotherapy and chemotherapy and the development of novel biological and molecular treatment approaches. Of all cancer patients - 22% are cured by surgery, 18% by radiotherapy and 5% by chemotherapy alone or in combination with surgery or radiotherapy. Radiotherapy remains the most effective nonsurgical treatment modality forming a central provision of treatment in Cancer Centres and is solely responsible for or significantly contributes to cure in 40% of the long-term survivors of cancer. 40-45% of all cancer patients will require radiotherapy …show more content…
This minimises the risk of a geographical miss that may compromise tumour control and increase surrounding normal tissue damage. To help in this process various immobilisation devices are available, which include vacuum moulded bags of polystyrene beads, and foam blocks and wedges, which can be used for trunk and limb immobilisation. Higher degrees of precision are required for treatment of CNS and head and neck tumours due to the close proximity of critical structures such as the spinal cord, eyes and optic chiasm. This can be achieved with immobilisation devices such as custom made perspex/plastic moulded shells (masks) that can be fixed to the treatment …show more content…
These treatments have to be planned and will involve the physics department.
For more complex treatment (Level 3) planning, volumes are defined on a CT study at a graphics terminal. At this level, the GTV, CTV and PTV can be defined in one or more planes (sections), using a series of CT and/or MRI sections. It is also assumed that the complete dose distributions are computed in the central plane and in other planes (sections) and with inhomogeneity corrections, when appropriate.
The computer planning system can develop digitally reconstructed radiographs (DRRs) that give beams-eye-views of the radiation fields.
6. Dosimetry.
Dosimetry is calculation of the amount of radiation dose absorbed by the patient. Beam data for treatment units are available as depth dose charts that allow simple dose calculation For simple field arrangements (single fields and parallel opposed fields), it is assumed that the dose at the ICRU Reference Point and an estimate of the maximum and minimum doses to the PTV can be determined using central axis depth dose tables. Radical treatments often require multiple and complex field arrangements to achieve the optimum dose to the tumour with normal tissue sparing, and modern computer planning systems are required to carry out the very complex dosimetric