Book contents
- Frontmatter
- Contents
- List of contributors
- Preface to the first edition
- Preface to the second edition
- Acknowledgements
- Abbreviations
- 1 Practical issues in the use of systemic anti-cancer therapy drugs
- 2 Biological treatments in cancer
- 3 Hormones in cancer
- 4 Pathology in cancer
- 5 Radiotherapy planning 1: fundamentals of external beam and brachytherapy
- 6 Radiotherapy planning 2: advanced external beam radiotherapy techniques
- 7 Research in cancer
- 8 Acute oncology 1: oncological emergencies
- 9 Acute oncology 2: cancer of unknown primary
- 10 Palliative|care
- 11 Management of cancer of the head and neck
- 12 Management of cancer of the oesophagus
- 13 Management of cancer of the stomach
- 14 Management of cancer of the liver, gallbladder and biliary tract
- 15 Management of cancer of the exocrine pancreas
- 16 Management of cancer of the colon and rectum
- 17 Management of cancer of the anus
- 18 Management of gastrointestinal stromal tumours
- 19 Management of cancer of the breast
- 20 Management of cancer of the kidney
- 21 Management of cancer of the bladder
- 22 Management of cancer of the prostate
- 23 Management of cancer of the testis
- 24 Management of cancer of the penis
- 25 Management of cancer of the ovary
- 26 Management of cancer of the body of the uterus
- 27 Management of cancer of the cervix
- 28 Management of cancer of the vagina
- 29 Management of cancer of the vulva
- 30 Management of gestational trophoblast tumours
- 31 Management of cancer of the lung
- 32 Management of mesothelioma
- 33 Management of soft tissue and bone tumours in adults
- 34 Management of the lymphomas and myeloma
- 35 Management of cancers of the central nervous system
- 36 Management of skin cancer other than melanoma
- 37 Management of melanoma
- 38 Management of cancer of the thyroid
- 39 Management of neuroendocrine tumours
- 40 Management of cancer in children
- Multiple choice questions
- Multiple choice answers
- Index
- References
6 - Radiotherapy planning 2: advanced external beam radiotherapy techniques
Published online by Cambridge University Press: 05 November 2015
- Frontmatter
- Contents
- List of contributors
- Preface to the first edition
- Preface to the second edition
- Acknowledgements
- Abbreviations
- 1 Practical issues in the use of systemic anti-cancer therapy drugs
- 2 Biological treatments in cancer
- 3 Hormones in cancer
- 4 Pathology in cancer
- 5 Radiotherapy planning 1: fundamentals of external beam and brachytherapy
- 6 Radiotherapy planning 2: advanced external beam radiotherapy techniques
- 7 Research in cancer
- 8 Acute oncology 1: oncological emergencies
- 9 Acute oncology 2: cancer of unknown primary
- 10 Palliative|care
- 11 Management of cancer of the head and neck
- 12 Management of cancer of the oesophagus
- 13 Management of cancer of the stomach
- 14 Management of cancer of the liver, gallbladder and biliary tract
- 15 Management of cancer of the exocrine pancreas
- 16 Management of cancer of the colon and rectum
- 17 Management of cancer of the anus
- 18 Management of gastrointestinal stromal tumours
- 19 Management of cancer of the breast
- 20 Management of cancer of the kidney
- 21 Management of cancer of the bladder
- 22 Management of cancer of the prostate
- 23 Management of cancer of the testis
- 24 Management of cancer of the penis
- 25 Management of cancer of the ovary
- 26 Management of cancer of the body of the uterus
- 27 Management of cancer of the cervix
- 28 Management of cancer of the vagina
- 29 Management of cancer of the vulva
- 30 Management of gestational trophoblast tumours
- 31 Management of cancer of the lung
- 32 Management of mesothelioma
- 33 Management of soft tissue and bone tumours in adults
- 34 Management of the lymphomas and myeloma
- 35 Management of cancers of the central nervous system
- 36 Management of skin cancer other than melanoma
- 37 Management of melanoma
- 38 Management of cancer of the thyroid
- 39 Management of neuroendocrine tumours
- 40 Management of cancer in children
- Multiple choice questions
- Multiple choice answers
- Index
- References
Summary
Introduction
Recent advances in technology have enabled more complex radiotherapy to be delivered routinely and the use of stereotactic or modulated techniques have become standard for many indications. These developments allow the radiation dose to conform more closely to the planning target volume (PTV) while more effectively avoiding normal tissue. This can allow the dose to be escalated without increasing the risks of normal tissue toxicity.
Some of these techniques require specialised machines, described later in the chapter, and recently there has also been interest in modifying conventional linear accelerators to achieve the same aim. For instance, the increased use of cranial stereotactic techniques for both malignant and non-malignant indications has led both to an increase in specific machines and to the development of linear accelerators which deliver advanced radiotherapy to both cranial and extracranial sites. Rotational therapy, a technique that was used by some centres in the 1960s, has been ‘rediscovered’ and, when combined with the modulated techniques of conventional intensity-modulated radiotherapy (IMRT), has led volumetric-modulated adaptive therapy (VMAT), delivering radiation in a way similar to tomotherapy.
Advances in imaging have also contributed to radiotherapy development. For example, use of pretreatment MRI or PET scans can help to define planning target volumes, and cone beam CT scans during treatment can check on internal organ movement and set-up accuracy. The ability to ‘fuse’ these images with the CT planning scan has greatly assisted both radiotherapy planning and treatment delivery.
Intensity-modulated radiation therapy
Introduction
IMRT is a technique which uses beams that, unlike the flat or wedged beams of conventional RT, have changing dose intensity across them, as shown in Figure 6.1 (Webb, 2003; Bortfeld, 2006). Modulation was originally produced by using low melting point compensators, but is now usually generated by moving the multi-leaf collimators (MLCs) during ‘beam on’ time. The aim of this is to build up the desired dose distribution by producing appropriately modulated beams.
The basic principle of IMRT can be seen in Figure 6.2, which shows three modulated beams to cover a PTV with an isodose distribution that wraps around the organ at risk (OAR) and conforms well to the target volume. In practice more beams, usually between 5 and 9, are needed to give an acceptable distribution.
- Type
- Chapter
- Information
- Practical Clinical Oncology , pp. 70 - 79Publisher: Cambridge University PressPrint publication year: 2015
References
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