Handbook of Radiotherapy Physics - Theory and Practice - Taylor & Francis ( ) In order to cover in detail all aspects of radiotherapy physics and biology , Publishing, Madison, WI, , tvnovellas.info . Handbook of Radiotherapy Physics Theory and Practice - Ebook download as PDF File .pdf), Text File .txt) or read book online. radiotherapy physics. From background physics and biological models to the latest imaging and treatment modalities, the Handbook of Radiotherapy Physics: Theory and Practice covers. DownloadPDF MB Read online. From background.
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HANDBOOK OF RADIOTHERAPY PHYSICS: THEORY AND PRACTICE IAEA, Vienna, (tvnovellas.info Handbook of Radiotherapy Physics, Theory and Practice CRC Press This Document PDF may be used for research, teaching and private. Handbook of Radiotherapy Physics: Theory and Practice | 𝗥𝗲𝗾𝘂𝗲𝘀𝘁 𝗣𝗗𝗙 on ResearchGate | On Jan 1, , P. Mayles and others published Handbook of.
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America in the s and subsequently via the computer-controlled multileaf collimator [ 4 ].
More generally, a vastly increased number of degrees of freedom in the inverse planning process were now available.
And the onward march of technology shows no signs of abating. With very few exceptions, strict protocols are followed. These specify for a given tumour type the precise radiation dose that shall be delivered, within tightly defined uniformity limits e. The above dose-escalation strategy has resulted in some modest gains in local control rates, particularly for intermediate- and late-stage prostate tumours [ 16 ] for no increase or even decreases in principally rectal complication rates.
But as will be demonstrated in what follows, a rigid predefined dose prescription will lead to underdosage in some patients and to adverse effects from overdosage in others [ 17 ].
Materials and Methods 2. Radiobiological Models for TCP and NTCP Models for estimating the probability of tumour local control TCP and of normal-tissue complication NTCP were first proposed in the second half of the s and the first half of the s see [ 18 ] for a useful summary of the various models and associated references.
By definition these best-fit parameters make the models reproduce the clinical data points they were fitted to, but the associated confidence intervals are usually fairly wide. The source of this sometimes large uncertainty may reside in the functional form of the model but also in the nature of the data and the way they are reported.
However, it should be borne in mind that uncertainty is intrinsic to radiotherapy treatments; for example, meeting normal tissue dose criteria is not a guarantee against the occurrence of a complication.
To some extent, biological models are also subject to this uncertainty. All the radiobiological evaluations given in this paper should be understood as estimates based on the best-fit parameters available today. It is emphasized that the current TCP, NTCP models are hybrid in nature; they apply to the individual patient's dose distribution, expressed in terms of dose-volume histograms DVHs , but to the population-averaged patient biology.
The currently used NTCP models also involve population-averaged biology though this is generally implicit rather than explicit in their mathematical form. Certain radiobiological models are wholly or partly mechanistic e. In all cases, some assumptions are explicitly or implicitly made so as to render the problem of predicting the outcome of radiotherapy mathematically manageable.
For example, the LKB model considers all volume elements of a particular organ to have the same importance for the function of this organ.
It is the most commonly reported complication in breast radiation therapy patients who receive adjuvant axillary radiotherapy following surgery to clear the axillary lymph nodes. Cancer survivors are already more likely than the general population to develop malignancies due to a number of factors including lifestyle choices, genetics, and previous radiation treatment.
It is difficult to directly quantify the rates of these secondary cancers from any single cause. Studies have found radiation therapy as the cause of secondary malignancies for only a small minority of patients. In the vast majority of cases, this risk is greatly outweighed by the reduction in risk conferred by treating the primary cancer.
Cardiovascular disease Radiation can increase the risk of heart disease and death as observed in previous breast cancer RT regimens. Radiation-induced fibrosis, vascular cell damage and oxidative stress can lead to these and other late side effect symptoms.
Cognitive decline was especially apparent in young children, between the ages of 5 to Studies found, for example, that the IQ of 5-year-old children declined each year after treatment by several IQ points. Pelvic radiation disease includes radiation proctitis , producing bleeding, diarrhoea and urgency,  and can also cause radiation cystitis when the bladder is affected.
Radiation-induced polyneuropathy Radiation treatments are vitally necessary but may damage nerves near the target area or within the delivery path as nerve tissue is also radiosensitive. In the CNS for example, cranial nerve injury typically presents as a visual acuity loss years post treatment. Effects on reproduction[ edit ] During the first two weeks after fertilization , radiation therapy is lethal but not teratogenic.
However, mistakes do occasionally occur; for example, the radiation therapy machine Therac was responsible for at least six accidents between and , where patients were given up to one hundred times the intended dose; two people were killed directly by the radiation overdoses.
From to , a hospital in Missouri overexposed 76 patients most with brain cancer during a five-year period because new radiation equipment had been set up incorrectly. ASTRO has launched a safety initiative called Target Safely that, among other things, aims to record errors nationwide so that doctors can learn from each and every mistake and prevent them from happening. ASTRO also publishes a list of questions for patients to ask their doctors about radiation safety to ensure every treatment is as safe as possible.
When Dupuytren's disease is at the nodules and cords stage or fingers are at a minimal deformation stage of less than 10 degrees, then radiation therapy is used to prevent further progress of the disease.
Radiation therapy is also used post surgery in some cases to prevent the disease continuing to progress.
Low doses of radiation are used typically three gray of radiation for five days, with a break of three months followed by another phase of three gray of radiation for five days. This DNA damage is caused by one of two types of energy, photon or charged particle.
This damage is either direct or indirect ionization of the atoms which make up the DNA chain. Indirect ionization happens as a result of the ionization of water, forming free radicals , notably hydroxyl radicals, which then damage the DNA. In photon therapy, most of the radiation effect is through free radicals.
However, double-stranded DNA breaks are much more difficult to repair, and can lead to dramatic chromosomal abnormalities and genetic deletions.
Targeting double-stranded breaks increases the probability that cells will undergo cell death. Cancer cells are generally less differentiated and more stem cell -like; they reproduce more than most healthy differentiated cells, and have a diminished ability to repair sub-lethal damage.
Single-strand DNA damage is then passed on through cell division; damage to the cancer cells' DNA accumulates, causing them to die or reproduce more slowly. One of the major limitations of photon radiation therapy is that the cells of solid tumors become deficient in oxygen.
Solid tumors can outgrow their blood supply, causing a low-oxygen state known as hypoxia. Oxygen is a potent radiosensitizer , increasing the effectiveness of a given dose of radiation by forming DNA-damaging free radicals.
Tumor cells in a hypoxic environment may be as much as 2 to 3 times more resistant to radiation damage than those in a normal oxygen environment. Newer research approaches are currently being studied, including preclinical and clinical investigations into the use of an oxygen diffusion-enhancing compound such as trans sodium crocetinate TSC as a radiosensitizer.
Due to their relatively large mass, protons and other charged particles have little lateral side scatter in the tissue—the beam does not broaden much, stays focused on the tumor shape, and delivers small dose side-effects to surrounding tissue.
They also more precisely target the tumor using the Bragg peak effect. See proton therapy for a good example of the different effects of intensity-modulated radiation therapy IMRT vs. This procedure reduces damage to healthy tissue between the charged particle radiation source and the tumor and sets a finite range for tissue damage after the tumor has been reached.
In contrast, IMRT's use of uncharged particles causes its energy to damage healthy cells when it exits the body. This exiting damage is not therapeutic, can increase treatment side effects, and increases the probability of secondary cancer induction. Many other factors are considered by radiation oncologists when selecting a dose, including whether the patient is receiving chemotherapy, patient comorbidities, whether radiation therapy is being administered before or after surgery, and the degree of success of surgery.
Delivery parameters of a prescribed dose are determined during treatment planning part of dosimetry. Treatment planning is generally performed on dedicated computers using specialized treatment planning software. Depending on the radiation delivery method, several angles or sources may be used to sum to the total necessary dose.
The planner will try to design a plan that delivers a uniform prescription dose to the tumor and minimizes dose to surrounding healthy tissues.
In radiation therapy, three-dimensional dose distributions may be evaluated using the dosimetry technique known as gel dosimetry. Fractionation allows normal cells time to recover, while tumor cells are generally less efficient in repair between fractions. Fractionation also allows tumor cells that were in a relatively radio-resistant phase of the cell cycle during one treatment to cycle into a sensitive phase of the cycle before the next fraction is given.
Similarly, tumor cells that were chronically or acutely hypoxic and therefore more radioresistant may reoxygenate between fractions, improving the tumor cell kill. In North America, Australia, and Europe, the typical fractionation schedule for adults is 1. In some cancer types, prolongation of the fraction schedule over too long can allow for the tumor to begin repopulating, and for these tumor types, including head-and-neck and cervical squamous cell cancers, radiation treatment is preferably completed within a certain amount of time.
For children, a typical fraction size may be 1. In some cases, two fractions per day are used near the end of a course of treatment. This schedule, known as a concomitant boost regimen or hyperfractionation, is used on tumors that regenerate more quickly when they are smaller.
In particular, tumors in the head-and-neck demonstrate this behavior. Patients receiving palliative radiation to treat uncomplicated painful bone metastasis should not receive more than a single fraction of radiation. This is a radiation treatment in which the total dose of radiation is divided into large doses. Typical doses vary significantly by cancer type, from 2. The rationale of hypofractionation is to reduce the probability of local recurrence by denying clonogenic cells the time they require to reproduce and also to exploit the radiosensitivity of some tumors.