Radiotherapy

Radiotherapy is one of the methods of radiation therapy, in which with the purpose of treatment is used x-rays with energies from 10 to 250 square With increasing voltage on x-ray tube increases the radiation energy and with it its penetrating power in the tissues increases from a few millimeters to see 8-10
Modern industry produces two types rentgenoterapevticheskie AIDS. One for the short-focus x-ray therapy with radiation energy from 10 to 60 kV for irradiation with small distances (up to 6-7 .5 cm) superficial pathological processes of the skin and mucous membranes. Other for deep x-ray therapy with radiation energy from 100 to 250 kV for irradiation from a distance of from 30 to 60 cm deep located pathological foci. X-ray radiation in the x-ray tube, always heterogeneous in its energy. For a more or less homogeneous beam use filters that absorb soft rays. For low-energy radiation apply the filters from light metals (aluminum, brass thickness 0,5-1 - 3 mm). For radiation high energy (180-200 kV) uniformity of radiation is achieved by using filters of heavy metals (zinc, copper thickness of 0.5-2 mm). To limit field exposure and convenience centration when radiotherapy is used cylindrical or rectangular tubes, providing necessary for each individual patient's skin and focal length. The output window tubes devices for short-focus x-ray therapy also has a diameter of up to 5 cm, and for the deep space 16-225 cm2. The short-focus x-ray treatments successfully used in the treatment of skin cancer, cancer of the upper and lower lips I and II stages of the disease, but at a higher distribution process combined with Curie-therapy or remote methods of radiation therapy. The short-focus x-ray treatments in combination with remote sensing is used for the treatment of both early and more common cancers of the oral mucous cavity, cervical cancer, colon cancer. The short-focus x-ray treatments can be applied during the operation in early cancers of the bladder, larynx, stomach.
Radiotherapy at a voltage from 160 to 250 kV 50-ies of our century was the only method of remote radiation deeply located pathological processes as inflammatory and dystrophic, and malignant tumors. In cancer of the internal organs characterized by low radiosensitivity and requiring for their destruction of large doses of radiation (within 6000-7000 rad), radiotherapy proved ineffective. Several best results can be obtained with x-ray therapy through lead grid, which can increase the focal dose and reduce the radiation dose to normal tissue.
Currently in the treatment of deep tumors radiotherapy replaced remote gamma-therapy, the use of the bremsstrahlung and electron radiation high energy. Radiotherapy can be used in the treatment of radiosensitive tumors (Ewing sarcoma, chlamydia, retikulosarkoma). Good results were obtained when the therapy of acute inflammatory processes, while using small doses of the order of 10-15 happy and total dose of not more than 100 rad.

X - ray therapy is the medical discipline that studies the theory and practice of application of x-ray radiation for therapeutic purposes. Is a private section of radiation therapy (see).
The use of radiotherapy began in 1897, but the scientific basis radiotherapy received only with the development of physics, dosimetry, radiobiology and the accumulation of clinical experience.
There are x-ray treatments distance (the distance of the focus skin of 30 cm and more) and close-focus (focus distance - skin does not exceed 7.5 cm). In turn remote radiotherapy can be implemented as a static irradiation (x-ray tube and the patient during irradiation fixed and mobile radiation (x-ray tube or a patient is in a state of relative motion).
Numerous forms of static and mobile x-ray irradiation. Can vary the various elements of the irradiation conditions, beam quality, the distance of the focus skin or the radius of the swing, the number of fields or swing angle, size, shape and number of fields or radiation areas, of single or cumulative dose of radiation, the rhythm of radiation, dose rate, and so on
X-rays generated in the x-ray tubes using high-voltage electric apparatus (see X-ray machines), the effects on tissues and organs of the human body causes suppression of individual cells, suppression of growth, and in some cases their destruction. These phenomena are a consequence of the absorption and scattering - the primary physical processes of interaction of x-ray radiation with biological environment (see diagram).
For primary physical followed by a physical-chemical and biochemical processes that determine the development of therapeutic effect. Characteristic x-ray radiation is its continuous energy spectrum, which are quanta of radiation with any energies, up to the maximum, corresponding to the highest voltage generation. The latter currently in therapy usually does not exceed 250 square
On the energy spectrum of the working radiation beam is affected by the characteristics and scheme rentgenoterapevticheskie apparatus, type the supply of electric power, design and materials rentgenoterapevticheskie tube, as well as further filtering.
For rational therapy, it is important to use the basic physical characteristics of the distribution of x-ray radiation: the law of the inverse square of the distance and the pattern of absorption of radiation in matter. The latter is characterized by the linear attenuation coefficient and depends on chemical composition, density, and energy. Each component of the energy spectrum in the interaction with a given substance is changing in different ways. Therefore, along with the weakening of the x-ray beam is changed and its qualitative composition. Quality assessment (penetrating) working x-ray beam used for remote radiation therapy provides a layer half of weakening (D) and is expressed in mm of layer thickness inhibiting substances (lead, copper, aluminum and others).
When close-focus x-ray therapy with the use of soft radiation such quality assessment is performed by defining a layer half dose (SPD) and is measured in millimeters of thickness of a layer of cloth, which covered the radiation.
The most important physical factor affecting the value of absorbed doses in radiotherapy, is scattered radiation. The contribution of scattered radiation depends on the irradiation conditions - size surface of the field, the distance of the focus skin and energy radiation.
The therapeutic effect of the therapy is associated with absorbed dose in the pathological focus. The optimal value of the absorbed dose, its fragmentation, rhythm exposure due in each case, the nature of the pathological process. On the degree of concomitant reactions of others pathological focus healthy tissues and organs, as well as reactions of the whole organism is affected by the value of the integral doses in these individual anatomical structures in the whole body of the patient.
Effects of radiotherapy is not unique to different histological structures that are associated with various sensitivity ionizing radiation (see Radiobiology).
However, the sensitivity of irradiated tissues in the human body depends on numerous other factors - age, sex, body temperature and irradiated site, localization, hydrophilicity, blood flow, oxygen saturation, its functional activity, the intensity of metabolic processes and mn. others, including from its original condition, and the reactivity of the organism. On the biological effects of x-ray therapy also affects the character of distribution of radiation dose in time. Fractional irradiation in comparison with the single is less damaging. In this case, it helps to reveal the differential sensitivity of tissues and the so-called therapeutic interval - the difference in the sensitivity of normal and pathological histostructure.
Radiotherapy can cause various effects. Depending on the value of the absorbed dose of radiation, rhythm exposure, the object of impact, nature and stage of the disease and, finally, the reactivity of the organism of the patient may have anti-inflammatory and desensitization, destructive, analgesic, and other effects.
Although General regularities of biological action of ionizing radiation is rather well investigated, but some parts of this complex process (interaction of radiation with pathologically changed tissues) is still unclear. In particular, requires further study the changing nature of cellular reactions, intermediario exchange, developing antibodies, reactivity of connective tissue and mn. other
For the last time with the deepening of knowledge of biological action of ionizing radiation has been the desire to limit the application of radiotherapy of oncological practice. For nonneoplastic diseases radiotherapy is recommended only in the early stages of acute inflammatory diseases and in the absence of other equivalent means of treatment or the ineffectiveness of the last in persons older than 40 years. For nonneoplastic diseases in children x-ray treatments should not be used.
Radiotherapy should be applied only when there is scientific evidence for such treatment and only in patients with perfectly vindicated disease. "With rare exception to this rule can only serve some borderstone tumors of the mediastinum, when radiotherapy should be used as the only involuntary emergency decompression method of influence on vital thoracic cavity organs" (C. A. Reinberg).
In the appointment of therapy is necessary to clearly formulate on the basis of clinical data, a task that must be solved radiation therapy. Delivered
the mission determines the method, the technique therapy, the size of the dose. Must be the choice of x-ray radiation among other types of ionizing radiation. The latter is done by analyzing the depth of pathological focus dose of fields, created by radiation with different energies by different types of radiation. Depending on the nature, form, size, location and stage of the pathological process, as well as the status of surrounding tissues and the General condition of the body the plan of conducting the therapy.
Calculated absorbed doses of radiation in the focus during the procedure, the session, the entire course of treatment, and accordingly admissible surface radiation doses, are determined by the size, number and location of the fields or radiation areas, conditions centering and formation of the beam that rhythm irradiation and other
Holding of a session of therapy should be preceded by: 1) precise localization and identification of the size of the pathological education and the application of its projection on the skin; 2) adjustment of the x-ray irradiation of the patient; 3) the focus of the beam. During a session of therapy is necessary to continually monitor the correct execution of the given program irradiation by direct visual observation or by means of special devices.
A common requirement of radiation therapy is to obtain a positive result at minimal damage to surrounding pathological focus healthy tissue.
The cause of many of radiation damage in the form of trophic ulcers, atrophy of the tissues and others (see Radiation damage), sometimes taking place during radiotherapy is ignoring this requirement.
In connection with the extension of possibilities of using high-energy sources of radiation therapy used mainly in relatively shallow location of a pathological focus, and if possible use of small doses of radiation.
X-ray treatments used independently or as part of the combined (surgery), complex (with the chemotherapy) or combined (with other types of radiation treatment (see Radiation therapy). As a rule, it should be complemented next concomitant therapy (blood transfusion, vitamin therapy, medication, hormone therapy and others).
Remote radiotherapy indicated for round-cell sarcomas, especially when lymphosarcoma, of lymphoepithelial masses and reticuloendothelial tumors early stages of cancer of the vocal cords; close-focus RV - for skin cancer, squamous cell cancer of mucous membranes, primary malignant melanomas. Optimal total absorbed dose, depending on the character and localization of tumors, as well as some other factors may vary between 3000 to 12 000 happy. One-absorbed doses more often amount to 150-200 happy. When close-focus R. they are approximately two times higher. Rhythm of irradiation depending on the nature of the tumor may be different.
When radiotherapy of non-neoplastic diseases single dose in the focus should not exceed 25-80 glad, and the interval between exposures - 3-7 days. More acute inflammatory process requires less time and the total dose and longer intervals between exposures. Sometimes it is enough 1-2 exposures to ensure resolving effect or to stimulate abstsedirovanie. In subacute and chronic processes using high doses and a slightly shorter interval between exposures. The total absorbed dose and the number of sessions irradiation are determined by the course of the disease. Usually spend 4-6 exposures.
The reaction of the organism (see Radiation sickness) when conventional radiotherapy, as a rule, is more pronounced than when exposed to radiation at higher energies. Sometimes these radiation reaction becomes severe complication requiring special treatment. The severity of reactions often serves as a criterion when assessing the advantages or disadvantages of different options R.

  • Radiotherapy in children