Methodical Instruction of practical lesson №3 Theme: Principles and methods of radial therapy icon

Methodical Instruction of practical lesson №3 Theme: Principles and methods of radial therapy




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Methodical Instruction of practical lesson № 3

Theme: Principles and methods of radial therapy.


I. Actuality of theme:

Knowledge of possibilities, indications and contra-indications for of different methods of radial therapy will help correctly to choose tactic of medical treatment of oncologic patients. In an oncologic clinic there are three basic variants of medical treatment are applied: radial, surgical, chemotherapy. A radial method can be used both independently, and in combination with the other methods of medical treatment


ІІ. Training purpose:

2.1. A student must know:

  • kinds and sources of ionizing radiations, that are used in practice of radial therapy;

  • clinical dosimetry, units, types of doses and value of dosimetry in radial therapy of different diseases;

  • kinds, methods of radial therapy;

  • possibilities and principles of radial therapy.


2.2 To Be Able:

  • to determine the indications and contra-indications for radial therapy of malignant tumours and untumular diseases;

  • to use data of clinical and roentgenologic topometry during the gamma-therapy controlled from distance;

  • principles of planning of course of radial therapy on the model of malignant tumours of mouth cavity, larynx, etc.


ІІІ. Educational purpose:
  • ^

    to pay attention to importance of deontological, ethics moments of radiotherapy of oncological patients;

IV. Intersubject integration.





The name of discipline and proper department

To Know

To Be Able

Physiology (department of normal and pathological physiology)

Metabolic processes in a mew, physiology of exchange of matters and crovotvorennya

To be able to determine the pathological changes in the organism coased by radiation

Topographical anatomy

Anatomy of organs, their topography

To project a location of organ on body surface
^

V. Plan and organization of practical lesson


5.1. Duration of lesson - 2 hours.

5.2. Stages of lesson (table):



№ p.p.

Basic stages of lesson

Educational purpose in the levels of mastering

Methods of control

Time

1.

Preparatory stage:

-organization of lesson;

-determination of educational purpose and motivation;

-control of initial level of knowledges, abilities and skills;


^ L = II-III

Frontal questioning, test control (sets of tests).

15
min.

2.

Basic stage:

forming of professional abilities and skills:;

б) a teacher explains dependence the dose on the depth of of tumours and their histological structure.

в) in the department of radial therapy students acquaint themself with devices using for radial therapy .


L= ІІІ

In written form, to name:

  1. types of radial therapy;

  2. methods of radial therapy;

  3. methods of radiation;

  4. basic principles of radial therapy.




60 min.

3.

Final stage:

- control and correction of level of professional skills and knowledges;

- general result of lesson;

- homework.


L= ІІІ


L = ІІ


Individual control of results of writing works.

Solution of tests.

Tests and standards of answers.

15 min.


5.2.1. Preparatory stage:

At the beginning of lesson a teacher acquaints students with the basic tasks of lesson, plan. For the control of initial level of knowledges of students to each of them the list of tests is offered. The analysis of basic properties of ionizing radiation is conducted.


^

5.2.2. Basic stage:


  • Forming of professional abilities and skills in radial therapy, sources of radiation and methods of radiation ; possibilities and principles of radial therapy;

  • A teacher explains the basic tasks and principles of radial therapy concerning tumours, radiobialogical basis, kinds and sources of radiations, principles of clinical dosimetry, kinds, methods of radial therapy, methods of radiation, construction of topometry cards.

  • In the department of the radial therapy controlled from distance students acqaint themself with the structure of department, anti-radial defence, work of the gamma-therapeutic equipment. "AGAT –R1u", determination of time of radiation for doses valid for one procedure.


Radiation therapy (or radiotherapy) is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). Radiotherapy may be used for curative or adjuvant cancer treatment. It is used as palliative treatment (where cure is not possible and the aim is for local disease control or symptomatic relief) or as therapeutic treatment (where the therapy has survival benefit but is not curative). Total body irradiation (TBI) is a radiotherapy technique used to prepare the body to receive a bone marrow transplant. Radiotherapy has a few applications in non-malignant conditions, such as the treatment of trigeminal neuralgia, severe thyroid eye disease, pterygium, prevention of keloid scar growth, and prevention of heterotopic ossification. The use of radiotherapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers.

Radiotherapy is commonly used for the treatment of malignant tumors (cancer), and may be used as the primary therapy. It is also common to combine radiotherapy with surgery, chemotherapy, hormone therapy or some mixture of the three. Most common cancer types can be treated with radiotherapy in some way. The precise treatment intent (curative, adjuvant, neoadjuvant, therapeutic, or palliative) will depend on the tumour type, location, and stage, as well as the general health of the patient.

Radiation therapy is commonly applied to the tumour. The radiation fields may also include the draining lymph nodes if they are clinically or radiologically involved with tumour, or if there is thought to be a risk of subclinical malignant spread. It is necessary to include a margin of normal tissue around the tumour to allow for uncertainties in daily set-up and internal tumor motion. These uncertainties can be caused by internal movement (for example, respiration and bladder filling) and movement of external skin marks relative to the tumour position.

To spare normal tissues (such as skin or organs which radiation must pass through in order to treat the tumour), shaped radiation beams are aimed from several angles of exposure to intersect at the tumour, providing a much larger absorbed dose there than in the surrounding, healthy tissue.

Dosage


The amount of radiation used in radiation therapy is measured in gray (Gy), and varies depending on the type and stage of cancer being treated. For curative (radical) cases, the typical dose for a solid epithelial tumor ranges from 60 to 80 Gy, while lymphoma tumors are treated with 20 to 40 Gy. Preventative (adjuvant) doses are typically around 45 - 60 Gy in 1.8 - 2 Gy fractions (for Breast, Head and Neck cancers respectively.) Many other factors are considered by radiation oncologists when selecting a dose, including whether the patient is receiving chemotherapy, whether radiation therapy is being administered before or after surgery, and the degree of success of surgery.

Fractionation


The total dose is fractionated (spread out over time) in order to give normal cells time to recover. In the USA and Europe, the typical fractionation schedule for adults is 1.8 to 2 Gy per day, five days a week. In the northern United Kingdom, fractions are more commonly 2.67 to 2.75 Gy per day, which eases the burden on thinly spread resources in the National Health Service. For children, a typical fraction is 1.5 to 1.7 Gy per day, reducing the chance and severity of late-onset side effects.

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 and/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.

One of the best-known alternative fractionation schedules is Continuous Hyperfractionated Accelerated Radiotherapy (CHART). CHART, used to treat lung cancer, consists of three smaller fractions per day. Although reasonably successful, CHART can be a strain on radiation therapy departments.

Implants can be fractionated over minutes or hours, or they can be permanent seeds which slowly deliver radiation until they become inactive.
^

Mechanism of action


Radiation therapy works by damaging the DNA of cells. The damage is caused by a photon, electron, proton, neutron, or ion beam directly or indirectly ionizing 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 the most common forms of radiation therapy, most of the radiation effect is through free radicals. Because cells have mechanisms for repairing DNA damage, breaking the DNA on both strands proves to be the most significant technique in modifying cell characteristics. Because cancer cells generally are undifferentiated and stem cell-like, they reproduce more, and have a diminished ability to repair sub-lethal damage compared to most healthy differentiated cells. The DNA damage is inherited through cell division, accumulating damage to the cancer cells, causing them to die or reproduce more slowly. Proton radiotherapy works by sending protons with varying kinetic energy to precisely stop at the tumor.

One of the major limitations of radiotherapy is that the cells of solid tumors become deficient in oxygen. This is because solid tumours usually outgrow their blood supply, causing a low-oxygen state known as hypoxia. The more hypoxic the tumours are the more resistant they are to the effects of radiation because oxygen makes the radiation damage to DNA permanent. Much research has been devoted to overcoming this problem including the use of high pressure oxygen tanks, blood substitutes that carry increased oxygen, hypoxic cell radiosensitizers such as misonidazole and metronidazole, and hypoxic cytotoxins, such as tirapazamine. There is also interest in the fact that high LET particles such as carbon or neon ions may have an antitumour effect which is independent of tumour hypoxia.
^

History of radiation therapy


Radiation therapy has been in use as a cancer treatment for more than 100 years, with its earliest roots traced from the discovery of x-rays in 1895.[2] The concept of therapeutic radiation was invented by German physicist Wilhelm Conrad Rontgen when he discovered that the x-ray was a powerful and effective tool with which to treat cancer.

The field of radiation therapy began to grow in the early 1900s largely due to the groundbreaking work of Nobel Prize-winning scientist Marie Curie, who discovered the radioactive elements polonium and radium. This began a new era in medical treatment and research.[2]. Radium was used in various forms until the mid-1900s when cobalt and caesium units came into use. Medical linear accelerators have been developed since the late 1940s.

With Godfrey Hounsfield’s discovery of computed tomography (CT), three-dimensional planning became a possibility and created a shift from 2-D to 3-D radiation delivery; physicians and physics were no longer limited because CT-based planning allowed physicians to directly measure the dose delivered to the patient's anatomy based on axial tomographical images. Orthovoltage and cobalt units have largely been replaced by megavoltage linear accelerators, useful for their penetrating energies and lack of physical radiation source.

In the last few decades, the advent of new imaging technologies, e.g., magnetic resonance imaging (MRI) in the 1970s and positron emission tomography (PET) in the 1980s, as well as new radiation delivery and visualization products, e.g., digital linear accelerator, image fusion has moved radiation therapy from 3-D conformal to IMRT and eventually to IGRT (4-D) in the near future. These advances have resulted in better treatment outcomes and less side effects. Now 70% of cancer patients receive radiation therapy as part of their cancer treatment.


5.3. Control questions to the theme of lesson:

1. Radio-biological basics of radial therapy.

2. Kinds and sources of ionizing radiation, that is used in practice of radial therapy.

3. Basics and principles of clinical dosimetry.

4. Kinds and principles of radial therapy, methods of radiation.

5. Basic principle, indications and contra- of the gamma-therapy controlled from distance.

6. Value of clinical topomethry in preparation of patients to radial therapy.

7. Principles of planning of radial therapy of patients with the malignant tumours of mouth cavity, larynx, etc.


5.4. Final stage.

The control of solution of tasks and eventual level of knowledges is conducted by their verification and raising of questions of practical direction. Rating of mastering the material of theme is depends on theoretical knowledges, practical skills, independent work of studrnt.

In a result a teacher considers typical errors which are assumed by students at implementation of self-education work and assigns to a next lesson. A teacher sets the homework, recommends literature after the theme of the following lesson^: basic and additional.


VІ. Materials for the methodical providing of lesson.


^ 6.1. Place of conducting of lesson: class room, department of radial therapy.


6.2. Material providing of lesson:

Tables:

  • types of radial therapy;

  • methods ofrradiation;

  • principles of planning of radial therapy at patients with the malignant tumours of uterus.


^ 6.3. Materials of control of basic (initial level) preparation of students

Tests for determination of initial level of knowledges

1. The types of radial therapy are determined after:

а) methods of radial defence;

б) types of ionizing radiation;

в) indication for radial therapy;

г) methods of radiation;


2. The methods of radial therapy are determined after:

а) methods radial defence;

б)types of ionizing radiation;

в)indications for radial therapy;

г)methods of radiation.


3.Basic principle of radial therapy of malignant tumors consists in:

а) concentration of optimum dose in a tumor without consideration of dose on healthy tissues;

б) concentration of optimum dose into on a tumour at a minimum dose on healthy tissues;

в) at a minimum dose on a tumor and healthy tissues.


4. The choice of general i dose at malignant tumours depends on:

а) concomitant disease;

б) histological diagnosis;

в) type of radiation;

г) method of radil therapy.


6. A dose for one session depends on:

а) histological structure of tumour;

б) localizations;

в) sizes;

г) sensitiveness of tumour to radiation;

д) sensitiveness of healthy tissues to radiation.


7. The size of the field of radiation depends on:

а) histological structure of tumour;

б) localizations;

в) sizes;

г) character of contours.


8. The quantity of the fields depends on:

а) histological structure of tumour;

б) sizes;

в) localizations;

г) general dose;


9. Distance from a source to the surface of radiation depends on:

а) sizes of tumour;

б) histological structure;

в) depths of location;

г) methods of radiation;

д) dose for one procedure;

е) general dose.


10. The distance method of radial therapy is executed at is a source - surface distance:

а) to 10 cm;

б) to 30 cm;

в) more than 30 cm.


VІІ. Literature



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