Brain Tumor – Preparations for radiation therapy
Brain Tumor – Preparations for radiation therapy, An exact therapy planning is necessary in order to apply a dose as high as possible in the region of the tumor and a dose as low as possible in the surrounding healthy tissue. As a result, the side effects are kept as low as possible with the best possible healing. Depending on tumor disease and their biological behavior, different preparations may be necessary.
1. Computer-assisted irradiation planning
In order to enable an optimal irradiation technique, it may be necessary to perform a computer tomography of the head, occasionally also of the spinal canal, beforehand. In this computed tomography care is taken that it is carried out exactly in the position as the subsequent irradiation. Therefore, at this time, the necessary aids (such as aids for storage such as head masks) are also prepared and adapted for each individual patient. Computer tomography is usually performed without an intravenous contrast medium, but depending on the question, it may also be necessary to add additional contrast media.
The main goal of computed tomography is to achieve a three-dimensional volume set for computer-assisted irradiation planning.By the computed physical density values are obtained with the aid of X-rays with which the physicist can calculate the dose distribution within the head or spinal cord channel accurately. Furthermore, the CT provides an accurate representation of the anatomical conditions, in individual cases, the tumor spread. The images of computerized treatment planning and the data contained therein are usually imported directly into the treatment planning computer. The radiation oncologist then draws a millimeter the desired target volume. Physician and physicist determine the cheapest array using the computer. At the same time, a precise calculation is achieved, ie the necessary exposure time to achieve the defined dose at a certain depth. Furthermore, the individual therapeutic fields can be modeled individually so that an exact adaptation to the selected target volume is reached. The therapeutic areas intersect at a defined point of intersection corresponds to the center of the rotation axis of the accelerator. This pivot point or intersection of the radiation is also called isocenter. The physical dose calculation, the array and the dose distribution are determined according to international standards, documented and usually checked by a second physicist. In this way, a security irradiation at a high level is guaranteed.
The so-called X-ray simulator corresponds to a device having the same geometric characteristics as the irradiation device. The device is rotated through 360 ° so that fields of therapy readjusted from different individual directions of irradiation (simulated) can be. Under fluoroscopic the region to be irradiated is then ( “target volume”) is set so that it optimally recorded and the environment is protected as much as possible. This method is now often replaced by a CT-based treatment planning.
Implementation of a computerized plan irradiation
was a computerized radiation treatment plan calculated, it is transmitted with the aid of fluoroscopy device on the mask. Typically, the location of the isocenter around which arrange the fields of therapy, is transmitted. For the exact transmission is located in a three-dimensional simulator laser system that tracks the location of this isocentre on the mask surface. This three-dimensional coordinate system makes precise positioning and defining the position of therapeutic areas. This laser system is also in each treatment room. In this way an exact positioning of the fields is achieved. During the simulation, be irradiated therapy fields are set under fluoroscopy and creates an X-ray image, a simulation film. Overall, the simulation of the most time-consuming part of the treatment for the patient and the staff of radiotherapy. Here custom work needs to be done requires patience. The radiation fields and the location of the isocenter are then marked the end of the simulation with special paint on the mask.
Irradiation documents and also the simulation films must be kept for 30 years for the details of the radiation therapy can be traced later if required at any time.
When irradiated neuro axis direct setting of therapeutic areas is usually carried out. The irradiation is in the prone position. The radiation treatment of the head 2 via lateral fields and the treatment of the spinal canal than 1 or 2 fields directly from the rear. Under fluoroscopy, the exact positioning of the fields of therapy can be determined. Then the documentation on simulation movies and the delineation of therapeutic areas on the plaster cast or on the skin of the back done. The additional overlay marks of the laser are also mounted and located. Today, computer-based radiation planning for the radiation treatment of the entire Liquorraumes are increasingly being used. Here, increasingly supine proven with a fixation of the head by the usual face mask.
In a detail has to pay particular
case of computerized treatment planning and simulation special markings are usually attached to the skin. These marks are necessary for the precise setting of therapeutic areas at the irradiation device and must not be removed. In most cases, they are covered with patches. These marks should not be washed off. If there is no marking necessary treatment planning must be repeated. Sometimes small dots are tattooed into the skin, this last a little longer and can not be removed by washing. But they are so small that they can only see an experienced eye.
Implementation of radiotherapy
The actual irradiation time per session is usually very short. The purely physical delivery of the dose per irradiation field is usually in seconds or minutes range. The vast time is needed for storage by adjusting the face mask or using other positioning aids and the setting of the radiation fields. The first radiation often requires the most time, as important control measures by the physicist and the doctor or the medical technical assistant are carried out in individual cases. For the first treatment planning and X-ray images are obtained with the therapeutic beam which verifications, which are reviewed on an individual basis prior to the administration of the first irradiation by a doctor or a physicist. Here, the currently applied therapy field is compared to the planned treatment field. Possibly.a fine adjustment of therapeutic areas may be necessary. Only after this process, the radiation from the physician and physicist is finally released. The details will be able to explain the medical staff.
Usually, irradiated 5 days per week. Irradiation is 1 x daily. In rare cases, it can also lead to two radiation treatments per day come ( “Hyperfractionation”). In some cases, fewer sessions per week can be applied. During irradiation series are conducted periodically checks the therapeutic areas with production of verification films.
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