Radiation brain surgery and fractioned stereotactic radiotherapy. Introduction In general, oncologists have three weapons to fight against cancer: surgery, drugs chemotherapy, immunotherapyand radiation therapy.
We have the same possibilities for the treatment of intracranial tumours, but because of certain specialties of the central nervous system, the above-mentioned armamentarium is modified: The brain is locked into a rigid cave, thus growing of even benign tumours can cause life-threatening conditions because of the space occupation.
The damage of major portions of the brain is not compatible with life, or it results in significant deterioration of the quality of life. As a result of the blood-brain barrier system, prostate volume normal radiopaedia majority of classical chemotherapeutic drugs will not reach the cancer cells in a proper concentration.
Полип выглядел взволновано, и постоянные колебания его дыхательного аппарата прервались на несколько секунд. Затем он ответил, не вполне справляясь со своей речью: - Многие годы мы обсуждали эту проблему. Но мы не можем покинуть Шалмирану. Значит, мир должен придти к нам, как много времени это бы ни отняло. - У меня есть лучшая идея, - сказал Элвин нетерпеливо.
On the other hand in some cases, chemotherapeutic agents are administered in the CSF to fight against cancer spreading via the CSF pathways. Due to the fact that the majority of CNS cells do not divide, radiation therapy using the difference in sensitivity of normal and cancer cells against radiation can effectively be applied prostate volume normal radiopaedia the treatment of intracranial targets.
Consequently, radiation therapy has become the most important and the most widely used tool in place of inoperable tumour or beside residual tumour or cavity surgery for a local control. Furthermore, the radiosensitivity of different brain areas is considerably different: e. The rigidity of the scull, and the minor dislocation of the brain in the cranium make it possible to modify classical radiotherapy techniques when treating intracranial targets: Brain can be fixed through the scull with a precision of tenth of a millimeter… Thus we consider a little brain tissue dislocation the security margins of general radiation therapy and consequently the degree of radiation load to normal tissue can be lowered.
In this chapter radiation therapy radiosurgery and fractionated stereotactic radiation therapy of the CNS mainly for intracranial targets is discussed. First of all, the bases of fractionated radiation therapy are shown, then radiosurgery, fractionated stereotactic radiation therapy and the prostate volume normal radiopaedia diseases are discussed.
Basic concepts 2. Theoretically to determine the exact position of an object we need: A reference coordinate system A map, if the interrelation of the object is considered Since the map has its own coordinate system, this one and the real coordinate system needs to be correlated to each other. This procedure is the registration.
In practice, there are frame based and frameless techniques. In the former case the stereotactic frame is the base of a 3D coordinate system. In case of frameless navigation the part of the body to be treated is immobilized in some way, and its position is compared to a reference system e. In both cases the CT, or MR picture data serve as reference maps for the navigation.
The history of stereotaxy and surgical navigation The pioneers of intracranial neurosurgeons at the end of the 19th and the beginning of 20th centuries relied purely on their anatomical knowledge and clinical observations regarding the place, size and characteristics of certain brain structures and pathologies, since intracranial imaging was not yet available.
For the first time, a Russian professor, Zernov Dmitri Zernov,an anatomist in Moscow created and used a prostate volume normal radiopaedia instrument encephalometer for anatomical studies and neurosurgical interventions. With the help of this instrument he was able to determine the position of brain structures in polar coordinates.
He nem sérti a prosztatitist the encephalometer to determine the position of the central sulcus, and revealing this place, he discovered a cerebral abscess.
Figure 7. Figure 1. Kandel: Functional and stereotactic neurosurgery, Although clearly from above, he was the one who developed stereotaxy, his work Prostate koncepció not known by the rest of the world, thus usually Sir Victor Horsley and his colleague Robert H.
Clarke are considered to build a stereotactic instrument first time in the world in for electrophysiological experiments in animals. Unfortunately they could not define the exact position of subcortical structures compared to bones in a humans, that is why this method did not spread for a long time.
Prostate volume normal radiopaedia the next years and decades, procedures utilizing this technique developed rapidly but the transfer of image information to the given patient depended purely on the anatomical knowledge and power of spatial conception of the surgeon.
Home Epipharynx tumor The localisation of this tumor in the epipharynx is a rarity and unknown in the literature. Hátránya, hogy intubációkor zavarhatja a vizualizációt. A gastralis táplálás javasolt, ha a gyomorürülés biztosított, és nincs aspirációs veszély. The hypopharynx or laryngopharynx forms the most inferior portion of the pharynx, being the continuation of the oropharynx superiorly and both the larynx and esophagus inferiorly.
The goal was to guide an instrument to a formerly defined point of the brain. Frame based stereotaxy After all these, the stereotactic frames firmly attached to the scull spread widely.
Initially, they have been used to guide prostate volume normal radiopaedia lesions in order to relive the symptoms of movement disorders, chronic pain, and epilepsy; and later to prostate volume normal radiopaedia cysts, abscesses, to implant radio-isotopes, to make biopsies or for radiosurgery. The advantage of a stereotactic frame is its precise and reliable attachment and coordinate system. Its disadvantages in general neurosurgery : the frame is applied on the day of the surgery scala posterior structures can not be reached easily the frame may impede the surgeon the localization is feasible for single or a small number of targets it is hard to change target during surgery 2.
Frameless stereotaxy Recently called neuronavigation As a consequence of the exploding evolution of computation and imaging techniques DSA, CT, MR the possibility and quality of surgical planning Ofloxin és prostatitis improved.
On the other hand, the rich information collected prior to surgery should be transferred in some way to the operation field in order to use it during surgery.
This task, requiring serious experience and orientation skills, was solved purely in mind of a traditional neurosurgeon. David Roberts developed a navigation system based on ultrasonography in This did not spread wide in clinical practice. InEiju Watanabe constructed a localization system that consisted of many joints and arms of given length. This instrument went into standardized production. At the early nineties, two further navigation systems emerged: the electromagnetic, and the optical.
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The advantage of the electromagnetic system was that there was no need for direct optical contact between the machine and the surgical field, on the other hand the initial imprecision of 2 millimeters increased in vicinity of cipro for prostatitis reviews, which was its disadvantage.
Thus optical systems spread wide their functioning is similar to GPS. Active and passive types exist: In case of an active system, infrared beams emitted by instruments connected to the base system are detected by infrared cameras. Its disadvantage is that the wires are sometimes disturbing during the surgery.
Its advantages are that they can be used well under sterile drapes and under wet conditions.
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The instruments of a passive system have small reflective fiducials that are detected by two cameras, ejecting infrared light. The advantage of the system is the lack of wires, the disadvantage is that it is more sensitive to humidity and the fiducials need to be changed regularly, because they worn out during sterilization.
The change of the pellets is pretty expensive cost ineffectiveness.
In case of neuronavigation, however, initially there is no relationship between the two coordinate systems. The procedure that establishes this relationship is called registration. Types of registration: Paired point prostate volume normal radiopaedia we need at least 3 points which are not lying in line [linearly independent] At the beginning, prostate volume normal radiopaedia based registration was used.
We grant much more points in the space, which define the surface. Neurosurgeons navigate the tip of their instruments or the focus of their microscope in order to orient intracranially. Oncologists try to direct the radiation beam towards the intracranial target and since the radiation head cannot move freely except CyberKnife ; the patient is positioned to the instrument to the center of the radiation instrument.
Radiosurgery, RS Single session, focused irradiation to a stereotactically localized target. The reason of the denomination: The treatment results in long-term similar effects as the target was excised by a scalpel, and in most cases prostate volume normal radiopaedia a small scar remains in place of the target.
The treatment for one target can be done in 20 minutes, and its effect is definitive and irreversible, similar to a surgical intervention. Fractionated stereotactic radiation therapy fSRT Multiple sessions, focused irradiation to a stereotactically localized target. Biological principles of a traditional fractionated radiation therapy The effect of ionizing radiation is due to prostate volume normal radiopaedia energy egress.
Многие поколения мечтали об этом веке, но достигли его лишь. Так и существовали они в своем неменяющемся городе, ходили по его улицам, и улицы эти каким-то чудесным образом не знали перемен, хотя в небытие уже ушло более миллиарда лет. Им потребовалось несколько часов, чтобы с боем вырваться из Пещеры Белых Червей.
Major portion of the absorbed energy is translated to the ionization of the atoms in the given volume. The shorter the absorption route Linear Energy Transfer, LET the more ions are produced on the way of the particle, viz. In case of radiation qualities with very high ionizing density neutron, accelerated ions chemical reactions can directly reach the bigger molecules proteins, RNA, DNAwhile electron or photon irradiation acts indirectly by formation of free oxygen radicals.
These make fast reactions with macromolecules, thus membrane or enzyme Gyertyák a prosztatitis ár kezelésére, signal transduction, protein- and DNA-synthesis can be damaged, and apoptosis can be induced. Chemical reactions caused by the radiation induce protective mechanisms, the inflammatory cascade is activated, and repair mechanisms come into effect.
In cellular level either transient, reparable disturbance develops, or prostate volume normal radiopaedia cell becomes unable to divide, or dies. The biological effect of radiation A prosztatitis okai egy emberben on the proportion of cells capable for proliferation in cell cycle; cells are the most sensitive in G2 and M phaseon the number of cells, on the repair capacity and oxygenation of them, on their sensitivity determined by their molecular composition, and on the temporal distribution of the prostate volume normal radiopaedia dose that is: fractionation.
The total dose of the irradiation treatment is fractionated divided into several smaller doses and given off in multiple sessions because of the following reasons: Fractionation allows normal cells to recover between fractions, while the regeneration ability of cancer cells is less potent Fractionation makes it possible for cancer cells being in an insensitive phase of the cell cycle during one session, to get into a sensitive phase for the next fraction Cancer cells being in a hypoxic environment during one session thus being less radiosensitive may reoxygenate by the time the next session starts, and become more radiosensitive.
Radiation necrosis was a dreadful side effect of radiotherapy those days. It affected the target volume and neighboring healthy tissues, and it was very difficult to stop. It often caused severe brain swelling in case of intracranial treatments or fistulae, peritonitis, ileus at abdominal irradiation resulting life-threatening conditions.
With the technical mainly computational development, it become possible to direct the radiation beams coming from different directions with a tenth of a millimeter exactitude, and to safely administer huge doses of irradiation, enough to cause irreversible tissue damage in one session.
Hence its name is radiosurgery. It should be noted here, that the description above is valid mainly for the treatment of malignant intracranial tumours.
The technique using smaller doses can be used for the treatment of benign lesions as well. In these cases our goal is not the total destruction of the target volume but to prevent it from growing vestibular schwannomaor to minimize its blood supply arterio-venous malformations.
In these cases, irradiation induces endothelial division and causes occlusion of the vessels within months. Principles of fractionated stereotactic radiotherapy fSRT By definition, compared to radiosurgery, the difference is that the radiotherapy applied with the precision of stereotaxy is given in multiple sessions, using the advantageous features of both traditional radiotherapy and radiosurgery with high spatial selectivity: it is prostate volume normal radiopaedia precisely applied radiotherapy that utilizes the radiosensitivity difference between normal and tumour cells.
In CNS oncology it is used mainly for the treatment of tumours near eloquent brain areas where the required fall of dose in vicinity of the target cannot be reached, thus chances of injury of the risk organ in case of a single session radiosurgery would be prostate volume normal radiopaedia high.
Requirements of stereotactic radiation techniques 6. Immobilization of the target volume In order to safely deliver the required dose resulting in radionecrosis, the target has to be rigidly and reproducibly immobilized.
The goal is the possibility to bring the target volume into the same position for the treatment as it was during the imaging serving the basis of treatment planning. This requirement can be fulfilled easily for intracranial targets, since the brain can be fixed without major shift through the scull. That is why radiosurgery and stereotactic radiotherapy remained until the last years a therapeutic option for only intracranial targets.
Rapid technical evolution of the last decade has made stereotactic irradiations possible in all parts of the body. In reality, the exact position of the target volumes is given related to this frame as reference.
The screws are attached firmly to the outer cortical layer of the scull under local anaesthesia. Beyond the anesthetic injection the attachment of the frame causes a transitional feeling of wring for minutes.
Mask For the fractionated stereotactic radiotherapy the scull and the target volume through it would be unfeasible to be attached in an invasive way since it would be necessary to wear it for the total course of even 6 weeks, or — theoretically — it would have to be attached before every treatment session, but in this case a new CT and new plan would also be required.
To overcome this problem, non-invasive immobilization systems emerged.
Nowadays thermoplastic mask systems emerged and are complemented with other instruments e. Positioning, guidance and image guided radiotherapy IGRT Accurate irradiation of the target volume made marked reduction of radiation load of healthy tissue, and precise implementation necessary.
Although using a well-prepared mask the head of a well-collaborating patient can be fixed with accuracy similar to the frame session by session, millimeter preciseness required the verification of the position of the target volume. If mismatch is observed the patient is repositioned.
Next to the megavolt system, the most modern LINACs are equipped with a kilovolt system two pairs of X-ray tube and detector as well. DRR calculated from the plan and actual X-ray or prostate volume normal radiopaedia beam CT images are compared, and the mismatch is calculated by an image fusion algorithm in 6 degrees of freedom shift and tilt in three directionsand corrected by a robotic couch.
This is achieved by vacuum mattresses, or by masks molded on the given part of the body. On the other hand, we should take into account that the shape and position of different organs inside the body change with their functioning movement of bowels, change of the shape of lung during breathing, etc.
The impreciseness derived from the above prostate volume normal radiopaedia organ movements could be eliminated using the following techniques: For targets lying near by bones, and whose positions and shapes do not change in relation to the bone, an X-ray and DRR pair can be used for positioning like in case of intracranial targets.
For target volumes where organ movement and shape alteration is negligible positioning of the target is done by mismatch minimization of Cone beam and planning CTs.
A simple but invasive possibility for the stereotactic positioning of certain retroperitoneal organs prostate volume normal radiopaedia the use of implanted markers. Golden seeds are implanted prior the planning CT. The point is, that respiratory curve data are stored with the images, and the plan is created to a given phase of the respiratory cycle. During treatment, beams are on only during the given phase.