Treatment Slides

COMPARISON WITH OTHER TECHNIQUES-

Gamma Knife compared with other Linac based treatments

The origin of Stereotactic Radiosurgery clearly began with Prof Lars Leksell's description of the technique in both in technical terms and in terms of practical applications in 1951 based on his experiments with ortho-voltage x-ray tube mounted on stereotactic frame arc and later in Uppsala University Cyclotron Unit. These experiments proved the possible feasibility of stereotactic radiosurgery but also that it is not a simple and efficient process to use these cyclotrons or charged particles and Liner accelerators. He developed first Gamma knife prototype in 1967 and started early treatment. Later Gamma Knife proved itself as Gold Standard for Stereotactic Radiosurgery.

As people continue to search for alternative technologies later the Linac, based radiosurgery was developed at various centers by different process. In 1982, Betti and Derechinsky in Paris and Buenos Aires and Colombo and colleagues in Vicenza in Italy demonstrated possible clinical use of linear accelerators for stereotactic radiosurgery by modifying the medical Linac already in use for radiotherapy. Centers started upgrading there linacs by attachments bought from various sources and started for stereotactic radiosurgery in a limited way. Winston and Lutz in Boston began to adopt there linear accelerator to a widely available stereotactic guiding device in 1987. Other similar therapies are also developed using fractionation, and dynamic beam shaping therapy or Intensity Modulation Radiotherapy [IMRT].

Question of superiority of techniques over each other is interpreted by user and sellers in there own way. What should be of concern to patient is what are his chances to get relief and cure form his prevailing disease without or with minimal complications.

There are three techniques available for stereotactic radiosurgery and similar treatments. Heavy Charges particles, Gamma Knife and Liner accelerators, which can also be used, for fractionated stereotactic radiotherapy and Intensity modulated radiotherapy. The centers using heavy charges particle are very few and can be counted on fingertips. Since Gamma Knife Prototype installation, it in 1967 its efficacy has been proved with long tract records of treated patients and similar efficacy in centers around the world. The linear accelerator based radiosurgery starting in 1982 has much smaller tract record and there is poor standardization as these centers are upgraded by different packages by different agencies. So there is large variation in techniques for dose delivery, planning pattern and radiation dose used, and so the results to wary.

Dedicated Linacs have been developed for stereotactic radiosurgery. These centers are very few as most linac centres are established in oncology departments not neurosurgery department and dedicated linac is not good enough for radiotherapy. These can treat small tumors and those, which are not critically located and cannot do functional surgery. As basic technique has limitation that with linac it is difficult to plan more that 4-5 isocentres the total internal dose of the tumor in less and conformity is not as sharp when compared to Gamma knife planning where there is no limit to number of isocentres. Thus, the treatment results are not as good as Gamma knife

Non-dedicated linear accelerators are mostly used for fractionated stereotactic radiotherapy where large and fewer fractions are given as compared to conformal radiotherapy. The can treat large lesions and malignant lesions. Radiobiologically we understand that fractionation is not very good for benign lesions due to there low a/ß ratio. In addition, malignant tumors do not do well with hypo-fractionation. Over all, there are a many controversies in such usage of linac. There results are also much poorer than gamma knife.

Newer Dynamic beam shaping technique or IMRS using micro multileaf collimator has same disadvantage as of any other linac, of delivery of low internal dose, which make the result poor. Although it has been claimed that the planning is as conformal as Gamma knife but as the radiation delivery is low it do not match in results as compared to gamma Knife. In addition, most centers even with a micro MLC do not do a single session radiosurgery but radiotherapy with multiple fractions. Only over all advantage is to reduce dose to peripheral structures, which was always present with Gamma Knife.

To conclude we can say although many new technologies are coming which will try to do radiosurgery like Gamma knife, it remains the gold standard and most successful radiosurgical technique so far.

Machines are made for different things. A Volkswagen cannot do what a Mack truck can do -- each is designed for something different. This is true of all radiation machines. First, ask, "What is the machine designed for?" Then ask, "Will I be treated by a neurosurgeon?" The answers will guide you.

Things to think about: Is newer always better? Whenever there is a product on the market that is well known and accepted, many other manufacturers step in to capitalize on this market area. It is the same with treatment technology. When a new machine is developed, it takes at least a decade to have enough machines in treatment and enough research to see if the new treating machine can do what the manufacturer states. Only time will tell.