ANA Discussion Forum
Treatment Options => Radiation / Radiosurgery => Topic started by: luckyone on March 20, 2012, 11:33:42 pm
-
Just wondering if anyone out there has thought about this. I am thinking of GK vs CK, and with CK you are being exposed to much higher doses of radiation than an x-ray just for the CT scan alone... then you add the actual fractional treatment. Multiply that 6 times per minute, times a treatment of 30 mins times 3 days. That is a lot of radiation. Does that make GK a better option?
-
Cyberknife only requires one CT Scan which is for the treatment planning only, it doesn't do CT scanning during treatment.
There are two low dose x-ray tubes which are used to position the patient, and there are also infrared detectors that also detect movement. The number of low dose xrays that you receive is dependant on the person programming the machine, but I have seen reference to a maximum of one xray per shot, and 1 per minute as being typical. So 6 per minute seems high to me. I am sure your treating doctor can put more light on this.
The low dose positioning X-Rays of course do pose a small risk, however I believe the amount of additional radiation you will receive as a result of the x-ray positioning, is quite small in comparison to the amount of extraneous radiation that you will receive as a result of the treatment.
Speak with the doc's, I believe the additional radiation from the positioning xrays poses only a small increase in the overall dosage to good tissue.
-
Thanks PaulW, I appreciate your reply. I would love the opportunity to get a consultation but my insurance UnitedHealthcare is giving me the run-around for trying to go outside my HMO plan. I am currently going back and forth with Dr Chang from Stanford to get his take on why I should do CK versus GK.
-
From what I have been told, you get much more radiation from GK. I was told that GK is done in one dose so the radiation must be a much higher dose. With CK the dose can be cut back and as with me they did 5 sessions instead of 3.
TJ
-
CT scan is also needed for treatment planning for GK. So you wouldn't avoid the CT one way or another. GK uses gamma rays from a cobalt source. CK uses X-rays. GK delivers a single dose (average doses nowadays are 12-13 Gy), whereas CK uses fractionated treatment (usually about 18 Gy if I remember well from what I have read here), delivered over 3 or 5 days. The total dose seems higher therefore, but the dose delivered during every session is lower, that's why CK is considered to be slightly more advantageous in terms of hearing preservation. I think overall these are considered biologically equivalent.
CK is considered to have an advantage by delivering a more uniform radiation dose to the tumor. Whereas GK delivers twice as much at the centre than at the edge. Other than that the two modes of treatment are considered very similar in terms of their effectiveness. Depending on who you consult with they will tend to promote one vs. the other. So you need to ask around and get multiple opinions.
Marianna
-
Depending on the size shape and location of the tumour I believe that either machine can be proved to be slightly worse or slightly better than each other. Cyberknife can do multiple fractions and is frameless which is a differentiator and even the effectiveness of that for AN's is debateable.
The best GK centres are getting very similar results to the best CK centres.
One thing that is known, is that a reduction in radiation to the cochlear helps preserve hearing.
Better machines, better software, better MRI's, lower radiation doses, the treating of smaller AN's..
Its all helping to reduce the radiation dose to the cochlear.
-
Hi TJ;
Of course the radiation received from either GK or CK is "focused beam", so has little to no impact on the rest of the body.
GK is normally one setting and delivers 12 - 13 gys. CK may be more Tx's, but the individual dosages would add to about the same as the 13 gy.
One thing about CK is positioning the equipment requires a CT. A CT is equivalent to about 400 chest x-rays. Also with CK is the small amount of X-ray emitted by the positioning system for the linear accelerator. The CT and x-rays used for aligning and constant positioning would be accumulative, while the focused beam of the actual tumor delivery has no build up or half life.
FSR actually has the highest overall focused beam dosage, but is delivered in hypofractions. They are not accumulative.
I think, in general, AN Tx providers are drifting away from FSR as the physics of the other 2 systems are tissue sparing by nature.
From what I have been told, you get much more radiation from GK. I was told that GK is done in one dose so the radiation must be a much higher dose. With CK the dose can be cut back and as with me they did 5 sessions instead of 3.
TJ
-
GK and CK are both good treatment options.
Jan
-
I had GK in 2010 and had an MRI for planning, Never had a CT.
-
I remember having a CT for CK planning. I also had a CT after surgery.