Re: Novalis Shaped Beam Surgery
Hi Tall Allen,
Misleading or simply wrong information can be found in many places. Including major print media and the Internet.
Presently only the CyberKnife can deliver beams of radiation from a choice of nodes of 360% reference to the target. Why is this important? This allows beams to be selected to miss critical structures. All other machines deliver beams from a 2D plane. Physics limits the shape of the prescribed dose volume. This is a major advantage of the CyberKnife.
Respiration timing is "not" used in the treatment of prostate cancer. Prostrate movement during treatment is the result of solids and gases in the colon and liquids in the bladder. Respiration timing is used in the treatment of lung cancer and breast cancer with many new radiation systems. The CyberKnife uses respiration timing if, fiducials (targets) are not used to target the tumor.
The CyberKnife is the only radiotherapy treatment that tracks the prostate, with sub mm accuracy, during treatment. When the prostate moves the beam is moved to stay on target.
Only the CyberKnife tracks and automatically adjust the beams to keep on target. This allows the dose volume margin to be reduced, which reduces high dose to the colon and bladder.
Ionizing Radiation energy to cancer cells is measured in fraction size, number of fractions, and total dose. The biologic equivalent of dose per session is not linear. The size of the linear accelerator is not a measure of treatment dose. Hypo fractionation is the term used for a therapy that delivers high dose per session. Prostate cancer is more sensitive to increased dose per session/fraction than other cancers. This is a good characteristic that has resulted in better cure rates with increased dose per session/fraction. Hypo fractionation (HDR Brachytherapy and CyberKnife) has a very high cure rate relative to lower dose per session radiation. IMRT total dose has increased from 60 Gy to 80-86.4 Gy delivered in 1.8 Gy per session/fraction. Today the typical IMRT plan is 40-45 days of therapy. The CyberKnife has two plans four sessions of 9.5 Gy or five sessions of 7.25 Gy. The total does of hypo fractionation is less than 1/2 of the total dose from IMRT. The dose to normal tissue is lower with hypo fractionation plans and toxicity less.
Presently only the CyberKnife can deliver a hypo fractionated dose with sub mm accuracy from 1000's of nodes at 360% to the target. Other IMRT machines, by any name, can deliver a hypo fractionated but do not because of toxicity to normal tissue.
Suggest all men understand the science of radiotherapy. This is the only way to know if your are being mislead.
Last edited by viperfred; 08-31-2010 at 02:44 PM.