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Contemporary Proton Therapy: Challenges and Potentials
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dayananda shamurailatpam
Oct 10, 2020
How main proton beam is delivered to different treatment rooms for treating different patients simultaneously? Response : Only One proton field can be deliver at a time. If beam is requested from two treatment room simultaneously, the main controller will put the request in que. Priority in Que depend on user request (High priority/Normal priority). For the same request e.g. normal priority, main controller will prioritize the request based on the request time. Also, what are the interlocks or systems available to prevent wrong dose delivery in case of multiple treatment simultaneously? Response: When the beam is allocated to one treatment room, other room can't use the beam till the delivery is complete or release the beam by the user from the other room. Are the patients being protected from Neutron dose during treatment with proton beam. If so, how the same is done? Or it is allowed for thesake of the benefit to the patient? Response: The contribution of neutron dose to patient is negligible in pencil beam scanning technique. This is also another advantages of scanning technique over scattering technique. Therefore, no special attempt has been made to protect patient from the neutron dose. what are the main drawback of proton therapy beside cost? Response: I wouldn't call as drawbacks. But obviously there are challenges which can be mitigated. They are Lack of evidences of clinical benefit to many clinical sites, Lateral Penumbra is slightly wider. Charge particles are more vulnerable to uncertainty. Treating moving tumor is challenging specially with IMPT due to interplay effect. what is the life expectancy of CSI patients and when should one expect the incidence of secondary malinancy? Response : Life expectancy of pediatric CNS has increased significantly over the last few decades due to the improvement in surgical procedure, better understanding of tumor biology, better chemotherapeutic drug and of course refinement of radiotherapy techniques. The 5-year survival rate has been reported to >80% for average-risk and >50% for high-risk medulloblastoma. Plz refer Packer RJ J Clin Oncol 2006;24:4202–8, Gajjar A J Clin Oncol 2004;15:984–93.Bree R. EatonInt J Radiation Oncol Biol Phys, Vol. 94, No. 1, pp. 133e138, 2016. The onset of second cancer ? That is bit difficult question. Few literatures set 5 years in their definition of the onset of second cancer. However, the graph which i share during my presentation showed around 0.01% of their patient treated with proton therapy developed second cancer in 2-3 yrs after treatment. The rate of incidence increases which increases with the the duration of survival after treatment. I would suggest to refer the paper by Mu et al 2015 Christine S Chung et al 2013. In India, what is the future of Proton therapy treatments for the patients belongs to Middle Income Group (MIG), and Low Income Group (LIG) ? Response: If the patient is qualified for proton therapy, there are many health schemes provided by Govt., Insurance, Trust, Crowd Funding etc. to help MIG and LIG. What is your opinion on it?what is the dose limit for neutron in radiation survey around proton therapy facility ? Response : There is no separate dose limit for neutron. However, when the measured total ambient dose is converted in to the effective dose equivalent, it should be well below the annual dose limit of worker and public set by the competent authority of the country. what is the shield thickness? has anyone measured the neutron spectra inside and outside vault? Response: Shielding thickness varies from 1.2 m to 4.6 m. No we have not attempted to measure neutron spectra. if yes result olIs island kind of distribution possible in proton? Ex spinal cord sparing, hippo cambal sparing. Response: Yes. We have treated few patients with hippocampus sparing technique. What about the phantom measurements for protons? Response: Question is not clear to me Is it right to use 2mm dta criteria for gamma analysis? Response : Although many centers across the world including ours used gamma of 3%@3mm, for the shake of investigating the impact of spot positioning error in the accuracy of proton treatment delivery we have used 2%@2mm and 1%@1mm. Moreover, recent recommendation support 2%@2mm what are the indications for proton therapy in india? Response: Currently main sites are Pediatric, CNS, Head&Neck, Bone & Soft Tissue, Chordomas and Condrosarcomas, More are under investigation and spectrum of eligible site is expanding.
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dayananda shamurailatpam
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