1 Radiation Therapy Flashcards
Sulfhydryl components
scavenge free radicals
Administering a dose in fractions with adequate time between applications allows
the repair of sublethal damage
and the repopulation of tissue cells.
Tumors often have poorly developed
blood vessels intermittent blood flow
Dose range for solid tumor cure
60 to 80 Gy,
Preventive (adjuvant) doses
45–60 Gy in 1.8–2 Gy fractions (for breast, head, and neck cancers.)
In North America, Australia, and Europe, the typical fractionation schedule
for adults is 1.8 to 2 Gy per day, five days a week, For children, a typical fraction size may be 1.5 to 1.8 Gy per day
External beam radiation therapy fails
to eradicate the primary tumor in 1 out of 3 patients
E of protons used in proton therapy
190MeV with range 25cm (Bragg-Peak)
the most common form of radiotherapy
External beam radiotherapy or teletherapy
Kilovoltage (“superficial”) X-rays
treating skin cancer and
superficial structures. 50 to 200 kV
Megavoltage (“deep”) X-rays
treat deep-seated tumors
(e.g. bladder, bowel, prostate, lung, or brain). 1 to 25 MV. Most common in therapy and produced in linac and Co units (Co-60 teletherapy machine)
diagnostic X-rays
20 to 150 kV
orthovoltage X-rays
200 to 500 kV
supervoltage X-rays
500 to 1000 kV
Intensity Modulated Radiation Therapy
intensity modulation is achieved by moving the leaves in the MLC(Multi-Leaf Collimator) during the course of treatment, thereby delivering a radiation field with a non-uniform (i.e. modulated) intensity in beamlets
3D Conformal Radiation Therapy
utilizes sophisticated computer technologies such as CT scans and MRI images to view tumors in three dimensions (3D)-width, height and depth. With superior tumor imaging, patient treatment plans can be created with greater precision.
Neutron Capture Therapy
the patient is injected with a tumor localizing drug containing a non-radioactive isotope that has a high cross section for slow neutron capture.;patient is radiated with epithermal neutrons, which after losing energy as they penetrate tissue, are
absorbed by the injected isotope, which then emits high-energy charged particles that deposit their kinetic energy locally,
thereby resulting in the killing of cancer cells.
Isotopes Used in Neutron Capture Therapy
boron-10 only - BNCT
The BNCT Reaction
10B+n=7Li+4He+Gamma (0.477 MEv)
B agents used clinically
Sodium borocaptate (BSH); Boronophenylalanine (BPA)
BNCT Dose Components
1H(n,gamma)2H, 14N(n,p)14C; fast neutrons from recoil. D=CFD(boron)+RBE(N)D(N)+RBE(R)D(R)+RBE(gamma)D(gamma)
Brachytherapy or Endocurietherapy
Implanting radioactive sources into or close to tumor 50-70 Gy in 5-9
days is common
common for temporary implants in Interstitial therapy
Iridium-192
iodine- 125 in Interstitial therapy
common for permanent implants total prescribed dose of 160 Gy, with 80 Gy delivered in the first 60 days.most effective in slow-growing tumors
