Devita, Hellman, and Rosenberg's Cancer

LWBK1006-07 LWW-Govindan-Review November 22, 2011 13:54

88 DeVita, Hellman, and Rosenberg’s CANCER: Principles and Practice of Oncology Review

Question 7.13. Which of the following statements best describes the tissue effects from

radiation?

A. Early or acute effects typically occur within months after irradiation.

B. Large a/b ratio has a small “shoulder” in the low-dose portion.

C. The frequencies of late effects depend strongly on radiation fraction

size.

D. Typical human tumors and early-responding normal tissues have a

small a/b ratio.

Question 7.14. Which of the following statements is an INCORRECT description of the

interaction of x-rays with biologic material?

A. In modern treatment with greater than 4 MeV photons, photoelectric

effect dominates the interaction.

B. In photoelectric effect, an incoming x-ray transfers all its energy to

an inner orbit electron, which is ejected from the atom. A photon is

produced as an outer shell electron fills the vacant hole.

C. In Compton scattering, energy from the x-ray is both absorbed and

scattered. The photon emerges with reduced energy and a change in

direction.

D. In pair production, an electron and a positron are produced.

Question 7.15. Which of the following statements describes the depth dose characteristics

of radiation?

A. Higher-energy photons deposit more dose to the skin surface.

B. For a given energy, electrons generally penetrate deeper in tissue com-

pared with photons.

C. Electron beams deposit less dose to the skin surface as the incident

electron energy increases.

D. Depth of maximum dose increases as the energy of the incident beam

increases.

Question 7.16. Which of the following statements is NOT true regarding brachytherapy?

A. Isotopes with properties of long half-lives and high energy are typi-

cally used for permanent implants.

B. Brachytherapy refers to placement of radioactive sources next to or

inside the tumor, or within body or surgical cavities.

C. High doses can be delivered within a few centimeters of the source.

D. A potential advantage of brachytherapy is its ability to produce con-

formal treatments with low normal tissue dose.

Question 7.17. Which of the following can be a subacute toxcitiy from radiation therapy?

A. Pneumonitis

B. Myelitis.

C. Brain necrosis.

D. B and C.